Systematic errors of total ozone retrievals using the 9.7‐micron channel Earth radiance

Abstract

A systematic analysis of the TIROS Operational Vertical Sounder (TOVS) used as a lower stratospheric ozone monitor is realized. The total ozone retrieved from the TOVS radiances appears to be sensitive to the vertical distribution of ozone. This dependency is first studied using radiative transfer calculations. Poor information on ozone above 40 hPa is available and thus a partial ozone column over the atmospheric layer 400–40 hPa is derived. Systematic errors of the total and partial ozone column retrievals are investigated using comparisons with Total Ozone Mapping Spectrometer observations and four‐dimensional ozone fields derived from data assimilation experiments. The latitudinal and seasonal differences over the year 1998 are inside the interval (+35, −35) Dobson Units (DU) for the total ozone column and inside (+15, −15) DU for the partial one. This work, now limited to observations over oceans, has to be extended to other conditions for a better understanding of differences between infrared ozone measurements and ultraviolet ozone measurements.