Low Level Jet Streams at the Sea Ice Edge - Numerical Simulations using WRF

Abstract

The goal of the presented thesis is to investigate the formation of low level jets at the sea ice edge. Differential heating creates very sharp fronts at the ice edge. A transversal circulation, initiated by altered pressure gradients, influences the speed of the geostrophic wind and therefore can create low level jets. \\ The Weather Research and Forecast Model (WRF) was used to simulate three different cases. An analysis of the geostrophic wind suggested that the ice edge jet simulated by \citet{groenaas_1999} is not forced by the ice edge but rather by a slowing down of the proximate flow. Similar results were obtained in a simulation of measurements by \citet{drue_2001}. The atmospheric situation in both cases was comparable. The large scale flow had the sea ice edge to the right and the thermal wind was directed in the opposite direction. However, the measurements did not contain a low level jet. Furthermore, a discrepancy regarding frictional processes over sea ice was revealed. The only measured ice edge jet by \citet{shapiro_1989} could not be reproduced. This case, however, showed a complex setting of the atmosphere and it was not clear if the forcing of the low level jet was only due to the ice edge. Future work will focus on idealized cases in order to increase the quality of ice edge jet predictions.