Abstract
Abstract. Two years of Very High Frequency (VHF) radar echo power observations are used to examine the structure and variability of the tropopause at Davis, Antarctica. Co-located radiosonde and ozonesonde launches provide data with which to calculate the lapse-rate and chemical tropopauses. The radar tropopause, defined as the maximum vertical gradient of echo return power, can be used as a definition of the Antarctic tropopause throughout the year under all meteorological conditions. During the extended summer period of December–April (DJFMA) inclusive, radar tropopauses are (0.2 ± 0.4) km lower than radiosonde lapse-rate (i.e. the World Meteorological Organisation – WMO) tropopauses and during the extended winter period of June–October (JJASO) inclusive, the radar tropopauses are (0.8 ± 1.0) km lower. A potential vorticity tropopause is defined as the altitude of the −2 PVU surface (where 1 PVU = 106 m2 s−1 K kg−1). This is (0.3 ± 0.5) km lower than the radar tropopause during DJFMA and (0.5 ± 1.0) km lower during JJASO. The radar, potential vorticity and ozone tropopauses decrease in altitude during increasingly strong cyclonic conditions, in contrast to the radiosonde WMO tropopause which remains nearly constant. During strong JJASO cyclonic conditions, there are large (several km) differences between WMO tropopause altitudes and radar tropopause altitudes. A seasonal cycle in tropopause fold occurrence is observed, with approximately a three-fold increase during JJASO.
Highlights
The upper troposphere and lower stratosphere (UTLS) is the atmospheric region within a few kilometers of the at which the temperature lapse rate falls below 2 K km−1 and the average lapse rate within 2 km above this altitude does not exceed S2 Koklimd−1E(aWrotrhld Meteorological Organization, 1957).Published by Copernicus Publications on behalf of the European Geosciences Union
For reasons related to the seasonal variability in the tropopause structure, the extended winter season is defined as the months June–October inclusive, and the extended summer season as December–April inclusive (DJFMA)
Sudden increases in zradar (e.g. 17 September 2009) are reminiscent of the tropopause folds associated with stratospheric intrusions of radar data, ozonesonde data over the nine years from Febru- ozone into the troposphere identified in the Northern Hemiary 2003 until March 2012 are used to provide sufficient sphere (Hocking et al, 2007)
Summary
The upper troposphere and lower stratosphere (UTLS) is the atmospheric region within a few kilometers of the (above 500 hPa) at which the temperature lapse rate falls below 2 K km−1 and the average lapse rate within 2 km above this altitude does not exceed S2 Koklimd−1E(aWrotrhld Meteorological Organization, 1957). The troposphere and stratosphere are chemically distinct regions of the atmosphere, allowing for the definition of a chemical tropopause. This tropopause is based on a threshold concentration of a trace species in a vertical profile, such as ozone (Bethan et al, 1996; Pan et al, 2004)
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