Evaluation of IMERG and MRMS remotely sensed snowfall products

In this study, snow accumulation (SA) estimates of the Integrated Multi-satellitE Retrievals for GPM (Global Precipitation Measurement) (IMERG) and Multi-Radar/Multi-Sensor (MRMS) products were evaluated against the SNOwpack TELemetry (SNOTEL) ground observations over a Basin in the western United States from October 2016 to February 2017. IMERG underestimated SA in three snowfall probability thresholds of 45%, 65% and 85%. With increasing the threshold from 45% to 85%, MRMS Bias index showed overestimation compared to that of the IMERG. Overall, MRMS presented more accurate results than the IMERG. In categorical analysis, IMERG had better probability of detection (POD) values than the MRMS although MRMS was generally more accurate than the IMERG in all thresholds. Moreover, with respect to Bias, mean absolute error (MAE) and root mean square error (RMSE) indices in various elevation classes, IMERG was more efficient in lower elevation classes while in categorical analysis, MRMS performed worse than the IMERG based on the POD values. This weakness increased in higher elevation classes. Also, in another comparison in different SA classes, the results showed that IMERG had better performance than the MRMS under moderate snowfall condition. However, MRMS estimates improved in heavy snowfall. In general, it was concluded that the IMERG performed better in snowfall detection than the MRMS; while in contrast, the opposite was true in estimating the SA.