Development and validation of a snow albedo algorithm for the MODIS instrument

Abstract

A prototype snow albedo algorithm has been developed for the Moderate Resolution Imaging Spectroradiometer (MODIS). It complements existing MODIS products by providing albedo measurements for areas mapped as snow on a global daily basis by MODIS. Cloud detection and atmospheric correction are accomplished using existing MODIS products. Models of the bidirectional reflectance of snow created using a discrete-ordinate radiative transfer (DISORT) model are used to correct for anisotropic scattering effects over non-forested surfaces. Initial algorithm validation is undertaken through comparisons with broadband albedo measurements made at the U.S. National Oceanic and Atmospheric Administration (NOAA) Surface Radiation Budget Network (SURFRAD) site in Fort Peck, MT. In situ SURFRAD albedo measurements are compared to daily MODIS snow albedo retrievals for the period 21–26 November 2000 created from five narrow-to-broadband albedo conversion schemes. The prototype MODIS algorithm produces reasonable broadband albedo estimates. Maximum daily differences between the five MODIS broadband albedo retrievals and in situ albedo are 15%. Daily differences between the best MODIS broadband estimate and the measured SURFRAD albedo are 1–8%. However, no single conversion scheme consistently provides the closest albedo estimate. Further validation and algorithm development using data from North America and Greenland is ongoing.

A review of global satellite-derived snow products

“…The Climate-Modeling Grid was developed to be useful for the evaluation of climate models and for studies at large spatial scales. Other features of the MODIS snow product suite include daily snow albedo (Klein and Stroeve, 2002) and fractional snow cover (Salomonson and Appel, 2004). In addition, a new cloud-gap filled product provides information on cloud persistence, and uses observations from prior days to map snow (Hall et al, 2010).…”

Large surface meltwater discharge from the Kangerlussuaq sector of the Greenland ice sheet during the record-warm year 2010 explained by detailed energy balance observations

“…Therefore daily MOD10A1 albedo data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite (Hall et al, 2006;Klein and Stroeve, 2002) were used. MOD10A1 data were validated using GC-Net AWS data by , who reported a root mean square (RMS) error of 0.067 and correlation of 0.79.…”

MODIS Snow and Sea Ice Products

“…In deriving albedo, atmospherically-corrected MODIS surface reflectances in individual MODIS bands for snow-covered pixels located in non-forested areas are adjusted for anisotropic scattering effects using a DlScrete Ordinates Radiative Transfer model (DISORT) and snow optical properties (Klein et al 2000; Stroeve 2002). Currently in the aigori~m, snow-covered forests are considered to be Lambertian reflectors.…”