Publication Date:
2017-06-08
Description:
Within the California South Coast Air Basin (SoCAB), X varies significantly due to atmospheric dynamics and the non-uniform distribution of sources. X measurements within the basin have seasonal variation compared to the “background” due primarily to dynamics, or the origins of air masses coming into the basin. We observe basin−background differences that are in close agreement for 3 observing systems: TCCON 2.3 ± 1.2ppm, OCO-2 2.4 ± 1.5ppm, and GOSAT 2.4 ± 1.6ppm (errors are 1 σ ). We further observe persistent significant differences (∼0.9ppm) in X between two TCCON sites located only 9km apart within the SoCAB. We estimate 20% (±1 σ CI: 0%, 58%) of the variance is explained by a difference in elevation using a full physics and emissions model, and 36% (±1 σ CI: 10%, 101%) using a simple, fixed mixed layer model. This effect arises in the presence of a sharp gradient in CO 2 (or another species) between the mixed layer (ML) and free troposphere. Column differences between nearby locations arise when the change in elevation is greater than the change in ML height. This affects the fraction of atmosphere that is in the ML above each site. We show that such topographic effects produce significant variation in X across the SoCAB as well.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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