Long period/large scale oscillations of temperature during the DYANA campaign
Résumé
During the DYANA campaign (January-March 1990) vertical temperature profiles were measured in the middle atmosphere above 11 rocket and four lidar stations in the northern hemisphere. Strong temperature variations were observed, especially at the medium to high latitude stations. Time series analysis was applied, and most oscillations were found to be quasi-periodic only, and restricted to certain altitude levels. Solely the longest periods (>4 weeks) and the shortest periods (around 5 days) were consisterrtly observed in the whole altitude regime, and were, therefore, further analysed. These temperature variations were found to be compatible with the assumption that the Quasi-Stationary Planetary Wave No. 1 (QSW 1) of the CIRA 1990 Model Atmosphere was modulated with the respective periods. Especially close similarity of the vertical phase structures was obtained. The amplitudes measured were, however, much larger than those of the model, and hence some amendment to the model may be appropriate. The importance of QSW 1 modulation appears to be considerable, as more than 50% of the temperature variance could be ascribed to it. The DYANA results were checked by an analysis of respective data from two other campaigns (Winter Anomaly campaign, 1976, and MAP/WINE campaign, 1984). Essentially the same results were obtained. Considering the strength of QSW 1 control, the midwinter middle atmosphere shows itself to be quite strongly and persisterrtly structured in both the vertical and horizontal directions. This applies to all parts of the stratosphere and mesosphere.