Temperature climatology and trend estimates in the UTLS region as observed over a southern subtropical site, Durban, South Africa H. Bencherif1, R. D. Diab2, T. Portafaix1, B. Morel1, P. Keckhut3, and A. Moorgawa2 1Laboratoire de l'Atmosphère et des Cyclones, UMR 8105 CNRS/Université/Météo-France, Université de La Réunion, B.P 7151, 97715, Saint-Denis, Reunion Island, France 2University of KwaZulu-Natal, Durban 4041, South Africa 3Service d'Aéronomie, UMR-CNRS 7620, B.P. 3, Verrières-le-Buisson, France
Abstract. Temperature trends in the UTLS region are under-reported, particularly in
the Southern Hemisphere, and yet temperature is one of the most important
indicators of changes in dynamical and radiative processes in the
atmosphere. Here radiosonde data from Durban, South Africa (30.0° S,
30.9° E) over the period 1980 to 2001 (22 years) between 250 and 20 hPa
are used to derive a mean temperature climatology and to determine trends.
The seasonal cycle at the 250-hPa level is anti-correlated with the seasonal
cycles at the 150-hPa and 100-hPa heights. The 100-hPa level (local
tropopause) exhibits a minimum temperature in late summer and a maximum in
winter, and closely corresponds to previous results for tropical regions.
Based on a Fourier analysis, both the annual cycle (AO) and the semi-annual
cycle (SAO) are dominant, although the former is about 4 times stronger. The
AO is strongest at the 100-hPa height. A trend analysis reveals a cooling
trend at almost all heights in the UTLS region, with a maximum cooling rate
of 1.09±0.41 K per decade, at 70-hPa. Cooling rates are in good
agreement with other studies and are slightly higher in summer than in
Citation: Bencherif, H., Diab, R. D., Portafaix, T., Morel, B., Keckhut, P., and Moorgawa, A.: Temperature climatology and trend estimates in the UTLS region as observed over a southern subtropical site, Durban, South Africa, Atmos. Chem. Phys., 6, 5121-5128, doi:10.5194/acp-6-5121-2006, 2006.