Upper Atmosphere Research Satellite accuracy and spatial resolution, and hence to study the structure and dynamics of the region, (ii) To investigate the distribution and variability of water vapour in the middle atmosphere, to determine its role in the atmospheric general circulation, and its sources and sinks in the middle atmosphere, (iii) To measure the global distribution of oxides of nitrogen and hence to investigate their origins and their roles in catalytic cycles which control the amount of ozone in the stratospheric ozone layer. It also made extensive observations of volcanic aerosols and polar stratospheric clouds in the middle atmosphere. The instrument operated from
Ozone layer of April and May and lowest in October. While the total amount of ozone increases moving from the tropics to higher latitudes, the concentrations are greater in high northern latitudes than in high southern latitudes, due to the ozone hole phenomenon. The highest amounts of ozone are found over the Arctic during the spring months of March and April, but the Antarctic has their lowest amounts of ozone during their summer months of September and October, The ozone layer can be depleted by free radical catalysts, including nitric oxide (NO), nitrous oxide (NO), hydroxyl (OH), atomic chlorine (Cl), and atomic