Annual and El Niño-Southern Oscillation variations in observations of in situ stratospheric ozone over Peninsular Malaysia

Abstract

[1] We present stratospheric ozone profiles over Peninsular Malaysia in equatorial Southeast Asia measured twice a month for the 8 years from 1992 to 1999. For correlation analyses we used data after July 1993, to exclude the period just after the eruption of Mount Pinatubo. In the bottom of the stratosphere (the layer from the tropopause (16.5 ± 0.7 km) up to 20 km), ozone concentrations oscillated annually, showing minimum values around February–April in the northern winter and maximum values around July–September in the northern summer. The amplitude of the annual oscillation of ozone in the bottom of the stratosphere seemed to be several dozen percent larger than the amplitudes of the oscillations over Natal in Brazil and Samoa in the Pacific Ocean. Ozone concentrations of individual soundings closely correlated with temperature (R = 0.833 at 17.5 km; R = 0.854 at 19.5 km) and varied inversely with tropopause heights (R = −0.615 at 17.5 km; R = −0.390 at 19.5 km), indicating the influence of seasonal variations in convection and Brewer-Dobson circulation induced by extratropical wave driving. The ozone anomaly from monthly mean values in the bottom of the stratosphere was positively correlated (R = 0.570 at 17.5 km) with the Southern Oscillation Index (SOI) through changes in tropopause heights; this was unexpectedly different from the negative correlation between ozone and SOI in the western Pacific. This east-west difference might be attributable to the different circulation systems in the western Pacific and Peninsular Malaysia.