Identification of favorable environments for thunderstorms in reanalysis data

Abstract

The relations between lightning occurrence over Europe from the EUCLID network (2008–2013) and
\nparameters derived from ERA-Interim reanalysis data were studied to increase the understanding of the
\nconditions under which thunderstorms form. The objective was to identify relevant factors beyond instability
\nand convective inhibition, in order to better model thunderstorms using numerical weather prediction or
\nclimate model data. It was found that latent instability is only required up to a certain amount of approximately
\n200–400 J kg-1 CAPE. For higher values of CAPE (∼ 800–2800 J kg-1), the relative frequency of lightning is
\nrather constant. Relative humidity in the low to mid-troposphere has a major influence on storm occurrence
\nwith low relative humidity strongly suppressing thunderstorm development. For an average 850–500 hPa
\nrelative humidity below 50%, the frequency of lightning decreases to below 15%, even when CIN is
\nnegligible and CAPE sufficient. A subtle dependency on wind shear was found in which two regimes of
\nhigher frequency of lightning were identified. For very weak and for high shear the probability was higher
\nthan for intermediate values of both deep-layer and low-level shear.