The impact of ocean–atmosphere coupling on heavy precipitation events over eastern Adratic and Dinaric Alps

The Adriatic region is one of the rainiest areas in Europe, particularly its coastal mountainous region. This area is often affected by severe weather events like heavy rainfall and flash floods, which pose a severe risk to people and property. Air-sea interactions play a significant role in this region, particularly in the autumn when heavy precipitation events (HPEs) are frequent, and the gradients are high between the sea-surface temperature (SST) and atmospheric temperature.

Atmosphere-only regional climate models (RCMs) are forced by SST as a lower boundary condition, which comes from reanalysis or global models. These models typically have a much lower resolution than the atmosphere-only RCM. On the other hand, regional atmosphere-ocean coupled models (RAOCMs) explicitly resolve air-sea interactions at high resolutions resulting in improved cyclogenesis and precipitation.

Our objective is to assess the impact of ocean-atmosphere coupling on heavy precipitation events that occurred during the first HyMeX Special Observation Period from 5 September to 6 November 2012. We focus on the six intensive observation periods (IOPs) during which heavy precipitation events affected the eastern Adriatic region. Additionally, we assess the performance of the coupled simulations in representing heavy and extreme precipitation at climatological scales.

To achieve this, we use the evaluation atmosphere-only RCMs and RAOCMs simulations from the Med-CORDEX framework. As a reference dataset, we use the precipitation analysis system MESCAN-SURFEX, available at 5.5 km resolution every 6 h, and the rain gauge data from the local observational networks. The main verification method for the HPEs is the quality object-based measure SAL which takes into account the structure (S), the amplitude (A), and the location (L) of the precipitation field. For the climatological scale, we focus on a range of heavy and extreme precipitation indices.