[Eoas-seminar] MET Seminar by Fiaz Ahmed

[eoas-seminar at lists.fsu.edu]

MET faculty candidate seminar on Tuesday February 28th at 3:15 PM

Title:**Tropical precipitation and its environmental controls: 
reverse-engineering the physics from statistics

Speaker: Dr. Fiaz Ahmed (UCLA)

Abstract:
Tropical rain affects us all. The local effects of tropical rain include 
floods and droughts that disrupt large agrarian societies. The remote 
effects modify weather patterns even in the midlatitudes. To understand 
how tropical precipitation arises, one must study atmospheric 
convection—which ultimately generates rain—and its immediate 
environment. However, the convection-environment problem is confounded 
by fast timescales (a few hours), small spatial scales (a few km), and 
tight coupling between clouds and dynamics. Consequently, our climate 
model projections of future precipitation remain uncertain. In this 
talk, I present an approach in which space-borne precipitation data are 
used to build a simple physical model of tropical convection. This 
approach identifies (and helps construct) a cloud buoyancy measure from 
environmental thermodynamic variables. This buoyancy measure is the key 
to convection-environment relations; it explains land-ocean differences 
in precipitation statistics, improves theoretical understanding of 
tropical waves and helps diagnose process-level errors in climate 
models. However, the buoyancy measure falls short when predicting the 
magnitude of precipitation extremes. This deficiency is addressed using 
a Bayesian machine learning tool that helps fully describe the 
precipitation distribution. This talk will conclude with a 
forward-looking discussion about a data-driven, stochastic 
parameterization scheme to simulate rainfall variability in 
intermediate-complexity models.
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