Schedule May 22, 2018
Subtropical Turbulence and Clouds: From LES to Climate Models
Joao Teixeira (JPL)

Some of the biggest uncertainties in weather forecasts and climate models stem from the challenge of properly representing clouds and convection (thermally-driven movement) in the atmosphere. Clouds can significantly alter the Earth's albedo (reflectivity of the sun's rays back to space), and thus affect the heating that drives atmosphere dynamics. Part of the difficulty in representing the effects of clouds is that small-scale dynamics have unknown but significant impacts on large-scale dynamics, especially when the atmosphere and cloud structure change drastically over long distances. A simple model coupling cloud cover and sea surface temperature was developed. It compared well with atmospheric data derived from a collection of observations in a region of the Pacific Ocean where clouds transition from shallow (over cold ocean) to deep (over warm ocean). Next, convection was represented as a simple model of multiple rising plumes of warm air that could mix and entrain surrounding air in a random way. The model produced a realistic cloud transition compared to ship-based measurements over the same region of the Pacific Ocean. These results showed promise that simple models, which represent small-scale cloud dynamics, can be extended to large-scale climate models where small-scale features are underrepresented.

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