OLI-DRFS: Retrievals of Dust Radiative in Snow from Landsat-8

Abstract:

Snow is one of the brightest among earth’s natural surfaces, with an albedo of ~0.9 when first deposited. Deposition of light-absorbing particles (LAPs), such as dust and black carbon aerosols, darkens snow’s surface and greatly reduces the visible albedo. This leads to an increase in radiative forcing, the additional solar radiation absorbed due to the presence of LAPs, which is known to initiate snowmelt earlier than anticipated. Other adverse effects may also result from this process including snow albedo feedbacks, in which the additional energy accelerates grain growth and exposes darker substrate earlier, respectively lowering the near-infrared snow albedo and the land surface albedo. Snow in the mid-latitudes is of particular concern as this critical water resource is located near aerosol emission sources, increasing its susceptibility to the impacts of LAP deposition. Although the ability to consistently monitor such impacts is limited, remote sensing has the potential to fill observation gaps over inaccessible mountain snow. The MODIS Dust Radiative Forcing in Snow (MODDRFS) algorithm uses surface reflectance data to estimate the amount of solar radiation absorbed by the presence of dust and other LAP on snow. MODDRFS has the capability to provide data on a daily basis, but the resolution is relatively coarse (500 m) with a relatively high uncertainty (~30 W/m²). This study adapts the MODDRFS algorithm concept to Landsat 8 (OLI) surface reflectance data, referred to as OLI-DRFS. By doing so, we are able to assess snow albedo and LAP RF at an enhanced resolution that may provide more accurate results in complex terrain. Although less frequent, this dataset provides the means for potential downscaling of MODDRFS, leveraging the finer spatial resolution of OLI-DRFS and the frequent temporal resolution of MODDRFS. We will demonstrate retrievals from the Western US and Himalaya.