Bias-Adjusted Satellite-Based And Reanalysis Products Show Agreement In Estimating North American Monsoon Season Precipitation
Presenter: Stella Heflin1
Co-Author(s): Reza Ehsani
Advisor(s): Dr. Ali Behrangi
1Department of Hydrology and Atmospheric Sciences, University of Arizona
Assessment of precipitation products with ground-based data is essential to building confidence over data-scarce regions. Precipitation products tend to have large errors in semi-arid regions like the Southwestern US, where accurate precipitation quantification is critical for water resource management and flood mitigation. Therefore, this region, with a high density of ground-based data, is important for product evaluation and is interesting due to its monsoonal precipitation pattern, in which changes in circulation patterns that bring tropical moisture to the region yield over 50% of the region’s precipitation between the months of June-September. The performance of precipitation products was evaluated on precipitation rate and intensity over Arizona and New Mexico for the monsoon seasons 2002-2021. These products include the European Center for Medium-Range Weather Forecasts (ECMWF) Reanalysis 5th Generation-Land (ERA5-Land), and three satellite-based datasets: Integrated Multi-SatellitE Retrievals for Global Precipitation Mission (GPM) (IMERG-Late, IMERG-Final) and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks - Dynamic Infrared Rain Rate (PDIR-Now). The reference was Stage IV, a ground radar-based product. Results indicate that all satellite-only products tend to capture interannual patterns of precipitation rate but struggled to capture high-intensity events. However, IMERG-Final notably captured interannual precipitation rate trends better (Stage IV correlation: 0.873 Arizona, 0.787 New Mexico) than other products. Meanwhile, ERA5-Land performed well in capturing both precipitation rate (Stage IV correlation: 0.922 Arizona, 0.696 New Mexico) and precipitation volume. The implications of this study indicate the importance of gauge adjustment for satellite products (IMERG), especially over arid regions.