February 18, 2015 Dr. Katrina E. Bennett, Investigating snow cover depletion timing in boreal watersheds of Interior Alaska from remote sensing, in situ measurements, and statistical modeling Postdoctoral Student, Los Alamos National Lab

Investigating snow cover depletion timing in boreal watersheds of Interior Alaska from remote sensing, in situ measurements, and statistical modeling

Dr. Katrina E. Bennett, Postdoctoral Student, Los Alamos National Lab

Snow cover depletion timing in boreal Interior Alaska is a fundamental process that affects multiple climatic, human, and ecological systems and is known to be changing in response to amplified climate warming. The lack of a high quality, spatially and temporally dense meteorological network in Alaska for use in basin-scale snowpack modeling necessitates alternative methods to estimate melt timing. This study provides an estimate of snow melt timing characteristics for 38 stations across Interior Alaska using the Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing snow cover extent (SCE) products and a nonlinear regression approach (2000-2012). The nonlinear model replicated the depletion curve with accuracy compared to observed data, and showed promise as a statistical tool to define melt timing. One index, the date of maximum snow depletion initiation, closely correlated with snow depth observed at climate stations (average rho=0.57, p-values < 0.001). The nonlinear model parameters were then predicted based on tree regression of climate and physiographic indices to estimate the year-to-year snow depletion timing. Important climate and physiographic variables identified were temperature, albedo, wind speeds combined with topographic features (slope and aspect). The SCE curve was estimated for 1979-2012, allowing for further analysis of snow melt metrics over time. The technique was also used to generate an Alaska-wide example of the variability in select melt timing indices, highlighting the unique response of boreal interior. The methods described in this work can be used to illustrate the pattern of snow cover depletion for river forecasting and water resource management.