Comprehensive Lagrangian assessment of Canary Island precipitation moisture sources

Abstract

The Canary Archipelago, due to its location between the tropics and subtropics, represents a key region for studying precipitation moisture sources. This study provides a high-resolution (20 km) climatological analysis of the moisture sources for potential precipitation in the archipelago from 1985 to 2022, applying a dynamic downscaling methodology (WRF-ARW) and a Lagrangian approach considering the trajectories of potentially precipitating particles (FLEXPART-WRF model). The analysis differentiates between precipitation and non-precipitation days, western and eastern islands, and moisture transport above and below the trade wind inversion layer (at 900 hPa). Results indicate that the main moisture source for the archipelago is the North Atlantic (up to 74 % annually), and a crucial contribution comes from the northeast region of the islands, especially under prevailing trade wind conditions. During the summer, moisture from the African continent further enhances its contribution up to 16 % for the total moisture transported. The moisture pattern is more pronounced on days with precipitation, extending longitudinally towards the western Atlantic, and showing the largest positive anomalies during intense precipitation events. Notably, our findings highlight the strong contribution of moisture from the northeast above the inversion layer, even on non-precipitation days. Additionally, differences in precipitation moisture source patterns were observed between the eastern and western islands, with positive anomalies in the northern sector for the former and the western one for the latter, each associated with different circulation patterns.