Severe Convective Storms across Europe and the United States. Part II: ERA5 Environments Associated with Lightning, Large Hail, Severe Wind, and Tornadoes

Mateusz Taszarek,Kimberly A Hoogewind,Tomáš Púčik,Harold E Brooks,John T Allen

doi:10.1175/jcli-d-20-0346.1

Abstract

AbstractIn this study we investigate convective environments and their corresponding climatological features over Europe and the United States. For this purpose, National Lightning Detection Network (NLDN) and Arrival Time Difference long-range lightning detection network (ATDnet) data, ERA5 hybrid-sigma levels, and severe weather reports from the European Severe Weather Database (ESWD) and Storm Prediction Center (SPC) Storm Data were combined on a common grid of 0.25° and 1-h steps over the period 1979–2018. The severity of convective hazards increases with increasing instability and wind shear (WMAXSHEAR), but climatological aspects of these features differ over both domains. Environments over the United States are characterized by higher moisture, CAPE, CIN, wind shear, and midtropospheric lapse rates. Conversely, 0–3-km CAPE and low-level lapse rates are higher over Europe. From the climatological perspective severe thunderstorm environments (hours) are around 3–4 times more frequent over the United States with peaks across the Great Plains, Midwest, and Southeast. Over Europe severe environments are the most common over the south with local maxima in northern Italy. Despite having lower CAPE (tail distribution of 3000–4000 J kg−1 compared to 6000–8000 J kg−1 over the United States), thunderstorms over Europe have a higher probability for convective initiation given a favorable environment. Conversely, the lowest probability for initiation is observed over the Great Plains, but, once a thunderstorm develops, the probability that it will become severe is much higher compared to Europe. Prime conditions for severe thunderstorms over the United States are between April and June, typically from 1200 to 2200 central standard time (CST), while across Europe favorable environments are observed from June to August, usually between 1400 and 2100 UTC.

Highlights

Observational records from lightning detection networks or severe weather reports produce straightforward but imperfect climatologies of severe convective storms, as presented in the first part of the study (Taszarek et al 2020a, hereafter particularly related to biases and inhomogeneity issues (Part I))
Expanding upon the climatological aspects of severe convective storms over Europe and the United States evaluated in the first part of the study (Part I), here we focus on collocated atmospheric environments and their spatial and temporal variability
Parcel parameters Consistent with prior studies, there is a relationship between increasing convective available potential energy (CAPE) and severity of hail and tornado events (Fig. 2a)

Summary

Introduction

Observational records from lightning detection networks or severe weather reports produce straightforward but imperfect climatologies of severe convective storms, as presented in the first part of the study (Taszarek et al 2020a, hereafter Part I). These data feature many spatial and temporal biases, and for some regions offer limited record length. In many parts of the world, severe weather reports are not even collected, which creates difficulties in constructing reliable climatologies. A typical practice has been to consider environmental proxies favorable to the development of severe thunderstorms and construct their climatologies (Johns and Doswell 1992; Griffiths et al 1993; Doswell et al 1996; Brooks et al 2003).

Objectives

Results

Conclusion