Reduced lightning accompanying moderate rain and occasional thunderstorms
In the summer of 2021, Germany witnessed a significant drop in the number of lightning strikes compared to previous years. Nowcast, a Munich-based lightning tracking company, reported that on June 1 alone, there were 43,000 lightning discharges in Germany, marking the most recorded in a single day. However, this figure was 41,129 fewer than the same month in 2020.
Similarly, Aldis/Blids information service recorded 23,986 lightning strikes in July 2021, a significant decrease from the 41,129 strikes in July 2020. It's worth noting that Aldis/Blids only counts ground strikes, not cloud-to-cloud discharges.
The summer months from June 1 to July 31, 2021, saw a total of 394,000 lightning strikes in Germany, the lowest value in at least 15 years, according to Nowcast. This trend continued into August, with the German Weather Service reporting an average of 114 liters of rain per square meter in July 2021.
Meteorologist Nikolas Zimmermann from the weather service UBIMET attributed the low number of lightning strikes to the lack of large-scale thunderstorm systems in Germany this year. However, the exact reasons for this decrease remain unclear.
Research suggests that lightning frequency depends heavily on atmospheric conditions such as convection, cloud formation, and topography. Severe thunderstorms, which produce lightning, often cluster around mountain ranges and plains, influenced by complex orography as seen in regions like the Alps and surrounding areas in Europe including Germany.
Climate change impacts on lightning are complex and regionally variable. It is difficult to accurately predict changes in lightning strikes because simulating cloud microphysics (convection and ice formation) in climate models is challenging. Some regions may see increases, others decreases. For example, studies show a decrease in the number of lightning days per year globally or regionally, but on lightning-active days, there can be more intense lightning activity due to stronger convection and more cloud ice.
Air pollution also influences lightning frequency but with a threshold effect: particulate emissions can increase lightning up to a certain point, beyond which further pollution suppresses lightning. The COVID-19 pandemic in 2020-2021 led to changes in human activity and potentially reduced particulate air pollution in some regions, which might have influenced local atmospheric conditions affecting lightning frequency, although this is speculative without direct studies on Germany for that period.
More specific research or meteorological analyses would be required to explain lightning variation in Germany in summer 2021, such as weather pattern variability or atypical atmospheric conditions during that season. The general scientific understanding suggests lightning is affected by multiple interacting factors that can cause year-to-year variability.
Despite the decrease in lightning strikes during the summer months, the year 2021 might still surpass the 2020 record of 813,000 lightning strikes, as reported by Nowcast, with 563,000 strikes recorded as of August 8. Each lightning strike is counted only once, even if it has multiple discharges and flickers.
In May 2021, 118,000 lightning discharges were recorded, which is about 45% less than the average of the past 15 years. As the weather patterns shift and atmospheric conditions change, it will be interesting to see if the number of lightning strikes in Germany continues to increase in the coming months.
Weather-forecasting services reported a significant decrease in the number of lightning strikes in Germany during the summer of 2021 compared to previous years. Meteorologist Nikolas Zimmermann from weather service UBIMET attributed this drop to the lack of large-scale thunderstorm systems, suggesting that weather-forecasting could be crucial in understanding the factors behind lightning frequency.
