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Title: How can mountaintop CO 2 observations be used to constrain regional carbon fluxes?

Despite the need for researchers to understand terrestrial biospheric carbon fluxes to account for carbon cycle feedbacks and predict future CO 2 concentrations, knowledge of these fluxes at the regional scale remains poor. This is particularly true in mountainous areas, where complex meteorology and lack of observations lead to large uncertainties in carbon fluxes. Yet mountainous regions are often where significant forest cover and biomass are found – i.e., areas that have the potential to serve as carbon sinks. As CO 2 observations are carried out in mountainous areas, it is imperative that they are properly interpreted to yield information about carbon fluxes. In this paper, we present CO 2 observations at three sites in the mountains of the western US, along with atmospheric simulations that attempt to extract information about biospheric carbon fluxes from the CO 2 observations, with emphasis on the observed and simulated diurnal cycles of CO 2. We show that atmospheric models can systematically simulate the wrong diurnal cycle and significantly misinterpret the CO 2 observations, due to erroneous atmospheric flows as a result of terrain that is misrepresented in the model. This problem depends on the selected vertical level in the model and is exacerbatedmore » as the spatial resolution is degraded, and our results indicate that a fine grid spacing of ~4 km or less may be needed to simulate a realistic diurnal cycle of CO 2 for sites on top of the steep mountains examined here in the American Rockies. In conclusion, in the absence of higher resolution models, we recommend coarse-scale models to focus on assimilating afternoon CO 2 observations on mountaintop sites over the continent to avoid misrepresentations of nocturnal transport and influence.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ; ORCiD logo [2]
  1. Univ. of Utah, Salt Lake City, UT (United States). Dept. of Atmospheric Sciences
  2. National Center for Atmospheric Research, Boulder, CO (United States). Earth Observing Lab.
Publication Date:
Grant/Contract Number:
SC0010624; SC0010625
Type:
Published Article
Journal Name:
Atmospheric Chemistry and Physics (Online)
Additional Journal Information:
Journal Name: Atmospheric Chemistry and Physics (Online); Journal Volume: 17; Journal Issue: 9; Journal ID: ISSN 1680-7324
Publisher:
European Geosciences Union
Research Org:
Univ. of Utah, Salt Lake City, UT (United States)
Sponsoring Org:
USDOE Office of Science (SC); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1355135
Alternate Identifier(s):
OSTI ID: 1368184