Abstract :
[en] Near-surface winds play a crucial role in the climate of Antarctica, but accurately quantifying and understanding their drivers is complex. They result from the contribution of two distinct families of drivers: the large-scale pressure gradient and surface-induced pressure gradients known as katabatic and thermal wind. The extrapolation of vertical potential temperature above the boundary layer down to the surface enables us to separate and quantify the contribution of these different pressure gradients in the momentum budget equations. Using this method applied to outputs of the regional atmospheric model MAR at a 3-hourly resolution, we find that the seasonal and spatial variability in near-surface winds in Adélie Land is dominated by surface processes. On the other hand, high-frequency temporal variability (3-hourly) is mainly controlled by large-scale variability everywhere in Antarctica, except on the coast. In coastal regions, although the katabatic acceleration surpasses all other accelerations in magnitude, none of the katabatic or large-scale accelerations can be identified as the single primary driver of near-surface wind variability. The angle between the large-scale acceleration and the surface slope is a key factor in explaining strong wind speed events: the highest-wind-speed events happen when the katabatic and large-scale forcing are aligned, although each acceleration, when acting alone, can also cause strong wind speed. This study underlines the complexity of the drivers of Antarctic surface winds and the value of the momentum budget decomposition to identify drivers at different spatial and temporal scales.
Funding text :
The authors appreciate the support of the University of Wisconsin\u2013Madison Automatic Weather Station Program for the dataset, data display, and information (NSF grant number 1924730). We acknowledge using data from the CALVA project and CENECLAM and GLACIOCLIM observatories. This work is part of the Katabatic project, AWACA project, and the POLARiso project. The MAR simulations were performed thanks to access granted to the HPC resources of IDRIS under the allocation 2022-AD010114000 made by GENCI. We acknowledge the work of Xavier Fettweis (Universit\u00E9 de Li\u00E8ge) in developing and maintaining the MAR model.This research has been funded by the Agence Nationale de la Recherche JCJC Katabatic project (grant no. ANR19-CE01-0020-01) awarded to Anais Orsi and by NSERC Discovery (grant no. DGERC-2021-00213). This work is also part of the AWACA project that has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 951596) and part of the POLARiso project that has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk\u0142odowska-Curie action (grant agreement no. 8410).This research has been funded by the Agence Nationale de la Recherche JCJC Katabatic project (grant no. ANR19-CE01-0020-01) awarded to Ana\u00EFs Orsi and by NSERC Discovery (grant no. DGERC-2021-00213). This work is also part of the AWACA project that has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 951596) and part of the POLARiso project that has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk\u0142odowska-Curie action (grant agreement no. 8410).
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