Knowing the temperature structure in height and time establishes the basis to understand the climate of the earth. At the IAP a method has been developed to measure temperature profiles and temperature variations due to waves in the whole altitude range from 1 to 105 km for the first time. Two different lidars (the potassium lidar and the RMR lidar ) and different methods of measuring temperatures are used. The seasonal variation of temperatures is still based on nighttime-only soundings since 2002. Regular soundings during night and day are performed since 2010.
Mean temperature profiles of the winter (November – January) and the summer (June, July) measurements are calculated and shown in the Figure below. The well-known temperature differences in the troposphere, i.e. high temperatures are found in summer and low temperatures are found in winter, proceed into the stratosphere. Above the stratopause the temperature gradient is much larger in summer (about - 4 K/km) as in winter (about -1 K/km). Accordingly, the summer mesopause is found at low altitudes (about 87 km) and its temperature is very low (<150 K). In contrast the winter mesopause is found at higher altitude (about 104 km) and is also about 15 K warmer than in summer. This phenomenon is called two-level-mesopause and is much more pronounced at polar latitudes .
A represantative seasonal variation of temperatures is obtained from applying a harmonic fit to the data. The height structure of the atmosphere showing the different layers is similarly represented in the winter/summer profiles and in the seasonal plot. The largest temperature changes are observed around the stratopause (40-50 km) and around the mesopause (85-105 km). In the middle mesosphere (65-75 km) temperatures are nearly constant throughout the year.
Dr. Michael Gerding
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