Tropospheric constituents from direct sun and sky radiance measurements: preliminary results on measurement feasibility

摘要

The background and an approach for deriving tropospheric ozone, water vapor and aerosols from direct sun observations, zenith sky radiances and the ratio of radiances at large zenith (near horizon) to the corresponding zenith sky radiances is described. Surface based remote sensing measurements of zenith sky and large zenith angle atmospheric radiance measurements have been made in the wavelength range of 305 nm to 923 nm near local noon from a mountain site at an altitude of 2.6 km in the vicinity of Boulder, Colorado. The wavelength dependence of the limb/zenith radiance ratios indicate significant limb darkening in the ultraviolet that changes to limb brightening with increasing wavelengths that is a maximum in the blue. Model calculations of a molecular atmosphere with absorption by ozone for wavelengths between 300 and 400 nm indicates that this ratio is sensitive to tropospheric ozone. Results from measurements and model calculations of the sensitivity of these ratios to tropospheric ozone are presented.