20-year LiDAR observations of stratospheric sudden warming over a mid-latitude site, Observatoire de Haute Provence (OHP; 44° N, 6° E): case study and statistical characteristics
1Laboratoire de l'Atmosphère et des Cyclones, UMR 8105 CNRS/Université/Météo-France, Université de LaRéunion, Messag 9 BP 1751, Saint Denis, Réunion Island, France
2National Atmosphere Research Laboratory, Tirupati, Andhra-Pradesh, India
3National Laser Centre, Council for Scientific and Industrial Research (CSIR), P.O. Box 395, Pretoria 0001, South Africa
4Service d'Aéronomie, IPSL, UMR CNRS, Paris, France
Abstract. The present study delineates the characteristics of Stratospheric Sudden Warming (SSW) events observed over the Observatoire de Haute Provence (OHP: 44° N, 6° E). The study uses 20 years of Rayleigh LiDAR temperature measurements for the period, 1982–2001, which corresponds to 2629 daily temperature profiles. Characteristics of warming events, such as type of warming (major and minor), magnitude of warming, height of occurrence and day period of occurrence are presented with emphasis on wave propagation and isentropic transport conditions. The major and minor warming events are classified with respect to temperature increase and reversal in the zonal wind direction in the polar region using reanalysis data from the National Centre for Environmental Prediction (NCEP). SSWs occur with a mean frequency of 2.15 events per winter season. The percentage of occurrence of major and minor warming events are found to be ~23% and ~77%, respectively. The observed major and minor SSW is associated with a descent of the stratopause layer by −6 to 6 km range. The heights of occurrences of major SSWs are distributed between 38 km and 54 km with magnitudes in the 12.2–35.7 K temperature range, while minor SSW occurrences appear in the 42–54 km range, closer to the usual stratopause layer (~47 km) and with a slightly larger range of temperature magnitude (10.2–32.8 K). The observed major and minor events are examined in connection with Quasi-Biennial Oscillation (QBO) phases.