Investigating the Source, Transport, and Isotope Composition of Water Vapour in the Planetary Boundary Layer

2016 ◽  
Author(s):  
Anonymous
Keyword(s):  
Boundary Layer ◽  
Water Vapour ◽  
Planetary Boundary Layer ◽  
Isotope Composition ◽  
Isotope Composition Of Water

scholarly journals Investigating the Source, Transport, and Isotope Composition of Water Vapor in the Planetary Boundary Layer

2016 ◽  
Author(s):  
T. J. Griffis ◽  
J. D. Wood ◽  
J. M. Baker ◽  
X. Lee ◽  
K. Xiao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Planetary Boundary Layer ◽  
Isotope Composition ◽  
Large Fraction ◽  
Terrestrial Ecosystems ◽  
Wavelet Coherence ◽  
Convective Precipitation ◽  
Isotope Composition Of Water ◽  
Tall Tower

Abstract. Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understanding feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor from a very tall tower (185 m) in the Upper Midwest, United States to help diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotope observations for the region. Models and cross wavelet analyses were used to assess the importance of Rayleigh, evapotranspiration (ET), and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a very large seasonal amplitude (mean monthly δ18Ov ranged from −40.1 to −15.5 ‰ and δ2Hv ranged from −278.7 to −109.1 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio at the annual time-scale. However, this relation was strongly modulated by ET and PBL entrainment processes at time-scales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dx) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that ET often leads changes in dx, confirming that it is a potential tracer of regional ET. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional ET. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratios events (> 25 mmol mol−1) indicate that regional ET can account for 40 % to 60 % of the PBL water vapor. These estimates are in relatively good agreement with that derived from numerical weather model simulations. This relatively large fraction of ET-derived water vapor implies that ET has an important impact on the precipitation recycling ratio within the region. Based on multiple constraints, we estimate that the summer season recycling fraction is about 30 %, indicating a potentially important link with convective precipitation.

scholarly journals Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

2016 ◽  
Vol 16 (8) ◽  
pp. 5139-5157 ◽  
Author(s):  
Timothy J. Griffis ◽  
Jeffrey D. Wood ◽  
John M. Baker ◽  
Xuhui Lee ◽  
Ke Xiao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Planetary Boundary Layer ◽  
Isotope Composition ◽  
Convective Precipitation ◽  
Mixing Ratio ◽  
Rayleigh Distillation ◽  
Water Vapor Mixing Ratio ◽  
Isotope Composition Of Water ◽  
Tall Tower

Abstract. Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotope observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ18Ov ranged from −40.2 to −15.9 ‰ and δ2Hv ranged from −278.7 to −113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dv) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in dv, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( >  25 mmol mol−1) indicate that regional evaporation can account for 40 to 60 % of the PBL water vapor. These estimates are in relatively good agreement with that derived from numerical weather model simulations. This relatively large fraction of evaporation-derived water vapor implies that evaporation has an important impact on the precipitation recycling ratio within the region. Based on multiple constraints, we estimate that the summer season recycling fraction is about 30 %, indicating a potentially important link with convective precipitation.

Characterization of the time evolution of the PBL structure and dry-layers based on the us of Raman Lidar measurements collected during HYMEX-SOP1

2021 ◽  
Author(s):  
Donato Summa ◽  
Paolo Di Girolamo ◽  
Noemi Franco ◽  
Benedetto De Rosa ◽  
Fabio Madonna ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Boundary Layer ◽  
Water Vapour ◽  
Planetary Boundary Layer ◽  
Grid Point ◽  
Laser Source ◽  
Raman Lidar ◽  
Water Vapour Concentration ◽  
Vapour Concentration

<p>The exchange processes between the Earth and the atmosphere play a crucial role in the development of the Planetary Boundary Layer (PBL). Different remote sensing techniques can provide PBL measurement with different spatial and temporal resolutions. Vertical profiles of atmospheric thermodynamic variables, i.e.  temperature and humidity, or wind speed, clouds and aerosols can be used as proxy to retrieve PBL height from active and passive remote sensing instruments. The University of BASILicata ground-based Raman Lidar system (BASIL) was deployed in the North-Western Mediterranean basin in the Cévennes-Vivarais site (Candillargues, Southern France, Lat: 43°37' N, Long: 4° 4' E, Elev: 1 m) and operated between 5 September and 5 November 2012, collecting more than 600 hours of measurements, distributed over 51 days and 19 intensive observation periods (IOPs). BASIL is capable to provide high-resolution and accurate measurements of atmospheric temperature and water vapour, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. This measurement capability makes BASIL a key instrument for the characterization of the water vapour concentration. BASIL makes use of a Nd:YAG laser source capable of emitting pulses at 355, 532 and 1064 nm, with a single pulse energy at 355nm of 500 mJ [1] .In the presented research effort, water vapour concentration was  computed and used to determine the PBL height. [2]. A dynamic index  included in the European Centre for Medium-range Weather Forecasts (ECMWF) ERA5 atmospheric reanalysis (CAPE, Friction velocity, etc.) is also considered and compared with BASIL resutls. ERA5 provides hourly data on regular latitude-longitude grids at 0.25° x 0.25° resolution at 37 pressure levels [3]. ERA5 is publicly available through the Copernicus Climate Data Store (CDS, https://cds.climate.copernicus.eu).  In order to properly carry out the comparison, the nearest ERA5 grid point to the lidar site has been considered assuming the representativeness uncertainty due to the use of the nearest grid-point comparable with other methods (e.g. kriging, bilinear interpolation, etc.). More results from this  measurement  effort will  be reported and discussed at the Conference.</p><p><strong>Reference</strong></p><p>[1] Di Girolamo, Paolo, De Rosa, Benedetto, Flamant, Cyrille, Summa, Donato, Bousquet, Olivier, Chazette, Patrick, Totems, Julien, Cacciani, Marco. Water vapor mixing ratio and temperature inter-comparison results in the framework of the Hydrological Cycle in the Mediterranean Experiment—Special Observation Period 1. BULLETIN OF ATMOSPHERIC SCIENCE AND TECHNOLOGY, ISSN: 2662-1495, doi: 10.1007/s42865-020-00008-3</p><p>[2] D. Summa, P. Di Girolamo, D. Stelitano, and M. Cacciani. Characterization of the planetary boundary layer height and structure by Raman lidar: comparison of different approaches  Atmos. Meas. Tech., 6, 3515–3525, 2013 www.atmos-meas-tech.net/6/3515/2013/doi:10.5194/amt-6-3515-2013</p><p>[3] Hersbach et al. The ERA5 global reanalysis Hans  https://doi.org/10.1002/qj.3803[3]</p>

scholarly journals The stable isotope composition of water vapour above Corsica during the HyMeX SOP1: insight into vertical mixing processes from lower-tropospheric survey flights

2016 ◽  
Author(s):  
Harald Sodemann ◽  
Franziska Aemisegger ◽  
Stephan Pfahl ◽  
Mark Bitter ◽  
Ulrich Corsmeier ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Stable Isotope ◽  
Water Vapour ◽  
Isotope Composition ◽  
Water Isotopes ◽  
High Temporal Resolution ◽  
Stable Isotope Composition ◽  
Stable Water Isotopes ◽  
Mixing Processes ◽  
Strong Inversion

Abstract. Stable water isotopes are powerful indicators of meteorological processes on a broad range of scales, reflecting evaporation, condensation, and airmass mixing processes. With the recent advent of fast laser-based spectroscopic methods it has become possible to measure the stable isotopic composition of atmospheric water vapour in situ at high temporal resolution, enabling to tremendously extend the measurement data base in space and time. Here we present the first set of airborne spectroscopic stable water isotopes measurements over the western Mediterranean. Measurements have been acquired by a customised Picarro L2130-i cavity-ring down spectrometer deployed onboard of the Dornier 128 D-IBUF aircraft together with a meteorological flux measurement package during the HyMeX SOP1 field campaign in Corsica, France during September and October 2012. Taking into account memory effects of the air inlet pipe, the typical time resolution of the measurements was about 15–30 s, resulting in an average horizontal resolution of about 1–2 km. Cross-calibration of the water vapour measurements from all humidity sensors showed good agreement in most flight conditions but the most turbulent ones. In total 21 successful stable isotope flights with 59 flight hours have been performed. Our data provide quasi-climatological autumn average conditions of the stable isotope parameters δD, δ18O and d-excess during the study period. A time-averaged perspective of the vertical stable isotope composition reveals for the first time the mean vertical structure of stable water isotopes over the Mediterranean at high resolution. A d-excess minimum in the overall average profile is reached in the region of the boundary layer top due to precipitation evaporation, bracketed by higher d-excess values near the surface due to non-equilibrium fractionation and above the boundary layer due to the non-linearity of the d-excess definition. Repeated flights along the same pattern reveals pronounced day-to-day variability due to changes in the large-scale circulation. During a period marked by a strong inversion at the top of the marine boundary layer, vertical gradients in stable isotopes reached up to 25.4 ‰ 100 m−1 for δD.

scholarly journals Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers

2020 ◽  
Vol 13 (6) ◽  
pp. 3167-3190
Author(s):  
Yongbiao Weng ◽  
Alexandra Touzeau ◽  
Harald Sodemann
Keyword(s):  
Water Vapour ◽  
Isotope Composition ◽  
Data Interpretation ◽  
Polar Regions ◽  
Mixing Ratio ◽  
Mixing Ratios ◽  
Δ18o And Δd ◽  
Isotope Composition Of Water ◽  
The Impact ◽  
Cavity Ring Down

Abstract. Recent advances in laser spectroscopy enable high-frequency in situ measurements of the isotope composition of water vapour. At low water vapour mixing ratios, however, the measured stable water isotope composition can be substantially affected by a measurement artefact known as the mixing ratio dependency, which is commonly considered independent of the isotope composition. Here we systematically investigate how the mixing ratio dependency, in a range from 500 to 23 000 ppmv of three commercial cavity ring-down spectrometers, is affected by the isotope composition of water vapour. We find that the isotope composition of water vapour has a substantial and systematic impact on the mixing ratio dependency for all three analysers, particularly at mixing ratios below 4000 ppmv. This isotope composition dependency can create a deviation of ±0.5 ‰ and ±6.0 ‰ for δ18O and δD, respectively, at ∼2000 ppmv, resulting in about 2 ‰–3 ‰ deviation for the d-excess. An assessment of the robustness of our findings shows that the overall behaviour is reproducible over up to 2 years for different dry gas supplies, while being independent of the method for generating the water vapour and being the first order of the evaluation sequence. We propose replacing the univariate mixing ratio dependency corrections with a new, combined isotope composition–mixing ratio dependency correction. Using aircraft- and ship-based measurements in an Arctic environment, we illustrate a relevant application of the correction. Based on our findings, we suggest that the dependency on the isotope composition may be primarily related to spectroscopy. Repeatedly characterising the combined isotope composition–mixing ratio dependency of laser spectrometers when performing water vapour measurements at high elevations, on aircraft, or in polar regions appears critical to enable reliable data interpretation in dry environments.

scholarly journals Observing Water Vapour in the Planetary Boundary Layer from the Short-Wave Infrared

2018 ◽  
Vol 10 (9) ◽  
pp. 1469 ◽  
Author(s):  
Tim Trent ◽  
Hartmut Boesch ◽  
Peter Somkuti ◽  
Noëlle Scott
Keyword(s):  
Boundary Layer ◽  
Water Vapour ◽  
Planetary Boundary Layer ◽  
Short Wave ◽  
Electromagnetic Spectrum ◽  
Climate Data ◽  
Data Set ◽  
Near Surface ◽  
Land Surfaces ◽  
Shortwave Infrared

Water vapour is a key greenhouse gas in the Earth climate system. In this golden age of satellite remote sensing, global observations of water vapour fields are made from numerous instruments measuring in the ultraviolet/visible, through the infrared bands, to the microwave regions of the electromagnetic spectrum. While these observations provide a wealth of information on columnar, free-tropospheric and upper troposphere/lower stratosphere water vapour amounts, there is still an observational gap regarding resolved bulk planetary boundary layer (PBL) concentrations. In this study we demonstrate the ability of the Greenhouse Gases Observing SATellite (GOSAT) to bridge this gap from highly resolved measurements in the shortwave infrared (SWIR). These new measurements of near surface columnar water vapour are free of topographic artefacts and are interpreted as a proxy for bulk PBL water vapour. Validation (over land surfaces only) of this new data set against global radiosondes show low biases that vary seasonally between −2% to 5%. Analysis on broad latitudinal bands show biases between −3% and 2% moving from high latitudes to the equatorial regions. Finally, with the extension of the GOSAT program out to at least 2027, we discuss the potential for a new GOSAT PBL water vapour Climate Data Record (CDR).

Airborne water vapor isotope measurements over the Iceland Sea in winter conditions

2021 ◽  
Author(s):  
Alexandra Touzeau ◽  
Hans-Christian Steen-Larsen ◽  
Ian Renfrew ◽  
Þorsteinn Jónsson ◽  
Andrew Elvidge ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Stable Isotope ◽  
Sea Ice ◽  
Water Vapour ◽  
Cloud Cover ◽  
Isotope Composition ◽  
Specific Humidity ◽  
Free Troposphere ◽  
Cold Air ◽  
Isotope Measurements

<p>Improved understanding of evaporation and condensation processes is critical to improve the representation of the water cycle in atmospheric models. Thereby, in-situ measurements along the entire moisture transport pathway, covering evaporation, mixing between different air masses in the atmospheric boundary layer and the free troposphere, and resulting precipitation are highly valuable to obtain new insight. In particular, coherent measurements of the stable isotope composition in atmospheric vapour can provide additional constraints on phase change processes of water vapour from source to sink, enabling direct comparison within isotope-enabled models.</p><p>Here we present stable isotope measurements from the Iceland Greenland Seas Project field campaign that took place in February-March 2018. This unique dataset includes simultaneous measurements from a land-station in Husavik, Iceland, a ship and an air plane in the subpolar region. Alternation between cold-air outbreaks and mid-latitude airmasses characterized the measurement period. Here we focus on the stable water isotope composition in water vapour obtained from 10 research flights, covering a large geographic range (64 °N to 72 °N). Careful data treatment was applied to ensure the quality of isotope measurements in the predominant cold, dry conditions with large gradients in isotope composition and humidity.</p><p>From an intercomparison flight over the Husavik station, we find good agreement between ground and airborne measurements. Out of 7 flights dedicated to the study of atmosphere-ocean-ice interactions, with both low-levels legs and vertical sections in predominant Cold Air Outbreak (CAO) conditions, we focus on the marginal ice zone and regions covered by shallow cumulus clouds. For open water flights, we find the horizontal and vertical distribution of δ<sup>18</sup>O in the marine boundary layer to covary with cloud cover. Thereby, downdrafts bring dry and <sup>18</sup>O-depleted air from the free troposphere towards the surface, corresponding to openings in cloud cover. For flights passing over sea ice edge, both δ<sup>18</sup>O and specific humidity show a clear east-west gradient, with increasing values towards the open sea reflecting ocean moisture availability. Additionally, open leads in the sea ice also have a visible impact on isotope values. Lastly, relatively low d-excess values are observed over the sea-ice, which could either be caused by local processes or advection.</p>

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