Changes in Surface Albedo of Desert Playas Caused by Short Term Variations in Surface Moisture

Desert playas form a landscape often in stark contrast to surrounding mountain ranges due to their minimal topographic relief, lack of vegetation, and saline soils. The high soil salinity creates light-colored surfaces with high surface albedo, often upwards of 50 percent. Abrupt flooding on desert playas caused by direct rainfall, runoff from surrounding higher terrain, and surface winds displacing shallow water bodies reduces the surface albedo. Specifying albedo accurately as a function of land surface type is critical for weather and climate models in interior basins. The basin and range topography of Northern Utah forms large desert playas which undergo abrupt surface changes in response to precipitation events. A weather station installed to support a separate NSF project on the Bonneville Salt Flats provides estimates of albedo that can be related to the changes in the underlying surface. Another weather station located on the playa margin between the Great Salt Lake and Antelope Island provides a contrasting playa surface type. Standard meteorological data as well as solar radiation data are collected at both playa sites. MODIS surface albedo product MCD43A3 and land surface reflectance product MOD09A1 provide remote sensing estimates of albedo and water coverage of the playa sites for this study. Discriminating high albedo playa surfaces from clouds is difficult on the basis of satellite retrieval algorithms. The MODIS MCD43A3 surface albedo product is often unable to produce high quality albedo data for pixels containing the desert playa sites. The MODIS MOD09A1 land surface reflectance product allows for the calculation of the normalized difference water index (NDWI) which highlights playa flooding events and periods of increased playa soil moisture with greater reliability than the MODIS albedo product. Estimates of albedo at the two playa sites are related to the NDWI to understand the impact precipitation events have on surface albedo.