Pulsed Airborne Lidar measurements of Atmospheric CO2 Column Absorption and Line Shapes from 3-13 km altitudes
James
B
Abshire, NASA -Goddard, james.b.abshire@nasa.gov
(Presenting)
Haris
Riris, NASA-Goddard, haris.riris@nasa.gov
Graham
R.
Allan, Sigma Research, graham.r.allan@nasa.gov
Clark
Weaver, GEST - University of Maryland, clarkweaver@gmail.com
Jianping
Mao, GEST - University of Maryland, jianping.mao@nasa.gov
Xiaoli
Sun, NASA -Goddard, xiaoli.sun@nasa.gov
Axel
Amediek, DLR, Germany, axel.amediek@dlr.de
We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA’s ASCENDS mission. Our technique uses two pulsed lasers allowing simultaneous measurement of a CO2 absorption line in the 1570 nm band, O2 extinction in the Oxygen A-band and surface height and backscatter. The lidar measures the energy and time of flight of the laser echoes reflected from the atmosphere and surface. The lasers are rapidly and precisely stepped in wavelength across the CO2 line and an O2 line region during the measurement. The receiver uses a telescope and photon counting detectors, and measures the background light and energies of the laser echoes from the surface and atmosphere. The gas extinction and column densities for the CO2 and O2 gases are estimated from the ratio of the on- and off- line signals via the DIAL technique. Time gating is used to isolate the laser echo signals from the surface.
We have demonstrated the CO2 measurement from the NASA Glenn Lear-25 aircraft. The airborne lidar steps the pulsed laser’s wavelength across the selected CO2 line with 20 steps per scan. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a photomultiplier and is recorded. In July and August 2009 we made 9 two 2 hour long flights and measured the atmospheric CO2 absorption and line shapes using the 1572.33 nm line. Measurements were made at stepped altitudes from 3-13 km over Nebraska, Illinois, the DOE SGP ARM site, and near and over the Chesapeake Bay in North Carolina and Virginia. Strong laser signals and clear CO2 line shapes were observed at all altitudes, and some measurements were made through thin clouds. Analysis shows that the average signal levels follow predicted values, the altimetry measurements had an uncertainty of about 4 m, and that the average optical line depths follow the number density calculated from in-situ sensor readings. The flights were coordinated with other CO2 lidar from LaRC and JPL. Details of the flights and measurements, analysis and scaling to space will be described in the presentation.
Presentation Type: Poster
Poster Session: Orbital and Suborbital Missions
NASA TE Funded Awards Represented:
Collatz, George
Impacts of Disturbance History and Climate on Carbon Fluxes from North American Forests: Application of Satellite, Inventory, and Climate Data to Inform Biogeochemical Modeling