Do Mesoscale Convective Systems precipitation follows the Clausius-Clapeyron relationship?

Abstract

Floods related to heavy precipitation are common over Europe during both the warm and the cold seasons. In a way to better understand these heavy precipitation systems and their potential evolution in a warming climate, several studies investigated the dependency of precipitation extremes to temperature over Europe (e.g. Lenderink et al., 2008; Berg et al., 2013). It was found that the scaling of precipitation extremes can exceed the scaling expected from the Clausius-Clapeyron (CC) relationship, relating temperature to the water holding capacity of the atmosphere. While several potential explanations were proposed, a recent study (Lochbihler et al., 2017) noted the important role of large systems in determining this “super-CC” scaling over the Netherlands. Building on this study, we further investigate the role of Mesoscale Convective Systems (MCS) in determining the temperature precipitation relationship over Europe. The detection and tracking of MCSs is based on the recent Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG; Huffman et al., 2019) satellite precipitation climatology. We use the EUropean Cooperation for LIghtning Detection (EUCLID) lightning dataset to distinguish between stratiform (or shallow convective) and deep convective rain patches without introducing bias in precipitation intensity. We select the temperature upstream of the MCS tracks, as a proxy of the moisture source involved in the formation of MCS precipitation. MCS can display strong dynamical features such as the rear inflow jet or cold pools, of which the effects on precipitation as well as their changes with temperature are still unclear. It suggests that MCS precipitation may deviate significantly from the CC scaling. Additionally, the processes involved in MCS precipitation may differ depending on the stage of the MCS life cycle. We thus characterize the temperature dependency of MCS precipitation and their 2-D structure at different stages of their life cycle. This work contributes to better understanding the drivers of MCS precipitation and how these may evolve in a warming climate.