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Six- and Three-Hourly Meteorological Observations from 223 Former U.S.S.R. Stations (NDP-048)

DOI: 10.3334/CDIAC/cli.ndp048

image PDF  image Data  image Previous Data (data through 1990, published in 1998)

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Investigators

Contributed by
V. N. Razuvaev, E. B. Apasova, R. A. Martuganov
All-Russian Research Institute
of Hydrometeorological Information-World Data Centre
Obninsk, Russia

Prepared by
D. P. Kaiser and G. P. Marino
(contact: kaiserdp@ornl.gov)
Carbon Dioxide Information Analysis Center
Oak Ridge National Laboratory
Oak Ridge, Tennessee

Date Published: November 2007

Prepared for the
Climate Change Research Division
Office of Biological and Environmental Research
U.S. Department of Energy
Budget Activity Number KP 12 05 06 0

Prepared by the
Carbon Dioxide Information Analysis Center
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37831-6290
managed by
University of Tennessee-Battelle, LLC
for the
U.S. DEPARTMENT OF ENERGY
under contract DE-AC05-00OR22725

Contents

List of Figures
List of Tables
Abstract
1. Name of the Numeric Data Package
2. Principal Investigators
3. Keywords
4. Background Information
5. Description of the Database
6. CDIAC Quality Assurance Checks
7. File Descriptions
    Documentation File for NDP-048 (ndp048.txt)
    FORTRAN and SAS Data Retrieval Programs (.for and .sas files)
    Station Inventory File (station.inv)
    Data Gaps File (gaps.dat)
    Station Timezone File (timezone.dat)
    Station History File (station.his)
    Station Data Files
8. References

List of Figures

1. Locations of stations in the 223-station former U.S.S.R. network

List of Tables

1. Inventory of stations in the 223-station former U.S.S.R. network
2. Gaps in the periods of record of the 223 former U.S.S.R. stations

Abstract

Razuvaev, V. N., E. G. Apasova, and R. A. Martuganov. 2007. Six- and Three-hourly Meteorological Observations from 223 Former U.S.S.R. Stations. ORNL/CDIAC-108, NDP-048. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee. doi: 10.3334/CDIAC/cli.ndp048>

This database contains 6- and 3-hourly meteorological observations from a 223-station network of the former Soviet Union. These data have been made available through cooperation between the two principal climate data centers of the United States and Russia: the National Climatic Data Center (NCDC), in Asheville, North Carolina, and the All-Russian Research Institute of Hydrometeorological Information-World Data Centre (RIHMI-WDC) in Obninsk, Russia. The first version of this database extended through the mid-1980s (ending year dependent upon station) and was made available in 1995 by the Carbon Dioxide Information Analysis Center (CDIAC) as NDP-048. A second version of the database extended the data records through 1990. This third, and current version of the database includes data through 2000 for over half of the stations (mainly for Russia), whereas the remainder of the stations have records extending through various years of the 1990s. Because of the break up of the Soviet Union in 1991, and since RIHMI-WDC is a Russian institution, only Russain stations are generally available through 2000. The non-Russian station records in this database typically extend through 1991. Station records consist of 6- and 3-hourly observations of some 24 meteorological variables including temperature, past and present weather type, precipitation amount, cloud amount and type, sea level pressure, relative humidity, and wind direction and speed. The 6-hourly observations extend from 1936 through 1965; the 3-hourly observations extend from 1966 through 2000 (or through the latest year available). These data have undergone extensive quality assurance checks by RIHMI-WDC, NCDC, and CDIAC. The database represents a wealth of meteorological information for a large and climatologically important portion of the earth's land area, and should prove extremely useful for a wide variety of regional climate change studies.

1. Name of the Numeric Data Package

Six- and Three-hourly Meteorological Observations from 223 Former U.S.S.R. Stations

2. Principal Investigators

V. N. Razuvaev, E. B. Apasova, R. A. Martuganov
All-Russian Research Institute
of Hydrometeorological Information-World Data Centre
Obninsk, Russia

3. Keywords

U.S.S.R., former Soviet Union, Russia, hourly data, air temperature, dew point temperature, relative humidity, water vapor pressure, sea level pressure, visibility, cloud amount, cloud height, wind direction, wind speed, precipitation amount, soil temperature, weather type, atmospheric phenomena

4. Background Information

In recent years, a great deal of meteorological data have been exchanged between the two principal climate data centers of the United States and Russia: the National Climatic Data Center (NCDC), in Asheville, North Carolina, and the All-Russian Research Institute of Hydrometeorological Information World Data Centre (RIHMI-WDC) in Obninsk. This was accomplished via Working Group VIII (Influence of Environmental Changes on Climate) of the bilateral initiative known as the Agreement on Protection of the Environment, established on May 23, 1972, by the United States and the U.S.S.R. Working Group VIII established the Climate Data Exchange and Management Agreement Project, the purpose of which is to promote the sharing of climatological data between NCDC and RIHMI-WDC. Surface meteorological and climatological data for the former U.S.S.R. that have been received by NCDC from RIHMI-WDC to date include:

  • monthly mean temperature data from 243 stations (1891-1988),
  • daily temperature and precipitation data from 223 stations (1881-1989),
  • 6-hourly observations from the above 223 stations (1936-1965), and
  • 3-hourly observations from the above 223 stations (1966-2000).

The Carbon Dioxide Information Analysis Center (CDIAC), through a cooperative agreement with NCDC , has packaged and made available to the public the four databases referred to above. The monthly mean temperature data from 243 stations (1891-1988) are included in the Global Historical Climatology Network database (Vose et al. 1992); the daily temperature and precipitation data from 223 stations (1881-1989) are documented in Razuvaev et al. (1993). The purpose of this numeric data package (NDP) is to update (for many stations, through 2000) the 6- and 3-hourly observations from the 223-station network of the former Soviet Union (FSU). These hourly data represent a wealth of meteorological information for a large and climatologically important part of the earth's land area and are described in the following sections.

5. Description of the Database

The data records contained in this NDP include 25 types of meteorological observations from each of the 223 FSU stations. These observations appear in each record of the database in the order given below.

  • Relative humidity
  • Water vapor pressure
  • Sea level pressure
  • Humidity deficit
  • Pressure tendency characteristic
  • Pressure tendency value
  • Horizontal visibility
  • Height of cloud base
  • Dew point temperature
  • Ground state (description of the state of the ground surface)
  • Total cloud amount
  • Low-cloud amount
  • Wind direction
  • Wind speed
  • Precipitation amount
  • Air pressure at station level
  • Near-surface air temperature
  • Soil surface temperature
  • Past weather
  • Present weather
  • Atmospheric phenomena
  • High-level cloud type
  • Mid-level cloud type
  • Low-level cloud type
  • Characteristic of wind irregularity (only present in 6-hourly observations)

Detailed descriptions of all variables are presented in the following sections of this document. Observations of the last variable in the above list--characteristic of wind irregularity--are only present in the 6-hourly data, which run through 1965. Observations of all other variables are, for the most part, present throughout each station's record. Each record of the database contains entries for all variables at a specific observation hour. Over the period 1936-65, observations were carried out at 0100, 0700, 1300, and 1900 Local Mean Time (LMT). From 1966 through 2000, observations were made at 0000, 0300, 0600, 0900, 1200, 1500, 1800, and 2100 Moscow Legal Time (MLT). In the version of the database presented here, times of observation have been converted to Greenwich Mean Time (GMT) (3 h earlier than MLT); the GMTs of observations vary with station as a function of timezone (longitude). In converting LMT to GMT each station had to be assigned a specific timezone. For a small number of stations there was some uncertainty involved in this due to changes over the years in timezone designation; however, the potential error is no more than 1 h in any case.

Not all stations have data for 1936-2000; some station records begin after 1936, and some have gaps ranging from one month to several years. An inventory of the 223-station network, including each station's name, World Meteorological Organization (WMO) station number, latitude, longitude, elevation above sea level, and beginning and ending years of record, is given in Table 1. Stations with gaps in their period of record are identified in Table 1 by asterisks, with these gaps presented in detail in Table 2. A map showing the locations of all 223 stations is presented in Figure 1. The number plotted next to each station in Figure 1 is the station sequence number given in the leftmost column in Table 1.

6. CDIAC Quality Assurance Checks

An important part of the data packaging process at CDIAC involves the quality assurance (QA) of data before distribution. Data received by CDIAC are rarely in a condition that would permit immediate distribution, regardless of their source. To guarantee data of the highest possible quality, CDIAC performs extensive QA checks, examining the data for completeness, reasonableness, and accuracy.

Some basic data checks had been performed by RIHMI-WDC and NCDC prior to the arrival of the data at CDIAC. Extensive documentation pertaining to the units, acceptable ranges, and coding of variables in the database was provided by RIHMI-WDC to CDIAC. This information provided a basis for data checks performed by CDIAC and comprises the bulk of the database description presented in Sect. 7. Descriptions of data checks performed and a few general comments on findings are presented below.

Station numbers in data files were verified through comparison with station inventory information provided in a separate file by RIHMI-WDC and also through the WMO website (www.wmo.int).

Dates in data records were checked. Checks included:

  • ensuring that the year of all 6-hourly observations was between 1936 and 1965 and that the year of all 3-hourly observations was between 1966 and 2000;
  • ensuring that the month, day, and hour of each observation contained reasonable values (e.g., all months were checked for the correct number of days, and the hour of each observation was checked to make sure it corresponded with the hourly increments prescribed in the RIHMI-WDC documentation); and
  • ensuring that data records were sorted chronologically.

Gaps were searched for in the period of record of each station. This included

  • looking for missing individual hourly entries. Where these were discovered, an entry with the appropriate time was inserted that included missing indicators (composed of "9"s) for all meteorological variables. This was done to maintain hour-to-hour continuity (i.e., four and eight entries per day, for the 6- and 3-hourly observations, respectively);
  • checking for missing days in each month that had at least partial data for the month (hourly entries with missing data codes were inserted for the few missing days that were found); and
  • checking for missing months or years of data. This type of occurrence is fairly common in the database. Records with missing data values were not inserted where these larger-scale gaps occurred; rather, these occurrences have been detailed in Table 2.

Values for each variable were checked to make sure they were within the acceptable and reasonable ranges prescribed in the RIHMI-WDC documentation. When values outside these ranges were discovered, the complement and/or quality flags associated with that particular variable were set to 9 to indicate suspect data. (See the section on the station data files below in Sect. 7 for details on ranges and data flags.)

Values of all data flags were checked for validity using the RIHMI-WDC documentation. Flags determined to be invalid based upon RIHMI-WDC documentation were set to 9 to indicate that the associated data value should be interpreted with caution.

7. File Descriptions

This section describes the 238 files contained in this database. In addition to the 223 data files there are also 15 files that include associated documentation and FORTRAN and SAS codes for reading the data files.

  • Documentation File For NDP-048 (ndp048.txt) - This file is an ASCII version of this HTML documentation. It exists for the benefit of those downloading the database directly from CDIAC's anonymous FTP site without the use of a web browser.
  • Fortran and SAS Data Retrieval Programs (.for and .sas files) - These files are provided for the benefit of users with FORTRAN or SAS on their systems, enabling them to read any of the data files in this database using these software packages. The program files are:
    • invent.for - a FORTRAN program for reading the station inventory file (station.inv)
    • gaps.for - a FORTRAN program for reading the file containing information on gaps in the period of record for each station (gaps.dat)
    • timezone.for - a FORTRAN program for reading the file containing timezone information (timezone.dat)
    • history.for - a FORTRAN program for reading the station history file (station.his)
    • data.for - a FORTRAN program for reading any of the station data files
    • invent.sas - contains a SAS® program for reading the station inventory file (station.inv)
    • gaps.sas - a SAS® program for reading the file containing information on gaps in the period of record for each station (gaps.dat)
    • timezone.sas - a SAS® program for reading the file containing timezone information (timezone.dat)
    • history.sas - a SAS® program for reading the station history file (station.his)
    • data.sas - a SAS® program for reading any of the station data files
  • Station Inventory File (station.inv)

    Each record of the station inventory file contains a station's sequence number (1-223), WMO station number, name, latitude, longitude, elevation, beginning month and year of record, and ending month and year of record. The file may be read using invent.for or invent.sas. Stated in tabular form, the contents include

                       Variable     Variable   Starting       Ending
         Variable        type       width        column       column
    
         SEQNUM        Numeric         3           1            3
         WMO           Numeric         5           5            9
         NAME          Character      25          11           35
         LAT           Numeric         5          37           41
         LON           Numeric         7          43           49
         ELEV          Numeric         6          51           56
         BMONTH        Numeric         2          61           62
         BYEAR         Numeric         4          64           67
         EMONTH        Numeric         2          69           70
         EYEAR         Numeric         4          72           75
    
    
         where
    
                SEQNUM  is the sequence number of the station in the data base (1-223);
    
                WMO     is the WMO No. of the station;
    
                NAME    is the name of the station;
    
                LAT     is the latitude of the station in decimal degrees north;
    
                LON     is the longitude of the station in decimal degrees east;
    
                ELEV    is the elevation of the station above sea level (meters) missing elevations
                            are coded as -999.9;
    
                BMONTH      is the beginning month of the station's period of record;
    
                BYEAR       is the beginning year of the station's period of record;
    
                EMONTH      is the ending month of the station's period of record; and
    
                EYEAR       is the ending year of the station's period of record.
    
    

    Data Gaps File (gaps.dat) - This file contains information on stations that have at least one gap of at least one month in duration at any time during their period of record. There are only two variables in the file: WMO (WMO station number), a numeric variable in columns 1-5, and GAP (month/year with no data or the range of months/years with no data), a character variable in columns 9-25. Many stations have more than one record in this file, due to multiple gaps in their periods of record. This file may be read with gaps.for or gaps.sas.

    Station Timezone File (timezone.dat) - This file contains information for converting observations at each former U.S.S.R. station from GMT (the time given in the data files) to LMT. There are only two variables in the file: WMO (WMO station number), a numeric variable in columns 1-5, and ZONE (the number of hours that must be added to the GMT of an observation to obtain the LMT of the observation), a numeric variable in columns 7-8 ranging from 3 to 13 h. This file may be read with timezone.for or timezone.sas.

    Further data checks performed as part of updating the FSU database through 1990 (the previous version of the database) uncovered evidence of several stations requiring a new timezone assignment at some point in their period of record in order for the data to be properly sorted over time. The main check made use of the variable PTND, which is the reported change in station pressure from the previous observation to the current observation. Taking the difference of actual station pressure values from successive observations and comparing this difference to the value of PTND occasionally produced conflicting results. This always signaled a point in a station's record where the hourly values needed to be sorted differently from that point forward so as to be serially correct. It is uncertain whether these needed modifications resulted from actual changes in official timezone designation at stations or from changes in local observing time. This information is important for users who wish to calculate the correct LMT of observations. The required adjustment is to increase the value of the variable ZONE in (timezone.dat) by 1 hour for particular stations beyond specific dates. Stations that this applies to are given below by WMO station number with the required date of change.

    24966 - October 1, 1981
    25551 - January 1, 1982
    27648 - January 1, 1970
    27947 - April 1, 1981
    34123 - April 1, 1981
    34139 - April 1, 1981

    In addition, further QA checks determined that the correct value of the ZONE variable for Kolpasev (WMO No. 29231) is 7, not 5 as given in Razuvaev et al. (1995). The file timezone.dat has been modified accordingly.

    Station History File (station.his) - This file contains information on rain gauge replacement dates and the date, direction, and distance of any station relocations. It only reflects information available as of the late 1980s. There are two types of entries for each station. One type contains the station's WMO No. and rain gauge replacement date. The other type contains the station's WMO No. and a relocation date, distance, and direction. The file is sorted by WMO No., year, month, and day. This file may be read using history.for or history.sas. Stated in tabular form, the contents include

                            Variable     Variable       Starting     Ending
         Variable             type        width          column      column
    
         WMO                Numeric        5               1           5
         TYPE               Character      4               7          10
         YEAR               Numeric        4              12          15
         MONTH              Numeric        2              17          18
         DAY                Numeric        2              20          21
         DIST               Character      2              23          24
         DIRECT             Character      3              26          28
    
    
         where
    
           WMO       is the WMO No. of the station;
    
           TYPE      is the type of change indicated by this entry.  The possible values of TYPE
                     are as follows:
    
                     RAIN    = rain gauge replacement (i.e., change from old-type gauge
                               to Tretyakov-type gauge).  Each station will have only one
                               RAIN entry.  When this type of entry is used, DIST and
                               DIRECT (described below) are not relevant and thus are
                               coded as blanks;
    
                     MOVE    = station relocation.  Each station will have at least one
                               MOVE entry.  If a station moved on more than one
                               occasion, then separate entries are included for each
                               relocation.  If a station never moved, then that station will
                               have only one MOVE entry; in this entry, YEAR,
                               MONTH, DAY, DIST, and DIRECT (described below) are
                               all coded as missing.  In other words, if a station has only
                               one MOVE entry, and if all variables in that MOVE entry
                               are coded as missing, then the given station never moved;
    
           YEAR    is the year in which the change took place.  Missing years are coded as
                   999;
    
           MONTH   is the month in which the change took place.  Missing months are coded
                   as  9;
    
           DAY     is the day on which the change took place.  Missing days are coded as  9;
    
           DIST    is the distance (km)  that the station was moved.  Missing distances are
                   coded as  9.  A distance of zero indicates that the station moved less than 1
                   km.  DIST only applies to station relocation entries (i.e., lines in which
                   TYPE = MOVE).  In rain gauge replacement entries (i.e., lines in which
                   TYPE = RAIN), DIST is not relevant and thus is coded as blanks; and
    
           DIRECT  is the direction in which the station was moved (e.g., N = north, SE =
                   southeast).  Missing directions are coded as  99.  DIRECT only applies to
                   station relocation entries (i.e., lines in which TYPE = MOVE).  In rain
                   gauge replacement entries (i.e., lines in which TYPE = RAIN), DIRECT is
                   not relevant and thus is coded as blanks.
    
    

    Station Data Files (XXXXX.dat) - These files (where "XXXXX" is filled with a particular station's 5-digit WMO station number) contain the 6- and 3-hourly meteorological observations from the stations. They may be read with data.for or data.sas. The date and time in all data records correspond with GMT. Stated in tabular form, the contents include the following numeric variables

                               Variable       Starting       Ending
         Variable              width          column         column
    
    
         WMO                     5               1              5
         YEAR                    4               6              9
         MONTH                   2              10             11
         DAY                     2              12             13
         HOUR                    2              14             15
         RH                      3              16             18
         RHQF                    1              19             19
         VAPORP                  3              20             22
         VAPQF                   1              23             23
         SLP                     5              24             28
         SLPQF                   1              29             29
         HDEF                    3              30             32
         HDEFQF                  1              33             33
         PCHR                    1              34             34
         PCHRQF                  1              35             35
         PTND                    3              36             38
         PTNDQF                  1              39             39
         VIS                     2              40             41
         VISCF                   1              42             42
         VISQF                   1              43             43
         HCLD                    2              44             45
         HCLDCF                  1              46             46
         HCLDQF                  1              47             47
         TDEW                    3              48             50
         TDEWQF                  1              51             51
         GRND                    1              52             52
         GRNDQF                  1              53             53
         TCLD                    2              54             55
         TCLDCF                  1              56             56
         TCLDQF                  1              57             57
         LCLD                    2              58             59
         LCLDCF                  1              60             60
         LCLDQF                  1              61             61
         WDIR                    2              62             63
         WDIRQF                  1              64             64
         WSPD                    2              65             66
         WSPDQF                  1              67             67
         PRCP                    4              68             71
         PRCPCF                  1              72             72
         PRCPQF                  1              73             73
         STAP                    5              74             78
         STAPQF                  1              79             79
         SOILT                   3              80             82
         SOILQF                  1              83             83
         W                       1              84             84
         WCF                     1              85             85
         WQF                     1              86             86
         WW                      2              87             88
         WWQF                    1              89             89
         AIRT                    4              90             93
         AIRTQF                  1              94             94
         APH1                    1              95             95
         APH1CF                  1              96             96
         APH1QF                  1              97             97
         APH2                    1              98             98
         APH2CF                  1              99             99
         APH2QF                  1             100            100
         APH3                    1             101            101
         APH3CF                  1             102            102
         APH3QF                  1             103            103
         APH4                    1             104            104
         APH4CF                  1             105            105
         APH4QF                  1             106            106
         APH5                    1             107            107
         APH5CF                  1             108            108
         APH5QF                  1             109            109
         APH6                    1             110            110
         APH6CF                  1             111            111
         APH6QF                  1             112            112
         APH7                    1             113            113
         APH7CF                  1             114            114
         APH7QF                  1             115            115
         CLDH                    1             116            116
         CLDHCF                  1             117            117
         CLDHQF                  1             118            118
         CLDM                    1             119            119
         CLDMQF                  1             120            120
         CLDL1                   1             121            121
         CLDL1F                  1             122            122
         CLDL2                   1             123            123
         CLDL2F                  1             124            124
         CLDL3                   1             125            125
         CLDL3F                  1             126            126
         WIR                     1             127            127
         WIRF                    1             128            128
    
    
         where
    
                WMO          is the WMO number of the station;
    
                YEAR         is the year (Greenwich) of the observations in the record;
    
                MONTH        is the month (Greenwich) of the observations in the record;
    
                DAY          is the day (Greenwich) of the observations in the record;
    
                HOUR         is the GMT of the observations in the record;
    
                RH           is the relative humidity of the air (expressed in percent) as determined by
                             use of a psychrometer.  Relative humidity is defined as the ratio of the
                             observed vapor pressure to the saturation vapor pressure for the observed
                             air temperature.  Values of observations may range from 0 to 100%.
                             Missing observations are coded as 999;
    
                RHQF         is the quality flag for the relative humidity observation (0 indicates a valid
                             observation; 9 indicates a suspect or missing observation);
    
                VAPORP       is the water vapor pressure of the air [expressed in tenths of hectopascals
                             (hPa)] as determined by use of a psychrometer.  The water vapor pressure
                             is the partial pressure of the water vapor contained in the air.  Values of
                             observations considered valid may range from 0.0 to 95.0 hPa.  Missing
                             observations are coded as 999;
    
                VAPQF        is the quality flag for the water vapor pressure observation (0 indicates a
                             valid observation; 9 indicates a suspect or missing observation);
    
                SLP          is the sea level pressure of the air (expressed in tenths of hPa) as
                             determined by use of a barometer.  Because a station would rarely be able
                             to position a barometer precisely at sea level, the air pressure measured at
                             a station is "reduced" to sea level by using a standard barometric height
                             formula.  Values of observations considered valid may range from 900.0 to
                             1100.0 hPa.  At stations located above a certain elevation (500 m through
                             1980; 800 m since 1981), air pressure is not reduced to sea level, but is
                             assigned the missing code 99999;
    
                SLPQF        is the quality flag for the sea level pressure observation (0 indicates a valid
                             observation; 9 indicates a suspect or missing observation);
    
                HDEF         is the humidity deficit (saturation deficiency); the difference between the
                             saturation vapor pressure and the actual water vapor pressure at a given
                             temperature and pressure as measured in tenths of hPa.  Valid values may
                             range from 0.0 to 95.0 hPa.  Missing observations are coded as 999;
    
                HDEFQF       is the quality flag for the humidity deficit observation (0 indicates a valid
                             observation; 9 indicates a suspect or missing observation);
    
    
                PCHR         is the pressure tendency characteristic, corresponding to the shape of the
                             barograph trace of air pressure at the station for the preceding 3-h period.
                             This is a coded value ranging from 0 to 8, as explained below (a missing
                             value is coded as 9):
    
                   0  =  increasing, then decreasing; pressure unchanged or higher than 3 h ago;
                   1  =  increasing, then steady; increasing, then weaker increase;
                         current pressure is higher than 3 h ago;
                   2  =  uniform or non-uniform increase; current pressure is higher than 3 h ago;
                   3  =  decreasing, then increasing; steady, then increasing; or
                         increasing, then increasing more rapidly; current pressure is
                         higher than 3 h ago;;
                   4  =  steady; pressure is the same as 3 h ago;
                   5  =  decreasing, then increasing; pressure is the same or lower than 3 h ago;
                   6  =  decreasing, then steady; or decreasing then decreasing more
                         slowly; current pressure is lower than 3 h ago;
                   7  =  decreasing steadily or unsteadily; current pressure is lower than 3 h ago;
                   8  =  increasing, then decreasing; steady, then decreasing; or
                         decreasing, then decreasing more quickly; current pressure is
                         lower than 3 h ago;
    
                PCHRQF    is the quality flag for the pressure tendency characteristic (0 indicates a
                          valid observation; 9 indicates a suspect or missing observation);
    
                PTND      is the pressure tendency value (i.e., the absolute difference between the
                          current air pressure at the station and that which was observed 3 h before).
                          The sign of PTND is indicated by the value of PCHR: if PCHR is equal to
                          0, 1, 2, or 3, then PTND is positive; if PCHR is equal to 4 then PTND
                          should equal 0; and, if PCHR is equal to 5, 6, 7, or 8, then PTND is
                          negative.  Values are given in tenths of hPa; observations considered valid
                          may range from 0.0 to 20.0 hPa, and a missing observation is coded as
                          999);
    
                PTNDQF    is the quality flag for the pressure tendency value (0 indicates a valid
                          observation; 9 indicates a suspect or missing observation);
    
                VIS       is the horizontal visibility, given as a coded value indicating distance in
                          km.  The horizontal visibility is defined as the maximum distance at which
                          an absolutely black body of rather large angular dimensions (over 15
                          angular min) can be distinguished against the background of the sky in
                          daylight, or the distance at which an unfocused light source of a given
                          intensity becomes indistinguishable at night.  Horizontal visibility depends
                          on atmospheric phenomena.  Thus, in the fog it can be reduced to zero,
                          while in clear arctic air it can reach hundreds of kilometers.  Coded values
                          may range from 00 to 50 and from 56 to 99.  Codes 00-50 and 56-89 are
                          used when visibility is measured using instruments; codes 90-99 are used
                          when visibility is estimated visually.  The codes and their meanings are as
                          follows:
    
                   00-50  =    indicates visibility in tenths of km (i.e., 0.0 km to 5.0 km).
                               For example, 25 = 2.5 km (00 is the code for visibility less
                               than 0.1 km);
                   51-55  =    not used;
                   56-80  =    the range 6 km to 30 km.  Visibility in whole kilometers
                               may be determined by subtracting 50 from the code, e.g., a
                               code of 65 indicates the visibility is 15 km;
                   81     =    35 km;
                   82     =    40 km;
                   83     =    45 km;
                   84     =    50 km;
                   85     =    55 km;
                   86     =    60 km;
                   87     =    65 km;
                   88     =    70 km;
                   89     =    >70 km;
                   90     =    <0.05 km;
                   91     =    0.05 km;
                   92     =    0.2 km;
                   93     =    0.5 km;
                   94     =    1 km (about 1/2 mile);
                   95     =    2 km (about 1 mile);
                   96     =    4 km (about 2 miles);
                   97     =    10 km (about 6 miles);
                   98     =    20 km (about 12 miles); and
                   99     =    >50 km (>30 miles).
    
                   If VIS = 99 with both the complement and quality flags set to 9 (see
                   below), the observation is missing.
    
                VISCF     is the horizontal visibility complement flag.  VISCF = 0 indicates the
                          visibility corresponds to the value given for VIS; VISCF = 1 indicates the
                          visibility is actually greater than the value given for VIS; VISCF =  9
                          indicates a suspect or missing observation;
    
                VISQF     is the quality flag for the horizontal visibility value (0 indicates a valid
                          observation; 9 indicates a suspect or missing observation);
    
                HCLD is the height above ground of the base of the lowest cloud.  This height is
                usually coded in hundreds of meters, as detailed in the following:
    
                   00     =   less than or equal to 50 m with fog present;
                   01-25  =   100 m to 2500 m, e.g., 10 = 1000 m;
                   98     =   no clouds below 2500 m, however there may be mid- or
                              high-level clouds whose height has not been determined;
                   99     =   no clouds or traces of clouds whose height has not been
                              determined; or observation is missing if both complement
                              and quality flags are set to 9 (see below);
    
                HCLDCF  is the complement flag for the lowest cloud height observation.  A value of
                        0 means the height was measured using instrumentation; a value of 1
                        indicates the height was estimated visually.  This flag is set to 9 in the
                        case of a suspect or missing observation;
    
                HCLDQF  is the quality flag for the lowest cloud height observation (0 indicates a
                        valid observation; 9 indicates a suspect or missing observation);
    
                TDEW    is the dew point temperature in whole degrees celsius.  The dew point
                        temperature is defined as the temperature to which moist air must be
                        cooled, with air pressure and water vapor pressure held constant, in order
                        that it just reach saturation with respect to the water in the air.  The dew
                        point is determined by using a psychrometer.  Observations considered
                        valid may range from -70° to +40°C.  Missing observations are coded as 999;
    
                TDEWQF  is the quality flag for the dew point temperature (0 indicates a valid
                        observation; 9 indicates a suspect or missing observation);
    
                GRND    is the ground state, a visual observation of the state of the ground surface
                        in the vicinity of the station made usually near 0800 and 2000 LMT.  This
                        is a coded value as detailed in the following:
    
                   0  =  surface of ground dry (no appreciable amount of dust or loose sand);
                   1  =  surface of ground moist (no pools);
                   2  =  surface of ground wet (standing water in small or large pools on surface);
                   3  =  surface of ground frozen;
                   4  =  glaze on ground, but no snow or melting snow;
                   5  =  ice, snow, or melting snow covering less than one-half of the ground;
                   6  =  ice, snow, or melting snow covering more than one-half of the ground;
                   7  =  ice, snow, or melting snow covering ground completely;
                   8  =  loose dry snow, dust, or sand covering more than one-half of the ground;
                   9  =  loose dry snow, dust, or sand covering ground completely (if GRNDQF = 0;
                         otherwise, the observation is missing);
    
                GRNDQF  is the quality flag for the ground state observation (0 indicates a valid
                        observation; 9 indicates a suspect or missing observation);
    
                TCLD    is the total cloud amount, estimated visually by an observer according to a
                        10-point system (i.e., in tenths of sky cover).  A value of 0 indicates no
                        clouds present or <1/10 sky cover, a value of 10 indicates an overcast sky
                        (with or without gaps amounting to <1/10 sky cover; see explanation of
                        complement flag below), and a value of 99 indicates a missing
                        observation.  The gaps between individual cloud elements, typical of some
                        cloud genera (e.g., altocumulus and stratocumulus) are not to be included
                        as part of the total cloud cover estimate (i.e., they are counted as clear sky);
    
                TCLDCF  is the total cloud amount complement flag.  TCLDCF = 1 is used if
                        10-point cloudiness (overcast) is observed with gaps; TCLDCF = 0 is
                        coded for all other valid cloud amounts; and TCLDCF = 9 indicates a
                        suspect or missing observation;
    
                TCLDQF  is the quality flag for the total cloud amount observation (0 indicates a
                        valid observation; 9 indicates a suspect or missing observation);
    
                LCLD    is the low-cloud amount, estimated visually by an observer according to a
                        10-point system (i.e., in tenths of sky cover).  A value of 0 indicates no
                        low clouds present or <1/10 of the sky is covered with low clouds.  The
                        gaps between individual cloud elements, typical of some cloud genera
                        (e.g., stratocumulus and cumulus) are not to be included as part of the low
                        cloud  cover estimate (i.e., they are counted as clear sky).  Missing
                        observations are coded as 99;
    
                LCLDCF  is the low-cloud amount complement flag.  TCLDCF = 1 is used if
                        10-point cloudiness (overcast) is observed with gaps; TCLDCF  = 0 is
                        coded for all other valid low-cloud amounts; and TCLDCF = 9 indicates a
                        suspect or missing observation;
    
                LCLDQF  is the quality flag for the total cloud amount observation (0 indicates a
                        valid observation; 9 indicates a suspect or missing observation);
    
                WDIR    is the direction from which the wind is blowing, as measured 10-12 m
                        above ground level.  This is a coded observation, the values for which are
                        given as follows:
    
                   Code     Wind direction
                   ---- --------------
                   00   =   calm winds
                   02   =   NNE
                   05   =   NE
                   07   =   ENE
                   09   =   E
                   11   =   ESE
                   14   =   SE
                   16   =   SSE
                   18   =   S
                   20   =   SSW
                   23   =   SW
                   25   =   WSW
                   27   =   W
                   29   =   WNW
                   32   =   NW
                   34   =   NNW
                   36   =   N
                   99   =   variable winds (if WDIRQF = 0; otherwise, the observation is missing);
    
                WDIRQF  is the quality flag for the wind direction observation (0 indicates a valid
                        observation; 9 indicates a suspect or missing observation).  Missing
                        observations are coded as 99;
    
                WSPD    is the wind speed in m/s as measured 10-12 m above ground level.
                        Observations considered valid may range from 0 to 60 m/s;
    
                WSPDQF  is the quality flag for the wind speed observation (0 indicates a valid
                        observation; 9 indicates a suspect or missing observation);
    
                PRCP    is the precipitation amount to the nearest tenth of a millimeter.
                        Observations considered valid may range from 0 to 5000 (0 mm to 500 mm).
                        Missing observations are coded as 9999.  Rain gauges are positioned
                        2 m above ground level, and were read at 0700 and 1900 LMT from 1936
                        through 1965.  In 1946, the old-style gauge (exact type unknown) was
                        replaced with the Tretyakov-type gauge (see Appendix A for the date of
                        implementation at each site).  Beginning in 1966, gauges were read at
                        0300, 0900, 1500, and 2100 MLT in timezone 2; at 0300, 0600, 1500,
                        and 1800 MLT in zones 3-5; at 0300 and 1500 MLT in zones 6-8; at
                        0000, 0300, 1200, and 1500 MLT in zones 9-11; and at 2100, 0300, 0900,
                        and 1500 MLT in zone 12.  Also, beginning in 1966, wetting corrections
                        of  0.2 mm were applied to each hourly measurement.  (Because four
                        observations per day were collected at stations in timezones 2-5 and
                        9-12, four corrections were counted in the calculation of daily totals;
                        therefore, total daily corrections are higher for stations in these areas.)
                        From 1966 onward, readings at some stations were also taken at the
                        observing hours closest to 0800 and 2000 LMT.  Beginning in 1986,
                        readings at 0300 and 1500 MLT were discontinued at all stations except
                        those in timezone 2.  (The term "timezone" in the preceding corresponds
                        to assigning the numbers 1-12 to 12 timezones stretching from west to
                        east across the FSU.   The timezone of each station in this
                        sense may be obtained by subtracting 1 from the value of the ZONE
                        variable in the file timezone.dat.)
    
                PRCPCF  is the precipitation amount complement flag.  It is set to 1 if a trace of
                        precipitation has been measured, i.e., <0.1 mm.  This flag is set to 0 for all
                        other valid precipitation observations, and is set to 9 for suspect or missing
                        precipitation observations;
    
                PRCPQF  is the quality flag for the precipitation amount (0 indicates a valid
                        observation; 9 indicates a suspect or missing observation);
    
                STAP    is the pressure of the air at station level (expressed in tenths of hPa) as
                        determined by use of a barometer.  Values of observations considered valid
                        may range from 600.0 to 1100.0 hPa.  Validity is of course assessed by
                        considering factors such as the station's elevation above sea level,
                        geographic location, season, and pressures at neighboring stations.
                        Missing observations are coded as 99999;
    
                STAPQF  is the quality flag for the station level pressure observation (0 indicates a
                        valid observation; 9 indicates a suspect or missing observation);
    
                SOILT   is the soil surface temperature, expressed in whole degrees celsius.  Soil
                        surface temperature is measured at a smooth, unshaded site that is devoid
                        of vegetation.  When the ground is snow-covered, the thermometer  is
                        placed on the snow surface and the temperature of the snow cover is
                        measured.  Observations considered valid may range from -75 to +75°C.
                        Missing observations are coded as 999;
    
                SOILQF  is the quality flag for the soil surface temperature (0 indicates a valid
                        observation; 9 indicates a suspect or missing observation);
    
                W       is the past weather code, used in describing the meteorological conditions
                        observed between the past and current observations.  At 0000, 0600, 1200,
                        and 1800 GMT this code describes weather from the previous 6-hour
                        period; at 0300, 0900, 1500, and 2100 GMT it describes weather for the
                        previous 3-hour period.  The codes and their meanings are as follows:
    
                    0  =  clear sky or no more than 5/10s cloud amount;
                    1  =  variable sky; cloud amount was both less than and greater than
                          5/10 sky cover during the preceding three hours;
                    2  =  overcast or cloud amount greater than 5/10s;
                    3  =  sand or dust storm, or drifting or blowing snow;
                    4  =  fog, ice fog, or thick haze or smoke;
                    5  =  drizzle;
                    6  =  rain;
                    7  =  snow, or rain and snow mixed;
                    8  =  shower(s);
                    9  =  thunderstorm, with or without precipitation (if WQF = 0;
                          otherwise, the observation is missing);
    
                WCF     is the past weather complement flag.  It is set to 0 when used with the
                        previously defined past weather codes, however it is set to 1 for past
                        weather codes 3, 7, and 8 if the past weather also included a snowstorm.
                        The complement flag is set to 9 in the case of a suspect or missing past
                        weather observation;
    
                WQF     is the quality flag for the past weather observation (0 indicates a valid
                        observation; 9 indicates a suspect or missing observation);
    
                WW      is the present weather code, reflecting the meteorological conditions at the
                        time of observation or during the preceding 1-h period.  Codes range from
                        00 to 99 and are defined as follows:
    
                     Code         Present weather
                 ----         ---------------
                     00-19   =    no precipitation, fog, dust storm, sandstorm, drifting or
                                  blowing snow at the station at the time of observation
                                  and, except for codes 09 and 17, during preceding hour;
    
                     00      =    cloud development conditions unknown;
                     01      =    cloud generally dispersing;
                     02      =    state of sky on the whole unchanged;
                     03      =    clouds generally forming or developing;
                     04      =    visibility reduced by smoke or volcanic ash;
                     05      =    haze;
                     06      =    widespread dust in suspension in the air;
                     07      =    dust or sand raised by wind at or near the station at the
                                  time of observation;
                     08      =    well developed dust whirl(s) seen at or near the station;
                     09      =    dust storm within sight;
                     10      =    mist, steam mist (light fog);
                     11      =    patches of shallow fog, or, from 1966 onward, ice fog;
                     12      =    more or less continuous shallow fog, or, from 1966
                                  onward, ice fog;
                     13      =    lightning visible, no thunder heard;
                     14      =    precipitation within sight, not reaching the ground;
                     15      =    precipitation within sight, reaching the ground or the
                                  surface of the sea, but distant (i.e., estimated to be
                                  more than 5 km from the station);
                     16      =    precipitation within sight, reaching the ground or the
                                  surface of the sea, near to, but not at the station;
                     17      =    thunderstorm, but no precipitation at the station or
                                  within sight;
                     18      =    squall;
                     19      =    funnel cloud;
    
                     -----------------------------------------------------------------------
    
                     20-29   =    precipitation, fog, ice fog, or thunderstorm at the
                                  station during the preceding hour but not at the time of
                                  the observation;
    
                     20      =    drizzle or snow grains;
                     21      =    rain;
                     22      =    snow;
                     23      =    rain and snow or ice pellets;
                     24      =    freezing drizzle or freezing rain;
                     25      =    showers of rain;
                     26      =    showers of snow, or of rain and snow;
                     27      =    shower of hail, or ice pellets;
                     28      =    fog or ice fog;
                     29      =    thunderstorm;
    
                     -----------------------------------------------------------------------
    
                     30-39   =    dust storm or sandstorm, drifting or blowing snow at
                                  the time of observation;
    
                     30      =    slight or moderate dust storm or sandstorm subsiding;
                     31      =    slight or moderate dust storm or sandstorm, no
                                  appreciable change during the preceding hour;
                     32      =    slight or moderate dust storm or sandstorm, increasing;
                     33      =    severe dust storm or sandstorm, decreasing;
                     34      =    severe dust storm or sandstorm with no appreciable change;
                     35      =    severe dust storm or sandstorm, increasing;
                     36      =    slight or moderate drifting snow;
                     37      =    heavy drifting snow;
                     38      =    slight or moderate blowing snow;
                     39      =    heavy blowing snow;
    
                     -----------------------------------------------------------------------
    
                     40-49   =    fog or ice fog at the time of observation;
    
                     40      =    fog or ice fog near the station;
                     41      =    fog or ice fog in patches;
                     42      =    fog or ice fog decreasing, sky discernible;
                     43      =    fog or ice fog decreasing, sky not discernible;
                     44      =    fog, or, from 1966 onward, ice fog; sky discernible; no
                                  appreciable change;
                     45      =    fog, or, from 1966 onward, ice fog; sky not
                                  discernible; no appreciable change;
                     46      =    fog or ice fog, sky discernible, becoming thicker;
                     47      =    fog or ice fog, sky not discernible, becoming thicker;
                     48      =    fog, depositing rime, sky discernible;
                     49      =    fog, depositing rime, sky not discernible;
    
                     -----------------------------------------------------------------------
    
                     50-59   =    drizzle at the station at the time of observation;
    
                     50      =    drizzle intermittent, slight at time of observation;
                     51      =    drizzle continuous, slight at time of observation;
                     52      =    drizzle intermittent, moderate at time of observation;
                     53      =    drizzle continuous, moderate at time of observation;
                     54      =    drizzle intermittent, heavy at time of observation;
                     55      =    drizzle continuous, heavy at time of observation;
                     56      =    drizzle, freezing, slight;
                     57      =    drizzle, freezing, heavy;
                     58      =    drizzle and rain, moderate or heavy;
                     59      =    drizzle and rain, moderate or heavy;
    
                     -----------------------------------------------------------------------
    
                     60-69   =    rain at the station at the time of observation;
    
                     60      =    rain intermittent, slight;
                     61      =    rain continuous, slight;
                     62      =    rain intermittent, moderate;
                     63      =    rain continuous, moderate;
                     64      =    rain intermittent, heavy;
                     65      =    rain continuous, heavy;
                     66      =    rain, freezing, slight;
                     67      =    rain, freezing, moderate or heavy;
                     68      =    rain or drizzle and snow, slight;
                     69      =    rain or drizzle and snow, moderate or heavy;
    
                     -----------------------------------------------------------------------
    
                     70-79   =    solid precipitation not in showers at the time of
                                       observation;
    
                     70      =    intermittent fall of snow flakes, slight;
                     71      =    continuous fall of snow flakes, slight;
                     72      =    intermittent fall of snow flakes, moderate;
                     73      =    continuous fall of snow flakes, moderate;
                     74      =    intermittent fall of snow flakes, heavy;
                     75      =    continuous fall of snow flakes, heavy;
                     76      =    diamond dust;
                     77      =    snow grains;
                     78      =    isolated starlike snow crystals;
                     79      =    ice pellets;
    
                     -----------------------------------------------------------------------
    
                     80-90   =    showery precipitation at the time of observation;
    
                     80      =    rain shower(s), slight;
                     81      =    rain shower(s), moderate or heavy;
                     82      =    rain shower(s), violent;
                     83      =    shower(s) of rain and snow mixed, slight;
                     84      =    shower(s) of rain and snow mixed, moderate or heavy;
                     85      =    snow shower(s), slight;
                     86      =    snow shower(s), moderate or heavy;
                     87      =    shower(s) of snow pellets or small hail, slight;
                     88      =    shower(s) of snow pellets or small hail, moderate or heavy;
                     89      =    shower(s) of hail, slight;
                     90      =    shower(s) of hail, moderate or heavy;
    
                     -----------------------------------------------------------------------
    
                     91-99   =    thunderstorm during the preceding hour or at the time
                                  of observation;
    
                     91      =    slight rain at time of observation, thunderstorm during
                                  the preceding hour;
                     92      =    moderate or heavy rain at time of observation,
                                  thunderstorm during the preceding hour;
                     93      =    slight snow or hail at the time of observation,
                                  thunderstorm during the preceding hour;
                     94      =    moderate or heavy snow or hail at the time of
                                  observation, thunderstorm during preceding hour;
                     95      =    thunderstorm, slight or moderate with rain and/or snow
                                  at the time of observation;
                     96      =    thunderstorm, slight or moderate with hail at the time
                                  of observation;
                     97      =    thunderstorm, heavy, with rain or snow at time of
                                  observation;
                     98      =    thunderstorm, combined with dust storm or sandstorm
                                  at time of observation;
                     99      =    thunderstorm, heavy, with hail at the time of
                                  observation (if WWQF = 0; otherwise, the observation
                                  is missing);
    
                WWQF    is the quality flag for the present weather observation (0 indicates a valid
                        observation; 9 indicates a suspect or missing observation);
    
                AIRT    is the air temperature (tenths of degrees celsius), measured 2 m above
                        ground or snow surface level.  Observations considered valid may range
                        from -70.0° to +55.0°C.  Missing observations are coded as 9999;
    
                AIRTQF  is the quality flag for air temperature (0 indicates a valid observation; 9
                        indicates a suspect or missing observation);
    
                APH1-APH7    are seven atmospheric phenomena groups, used for reporting various
                             atmospheric phenomena during the ten minutes preceding the observation
                             hour.  These phenomena are observed visually, as are estimates of their
                             intensity.  Atmospheric phenomena intensity can be weak, moderate or
                             strong.  The phenomena are described by means of codes that are
                             particular to each of the seven groups.  A coded value of 0 indicates that
                             atmospheric phenomena were not observed at the time of observation.
                             Additional codes and their meanings are as follows:
    
                   APH1 group: 1    =    not used;
                               2    =    not used;
                               3    =    dew;
                               4    =    rime;
                               5    =    crystalline frost, grain frost;
                               6    =    glazed frost;
                               7    =    rime and crystalline frost;
                               8    =    rime and glazed frost;
                               9    =    crystalline frost and glazed frost;
    
                   APH2 group: 1    =    not used before 1966, from 1966 onward: snow haze;
                               2    =    haze;
                               3    =    mist;
                               4    =    ground fog;
                               5    =    crystalline fog, sky visible;
                               6    =    ice fog;
                               7    =    fog, sky visible;
                               8    =    fog;
                               9    =    not used before 1966, from 1966 onward: shallow ice fog;
    
                   APH3 group: 1    =    drifting dust;
                               2    =    funnel cloud;
                               3    =    dust storm;
                               4    =    whirl;
                               5    =    drifting snow;
                               6    =    blowing snow;
                               7    =    blizzard;
                               8    =    snow storm;
                               9    =    not used;
    
                   APH4 group: 1    =    before 1966: corona around sun/moon; not used
                                         from 1966 onward;
                               2    =    sunshine;
                               3    =    before 1966: halo around sun/moon; not used from
                                         1966 onward;
                               4    =    snow grains and sunshine;
                               5    =    snow pellets and sunshine;
                               6    =    snow grains;
                               7    =    snow pellets;
                               8    =    ice pellets;
                               9    =    ice pellets and sunshine;
    
                   APH5 group: 1    =    not used;
                               2    =    glazed rain;
                               3    =    drizzle;
                               4    =    rain;
                               5    =    rain shower;
                               6    =    glazed rain, rain;
                               7    =    glazed rain, rain shower;
                               8    =    not used;
                               9    =    not used;
    
                   APH6 group: 1    =    not used;
                               2    =    mirage;
                               3    =    ice needles;
                               4    =    snow melting;
                               5    =    snow melting shower;
                               6    =    not used;
                               7    =    snow;
                               8    =    snow shower;
                               9    =    not used;
    
                   APH7 group: 1    =    not used;
                               2    =    sea soaring (lake or river soaring);
                               3    =    polar lights;
                               4    =    sea soaring and polar lights;
                               5    =    summer lightning;
                               6    =    before 1966, thunderstorm in the distance; not used
                                         from 1966 onward;
                               7    =    thunderstorm;
                               8    =    hail;
                               9    =    thunderstorm and hail;
    
                APH1CF-  are the corresponding complement flags for the seven atmospheric
                APH7CF   phenomena groups.  These flags are used to denote whether or not an
                         observation has been made, and if so, to denote the intensity of the
                         phenomena.  A complement flag of 0 accompanying an atmospheric
                         phenomena code of 0 means none of the phenomena in a particular group
                         have been observed.  When accompanying a nonzero phenomena code, a
                         complement flag of 0 denotes phenomena of weak intensity, 1 denotes
                         moderate intensity, and 2 denotes strong intensity.  A complement flag of
                         9, when accompanied by a quality flag of 9 (see below) indicates a suspect
                         or missing observation;
    
                APH1QF-  are quality flags for the seven atmospheric phenomena groups (0 indicates
                APH7QF   a valid observation; 9 indicates a suspect or missing observation);
    
                CLDH     is the coded value for the high-level cloud type.  High clouds are defined
                         as those with bases higher than 6000 m and include cirrus (Ci),
                         cirrocumulus (Cc), and cirrostratus (Cs) clouds.  Codes have the following
                         meanings:
    
                      0  =  cloud type is not indicated, but low- or  mid-level clouds
                            observed, with total cloud amount ranging anywhere from 1/10
                            to overcast with gaps; high-level clouds are absent or amount
                            to less than 1/10 sky cover;
                      1  =  Ci;
                      2  =  Cc;
                      3  =  Cs;
                      4  =  Ci and Cc;
                      5  =  Ci and Cs;
                      6  =  Cc and Cs;
                      7  =  Ci, Cc, and Cs;
                      8  =  high cloud presence and type cannot be determined because of
                            continuous fog or snowstorm; or high-level cloud presence and
                            type cannot be determined because of overcast conditions at
                            lower levels;
                      9  =  complete absence of clouds or, in the case of translucent fog,
                            clear in the zenith (if CLDHQF =0; otherwise the observation
                            is missing);
    
                CLDHCF   is the high-level cloud type complement flag.  It is set to 0 when the
                         high-level cloud type has been determined with no fog present; set to 1
                         when the high-level cloud type has been determined with translucent fog
                         or when the high-level cloud type cannot be determined because of
                         continuous fog; and set to 9 if the high-level cloud type is suspect or
                         missing.
    
                CLDHQF   is the high-level cloud type quality flag (0 indicates a valid observation; 9
                         indicates a suspect or missing observation);
    
                CLDM     is the coded value for the mid-level cloud type.  Mid-level clouds are
                         defined as those with bases between 2000 m and 6000 m; they include
                         altocumulus (Ac) and altostratus (As) clouds.  Codes have the following
                         meanings:
    
                      0  =  cloud type is not indicated, but high-level clouds (amount
                            ranging from 1/10 to overcast) and/or low-level clouds (amount
                            ranging from 1/10 to overcast with gaps) observed; mid-level
                            clouds are absent or amount to less than 1/10 sky cover;
                      1  =  Ac;
                      2  =  As;
                      3  =  not used;
                      4  =  Ac and As;
                     5-7 =  not used;
                      8  =  mid-level cloud presence and type cannot be determined due to
                            fog or snowstorm; or mid-level cloud presence and type cannot
                            be determined because of overcast at lower levels;
                      9  =  complete absence of clouds or, in the case of translucent fog,
                            clear in the zenith (if CLDMQF =0; otherwise the observation
                            is missing);
    
                CLDMQF     is the mid-level cloud type quality flag (0 indicates a valid observation;
                           9 indicates a suspect or missing observation);
    
                CLDL1      is the first of three code groups for describing low-level cloud type.
                           Low-level clouds are defined as those with bases lower than 2000 m; they
                           include stratocumulus (Sc), stratus (St), nimbostratus (Ns), cumulus (Cu),
                           and cumulonimbus (Cb) clouds.  Codes have the following meanings:
    
                      0  =  cloud type is not indicated, but high- or  mid-level clouds
                            observed, with total cloud amount ranging anywhere from 1/10
                            to overcast; low-level clouds of the CLDL1 group (see below)
                            are absent or amount to less than 1/10 sky cover;
                      1  =  Cu;
                      2  =  Cb;
                      3  =  not used;
                      4  =  Cu and Cb;
                     5-7 =  not used;
                      8  =  low-level cloud presence and type cannot be determined due to
                            fog or snowstorm;
                      9  =  complete absence of clouds or, in the case of translucent fog,
                            clear in the zenith (if CLDL1F =0; otherwise the observation is
                            missing);
    
                CLDL1F     is the low-level cloud type quality flag for the first low-level cloud group
                           (0 indicates a valid observation; 9 indicates a suspect or missing
                           observation);
    
                CLDL2      is the second of three code groups for describing low-level cloud type.
                           Low-level clouds are defined as those with bases lower than 2000 m; they
                           include stratocumulus (Sc), stratus (St), nimbostratus (Ns), cumulus (Cu),
                           and cumulonimbus (Cb) clouds.  Codes have the following meanings:
    
                      0  =  cloud type is not indicated, but high- or  mid-level clouds
                            observed, with total cloud amount ranging anywhere from 1/10
                            to overcast; low-level clouds of the CLDL2 group (see below)
                            are absent or amount to less than 1/10 sky cover;
                      1  =  St;
                      2  =  Sc;
                      3  =  not used;
                      4  =  St and Sc;
                     5-7 =  not used;
                      8  =  low-level cloud presence and type cannot be determined due to
                            fog or snowstorm;
                      9  =  complete absence of clouds or, in the case of translucent fog,
                            clear in the zenith (if CLDL2F =0; otherwise the observation is
                            missing);
    
                CLDL2F     is the low-level cloud type quality flag for the second low-level cloud
                           group.  (0 indicates a valid observation; 9 indicates a suspect or missing
                           observation.);
    
                CLDL3      is the third of three code groups for describing low-level cloud type.
                           Low-level clouds are defined as those with bases lower than 2000 m; they
                           include stratocumulus (Sc), stratus (St), nimbostratus (Ns), cumulus (Cu),
                           and cumulonimbus (Cb) clouds.  Codes have the following meanings:
    
                      0  =  cloud type is not indicated, but high- or  mid-level clouds
                            observed, with total cloud amount ranging anywhere from 1/10
                            to overcast; low-level clouds of the CLDL3 group (see below)
                            are absent or amount to less than 1/10 sky cover;
                      1  =  not used;
                      2  =  Ns;
                      3  =  fractostratus (Fs) and fractocumulus (Fc) of bad weather (also
                            known as scud);
                     4-5 =  not used;
                      6  =  Ns and Frnb;
                      7  =  not used;
                      8  =  low-level cloud presence and type cannot be determined due to
                            fog or snowstorm;
                      9  =  complete absence of clouds or, in the case of translucent fog,
                            clear in the zenith (if CLDL3F =0; otherwise the observation is missing);
    
                CLDL3F     is the low-level cloud type quality flag for the third low-level cloud group
                           (0 indicates a valid observation; 9 indicates a suspect or missing
                           observation);
    
                WIR        is the wind irregularity characteristic.  It is a coded value used to describe
                           the wind speed as steady or gusty and the wind direction as constant or
                           variable.  The wind is considered to be steady if its speed remains
                           essentially constant over the course of two minutes; otherwise it is
                           considered gusty.  The wind direction is considered constant if over the
                           course of two minutes it varies within one compass point; otherwise it is
                           considered to be variable.  Observations of this variable are only present in
                           the 6-hourly data records (i.e., in the pre-1966 data).  The 3-hourly records
                           (1966 onward) contain a value of 9 to indicate missing data.  For the pre-
                           1966 data, a value of 9 is also used to indicate a missing value.  Codes for
                           observations have the following meanings:
    
                      0  =  no wind;
                      1  =  steady speed, constant direction;
                      2  =  steady, variable;
                      3  =  gusty, constant;
                      4  =  gusty, variable;
                      5  =  characteristic is not defined;
                      6  =  the wind speed and direction at this hour are considered suspect.
    
    
                WIRF       is the wind irregularity characteristic quality flag (0 indicates a valid
                           observation; 9 indicates a suspect or missing observation).
    
    

    8. References

    • Razuvaev, V. N., E. G. Apasova, and R. A. Martuganov. 1993. Daily Temperature and Precipitation Data for 223 USSR Stations. ORNL/CDIAC-56, NDP-040. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
    • Razuvaev, V. N., E. G. Apasova, and R. A. Martuganov. 1995. Six- and Three-Hourly Meteorological Observations from 223 USSR Stations. ORNL/CDIAC-66, NDP-048. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
    • Vose, R. S., R. L. Schmoyer, P. M. Steurer, T. C. Peterson, R. Heim, T. R. Karl, and J. K. Eischeid. 1992. The Global Historical Climatology Network: Long-term monthly temperature, precipitation, sea level pressure, and station pressure data. ORNL/CDIAC-53, NDP-041. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee.