Atmospheric CO_(2) measurements with a 2 (mu)m airborne laser absorption spectrometer employing coherent detection

摘要

We report airborne measurements of CO_(2) column abundance conducted during two 2009 campaigns using a 2.05 (mu)m laser absorption spectrometer. The two flight campaigns took place in the California Mojave desert and in Oklahoma. The integrated path differential absorption (IPDA) method is used for the CO_(2) column mixing ratio retrievals. This instrument and the data analysis methodology provide insight into the capabilities of the IPDA method for both airborne measurements and future global-scale CO_(2) measurements from low Earth orbit pertinent to the NASA Active Sensing of CO_(2) Emissions over Nights, Days, and Seasons mission. The use of a favorable absorption line in the CO_(2) 2 (mu)m band allows the on-line frequency to be displaced two (surface pressure) half-widths from line center, providing high sensitivity to the lower tropospheric CO_(2). The measurement repeatability and measurement precision are in good agreement with predicted estimates. We also report comparisons with airborne in situ measurements conducted during the Oklahoma campaign.