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Validation of the Global Precipitation Measurement IMERG Products in the Canadian Arctic

Precipitation is a meteorological variable with high special and temporal variability. It plays a key role in the hydrological cycle and is crucial for water resource management, reanalyses and numerical weather prediction. While the south of Canada is more densely covered by ground-based measurement stations, coverage is sparse in the northern regions, e.g., beyond 60°N. Particularly in these regions, satellite measurements can potentially fill the gaps.

The Integrated Multi-satellitE Retrievals for GPM (IMERG) algorithm takes advantage of a constellation of the so-called GPM Core Observatory and various passive microwave satellite sensors. Their information is combined in IMERG to estimate precipitation rate. IMERG features an early, a late and a final product with a latency of 4-5 hours, 18 hours and 4 months, respectively, and also offers a monthly as well as a half-hourly product. While the final product, with maximum accuracy, is the product of choice when it comes to climatological questions, the early product is the most relevant one for near-realtime applications.

Since precipitation in the Arctic is generally very light, remote sensing measurements are very challenging. In addition, passive microwave sensors struggle with precipitation measurements over ice and snow surfaces. Hence, an extensive validation study is performed using various ground-based precipitation measurements from the Environment and Climate Change Canada (ECCC) supersite at Iqaluit (63.75°N, 68.55°W). In this study, we examine the most recent IMERG products, Version 5.2. While the current focus is on the final IMERG products, future studies also aim at the validation of the early near realtime product. In addition, the study will be expanded to include the ECCC supersite at Whitehorse (60.71°N, 135.07°W) and several independent ground-based stations beyond 60°N.