Heavy convective and stratiform precipitation and their links to atmospheric circulation

Precipitation in Central Europe can be classified as stratiform or convective based on its origin. Heavy convective precipitation is associated with intense storms, develops rapidly in localized areas, and can cause flash floods. In contrast, heavy stratiform precipitation is linked to longer-lasting, less intense rainfall events that may lead to large-scale flooding. These two types of precipitation also differ in their causal conditions, such as atmospheric circulation patterns and thermodynamic properties.

This study analyses heavy precipitation using time series from 19 observation stations across the Czech Republic for the period 1982–2021. An algorithm based on SYNOP reports was applied to classify precipitation totals as either convective or stratiform. Days with heavy precipitation (totals exceeding the 90th percentile) were assigned a circulation type using the Jenkinson & Collins (1977) method. This approach identifies 27 circulation types based on three indices: flow direction, strength, and vorticity.

The circulation types associated with heavy precipitation vary by season, precipitation type, and station location. Across all seasons, heavy precipitation is predominantly linked to cyclonic circulation and directional types with westerly and northerly flow components. In summer, heavy convective precipitation is additionally associated with anticyclonic conditions and unclassified patterns.

As climate change may significantly alter the atmospheric conditions driving heavy precipitation, understanding these phenomena and projecting their future behaviour is essential. To achieve this, the regional climate model ALADIN-CLIMATE/CZ operated by the Czech Hydrometeorological Institute will be used to evaluate the future relationship between heavy convective and stratiform precipitation and atmospheric circulation.