Atmospheric Rivers at the Kerguelen Islands: A Story through Weather Types
Résumé
This study analyzes the interrelationship between atmospheric rivers (ARs) and weather types (WTs) on the Kerguelen Islands, in the southern Indian Ocean, over the last 40 years. Their respective characteristics and impacts as well as their influence on precipitation and temperature are investigated using ERA5 reanalyses and in situ data. Results show that, even though they can occur throughout the year, ARs are mostly associated with four WTs, which have a strong influence on preferential AR direction and landfalling location. These WTs correspond to those favoring northerly or northwesterly anomalies promoting moisture export from the subtropical latitudes. Weather type influence on daily precipitation and temperature is highly variable with the relationship depending on their co-occurrence, or lack thereof, with AR events. Depending on their orientation, ARs have different impacts on the local climate and are responsible for a majority of the strongest east–west precipitation gradients. Significance Statement The Kerguelen Islands, hosting the largest French glacier, are experiencing atmospheric drying which is causing the latter to retreat. Unstudied in this region, atmospheric rivers are expected to significantly impact the islands’ precipitation variability. Here, we show that these atmospheric rivers, channeling moisture export from the subtropics, are responsible for the most intense precipitation and warm events over Kerguelen. Their effects on precipitation and temperature variability strongly depend on their landfalling location, their direction, and their local interactions with the complex topography. This study underscores atmospheric rivers’ vital role in local humidity variability, indicating a need for further long-term research on their evolution in Kerguelen.
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