Intra-annual variations of spectrally resolved gravity wave activity in the upper mesosphere/lower thermosphere (UMLT) region

The period range between 6 and 480 min is known to represent the major part of the gravity wave spectrum driving mesospheric dynamics. We present a method using wavelet analysis to calculate gravity wave activity with a high period resolution and apply it to temperature data acquired with the OH* airglow spectrometers called GRIPS (GRound-based Infrared P-branch Spectrometer) within the framework of the NDMC (Network for the Detection of Mesospheric Change; https://ndmc.dlr.de, last access: 22 September 2020). We analyse data measured at the NDMC sites Abastumani in Georgia (ABA; 41.75.sup." N, 42.82.sup." E), ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research) in Norway (ALR; 69.28.sup." N, 16.01.sup." E), Neumayer Station III in the Antarctic (NEU; 70.67.sup." S, 8.27.sup." W), Observatoire de Haute-Provence in France (OHP; 43.93.sup." N, 5.71.sup." E), Oberpfaffenhofen in Germany (OPN; 48.09.sup." N, 11.28.sup." E), Sonnblick in Austria (SBO; 47.05.sup." N, 12.95.sup." E), Tel Aviv in Israel (TAV; 32.11.sup." N, 34.80.sup." E), and the Environmental Research Station Schneefernerhaus on top of Zugspitze mountain in Germany (UFS; 47.42.sup." N, 10.98.sup." E). All eight instruments are identical in construction and deliver consistent and comparable data sets.