s Donna J. Scott, Marilyn Kaminski, Jason Wolfe, Terry Haran NSIDC's MODIS Snow and Sea Ice Products NSIDC provides a suite of fully automated, quality controlled, daily global maps of snow and sea ice extent products, produced at 500m, 1000m, and 0.05º spatial resolutions from the MODIS instrument. The Terra satellite products are available in Collection 4 from February 2000 to the present; Aqua satellite products are available in Collection 4 from July 2002 to the present. MODIS at NSIDC Methods of Ordering MODIS data at NSIDC Along with the EOS Data Gateway (EDG), several methods are available to order MODIS data through NSIDC. The Search ‘n’ Order Web Interface (SNOWI) provides easier retrieval of MODIS tiled products. The Data Pool provides easy access for downloading recently produced data (currently 15 days for each product). Each of these interfaces can be accessed from NSIDC at Users can also request subscriptions to MODIS data, where data can be pushed to a user's machine as they becomes available at NSIDC. The machine-to-machine gateway is a functionality currently provided at NSIDC that allows users to develop their own command-line argument scripts/codes to access MODIS data directly from our archive disks. For further information on subscriptions or the machine-to-machine gateway, please contact NSIDC User Services at NSIDC's ordering interfaces provide tools to simplify identification of granules and to create subsets of granules. Browse images (online reduced resolution images) allow users to view data prior to ordering through the EDG and Data Pool. The HDF Subsetting Appliance (HSA), available through the EDG, gives users options to subset data spatially, temporally, and by parameter. The HDF to GeoTIFF converter (HEG), available through the Data Pool or as a standalone utility, provides options to stitch, subset, reproject and reformat certain products. The MODIS Swath-to-Grid Toolbox (MS2GT), developed at NSIDC, is a set of software tools that reads MODIS swath HDF-EOS data files and produces flat binary files of gridded data in a variety of map projections. NSIDC also offers many other options for converting the MODIS HDF-EOS format to binary or ASCII formats. For more information on these, please see our HDF-EOS tools page at MODIS Tools Provided and Developed by NSIDC MODIS Collection 5 (V005), planned to start in April 2005, will include several improvements to existing snow and sea ice products for Terra and Aqua instruments. The level 2 snow products will incorporate a revised cloud algorithm and a new fractional snow algorithm. The level 3 gridded daily snow products will also include fractional snow cover. The level 2 and level 3 sea ice products will be modified to eliminate sea ice determined by ice surface temperature. New products will include gridded daily snow products in a polar projection, as well as monthly snow and sea ice products. These additions will be valuable for polar research and global modeling using cryospheric data. What to Expect in Collection 5 Viewing Snow Cover Over Colorado Using MODIS Tools The Collections of MODIS In November 2003, Terra data were reprocessed to Collection 4 (V004). The MOD10_L2 files now have two separate snow cover masks, one incorporating the original cloud mask, and another using a less cloud-conservative mask. A sinusoidal grid projection replaces integerized sinusoidal (ISIN) grid projection in MOD10A1 and MOD10A2. The MOD10A1 data granules after 14 September 2003 include a “Snow Albedo” data array. The fractional snow cover in MOD10C1 now ranges from 0 – 100%, and the structural metadata (StructMetadata.0) has been corrected from 24 July 2002 onward. All of the sea ice products now have a threshold change from 277 K to 281 K in the thermal mask. In July 2004, all Aqua products were reprocessed to V004. This collection includes the same properties as Terra V004, except MOD29P1N does not have a counterpart in Aqua V004. The MYD10A1 granules after 4 July 2002 include a “Snow Albedo” data array. In addition, all Aqua V004 snow and ice granules use MODIS band 7 instead of band 6, due to the large number of malfunctioning detectors in band 6. And due to increasingly erroneous snow detection using the NDSI/NDVI method with band 7 data, the NDSI/NDVI test is disabled. This MYD10_L2 browse image from 27 December 2003 (20:25 UTC) was downloaded from the Data Pool. The image covers the western United States. The image is upside-down because the Aqua satellite is traveling along a descending pass (north to south). This GeoTIFF image was created with the MODIS Swath-to-Grid Toolbox (MS2GT), available from NSIDC. The image covers the same area (central Colorado) as the above image, using a single MOD10_L2 file from 21 May 2003 as input. Unlike the above 8- day composite image, this daily swath file contains more cloud contamination (blue). Also notice the difference in snow pack resulting from melting, compared to the other image. The file used to create this image is MOD10_L2.A hdf. This image was created with the HDF-EOS to GeoTIFF converter (HEG). Five input tiles were stitched together, a subset was extracted for central Colorado, and the subset was reprojected to a Universal Transverse Mercator (UTM) projection. Data cover 17 to 24 May The following MOD10A2 8-day composite files were used as input: MOD10A2.A h09v hdf, MOD10A2.A h09v hdf, MOD10A2.A h10v hdf, MOD10A2.A h10v hdf, MOD10A2.A h10v hdf These images were created from the HDF Subsetting Appliance (HS A), a subsetting tool built into the EOS Data Gateway. The images were derived from two of the five MOD10A2 data granules used to create the images at the right. Data cover 17 to 24 May MODIS Snow and Sea Ice Products