Introduction

1. 100 80 60 40 20 0 % Start Berkner Is. cm 0 20 40 60 80 End Berkner Is. Snow and Ice Products from the Aqua, Terra, and ICESat Satellites at the National Snow and Ice Data Center Part I: Overview of Standard Products Introduction Sensors on the NASA Earth Observing System (EOS) satellites are a significant advancement over their predecessors and are providing a wealth of information on snow and ice. The Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua and Terra spacecraft and the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) on the Aqua spacecraft provide improved visible/infrared and passive microwave imagery and products. The Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud, and land Elevation Satellite (ICESat) is the first satellite-borne laser altimeter and represents an entirely new technology for ice remote sensing. MODIS The Moderate Resolution Imaging Spectroradiometer (MODIS) was launched on the NASA EOS Aqua and Terra satellites. MODIS observes the earth at 36 visible and infrared spectral bands ranging from 0.405 – 14.385 μm. MODIS represents a substantial improvement in spatial resolution and spectral range and resolution over its predecessor, the Advanced Very High Resolution Radiometer (AVHRR), and yields much improved information on sea ice and snow properties. As one of NASA’s Distributed Active Archive Centers (DAACs), the National Snow and Ice Data Center in Boulder, CO is the repository for these data. In Part I below, we present information and data examples of standard products available from NSIDC. In Part II, to the right, we present two case studies that demonstrate the utility of combinations of the products and value-added fields derived from the standard products. Information and data can be obtained at: http://nsidc.org/daac/projects/ MODIS Sea Ice Cover 6 February 2004 1 km resolution EASE-Grid MODIS Snow and Ice Products AMSR-E The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) was launched onboard the NASA EOS Aqua satellite on May 4, 2002. Its six dual-polarized passive microwave frequencies represent the next step in passive microwave remote sensing and are a substantial improvement over its predecessor, the Special Sensor Microwave/Imager (SSM/I). AMSR-E’s improved spatial resolution and additional frequencies allow it to obtain improved products compared to SSM/I as well as entirely new products. AMSR-E vs. SSM/I AMSR-E Snow and Ice Products MODIS provides several sea ice and snow products, including sea ice cover (above), snow cover (far right), visible reflectance (near right), and infrared radiance. A summary of products available is listed in the table above. Snow Cover 500 m resolution Visible Image 500 m resolution AMSR-E Sea Ice Products, 4 March 2004 Sea Ice Products AMSR-E provides continuity with SSM/I sea ice concentrations, but at double the spatial resolution and with improved algorithms. For AMSR-E, the Enhanced NASA Team Algorithm (also called NASA Team 2) is employed for the Arctic, and a modified Bootstrap Algorithm for the Antarctic. Standard AMSR-E products also include sea ice temperature and snow depth over sea ice (only first-year ice in the Arctic), which are not available from previous satellite passive microwave sensors. (The sea ice temperature is indicative of the temperature of the emitting layer, which often corresponds to the sea ice/snow interface). The products are produced on a polar stereographic grid as daily composites of ascending, descending, and all passes over a 24-hour period; swath brightness temperatures are also available. More information on the sea ice products is available from Comiso et al., 2002. Sea Ice Concentration MODIS Swath Products over Alaska 5 March 2004 ICESat/GLAS The Geoscience Laser Altimeter System (GLAS) instrument was launched on the Ice, Cloud, and land Elevation Satellite (ICESat) January 12, 2003. ICESat/GLAS is the first satellite laser altimeter and produces a variety of unique ice products. The laser altimeter measures the topography of features on the earth’s surface including glacier height and sea ice freeboard at two frequencies, one green (532 nm) and one infrared (1064 nm). The active laser on ICESat/GLAS also has particular advantages over passive visible and infrared sensors in detecting clouds and cloud properties. This is especially beneficial over ice-covered surfaces where the surface and clouds can difficult to distinguish from each other using passive visible and infrared sensors. Ice Temperature Snow Depth Over Sea Ice 270 K ICESat/GLAS Ice Products 245 K • References • Armstrong, R.L.,and M.J. Brodzik, Recent Northern Hemisphere snow extent: A comparison of data derived from visible and microwave sensors, Geophys. Res. Lett., 23(19), 3673-3676, 2001. • Chang, A.T.C., A. Rango, and others, Algorithm Theoretical Basis Document (ATBD) for the AMSR-E Snow Water Equivalent Algorithm, version 3.1, 45 pgs., 30 Nov., 2000. • Comiso, J.C., D.J. Cavalieri, and T. Markus, Sea ice concentration, ice temperature, and snow depth using AMSR-E data, IEEE Trans. Geosci. Rem. Sens., 41(2), 243-251, 2003. • Emery, W.J., C.W. Fowler, J. Hawkins, and R.H. Preller, 1991. Fram Strait satellite image-derived ice motions, J. Geophys. Res., 96(C5), 8917-8920. • Hall, D.K.., G.A. Riggs, and V.V. Salomonson, Algorithm Theoretical Basis Document (ATDB) for the MODIS Snow, Lake Ice-, and Sea Ice-Mapping Algorithms. NASA Goddard Space Flight Center, Greenbelt, MD, Sept. 2001. • Kwok, R., H.J. Zwally, and D. Yi, ICESat observations of Arctic sea ice: A first look, submitted to Geophys. Res. Lett. • Zwally, H.J., B. Schutz, W. Abdalati, and others, ICESat’s laser measurements of polar ice, atmosphere, ocean and land, J. Geodynamics, 34(3-4), 405-445. Ocean Land No Data 5 March 2004 240 mm AMSR-E Snow Water Equivalent Product AMSR-E provides snow water equivalent estimates (SWE) as daily fields, 5-day composites, and monthly averages. Products are provided in 25 km EASE-Grid polar hemispheric and global projections. More information on AMSR-E snow products is available from Chang et al. (2000). Above, a sample from an ICESat pass shows an elevation profile over Antarctica. The section of the profile is indicated on the ground track. The colors on the ground track indicate elevation, with green being lowest elevation, followed by yellow, brown, purple and white for higher elevations. Acknowledgments Thanks to R. Schutz, H.J. Zwally and the rest of the ICESat/GLAS Science Team for the sea ice elevation data; to T. Haran and T. Scambos, for input on the ICESat/GLAS data; to J. Wolfe for MODIS imagery; to S.J.S. Khalsa for the Antarctic ICESat/GLAS example; and to N. Geiger-Wooten for additional assistance. 1 mm Ocean/Sea Ice Ice Sheet Bare Land No Data