Cryospheric and Polar Processes Seminar

Dusting for the fingerprints of dust-on-snow in the Upper Colorado River Basin

Dr. Mark Raleigh, CIRES Visiting Postdoc, University of Colorado Boulder

Abstract: The deposition of desert dust on seasonal snow and glaciers alters the surface energy balance, specifically through enhanced absorption of shortwave radiation.  In the Upper Colorado River Basin (UCRB), the increased radiative forcing with dust-on-snow has advanced snowmelt on the order of 3 to 7 weeks. From a hydrologic perspective, this shift in snowmelt timing is problematic, as there is evidence that it has increased evapotranspiration and decreased annual streamflow in the UCRB. Dust is furthermore problematic because operational river forecasting models do not account for perturbations in snow albedo with dust deposition, and degradation in model accuracy has been linked to extremes in dust-on-snow loading.

Expanded monitoring of dust-on-snow in the UCRB with in situ observations and remote sensing began in the early 2000s and this relatively short record shows considerable interannual variability in dust conditions. Extending knowledge about annual dust-on-snow conditions in the UCRB prior to the 21st century would provide context for changes in the water balance and could benefit the calibration of operational river forecasting models.  This project aims to identify the fingerprint of dust-on-snow as can be inferred from operational measurements, models, and remote sensing, and to extend the dust record in the UCRB back to the mid-1980s.  In this presentation, I will focus on how SNOTEL data may provide clues about interannual and spatial changes in dust-on-snow in the UCRB.  I will also present preliminary work comparing dust-on-snow signatures from MODIS and Landsat.