DOI: 10.1029/2012JD018212
论文题名: Identifying tropospheric baseline air masses at mauna loa observatory between 2004 and 2010 using radon-222 and back trajectories
作者: Chambers S.D. ; Zahorowski W. ; Williams A.G. ; Crawford J. ; Griffiths A.D.
刊名: Journal of Geophysical Research Atmospheres
ISSN: 21698996
出版年: 2013
卷: 118, 期: 2 起始页码: 992
结束页码: 1004
语种: 英语
Scopus关键词: Mixing
; Observatories
; Trajectories
; Troposphere
; Back trajectories
; Base-line conditions
; Budget calculation
; Lower troposphere
; Marine boundary layers
; Radon concentrations
; Trajectory information
; Upper troposphere
; Radon
; air mass
; amplitude
; boundary layer
; concentration (composition)
; flux measurement
; identification method
; marine environment
; observational method
; radon isotope
; sampling
; troposphere
英文摘要: We use 7 years of hourly radon observations atMauna Loa Observatory (MLO), together with 10-day back trajectories, to identify baseline air masses at the station. The amplitude of the annualMLO radon cycle, based on monthlymeans, was 98 mBqm-3 (39 -137mBq m-3), with maximum values in February (90th percentile 330 mBq m-3) and minimum values in August (10th percentile 8.1mBqm-3). The composite diurnal radon cycle (amplitude 49mBq m-3) is discussed with reference to the influences of local flow features affecting the site, and a 3-hour diurnal sampling window (0730-1030 HST) is proposed for observing the least terrestrially influenced tropospheric air masses. A set of 763 baseline events is selected, using the proposed sampling window together with trajectory information, and presented along with measured radon concentrations as a supplement. This data set represents a resource for the selection of baseline events at MLO for use with a range of trace species. A reduced set of 196 "deep baseline" events occurring in the July-September window is also presented and discussed. The distribution (10th/50th/90th percentile) of radon in deep-baseline events (8.7/29.2/66.1 mBq m-3) was considerably lower than that for the overall set of 763 baseline events (12.3/40.8/104.1 mBq m-3). Results from a simple budget calculation, using sonde-derived mixing depths and literature-based estimates of oceanic radon flux and radon concentrations in the marine boundary layer, indicate that the main source of residual radon in the lower troposphere under baseline conditions at MLO is downward mixing from aged terrestrial air masses in the upper troposphere. © 2012. American Geophysical Union.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/64023
Appears in Collections: 影响、适应和脆弱性 气候减缓与适应
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作者单位: Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia
Recommended Citation:
Chambers S.D.,Zahorowski W.,Williams A.G.,et al. Identifying tropospheric baseline air masses at mauna loa observatory between 2004 and 2010 using radon-222 and back trajectories[J]. Journal of Geophysical Research Atmospheres,2013-01-01,118(2)