TY - JOUR
T1 - Implementation of Improved Parameterization of Terrestrial Flux in WRF-VPRM Improves the Simulation of Nighttime CO2 Peaks and a Daytime CO2 Band Ahead of a Cold Front
AU - Hu, Xiao Ming
AU - Gourdji, Sharon M.
AU - Davis, Kenneth J.
AU - Wang, Qingyu
AU - Zhang, Yao
AU - Xue, Ming
AU - Feng, Sha
AU - Moore, Berrien
AU - Crowell, Sean M.R.
N1 - Funding Information:
This study was supported by the Atmospheric Carbon and Transport (ACT)‐America project through Grant NNX17AG11G at OU and Grant NNX15AG76G at Penn State. The ACT‐America project is a NASA Earth Venture Suborbital 2 project funded by NASA's Earth Science Division. The last author was supported by NASA OCO‐2 program under Grant 80NSSC18K0896. Computations were performed at the San Diego Supercomputer Center (SDSC) through XSEDE allocation Grant TG‐ATM160014. References are made to certain commercially available products in this paper to adequately specify the experimental procedures involved. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that these products are the best for the purpose specified.
Funding Information:
This study was supported by the Atmospheric Carbon and Transport (ACT)-America project through Grant NNX17AG11G at OU and Grant NNX15AG76G at Penn State. The ACT-America project is a NASA Earth Venture Suborbital 2 project funded by NASA's Earth Science Division. The last author was supported by NASA OCO-2 program under Grant 80NSSC18K0896. Computations were performed at the San Diego Supercomputer Center (SDSC) through XSEDE allocation Grant TG-ATM160014. References are made to certain commercially available products in this paper to adequately specify the experimental procedures involved. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that these products are the best for the purpose specified.
Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.
PY - 2021/5/27
Y1 - 2021/5/27
N2 - Enhanced CO2 mole fraction bands were often observed immediately ahead of cold front during the Atmospheric Carbon and Transport (ACT)-America mission and their formation mechanism is undetermined. Improved understanding and correct simulation of these CO2 bands are needed for unbiased inverse CO2 flux estimation. Such CO2 bands are hypothesized to be related to nighttime CO2 respiration and investigated in this study using WRF-VPRM, a weather-biosphere-online-coupled model, in which the biogenic fluxes are handled by the Vegetation Photosynthesis and Respiration Model (VPRM). While the default VPRM satisfactorily parameterizes gross ecosystem exchange, its treatment of terrestrial respiration as a linear function of temperature was inadequate as respiration is a nonlinear function of temperature and also depends on the amount of biomass and soil wetness. An improved ecosystem respiration parameterization including enhanced vegetation index, a water stress factor, and a quadratic temperature dependence is incorporated into WRF-VPRM and evaluated in a year-long simulation before applied to the investigation of the frontal CO2 band on August 4, 2016. The evaluation shows that the modified WRF-VPRM increases ecosystem respiration during the growing season, and improves model skill in reproducing nighttime near-surface CO2 peaks. A nested-domain WRF-VPRM simulation is able to capture the main characteristics of the August 4 CO2 band and informs its formation mechanism. Nighttime terrestrial respiration leads to accumulation of near-surface CO2 in the region. As the cold front carrying low-CO2 air moves southeastward, and strong photosynthesis depletes CO2 further southeast of the front, a CO2 band develops immediately ahead of the front.
AB - Enhanced CO2 mole fraction bands were often observed immediately ahead of cold front during the Atmospheric Carbon and Transport (ACT)-America mission and their formation mechanism is undetermined. Improved understanding and correct simulation of these CO2 bands are needed for unbiased inverse CO2 flux estimation. Such CO2 bands are hypothesized to be related to nighttime CO2 respiration and investigated in this study using WRF-VPRM, a weather-biosphere-online-coupled model, in which the biogenic fluxes are handled by the Vegetation Photosynthesis and Respiration Model (VPRM). While the default VPRM satisfactorily parameterizes gross ecosystem exchange, its treatment of terrestrial respiration as a linear function of temperature was inadequate as respiration is a nonlinear function of temperature and also depends on the amount of biomass and soil wetness. An improved ecosystem respiration parameterization including enhanced vegetation index, a water stress factor, and a quadratic temperature dependence is incorporated into WRF-VPRM and evaluated in a year-long simulation before applied to the investigation of the frontal CO2 band on August 4, 2016. The evaluation shows that the modified WRF-VPRM increases ecosystem respiration during the growing season, and improves model skill in reproducing nighttime near-surface CO2 peaks. A nested-domain WRF-VPRM simulation is able to capture the main characteristics of the August 4 CO2 band and informs its formation mechanism. Nighttime terrestrial respiration leads to accumulation of near-surface CO2 in the region. As the cold front carrying low-CO2 air moves southeastward, and strong photosynthesis depletes CO2 further southeast of the front, a CO2 band develops immediately ahead of the front.
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U2 - 10.1029/2020JD034362
DO - 10.1029/2020JD034362
M3 - Article
AN - SCOPUS:85105822249
VL - 126
JO - Journal of Geophysical Research: Atmospheres
JF - Journal of Geophysical Research: Atmospheres
SN - 2169-897X
IS - 10
M1 - e2020JD034362
ER -