Perspectives on Convective Rainfall From Passive and Active Microwave Sensors

Abstract

Understanding the type of rainfall is crucial for hydrological modeling, large-scale circulation simulations, and severe weather alerts. The present study offers an insight into the consistency of convective rain observations from spaceborne active (KuPR)/passive (GPM Microwave Imager [GMI]) microwave sensors and ground-based radar network (GV-MRMS). Findings over CONUS suggest a strong agreement in convective rain detection between the three products for the deep convective regime—the storms exceeding 10 km in height and characterized by low brightness temperature at ice-sensing channels. In contrast, a poor agreement occurs for shallow-broken rain systems with storm tops below 5 km. Compared to the GV-MRMS product, GMI and KuPR tend to classify shallow-broken rain as convective. Globally, at the midlatitudes, GMI recognizes less than 20% of KuPR-detected convective rain, while showing a better agreement in the tropical regions. Linear trends of GMI and KuPR convective rain, calculated for the period 2014–2023, reveal agreement in cold (ice phase present in the hydrometer column) and disagreement in warm (no ice phase present) rain cases, with −0.022 (GMI) and −0.019 (KuPR) mm day⁻¹ decade⁻¹ for cold and −0.010 (KuPR) and 0.002 (GMI) mm day⁻¹ decade⁻¹ for warm rain, respectively. Trends observed over the ITCZ in the mid and east Pacific Ocean oppose those over the west Pacific and tropical Atlantic Ocean. All variations are successfully linked to the environmental conditions, known to reflect atmospheric convective preference and offer a valuable proxy to the users.