Variations in the snow melt onset date derived from passive microwave data

Providing a long term climatology of snow melt onset over Arctic sea ice is useful for detecting climate change, validating climate models, and accurately modeling the spring Arctic surface energy balance. Passive microwave satellite data from the Scanning Multichannel Microwave Radiometer (SMMR) and the Special Sensor Microwave/Imager (SSM/I) are indispensable for this task because they represent an all-season, all-weather, diurnally consistent, and reasonably continuous data set of more than 20 years in length (1979-1998). In this project, interannual variations in a passive microwave-derived snow melt onset database are discussed. A consistent blended brightness temperature record, created from the different satellite platforms through linear regression analysis, is used to ensure consistency in the data set. Snow melt onset dates are calculated based on the horizontal brightness temperature range between 19 and 37 GHz. Results indicate both regional and annual variations exist in the melt onset date. For instance, melt onset often exceeds 30 days over first-year ice regions, but rarely surpasses 20 days over multiyear ice regions. In addition, the annually-averaged melt onset date shows a 14 day range between the abnormally early melt in 1990 and the anomalously late melt in 1996. This new data set provides a valuable addition to researchers for seasonal-to-interannual and long term climate studies.