Global observations of the carbon budget 2. CO2 column from differential absorption of reflected sunlight in the 1.61 μm band of CO 2

Abstract

This paper investigates the impact of uncertainty in atmospheric composition and state upon the feasibility of measuring the CO2 column from spectral analysis of sunlight reflected to space in the 1.61 μm absorption band of CO2. In principle, measurements of clear sky radiance at two frequencies, one where CO2 absorbs strongly and the other weakly, allow the difference between the optical thicknesses of the atmosphere at the two frequencies to be determined precisely. That difference, denoted by L, is a linear functional of the CO2 density profile, which depends strongly on the CO2 amount and only weakly upon its vertical distribution, thus suggesting that the CO2 column may be estimated fro..