Atmospheric rivers (ARs) are filaments of enhanced moisture in the atmosphere, usually located in subtropical zones and mid-latitudes over oceanic areas. Enormous quantities of water vapor travel through these structures, so that precipitation, which can be very heavy, occurs when they make landfall.
This thesis presents a Lagrangian method to correctly compute the sources of precipitation in AR events. The methodology is applied to a pair of ARs that affected the Iberian Peninsula in the 1980s. The results are considered together with other more conventional approaches to study ARs, which makes us gain some insight on how water vapor is transported, and formulates interesting future research questions.