20-year LiDAR observations of stratospheric sudden warming over a mid-latitude site, Observatoire de Haute Provence (44°N, 6°E): Case study and statistical characteristics

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 1982-2001 period, which corresponds to 2629 daily temperature profiles. The characteristics of warming events are presented in terms of type of warming (major and minor), magnitude of warming, height of occurrence, day and period of occurrence 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 National Centre for Environmental Prediction (NCEP) reanalysis data. SSWs occur with a mean frequency of 2.15 events per winter season. The percentages 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 descent of stratopause layer by -6 to 6 km range. The height of occurrences of major SSW are distributed between 38 km and 54 km with magnitude in the 12.2-35.7 K temperature range, while the minor SSW appear in 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 and presented.