Stephan Winkler’s 2017 Imaggeo Photo Contest finalist photo showcases an unusual weather phenomenon…
The image shows a typical weather situation in the Southern Alps of New Zealand with a moist, westerly airflow pushing over the Main Divide [which separates the water catchments of the more heavily populated eastern side of the island from those on the west coast] to create a typical foehn wind [dry and warm winds which form on the downside of a mountain range] pattern (locally called Nor’Wester) in the region. Immediately west of this Main Divide, annual precipitation of up to 15,000 mm has been estimated.
The upper part of Tasman Glacier, as other glaciers around and immediately east of the Main Divide, receive impressive amounts of snow due to an overspill effect and can still be regarded as maritime.
In the image, however, the situation is displayed when right at the Main Divide the clouds disappear due to increasing temperatures when flowing over the Divide. The foehn wind developing with such weather pattern can be very strong. However, the image nicely shows how the glaciation of the central Southern Alps is influence by the availability of moisture and the dynamic character of the regional climate.
Description by Stephan Winkler (Senior Lecturer in Quaternary Geology and Palaeoclimatology at the University of Canterbury), as published previously on imaggeo.egu.eu
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