scholarly journals Design and performance of a Nafion dryer for continuous operation at CO<sub>2</sub> and CH<sub>4</sub> air monitoring sites

2012 ◽  
Vol 5 (4) ◽  
pp. 5449-5468 ◽  
Author(s):  
L. R. Welp ◽  
R. F. Keeling ◽  
R. F. Weiss ◽  
W. Paplawsky ◽  
S. Heckman
Keyword(s):  
Water Vapor ◽  
Monitoring Network ◽  
Ambient Air ◽  
Drying Methods ◽  
Inlet System ◽  
Simple Method ◽  
Mixing Ratios ◽  
Peak Broadening ◽  
Order Of Magnitude ◽  
Water Vapor Mixing Ratio

Abstract. In preparation for the routine deployment of the Earth Networks greenhouse gas monitoring network, we have designed and tested a simple method for drying ambient air to below 0.2% mole fraction H2O using a Nafion dryer. The inlet was designed for use with a Picarro model G2301 cavity ring down spectrometer (CRDS) CO2/CH4/H2O analyzer. The analyzer measures water vapor mixing ratio at the same frequency as CO2 and CH4 and then corrects for the dilution and peak broadening effects of H2O on the CO2 and CH4 mixing ratios. This analyzer is remarkably stable and performs well on water vapor correction tests, but there is potentially an added benefit of reducing the dependence on the H2O correction for long term field measurement programs. Substantially lowering the amount of H2O in the sample can reduce uncertainties in the applied H2O corrections by an order of magnitude or more, and eliminate the need to determine an instrument-specific H2O correction factor and to verify its stability over time. Our Nafion drying inlet system takes advantage of the extra capacity of the analyzer pump to redirect 30% of the dry gas exiting the Nafion to the outer shell side of the dryer and has no consumables. We tested the Nafion dryer against a cryotrap (−95 °C) method for removing H2O and found that it does not significantly alter the CO2 and CH4 dry mixing ratios of the sample gas. Systematic differences between the drying methods were at the level of 0.05 ppm in CO2 and 0.1 ppb in CH4 for the wet-air tests, well within the WMO compatibility guidelines.

scholarly journals Design and performance of a Nafion dryer for continuous operation at CO<sub>2</sub> and CH<sub>4</sub> air monitoring sites

2013 ◽  
Vol 6 (5) ◽  
pp. 1217-1226 ◽  
Author(s):  
L. R. Welp ◽  
R. F. Keeling ◽  
R. F. Weiss ◽  
W. Paplawsky ◽  
S. Heckman
Keyword(s):  
Water Vapor ◽  
Ambient Air ◽  
Gas Mixing ◽  
Inlet System ◽  
Simple Method ◽  
Mixing Ratios ◽  
Peak Broadening ◽  
Order Of Magnitude ◽  
And Performance ◽  
The Impact

Abstract. In preparation for routine deployment in a network of greenhouse gas monitoring stations, we have designed and tested a simple method for drying ambient air to near or below 0.2% (2000 ppm) mole fraction H2O using a Nafion dryer. The inlet system was designed for use with cavity ring-down spectrometer (CRDS) analyzers such as the Picarro model G2301 that measure H2O in addition to their principal analytes, in this case CO2 and CH4. These analyzers report dry-gas mixing ratios without drying the sample by measuring H2O mixing ratio at the same frequency as the main analytes, and then correcting for the dilution and peak broadening effects of H2O on the mixing ratios of the other analytes measured in moist air. However, it is difficult to accurately validate the water vapor correction in the field. By substantially lowering the amount of H2O in the sample, uncertainties in the applied water vapor corrections can be reduced by an order of magnitude or more, thus eliminating the need to determine instrument-specific water vapor correction coefficients and to verify the stability over time. Our Nafion drying inlet system takes advantage of the extra capacity of the analyzer pump to redirect 30% of the dry gas exiting the Nafion to the outer shell side of the dryer and has no consumables. We tested the Nafion dryer against a cryotrap (−97 °C) method for removing H2O and found that in wet-air tests, the Nafion reduces the CO2 dry-gas mixing ratios of the sample gas by as much as 0.1 ± 0.01 ppm due to leakage across the membrane. The effect on CH4 was smaller and varied within ± 0.2 ppb, with an approximate uncertainty of 0.1 ppb. The Nafion-induced CO2 bias is partially offset by sending the dry reference gases through the Nafion dryer as well. The residual bias due to the impact of moisture differences between sample and reference gas on the permeation through the Nafion was approximately −0.05 ppm for CO2 and varied within ± 0.2 ppb for CH4. The uncertainty of this partial drying method is within the WMO compatibility guidelines for the Northern Hemisphere, 0.1 ppm for CO2 and 2 ppb for CH4, and is comparable to experimentally determining water vapor corrections for each instrument but less subject to concerns of possible drift in these corrections.

Humidity-Dependent Cold Cells on the Antenna of the Stick Insect

2007 ◽  
Vol 97 (6) ◽  
pp. 3851-3858 ◽  
Author(s):  
Harald Tichy
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Partial Pressure ◽  
Systematic Study ◽  
Water Vapor Pressure ◽  
Ambient Air ◽  
Stick Insect ◽  
Proper Choice ◽  
Impulse Frequency ◽  
Order Of Magnitude

We present the first systematic study of the response of insect “cold cells” to a variation in the partial pressure of water vapor in ambient air. The cold cells on the antenna of the stick insect respond with an increase in activity when either the temperature or the partial pressure of water vapor is suddenly reduced. This double dependency does not in itself constitute bimodality because it could disappear with the proper choice of parameters involving temperature and humidity. In this study, we demonstrate that the evaporation of a small amount of water from the sensillum surface resulting from a drop in the water vapor pressure—leading to a transient drop in temperature and thus to a brief rise in impulse frequency—is the most plausible explanation for this bimodal response. We also show with an order-of-magnitude calculation that this mechanism is plausible and consistent with the amounts of water vapor potentially present on the sensillum. We hypothesize that a film of moisture collects on the hygroscopic sensillum surface at higher humidity and then tends to evaporate when humidity is lowered. The water might even be bound loosely within the cuticular wall, a situation conceivable in a sensillum that contains two hygroreceptive cells in addition to the cold cell.

scholarly journals In situ measurements of water vapor, heat, and CO2 fluxes within a prescribed grass fire

2006 ◽  
Vol 15 (3) ◽  
pp. 299 ◽  
Author(s):  
Craig B. Clements ◽  
Brian E. Potter ◽  
Shiyuan Zhong
Keyword(s):  
Water Vapor ◽  
Dynamic Environment ◽  
Ambient Air ◽  
Lower Atmosphere ◽  
Fuel Load ◽  
Fire Plumes ◽  
Smoke Plumes ◽  
Water Vapor Mixing Ratio ◽  
Good Agreement

Fluxes of water vapor, heat, and carbon dioxide associated with a prescribed grass fire were documented quantitatively using a 43-m instrumented flux tower within the burn perimeter and a tethered balloon sounding system immediately downwind of the fire. The measurements revealed significant increases of temperature (up to 20°C), heat flux (greater than 1000 W m–2), and CO2 (larger than 2000 parts per million by volume) within the smoke plumes, as well as an intensification of turbulent mixing. Furthermore, the observations revealed an increase in water vapor mixing ratio of more than 2 g kg–1, or nearly 30% over the ambient air, which is in good agreement with theoretical estimates of the amount of water vapor release expected as a combustion by-product from a grass fire. These observations provide direct evidence that natural fuel-load grass-fire plumes may modify the dynamic environment of the lower atmosphere through not only heat release and intense mixing, but also large addition of water vapor.

scholarly journals Profiling water vapor mixing ratios in Finland by means of a Raman lidar, a satellite and a model

2017 ◽  
Vol 10 (11) ◽  
pp. 4303-4316 ◽  
Author(s):  
Maria Filioglou ◽  
Anna Nikandrova ◽  
Sami Niemelä ◽  
Holger Baars ◽  
Tero Mielonen ◽  
...  
Keyword(s):  
Water Vapor ◽  
Weather Prediction ◽  
Limited Area ◽  
Mixing Ratio ◽  
Atmospheric Conditions ◽  
Raman Lidar ◽  
Mixing Ratios ◽  
Seasonal Analysis ◽  
Relative Errors ◽  
Water Vapor Mixing Ratio

Abstract. We present tropospheric water vapor profiles measured with a Raman lidar during three field campaigns held in Finland. Co-located radio soundings are available throughout the period for the calibration of the lidar signals. We investigate the possibility of calibrating the lidar water vapor profiles in the absence of co-existing on-site soundings using water vapor profiles from the combined Advanced InfraRed Sounder (AIRS) and the Advanced Microwave Sounding Unit (AMSU) satellite product; the Aire Limitée Adaptation dynamique Développement INternational and High Resolution Limited Area Model (ALADIN/HIRLAM) numerical weather prediction (NWP) system, and the nearest radio sounding station located 100 km away from the lidar site (only for the permanent location of the lidar). The uncertainties of the calibration factor derived from the soundings, the satellite and the model data are  < 2.8, 7.4 and 3.9 %, respectively. We also include water vapor mixing ratio intercomparisons between the radio soundings and the various instruments/model for the period of the campaigns. A good agreement is observed for all comparisons with relative errors that do not exceed 50 % up to 8 km altitude in most cases. A 4-year seasonal analysis of vertical water vapor is also presented for the Kuopio site in Finland. During winter months, the air in Kuopio is dry (1.15±0.40 g kg−1); during summer it is wet (5.54±1.02 g kg−1); and at other times, the air is in an intermediate state. These are averaged values over the lowest 2 km in the atmosphere. Above that height a quick decrease in water vapor mixing ratios is observed, except during summer months where favorable atmospheric conditions enable higher mixing ratio values at higher altitudes. Lastly, the seasonal change in disagreement between the lidar and the model has been studied. The analysis showed that, on average, the model underestimates water vapor mixing ratios at high altitudes during spring and summer.

scholarly journals Analytical system for stable carbon isotope measurements of low molecular weight (C<sub>2</sub>-C<sub>6</sub>) hydrocarbons

2011 ◽  
Vol 4 (6) ◽  
pp. 1161-1175 ◽  
Author(s):  
A. Zuiderweg ◽  
R. Holzinger ◽  
T. Röckmann
Keyword(s):  
Carbon Isotope ◽  
Stable Carbon Isotope ◽  
Carbon Isotope Ratio ◽  
Ambient Air ◽  
Automated System ◽  
Stable Carbon ◽  
Inlet System ◽  
Air Samples ◽  
Amount Of Substance ◽  
Mixing Ratios

Abstract. We present setup, testing and initial results from a new automated system for stable carbon isotope ratio measurements on C2 to C6 atmospheric hydrocarbons. The inlet system allows analysis of trace gases from air samples ranging from a few liters for urban samples and samples with high mixing ratios, to many tens of liters for samples from remote unpolluted regions with very low mixing ratios. The centerpiece of the sample preparation is the separation trap, which is used to separate CO2 and methane from the compounds of interest. The main features of the system are (i) the capability to sample up to 300 l of air, (ii) long term (since May 2009) operational δ13C accuracy levels in the range 0.3–0.8 ‰ (1-σ), and (iii) detection limits of order 1.5–2.5 ngC (collected amount of substance) for all reported compounds. The first application of this system was the analysis of 21 ambient air samples taken during 48 h in August 2009 in Utrecht, the Netherlands. Results obtained are generally in good agreement with those from similar urban ambient air studies. Short sample intervals allowed by the design of the instrument help to illustrate the complex diurnal behavior of hydrocarbons in an urban environment, where diverse sources, dynamical processes, and chemical reactions are present.

scholarly journals The airborne mass spectrometer AIMS – Part 1: AIMS-H<sub>2</sub>O for UTLS water vapor measurements

2015 ◽  
Vol 8 (12) ◽  
pp. 13525-13565 ◽  
Author(s):  
S. Kaufmann ◽  
C. Voigt ◽  
T. Jurkat ◽  
T. Thornberry ◽  
D. W. Fahey ◽  
...  
Keyword(s):  
Water Vapor ◽  
Mass Spectrometer ◽  
Ambient Air ◽  
Reaction Scheme ◽  
Gas Discharge ◽  
Ion Source ◽  
Tunable Diode Laser ◽  
Cloud Formation ◽  
Calibration Source ◽  
Mixing Ratios

Abstract. In the upper troposphere and lower stratosphere (UTLS), the accurate quantification of low water vapor concentrations has presented a significant measurement challenge. The instrumental uncertainties are passed on to estimates of H2O transport, cloud formation and the H2O role in the UTLS energy budget and resulting effects on surface temperatures. To address the uncertainty in UTLS H2O determination, the airborne mass spectrometer AIMS-H2O, with in-flight calibration, has been developed for fast and accurate airborne water vapor measurements. We present the new setup to measure water vapor by direct ionization of ambient air. Air is sampled via a backward facing inlet that includes a bypass flow to assure short residence times (< 0.2 s) in the inlet line, which allows the instrument to achieve a time resolution of ∼ 4 Hz. From the main inlet flow, a smaller flow is extracted into the novel pressure-controlled gas discharge ion source of the mass spectrometer. The air is directed through the gas discharge region where water molecules react to form hydronium ion clusters, H3O+(H2O)n (n= 0, 1, 2), in a complex reaction scheme similar to the reactions in the D-region of the ionosphere. These ions are counted to quantify the ambient water vapor mixing ratio. The instrument is calibrated during flight using a new calibration source based on the catalytic reaction of H2 and O2 on a Pt surface to generate a calibration standard with well defined and stable H2O mixing ratios. In order to increase data quality over a range of mixing ratios, two data evaluation methods are presented for lower and higher H2O mixing ratios respectively, using either only the H3O+(H2O) ions or the ratio of all water vapor dependent ions to the total ion current. Altogether, a range of water vapor mixing ratios from 1 to 500 ppmv (mole ratio, 10−6 mol mol−1) can be covered with an accuracy between 7 and 15 %. AIMS-H2O was deployed on two DLR research aircraft, the Falcon during CONCERT (Contrail and Cirrus Experiment) in 2011, and HALO during ML-CIRRUS (Mid-Latitude Cirrus) in 2014. The comparison of AIMS-H2O with the SHARC tunable diode laser hygrometer during ML-CIRRUS shows a very good overall agreement between both instruments for the entire campaign.

Direct injection of water vapor into the lower stratosphere through extreme convection: A case study for the summer 2019 in the mid latitudes

2020 ◽  
Author(s):  
Dina Khordakova ◽  
Christian Rolf ◽  
Martina Krämer ◽  
Martin Riese
Keyword(s):  
Water Vapor ◽  
Satellite Images ◽  
Lower Stratosphere ◽  
Global Climate ◽  
Direct Injection ◽  
Reanalysis Data ◽  
Radiation Budget ◽  
Mixing Ratio ◽  
Mixing Ratios ◽  
Water Vapor Mixing Ratio

&lt;p&gt;Water vapor is one of the strongest greenhouse gases of the atmosphere. Its driving role in the upper troposphere / lower stratosphere region (UTLS) for the radiation budget was shown by e.g. Riese et al., (2012). Despite its low abundance of 4 - 6 ppmv in the stratosphere, even small changes in its mixing ratio can leed to a positive feedback to global warming. To better understand changes and variability of water vapor in the lower stratosphere, we focus here on exchange processes from the moist troposphere to the dry stratosphere in the mid latitudes. These processes are caused by extreme vertical convection, which is expected to increase in intensity and frequency with progressive global climate change.&lt;/p&gt;&lt;p&gt;Within the MOSES (Modular Observation Solutions for Earth Systems) campaign in the summer of 2019, two extreme vertical convection events could be captured with balloon borne humidity sensors over the eastern part of Germany. The comparison of measurements before and after both events reveal distinct water vapor enhancements in the lower stratosphere and show that even in mid-latitudes over shooting convection can impact the water vapor mixing ratio in the UTLS. The measurements are compared with the Microwave Limb Sounder (MLS) data as well as ECMWF reanalysis data.&lt;/p&gt;&lt;p&gt;&lt;span&gt;We will show a deeper analysis of both events by using visible and infrared weather satellite images in combination with meteorological fields of ECMWF. &lt;/span&gt;&lt;span&gt;B&lt;/span&gt;&lt;span&gt;ackward trajectories of the air masses &lt;/span&gt;&lt;span&gt;with the enriched water vapor mixing ratios &lt;/span&gt;&lt;span&gt;calculated with&lt;/span&gt;&lt;span&gt; the CLAMS model &lt;/span&gt;&lt;span&gt;and&lt;/span&gt; &lt;span&gt;combined&lt;/span&gt;&lt;span&gt; with the satellite images can &lt;/span&gt;&lt;span&gt;confirm the convective origin. &lt;/span&gt;&lt;span&gt;Additionally,&lt;/span&gt;&lt;span&gt; we show the &lt;/span&gt;&lt;span&gt;further &lt;/span&gt;&lt;span&gt;development of this distinct water vapor filaments within the lower stratosphere &lt;/span&gt;&lt;span&gt;in order to&lt;/span&gt;&lt;span&gt; trace the transport and mixing process, &lt;/span&gt;&lt;span&gt;based on an&lt;/span&gt; &lt;span&gt;analysis of forward trajectories.&lt;/span&gt;&lt;/p&gt;

scholarly journals The airborne mass spectrometer AIMS – Part 1: AIMS-H<sub>2</sub>O for UTLS water vapor measurements

2016 ◽  
Vol 9 (3) ◽  
pp. 939-953 ◽  
Author(s):  
Stefan Kaufmann ◽  
Christiane Voigt ◽  
Tina Jurkat ◽  
Troy Thornberry ◽  
David W. Fahey ◽  
...  
Keyword(s):  
Water Vapor ◽  
Mass Spectrometer ◽  
Ambient Air ◽  
Reaction Scheme ◽  
Gas Discharge ◽  
Ion Source ◽  
Tunable Diode Laser ◽  
Cloud Formation ◽  
Calibration Source ◽  
Mixing Ratios

Abstract. In the upper troposphere and lower stratosphere (UTLS), the accurate quantification of low water vapor concentrations has presented a significant measurement challenge. The instrumental uncertainties are passed on to estimates of H2O transport, cloud formation and the role of H2O in the UTLS energy budget and resulting effects on surface temperatures. To address the uncertainty in UTLS H2O determination, the airborne mass spectrometer AIMS-H2O, with in-flight calibration, has been developed for fast and accurate airborne water vapor measurements. We present a new setup to measure water vapor by direct ionization of ambient air. Air is sampled via a backward facing inlet that includes a bypass flow to assure short residence times (< 0.2 s) in the inlet line, which allows the instrument to achieve a time resolution of  ∼ 4 Hz, limited by the sampling frequency of the mass spectrometer. From the main inlet flow, a smaller flow is extracted into the novel pressure-controlled gas discharge ion source of the mass spectrometer. The air is directed through the gas discharge region where ion–molecule reactions lead to the production of hydronium ion clusters, H3O+(H2O)n (n = 0, 1, 2), in a complex reaction scheme similar to the reactions in the D-region of the ionosphere. These ions are counted to quantify the ambient water vapor mixing ratio. The instrument is calibrated during flight using a new calibration source based on the catalytic reaction of H2 and O2 on a Pt surface to generate a calibration standard with well-defined and stable H2O mixing ratios. In order to increase data quality over a range of mixing ratios, two data evaluation methods are presented for lower and higher H2O mixing ratios respectively, using either only the H3O+(H2O) ions or the ratio of all water vapor dependent ions to the total ion current. Altogether, a range of water vapor mixing ratios from 1 to 500 parts per million by volume (ppmv) can be covered with an accuracy between 7 and 15 %. AIMS-H2O was deployed on two DLR research aircraft, the Falcon during CONCERT (CONtrail and Cirrus ExpeRimenT) in 2011, and HALO during ML-CIRRUS (Mid-Latitude CIRRUS) in 2014. The comparison of AIMS-H2O with the SHARC tunable diode laser hygrometer during ML-CIRRUS shows a correlation near to 1 in the range between 10 and 500 ppmv for the entire campaign.

scholarly journals Measurements of the Total Water Content of Cirrus Clouds. Part I: Instrument Details and Calibration

2006 ◽  
Vol 23 (11) ◽  
pp. 1397-1409 ◽  
Author(s):  
E. M. Weinstock ◽  
J. B. Smith ◽  
D. Sayres ◽  
J. R. Spackman ◽  
J. V. Pittman ◽  
...  
Keyword(s):  
Water Vapor ◽  
Water Content ◽  
Solid Phase ◽  
Ambient Air ◽  
Cirrus Clouds ◽  
Specific Humidity ◽  
Total Water Content ◽  
Total Water ◽  
Measurement Capability ◽  
Mixing Ratios

Abstract This paper describes an instrument designed to measure the sum of gas phase and solid phase water, or total water, in cirrus clouds, and to be mounted in a pallet in the underbelly of the NASA WB-57 research aircraft. The ice water content of cirrus is determined by subtracting water vapor measured simultaneously by the Harvard water vapor instrument on the aircraft. The total water instrument uses an isokinetic inlet to maintain ambient particle concentrations as air enters the instrument duct, a 600-W heater mounted directly in the flow to evaporate the ice particles, and a Lyman-α photofragment fluorescence technique for detection of the total water content of the ambient air. Isokinetic flow is achieved with an actively controlled roots pump by referencing aircraft pressure, temperature, and true airspeed, together with instrument flow velocity, temperature, and pressure. Laboratory calibrations that utilize a water vapor addition system that adds air with a specific humidity tied to the vapor pressure of water at room temperature and crosschecked by axial and radial absorption of Lyman-α radiation at the detection axis are described in detail. The design provides for in-flight validation of the laboratory calibration by intercomparison with total water measured by radial absorption at the detection axis. Additionally, intercomparisons in clear air with the Harvard water vapor instrument are carried out. Based on performance of the Harvard water vapor instrument, this instrument has the detection capability of making accurate measurements of total water with mixing ratios in the mid- to upper troposphere of up to 2500 ppmv and mixing ratios in the lower stratosphere of about 5 ppmv, corresponding to almost three orders of magnitude in measurement capability.

scholarly journals Comparison of Raman Lidar Observations of Water Vapor with COSMO-DE Forecasts during COPS 2007

2011 ◽  
Vol 26 (6) ◽  
pp. 1056-1066 ◽  
Author(s):  
Christian Herold ◽  
Dietrich Althausen ◽  
Detlef Müller ◽  
Matthias Tesche ◽  
Patric Seifert ◽  
...  
Keyword(s):  
Water Vapor ◽  
Short Range ◽  
Residual Layer ◽  
Small Scale ◽  
Free Troposphere ◽  
Raman Lidar ◽  
Mixing Ratios ◽  
Performance Check ◽  
Water Vapor Mixing Ratio ◽  
Range Forecasts

Abstract Water vapor measurements with the multiwavelength Raman lidar Backscatter Extinction Lidar-Ratio Temperature Humidity Profiling Apparatus (BERTHA) were performed during the Convective and Orographically-induced Precipitation Study (COPS) in the Black Forest, Germany, from June to August 2007. For quality assurance, profiles of the water vapor mixing ratio measured with BERTHA are compared to simultaneous measurements of a radiosonde and an airborne differential absorption lidar (DIAL) on 31 July 2007. The differences from the radiosonde observations are found to be on average 1.5% and 2.5% in the residual layer and in the free troposphere, respectively. During the two overflights at 1937 and 2018 UTC, the differences from the DIAL results are −2.2% and −3.7% in the residual layer and 2.1% and −2.6% in the free troposphere. After this performance check, short-range forecasts from the German Meteorological Service’s (Deutscher Wetterdienst, DWD) version of the Consortium for Small-Scale Modeling (COSMO-DE) model are compared to the BERTHA measurements for two case studies. Generally, it is found that water vapor mixing ratios from short-range forecasts are on average 7.9% drier than the values measured in the residual layer. In the free troposphere, modeled values are 9.7% drier than the measurements.

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