Partitioning of Large-Scale and Local-Scale Precipitation Events by Means of Spatio-Temporal Precipitation Regimes on Corsica

Isabel Knerr,Jörg Bendix,Sébastien Santoni,Emilie Garel,Frédéric Huneau,Katja Trachte

doi:10.3390/atmos11040417

Abstract

The island of Corsica in the western Mediterranean is characterized by a pronounced topography in which local breeze systems develop in the diurnal cycle. In interaction with the large-scale synoptic situation, various precipitation events occur, which are classified in this study with regard to their duration and intensity. For this purpose, the island was grouped into five precipitation regimes using a cluster analysis, namely the western coastal area, the central mountainous region, the southern coastal area, the northeast coastal area, and the eastern coastal area. Based on principal component analysis using mean sea level pressure (mslp) obtained from ERA5 reanalysis (the fifth generation of the European Centre for Medium-Range Weather Forecasts, ECMWF), six spatial patterns were identified which explain 98% of the large-scale synoptic situation, while the diurnal breeze systems within the regimes characterize local drivers. It is shown that on radiation days with weak large-scale pressure gradients, pronounced local circulations in mountainous regions are coupled with sea breezes, leading to a higher number of short and intense precipitation events. Meridional circulation patterns lead to more intensive precipitation events on the eastern part of the island (30% intensive events with meridional patterns on the east side compared to 11% on the west side). On the west side of Corsica, however, coastal precipitation events are seldom and less intense than further inland, which can be attributed to the influence of the topography in frontal passages.

Highlights

Achieving a proper knowledge of precipitation variability in space and time poses many challenges, as precipitation behaves differently on different scales
Our study focuses on the Island of Corsica which is located in the central western Mediterranean between 41◦ 22‘ N and 43◦ 01‘ N latitude and 8◦ 33‘ E and 9◦ 34‘ E longitude (Figure 1)
We investigated precipitation events in different regions on the mountainous island of Corsica, and divided them into locally and large-scale induced events with regard to their drivers

Summary

Introduction

Achieving a proper knowledge of precipitation variability in space and time poses many challenges, as precipitation behaves differently on different scales. Atmosphere 2020, 11, 417 orography on the area of formation and on the intensity and sums of precipitation was found [3,4] It was shown by [5], for instance, for two heavy precipitation events in Taiwan, that the synoptic situation overlapped the diurnal breeze effects, but that the pronounced topography of the island had a large influence on the spatial variation of the distribution of the precipitation totals. It was pointed out by [1] that meso- and microscale systems in the Mediterranean area are important for precipitation formation

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Discussion

Conclusion