The wave turbopause

The wave turbopause is defined as the mesospheric altitude level where the temperature fluctuation field indicates a substantial increase in wave amplitudes in the vertical direction. The turbopause altitude is analyzed on the basis of four years of SABER data (2002-2005, Version 1.06). Substantial seasonal and latitudinal variations are found, with some interannual variability also present. Seasonal changes are annual at high latitudes, semi-annual at low latitudes, and a mixture of both at middle latitudes. Southern hemisphere data are similar as in the North if shifted by half a year. Latitudinal variations show a minimum in the tropics and two relative maxima at middle latitudes. The wave turbopause is found near to zero-wind lines or low-wind zones (zonal wind). It is compared to rocket and other measurements, and interesting similarities are obtained. The wave turbopause can also be found in the HAMMONIA GCM. A preliminary analysis shows results similar to those of the SABER measurements. (c) 2007 Elsevier Ltd. All rights reserved.