Global climatology of Convective Available Potential Energy (CAPE) and Convective Inhibition (CIN) in ERA-40 reanalysis

Abstract

Convective Available Potential Energy (CAPE) and Convective Inhibition (CIN) play a dominant role in convective precipitation, its genesis and intensity. A global climatology of CAPE and CIN is presented in terms of seasonal means, variances, and trends based on 44 years (1958–2001) of six-hourly ERA-40 reanalysis (European Centre for Medium-Range Weather Forecast ECMWF, T106 resolution). CAPE shows large values and high variability in the tropics with maxima over the continents; the seasonal changes are dominated by specific humidity. CIN shows large means and variability in the subtropics. Significant trends in CAPE and CIN give the following results: (i) In general, a CAPE increase is noted during all seasons while, in particular, in autumn CIN shows a decrease over continents. (ii) Splitting of the time series reveals a sign change in trend commencing at the end of the 70s; this is observed in parts of the tropical continents and North America. CAPE and CIN show trends of opposite sign with CAPE increasing in the first half and a decrease during the second half (and vice versa for CIN).