Atmospheric CO2 monitoring from space

A spectroscopic method of monitoring the atmospheric CO2 mixing ratio vertical profile from space is described. An experimental design is presented for a solar occultation mode with the O-2 A band in the visible region to retrieve pressure and temperature profiles first, and then several CO2 bands in the infrared region at 4.3, 2.7, and 2.0 mu m to obtain CO2 mixing ratio profiles. Instrument techniques considered are low resolution Fourier transform spectrometry and radiometry of various bandwidths. Simulations indicate that the precision of the pressure, temperature, and CO2 mixing ratio measurements for an altitude region 30-10 km are less than 1%, 1 K, and 1%, respectively, for the case of the Fourier transform spectrometer and approximately 1%, 1 K, and 2% for the case of the radiometer. With careful experimental design, measurements can be made with better precision and also can extend below 10 km. This inferred precision of CO2 may be considered to be good enough for investigating atmospheric dynamics when CO2 is used as a tracer and also for measuring spatial and temporal variations of CO2 mixing ratios in the range of 0.5-6.5% of 350 parts per million by volume in the troposphere and the lower stratosphere. (C) 1997 Optical Society of America.