Retrieval of Martian ozone and dust from SPICAM spectrometer for MY27-MY28

Abstract

Ozone (O₃) is important in the stabilisation of CO_{{2}} in the Martian atmosphere and thus it is important to study the spatio-temporal variability of O_{{3}}. We retrieve two years of total columnar O_{{3}} from raw spectral data provided by the SPectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) instrument aboard the Mars Express. The seasonal variability is studied in tropical, mid- and high latitudes and is compared with simulations by a photochemical coupled general circulation model (GCM). The high latitudes exhibit the largest seasonal variations in O_{{3}}, with a winter high and a summer low and a comparison with GCM results is good in general. We have studied the correlation of O_{{3}} with dust, retrieved simultaneously from SPICAM observations. In southern tropical latitudes, the columnar O_{{3}} is seen to increase during a global dust storm year (Martian year (MY) 28) compared to the O_{{3}} column values during a year without global dust storm (MY27), although the water vapour column between these years remains unchanged. This indicates the radiative impact of dust on O_{{3}} and its retrieval. We also study the ozone-carbon monoxide correlation as a tracer of dynamics. The dynamical contribution to the O_{{3}} column is found to be the highest during winter over the southern polar region.