"Mesosphere and Lower Thermosphere Summer Wind Variability over Nearly Two Decades at Middle and High Latitudes"

Winds at the mesosphere and lower thermosphere have been measured by partial reflection radars and specular meteor radars for almost two decades (2004-2021) over Germany and Norway (i.e., middle and high latitudes, respectively). These continuous wind measurements during this period are important to understand their long-term behavior. The zonal mean wind climatology displays an eastward wind during the winter months and a westward summer jet below ~85km at middle latitudes (~90km at high latitudes), above the mentioned height, an eastward wind jet is observed. In the meridional wind component, the southward summer jet display amplitudes between 4 and 5 times less intense than the westward jet. We studied the intensity of the summer jets, the long-term variability and the possible connection to external forcing (i.e. El Niño-Southern Oscillation, quasi-biennial oscillation and solar activity). We identify significant trends at middle latitudes in the monthly summer values of the westward summer jet calculated with 32 years of measurements. This trend suggests an increasing amplitude of the mean wind over the years, while at high latitudes the eastward jet shows an opposite behavior. On the other hand, the meridional component at middle latitudes shows a decreasing southward wind.