School of Meteorology

The rain is askew: changes in the distributions of rain and vertical velocity

Dr. Angeline Pendergrass
Advanced Studies Program
Post-Doctoral Research Fellow
NCAR

09 March 2015, 2:00 PM

National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

As the planet warms, climate models predict that rain will become heavier and less frequent, and circulation will weaken. In this talk I’ll tell you about my work looking at how the distribution of rain (in terms of intensity and frequency) and the corresponding distribution of vertical velocity with warming.

To quantify the distribution of rain, we focus on daily precipitation accumulation from climate models. These models have a wide range of responses to global warming, especially at the extreme end of the distribution. In order to interpret this range of responses, we introduce shift and increase modes of change of the distribution. These capture the response of the entire distribution well in some models, while other models also have an extreme mode, isolated at the heaviest rain rates.

With two heuristic models, we show how changes in moisture and vertical velocity distributions can affect the distribution of rain. An increase in skewness of the vertical velocity distribution is crucial for explaining the change in the distribution of rain, particularly the decrease in the total number of rain events.

In this talk you’ll see a few things we’ve learned about how circulation changes by approaching the problem from the perspective of the distribution of rain. Looking ahead, there is still work to be done strengthening the global-scale understanding of rain and how it changes with warming, and also building on it to increase our knowledge about regional precipitation change by incorporating dynamical perspectives.

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