Temperature trends in the middle atmosphere as seen by historical Russian rocket launches: Part 2, Heiss Island (80.6°N, 58°E)

Long-term changes of the temperature of the middle atmosphere are investigated using a data bank obtained by Russian rocketsondes at Heiss Island (80.6°N, 58°E). The major interest of the data series is that it is one of the longest and uninterrupted records obtained at high latitudes in the northern hemisphere over 25 years, from 1969 to 1994. Previous estimates using this dataset has shown the largest trends. The revised analysis performed here took into account all possible discontinuities in the data series, such as a change in the time-of-measurement, T0, and in the type of sensor. For this purpose, some data were filtered out, and a statistical model based on multiple regression analyses included step functions to take into account such discontinuities. The temperature responses to different sources of variability (solar activity, volcanic aerosols) were retrieved for summer and winter periods. The response to the 11-year solar cycle in the winter period is found to be largely positive in the stratosphere (+4 K) and largely negative in the mesosphere (-8 K), with a smaller and opposite response in summer. This response depends on the phase of the QBO, as already shown by previous studies. The response to volcanic aerosols is found to be significantly positive in the upper mesosphere, in good agreement with numerical simulations and with observations above France. The long-term trend resulting from this reanalysis indicates a cooling of the middle atmosphere, increasing with altitude from -2 K/decade at 40 km to a maximum of -6 K/decade around 65 km. This result is slightly larger than the trend observed at mid-latitude but quite smaller than previous estimates