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.

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