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Emissions and topographic effects on column CO 2 ( X CO 2 ) variations, with a focus on the Southern California Megacity
Author(s) -
Hedelius Jacob K.,
Feng Sha,
Roehl Coleen M.,
Wunch Debra,
Hillyard Patrick W.,
Podolske James R.,
Iraci Laura T.,
Patarasuk Risa,
Rao Preeti,
O'Keeffe Darragh,
Gurney Kevin R.,
Lauvaux Thomas,
Wennberg Paul O.
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2017jd026455
Subject(s) - troposphere , structural basin , environmental science , atmospheric sciences , greenhouse gas , satellite , climatology , elevation (ballistics) , atmosphere (unit) , geology , meteorology , geography , physics , oceanography , geomorphology , astronomy
Within the California South Coast Air Basin (SoCAB),XCO 2varies significantly due to atmospheric dynamics and the nonuniform distribution of sources.XCO 2measurements 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 three observing systems: Total Carbon Column Observing Network (TCCON) 2.3 ± 1.2 ppm, Orbiting Carbon Observatory‐2 (OCO‐2) 2.4 ± 1.5 ppm, and Greenhouse gases Observing Satellite 2.4 ± 1.6 ppm (errors are 1 σ ). We further observe persistent significant differences (∼0.9 ppm) inXCO 2between two TCCON sites located only 9 km apart within the SoCAB. We estimate that 20% (±1 σ confidence interval (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 any species (here we focus on CO 2 ) 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 inXCO 2across the SoCAB as well.