Spatio-Temporal Trends in Melt Onset in the Upper Indus Basin Using Enhanced-Resolution Passive Microwave Brightness Temperatures

Since 1978, satellite passive microwave sensors have observed Earth passive microwave emissions. Collected globally both day and night and able to see through most clouds, passive microwave measurements are used to derive significant and meaningful cryospheric climate records at high latitudes and high elevations, including sea ice concentrations, snow water equivalent and snow and ice melt onset. Using the newly-available NASA MEaSUREs Calibrated, Enhanced-Resolution Brightness Temperature (CETB) Earth System Data Record (ESDR), we are investigating improvements to the Diurnal Amplitude Variation (DAV) melt onset detection algorithm in topographically complex regions of High Asia. The CETB ESDR leverages new, cross-sensor calibrations of Level 2 swath data and the numerically efficient radiometer version of the Scatterometer Image Reconstruction (rSIR) method to increase image spatial resolution up to 3.125 km for the highest measured frequencies. The rSIR processing has been applied to the complete SSM/I-SSMIS and AMSR-E observation record, including many periods of sensor overlap that have never before been available as gridded products. We present analysis of melt onset algorithms in the high-relief Upper Indus Basin, including spatio-temporal statistics and trends, correlation of drainage-scale melt timing with available streamflow records, and potential improvements to melt onset detection from the complete and overlapping time series, for the period 1987-2017.