Aircraft-based investigation of boundary layer structures over the North Water Polynya and in summertime katabatic winds over northwest Greenland.

Ernsdorf, Thomas, Heinemann, Günther and Drüe, Clemens (2012) Aircraft-based investigation of boundary layer structures over the North Water Polynya and in summertime katabatic winds over northwest Greenland. [Talk] In: International Polar Year (IPY) Conference "From Knowledge to Action". , 22.04.-27.04.2012, Montréal, Canada .

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Abstract

The experiment IKAPOS (Investigation of Katabatic winds and Polynyas during Summer) was performed in June 2010. It was targeted at the summertime katabatic wind system in coastal areas of northwest Greenland and at atmosphere/sea-ice/ocean exchange processes over the North Water (NOW) Polynya.
The katabatic-driven near-surface wind regime plays a key role in exchange processes of energy and momentum between the atmosphere and the underlying surface over the ice sheet of Greenland. During summer, cooling of the boundary layer and hence the katabatic forcing is less than during winter, but strong winds can occur under appropriate synoptic forcing. On the other hand, the NOW Polynya represents one of the largest polynyas of the Arctic, and the air-sea interaction over the NOW has a significant impact on ocean processes, ice formation, gas exchange and biology.
IKAPOS is mainly based on measurements with the research aircraft POLAR 5 of Alfred Wegener Institute (AWI, Bremerhaven). In order to determine turbulent heat and momentum fluxes, POLAR 5 was instrumented with a turbulence measurement system collecting data on a nose boom with a sampling rate of 100 Hz.
Besides navigational and further basic meteorological instrumentation, the aircraft was equipped with radiation and surface temperature sensors, laser altimeters, and video and digital cameras. A total of six research flights have been performed, two of them were katabatic wind flights (over Humboldt and Steenstrup Glacier, respectively).
The katabatic wind flights capture conditions of weak and strong synoptically forced katabatic
wind with up to 14 m s-1 wind speed. Over the NOW, a stable, but fully turbulent boundary layer with strong winds of 15 m s-1 to 20 m s-1
was present during conditions of relatively warm synoptically induced northerly winds. Strong surface inversions were found in the lowest 100 m to 200 m. As a consequence of channeling effects at Smith Sound a well-pronounced low-level jet system was documented. These channeling effects lead to an increased wind-induced sea-ice export from the Nares Strait through Smith Sound.
Three-dimensional (3D) structures of mean quantities will be presented as well as turbulent fluxes and energy budgets in the ABL over the ice sheet of Greenland and the NOW Polynya.
The findings of IKAPOS are valuable for the validation of numerical models (including climate models) and will contribute to the understanding of the exchange processes over summertime Arctic polynyas and the Greenland ice sheet.

Document Type: Conference or Workshop Item (Talk)
Keywords: Katabatic winds; Polynya; Greenland; IKAPOS
Projects: Polynya, Laptev Sea System
Date Deposited: 11 Dec 2014 15:15
Last Modified: 11 Dec 2014 15:15
URI: http://oceanrep.geomar.de/id/eprint/26463

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