Changes in the stratospheric and mesospheric thermal conditions during the last three decades:4.trends in the height and temperature of the stratopause

摘要

Statistical analysis was applied to series of weekly temperatures measured by meteorological rockets at heights of 25-7km over the Heiss Island (80.6deg N),Volgograd (148.7deg N) Thumba (8.5deg N),and Molodezhnaya (67.7deg S) stations during 1969-1995.A linear approximation of a time series for month,with the long-period component filtered out,was used to construct vertical profiles of temperature and to estimate variations in the stratopause height and temperture during the entire period of rocket measurements.A statistically significant decrease (with 95% confidence) was established in the stratopause height.Specifically,the stratopause height was found to decrease by 0.4 km over Heiss Island,by 0.5 km over Thumba,and especially strongly (by 2.4 km)over Volgograd.Over the Molodezhnaya station,the annual mean stratopause height did not vary.A decrease in the stratopause height from the data measured at Volgograd and Thumba was ound to occur inall seasons,except for the spring months.The maximum decrease in the stratopause height at 5-7 km was observed over Volgograd in winter.The stratopause height over Heiss Island decreased only in January (2.4 km),February (4.5 km),and insignificantly in March (1.0 km).The stratopause temperature decreasd statistically significantly over Heiss Island (by 4.9K),Volgograd (by 2.8K),and Thumba (by 4.0 K)and increased by 1.0 K(statistically insignificnatly with 95% confidence)over the Molodezhnaya station.The changes in the stratopause temperature agree with previously published values of annual mean trends in the height range 45-50km.Estimatesof monthly mean variations in the stratopause temperature are presented.The assumption is discussed that ozone depletion in the mesosphere during the last decades is the main cause for the observed decrease in the stratopause height.