Detecting Snowfall Events over the Arctic Using Optical and Microwave Satellite Measurements

Abstract. The precipitation over the Arctic region is a difficult quantity to determine with high accuracy, as the in situ observation network is sparse, and current climate models, atmospheric reanalyses and direct satellite-based precipitation observations suffer from diverse difficulties that hinder the correct assessment of precipitation. We undertake a proof-of-concept investigation into how accurately optical satellite observations, namely Sentinel-2 surface reflectance-based grain size-connected specific surface area of snow (SSA), and microwave-based snow water equivalent (SWE) estimates can detect snowfalls over the Arctic. Here, we chose a limited area (a circle of 100 km radius around Luosto radar located in Northern Finland) and a short time period (covering March 2018) to test these data sources and their usability to this precipitation assessment problem. We classified differences between observations independently for SSA and SWE and compared the results to the radar-based snowfall information. These initial results are promising. Situations with snowfalls are classified with high recalls, 67 % for SWE and around 90 % for SSA when compared to radar-based data. Cases without snowfalls are more difficult to classify, the recall value for SWE is only 38 %, but for SSA the recall values are higher, varying from almost 60 % to over 70 %. These results indicate, that using optical and microwave-based satellite observations can be used to detect snowfall events over the Arctic.