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

Abstract

In this study we investigate convective environments and their corresponding climatological features over Europe and the United States. For this purpose, NLDN and ATDnet lightning data, ERA5 hybrid-sigma levels, and severe weather reports from ESWD and SPC Storm Data were combined on a common grid of 0.25° and 1-hour steps over a period 1979–2018. 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 mid-tropospheric 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 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 higher probability for convective initiation given 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 CST, while across Europe favorable environments are observed from June to August, usually between 1400 and 2100 UTC.

The damaging tornado in Luxembourg on 9 August 2019: towards better operational forecasts

“…Due to enhanced values of 0-1km stormrelative helicity (100-150m 2 s −2 ), the tornado potential was indeed considerable over parts of northern France, eastern Belgium and Luxembourg (Figure 4). Values above 100m 2 s −2 have been associated with significant tornadoes in Europe (Taszarek et al, 2017;Taszarek et al, 2020). However, it is important to underline the potentially large variability of low-level helicity on a temporal and/or spatial scale (Markowski et al, 1998), meaning that the area-averaged 0-1km storm-relative helicity value at 1300 utc shown in Figure 4 is possibly not representative for the in situ environment near the tornadic storm.…”

Climatology of Convective Storms in Estonia from Radar Data and Severe Convective Environments

“…Mesoscale environments of the severe convective storms are characterised by severe-storm predictors representing both thermodynamic and dynamical conditions. The severity of thunderstorms has been found to depend on CAPE and VWS [19,52,53]. Often some parameter characterising moisture abundance is included, like mixing ratio or precipitable water.…”

“…Nowadays, it is reasonable to use high-resolution model data from reanalyses for wind, moisture, and temperature fields for local and synoptic scale effects [19,51,54]. Previous studies have been using conditional statistics to differentiate between severe and non-severe events or environments.…”

“…Satellite observations can provide characteristics of convective clouds for extensive areas, but the data they provide are mostly very limited or not available for the higher midlatitudes [18]. Atmospheric reanalysis models such as European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 provide up to 30-kilometre resolution global climatologies of environmental conditions favourable for convective activity [19]. Based on these various datasets, several pan-European climatologies of thunderstorms have been constructed [20,21].…”

Evaluation of Precipitation in the Chinese Regional Reanalysis Using Satellite Estimates, Gauge-Based Observations and Global Reanalysis

“…Global reanalysis with high horizontal resolution is a milestone for climate researches. For example, the ERA5 global reanalysis with a 0.25-degree horizontal grid spacing released since 2018 introduced significant improvements in representing the atmosphere with much higher vertical and temporal resolutions compared to prior reanalyses (Zhang et al, 2019;Delhasse et al, 2020;Dullaart et al, 2020;Nogueira, 2020;Tarek et al, 2020;Taszarek et al, 2020). However, ERA5 performed unsuitable for trend analysis (Gleixner et al, 2020;Nogueira, 2020), and shows positive bias of temperature over complex topography, such as the Rocky Mountain area, possibly due to some processes not being accounted for in ERA5 (Tarek et al, 2020).…”