Role of post-tropical cyclones in the hydrological cycle of the northwestern Iberian Peninsula


Recommended citation: Pérez-Alarcón, A.; Fernández-Alvarez, J.C.; Sorí, R.; Liberato, M.L.R.; Trigo, R.M.; Nieto, R., Gimeno, L. (2023). Role of post-tropical cyclones in the hydrological cycle of the northwestern Iberian Peninsula. 2nd MedCyclones Workshop & 9th European Storm Workshop. Toulouse, France, 28-30 June 2023.


Tropical cyclones (TCs) formed in the North Atlantic (NATL) basin can influence the weather condition in western Europe after recurving northeastward. Generally, these TCs impact the European coast after undergoing an extratropical transition and, therefore, as post-TCs (PTCs). Recent works have projected a poleward expansion of the genesis area in the NATL basin under global warming. It is then expected an increasing frequency of TCs or PTCs crossing circa or over the western Europe coast. Therefore, this work examines the role of PTCs in the hydrological cycle in the northwestern Iberian Peninsula (NIP) from 1980 to 2018. The information on TCs was extracted from the HURDAT2 dataset from the US National Hurricane Center. The high-resolution Multi-Source Weighted–Ensemble Precipitation dataset was used to quantify the amount of rainfall contributed by PTCs. Our analysis revealed that 30 TCs (~5%) formed within the study period influenced the weather conditions in the NIP region. The monthly frequency showed that October and September were influenced by 13 and 10 PTCs, respectively, while August and November recorded the impacts of 5 and 2 TCs, respectively. The contribution of PTCs to the monthly precipitation totals from August to November accounted for approximately 4.2%. It is important to highlight that September registered the highest PTC rainfall contribution, which accounted for 7.1%. Likewise, the western and northern portions of the NIP recorded the highest PTC-related precipitation totals. TCs can also play a crucial role in the offset of drought episodes. In this line, by using the classification of drought categories for SPI values, we found that PTCs contributed to the ending of ~18% of the dry periods from July to October in the NIP. These findings could be useful for future studies on understanding the possible impacts caused by TCs or PTCs in this region in a warmer climate.