SRB_SW_LW_MONTHLY Readme 1.0 Introduction This file contains information about the Langley Eight-Year Shortwave and Longwave Surface Radiation Budget (SRB) Dataset sample read software and data files. The 8-Year SRB data set available through the Langley Distributed Active Archive Center (DAAC) is: SRB_SW_LW_MONTHLY Each data granule contains grid information, and monthly average shortwave and longwave surface radiation budget information and associated meteorological data. All 8-year SRB data files are stored in ASCII and can be read with the DAAC-provided read software. Additional information about the 8-year SRB data sets can be found in the SRB project and data set Guide documents at the Langley DAAC: http://eosweb.larc.nasa.gov Images of data from the 8-year SRB data files and other project information can be viewed at http://srb-swlw.larc.nasa.gov/ This Readme file includes five other sections: Section 2.0 - describes the available read software. Section 3.0 - discusses how to create an executable program from read software source code. Section 4.0 - demonstrates how to invoke the executable program. Section 5.0 - provides general information for the data set. Section 6.0 - provides more detailed implementation notes. If there are questions about using the 8-year SRB sample read software, please contact the Langley User and Data Services (UDS) office. The UDS may be reached by E-Mail: larc@eos.nasa.gov, by telephone at (757)864-8656, or by FAX at (757)864-8807. The UDS mailing address is: Langley DAAC User and Data Services Office NASA Langley Research Center Mail Stop 157D, 2 S. Wright St. Hampton, VA 23681-2199 USA 2.0 Read Software Files Currently, there is one sample read program which works with the 8-Year SRB data set, read_srb_sw_lw_monthly.f. It is written in Fortran 77. This program has been tested on the following computers and operating systems: Computer Operating System ------------------- ---------------- Sun Sparc Solaris 2.6 SGI Origin 2000 IRIX 6.4 HP 9000/735 HP-UX 10.10 DEC Alpha Digital UNIX 4.0A This program is written as an example of how to read in the SRB data. As delivered, it reads in and writes to the screen the sample data for a given gridbox. 3.0 Creating Executable Program Files 3.1 Create with f77 compiler To compile the program, use the command for the Fortran 77 compiler. The command may vary slightly among operating systems. On most systems the command is: % f77 -o read_srb read_srb_sw_lw_monthly.f If the appropriate compile command is not found on your system, check to be sure that your PATH environment variable includes the directory that contains the compiler or specify the entire path to the compiler in your command. This compile command creates an executable program file named read_srb. 4.0 Invoking Read Software 4.1 Running the executable version of the 8-year SRB Read Program This program assumes that it is being run in the directory that contains the data files. If not, then the format for the input filename must be modified to include the entire directory path (format 200). To execute the 8-year SRB read program: read_srb The user is prompted by the program to enter the month and year of interest and the gridbox of interest. A sample of the interactive program execution is provided in Section 6.0. 5.0 Data Set Information This section provides information for the 8-year SRB data set on-line at the Langley DAAC. This data set information was obtained from the data files, SRB documents, or directly from the data producer/provider. High-level data set descriptions, variable definitions, and contact information are given for each data set. 5.1 SRB_SW_LW_MONTHLY Data Set This data set is written in ASCII. LONG NAME FOR THIS DATA SET: Langley Eight-Year Shortwave and Longwave Surface Radiation Budget Dataset FILE NAMING CONVENTION: The 8-year SRB data granules are prefixed with "srb_sw_lw_" to indicate they belong to this data set and contain both shortwave and longwave SRB information. This prefix also distinguishes this dataset from a similar one at the LaRC DAAC (SRB_MONTHLY, granule prefix srb_monavgs). The SRB_MONTHLY dataset contains only shortwave SRB. A six digit designation follows the prefix and it indicates the year and month of data. Here is an example filename: srb_sw_lw_198610 October 1986 monthly average shortwave and longwave surface radiation budget data. DATA GRID: The SRB data are given on an equal-area grid containing 6596 grid cells covering the globe. This grid is the same as that used by the International Satellite Cloud Climatology Project (ISCCP). The grid is defined by the area of a 2.5 deg. latitude x 2.5 deg. longitude cell at the equator; the intersection of the Greenwich meridian and the equator is a cell corner. The first grid cell corner is located at -90S latitude, 0 longitude. All map cells are determined by a constant 2.5 deg. increment in latitude and a variable longitude increment. The longitude increment is an integer number of cells in a latitude zone. There are 3 grid cells at the North and South Poles and 144 at the equator. To learn more about this grid, download the DX/D1/D2 New Cloud Data Documentation from the following web site: http://isccp.giss.nasa.gov/documents.html VARIABLES: There are 21 variables for each gridbox and 6596 gridboxes covering the globe in each file. The dataset contains variables related to the grid, monthly average shortwave and longwave surface radiation parameters and monthly average meteorological parameters. These parameters are listed in order of appearance across each row of data. REGION - equal-area grid box numbering scheme starting at the South Pole and Greenwich, increasing eastward and northward. LATITUDE INDEX - latitude index starting at the South Pole, increasing northward. LONGITUDE INDEX - longitude index starting at Greenwich, increasing eastward. The number of longitudinal cells per band is dependent upon the latitude. There are 3 at the poles and 144 at the equator. CENTRAL LATITUDE - latitude of the center of the grid box. CENTRAL LONGITUDE - longitude of the center of the grid box. CLOUD AMOUNT - monthly average cloud amount (percent) TOTAL WATER VAPOR BURDEN - monthly average ISCCP-C1/TOVS reported water vapor burden (kg/m**2) summed over the 5 layers. SURFACE TEMPERATURE - monthly average ISCCP-C1 clear-sky composite surface temperature (K). SNOW/ICE AMOUNT - ISCCP-C1 snow/ice amount (percent), except where the average surface temperature was greater than 285 DEG K over a 5-day period. When this condition was met, it was assumed that the snow/ice cover had melted and the snow/ice amount was set to zero. SURFACE ALBEDO - monthly average fraction of downward shortwave flux that is reflected by the surface (dimensionless). TOP-OF-ATMOSPHERE DOWNWARD SHORTWAVE FLUX - monthly average shortwave (solar) radiation (flux density in W/m**2) received at the top-of-atmosphere. CLEAR-SKY DOWNWARD SHORTWAVE FLUX - monthly average shortwave (solar) radiation (flux density in W/m**2) reaching the surface if no clouds were present. ALL-SKY DOWNWARD SHORTWAVE FLUX (insolation) - monthly average shortwave radiation (flux density in W/m**2) reaching the surface. ALL-SKY NET SHORTWAVE FLUX (absorbed) - monthly average shortwave radiation (flux density in W/m**2) absorbed by the surface. SHORTWAVE CLOUD FORCING - change in the amount of shortwave flux reaching the surface due to the presence of clouds (W/m**2). CLEAR-SKY DOWNWARD LONGWAVE FLUX - monthly average longwave (atmospheric) radiation (flux density in W/m**2) reaching the surface if no clouds were present. ALL-SKY DOWNWARD LONGWAVE FLUX - monthly average longwave radiation (flux density in W/m**2) reaching the surface. ALL-SKY NET LONGWAVE FLUX - monthly average longwave radiation (flux density in W/m**2) absorbed by the surface. LONGWAVE CLOUD FORCING - change in the amount of longwave flux reaching the surface due to the presence of clouds (W/m**2). TOTAL NET FLUX - monthly average total radiation (shortwave + longwave) (flux density in W/m**2) absorbed by the surface. TOTAL CLOUD FORCING - change in the amount of total flux (shortwave + longwave) reaching the surface due to the presence of clouds (W/m**2). CONTACTS FOR DATA PRODUCT INFORMATION: Dr. Shashi Gupta Analytical Services and Materials, Inc. One Enterprise Parkway, Suite 300 Hampton, VA 23666-5845 USA E-mail : s.k.gupta@larc.nasa.gov Phone: (757) 827-4621 Fax: (757) 825-8659 Dr. Paul W. Stackhouse, Jr. NASA Langley Research Center MS 420, 21 Langley Boulevard Hampton, VA 23681-1379 USA E-mail: p.w.stackhouse@larc.nasa.gov Phone: 757-864-5368 Fax: 757-864-7996 6.0 Implementation Notes This section gives a brief explanation of how to run the sample read software. 6.1 read_srb_sw_lw_monthly f77 Program The read_srb_sw_lw_monthly f77 program can be used to read any of the 8-year SRB data files. The following is a sample session showing compilation and execution of the program on the machine named spell. spell 2: f77 -o read_srb read_srb_sw_lw_monthly.f read_srb.f: MAIN read_srb: spell 3: read_srb Enter month (1-12) and year (1983-1991) of data (EX. for Sept. 1988 ENTER 9 1988): 5 1990 Enter gridbox of interest (1-6596): 3232 You want to read May 1990 and print data for grid box 3232 Granule name: srb_sw_lw_199005 region = 3232 central latitude and longitude = -1.25 193.75 clear-sky shortwave flux = 284.71 all-sky shortwave flux = 268.37 clear-sky longwave flux = 413.11 all-sky longwave flux = 440.67 cloud percent = 58.80 surface albedo = .06 snow/ice percent = .00