scholarly journals Continuous monitoring of summer surface water vapor isotopic composition above the Greenland Ice Sheet

2013 ◽  
Vol 13 (9) ◽  
pp. 4815-4828 ◽  
Author(s):  
H. C. Steen-Larsen ◽  
S. J. Johnsen ◽  
V. Masson-Delmotte ◽  
B. Stenni ◽  
C. Risi ◽  
...  
Keyword(s):  
Water Vapor ◽  
Surface Water ◽  
Isotopic Composition ◽  
Large Scale ◽  
Near Infrared ◽  
Greenland Ice Sheet ◽  
Weather Conditions ◽  
Back Trajectory ◽  
Deuterium Excess ◽  
Air Mass

Abstract. We present here surface water vapor isotopic measurements conducted from June to August 2010 at the NEEM (North Greenland Eemian Drilling Project) camp, NW Greenland (77.45° N, 51.05° W, 2484 m a.s.l.). Measurements were conducted at 9 different heights from 0.1 m to 13.5 m above the snow surface using two different types of cavity-enhanced near-infrared absorption spectroscopy analyzers. For each instrument specific protocols were developed for calibration and drift corrections. The inter-comparison of corrected results from different instruments reveals excellent reproducibility, stability, and precision with a standard deviations of ~ 0.23‰ for δ18O and ~ 1.4‰ for δD. Diurnal and intraseasonal variations show strong relationships between changes in local surface humidity and water vapor isotopic composition, and with local and synoptic weather conditions. This variability probably results from the interplay between local moisture fluxes, linked with firn–air exchanges, boundary layer dynamics, and large-scale moisture advection. Particularly remarkable are several episodes characterized by high (> 40‰) surface water vapor deuterium excess. Air mass back-trajectory calculations from atmospheric analyses and water tagging in the LMDZiso (Laboratory of Meteorology Dynamics Zoom-isotopic) atmospheric model reveal that these events are associated with predominant Arctic air mass origin. The analysis suggests that high deuterium excess levels are a result of strong kinetic fractionation during evaporation at the sea-ice margin.

scholarly journals Continuous monitoring of summer surface water vapour isotopic composition above the Greenland Ice Sheet

2013 ◽  
Vol 13 (1) ◽  
pp. 1399-1433 ◽  
Author(s):  
H. C. Steen-Larsen ◽  
S. J. Johnsen ◽  
V. Masson-Delmotte ◽  
B. Stenni ◽  
C. Risi ◽  
...  
Keyword(s):  
Water Vapor ◽  
Surface Water ◽  
Isotopic Composition ◽  
Large Scale ◽  
Near Infrared ◽  
Greenland Ice Sheet ◽  
Weather Conditions ◽  
Back Trajectory ◽  
Deuterium Excess ◽  
Air Mass

Abstract. We present here surface water vapor isotopic measurements conducted from June to August~2010 at the NEEM camp, NW-Greenland (77.45° N 51.05° W, 2484 m a.s.l.). Measurements were conducted at 9 different heights from 0.1 m to 13.5 m above the snow surface using two different types of cavity-enhanced near infrared absorption spectroscopy analyzers. For each instrument specific protocols were developed for calibration and drift corrections. The inter-comparison of corrected results from different instruments reveals excellent reproducibility, stability, and precision with a standard deviation of ~ 0.23‰ for δ18O and ~ 1.4‰ for δD. Diurnal and intra-seasonal variations show strong relationships between changes in local surface humidity and water vapor isotopic composition, and with local and synoptic weather conditions. This variability probably results from the interplay between local moisture fluxes, linked with firn-air exchanges, boundary layer dynamics, and large-scale moisture advection. Particularly remarkable are several episodes characterized by high (> 40‰) surface water vapor deuterium excess. Air mass back-trajectory calculations from atmospheric analyses and water tagging in the LMDZiso atmospheric model reveal that these events are associated with predominant Arctic air mass origin. The analysis suggests that high deuterium excess levels are a result of strong kinetic fractionation during evaporation at the sea ice margin.

A Stochastic Model for Diagnosing Subtropical Humidity Dynamics with Stable Isotopologues of Water Vapor

2016 ◽  
Vol 73 (4) ◽  
pp. 1741-1753 ◽  
Author(s):  
Joseph Galewsky ◽  
David Rabanus
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Stochastic Model ◽  
Isotopic Composition ◽  
Model Parameters ◽  
Mixing Ratio ◽  
Deuterium Excess ◽  
Freeze Dried ◽  
Saturation Distribution ◽  
Cold Point

Abstract The humidity of the free troposphere can be modeled, to first order, in terms of cold-point dehydration, followed by moistening via mixing with boundary layer air. The relative balance between these processes is of prime interest for understanding interannual variability of humidity and for understanding the water vapor feedback. Measurements of water vapor isotopic composition can provide quantitative constraints on these processes. The authors developed a stochastic model that parameterizes water vapor isotopic composition in terms of these processes and fit the model parameters to data from the Chajnantor Plateau, Chile (23°S). For August–November 2012, the average mixing ratio was 1680 ppmv, with mean water vapor δD of −234‰ and mean deuterium excess of 21‰. The data were best fit by an asymmetric last-saturation distribution with mean last-saturation mixing ratio rs of 391 (+45, −75) ppmv, a median rs of 368 (+45, −75) ppmv, and a mean mixing fraction between the freeze-dried air and moist boundary layer air of . Measurements from August to November 2014 had an average mixing ratio of 2210 ppmv, an average δD of −220‰, and an average deuterium excess of 14‰. The last-saturation distribution for this period was less skewed than for 2012, with an average rs of 520 (+42, −75) ppmv and a median rs of 507 (+25, −75) ppmv. The mean mixing fraction for 2014 was . The results show that the moistening in 2014, relative to 2012, requires increases in both the last-saturation mixing ratio and the postcondensation moistening and illustrate the utility of isotopic measurements for constraining the processes governing subtropical humidity.

scholarly journals Relationships between submicrometer particulate air pollution and air mass history in Beijing, China, 2004–2006

2008 ◽  
Vol 8 (20) ◽  
pp. 6155-6168 ◽  
Author(s):  
B. Wehner ◽  
W. Birmili ◽  
F. Ditas ◽  
Z. Wu ◽  
M. Hu ◽  
...  
Keyword(s):  
Air Pollution ◽  
Large Scale ◽  
Northwest China ◽  
Back Trajectory ◽  
Anthropogenic Aerosol ◽  
Air Mass ◽  
Air Masses ◽  
Rapid Economic Growth ◽  
Trajectory Classification ◽  
History Of

Abstract. The Chinese capital Beijing is one of the global megacities where the effects of rapid economic growth have led to complex air pollution problems that are not well understood. In this study, ambient particle number size distributions in Beijing between 2004 and 2006 are analysed as a function of regional meteorological transport. An essential result is that the particle size distribution in Beijing depends to large extent on the history of the synoptic scale air masses. A first approach based on manual back trajectory classification yielded differences in particulate matter mass concentration by a factor of two between four different air mass categories, including three main wind directions plus the case of stagnant air masses. A back trajectory cluster analysis refined these results, yielding a total of six trajectory clusters. Besides the large scale wind direction, the transportation speed of an air mass was found to play an essential role on the PM concentrations in Beijing. Slow-moving air masses were shown to be associated with an effective accumulation of surface-based anthropogenic emissions due to both, an increased residence time over densely populated land, and their higher degree of vertical stability. For the six back trajectory clusters, differences in PM1 mass concentrations by a factor of 3.5, in the mean air mass speed by a factor of 6, and in atmospheric visibility by a factor of 4 were found. The main conclusion is that the air quality in Beijing is not only degraded by anthropogenic aerosol sources from within the megacity, but also by sources across the entire Northwest China plain depending on the meteorological situation.

scholarly journals Craig-Gordon model validation using observed meteorological parameters and measured stable isotope ratios in water vapor over the Southern Ocean

2019 ◽  
Author(s):  
Shaakir Shabir Dar ◽  
Prosenjit Ghosh ◽  
Ankit Swaraj ◽  
Anil Kumar
Keyword(s):  
Water Vapor ◽  
Surface Water ◽  
Southern Ocean ◽  
Isotopic Composition ◽  
Isotope Ratios ◽  
Mixing Processes ◽  
Relative Contribution ◽  
Molecular Diffusivity ◽  
Air Interface ◽  
Evaporation Flux

Abstract. The stable isotopic composition of water vapor over the ocean is governed by the isotopic composition of surface water, ambient vapor isotopic composition, exchange and mixing processes at the water-air interface as well as the local meteorological conditions. In this study we present water vapor and surface water isotope ratios in samples collected across the latitudinal transect from Mauritius to Prydz Bay in the Antarctic coast. The samples were collected on-board the ocean research vessel SA Agulhas during the 9th (Jan-2017) and 10th (Dec-2017 to Jan-2018) Southern Ocean expeditions. The inter annual variability of the meteorological factors governing water vapor isotopic composition is explained. The parameters governing the isotopic composition of evaporation flux from the oceans can be considered separately or simultaneously in the Craig-Gordon (CG) models. The Traditional Craig-Gordon (TCG) (Craig and Gordon, 1965) and the Unified Craig-Gordon (UCG) (Gonfiantini et al., 2018) models were used to evaluate the isotopic composition of evaporation flux for the molecular diffusivity ratios suggested by Merlivat (1978) (MJ), Cappa et al. (2003) (CD) and Pfahl and Wernli (2009) (PW) and for different ocean surface conditions. We found that the UCG model with CD molecular diffusivity ratios where equal contribution from molecular and turbulent diffusion is the best match for our observations. By assigning the representative end member isotopic compositions and solving the two-component mixing model, a relative contribution from locally generated and advected moisture was calculated along the transect. Our results suggest varying contribution of advected westerly component with an increasing trend upto 65° S. Beyond 65° S, the proportion of Antarctic moisture was found to be increasing linearly towards the coast.

scholarly journals Deuterium excess in atmospheric water vapor of a Mediterranean coastal wetland: regional versus local signatures

2015 ◽  
Vol 15 (2) ◽  
pp. 1703-1746 ◽  
Author(s):  
H. Delattre ◽  
C. Vallet-Coulomb ◽  
C. Sonzogni
Keyword(s):  
Water Vapor ◽  
Coastal Wetland ◽  
Deuterium Excess ◽  
Atmospheric Water ◽  
Time Step ◽  
Vapor Source ◽  
Air Mass ◽  
Air Masses ◽  
Clear Separation ◽  
Hourly Data

Abstract. Stable isotopes of the water vapor represent a powerful tool for tracing atmospheric vapor origin and mixing processes. Laser spectrometry recently allowed high time resolution measurements, but despite an increasing number of experimental studies, there is still a need for a better understanding of the main drivers of isotopic signal variability at different time scales. We present results of in situ measurements of δ18O and δD during 36 consecutive days in summer 2011 in atmospheric vapor of a Mediterranean coastal wetland exposed to high evapotranspiration (Camargue, Rhône River delta, France). A calibration protocol was tested and instrument stability was analysed over the period. The mean composition of atmospheric vapor during the campaign is δ18O = −14.66‰ and δD = −95.4‰, with δv data plotting clearly above the local meteoric water line, and an average deuterium excess (dv) of 21.9‰. At daily time step, we show a clear separation of isotopic characteristics with respect to the air mass back trajectories, with the Northern air masses providing depleted compositions (δ18O = −15.83‰, δD = −103.5‰) compared to Mediterranean air masses (δ18O = −13.13‰, δD = −86.5‰). There is also a clear separation between dv corresponding to these different air mass origins, but not in the same direction as was previously evidenced from regional rainfall data, with higher dv found for Northern air masses (23.2‰) than for Mediterranean air masses (18.6‰). Based on twenty-four average hourly data, we propose a depiction of typical daily evolution of water vapor isotopic composition. High diurnal variations in dv is attributed to a dominant control of evapotranspiration, over entrainment of free atmosphere. Daily cycles in dv are more pronounced for Mediterranean than for North Atlantic air mass origin and are discussed in terms of local evapotranspiration versus regional signatures. We calculate the composition of the vapor source that produces the day-time increase in dv for the different air mass origins, and propose an atmospheric water and isotopic mass balance.

scholarly journals Seasonality of moisture supplies to precipitation over the Third Pole: a stable water isotopic perspective

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Xiaoxin Yang ◽  
Tandong Yao
Keyword(s):  
Water Vapor ◽  
Isotopic Composition ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Potential Effect ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Physical Processes ◽  
Large Scale Atmospheric Circulation

Abstract This study integrated isotopic composition in precipitation at 50 stations on and around the Tibetan Plateau (TP) and demonstrated the distinct seasonality of isotopic composition in precipitation across the study period. The potential effect of water vapor isotopes on precipitation isotopes is studied by comparing the station precipitation data with extensive isotopic patterns in atmospheric water vapor, revealing the close linkage between the two. The analysis of contemporary water vapor transport and potential helps confirm the different mechanisms behind precipitation isotopic compositions in different areas, as the southern TP is more closely related to large-scale atmospheric circulation such as local Hadley and summer monsoon circulations during other seasons than winter, while the northern TP is subject to the westerly prevalence and advective moisture supply and precipitation processes. The new data presented in this manuscript also enrich the current dataset for the study of precipitation isotopes in this region and together provide a valuable database for verification of the isotope-integrated general circulation model and explanation of related physical processes.

Constraining Supersaturation and Transport Processes in a South American Cold-Air Outbreak Using Stable Isotopologues of Water Vapor

2015 ◽  
Vol 72 (5) ◽  
pp. 2055-2069 ◽  
Author(s):  
Joseph Galewsky
Keyword(s):  
Water Vapor ◽  
Isotopic Composition ◽  
Mesoscale Model ◽  
Path Following ◽  
Transport Processes ◽  
Back Trajectory ◽  
South American ◽  
Cold Air ◽  
Cold Air Outbreak ◽  
Δd And Δ18o

Abstract In situ measurements of water vapor isotopic composition from the subtropical Chilean Andes, supported by mesoscale model simulations and diagnostic analyses, document the processes governing the transport of dry air and isotopically depleted water vapor from the midlatitudes into the subtropics during a South American cold-air surge in July 2014. On 23 July 2014, temperatures on the Chajnantor Plateau reached −18°C, among the lowest temperatures on record for the site. On 26 July 2014, water vapor δD and δ18O reached a low of −538 ± 1.6‰ and −71.7 ± 0.2‰, among the lowest values on record. Numerical simulations show that the dynamics of the event were consistent with previous studies of South American cold-air outbreaks. Back-trajectory analyses show that the isotopically depleted water vapor that reached Chajnantor on July 26 was last saturated over the South Pacific on July 23 at 300 hPa at a temperature of about −50°C under ice supersaturation with RHice of about 110%. The water vapor traveled to Chajnantor along a nearly isentropic path following saturation. Modeling of the isotopic data require condensation at temperatures between −50°C and −53°C under supersaturation with RHice between 112% and 118%, followed by less than 25% moistening during transport. These results show that measurements of water vapor isotopic composition can provide observational constraints on in-cloud processes that influence the humidity of the subtropics.

scholarly journals A Study of the Free Tropospheric Humidity Interannual Variability Using Meteosat Data and an Advection–Condensation Transport Model

2009 ◽  
Vol 22 (24) ◽  
pp. 6773-6787 ◽  
Author(s):  
Hélène Brogniez ◽  
Rémy Roca ◽  
Laurence Picon
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Interannual Variability ◽  
Large Scale ◽  
Transport Model ◽  
Radiation Budget ◽  
Lagrangian Model ◽  
Back Trajectory ◽  
Good Proxy

Abstract Water vapor in the midtroposphere is an important element for the earth radiation budget. Despite its importance, the relative humidity in the free troposphere is not very well documented, mainly because of the difficulties associated with its measurements. A new long-term archive of free tropospheric humidity (FTH) derived from the water vapor channel of the Meteosat satellite from 1983 to 2005 is introduced. Special attention is dedicated to the long-term homogeneity and the definition of the retrieval layer. It is shown to complement the existing databases and is used to establish the climatology of FTH. Interannual variability is then evaluated for each season by using a normalized interannual standard deviation. This normalization approach reveals the importance of the relative variability of the dry areas to the moist regions. In consequence, emphasis is on the driest area of the region. Focusing on composites of the moist and dry seasons of the time series, the authors demonstrate that the 500-hPa relative humidity field, reconstructed using an idealized Lagrangian model, is a good proxy for the FTH variability there. The analysis of the origin of the air mass, using the back trajectory model, points out that lateral mixing between the deep tropics and extratropical latitudes takes place over this area, as advocated in previous theoretical studies. Systematic estimation of this large-scale mixing shows that, indeed, a significant part of the interannual variability of the free tropospheric humidity in this subtropical region stems from the amount of mixing of air originating from the deep tropics versus extratropical latitudes. The importance of this mechanism in the general understanding of the FTH distribution and variability is then discussed.

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