[A-AS10] Stratosphere-troposphere Processes And their Role in Climate

[AAS10-P06] Zonally asymmetric tropopause height trend in the subtropical Indian-Pacific sector

*Yuki Ishida¹, Jinro Ukita², Meiji Honda³ (1.Graduate School of Science and Technology, Niigata University, 2.Faculty of Science, Niigata University, 3.Program of Field Research in the Environmental Sciences, Faculty of Science, Niigata University)

Keywords:Tropopause, ENSO, Long-term trend

Tropopause variability provides key information on dynamical coupling and exchanges of the mass and chemical species between the stratosphere and troposphere. Its increasing trend has been linked to global warming of the troposphere (Santer et al. 2003; Seidel and Randel 2006). There are however notable regional differences in the trend. A zonally asymmetric pattern of the trend in boreal winter has been identified in the subtropical Indian-Pacific sector (Wilcox et al. 2012), one with an increasing trend over the southeast Asia and the other with a decreasing trend in the central Pacific. Based on an analysis on the JRA-55 reanalysis data over the period of 1979-2017 we found that a highly resembling pattern emerges as the leading EOF mode of the interannual variation in the detrended tropopause height field (r = 0.79 between the PC1 and NINO3.4). Focusing on the signature over the southeast Asia, we examined possible mechanisms, including a longitudinally restricted local Hadley circulation. At the meeting we shall discuss the results from this analysis and a potential upper tropospheric transient eddy effect.