On the Potential of GPM and JAXA Precipitation Retrievals in Probing Low, Moderate and High Precipitation Regimes over Semi-Arid Southwest US

The Sixth Assessment Report by the Intergovernmental Panel on Climate Change emphasizes climate change as the leading cause for an increase in the frequency and intensity of extreme precipitation events globally. These events are known to have several severe consequences including landslides, flash flooding, and extensive damage to infrastructures and ecosystems. Particularly affected by this variability are drylands characterized by limited precipitation and lower cloud coverages. Drylands, which cover 46.2% of the Earth's surface and are inhabited by three billion people, are highly vulnerable to climate change. Accurate monitoring and prediction of precipitation, along with understanding its variability across various temporal (from hourly to climatological) and spatial (from local through regional to global) scales remains critical for improving quantitative precipitation forecasts over drylands. Thus, a comprehensive understanding of the accuracy and errors associated with precipitation products obtained via ground based (bottom-up) and satellite-based (top-down) approaches over drylands remains critical.

Satellite precipitation products (SPPs) offer global coverage enabling comprehensive climatological studies as well as near real-time observations for decision-making. Integrated Multi-satellitE Retrievals for GPM (IMERG) and Global Satellite Mapping of Precipitation (GSMaP) from JAXA are two high-resolution global SPPs, currently in wide use for their superior performance over humid and sub-humid regions. However, their potential effectiveness over drylands has not been evaluated yet. We aim to (1) understand how these SPPs perform over semi-arid west Texas (southwestern US), and (2) determine the key precipitation products and associated intercomparison framework that are most suitable for real-time analysis of diverse precipitation events. To this end, we examined the accuracy of the above mentioned SPPs at diverse precipitation regimes (low, moderate, high) to identify their errors and accuracies via ground validation framework. Comparing these SSPs with ground-based "truth" across various precipitation intensities would help to identify gaps, inaccuracies, and uncertainties associated with different precipitation regimes in turn improving our understanding, predictive capabilities, and their impacts on climate and water resources. Unlike most major drylands, West Texas has an excellent ground-based precipitation monitoring system (i.e., the West Texas Mesonet, WTM). Additionally, rain gauges installed by NASA as a part of the Synergetic Surface-based and Satellite-borne Measurements of Arid-region Aerosol and Precipitation (S³-MAAP) project offer an excellent opportunity for conducting comprehensive inter-comparison efforts over a semi-arid region. Our analysis conducted via comparing gauge-calibrated SPPs against WTM measurements of rainfall indicates a significant dependence of the bias on varying precipitation intensities. While lower precipitation intensities tend to be overestimated, there is a notable underestimation associated with high precipitation events. Thus, a thorough evaluation of these newly released SPPs is crucial for identifying the most suitable product for near-real-time monitoring of extreme weather events over drylands.