Intensive tethersonde profiling campaigns
at Halley, Antarctica, during winter 2003.
For more infomation, please contact Phil Anderson.
Last updated 8th December, 2003. This page is still severely under construction...
The tethersonde profiling campaigns are designed to take measurments of
the boundary layer above mast height during stable and very stable conditions.
A 30 m turbulence/profile mast provides continual data up to 32 m. The tethersondes
are flown under Hagaman kites, with 3 houry profiles when conditions allow.
Acoustic backscatter from the flights gives a qualitative impression of the
level of turbulence and temperature gradient aloft. Variability (layering)
observed in the backscatter profile is of interest, and hence tetherprofiles
through layers are studied in detail (note 1).
2003 was the first year of campaigns, and various technical difficulties
are still being solved: hence the data coverage is not perfect.
The following pages show quick views of the available data.
IOC 1 from 18th to 22nd May, 2003. Long duration (4 day) dislocation event (note 2).
IOC 2 from 31st July to 2nd August, 2003. 2.5
day dislocation with near re-combination after 24 hours
IOC 3 from 13th to 16th November,2003. Near classic
diurnal variation in inversion strength, from neutral to stable stratification.
Pictures of wintertime flying: visible and
infra-red.
Notes
1. Layering in the upper boundary layer is frequently observed in the
acoustic backscatter data from Halley. The mechanism which initiates and
sustains sharply defined layering in the presence of turbulence is not understood.
Typical examples of sodar data with layering can be seen
here, with the rest of the sodar data available
here.
2. "Dislocation" is a term given to episodes where the temperature at
the surface decreases over time, whilst aloft it increases. This implies
a strong divergence in heat flux aloft, leading to warming, despite a surface
radiative imbalance. These events are thought to be self sustaining, in
that a critical temperature gradient is reached (for a given geostrophic
wind) beyond which turbulence heat flux (sensible heat flux) is suppressed.
Heat is still supplied to the upper levels of the surface layer, but is
suppressed within the surface layer, leading to rapid snow surface cooling,
but warming at upper levels.