A23B-0287
Atmospheric CO2 Variability Observed during ASCENDS Flight Campaigns

Tuesday, 15 December 2015
Poster Hall (Moscone South)
Bing Lin1, Edward V Browell2, Joel F Campbell1, Yonghoon Choi3, Jeremy T Dobler4, Tai-Fang Fan5, Fenton W Harrison1, Susan A Kooi3, Zhaoyan Liu1, Byron Meadows1, Amin R Nehrir1, Michael D Obland1, James Plant1 and Melissa M Yang1, (1)NASA Langley Research Center, Hampton, VA, United States, (2)STARSS II Affiliate, Hampton, VA, United States, (3)Science Systems and Applications, Inc. Hampton, Hampton, VA, United States, (4)Exelis, Inc (now part of Harris Corp.), Geospatial Systems, Fort Wayne, IN, United States, (5)SSAI, Hampton, VA, United States
Abstract:
Accurate observations of atmospheric CO2 with a space-based lidar system, such as for the NASA ASCENDS mission, will improve knowledge of global CO2 distribution and variability and increase the confidence in predictions of future climate changes. To prepare for the ASCENDS mission, the NASA Langley Research Center and Exelis Inc. (now part of Harris Corp.) have been collaborating in the development and evaluation of an Intensity-Modulated Continuous-Wave (IM-CW) lidar approach for measuring atmospheric CO2 from space. Two airborne IM-CW lidars operating in the 1.57-mm CO2 absorption band have been developed and flight tested to demonstrate precise atmospheric CO2 column measurements. A total of 14 flight campaigns have been conducted with the two lidar and in-situ CO2 measurement systems.

Significant atmospheric CO2 variations on various spatiotemporal scales were observed during these campaigns. For example, around 10-ppm CO2 changes were found within free troposphere in a region of about 200×300 km2 over Iowa during a summer 2014 flight. Even over extended forests, about 2-ppm CO2 column variability was measured within about 500-km distance. For winter times, especially over snow covered ground, relatively less horizontal CO2 variability was observed, likely owing to minimal interactions between the atmosphere and land surface. Inter-annual variations of CO2 drawdown over cornfields in the Mid-West were found to be larger than 5 ppm due to slight differences in the corn growing phase and meteorological conditions even in the same time period of a year. Furthermore, considerable differences in atmospheric CO2 profiles were found during winter and summer campaigns. In the winter CO2 was found to decrease from about 400 ppm in the atmospheric boundary layer (ABL) to about 392 ppm above 10 km, while in the summer CO2 increased from 386 ppm in the ABL to about 396 ppm in free troposphere. These and other CO2 observations are discussed in this presentation.

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