TOTAL OZONE AND AEROSOL OPTICAL DEPTHS INFERRED FROM RADIOMETRIC MEASUREMENTS IN THE CHAPPUIS ABSORPTION-BAND

A second-derivative smoothing technique, commonly used in inversion wo rk, is applied to the problem of inferring total columnar ozone amount s and aerosol optical depths. The application is unique in that the un knowns (i.e., total columnar ozone and aerosol optical depth) may be s olved for directly without employing standard inversion methods. It is shown, however, that by employing inversion constraints, better solut ions are normally obtained. The current method requires radiometric me asurements of total optical depth through the Chappuis ozone band. It assumes no a priori shape for the aerosol optical depth versus wavelen gth profile and makes no assumptions about the ozone amount. Thus, the method is quite versatile and able to deal with varying total ozone a nd various aerosol size distributions. The technique is applied first in simulation, then to 119 days of measurements taken in Tucson, Arizo na, that are compared to TOMS values for the same dates. The technique is also applied to two measurements taken at Mauna Loa, Hawaii, for w hich Dobson ozone values are available in addition to the TOMS values, and the results agree to within 15%. It is also shown through simulat ions that additional information can be obtained from measurements out side the Chappuis band. This approach reduces the bias and spread of t he estimated total ozone and is unique in that it uses measurements fr om both the Chappuis and Huggins absorption bands.