204E Oceanography

61 Route 9W - PO Box 1000

Palisades

NY

10964-8000

US

Phone: 

(845) 365-8527

ahs129@columbia.edu

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In the extratropical latitudes (where, for example, Columbia University is located) we have a fairly good understanding of the basic dynamical processes that control the atmosphere?s behavior. This understanding has two manifestations. With sophisticated numerical models, we can predict the extratropical weather fairly well, up to a week ahead or so. We also have much simpler mathematical models which, though not accurate enough to produce good weather forecasts, capture the basic dynamics of the atmosphere and can at least qualitatively simulate the important phenomena such as winter storms, fronts, waves in the jet stream, etc. These simpler models are derived as approximations to the full equations of atmospheric motion and energy. They form the core of our understanding and guide us as we analyze both observations and numerical simulations of the extratropical atmosphere.

The atmosphere behaves differently in the tropics than in the extratropics, and is less well understood. Weather forecasts are considerably less accurate in the tropics, and many of the largest uncertainties in our simulations of the global climate are related to gaps in our understanding of tropical atmospheric processes. In particular, we do not understand, in a wide range of circumstances, what controls where and when rain falls in the tropics. This lack of understanding and predictive capability is expressed by our lack of simple mathematical models for the tropics that combine economy and correctness as successfully as the simple extratropical models do.

My research aims to remedy this situation by developing and testing new simple mathematical models of the tropical atmosphere, using approximation methods broadly similar to those that have been so successful in the extratropics. We devise simplified equations that can be solved either analytically or with simple computer programs, but which still capture important aspects of the atmosphere?s behavior. In addition to its intrinsic value, this theoretical research has led us to a new method for using high-resolution, limited-area numerical models, which simulate tropical cloud systems in (almost) all their gory complexity, to address the question of what controls where and when it rains in the tropics. Lastly, because meteorology is fundamentally an observational science, I do spend some of my time analyzing observational data from the real atmosphere, in order to test our current theories or get ideas for new ones.

Some of my projects include:

• IRI Modeling/Prediction research group
• Applied Mathematics ( details )