File: get_srbavg1_1deg_reg_monthly.README 1.0 Introduction This readme file document provides information on how to extract the 1-degree regional monthly average top of the atmosphere (TOA) fluxes from the Clouds and Earth's Radiant Energy System (CERES) SRBAVG1 HDF data sets. The entire CERES SRBAVG1 data set contain 314 HDF Science Data Sets (SDS). The 1-degree regional monthly average TOA geo and non-geo fluxes are contained in 20 of these 314 SDS. The CERES SRBAVG1 data set is part of the larger CERES SRBAVG data set, which also contain SRBAVG2 and SRBAVG3 data sets. Additional information on the CERES SRBAVG data set can be found at http://eosweb.larc.nasa.gov/GUIDE/dataset_documents/cer_srbavg.html This document includes the following sections: Section 2.0 - Script read package contents Section 3.0 - Description Section 4.0 - Script usage Section 5.0 - Advantage of using this script Section 6.0 - Flat binary file format Section 7.0 - GrADS control file Section 8.0 - Examples global gifs images from GrADS Section 9.0 - FORTRAN/C read programs Section 10.0 - CERES 1-degree equal-angle grid system If users have questions, please contact the Langley ASDC User and Data Services Office at: Atmospheric Science Data Center User and Data Services Office Mail Stop 157D NASA Langley Research Center Hampton, Virginia 23681-2199 U.S.A. E-mail: support-asdc@earthdata.nasa.gov Phone: (757)864-8656 FAX: (757)864-8807 URL: http://eosweb.larc.nasa.gov 2.0 Sample Read Package Contents This package consists of the following files: 1) get_srbavg1_1deg_reg_monthly_geo* 2) get_srbavg1_1deg_reg_monthly_nongeo* 3) read_srbavg1_1deg_reg_monthly.c 4) read_srbavg1_1deg_reg_monthly.f 5) srbavg1_nongeo_clw.gif 6) srbavg1_nongeo_cnet.gif 7) srbavg1_nongeo_csw.gif 8) srbavg1_nongeo_tlw.gif 9) srbavg1_nongeo_tnet.gif 10) srbavg1_nongeo_tsw.gif 11) tnongeo.ctl 3.0 Description "get_srbavg1_1deg_reg_monthly_geo" and "get_srbavg1_1deg_reg_monthly_nongeo" are csh scripts that use standard HDF4 "hdp" utility and standard Unix "split" and "cat" commands to extract global map of CERES SRBAVG1 1-degree regional monthly average top of the atmosphere (TOA) geo and non-geo fluxes from the standard CERES SRBAVG1 HDF data file. The output is a flat binary file (IEEE 32-bit unformated binary data with no header) that contains geo output parameters from "get_srbavg1_1deg_reg_monthly_geo": 1) global map of geo TOA total sky outgoing longwave flux 2) global map of geo TOA total sky reflected shortwave flux 3) global map of geo TOA total sky net downward flux 4) global map of geo TOA total sky shortwave albedo 5) global map of geo TOA total sky outgoing window flux 6) global map of geo TOA clear sky outgoing longwave flux 7) global map of geo TOA clear sky reflected shortwave flux 8) global map of geo TOA clear sky net downward flux 9) global map of geo TOA clear sky shortwave albedo 10) global map of geo TOA clear sky outgoing window flux non-geo output parameters from "get_srbavg1_1deg_reg_monthly_nongeo": 1) global map of non-geo TOA total sky outgoing longwave flux 2) global map of non-geo TOA total sky reflected shortwave flux 3) global map of non-geo TOA total sky net downward flux 4) global map of non-geo TOA total sky shortwave albedo 5) global map of non-geo TOA total sky outgoing window flux 6) global map of non-geo TOA clear sky outgoing longwave flux 7) global map of non-geo TOA clear sky reflected shortwave flux 8) global map of non-geo TOA clear sky net downward flux 9) global map of non-geo TOA clear sky shortwave albedo 10) global map of non-geo TOA clear sky outgoing window flux The albedo is unitless and is in fraction. The fluxes are real number and is in unit of watts per squared meter. A value of 3.40282e+38 represents missing or no data for the gridbox. This flat binary file can be display using GrADS software with the supplied GrADS control file. A fortran read program is also provided to read the flat binary file. The pre-build binary of the HDF4 "hdp" utility can be obtained through the HDF4 website at http://hdf.ncsa.uiuc.edu/release4/obtain.html 4.0 Script usage geo: To use the script, just type the following at the Unix command line > get_srbavg1_1deg_reg_monthly_geo where is the name of the CERES SRBAVG1 file is the name of the flat binary file Here is an example for extracting CERES SRBAVG1 Terra FM1 Edition2D monthly average 1-degree non-geo fluxes for January 2001 into a flat binary file > get_srbavg1_1deg_reg_monthly_geo CER_SRBAVG1_Terra-FM1-MODIS_Edition2D_013023.200101 tgeo.grd non-geo: To use the script, just type the following at the Unix command line > get_srbavg1_1deg_reg_monthly_nongeo where is the name of the CERES SRBAVG1 file is the name of the flat binary file Here is an example for extracting CERES SRBAVG1 Terra FM1 Edition2C monthly average 1-degree non-geo fluxes for February 2003 into a flat binary file > get_srbavg1_1deg_reg_monthly_nongeo CER_SRBAVG1_Terra-FM1-MODIS_Edition2C_013023.200302 tnongeo.grd 5.0 Advantage of using this script a) Doesn't require special commercial softwares to read the CERES SRVAVG1 HDF data. b) Reduces data volume from 200 Mbytes/month (SRBAVG1 HDF file) to 2.6 Mbytes/month (flat binary file); that is a 98% saving in storage space. c) Can instantly view global map of CERES data using GrADS (a free data analysis and visualization software) d) FORTRAN and C read software is provided for easy access of the extracted binary data. e) Reduces time spent dealing with HDF data --> more time for doing real science. f) Can be converted to netcdf file format using grads to netcdf converter (available at NOAA/GFDL website) 6.0 Flat binary file format The flat binary data is stored in FORTRAN direct access unformatted binary form. So it can be opened by both FORTRAN and C program. The data file generated on a big endian machine will be in big endian format (Most Unix vendors). The data file generated on a little endian machine will be in little endian format (Intel/AMD based PCs/workstations or Compaq Alpa based systems). Byte swapping is only required if work is done between the big endian and little endian systems. There are 64800 grid points in the horizontal domain and 10 variables for each monthly file. Each physical parameter is stored in the data file as a 4-bytes real value. The fortran record length for the data file are 360*180 4-bytes words long or 360*180*4 bytes long (depending on your fortran compiler, it may need the 4-bytes word or the byte value, check your compiler for detail). A value of 3.40282e+38 represents missing or no data for the gridbox. This data format is comparable with the GrADS system. If you don't have GrADS, you can download the exec and the font files directly from GrADS Website. GrADS homepage is http://grads.iges.org/grads/head.html GrADS is highly recommanded but it is not required to use this data. A fortran program is provided for user to read the data. 7.0 GrADS control file GrADS control file is used by GrADS system to describe the contents of the flat binary file. tnongeo.ctl ---> Example of GrADS control file for viewing extracted CERES Terra FM1 SRVAVG1 Edition2C data for February 2003. 8.0 Examples global gifs images from GrADS The followings are the global images of monthly average TOA non-geo fluxes extracted from CERES Terra FM1 SRBAVG1 Edition2C data for February 2003 Total sky fluxes: srbavg1_nongeo_tlw.gif, srbavg1_nongeo_tsw.gif, srbavg1_nongeo_tnet.gif Clear sky fluxes: srbavg1_nongeo_clw.gif, srbavg1_nongeo_csw.gif, srbavg1_nongeo_cnet.gif 9.0 FORTRAN/C read programs read_srbavg1_1deg_reg_monthly.f --> FORTRAN77 program to read the flat binary file read_srbavg1_1deg_reg_monthly.c --> C program to read the flat binary file NOTE: FORTRAN compilers may assume 4 byte words when defining record lengths. If an error occurs while reading the input file "tnongeo.grd", in the input file open statements, remove the "*4" to make recl=360*180. 10.0 CERES 1-degree equal-angle grid system 1.0 degree ---> 360 longitude zones by 180 latitude zones; It starts at North pole and Dateline and goes east and south from there. Here is a map of the grid; each grid is a 1.0 degree longitude by 1.0 degree latitude box centered at these locations (1,1) (2,1) ............ (360,1) (89.5N,-179.5E) (89.5N,-178.5E) (89.5N,179.5E) (1,2) (2,2) ............ (360,2) (88.5N,-179.5E) (88.5N,-178.5E) (88.5N,179.5E) ........................................... ........................................... (1,180) (2,180) .......... (360,180) (89.5S,-179.5E) (89.5S,-178.5E) (89.5S,179.5E) Updated: July 31, 2006 April 17, 2012 (ASDC email changed) -----------------------------------------------------------------------------