Evaluation of Column CO2Retrieval from Intensity-Modulated Continuous-Wave Differential Absorption Lidar Measurements during ACT-America
Abstract
We present an airborne field evaluation of an Intensity-modulated continuous-wave (IM-CW) lidar system that measures atmospheric CO2column concentrations. This system transmits simultaneous wavelengths tuned to online and offline wavelengths on the 1.57111 μm CO2absorption line, with each modulated wavelength using orthogonal swept frequency waveforms. After this system was calibrated, we then used a spectroscopic model to derive the average column CO2mixing ratio (XCO2) using the measured optical depths. Based on insitu meteorological measurements and using Picarro as a calibration source we demonstrate our calibration is consistent from season to season and show a maximum calibration error of 4.1 ppm with a standard deviation of 1.2 ppm when compared to our calibration curve when compared over many seasons. We found that by using 10 second or longer moving averages, 1 ppm or better precision as demonstrated over a period of over 90 minutes, thus demonstrating the suitability of this instrument for measuring synoptic-scale variations in atmospheric XCO2. The estimated precision values for 0.1-s, 1-s, 10-s, and 60-s data were 3.47 ppm (0.86%), 0.987 (0.24%), 0.353 (0.087%), and 0.248 (0.061%), respectively. Their corresponding SNRs, which are the mean XCO2 divided by the standard deviation, are 116.4, 416.8, 1152, and 1748, respectively. We compared the observed trends with in situ CO2data assimilated into the Goddard Earth Observing System (GEOS). This analysis also showed that the measurement stability satisfied the ACT-America science requirement.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A53I..18C
- Keywords:
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- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0480 Remote sensing;
- BIOGEOSCIENCES