START_README.NDP-026E*****2007_Nov*****_*********-*********-*********-*********- This file contains 198 lines of up to 80 characters. This file is a brief introduction to the data archive: * Carole J. Hahn and Stephen G. Warren, 2007: 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. doi: 10.3334/CDIAC/cli.ndp026e (Email to authors: sgw@atmos.washington.edu; hahn@atmo.arizona.edu.) - 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/. - 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). - *********-*********-*********-*********-*********-*********-*********-*********- TABLE 1. CLOUD INFORMATION CONTAINED IN SYNOPTIC WEATHER REPORTS ________________________________________________________________ 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 ________________________________________________________________ - *********-*********-*********-*********-*********-*********-*********-*********- TABLE 2. CLOUD TYPE AND WEATHER TYPE DEFINITIONS USED ________________________________________________________________________________ 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 ________________________________________________________________________________ - *********-*********-*********-*********-*********-*********-*********-*********- 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 | | 52 OMYD Monthly Day AMT, FQ, AWP DEC ________________________________________________________________________________ * For land data see NDP-026D. * END__README.NDP-026E_*********-*********-*********-*********-*********-*********