How much of precipitation over the Euroregion Galicia – Northern Portugal is due to tropical-origin cyclones?: A Lagrangian approach

This study analyses the contribution of the tropical-origin cyclones (TCs) to monthly rainfall amounts in the Euroregion Galicia–Northern Portugal (EG-NP) from 1980 to 2018, while simultaneously determines the moisture sources that generate this TCs-related precipitation over the EG-NP region. We quantified the amount of rainfall contributed by TCs using the high resolution Multi–Source Weighted–Ensemble Precipitation dataset, and the identification of the sources of moisture was performed by applying a Lagrangian diagnostic method. The EG-NP region was impacted by 30 TCs during the study period, distributed from August to November, with September and October showing the highest frequency, with 10 and 13 TCs respectively. Mostly, TCs influenced the study region after undergoing an extratropical transition, however, a few well know events, such as Ophelia (October 2017) and Leslie (October 2018) still impacted with hurricane category 1 on the Saffir-Simpson wind scale. On average, the TCs-related precipitation accounted for ∼4.2% of mean rainfall from August to November, although September with ∼7.1% exhibited the largest contribution. Likewise, the highest TCs-related rainfall was found towards the western and northern region of EG-NP. Furthermore, during the passage dates, TCs obtained most of the precipitating moisture (∼75%) from the subtropical North Atlantic Ocean. On the other, the traditional climatological moisture sources for the EG-NP came from the Atlantic coast of Morocco and the Iberian Peninsula during August and October, from the western Mediterranean Sea in September, and a weak pattern from the Cantabrian Sea in November. These findings could be useful for future studies on understanding the possible impacts caused by TCs in this region in a warmer climate. •5% of tropical-origin cyclones (TCs) impacted the Euroregion Galicia–Northern Portugal.•TCs generally influenced the region after undergo the extratropical transition.•TCs-related rainfall accounted for ∼4.2% of mean rainfall from August to November.•The subtropical North Atlantic Ocean acted as the main moisture source.