Index of /ftp/ndp026e
START_README.NDP-026E*****2007_Nov*****_*********-*********-*********-*********-
This file contains 227 lines of up to 80 characters.
This file is a brief introduction to the data archive:
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Carole J. Hahn and Stephen G. Warren, 2007 (updated 2009): A GRIDDED CLIMATOLOGY OF CLOUDS
OVER LAND (1971-96) AND OCEAN (1954-97) FROM SURFACE OBSERVATIONS WORLDWIDE.
NDP-026E, Carbon Dioxide Information Analysis Center,
Oak Ridge National Laboratory, Oak Ridge, TN. (Documentation, 71 pages; plus
a 4-page appendix describing an update of ocean cloud averages for the years
1998-2008.) doi: 10.3334/CDIAC/cli.ndp026e
(Email to authors: sgw@atmos.washington.edu; hahn@atmo.arizona.edu.)
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NOTE: In August, 2010, this database was updated to contain ocean data
from 1998-2008. See the description of the update at the bottom of the file.
1. General Description of the Cloud Climatology Data Set
This archive provides a gridded climatology of clouds based on surface
synoptic weather reports which include cloud observations made visually
from land stations and ships at sea from locations around the globe. Cloud
averages formed from those observations are given on a 5-degree latitude-
longitude grid (or on a 10-degree grid for some ocean data), with land and
ocean data processed separately. Averages are given for total cloud cover,
clear-sky frequency, and nine cloud types from three levels of the troposphere
(high clouds, 3 middle cloud types, and 5 low cloud types). For each grid box,
this archive includes multi-year (1971-96 for land and 1954-97 for ocean)
annual, seasonal and monthly averages for day and night separately; analyses of
the first harmonic for the annual and diurnal cycles are also given. For the
ocean, seasonal averages for eight times per day and seasonal and monthly
averages by year are given for the grid boxes; for land, these latter quantities
were given for each of 5388 individual stations in the companion archive NDP-
026D. Cloud amounts and frequencies are given for all types, non-overlapped
amounts are provided for middle and high clouds, and mean base heights are
computed for low cloud types.
This archive supercedes our first climatology in this series (NDP-026). Our
analysis procedures have been improved and more years of data are used here.
Nighttime reports are now screened using the illuminance criterion of Hahn et
al. (1995); we distinguish more cloud types in the middle and low levels (we now
distinguish between As and Ac and between Sc, St and fog); and we imposed more
selection criteria on the stations and ships contributing.
These data and full documentation are available from:
Carbon Dioxide Information Analysis Center (CDIAC)
Oak Ridge National Laboratory
Post Office Box 2008
Oak Ridge, TN 37831-6335, U.S.A.
(http://cdiac.esd.ornl.gov/by_new/bynumber.html)
The documentation is also available online via
www.atmos.washington.edu/CloudMap/.
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2. Cloud Averages Contained in the Data Set
The cloud information contained in a synoptic weather report is listed in
Table 1 below. These quantities, along with the station/ship location and the
time of the report, are the basic data used to create this climatology.
Table 2 lists the cloud types analyzed for this climatology and provides their
definitions in terms of the synoptic code as defined by the World Meteorological
Organization and as modified in our cloud reports archive (NDP-026C) which was
the data archive used in the preparation of this climatology. Precipitation
codes are also given because they are used in our definitions of nimbostratus
and cumulonimbus cloud types. Note that we group all high clouds together in
this climatology; this is because preliminary analyses of the various cirriform
cloud types suggested that the assignment of high clouds among various sub-
species is not globally uniform.
The archive is divided into 52 File Categories; the divisions are based on the
content of the data. Table 4 (abbreviated from the full documentation), lists
the general contents of the categories.
These comments and tables provide a guide for the reader as to the makeup of
this data set. Details of the contents and formats for reading the data are
given in the full documentation (as well as the list of references cited here
and definitions of abbreviations used).
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TABLE 1. CLOUD INFORMATION CONTAINED IN SYNOPTIC WEATHER REPORTS
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Symbol Meaning Codes
________________________________________________________________
N total cloud cover 0-8 oktas
9= sky obscured
Nh lower cloud amount 0-8 oktas
h lower cloud base height 0-9
CL low cloud type 0-9
CM middle cloud type 0-9
CH high cloud type 0-9
ww present weather 00-99
Ix present weather indicator 1-6
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TABLE 2. CLOUD TYPE AND WEATHER TYPE DEFINITIONS USED
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Shorthand
Level notation Meaning Synoptic codes
________________________________________________________________________________
Tc total cloud cover N = 0-9
Cr completely clear sky N = 0
Ppt precipitation ww= 50-75,77,79,80-99
D drizzle 50-59
R rain 60-69
S snow 70-75,77,79
Ts thunderstorm or shower 80-99
Low CL=
Fo sky obscured by fog / with N=9 and
ww=10-12,40-49
St stratus 6,7
Sc stratocumulus 4,5,8
Cu cumulus 1,2
Cb cumulonimbus 3,9,
or N=9 with ww=Ts
LoL Fo + St + Sc + Cu + Cb
Mid CM=
Ns nimbostratus 2,7, or N=9 with ww=DRS
/ with ww=DRS and CL=0,7
/ with ww= RS and CL=4-8
As altostratus 1; 2 if not DRS
Ac altocumulus 3,4,5,6,8,9; 7 if not DRS
MiL Ns + As + Ac
High CH=
Hi cirriform clouds 1-9
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TABLE 4. DATA FILE CATEGORIES CONTAINED IN THE GRIDDED CLOUD ARCHIVE NDP-026E
________________________________________________________________________________
File Category General Contents
Number
------------- ----------------
GRID INFORMATION
1 GRID LAT, LON, LAND-FRACTION
& Number of land stations
-------------------------------------------------------------------------------
MULTI-YEAR AVERAGES
LAND DATA [5c]
2 Mean Annual Cloud AMOUNT
3 Mean Seasonal Cloud AMOUNT
4 Mean Seasonal Cloud FREQUENCY
5 Mean Seasonal AMOUNT-WHEN-PRESENT
6 Mean Seasonal Mid and Hi Cloud NON-OVERLAPPED AMOUNT
7 Mean Seasonal Low Cloud BASE HEIGHT
8 Mean Monthly Cloud AMOUNT
9 Mean Monthly Cloud FREQUENCY
10 Harmonics: ANNUAL; DIURNAL(Seasonally)
-------------------------------------------------------------------------------
11 LAND + OCEAN CLOUD AMOUNT [5c], Annual and Seasonal Averages
-------------------------------------------------------------------------------
OCEAN DATA [5c and/or 10r]
12 Mean Annual Cloud AMOUNT
13 Mean Seasonal Cloud AMOUNT
14 Mean Seasonal Cloud FREQUENCY
15 Mean Seasonal AMOUNT-WHEN-PRESENT
16 Mean Seasonal Mid, Hi Cloud NON-OVERLAPPED AMOUNT
17 Mean Seasonal Low Cloud BASE HEIGHT
18 Mean Monthly Cloud AMOUNT
19 Mean Monthly Cloud FREQUENCY
-------------------------------------------------------------------------------
by Synoptic Hour*:
20 Mean Seasonal Cloud AMOUNT
21 Mean Seasonal Cloud FREQUENCY
22 Mean Seasonal Mid, Hi Cloud NON-OVERLAPPED AMOUNT
23 Mean Seasonal Low Cloud BASE HEIGHT
24 Harmonics: ANNUAL; DIURNAL(Seasonally)
-------------------------------------------------------------------------------
INDIVIDUAL-YEAR AVERAGES, OCEAN DATA*:
25 Seasonal Mean Cloud AMT, DJF
26 Seasonal Mean Cloud AMT, MAM
27 Seasonal Mean Cloud AMT, JJA
28 Seasonal Mean Cloud AMT, SON
29 Seasonal Mean Cloud FQ, DJF
30 Seasonal Mean Cloud FQ, MAM
31 Seasonal Mean Cloud FQ, JJA
32 Seasonal Mean Cloud FQ, SON
33 Seasonal Mean Mid,Hi NOL, DJF
34 Seasonal Mean Mid,Hi NOL, MAM
35 Seasonal Mean Mid,Hi NOL, JJA
36 Seasonal Mean Mid,Hi NOL, SON
37 Seasonal Mean Low Base HGT, DJF
38 Seasonal Mean Low Base HGT, MAM
39 Seasonal Mean Low Base HGT, JJA
40 Seasonal Mean Low Base HGT, SON
-------------------------------------------------------------------------------
41 OMYD Monthly Day AMT, FQ, AWP JAN
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52 OMYD Monthly Day AMT, FQ, AWP DEC
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INDIVIDUAL-YEAR AVERAGES, OCEAN DATA (update years 1998-2008):
55 Seasonal Mean Cloud AMT, DJF
56 Seasonal Mean Cloud AMT, MAM
57 Seasonal Mean Cloud AMT, JJA
58 Seasonal Mean Cloud AMT, SON
59 Seasonal Mean Cloud FQ, DJF
60 Seasonal Mean Cloud FQ, MAM
61 Seasonal Mean Cloud FQ, JJA
62 Seasonal Mean Cloud FQ, SON
63 Seasonal Mean Mid,Hi NOL, DJF
64 Seasonal Mean Mid,Hi NOL, MAM
65 Seasonal Mean Mid,Hi NOL, JJA
66 Seasonal Mean Mid,Hi NOL, SON
67 Seasonal Mean Low Base HGT, DJF
68 Seasonal Mean Low Base HGT, MAM
69 Seasonal Mean Low Base HGT, JJA
70 Seasonal Mean Low Base HGT, SON
-------------------------------------------------------------------------------
71 OMYD Monthly Day AMT, FQ, AWP JAN
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72 OMYD Monthly Day AMT, FQ, AWP DEC
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* For land data see NDP-026D.
*
END__README.NDP-026E_*********-*********-*********-*********-*********-*********
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