Measurement of Pressure-Induced Broadening and Shift Coefficients of Carbon Dioxide Absorption Lines around 1.6 µm for using Differential Absorption Lidar

Abstract

A precise measurement of the vertical profiles of carbon dioxide is required for reducing the uncertainty in the carbon budget. In order to achieve measurements of the vertical CO2 distribution with an uncertainty better than approximately 4 ppm, a precise knowledge of the pressure-dependent broadening and shift coefficients of CO2 absorption lines is indispensable. In this paper, we report the measurement of air pressure-induced shift coefficients for eight absorption lines at around 1.57 µm. On average, the pressure shift coefficients are -0.30 MHz/Torr for pure CO2 and -0.24 MHz/Torr under an air-mixed condition.

Frequency stabilization of distributed-feedback laser diodes at 1572 nm for lidar measurements of atmospheric carbon dioxide

“…This offset is attributed to the constant component of the RAM and imperfect electronic components. It should also be noted that the 1572:335 nm atmospheric CO 2 line is pressure shifted from the CO 2 cell reference line by −0:25 MHz=Torr [38]. The overall offset can be calibrated with an external reference and corrected by shifting the offset locking reference frequencies.…”

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

“…IPDA measurements from aircraft have also been demonstrated 12-15 as part of efforts to develop spaceborne lidars. Converting absorption measurements to CO 2 concentrations requires precise spectroscopic knowledge, which is typically derived from controlled laboratory experiments [16][17][18][19] . Our present work extends spectroscopic investigations to conditions closer to those of atmospheric remote sensing.The lidar instrument, primarily designed for measuring the tropospheric CO 2 concentration in the column beneath the aircraft 15,20 , was flown aboard the NASA DC-8 during the ASCENDS 21 (Active Sensing of CO 2 Emissions over Nights, Days and Seasons) campaign in 2011, at altitudes ranging from 2 to 13 km above sea level.…”

“…IPDA measurements from aircraft have also been demonstrated [12][13][14][15] as part of efforts to develop spaceborne lidars. Converting absorption measurements to CO 2 concentrations requires precise spectroscopic knowledge, which is typically derived from controlled laboratory experiments [16][17][18][19] . Our present work extends spectroscopic investigations to conditions closer to those of atmospheric remote sensing.…”

Multi-points scanning method for wavelength locking in CO2 differential absorption lidar

“…Unlike the pressurebroadening effect, the atmospheric pressure shift results from energy-level shifts caused by molecular collisions, which was always thought to be negligible in the DIAL system. Based on the pressure-induced shift coefficients reported in [23] and the atmospheric pressure profile presented in [24], a 5000 m elevation leads to −354.6 Torr pressure changes, which in turn result in 88. 65 Mhz frequency shifts.…”