---TITLE: CASPR-ARCMIP 1997-1998 data set ---AUTHORS: Prof. Judith Curry School of Earth and Atmospheric Sciences Georgia Institute of Technology Atlanta, GA 30332-0340 office: 404 894-3955 fax: 404 894-5638 e-mail: curryja@eas.gatech.edu Contact for data questions : Randolph A. Reeder Aerospace Engineering Dept. University of Colorado Boulder, CO 80309 office: 303 492-4266 e-mail: rreeder@cloud.colorado.edu ---DATA SET OVERVIEW: The CASPR-ARCMIP data set consists of SHEBA AVHRR Arctic satellite retrievals corresponding to the ARCMIP domain location for the years 1997 and 1998. The original data is from the SHEBA AVHRR Full Arctic 25 km Retrievals ( version 1.0 ) set produced using the Cloud and Surface Parameter Retrieval ( CASPR ) algorithms. The original data set covers the entire Arctic twice daily for all of 1997 and 1998 at 25 km resolution. It is available from the web site at http://stratus.ssec.wisc.edu/products/ The CASPR-ARCMIP data is a subset of this original data corresponding to all locations given in the domain.txt file for the ARCMIP region. The time period is from 01 January 1997 through 31 December 1998. Twice daily data is given for 0400 and 1400 hours local time except for 1400 hours on day numbers 69 and 197 of year 1998 ( this data is missing ). ---DATA FORMAT: The files in this directory consist of two gzipped tar files called caspr_arcmip_1997.tar.gz and caspr_arcmip_1998.tar.gz each of size ~73 Mbytes and an ASCII file of the ARCMIP region called domain.txt . The tar file caspr_arcmip_1997.tar consists of 730 NetCDF files for the year 1997 with names caspr_1997xxx_0400.arcmip.nc ( for 0400 hours ) or caspr_1997xxx_1400.arcmip.nc ( for 1400 hours ) where xxx is the day-of-year from 001 thru 365. The 0400 or 1400 indicate the nearest hour in local solar time. The tar file caspr_arcmip_1998.tar consists of 728 NetCDF files for the year 1998 with names caspr_1998xxx_0400.arcmip.nc ( for 0400 hours ) or caspr_1998xxx_1400.arcmip.nc ( for 1400 hours ) where xxx is the day-of-year from 001 thru 365. The 0400 or 1400 indicate the nearest hour in local solar time. Two data files are missing : caspr_1998069_1400.arcmip.nc and caspr_1998197_1400.arcmip.nc . Each of the NetCDF files contains 20 variables. Each variable is a two dimensional array indexed by the location indices of the domain.txt file. The names of the variables are : 1. LAT the latitude in degrees 2. LON the longitude in degrees 3. LANDMASK the surface type mask 4. TSKIN the surface skin temperature in K 5. ALBEDO the surface broadband albedo 6. RADIUS the cloud droplet effective radius in micrometers 7. TAU the cloud optical depth 8. PHASE the cloud particle phase 9. CLDTEMP the cloud top temperature in K 10. CLDPRES the cloud top pressure in hPa 11. WATER the precipitable water in cm 12. SWDSFC downwelling shortwave radiation at surface in W/m^2 13. LWDSFC downwelling longwave radiation at surface in W/m^2 14. SWUSFC upwelling shortwave radiation at surface in W/m^2 15. LWUSFC upwelling longwave radiation at surface in W/m^2 16. SWDTOA downwelling shortwave radiation at TOA in W/m^2 17. SWUTOA upwelling shortwave radiation at TOA in W/m^2 18. LWUTOA upwelling longwave radiation at TOA in W/m^2 19. SWCLDF shortwave cloud forcing at surface in W/m^2 20. LWCLDF longwave cloud forcing at surface in W/m^2 The file domain.txt contains information about the ARCMIP region. The ARCMIP grid is defined by two indices x and y. The x index runs from 1 thru 70 and the y index runs form 1 thru 55 . For each x and y location the domain.txt file gives the latitude in degrees, the longitude in degrees, the elevation in meters, and the land use code for example ocean. The file contains 3850 ( 70 * 55 ) lines of data. The x and y indices correspond to the two indices of the variable arrays in the NetCDF files.