Wave propagation in the 1999–2000 Arctic early winter stratosphere

Abstract

Stratospheric wave propagation during the unusually cold NH early winter 99–00 is studied and compared to the recent cold winters of 94–95, 95–96 (the previous coldest NH winter) and 96–97. EP fluxes reveal less wave activity entered the stratosphere in 95–96 and 99–00, substantial temperature decreases during long periods of little wave activity in 94–95 and 99–00, and little wave propagation into the upper stratosphere in Nov 99–Jan 00 and Nov 95–mid‐Jan 96. 2‐D and 3‐D EP fluxes for 95–96 and 99–00 show both that wave activity was inhibited from propagating upward and poleward through the middle stratosphere until mid–Jan, and there was large horizontal propagation of wave activity in the middle and lower stratosphere during Nov and Dec. Thus, both less wave activity entering the stratosphere, and a background structure that prevented wave activity from propagating into the upper stratosphere, were important factors in producing unusually cold early winters in 95–96 and 99–00.