Precipitació i circulacions mesoescalars en zones d'orografia complexa

The orography of a region has a large impact on the precipitation and the circulation of the wind at all scales, from the microscale to the macroscale. However, the study the interactions between the relief and the atmosphere is difficult due to their singularity and complexity. This thesis intends to improve the knowledge of those interactions, with emphasis on microscale and mesoscale. To do this, several methodologies and data sources have been used to deal with each of the three parts in which this thesis has been divided. The first part characterizes the absolute extreme precipitation records in Spain on different temporal scales. Using all the records of the AEMET precipitation databases, the highest historical point-based rainfall values are presented for scales ranging from 10 minutes to 2 years. It has been stablished that these data are compatible with a power-law scaling R = a Db where R is the maximum rainfall record achieved during duration D. Finally, the regional and seasonal variability of the scaling law have been characterized. The results of this analysis show that the proximity to the sea and the orographic influence are key elements to achieve a record in Spain. However, the orography has less influence on short scales and higher influence in large scales. Winter microphysical precipitation and mountain circulations in the Cerdanya valley (Eastern Pyrenees) have been studied in the second part of this thesis using non-conventional instrumentation both remote sensing and in-situ measurements. In particular, data from a Parsivel disdrometer and from a Micro Rain Radar (MRR) measured during the experimental campaign Cerdanya-2017 has been analyzed. New methodologies for the analysis of this kind of data have been developed and applied. Having described the precipitation events occurred during the campaign, global precipitation for both the snow and rain have been analyzed from the microphysical perspective. The results in this part show the response of the precipitation profiles for different phenomena, for example a warm front passage or the existence of a decoupling between the snow and the low-level valley induced circulations. The third part studies the interaction of the low-level atmospheric circulation and the coastal orography on the Catalan coast. Specifically, the mesoscale ageostrophic reaction of the air have been identified as Coastally Trapped Disturbances (CTDs). CTDs may become a weather hazard for low-level aircraft operations on the Barcelona airport and may produce substantial economic losses. A climatology of CTDs in this area has been performed in order to characterize these phenomena, and the dynamic origin of the disturbances have been studied using scale analysis and examining their forcing mechanisms. Finally, the role of the diabatic heating on the development and duration of CTDs have been analysed in order to improve their future predictability. The results of these studies aim to contribute to a better understanding of the orographic interactions for both the precipitation and the mesoscale circulations in such a way they serve to eventually improve the precipitation estimates in complex orography areas and to make progress in the conceptual models and the numerical weather prediction.