CO2 Laser Sounder Lidar: Toward Atmospheric CO2 Measurements with High-Precision, Low-Bias and Global Coverage
Abstract
Globally distributed measurements of atmospheric CO2 concentration with high-precision, low-bias, and full seasonal sampling are crucial to advance carbon cycle sciences. However, two thirds of the Earth's surface is typically covered by clouds, and passive remote sensing approaches from space are limited to cloud-free sunlit scenes. NASA Goddard Space Flight Center has developed a pulsed, integrated-path differential absorption (IPDA) lidar approach to measure column average CO2 mixing ratio (XCO2) from space. Measurements of time-resolved laser backscattering from the atmosphere allows precise knowledge of the photon path-length to cloud tops, as well as to ground, which allows the technique to retrieve XCO2 to cloud tops.
We demonstrate this measurement capability using airborne lidar measurements from the summer 2017 ASCENDS/ABoVE airborne campaign in Alaska. We show retrievals of XCO2 to the ground, and to the boundary layer and mid-level cloud tops. We also demonstrate how the partial column XCO2 measured to cloud tops and the cloud slicing approach help resolve the vertical and horizontal gradients of CO2 in cloudy conditions. The XCO2 retrievals from the lidar are validated against airborne in situ measurements during spiral-down maneuvers and compared to the Goddard Parameterized Chemistry Transport Model (PCTM) simulations. Adding this measurement capability to future CO2 lidar missions will provide full global and seasonal data coverage as well as some information about vertical structure of CO2. This unique data is expected to benefit atmospheric transport process studies, assimilation of carbon data in models, and estimating global and regional carbon fluxes.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A43D..01M
- Keywords:
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- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES;
- 3360 Remote sensing;
- ATMOSPHERIC PROCESSES