The utility of near-surface water vapor deuterium excess as an indicator of atmospheric moisture source

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.

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Multi-year water vapor isotopes (δ18O/ δ2H) reveal dynamic drivers of moisture source and transport in the Barents Region

10.5194/egusphere-egu2020-15241 ◽

2020 ◽

Author(s):

Hannah Bailey ◽

Kaisa-Riikka Mustonen ◽

Eric Klein ◽

Pete Akers ◽

Ben Kopec ◽

...

Keyword(s):

Water Vapor ◽

Stable Isotope ◽

Sea Ice ◽

Transport Processes ◽

The Arctic ◽

Atmospheric Moisture ◽

Synoptic Scale ◽

Moisture Source ◽

Isotope Data ◽

Barents Region

Stable isotope ratios (&#948;18O and &#948;2H) in precipitation (P) and atmospheric water vapor (V) can provide mechanistic information about water cycle processes such as moisture evaporation, transport and recycling dynamics. Such insight is valuable in the Arctic where declining sea ice is amplifying atmospheric temperature and humidity, leading to complex seasonal patterns of synoptic climate and atmospheric moisture transport. Here, we present two years of continuous water vapor isotope data from Pallas-Yll&#228;stunturi National Park, northern Finland, to investigate moisture source and transport processes in the Barents Region of the Arctic. High-resolution (1-sec) measurements obtained between December 2017 and December 2019 are coupled with on-site automated weather station data &#8211; including air temperature, humidity, solar flux, wind speed and direction &#8211; as well as event-based precipitation sampling and stable isotope data over the same interval. Over the two-years, mean vapor &#948;18OV, &#948;2HV and d-excessV values are -24.50&#8240;, -181.49&#8240; and 14.49&#8240;, respectively. These values are strongly correlated and define a local vapor line for Pallas where &#948;2HV = 7.6 x &#948;18OV + 5.9 (R2=0.98). We observe a mean offset of 10.9 &#8240; between Pallas &#948;18OV and &#948;18OP, and d-excess is -4.8 &#8240; lower in &#948;18OP. There is a larger offset between vapor and precipitation d-excess during summer (-8.4&#8240;) compared to winter (0.1&#8240;) that may reflect varying fractionation coefficients between solid and liquid cloud-precipitation phases. The timeseries exhibits strong seasonality characterized by lower &#948;18OV/&#948;2HV and higher d-excess during winter, and the reverse during summer. In winter these broad patterns are primarily driven by synoptic-scale processes that influence the source and transport pathway of atmospheric moisture, and three dominant oceanic evaporative source regions are identified: the Barents, Norwegian, and Baltic Seas. Yet on diurnal timescales we observe distinct summer diel cycles that correlate with local fluctuations in specific humidity (q). These seasonal relationships are explored in context of spatial-temporal patterns in sea ice and snow cover distribution, as well as evapotranspiration processes across northern Eurasia. Finally, to better understand how current changes in the Arctic hydrologic cycle relate to inherent variability of the polar jet stream and related synoptic-scale weather, our isotope data are examined in context of dynamic circulation modes of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO).

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Characteristics of Seasonal Variation of Near-Surface Water Vapor D/H Isotope Ratio Revealed by Continuous in situ Measurement in Sapporo, Japan

SOLA ◽

10.2151/sola.2012-002 ◽

2012 ◽

Vol 8 ◽

pp. 5-8 ◽

Cited By ~ 4

Author(s):

‘Niyi Sunmonu ◽

Ken-ichiro Muramoto ◽

Naoyuki Kurita ◽

Kei Yoshimura ◽

Yasushi Fujiyoshi

Keyword(s):

Seasonal Variation ◽

Water Vapor ◽

Surface Water ◽

Isotope Ratio ◽

In Situ Measurement ◽

Near Surface

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What controls deuterium excess in global precipitation?

Climate of the Past ◽

10.5194/cp-10-771-2014 ◽

2014 ◽

Vol 10 (2) ◽

pp. 771-781 ◽

Cited By ~ 144

Author(s):

S. Pfahl ◽

H. Sodemann

Keyword(s):

Relative Humidity ◽

Empirical Relation ◽

Ice Cores ◽

Quantitative Agreement ◽

Sufficient Evidence ◽

Future Research ◽

Deuterium Excess ◽

Near Surface ◽

Source Temperature ◽

Moisture Source

Abstract. The deuterium excess (d) of precipitation is widely used in the reconstruction of past climatic changes from ice cores. However, its most common interpretation as moisture source temperature cannot directly be inferred from present-day water isotope observations. Here, we use a new empirical relation between d and near-surface relative humidity (RH) together with reanalysis data to globally predict d of surface evaporation from the ocean. The very good quantitative agreement of the predicted hemispherically averaged seasonal cycle with observed d in precipitation indicates that moisture source relative humidity, and not sea surface temperature, is the main driver of d variability on seasonal timescales. Furthermore, we review arguments for an interpretation of long-term palaeoclimatic d changes in terms of moisture source temperature, and we conclude that there remains no sufficient evidence that would justify to neglect the influence of RH on such palaeoclimatic d variations. Hence, we suggest that either the interpretation of d variations in palaeorecords should be adapted to reflect climatic influences on RH during evaporation, in particular atmospheric circulation changes, or new arguments for an interpretation in terms of moisture source temperature will have to be provided based on future research.

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-1399-2013 ◽

2013 ◽

Vol 13 (1) ◽

pp. 1399-1433 ◽

Cited By ~ 5

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.

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What controls deuterium excess in global precipitation?

Climate of the Past Discussions ◽

10.5194/cpd-9-4745-2013 ◽

2013 ◽

Vol 9 (4) ◽

pp. 4745-4770 ◽

Cited By ~ 7

Author(s):

S. Pfahl ◽

H. Sodemann

Keyword(s):

Relative Humidity ◽

Ice Core ◽

Empirical Relation ◽

Ice Cores ◽

Quantitative Agreement ◽

Convincing Evidence ◽

Deuterium Excess ◽

Near Surface ◽

Source Temperature ◽

Moisture Source

Abstract. The deuterium excess (d) of precipitation is widely used in the reconstruction of past climatic changes from ice cores. However, its most common interpretation as moisture source temperature cannot directly be inferred from present-day water isotope observations. Here, we use a new empirical relation between d and near-surface relative humidity together with reanalysis data to globally predict d of surface evaporation from the ocean. The very good quantitative agreement of the predicted hemispherically averaged seasonal cycle with observed d in precipitation indicates that moisture source relative humidity, and not sea surface temperature, is the main driver of d variability on seasonal time scales. There is no convincing evidence that RH might be less important for long-term palaeoclimatic d changes compared to moisture source temperature variations. Ice core d data may thus have to be reinterpreted, focusing on climatic influences on relative humidity during evaporation, in particular related to atmospheric circulation changes.

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High-resolution stable isotope signature of a land-falling atmospheric river in southern Norway

Weather and Climate Dynamics ◽

10.5194/wcd-2-713-2021 ◽

2021 ◽

Vol 2 (3) ◽

pp. 713-737

Author(s):

Yongbiao Weng ◽

Aina Johannessen ◽

Harald Sodemann

Keyword(s):

Surface Water ◽

High Resolution ◽

Water Vapour ◽

Isotope Composition ◽

Initial Period ◽

Cloud Microphysics ◽

Cloud Base ◽

Near Surface ◽

Surface Precipitation ◽

Moisture Source

Abstract. Heavy precipitation at the west coast of Norway is often connected to elongated meridional structures of high integrated water vapour transport known as atmospheric rivers (ARs). Here we present high-resolution measurements of stable isotopes in near-surface water vapour and precipitation during a land-falling AR in southwestern Norway on 7 December 2016. In our analysis, we aim to identify the influences of moisture source conditions, weather system characteristics, and post-condensation processes on the isotope signal in near-surface water vapour and precipitation. A total of 71 precipitation samples were collected during the 24 h sampling period, mostly taken at sampling intervals of 10–20 min. The isotope composition of near-surface vapour was continuously monitored in situ with a cavity ring-down spectrometer. Local meteorological conditions were in addition observed from a vertical pointing rain radar, a laser disdrometer, and automatic weather stations. We observe a stretched, “W”-shaped evolution of isotope composition during the event. Combining paired precipitation and vapour isotopes with meteorological observations, we define four different stages of the event. The two most depleted periods in the isotope δ values are associated with frontal transitions, namely a combination of two warm fronts that follow each other within a few hours and an upper-level cold front. The d-excess shows a single maximum and a step-wise decline in precipitation and a gradual decrease in near-surface vapour. Thereby, the isotopic evolution of the near-surface vapour closely follows that of the precipitation with a time delay of about 30 min, except for the first stage of the event. Analysis using an isotopic below-cloud exchange framework shows that the initial period of low and even negative d-excess in precipitation was caused by evaporation below cloud base. The isotope signal from the cloud level became apparent at ground level after a transition period that lasted up to several hours. Moisture source diagnostics for the periods when the cloud signal dominates show that the moisture source conditions are then partly reflected in surface precipitation and water vapour isotopes. In our study, the isotope signal in surface precipitation during the AR event reflects the combined influence of atmospheric dynamics, moisture sources, and atmospheric distillation, as well as cloud microphysics and below-cloud processes. Based on this finding, we recommend careful interpretation of results obtained from Rayleigh distillation models in such events, in particular for the interpretation of surface vapour and precipitation from stratiform clouds.

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An Analysis of the Processes Affecting Rapid Near-Surface Water Vapor Increases during the Afternoon to Evening Transition in Oklahoma

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-19-0062.1 ◽

2019 ◽

Vol 58 (10) ◽

pp. 2217-2234 ◽

Cited By ~ 1

Author(s):

W. G. Blumberg ◽

D. D. Turner ◽

S. M. Cavallo ◽

Jidong Gao ◽

J. Basara ◽

...

Keyword(s):

Water Vapor ◽

Surface Water ◽

Surface Cooling ◽

Near Surface ◽

Evening Transition ◽

Relative Contribution ◽

Oklahoma Mesonet ◽

Conditional Instability ◽

Water Vapor Mixing Ratio ◽

Spring Harvest

AbstractThis study used 20 years of Oklahoma Mesonet data to investigate the changes of near-surface water vapor mixing ratio qυ during the afternoon to evening transition (AET). Similar to past studies, increases in qυ are found to occur near sunset. However, the location, magnitude, and timing of the qυ maximum occurring during the AET are shown to be dependent on the seasonal growth and harvest of vegetation across Oklahoma in the spring and summer months. Particularly, the late spring harvest of winter wheat grown in Oklahoma appears to modify the relative contribution of local and nonlocal processes on qυ. By analyzing time series of qυ during the AET, it is found that the likelihood of a presunset qυ maximum is strongly dependent upon vegetation, soil moisture, wind speed, and cloud cover. Analysis also reveals that the increase in qυ during the AET can increase the parcel conditional instability despite the surface cooling produced by loss of insolation. Next to known changes in low-level wind shear, these changes in instability and moisture demonstrate new ways the AET can modify the presence of the key ingredients relevant to explaining the climatological increase in severe convective storm hazards around sunset.

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