Heini Wernli
Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland


On the linkage between cloud physics and extratropical dynamics


There are several ways how clouds influence the weather. The obvious ways are that clouds produce precipitation and reduce solar surface radiation. A more subtle influence of clouds on weather comes from the latent heat release due to phase transitions of water in clouds. This energy input to the atmospheric circulation can have important consequences: latent heating, in particular in the so-called warm conveyor belt airstream, contributes to the intensification of extratropical cyclones, and it can modify Rossby waves, the jet stream and the formation of blocks in the upper troposphere. This presentation will explain the fundamentals how these cloud-dynamics interactions occur, and it will present results from two ongoing projects in my research group. These projects aim at quantifying (i) the effect of below-cloud microphysical processes (e.g., snow sublimation) on cyclones and the jet stream, and (ii) the role of cloud diabatic processes in warm conveyor belts for erroneous medium-range weather forecasts in Europe.


Time and Place

Tuesday September 4th, 11.15
Rossbysalen C609, Arrhenius Laboratory, 6th floor