Midwinter atmospheric temperatures at ~87km above Davis station, Antarctica, are determined from hydroxyl airglow emissions. The temperature reported is determined over the interval, day-of-year (DOY) 106 to DOY 258.
TYPE OF INDICATOR
There are three types of indicators used in this report:
1.Describes the CONDITION ... of important elements of a system;
2.Show the extent of the major PRESSURES exerted on a system;
3.Determine RESPONSES to either condition or changes in the condition of a system.
This indicator is one of: CONDITION
RATIONALE FOR INDICATOR SELECTION
Over the last century the concentration of greenhouse gases has risen in the atmosphere. Greenhouse gases result in warming of the lower atmosphere but enhanced cooling of the upper atmosphere. Enhanced cooling rates of the upper atmosphere may provide a more readily measurable indicator of 'global warming'.
Midwinter hydroxyl layer temperatures, give a proxy temperature for an altitude of ~87km (just below the coldest region of the atmosphere in winter). Associated with anthropogenic greenhouse gas increases, this tenuous region of the atmosphere is expected to cool, with the magnitude of the cooling being significantly larger than the warming at ground level. When properly measured and interpreted, this may be the atmospheric region where variations in trends associated with anthropogenic climate change can be most rapidly and conclusively determined.
Hydroxyl airglow is emitted from an ~8km wide layer, centred at ~87 km.
DESIGN AND STRATEGY FOR INDICATOR MONITORING PROGRAM
Spatial Scale: Point value at Davis station, Antarctica
Frequency: Winter averages
Measurement Technique: Hydroxyl airglow rotational temperatures are determined by the standard technique involving the ratios of the intensity of hydroxyl airglow line emissions. The difficulties encountered and methods adopted at Davis are detailed in Greet et al., 1998. Refinement to the absolute temperatures determined by this technique have been published by French et al., 2000.
The values continue to be refined, though their relative difference between years is well quantified (see error estimates). The potential exists for determining some values at earlier epochs if instrumental uncertainties can be better quantified. This work is underway.
LINKS TO OTHER INDICATORS
Noctilucent cloud observations
Polar statospheric cloud observations
Stratopause region parameters for Davis
Tropospheric and lower stratospheric temperatures
Monthly averages of daily maximum and minimum temperatures
Monthly extremes of daily maximum and minimum temperatures
Atmospheric concentrations of greenhouse gas species
The fields in this dataset are: