Stratospheric temperature trends in the Southern Hemisphere

GUSTAVO A. MANSILLA; EDUARDO GUENNAM; MARTA M. ZOSSI

Workshop; 11th International Workshop on Long-TermChanges and Trends in the Atmosphere; 2022

Two main factors are attributed to the stratospheric cooling observed during the last decades. On one side the increasing concentrations of greenhouse gases and, on the other side the emissions of halogenated substances that produce ozone depletion. In this work, an analysis of the temperature behaviour was made for the lower stratosphere (100 hPa - 30 hPa) and middle (30 hPa - 10 hPa) between 1979 and 2020, in the Southern Hemisphere (SH) and in the South Atlantic Magnetic Anomaly (SAA) area. The results were compared with the stratospheric temperature behaviour on the global scale obtained by models and observations. The analyses conducted in this work are based on data of monthly averages anomalies of the stratospheric temperature obtained from NOAA Web-based Reanalysis Tool. In addition, an analysis of the temperature profiles trends was made considering the following heights: 100 hPa (15.9 km), 50hPa (21.0 km), 30 hPa (24.8 km), 20 hPa (27.8 km) and 10 hPa (33 km). Linear regression was made in each of the periods considered and trends and uncertainties were obtained. First, the entire period was considered; then, in order to isolate the significant effects of the volcanic events that occurred in 1982 (Chichon) and 1991 (Pinatubo), the whole period was subdivided as follows: 1979-1981, 1984-1990, 1994-2006 and 2006-2020. The whole period results confirmed a cooling of the SH stratosphere and an increase in stratospheric cooling with height, with values between -0.20 K/decade and -0.50 K/decade for lower stratosphere and between -0.30 K/decade and -1.10 K/decade for middle stratosphere. The datasets have different tendency values for each altitude, for instance at 30 hPa (24.8 km), trends have values between (-0.51 0.06) K/decade, for NCEP/NCAR R1dataset and (-0.210.05 K/decade) for Era-Interim dataset. At 100 hPa (15.9 km), the 20CRv3 dataset and Era-Interim dataset have positive tendencies in both zones analyzed: between (0.03 0.05) K/decade and (0.050.05 K/decade) for the SH and between (0.100.04) K/decade and (0.120.04) K/decade for the SAA area. For the period 2006-2020, at 15.9 km, the different datasets analyzed in this work, have positive trends for SH. This warmings values vary between (0.290.13) K/decade, for Era-Interim and (0.850.13) K/decade, for NCEP/NCAR R2.