Upper stratospheric temperature climatology derived from SAGE II observations: preliminary results

This study shows that the temperature information in the upper stratosphere can be derived from the SAGE II 385-nm observations. The preliminary results indicate that the zonal mean temperature increases with altitude below 50 km and decreases above 50 km. At 50 km, a regional maximum of 263 K is located in the tropics, and a minimum of 261 K occurs in the subtropics in both hemispheres. The derived long-term temperature changes from 1985 to 1997 reveal a statistically significant negative trend of -2 to -2.5 K/decade in the tropical upper stratosphere and about -2 K/decade in the subtropics near the stratopause. At latitudes poleward of 50 degrees, the results show a statistically significant positive trend of about 1 K/decade in the upper stratosphere. The preliminary results also show large annual temperature oscillations in the extratropics with a maximum amplitude of approximately 8 K located at about 44 km near 50 degrees in both hemispheres during local summer. In addition, the semiannual oscillation is found to be a maximum in the tropics with a peak amplitude of approximately 3.3 K located at about 42 km during the equinox.