Evidence of Global Mean Increases in the Frequency of Daily and Sub-daily Heavy Precipitation

Speaker: Dr. Maria Chinita, University of Los Angeles and Dr. Mark Richardson, Colorado State University

Thursday June 24, 2021
12:00 PM US Pacific Time



In a warming climate and assuming moisture availability, heavy precipitation is expected to increase at approximately 7% per degree of warming according to the Clausius-Clapeyron relationship, whereas total global precipitation is capped at ~2% K by atmospheric energy balance constraints. Such disproportionality suggests that extreme events increase at the expense of moderate and light events.

In this seminar, we will present what is, to our knowledge, the first global analysis of frequency changes in hourly and daily heavy precipitation by exploiting the 1/4° spatial resolution of the latest ERA5 reanalysis. Our robust metric captures local changes across both wet and dry regions, and avoids several known statistical biases. We report that during 1989—2018, the event that occurred one hour per year in 1979—1988 increased in frequency by 71 [53—93, 2σ range] %, while the one day per year extreme event frequency increased by 44 [37—54] %. Our results replicate prior findings that relative frequency increases are larger for increasingly rare events and for the first time we quantify that the mean frequency increase is substantially greater over the global ocean than over global land.

We will also investigate the fidelity of our results by validating ERA5 against the Frequent Rainfall Observations on GridS (FROGS) daily database. Finally, we will discuss statistical issues that cause biases in trends of rare event frequencies, and show simple methods to identify and mitigate these biases.

Speaker’s Bio:

Dr. Maria Chinita completed her PhD at the University of Lisbon, Portugal in 2018, where she studied strongly stable boundary layers and turbulence decomposition of convective flows using Large-Eddy Simulations. She joined JIFRESSE in 2019 to work on the improvement of the planetary boundary layer representation in General Circulation Models by implementing and evaluating the Eddy-Diffusivity Mass-Flux parameterization. She is also interested in the study of extreme events which is the scope of this presentation.

Dr. Mark Richardson is a research associate at Colorado State University and JPL. He develops satellite cloud retrievals and has published on changes in temperature, precipitation and cloud properties, combining climate model output with satellite and in-situ data.