Doutoramento em Ciências da Terra e do Espaço
Study of different atmospheric environments associated to storms development in the Madeira Island
Flavio Tiago do Couto

Orientação: Rui Paulo Vasco Salgado, Maria João Tavares da Costa & Véronique Ducrocq

The study aims to improve the understanding about different atmospheric environments leading to the development of storms associated with heavy precipitation in Madeira Island. For this purpose, four main goals have been considered: 1) To document the synoptic and mesoscale environments associated with heavy precipitation. 2) To characterize surface precipitation patterns that affected the island during some periods of significant accumulated precipitation using numerical modelling. 3) To study the relationship between surface precipitation patterns and mesoscale environments. 4) To highlight how the PhD findings obtained in the first three goals can be translated into and operational forecast context. Concerning the large scale environment, precipitation over the island was favoured by weather systems (e.g, mesoscale convective systems and low pressure systems), as well as by the meridional transport of high amount of moisture from a structure denominated as “Atmospheric River”. The tropical origin of this moisture is underscored, however, their impact on the precipitation in Madeira was not so high during the 10 winter seasons [2002 – 2012] studied. The main factor triggering heavy precipitation events over the island is related to the local orography. The steep terrain favours orographically-induced stationary precipitation over the highlands, although maximum of precipitation at coastal region may be produced by localized blocking effect.

These orographic precipitating systems presented different structures, associated with shallow and deep convection. Essentially, the study shows that the combination of airflow dynamics, moist content, and orography is the major mechanism that produces precipitation over the island. These factors together with the event duration act to define the regions of excessive precipitation. Finally, the study highlights two useful points for the operational sector, regarding the meridional water vapour transport and local effects causing significant precipitation over the island.