Global atmospheric chemistry from satellites: results from UARS/ISAMS

Abstract

Satellites are a relatively new tool for investigating atmospheric chemical processes and their products. The precision and, in particular, the space and time coverage, now being achieved is immensely useful, and often essential, where global-scale phenomena like the variability of the stratospheric ozone layer are under study. The IR remote-sensing method using pressure modulator radiometry has recently been extended to the mapping of trace species. The technique is described, and its capabilities demonstrated with some selected new results from the improved stratospheric and mesopheric sounder (ISAMS) on the upper atmosphere research satellite (UARS). ISAMS was designed to study nitrogen-catalysed ozone chemistry, plus transport and other processes involving water vapour, methane and carbon monoxide, in the middle atmosphere. Its primary products are fields of temperature and composition, including all of the important members of the active nitrogen family, water, methane, carbon monoxide, ozone, aerosols and ice clouds. In the new data, all of these show large variations with time, height and latitude. The results have not yet been fully analysed, but early indications are that they confirm some models based on theoretical predictions and earlier, more limited, data, while in other cases they show that the situation is more complex than had been assumed. Sophisticated studies of the radiative–chemical–dynamical system in the stratosphere using satellite data and computer models are now in progress. In the future, even more advanced sensors now being built will obtain improved spatial resolution in the stratosphere, and map the global budgets of tropospheric trace gases as well.