Long-term trends and solar cycle variations of mesospheric temperature and dynamics

摘要

Mesospheric and stratospheric temperatures and winds from several stations in Germany are analyzed for long-term trends in 1988-2008. Emphasis is on upper mesosphere (87 km) hydroxyl (OH) temperatures at Wuppertal (51°N, 7°E) that agree favorably with satellite-borne observations from Sounding of the Atmosphere Using Broadband Emission Radiometry and a twin OH instrument at HohenpeiBenberg (48°N, 11°E) that is operational since 2003. The two twin stations yield a combined data set with 80 time coverage suitable for high time resolution analyses. Annual mean temperatures at Wuppertal show a long-term trend of —0.23 K/yr and a solar flux sensitivity of 0.035 K/solar flux unit. Trend analysis of monthly mean temperatures yields substantial variations from one month to another, between 0 and —0.6 K/yr, hence questioning the value of seasonal mean trends. The OH temperatures have a well-known characteristic form of seasonal variation. This form changes during the 21 years of observation. The changes are compared to modifications of the summer length in the stratosphere and are interpreted as dynamics/circulation changes extending to the uppermost parts of the middle atmosphere.