An observed annual cycle in tropical upper stratospheric and mesospheric ozone

Analysis of more than one year of backscattered ultraviolet radiances obtained from an equatorial orbit by the Atmosphere Explorer-E satellite reveals an annual cycle in tropical, high altitude ozone which shows no latitude dependence between 20 degrees south and 20 degrees north. The amplitude of the variation increases with altitude. In the 35 to 45 km altitude region statistics of the data suggest no variation whatsoever, while in the lower mesosphere the radiances indicate an ozone increase of 25 to 30 percent between January and July with a decrease thereafter provided the solar irradiance remained constant except for the variation with earth-sun distance.