Stable isotope composition of water vapor in the atmospheric boundary layer above the forests of New England

He, Hui; Smith, Ronald B.

doi:10.1029/1999jd900080

Cited by 69 publications

(85 citation statements)

References 27 publications

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“…This finding has since been supported by large-scale advection models that reproduce, to first order, the isotope ratios observed in the subtropical free troposphere near Hawaii [Galewsky et al, 2007;Hurley et al, 2012]. In addition, He and Smith [1999] characterized moisture transport between the land surface and free atmosphere by pairing measurements of humidity and the stable isotope ratio in a simple mixing model.…”

Section: Introductionmentioning

confidence: 71%

“…When conditions are unsaturated, both q and the isotope ratio are conserved variables, and airmass mixing will cause observations to fall along a line in δ-1/q space [e.g., He and Smith, 1999;Noone et al, 2011]. In contrast, if an air mass experiences a pseudoadiabatic process, in which condensate is immediately removed as precipitation, its δ value follows a theoretical Rayleigh distillation [e.g., Dansgaard, 1964].…”

Section: Isotopic Models For the Convective Boundary Layermentioning

confidence: 99%

“…[18] Due to differences in the saturation vapor pressures of heavy and light isotopologues of water [Bigeleisen, 1961], the relationship between the isotope ratio and observed vapor mixing ratio provides a valuable diagnostic for moisture fluxes [Gat, 1996;He and Smith, 1999;Noone et al, 2011] and a means to distinguish moistening and dehydrating mechanisms [Worden et al, 2007;Noone, 2012]. When conditions are unsaturated, both q and the isotope ratio are conserved variables, and airmass mixing will cause observations to fall along a line in δ-1/q space [e.g., He and Smith, 1999;Noone et al, 2011].…”

Section: Isotopic Models For the Convective Boundary Layermentioning

confidence: 99%

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Characterizing moisture exchange between the Hawaiian convective boundary layer and free troposphere using stable isotopes in water

2013

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[1] The subtropical convective boundary layer (CBL) plays a critical role in climate by regulating the vertical exchange of moisture, energy, trace gases, and pollutants between the ocean surface and free troposphere. Yet bulk features of this exchange are poorly constrained in climate models. To improve our understanding of moisture transport between the boundary layer and free troposphere, paired measurements of water vapor mixing ratio and the stable isotope ratio 18 O/ 16 O are used to evaluate moist convective mixing and entrainment processes near the Big Island of Hawaii. Profile data from the island's east side are consistent with moist adiabatic processes below the trade wind temperature inversion. In contrast, profiles on the west side follow moist adiabatic lapse rates within discrete stable layers, suggesting moist convection sets the humidity structure of even the unsaturated regions around the island. Above the trade wind inversion, the transition from well-mixed boundary layer to free troposphere is characterized by a simple mixing line analysis, so long as the thermodynamic properties of the air mass at CBL top are known. Deviations from the mixing line identify thermodynamic boundaries in the atmospheric profile, which can persist from one day to the next. These findings indicate residual layers form during strong mixing events and regulate vertical moisture transport for multiple days at a time. Basic assumptions that synoptic-scale transport controls isotope ratios at CBL top are therefore not sufficient for describing moisture exchange between the boundary layer and free troposphere in the subtropics.Citation: Bailey, A., D. Toohey, and D. Noone (2013), Characterizing moisture exchange between the Hawaiian convective boundary layer and free troposphere using stable isotopes in water,

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Section: Introductionmentioning

confidence: 71%

Section: Isotopic Models For the Convective Boundary Layermentioning

confidence: 99%

Section: Isotopic Models For the Convective Boundary Layermentioning

confidence: 99%

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Characterizing moisture exchange between the Hawaiian convective boundary layer and free troposphere using stable isotopes in water

2013

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“…As a rule of thumb, the δD of water vapor gradually decreases with altitude, which reflects the integrated history of condensation (e.g., Ehhalt et al 2005). While none of the previous observational studies have described the vertical profile of d-excess, calculated d-excess from isotopic profiles reported by He and Smith (1999) showed that the d-excess values at the top of a boundary layer are significantly higher than those at the surface. From these results, we can speculate that the δD (d-excess) values of water vapor impinging on the mountain region are lower (higher) than those for the marine air mass.…”

Section: Atmospheric Process Responsible For Warm Eventsmentioning

confidence: 96%

Identification of Air Masses Responsible for Warm Events on the East Antarctic Coast

Kurita

Hirasawa

Koga

et al. 2016

SOLA

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Warm events, periods when rising surface air temperatures can trigger surface melt, have been recorded during the austral summer at Syowa station on the East Antarctic coast. This study identifies air masses responsible for summer warm events at Syowa. Air masses arriving at Syowa are classified into marine and glacial sources based on their isotopic characteristics. Warm events are not associated with moist marine air intrusion, but with the downward flow of dry glacial air along the west side slope of the mountains in Enderby Land (EL). We use simulations from the Antarctic Mesoscale Prediction System (AMPS) to explore the atmospheric process responsible for the warmest event at Syowa. The model output illustrates several foehn-associated features such as low-level blocking, precipitation on the mountain's windward side, and mountain wave activity, with warm air ascending on the upstream slope and descending to Syowa. The foehn warming is caused by an easterly cross-mountain flow associated with a low-pressure system to the north of the EL coast. Future changes in synoptic cyclonic activity off the EL coast may have a significant impact on the frequency and intensity of foehn events at Syowa and the associated coastal warm events.(Citation: Kurita, N., N. Hirasawa, S. Koga, J. Matsushita, H. C. Steen-Larsen, V. Masson-Delmotte, and Y. Fujiyoshi, 2016: Identification of air mass responsible for warm events on the East

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“…Note that the transpiration component of evapotranspiration is not expected to carry high d, as it has the same isotopic composition as the soil water at steady state (Yakir and Wang, 1996;Williams et al, 2004). In addition, the free atmospheric air is characterized by a isotopically lighter vapour (He and Smith, 1999;Bailey et al, 2013;Berkelhammer et al, 2013), and the dominance of entrainment during daytime is generally associated with a δ v depletion (Lai et al, 2006;Lai and Ehleringer, 2011;Tremoy et al, 2012;Bailey et al, 2013;Berkelhammer et al, 2013). Welp et al (2012) compared six measurement locations and found that both local evapotranspiration and entrainment were involved: in some of their sites, the d daily increase was associated with a δ 18 O decrease during the early morning due to entrainment of free atmosphere into the boundary layer during convective mixing, while the subsequent slight δ 18 O increase came from evapotranspiration.…”

Section: Daytime Processes: Contribution Of Local Evaporationmentioning

confidence: 99%

Deuterium excess in the atmospheric water vapour of a Mediterranean coastal wetland: regional vs. local signatures

2015

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Abstract. Stable isotopes of water vapour represent a powerful tool for tracing atmospheric vapour origin and mixing processes. Laser spectrometry recently allowed high timeresolution measurements, but despite an increasing number of experimental studies, there is still a need for a better understanding of the isotopic signal variability at different time scales. We present results of in situ measurements of δ 18 O and δD during 36 consecutive days in summer 2011 in atmospheric vapour of a Mediterranean coastal wetland exposed to high evaporation (Camargue, Rhône River delta, France). The mean composition of atmospheric vapour (δ v ) is δ 18 O = −14.66 ‰ and δD = −95.4 ‰, with data plotting clearly above the local meteoric water line on a δ 18 O-δD plot, and an average deuterium excess (d) of 21.9 ‰. Important diurnal d variations are observed, and an hourly time scale analysis is necessary to interpret the main processes involved in its variability. After having classified the data according to air mass back trajectories, we analyse the average daily cycles relating to the two main meteorological situations, i.e. air masses originating from North Atlantic Ocean and Mediterranean Sea. In both situations, we show that diurnal fluctuations are driven by (1) the influence of local evaporation, culminating during daytime, and leading to an increase in absolute water vapour concentration associated to a δ v enrichment and d increase; (2) vertical air mass redistribution when the Planetary Boundary Layer collapses in the evening, leading to a d decrease, and (3) dew formation during the night, producing a δ v depletion with d remaining stable. Using a twocomponent mixing model, we calculate the average composition of the locally evaporated vapour (δ E ). We find higher d (E) under North Atlantic air mass conditions, which is consistent with lower humidity conditions. We also suggest that δ v measured when the PBL collapses is the most representative of a regional signal. Strong, cold and dry winds coming from the north bring an isotopically depleted vapour, while light, warm and wet winds coming from the south bring an isotopically enriched vapour. Under northern conditions, a strong advection rate dilutes the contribution of the locally evaporated vapour (δ E ) to the ambient moisture (δ v ). The higher d values measured under northern conditions, compared to the Mediterranean situation, thus results from the combination of a higher d in both local and regional vapour. This depiction of typical daily cycles of water vapour isotopic composition can be used as a framework for further quantitative analyses of vapour sources during specific days.

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Stable isotope composition of water vapor in the atmospheric boundary layer above the forests of New England

Cited by 69 publications

References 27 publications

Characterizing moisture exchange between the Hawaiian convective boundary layer and free troposphere using stable isotopes in water

Characterizing moisture exchange between the Hawaiian convective boundary layer and free troposphere using stable isotopes in water

Identification of Air Masses Responsible for Warm Events on the East Antarctic Coast

Deuterium excess in the atmospheric water vapour of a Mediterranean coastal wetland: regional vs. local signatures

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