########################################################################### README file for the global IR land surface emissivity database Version: 3.0 Created by Suzanne Seemann and Eva Borbas CIMSS/SSEC University of Wisconsin Contact: Eva.Borbas@ssec.wisc.edu Date of release: August 2009 Note: This dataset was released in the hope that it will be useful, but without any warranty. !!!!! CHANGE IN DATA VERSION !!!!! ########################################################################### OVERVIEW AND REFERENCE: The UW-Madison baseline fit (BF) global emissivity data available here were derived using a procedure that fits monthly averaged MODIS MYD11 (MODIS level 3 operational land surface emissivity product) values to a baseline emissivity spectra determined using laboratory measurements of land surface materials. The JAMC paper that details the baseline fit procedure for deriving the database and its application to atmospheric retrievals is available at the website http://cimss.ssec.wisc.edu/iremis/ Please reference this paper for any use of the database: Seemann, S.W., E. E. Borbas, R. O. Knuteson, G. R. Stephenson, H.-L. Huang, 2007: Development of a Global Infrared Land Surface Emissivity Database for Application to Clear Sky Sounding Retrievals from Multi-spectral Satellite Radiance Measurements. J. of Appl. Meteor. and Climatol., Vol. 47, 108-123. BF DATA VERSIONS: !!!!!!!! Attention!!!!!!!!!!!! Because the BF emissivity data uses the MODIS MYD11 product as input, BF emissivity values will be affected by changes in the MYD11 algorithm. Beginning with January 2007 the NASA LP DAAC began processing the MYD11 data with the new collection 5 algorithm. Since then significant differences were found between MYD11 collection 4 and 5 data (especialy over desert areas). Due to these differences begining of this year the NASA LP DAAC decided to continue to produce collection 4 data beyond December 2006 but using the only available collection 5 MODIS input data like cloud mask, L1B data and atmospheric profiles. The new version of MYD11 data is called collection 041. You can find more information about the MYD11 collection 041 product in the following document: http://landweb.nascom.nasa.gov/QA_WWW/forPage/C41_LST.doc. As a result, the version 3 BF emissivity data derived from collection 5 MYD11 has been removed from this website and has been recomputed using the new collection 041 MYD11 as input. (Note, there are no changes in the BF algorithm itself between BF versions 2 and 3.) Version 2 BF emissivity data (derived from collection 004 MYD11 products) is available between Sept 2002 and December 2006 and version 3 data (derived from collection 041 MYD11 products) is available from Jan 2007 till May 2009. As collection 041 MYD11 data from other months becomes available on the LP DAAC server, the BF database will be processed. In the filenames of version 3 BF emissivity data, the "041" reflects the use of the collection 041 MYD11 data (ex. global_emis_inf10_monthFilled_MYD11C3.A2004214.041.nc.bz2 ). The filename of the version 2 BF data which used the MYD11 collection 4 data will not be changed (ex. global_emis_inf10_monthFilled_MYD11C3.A2004214.nc.bz2). Since there migh be differences due to cloud mask, over certain areas it is not recommended to use version 2 and 3 BF data as a continuous dataset. More information about the updates to MYD11 can be found in the following website: https://lpdaac.usgs.gov BF DATA FORMAT: The global emissivity data are available in NETCDF format, with one file per month. Each file contains monthly emissivity data at 10 inflection points on a 0.05 x 0.05 degree grid. The wavelengths saved in the files are 3.6, 4.3, 5.0, 5.8, 7.6, 8.3, 9.3, 10.8, 12.1, and 14.3 microns. Since these 10 wavelengths were chosen as inflection points to capture as much of the shape of the higher resolution spectra as possible, these values can be interpolated between inflection points to arrive at any emissivity between 3.6 and 14.3 microns. The monthly files also contain a flag for each grid point which gives information about how the emissivity data was derived, as explained below: flag = 0 for ocean/coastlines where there was no MYD11 data, and thus no baseline fit-derived emissivity. flag = 1 for regions where the baseline fit method was used to compute emissivity. flag = 2 where MYD11 data was not available at this lat/lon, and the emissivity average over the two adjacent months (before and after) for the corresponding lat/lon and wavelength was used. flag = 3 where no MYD11 data was available in either adjacent month for the corresponding lat/lon, and emissivity was filled in with the 2003 annual average for this lat/lon and wavelength. flag = 4 where no MYD11 data was available all year for this lat/lon (this occurs in some Antarctic regions only due to MYD11 algorithm constraints). Emissivity was filled in with the average of the annual average over all emissivity at a given wavelength with latitude < -80S. The latitude and longitude of the grid points are in the separate file: "global_emis_inf10_location.nc".