Assessing target areas for precipitating moisture source analysis of extratropical cyclones: An analysis based on case studies

Extratropical cyclones (ECs) play an important role in precipitation generation at mid-latitudes. EC circulation involves multiple precipitation-generating structures, raising questions regarding the origin of their moisture uptake. Our study aimed to identify the origin of precipitation using a Lagrangian approach by targeting EC characteristics in different regions. To achieve this goal, we focused on the 28 most intense ECs that affected the Iberian Peninsula (IP) in winter, with a detailed analysis of three cases, namely, Daniel, Elsa and Fabien, which occurred in December 2019. Our EC masking methodology defines target regions using the radius, warm conveyor belt (WCB) footprint stages, and a square root spiral contour centred on the cyclone, fitted to the decreasing mean sea level pressure field. Our results revealed that variations in the water budget radial target regions are driven by the intensity of moisture uptake over the spatial distribution. Furthermore, the moisture uptake patterns of the WCB ascent and outflow footprints closely resemble those of the central areas due to their geographical proximity. In the integral WCB uptake framework, the moisture gained from initial ascending particles within the inflow footprints effectively accounts for contributions from remote sources. Despite the broader precipitation inclusion, the spiral shape maintains systematic and efficient cyclone moisture dynamics.