Lightning Activity and Meteorological Conditions Before, Duringand After the 2018 Wildfires : Analysis of SMHI Lightning Dataand Meteorological Variables from CERRA During the SummerMonths of 2017-201
Year: 2026
Type: dissertation
Abstract: Climate change is expected to increase the frequency and intensity of extreme weather events, including heatwaves, droughts and wildfire-favourable conditions. During the summer of 2018 Sweden experienced exceptionally warm and dry conditions, contributing to several large wildfire events. Several of the most severe wildfires in Ljusdal Municipality were initiated by lightning strikes during intense thunderstorms in July 2018. The aim of this study was to investigate and compare lightning activity and meteorological conditions during the summer months of 2017-2019 within the study area 61–62°N and 1516°E. Lightning data provided by the Swedish Meteorological and Hydrological Institute (SMHI) were analysed together with meteorological variables from the Copernicus European Regional ReAnalysis (CERRA). The study included both an annual comparison of lightning characteristics and meteorological conditions, as well as a detailed analysis of lightning discharges recorded during 12-14 July 2018. The results showed substantial differences between the studied years. Lightning activity increased from 538 recorded discharges in 2017 to 4348 in 2018 and 6239 in 2019. Summer 2018 was characterized by the highest mean temperature and the lowest relative humidity of the study period. Correlation analysis showed that Convective Available Potential Energy (CAPE) exhibited the strongest positive relationship with lightning activity, with the highest correlation coefficient observed in 2019 (r = 0.927). Relationships between lightning activity, temperature and relative humidity varied between years and had both positive and negative outcome. The study indicates that extensive lightning activity alone is insufficient to explain large wildfire development. Instead, the combination of lightning activity, high temperatures, low relative humidity and dry environmental conditions appears to have played a crucial role in the wildfire outbreak during the summer of 2018. The results highlight the importance of considering both convective activity and meteorological conditions when assessing future wildfire risk.
Author: Emilsson, Julia
Language: Swedish
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Climate action
Open Access status: green
OpenAlex ID: W7165976562