The influence of atmospheric circulation on the occurrence of hail in the North German Lowlands

Abstract

The atmospheric circulation and thermal conditions in the troposphere were analysed to identify the situations which are conductive to hail development in the North German Lowlands. They were established on the basis of the data obtained from the US National Center for Environmental Prediction/US National Center for Atmospheric Research Reanalysis database, and they included sea level pressure, 500 hPa geopotential height, the temperature at 850 and 500 hPa and HYSPLIT backward trajectories model. Daily information about hail occurrence in 16 selected stations was received from Deutscher Wetterdienst database and it covered the years 1951–2010. It was found that hail in the studied area was connected with large negative anomalies of the sea level pressure over Scandinavia and, consequently, the northwestern direction of air mass influx. In some cases, hail was associated with the northern influx, with strong negative anomalies of the temperature, and with positive anomalies of the temperature during the southern influx of air masses.