Climatological Aspects of Convective Parameters over Europe: A Comparison of ERA-Interim and Sounding Data

Abstract

Abstract We compare over 1 million sounding measurements with ERA-Interim reanalysis for the 38-yr period from 1979 to 2016. The large dataset allows us to provide an improved insight into the spatial and temporal distributions of the prerequisites of deep moist convection across Europe. In addition, ERA-Interim is also evaluated. ERA-Interim estimates parameters describing boundary layer moisture and midtropospheric lapse rates well, with correlation coefficients of 0.94. Mixed-layer CAPE is, on average, underestimated by the reanalysis while the most unstable CAPE is overestimated. Vertical shear parameters in the reanalysis are better correlated with observations than CAPE, but are underestimated by approximately 1–2 m s−1. The underestimation decreases as the depth of the shear layer increases. Compared to radiosonde observations, instability in ERA-Interim is overestimated in southern Europe and underestimated over eastern Europe. High values of instability are observed from May to September, out of phase with the climatological pattern of wind shear, which peaks in winter. From September to April, favorable conditions for thunderstorms occur mainly over southern and western Europe with the peak location and higher frequency shifting to central and eastern Europe from May to August. For southern Europe, the annual cycle peaks in September with high values of inhibition suppressing thunderstorm activity in July and August. The area with the highest annual number of days with environmental conditions favorable for thunderstorms extends from Italy and Austria eastward through the Carpathians and Balkans.