The Effects of Large-Scale Orography on Storm Tracks

Abstract:

The Northern Hemisphere storm tracks exhibit dramatic zonal variations with the topography, with the synoptic eddy activities peaked in the North Pacific and the North Atlantic. In this study, the effects of large-scale orography (i.e. Tibet Plateau) on the zonal structure of the storm tracks are investigated by carrying out idealized numerical experiments with the GFDL dynamical core. In the experiment with a zonally uniform diabatic heating and a local Gaussian-shape orography to simulate the effect of Tibet Plateau, a local storm track similar to that in the North Pacific is observed in the downstream region. The energy budget analysis of synoptic eddy shows that the orography induced stationary eddy can efficiently enhance the low-level baroclinicity in the downstream region, which results in more baroclinic eddy generation and a locally enhanced storm track. Sensitivity studies are also carried out to investigate the dependence of the above results to the position and the length-scale of the Gaussian mountain. Our study shows that the intensity of the storm track gets stronger when the position of the large-scale topography is displaced more equatorward. The stronger synoptic eddy activity mainly attributes the stronger baroclinic generation and the weaker EKE conversion due to eddy–eddy interactions response to topography.