Upper ocean heat budget in the Gulf Stream Extension in two high resolution models and the influence of the Gulf Stream on Storm evolution

by LuAnne Thompson

Our research groups work on western boundary current interactions with the atmosphere is proceeding along two lines. In the first, we are examining the heat budget in two high resolution ocean models of the North Atlantic. One simulations consists of a hindcast of a one tenth of a degree POP simulation of the North Atlantic performed by Julie McClean from 1980 to the present. While the interannual variability of the Gulf Stream in the Extension and Recirculation, we hope to use the simulations to examine the relationships between heat and volume transport and the structure of the circulation and whether some components of the circulation are predictable from forcing fields. The second simulation is a one third of a degree assimilative simulation of the North Atlantic performed by MERCATOR in France that covers the altimetric observational period. While the model is not eddy resolving, it does reproduce the observed sea surface height fields owing to the assimilations, and it is possible to examine the heat and volume transport relationships in a more direct way.

The second aspect of our research involves the investigation of how the state of the Gulf Stream influences cyclogenesis in the atmosphere over head. While the state of upper level baroclinicity is important for the strength and path of storms in the North Atlantic, our hypothesis is that the position, strength and heat content of the Gulf Stream can also be important under certain conditions. To examine this hypothesis, we will be perform regional atmospheric simulations of storm evolution over the Gulf Stream Extension. Our plan is to identify several storms that evolve in the viscinity of the Gulf Stream by working closely with the data analysis team led by Kathie Kelly. We will then simulate the storm evolution using WRF (Weather Research and Forcasting Model) using boundary conditions from numerical weather prediction models (NCEP or ECMWF) while changing the surface temperature conditions to represent different Gulf Stream states. The goal will be to determine under what conditions, both atmospheric and oceanographic, the Gulf Stream can significantly impact the evolution of storms, and whether from this analysis, we can determine whether the Gulf Stream can have a long term impact on the atmosphere outside of the planetary boundary layer.