Journal
ATMOSPHERIC CHEMISTRY AND PHYSICS
Volume 15, Issue 20, Pages 11773-11788Publisher
COPERNICUS GESELLSCHAFT MBH
DOI: 10.5194/acp-15-11773-2015
Keywords
-
Funding
- Canadian Space Agency (CSA)
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- NASA Atmospheric CO2 Observations from Space (ACOS) program [NNX10AT42G]
- Sweden (SNSB)
- Canada (CSA)
- France (CNES)
- Finland (Tekes)
- NASA Goddard Earth Science Data and Information Services Center
- NASA [NNX10AT42G, 122543] Funding Source: Federal RePORTER
Ask authors/readers for more resources
The upper troposphere and lower stratosphere (UTLS) represents a transition region between the more dynamically active troposphere and more stably stratified stratosphere. The region is characterized by strong gradients in the distribution of long-lived tracers, whose representation in models is sensitive to discrepancies in transport. We evaluate the GEOS-Chem model in the UTLS using carbon dioxide (CO2) and ozone (O-3) observations from the HIAPER (The High-Performance Instrumented Airborne Platform for Environmental Research) Pole-to-Pole Observations (HIPPO) campaign in March 2010. GEOS-Chem CO2/O-3 correlation suggests that there is a discrepancy in mixing across the tropopause in the model, which results in an overestimate of CO2 and an underestimate of O-3 in the Arctic lower stratosphere. We assimilate stratospheric O-3 data from the Optical Spectrograph and InfraRed Imager System (OSIRIS) and use the assimilated O-3 fields together with the HIPPO CO2/O-3 correlations to obtain an adjustment to the modeled CO2 profile in the Arctic UTLS (primarily between the 320 and 360K isentropic surfaces). The HIPPO-derived adjustment corresponds to a sink of 0.60 Pg C for March-August 2010 in the Arctic. Imposing this adjustment results in a reduction in the CO2 sinks inferred from GOSAT observations for temperate North America, Europe, and tropical Asia of 19, 13, and 49 %, respectively. Conversely, the inversion increased the source of CO2 from tropical South America by 23 %. We find that the model also underestimates CO2 in the upper tropical and subtropical troposphere. Correcting for the underestimate in the model relative to HIPPO in the tropical upper troposphere leads to a reduction in the source from tropical South America by 77 %, and produces an estimated sink for tropical Asia that is only 19% larger than the standard inversion (without the imposed source and sink). Globally, the inversion with the Arctic and tropical adjustment produces a sink of -6.64 Pg C, which is consistent with the estimate of -6.65 Pg C in the standard inversion. However, the standard inversion produces a stronger northern land sink by 0.98 Pg C to account for the CO2 overestimate in the high-latitude UTLS, suggesting that this UTLS discrepancy can impact the latitudinal distribution of the inferred sources and sinks. We find that doubling the model resolution from 4 degrees x 5 degrees to 2 degrees x 2.5 degrees enhances the CO2 vertical gradient in the high-latitude UTLS, and reduces the overestimate in CO2 in the extratropical lower stratosphere. Our results illustrate that discrepancies in the CO2 distribution in the UTLS can affect CO2 flux inversions and suggest the need for more careful evaluation of model errors in the UTLS.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available