Date: Fri, 21 Sep 2001 12:42:44 -0400 From: "Larry L Stowe" X-Mailer: Mozilla 4.7 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: ... << many addressees>> Subject: NEW AVHRR Pathfinder Atmosphere (PATMOS) Data Set Dear PATMOS User: We have just completed our reprocessing of the AVHRR Pathfinder Atmosphere (PATMOS) data set for data from NOAA-7, 9, 11 and 14, to correct for errors and to extend it to June 2001. The data set begins with September 1981, with July-August 1981 missing due to uncorrectable calibration errors, September, 1994 - February 1995 missing due to loss of AVHRR coverage after the failure of the AVHRR on NOAA/11 and instability in NOAA/14 after its launch in December 1994, and November 1988 missing due to an incomplete month of NOAA/9 data. The reprocessing was performed to correct for errors discovered after the initial reprocessing was completed in 1997, as documented in an ERROR ALERT posted on the Aries ftp file server. These errors included: Temperature to Radiance Conversion inconsistencies affecting NOAA/7,9 and 14 data; Computation of Available Solar Energy (ASE); Computation of Absorbed Solar Radiation (ASR); No (or out-of-date) calibration drift correction applied to NOAA-14 channels 1 and 2; and cloud contamination for cloud-free ocean pixels poleward of 50 degrees latitude. These have all been corrected or modified to minimize their impact on analysis of the data. The Temperature to Radiance Conversion was corrected by using the correct conversion coefficients for each of the four satellites. The coding errors that caused the ASE and ASR to be in error were corrected. The most recent calibration drift correction coefficients in use in NESDIS for NOAA/14 operations since December 8, 1998 have been used for the entire NOAA/14 record. Because of unresolvable ambiguities between cloud and sea ice detection with the CLAVR-1 algorithm poleward of 50 latitude, it was decided to consider daily PATMOS-1 cloud-free radiance parameters as missing whenever the percent ice cover in these ocean grid cells was over 0%, to prevent any inappropriate use of these occasionally contaminated cloud-free radiances (all other radiances and parameters of PATMOS-1 are reported as observed). The PATMOS data sets (PATMOS-1 and -2) are accessible via anonymous ftp at: ftp://saa.noaa.gov; in the patmosa directory. Further instructions are given in the README, distribution.tar and userguide.tar files. Selected PATMOS-2 monthly mean parameters can be visualized and electronically accessed at the Satellite Active Archive's web page found at: http://las.saa.noaa.gov/. These data can be located by clicking AVHRR Pathfinder Global Products (either static map or java map). Java maps permit interactive zooming as well as selection of various regions of the earth. The data are available online in a number of different formats, which include NetCDF, MS-Excel Spreadsheet, and ASCII text. A number of graphs may also be selected. A manuscript describing the PATMOS data set has been submitted to the Journal of Climate. It is available via anonymous ftp at ftp://orbit-net.nesdis.noaa.gov@pub/crad/rcat/stowe/PATMOS/JCLIMATE. I am retiring from NOAA, effective September 22, 2001. If you have technical questions or need help with access or processing the data sets, please contact Dr. Andrew Heidinger at Andrew.Heidinger@noaa.gov or Dr. Herbert Jacobowitz at Herbert.Jacobowitz@noaa.gov. If you'd like to know what I'll be doing with my life after NOAA, have a look at http://www.StoweAwayTours.com. Here's to your successful research with this unique climate data set. Cheers, Larry -- Dr. Larry L. Stowe E/RA1, RM 712S, WWBG NOAA/NESDIS Office of Research and Applications 5200 Auth Road Camp Springs, MD 20746-4304 Phone: 301-763-8053, ext. 114 Fax: 301-763-8108 Email: Larry.L.Stowe@noaa.gov Use same address for FedEx packages.