A meta-analysis of water vapor deuterium-excess in the midlatitude atmospheric surface layer

Lisa R. Welp, Xuhui Lee, Timothy J. Griffis, Xue Fa Wen, Wei Xiao, Shenggong Li, Xiaomin Sun, Zhongmin Hu, Maria Val Martin, Jianping Huang

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58 Scopus citations

Abstract

Deuterium-excess (d) in water is a combination of the oxygen (δ18O) and hydrogen (δD) isotope ratios, and its variability is thought to indicate the location and environmental conditions of the marine moisture source. In this study, we analyze d of water vapor (d v) from six sites, all between 37 and 44N to examine patterns in the atmospheric surface layer and identify the main drivers of variability. Two sites are in urban settings (New Haven, CT, USA and Beijing, China), two sites are in agricultural settings (Rosemount, MN, USA and Luancheng, China), and two sites are in natural ecosystems, a forest (Borden Forest, Ontario, Canada) and a grassland (Duolun, China). We found a robust diurnal cycle in dv at all sites with maximum values during mid-day. Isotopic land surface model simulations suggest that plant transpiration is one mechanism underlying the diurnal pattern. An isotopic large-eddy simulation model shows that entrainment of the free atmosphere into the boundary layer can also produce high d v values in mid-day. Daily mid-day means of dv were negatively correlated with local mid-day relative humidity and positively correlated with planetary boundary layer height at the North American sites, but not the Chinese sites. The mechanism for these differences is still undetermined. These results demonstrate that within the diurnal time scale, dv of the surface air at continental locations can be significantly altered by local processes, and is therefore not a conserved tracer of humidity from the marine moisture source region as has previously been assumed.

Original languageEnglish (US)
Article numberGB3021
JournalGlobal Biogeochemical Cycles
Volume26
Issue number3
DOIs
StatePublished - 2012

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