Spectroscopic measurements of a CO2 absorption line in an open vertical path using an airborne lidar

TL;DR

This study demonstrates the use of airborne lidar to accurately measure atmospheric CO2 absorption line properties, including pressure broadening and line shift, with high agreement to theoretical models.

Contribution

It presents novel spectroscopic measurements of CO2 absorption lines from an airborne platform, validating HITRAN-based calculations with high precision.

Findings

Peak optical depth matches calculations within 0.3%

Line center shift measured within 5.2 MHz of predictions

Linewidth measured within 0.6% of theoretical values

Abstract

We use an airborne pulsed integrated path differential absorption lidar to make spectroscopic measurements of the pressure-induced line broadening and line center shift of atmospheric CO2 at the 1572.335 nm absorption line. We measure the absorption lineshape in the vertical column between the aircraft and ground. A comparison of our measured absorption lineshape to calculations based on HITRAN shows excellent agreement with the peak optical depth accurate to within 0.3%. Additionally, we measure changes in the line center position to within 5.2 MHz of calculations, and the absorption linewidth to within 0.6% of calculations.