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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.

Surface properties, such as roughness and vegetation, which vary both within and between urban areas, play a dominant role in determining surface–atmosphere energy exchanges. The turbulent heat flux partitioning is examined within a single urban area through measurements at four locations in Łódź, Poland, during August 2002. The dominant surface cover (land use) at the sites was grass (airport), 1–3-story detached houses with trees (residential), large 2–4-story buildings (industrial), and 3–6-story buildings (downtown). However, vegetation, buildings, and other “impervious” surface coverage vary within some of these sites on the scale of the turbulent flux measurements. Vegetation and building cover for Łódź were determined from remotely sensed data and an existing database. A source-area model was then used to develop a lookup table to estimate surface cover fractions more accurately for individual measurements. Bowen ratios show an inverse relation with increasing vegetation cover both for a site and, more significant, between sites, as expected. Latent heat fluxes at the residential site were less dependent on short-term rainfall than at the grass site. Sensible heat fluxes were positively correlated with impervious surface cover and building intensity. These results are consistent with previous findings (focused mainly on differences between cities) and highlight the value of simple measures of land cover as predictors of spatial variations of urban climates both within and between urban areas.