Impact of Global Warming on Gravity Wave Momentum Flux in the Lower Stratosphere

Abstract

Impacts of global warming on gravity wave (GW) momentum flux (MF) in the lower stratosphere are estimated by analyzing results of simulations we performed using a high-resolution coupled climate model. In the “doubled CO₂ climate” during the June-August period, a nearly uniform and isotropic increase in MF of 20-40% is obtained at 70 hPa as a result of an upward displacement of the tropopause. The geographical pattern of the largest enhancement of MF is generally coincident with changes in the tropospheric GW source. Eastward and westward components of MF both increase in relation to the enhanced source activity as well as to change in the tropopause height. However, the eastward component is preferentially filtered by the increased background westerly winds in the lower stratosphere. As a result, the net westward MF largely increases in the tropics and the southern mid-latitudes.