Midlatitude Synoptic Systems

Midlatitude synoptic systems produce most of the precipitation in midlatitudes through forced ascent. The cloud structures associated with these systems are extensive and comprise a rich mixture of convective, layered, and stratiform types, which have important effects on the energy and water balances in midlatitudes. Synoptic systems in midlatitudes are responsible for extreme modifications of the planetary boundary layer and intense interactions with the ocean. The combination of EOS instruments with assimilated data products, models, and in situ data will provide a unique opportunity to better understand these important weather systems and their role in climate.

Currently we are working with ERS-1 data to investigate the usefulness of these data in better defining the surface wind field variations associated with midlatitude synoptic systems, how these wind variations affect heat fluxes, and how these surface winds and fluxes compare with those produced by the current generation of weather prediction and climate models. We show below the surface pressure, SSM/I wind speed, and ERS-1 wind vectors associated with a midlatitude system . Next we show the surface winds from the ECMWF analysis and the surface wind analysis obtained by an optimal combination of our planetary boundary-layer model winds and the wind data from ERS-1 . The model and ERS-1 data produce a much better definition of the shear and convergence near the cold front and near the low pressure center. These wind differences have a significant influence on the surface fluxes and on the convection that is associated with the surface wind convergence along the front and in the center of the low