Using Satellite Thermal Infra-Red Imagery to Study Boundary Layer Structure in an Antarctic Katabatic Wind Zone

M.J. Varley, T.A. Lachlan-Cope and J.C. King

We have used snow surface temperatures obtained from thermal infra-red satellite imagery gathered under cloud-free conditions, together with radiosonde profiles of free-air temperature and high-resolution topographic data to study the thermal structure of the atmospheric boundary layer inland of Halley Research Station Surface temperatures over the Brunt Ice Shelf are significantly lower than those observed on the lower part of the adjoining coastal slopes as a result of the strong surface temperature inversion that forms over the ice shelf. Between 400 and 1500 m elevation the surface temperature lapse rate is close to the dry adiabatic value while the free-air temperature profile shows significant stability over this height range. This appears to imply that the strength of the surface inversion increases with increasing elevation. Above 1500 m the surface temperature lapse rate becomes significantly superadiabatic and the coldest surface temperatures are found a few tens of kilometres inland of the highest topography. We believe that this technique may prove useful for studying boundary layer structure in other regions of Antarctica where both high resolution topographic data and suitable satellite imagery are available.

This (105 Kb) is a NOAA AVHRR channel 4 image of the Brunt Ice Shelf and Coats Land at 0723 UTC on 2 August 1995, obtained using the ARIES satellite reception facility at Rothera Research Station. Halley Research Station is marked with a cross. A larger version of the image (380K) is available here .

	A topographic section along the line marked on the image.
	The surface temperature profile along the section line.
	The surface temperature (solid line) and the free-air temperature (broken line - from a radiosonde ascent at Halley) as a function of height.

Points to note include:

The low-level inversion in both surface and free-air temperatures
The near adiabatic lapse rate of the surface temperature between 400 and 1500 m
The stability of the free-air profile over this height range
The superadiabatic lapse rate in surface temperature on the upper part of the slope

This study forms part of the Coats Land Mesoscale Project

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