SRB_REL2.1_LW_3HRLY - GEWEX Longwave Cloud Properties 3-Hourly Data set README File 1.0 Introduction This README file provides information on the SRB_REL2.1_LONGWAVE_CLOUDPROPS_3HRLY data set. This data set provides 3-hourly global fields of 53 surface and cloud properties that serve as inputs to the GEWEX longwave algorithm (GLW). If users have questions, please contact the Langley Atmospheric Sciences Data Center (ASDC) Science, Users and Data Services Office at: Atmospheric Sciences Data Center Science, Users and Data Services Office Mail Stop 157D 2 South Wright Street NASA Langley Research Center Hampton, Virginia 23681-2199 U.S.A. E-mail: larc@eos.nasa.gov Phone: (757)864-8656 FAX: (757)864-8807 URL: http://eosweb.larc.nasa.gov This readme includes the following sections: 1.0 Introduction 2.0 Data Set Description 2.1 Data Quality 2.1.2. Indian Ocean Gap Artifact 2.2 Input Data 2.3 Grid Description 2.4 Points of Contact 3.0 Format and Packaging 4.0 Science Parameters Information 5.0 Description of Sample Read Software 6.0 Implementing the Sample Read Software 7.0 Sample Output 2.0 Data Set Description These 53 parameters fall into 14 classes; there are multiple parameters in some classes as listed below: 1. GLW Skin Temperature (glw_skint) 2. GEOS Skin Temperature (geos_skint) 3. ISCCP Skin Temperature (isccp_skint) 4. Precipitable Water (prec_water) 5. Snow/Ice Percentage (snow) 6. Day/Night flag (daynite; 1=Day, 0=Night) 7-18. 12 Bands of IR surface emissivity (emis) 7. band 1: 4.5 - 5.3 um 8. band 2: 5.3 - 5.9 um 9. band 3: 5.9 - 7.1 um 10. band 4: 7.1 - 8.0 um 11. band 5: 8.0 - 9.1 um 12. band 6: 9.1 - 10.2 um 13. band 7: 10.2 - 12.5 um 14. band 8: 12.5 - 14.9 um 15. band 9: 14.9 - 18.5 um 16. band 10: 18.5 - 25.0 um 17. band 11: 25.0 - 35.7 um 18. band 12: 35.7 - oo um 19-23. Cloud Fraction for 5 cloud types (cld_frac) 19. high ice 20. mid-level ice 21. mid-level water 22. low-level ice 23. low-level water 24-28. Cloud Visible Optical Depth for 5 cloud types (cld_tau) 24. high ice 25. mid-level ice 26. mid-level water 27. low-level ice 28. low-level water 29-33. Cloud particle size for 5 cloud types (cre) (droplet radius for water clouds; effective diameter for ice clouds) 29. high ice 30. mid-level ice 31. mid-level water 32. low-level ice 33. low-level water 34-38. Cloud Top Temperature for 5 cloud types (cld_top_temp) 34. high ice 35. mid-level ice 36. mid-level water 37. low-level ice 38. low-level water 39-43. Cloud Top Pressure for 5 cloud types (cld_top_pres) 39. high ice 40. mid-level ice 41. mid-level water 42. low-level ice 43. low-level water 44-48. Cloud Base Pressure for 5 cloud types (cld_base_pres) 44. high ice 45. mid-level ice 46. mid-level water 47. low-level ice 48. low-level water 49-53. Cloud Water or Ice Content for 5 cloud types (cld_water_cnt) 49. high ice 50. mid-level ice 51. mid-level water 52. low-level ice 53. low-level water These parameters are derived on a 3-hourly temporal resolution (i.e., a global instantaneous gridded field every 3 hours). The 8 3-hourly times per day are UT hours: 00, 03, 06, 09, 12, 15, 18, and 21. The current version of the data sets is identified as Release 2.1. The sources for these inputs are briefly described below. Please contact Dr. Paul W. Stackhouse Jr. at the address below for further details. 2.1 Data Quality The authors have not done any independent validation of the parameters provided in these files. The purpose in providing these data is to enable the users to make flux computations on their own using any algorithms (including the one used in our work), if they so desire. To get an assessment of the quality, the users should refer to the original sources of these data. 2.1.2. Indian Ocean Gap Artifact There is a visible and common artifact in much of the data set period, due to a lack of coverage from geostationary satellites over an area centered on 70 degrees east longitude. This situation , commonly called the Indian Ocean gap, occurs for all of the July 1983 - June 1998 time period, except for April 1988 - March 1989, when data from the INSAT satellite is available to cover the gap. In July of 1998, Meteosat-5 was moved over the gap area, eliminating the gap. When the Indian Ocean gap occurs, the gap area is covered by polar orbiting satellites, which can result in only one or two daytime overpasses per day. Geosynchronous temporal sampling during the daytime is 3-5 times per daytime depending upon the latitude (between 55 degrees North and South) and the time or year. In addition, the limbs of the geostationary satellites which bound the gap may suffer from spuriously high cloud amounts, due to large view angles. This results in an abrupt drop-off of cloud fraction in the gap as compared to the gap boundary. 2.2 Input Data Inputs to the algorithm were obtained from the following sources: Cloud parameters were derived from the DX data of the International Satellite Cloud Climatology Project (ISCCP; Rossow and Schiffer, 1999, BAMS, 80, 2261-2287). The cloud pixels were separated into categories of high, middle and low clouds where middle and low clouds could be composed of ice or water. Cloud fractions and cloud optical depths were determined within these categories. Cloud particle sizes were assumed and cloud physical thicknesses were also derived based upon information from literature. Temperature and moisture profiles were taken from a 4-D assimilation product provided by the Global Modeling and Assimilation Office (GMAO) at NASA GSFC and were produced with the Goddard Earth Observing System model version 1 (GEOS-1). Surface emissivities were taken from a map developed at NASA LaRC (Wilber et al. 1999, NASA/TP-1999-209362, 35 pp.). 2.3 Grid Description The properties are generated on a nested grid, which contains 44016 cells. The grid has a resolution of 1 degree latitude globally, and longitudinal resolution ranging from 1 degree in the tropics and subtropics to 120 degrees at the poles. The first cell is Latitude 89-90 degrees South, Longitude 0-120 degrees East. The cells start at the Greenwich meridian and proceed east around the globe, then shift one degree to the north. The number of cells per latitude band starting at the South Pole are: 3, 45, 45, 45, 45, 45, 45, 45, 45, 45, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 360, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 45, 45, 45, 45, 45, 45, 45, 45, 45, 3 The read software described below contains a subroutine to regrid the fluxes to 1 degree latitude by 1 degree longitude grid using replication. 2.4 Points of Contact Scientific contact: Dr. Paul W. Stackhouse Jr. Mail Stop 420 21 Langley Boulevard NASA Langley Research Center Hampton, VA 23681-2199 U.S.A. E-mail: p.w.stackhouse@larc.nasa.gov Production Contact: Atmospheric Sciences Data Center Science, Users and Data Services Office Mail Stop 157D 2 South Wright Street NASA Langley Research Center Hampton, VA 23681-2199 U.S.A. Other Contacts: None 3.0 Format and Packaging These data are provided as daily files each of which contains 3-hourly global fields of the 53 parameters described in Section 4.0 on an approximately 1 deg x 1 deg equal-area grid described in Section 2.3. The files are contain binary data and are named according to the following convention: srb_rel2.1_longwave_cldprops_3hrly_yyyymmdd.binary, where srb Project name, Surface Radiation Budget rel2.1 Release number for these data (Release 2.1) longwave Name of the algorithm, GEWEX Longwave cldprops Denotes cloud properties 3hrly Time resolution of the data set yyyy 4-digit year for these data mm 2-digit month for these data dd 2-digit day for these data binary file format 4.0 Science Parameters Information The files contain global fields of 3-hourly values of the 53 parameters on the nested grid. Each files has 424 (53x8) records; 53 records for each 3-hourly time (00, 03, 06, 09, 12, 15, 18, and 21 UT). Notes: Parameters in the same classes are described together in the list below. The values in the cloud particle size fields represent droplet radius for water clouds and effective particle diameter for ice clouds. Name: GLW Skin Temperature Units: Kelvin Type: real Range: 175-375 Fill Values: -999.00 Scale Factor: None Name: GEOS-1 Skin Temperature Units: Kelvin Type: real Range: 175-375 Fill Values: -999.00 Scale Factor: None Name: ISCCP Skin Temperature Units: Kelvin Type: real Range: 175-375 Fill Values: -999.00 Scale Factor: None Name: Precipitable Water (pw) Units: grams per square centimeter Type: real Range: 0-10 Fill Values: -999.00 Scale Factor: None Name: Snow/Ice Percentage Units: % Type: real Range: 0.0 - 100.0 Fill Values: -999.0 Scale Factor: None Name: Day/Night flag (Day=1, Night=0) Units: none Type: real Range: 0.0 or 1.0 Fill Values: n/a Scale Factor: None Name: IR Surface Emissivity (12 fields) Units: none Type: real Range: 0.0-1.0 Fill Values: -999. Scale Factor: None Name: Cloud Fraction (5 fields) Units: none Type: real Range: 0.0-1.0 Fill Values: -999.0 Scale Factor: None Name: Cloud Visible Optical Depth (5 fields) Units: none Type: real Range: 0-200 Fill Values: -999.0 Scale Factor: None Name: Cloud particle size (5 fields) Units: micrometer Type: real Range: 0-100 Fill Values: -999.0 Scale Factor: None Name: Cloud Top Temperature (5 fields) Units: Kelvin Type: real Range: 150-350 Fill Values: -999.0 Scale Factor: None Name. Cloud Top Pressure (5 fields) Units: hectopascals Type: real Range: 1000-100 Fill Values: -999.0 Scale Factor: None Name. Cloud Base Pressure (5 fields) Units: hectopascals Type: real Range: 1000-100 Fill Values: -999.0 Scale Factor: None Name. Cloud Water or Ice Content (5 fields) Units: grams per cubic meter Type: real Range: 0-10 Fill Values: -999.0 Scale Factor: None 5.0 Description of Sample Read Software Sample read software written in Fortran-90, read_longwave_cloudprops_3hrly.f90, was developed for reading these data. This software constitutes the name of the input data file, accesses and reads it, using the information provided in the namelist file (longwave_cloudprops_3hrly.nml). The input files are read as direct-access fortran binary on the nested (44016 box) grid. The software reads one or more of the parameter fields, regrids them to an equal-angle 1 deg x 1 deg grid, and writes them output as ascii or binary format. The choice of file format (ascii or binary) and of the location of the output files is also made through the namelist file. A sample namelist file that would be used to read the July 24, 1995 data file and write all parameters to an ascii format output file is presented below. Note that only 14 of the 53 parameters are written to the output. Only one out of 12 emissivity values (band 10) are written out. Similarly, only one cloud type (#5; low water cloud) is chosen for all cloud parameters. These choices are made by using "band=10" and "cld=5" in the namelist file. &time_vars year=1992 month=7 day=01 ascii=.true. binary=.false. path_in='**** input file path here****' path_out='**** output file path here****' little_endian=.false. glw_skint=.true. geos_skint=.true. isccp_skint=.true. prec_water=.true. snow=.true. daynite=.true. emis=.true. band=10 cld=5 cld_frac=.true. cld_tau=.true. cre=.true. cld_top_temp=.true. cld_top_pres=.true. cld_base_pres=.true. cld_water_cnt=.true. / There is a choice to convert the input fields from big endian to little endian byte order with the logical variable "little_endian" in the namelist. This applies to operating systems where byte order is stored opposite that of the Sun and SGI machines used to create the data set, such as Linux. If possible, a better choice for doing the conversion in these cases would be to use a compiler option. If using a compiler option, do not set little_endian to true. Both, input and output fields have the same orientation: they start at the Greenwich meridian-south pole and go east and north from there. A limitation of this code is that it provides a complete global field of the specified parameters in the above orientation. The user should be easily able to extract values for any box or lat-lon region from these fields. 6.0 Implementing the Sample Read Software The sample read software can be compiled with any Fortran 90 or 95 compiler. To compile: % f90 -o run_cldprops_3hrly read_longwave_cloudprops_3hrly.f90 The providers used a NAG F95 compiler but any F90/F95 compiler should work. Edit the namelist file to select month and year to be processed, choose the parameters to be read and the format of the output file. Run the software: % run_cldprops_3hrly 7.0 Sample Output The 14 tables of numbers below show the values of the 14 parameters selected above from these files for latitude bands 45-51 (starting at the south pole) and longitude boxes 100-104 (starting at the Greenwich meridian) for hour 06 of day 24 of the month. Values for only a small lat-lon box for a single time are printed to the screen. When the is code run, the following information appears on the screen: ***************************************************************** * * * * * Data Set longwave_cldprops_3hrly Read Software * * * * Version: 1.0 * * * * Date: August 5, 2004 * * * * Contact: Atmospheric Sciences Data Center * * Science, Users and Data Services Office * * Mail Stop 157D * * 2 South Wright Street * * NASA Langley Research Center * * Hampton, Virginia 23681-2199 * * U.S.A. * * * * E-mail: larc@eos.nasa.gov * * Phone: (757)864-8656 * * FAX: (757)864-8807 * * * ***************************************************************** Variable glw_skint_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 281.991 282.186 282.186 282.315 282.315 lat band # 46 283.025 283.108 283.148 283.188 283.226 lat band # 47 283.721 283.768 283.775 283.781 283.807 lat band # 48 284.146 284.135 284.100 284.064 284.090 lat band # 49 284.481 284.451 284.416 284.381 284.421 lat band # 50 284.726 284.716 284.724 284.732 284.800 lat band # 51 285.173 285.199 285.254 285.309 285.380 file /glw_skint_3hrly_19950724.binary has been written Variable geos_skint_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 281.991 282.186 282.186 282.315 282.315 lat band # 46 283.025 283.108 283.148 283.188 283.226 lat band # 47 283.721 283.768 283.775 283.781 283.807 lat band # 48 284.146 284.135 284.100 284.064 284.090 lat band # 49 284.481 284.451 284.416 284.381 284.421 lat band # 50 284.726 284.716 284.724 284.732 284.800 lat band # 51 285.173 285.199 285.254 285.309 285.380 file /geos_skint_3hrly_19950724.binary has been written Variable isccp_skint_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 275.439 275.960 275.960 276.362 276.362 lat band # 46 276.764 -999.000 -999.000 -999.000 -999.000 lat band # 47 280.180 280.515 -999.000 -999.000 277.367 lat band # 48 277.919 280.431 280.180 280.180 276.262 lat band # 49 -999.000 276.764 279.879 281.185 276.764 lat band # 50 276.262 281.185 279.326 281.397 278.472 lat band # 51 278.472 277.367 280.180 279.577 281.285 file /isccp_skint_3hrly_19950724.binary has been written Variable prec_water_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 1.367 1.009 1.009 0.798 0.798 lat band # 46 1.292 1.116 0.998 0.880 0.858 lat band # 47 1.332 1.167 1.064 0.961 0.938 lat band # 48 1.375 1.227 1.140 1.053 1.029 lat band # 49 1.397 1.266 1.193 1.120 1.098 lat band # 50 1.398 1.286 1.223 1.160 1.144 lat band # 51 1.379 1.281 1.226 1.171 1.169 file /prec_water_3hrly_19950724.binary has been written Variable snow_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 0.000 0.000 0.000 0.000 0.000 lat band # 46 0.000 0.000 0.000 0.000 0.000 lat band # 47 0.000 0.000 0.000 0.000 0.000 lat band # 48 0.000 0.000 0.000 0.000 0.000 lat band # 49 0.000 0.000 0.000 0.000 0.000 lat band # 50 0.000 0.000 0.000 0.000 0.000 lat band # 51 0.000 0.000 0.000 0.000 0.000 file /snow_3hrly_19950724.binary has been written Variable daynite_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 1.000 1.000 1.000 1.000 1.000 lat band # 46 1.000 1.000 1.000 1.000 1.000 lat band # 47 1.000 1.000 1.000 1.000 1.000 lat band # 48 1.000 1.000 1.000 1.000 1.000 lat band # 49 1.000 1.000 1.000 1.000 1.000 lat band # 50 1.000 1.000 1.000 1.000 1.000 lat band # 51 1.000 1.000 1.000 1.000 1.000 file /daynite_3hrly_19950724.binary has been written Variable emis_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 0.972 0.972 0.972 0.972 0.972 lat band # 46 0.972 0.972 0.972 0.972 0.972 lat band # 47 0.972 0.972 0.972 0.972 0.972 lat band # 48 0.972 0.972 0.972 0.972 0.972 lat band # 49 0.972 0.972 0.972 0.972 0.972 lat band # 50 0.972 0.972 0.972 0.972 0.972 lat band # 51 0.972 0.972 0.972 0.972 0.972 file /emis_10_3hrly_19950724.binary has been written Variable cld_frac_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 0.000 0.000 0.000 0.429 0.429 lat band # 46 0.000 0.333 0.750 0.333 1.000 lat band # 47 0.000 0.200 0.750 0.250 0.750 lat band # 48 0.250 0.000 1.000 0.400 0.400 lat band # 49 0.000 0.000 0.500 1.000 0.200 lat band # 50 0.250 0.000 0.500 1.000 1.000 lat band # 51 0.667 0.500 0.800 0.800 0.833 file /cld_frac_low_wat_3hrly_19950724.binary has been written Variable cld_tau_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 0.000 0.000 0.000 1.897 1.897 lat band # 46 0.000 2.240 2.620 3.180 2.903 lat band # 47 0.000 1.130 4.093 7.870 3.040 lat band # 48 7.870 0.000 1.262 4.870 5.815 lat band # 49 0.000 0.000 3.160 5.967 9.540 lat band # 50 2.120 0.000 1.730 3.585 4.217 lat band # 51 1.810 1.535 2.128 4.780 3.080 file /cld_tau_low_wat_3hrly_19950724.binary has been written Variable cre_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 0.000 0.000 0.000 9.840 9.840 lat band # 46 0.000 9.840 9.840 9.840 9.840 lat band # 47 0.000 9.840 9.840 9.840 9.840 lat band # 48 9.840 0.000 9.840 9.840 9.840 lat band # 49 0.000 0.000 9.840 9.840 9.840 lat band # 50 9.840 0.000 9.840 9.840 9.840 lat band # 51 9.840 9.840 9.840 9.840 9.840 file /cre_low_wat_3hrly_19950724.binary has been written Variable cld_top_temp_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 0.000 0.000 0.000 267.633 267.633 lat band # 46 0.000 266.000 266.167 268.400 266.600 lat band # 47 0.000 268.400 265.533 264.100 268.467 lat band # 48 266.000 0.000 269.375 267.800 265.400 lat band # 49 0.000 0.000 270.900 267.200 264.700 lat band # 50 269.700 0.000 271.750 269.525 266.600 lat band # 51 268.750 268.450 271.800 269.800 270.400 file /cld_top_temp_low_wat_3hrly_19950724.binary has been written Variable cld_top_pres_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 0.000 0.000 0.000 814.334 814.334 lat band # 46 0.000 742.474 759.918 816.536 789.531 lat band # 47 0.000 778.309 738.031 724.941 815.760 lat band # 48 709.833 0.000 804.735 791.455 745.069 lat band # 49 0.000 0.000 820.667 767.576 723.131 lat band # 50 760.073 0.000 825.589 802.397 752.073 lat band # 51 736.463 744.219 819.089 798.462 815.344 file /cld_top_pres_low_wat_3hrly_19950724.binary has been written Variable cld_base_pres_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 0.000 0.000 0.000 864.334 864.334 lat band # 46 0.000 792.474 809.918 866.536 839.531 lat band # 47 0.000 828.309 788.031 774.941 865.760 lat band # 48 759.833 0.000 854.735 841.455 795.069 lat band # 49 0.000 0.000 870.667 817.576 773.131 lat band # 50 810.073 0.000 875.589 852.397 802.073 lat band # 51 786.463 794.219 869.089 848.462 865.344 file /cld_base_pres_low_wat_3hrly_19950724.binary has been written Variable cld_water_cnt_ Hour = 06 Day = 24 lon # = 100 101 102 103 104 lat band # 45 0.000 0.000 0.000 0.026 0.026 lat band # 46 0.000 0.028 0.034 0.043 0.038 lat band # 47 0.000 0.015 0.051 0.097 0.041 lat band # 48 0.094 0.000 0.017 0.064 0.073 lat band # 49 0.000 0.000 0.043 0.077 0.116 lat band # 50 0.027 0.000 0.023 0.047 0.053 lat band # 51 0.022 0.019 0.029 0.063 0.041 file /cld_water_cnt_low_wat_3hrly_19950724.binary has been written