Global climatology and trends in convective environments from ERA5 and rawinsonde data

Mateusz Taszarek,Harold E Brooks,Mattia Marchio,John T Allen

doi:10.1038/s41612-021-00190-x

Abstract

Globally, thunderstorms are responsible for a significant fraction of rainfall, and in the mid-latitudes often produce extreme weather, including large hail, tornadoes and damaging winds. Despite this importance, how the global frequency of thunderstorms and their accompanying hazards has changed over the past 4 decades remains unclear. Large-scale diagnostics applied to global climate models have suggested that the frequency of thunderstorms and their intensity is likely to increase in the future. Here, we show that according to ERA5 convective available potential energy (CAPE) and convective precipitation (CP) have decreased over the tropics and subtropics with simultaneous increases in 0–6 km wind shear (BS06). Conversely, rawinsonde observations paint a different picture across the mid-latitudes with increasing CAPE and significant decreases to BS06. Differing trends and disagreement between ERA5 and rawinsondes observed over some regions suggest that results should be interpreted with caution, especially for CAPE and CP across tropics where uncertainty is the highest and reliable long-term rawinsonde observations are missing.

Highlights

Thunderstorms present a significant hazard to communities, agriculture, and infrastructure
A proxy of convective available potential energy (CAPE) is often considered, as it provides an apppffiffiffirffiffioffiffixffiffiiffiffimffiffiffiffiaffiffition to the theoretical maximum updraft speed (w 1⁄4 2 ́ CAPE) in convective clouds[11,12]
Convective available potential energy The climatological distribution of CAPE strongly reflects the availability of low-level moisture

Summary

INTRODUCTION

Thunderstorms present a significant hazard to communities, agriculture, and infrastructure. Our current understanding of future changes in convective environments induced by a globally warming climate is that large increases to low-level moisture (and CAPE) will result in the atmosphere being more conducive for severe thunderstorms[23,24,25,26,27] and heavy precipitation[28,29,30,31] These projections have large uncertainty with more recent studies indicating significant decreases (~15%) to lightning flash rate under global warming or mixed trends[32,33], in the tropics[29,34]. Results based on reanalyses should be always interpreted with caution, especially concerning thermodynamic instability and modeled precipitation where systematic errors are present[39,40]

RESULTS

DISCUSSION

METHODS