气候变化领域集成服务门户(CCPortal): Simulation of radon-222 with the GEOS-Chem global model: Emissions; seasonality; and convective transport

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DOI	10.5194/acp-21-1861-2021
	Simulation of radon-222 with the GEOS-Chem global model: Emissions; seasonality; and convective transport
	Zhang B.; Liu H.; Crawford J.H.; Chen G.; Duncan Fairlie T.; Chambers S.; Kang C.-H.; Williams A.G.; Zhang K.; Considine D.B.; Sulprizio M.P.; Yantosca R.M.
发表日期	2021
ISSN	1680-7316
起始页码	1861
结束页码	1887
卷号	21 期号:3
英文摘要	Radon-222 (222Rn) is a short-lived radioactive gas naturally emitted from land surfaces and has long been used to assess convective transport in atmospheric models. In this study, we simulate 222Rn using the GEOS-Chem chemical transport model to improve our understanding of 222Rn emissions and surface concentration seasonality and characterize convective transport associated with two Goddard Earth Observing System (GEOS) meteorological products, the Modern-Era Retrospective analysis for Research and Applications (MERRA) and GEOS Forward Processing (GEOS-FP). We evaluate four global 222Rn emission scenarios by comparing model results with observations at 51 surface sites. The default emission scenario in GEOSChem yields a moderate agreement with surface observations globally (68.9 % of data within a factor of 2) and a large underestimate of winter surface 222Rn concentrations at Northern Hemisphere midlatitudes and high latitudes due to an oversimplified formulation of 222Rn emission fluxes (1 atom cm-2 s-1 over land with a reduction by a factor of 3 under freezing conditions). We compose a new global 222Rn emission scenario based on Zhang et al. (2011) and demonstrate its potential to improve simulated surface 222Rn concentrations and seasonality. The regional components of this scenario include spatially and temporally varying emission fluxes derived from previous measurements of soil radium content and soil exhalation models, which are key factors in determining 222Rn emission flux rates. However, large model underestimates of surface 222Rn concentrations still exist in Asia, suggesting unusually high regional 222Rn emissions. We therefore propose a conservative upscaling factor of 1.2 for 222Rn emission fluxes in China, which was also constrained by observed deposition fluxes of 210Pb (a progeny of 222Rn). With this modification, the model shows better agreement with observations in Europe and North America (> 80 % of data within a factor of 2) and reasonable agreement in Asia (close to 70 %). Further constraints on 222Rn emissions would require additional concentration and emission flux observations in the central United States, Canada, Africa, and Asia. We also compare and assess convective transport in model simulations driven by MERRA and GEOS-FP using observed 222Rn vertical profiles in northern midlatitude summer and from three short-term airborne campaigns. While simulations with both GEOS products are able to capture the observed vertical gradient of 222Rn concentrations in the lower troposphere (0 4 km), neither correctly represents the level of convective detrainment, resulting in biases in the middle and upper troposphere. Compared with GEOS-FP, MERRA leads to stronger convective transport of 222Rn, which is partially compensated for by its weaker large-scale vertical advection, resulting in similar global vertical distributions of 222Rn concentrations between the two simulations. This has important implications for using chemical transport models to interpret the transport of other trace species when these GEOS products are used as driving meteorology. © 2021 Author(s).
语种	英语
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/168774
作者单位	National Institute of Aerospace, Hampton, VA, United States; NASA Langley Research Center, Hampton, VA, United States; Australian Nuclear Science and Technology Organization, Kirrawee, NSW, Australia; Department of Chemistry, Jeju National University, Jeju, South Korea; Pacific Northwest National Laboratory, Richland, WA, United States; NASA Headquarters, Washington, DC, United States; John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, United States
推荐引用方式 GB/T 7714	Zhang B.,Liu H.,Crawford J.H.,et al. Simulation of radon-222 with the GEOS-Chem global model: Emissions; seasonality; and convective transport[J],2021,21(3).
APA	Zhang B..,Liu H..,Crawford J.H..,Chen G..,Duncan Fairlie T..,...&Yantosca R.M..(2021).Simulation of radon-222 with the GEOS-Chem global model: Emissions; seasonality; and convective transport.Atmospheric Chemistry and Physics,21(3).
MLA	Zhang B.,et al."Simulation of radon-222 with the GEOS-Chem global model: Emissions; seasonality; and convective transport".Atmospheric Chemistry and Physics 21.3(2021).