Lightning flashes are locally rare albeit hazardous events. Cloud-to-ground lightning strikes may injure or kill people and damage infrastructure or start wild fires. Having reliable climatologies of lightning thus aids the assessment of all these risks.
Despite this scarcity, generalized additive models (GAMs) succeed in producing a climatology of lightning occurrence for the eastern Alps and surrounding lowlands at an unprecedented resolution of 1km2 for each day of April through September with data from the Austrian lightning detection and information system (ALDIS) and the digital elevation model TanDEM-X. ALDIS provides data for eleven years 2010-2020. The GAM adds the effects of seasonality, jaggedness of the terrain, and seasonally varying effects of elevation and region, thus combining information from analysis cells sharing similar characteristics. Therefore the GAM approach enables more flexibility and the inclusion of more explanatory information than the commonly used "cell-count" method that allows only for smoothing over cells which are close in space and/or time to each other.
The results of the GAM climatology are summarised as follows: At the beginning of the season the probability of a cloud-to-ground discharge over 1km2 on a given day is typically less than 1% with a rapid increase in spring, followed by a plateau and a gentler tapering-off in fall. Probabilities are lower at high elevations early in the season but increase once their snow cover is gone. Regional patterns of lightning also vary with season with an overall southward shift later in the year but more complex details. Grid cells with jagged topography have a higher probability of lightning.
How to cite: Simon, T. and Mayr, G. J.: Daily-resolved lightning climatology of the eastern Alpine region at the kilometer scale, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-61, https://doi.org/10.5194/ems2022-61, 2022.