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Open AccessArticle

Flow Regimes and Föhn Types Characterize the Local Climate of Southern Patagonia

Institut für Geographie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
Author to whom correspondence should be addressed.
Atmosphere 2020, 11(9), 899;
Received: 8 July 2020 / Revised: 16 August 2020 / Accepted: 20 August 2020 / Published: 25 August 2020
(This article belongs to the Special Issue Climatological and Hydrological Processes in Mountain Regions)
The local climate in Southern Patagonia is strongly influenced by the interaction between the topography and persistent westerlies, which can generate föhn events, dry and warm downslope winds. The upstream flow regime influences different föhn types which dictate the lee-side atmospheric response regarding the strength, spatial extent and phenomenology. We use a combination of observations from four automatic weather stations (AWSs) and high-resolution numerical modeling with the Weather Research and Forecasting (WRF) model for a region in Southern Patagonia (48° S–52° S, 72° W–76.5° W) including the Southern Patagonian Icefield (SPI). The application of a föhn identification algorithm to a 10-month study period (June 2018–March 2019) reveals 81 föhn events in total. A simulation of three events of differing flow regimes (supercritical, subcritical, transition) suggests that a supercritical flow regime leads to a linear föhn event with a large spatial extent but moderate intensity. In contrast, a spatially limited but locally strong föhn response is induced by a subcritical regime with upstream blocking and by a transition regime with a hydraulic jump present. Our results imply that the hydraulic jump-type föhn event (transition case) is the most critical for glacier mass balances since it shows the strongest warming, drying, wind velocities and solar radiation over the SPI. The consideration of flow regimes over the last 40 years shows that subcritical flow occurs most frequently (78%), however transitional flow occurs 14% of the time, implying the potential impact on Patagonian glaciers. View Full-Text
Keywords: föhn; local climate; flow regime; Southern Patagonia; WRF; Southern Patagonian Icefield föhn; local climate; flow regime; Southern Patagonia; WRF; Southern Patagonian Icefield
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    Description: Daily averages of a number of 2d and 3d variables
MDPI and ACS Style

Temme, F.; Turton, J.V.; Mölg, T.; Sauter, T. Flow Regimes and Föhn Types Characterize the Local Climate of Southern Patagonia. Atmosphere 2020, 11, 899.

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