Satellite observations of mesospheric ozone

A method is presented by which measurements of O2 Atmospheric band volume emission rate and temperature can be used to infer ozone mixing ratios in the mesosphere. The retrieval relies on the fact that a significant portion of the dayglow originates from ozone photolysis. This method is used to derive ozone concentrations from observations made by the High Resolution Doppler Imager (HRDI) on board the Upper Atmosphere Research Satellite. Five years of measurements are presented, with coverage up to 72° in latitude and an altitude range of 65 to 97 km. Observations show repeatable seasonal variability, with equatorial ozone showing a predominantly semi-annual variation at all altitudes. Equatorial ozone maximizes at equinox, with the amplitude of the variation being greater than 15% of the annual mean between 75 and 95 km. At mid-latitudes the variation changes to an annual cycle, with minimum ozone concentrations at 80 km seen during summer solstice. This is coincident with a maximum in water vapor measured by the Halogen Occultation Experiment (HALOE). At 95 km mid-latitude ozone peaks during summer solstice, coinciding with a minimum in observed temperatures. Simulations using a 1-dimensional photochemical model, constrained to observed temperatures and water vapor concentrations, successfully reproduce the relative changes in ozone. The minimum in ozone at 80 km is due to increased destruction of odd-oxygen by odd-hydrogen resulting from photolysis of water vapor. The maximum at 95 km is a result of the temperature dependence on odd-oxygen partitioning, as well as increased photolytic production of atomic oxygen.;A unique feature of the HRDI mesospheric ozone dataset is that all daylight local times are sampled. In the mesopause region large diurnal variability is observed, which is the result of a combination of chemical and dynamical control. Below 80 km the daytime variation in ozone is determined by photochemical reactions that affect the concentrations of atomic oxygen and hydrogen species. Above 80 km modeling studies show that ozone is sensitive to vertical motions. In particular, an enhancement in afternoon ozone seen during equinox is successfully modeled as a result of tidal advection of atomic oxygen from the lower thermosphere.