Precipitation in the Earth System: Global estimation, precipitation extremes relevant to hazards, and climate change

Precipitation is the input to the hydrologic cycle and affects the water and energy balance at the local, regional and global scales.  Precipitation extremes create hazards and endanger life, property and critical infrastructure.  Under global warming, precipitation is expected to change in complex ways, including the mean annual precipitation, the duration of wet and dry spells, the seasonality, and the frequency and magnitude of extremes.  In this talk, I will present recent results on two main aspects of precipitation: (1) global precipitation estimation from multi-satellite observations in places of the world that do not have ground measurements, with particular emphasis on preservation of extremes, and (2) assessment of the change of the space-time structure of storms under global warming.  In global precipitation estimation, we propose a new conditional generative diffusion model that combines the information from the instantaneous Passive Microwave (PMW) snapshots taken by Low Earth Orbit (LEO) satellites with the dynamical temporal information provided by GEO IR satellites, and show an impressive performance in capturing extremes and providing uncertainty quantification.  In assessing precipitation changes relevant to hazards, we analyze the cold-season precipitation over the western United States in long-term numerical simulations from the storm-resolving WRF model at 6 km and 1 h resolution in the historical period (1981-2020) and pseudo-future simulations for the 2041-2080 period, constrained by GCMs under the high emission RCP8.5 scenario. We demonstrate that global warming will induce a “sharpening” of storms both in time and space, meaning that a larger proportion of rain will fall over fewer wet hours and over smaller areas, amplifying hazard potential for flooding and post-fire debris flows.