The Southern Hemisphere jets and tropopause parameters derived from radio occultation monthly means
Presenter:
Pawel Hordyniec (1,2)
(1) RMIT University, SPACE Research Centre, Melbourne, Australia, (2) Wroclaw University of Environmental and Life Sciences, Institute of Geodesy and Geoinformatics, Wroclaw, Poland
(3) Bureau of Meteorology, Science and Innovation Group, Melbourne, Australia, (4) Wegener Center for Climate and Global Change (WEGC) and Institute for Geophysics, Astrophysics, and Meteorology/Institute of Physics, University of Graz, Graz, Austria, (5) Australian Antarctic Division, Kingston, Tasmania, Australia, (6) Antarctic Climate and Ecosystem Co-operative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
Poster
The long-term stability, global coverage and high vertical resolution of radio occultation measurements allows to derive three-dimensional and time-varying characteristics of the neutral atmosphere. The geophysical quantities of dry pressure and dry temperature, although lacking the moisture contribution, are well suitable for monitoring of the upper troposphere and lower stratosphere (UTLS) region. The upper-air circulation manifested by jet streams near the tropopause level opens a possibility for RO measurements to study patterns of both properties. Focusing our investigations on the Southern Hemisphere jets between mid-latitude and polar cells, we use daily RO profiles collected in 2009 to create monthly means of geopotential heights at dry pressure levels. The first-order approximation of horizontal wind is derived as a gradient of geopotential. The reference geostrophic winds are computed from ERA re-analysis fields and true winds serve as a measure of ageostrophy error for both datasets. The flow patterns for the most significant winds are analysed together with the distribution of tropopause height, pressure and temperature determined from model-independent dry RO profiles. While the magnitude of RO-derived geostrophic winds tends to be slightly underestimated and their distribution more smooth relative to background fields, the general wind patterns are well captured and agree to within 4 m/s RMSE for the polar jets identified at 200 hPa level. The distribution of tropopause temperature for meridional cross sections passing through jet streams suggests strong horizontal gradients near jet latitudes which could be utilized for determining jet core position.
Poster in PDF:
