4:25 PM - 4:40 PM
[ACG33-15] Influence of mid-latitude Sea Surface Temperature Fronts on the Atmospheric Water Cycle and Storm Track Activity
Keywords:SST front, Aqua planet experiment, Surface turbulent heat fluxes, Atmospheric water cycle, Diabatic heating, Storm track
The climatological mean turbulent air-sea sensible and latent heat exchange maximizes along midlatitude sea surface temperature (SST) fronts that tend to anchor midlatitude storm tracks. While the sensible heat exchange can be directly related to the forcing of low-level baroclinicity along the SST fronts, the air-sea moisture exchange associated with the latent heat flux and precipitation along the SST fronts must have a profound impact on the atmospheric water cycle with ramifications for the intensification of atmospheric cyclones and thus storm track intensity.
We investigate this influence of the SST front on the atmospheric water cycle using an atmospheric general circulation model in an aqua-planet configuration, where we vary the latitude of a zonally symmetric midlatitude SST front. We find that the midlatitude atmospheric water cycle responds through distinct changes in surface latent heat fluxes, precipitation, as well as atmospheric moisture fluxes that follow the position of the SST front. The tropical latitudes, however, remain largely unchanged irrespective of the position of the midlatitude SST front. While the moisture flux in the tropical latitudes is determined by the mean flow components, the mid and higher latitudes are dominated by the eddy moisture flux that is shifted with the position of the SST front.
The convergence of eddy moisture transport in the mid-latitudes yields precipitation bands near the SST front. The diabatic heating associated with this condensation generates available potential energy that can subsequently contribute to the development of baroclinic eddies. Along the SST front, the diabatic generation of eddy available potential energy contributes around 20% (40%) in winter (summer) to the overall conversion to eddy kinetic energy. Thus, the SST front not only controls the water cycle but also anchors the storm track through the associated diabatic heating.
We investigate this influence of the SST front on the atmospheric water cycle using an atmospheric general circulation model in an aqua-planet configuration, where we vary the latitude of a zonally symmetric midlatitude SST front. We find that the midlatitude atmospheric water cycle responds through distinct changes in surface latent heat fluxes, precipitation, as well as atmospheric moisture fluxes that follow the position of the SST front. The tropical latitudes, however, remain largely unchanged irrespective of the position of the midlatitude SST front. While the moisture flux in the tropical latitudes is determined by the mean flow components, the mid and higher latitudes are dominated by the eddy moisture flux that is shifted with the position of the SST front.
The convergence of eddy moisture transport in the mid-latitudes yields precipitation bands near the SST front. The diabatic heating associated with this condensation generates available potential energy that can subsequently contribute to the development of baroclinic eddies. Along the SST front, the diabatic generation of eddy available potential energy contributes around 20% (40%) in winter (summer) to the overall conversion to eddy kinetic energy. Thus, the SST front not only controls the water cycle but also anchors the storm track through the associated diabatic heating.