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Sample records for atmospheric water vapour

  1. Remote Sensing of Atmospheric Water Vapour by Pressure Modulation Radiometry.

    NASA Astrophysics Data System (ADS)

    Davis, G. R.

    1987-09-01

    Available from UMI in association with The British Library. Requires signed TDF. The Stratospheric and Mesospheric Sounder (SAMS) was a limb-sounding satellite experiment which used the technique of pressure modulation radiometry to measure the temperature and constituent distributions in the middle atmosphere. Two channels in the SAMS were devoted to the detection of water vapour, but the analysis of these data have produced unexpectedly high mixing ratios in the region of the stratopause. This thesis describes an attempt to resolve the discrepancy between theory and experiment by a laboratory investigation of the pressure modulation of water vapour. The central role of water vapour in the physics and chemistry of the middle atmosphere and previous attempts to measure its abundance are discussed. It is shown that the intercomparison of humidity sensing instruments has not produced a consensus and that the accuracy of the reported measurements is therefore in question. The SAMS water vapour channels are described and the need is shown for a laboratory transmission experiment. The pressure modulation technique is described in chapter 2 and a mathematical formulation is given. The constraints due to contaminant signals and harmonic contributions are considered and the use of the square wave chopping approximation in the interpretation of the measurements is discussed. In chapter 3, the spectroscopy of the H _2O rotation band is considered and it is shown that there are large uncertainties in most aspects of the problem due to the lack of spectroscopic measurements in this spectral region. In particular, the shapes of the collision broadened line wings under both self and foreign broadened conditions are poorly determined, a situation which is especially problematic for pressure modulation radiometry. The pressure modulation of water vapour is investigated in chapter 4 and it is shown by direct measurement of the pressure cycle that the linear model used by previous

  2. Modelling the budget of middle atmospheric water vapour isotopes

    NASA Astrophysics Data System (ADS)

    Zahn, A.; Franz, P.; Bechtel, C.; Groo, J.-U.; Rckmann, T.

    2006-06-01

    A one-dimensional chemistry model is applied to study the stable hydrogen (D) and stable oxygen isotope (17O, 18O) composition of water vapour in stratosphere and mesosphere. In the troposphere, this isotope composition is determined by "physical'' fractionation effects, that are phase changes (e.g. during cloud formation), diffusion processes (e.g. during evaporation from the ocean), and mixing of air masses. Due to these processes water vapour entering the stratosphere first shows isotope depletions in D/H relative to ocean water, which are ~5 times of those in 18O/16O, and secondly is mass-dependently fractionated (MDF), i.e. changes in the isotope ratio 17O/16O are ~0.52 times of those of 18O/16O. In contrast, in the stratosphere and mesosphere "chemical'' fractionation mechanisms, that are the production of HO due to the oxidation of methane, re-cycling of H2O via the HOx family, and isotope exchange reactions considerably enhance the isotope ratios in the water vapour imported from the troposphere. The model reasonably predicts overall enhancements of the stable isotope ratios in H2O by up to ~25% for D/H, ~8.5% for 17O/16O, and ~14% for 18O/16O in the mesosphere relative to the tropopause values. The 17O/16O and 18O/16O ratios in H2O are shown to be a measure of the relative fractions of HOx that receive the O atom either from the reservoirs O2 or O3. Throughout the middle atmosphere, MDF O2 is the major donator of oxygen atoms incorporated in OH and HO2 and thus in H2O. In the stratosphere the known mass-independent fractionation (MIF) signal in O3 is in a first step transferred to the NOx family and only in a second step to HOx and H2O. In contrast to CO2, O(1D) only plays a minor role in this MIF transfer. The major uncertainty in our calculation arises from poorly quantified isotope exchange reaction rate coefficients and kinetic isotope fractionation factors.

  3. Atmospheric water vapour and cloud water: an overview

    NASA Astrophysics Data System (ADS)

    Ruprecht, E.

    Hydro-meteorological parameters i.e. precipitable water, cloud water and ice content, and precipitation are most variable parameters in the atmosphere. This is the main reason why representative direct measurements of these properties are hardly available. Remote sensing with satellite-borne instruments in particular in the microwave spectral range is a way out of this dilemma. A number of algorithms has been developed. The different methods how to proceed in the development of such algorithms are discussed. Verification of the retrieved products in particular the liquid water path is a great problem, a few ideas will be discussed. Results will be shown for the total precipitable water W and liquid water path LWP over the Atlantic Ocean for different time scales. The structure of the W field is very similar for the same month in different years. But LWP is very variable, even for monthly means (October 1987 and 1989) the differences can be larger than 0.1 kg/m^2.

  4. Canopy-scale kinetic fractionation of atmospheric carbon dioxide and water vapour isotopes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The isotopic fluxes of carbon dioxide (CO2) and water vapour (H2O) between the atmosphere and terrestrial plants provide powerful constraints on carbon sequestration on land 1-2, changes in vegetation cover 3 and the Earth’s Dole effect 4. Past studies, relying mainly on leaf-scale observations, hav...

  5. The isotope composition of water vapour: A powerful tool to study transport and chemistry of middle atmospheric water vapour

    NASA Astrophysics Data System (ADS)

    Bechtel, Ch.; Zahn, A.

    2003-07-01

    A one-dimensional chemistry model is applied to study the stable hydrogen (D) and stable oxygen isotope (17O, 18O) composition of water vapour in stratosphere and mesosphere. The stable isotope ratios of tropospheric H2O are determined by "physical'' fractionation effects, i.e. phase changes, diffusion processes, and mixing of air masses. Due to these processes water vapour entering the stratosphere (i) is mass-dependently fractionated (MDF), i.e. shifts in the isotope ratio 17O/16O are ~0.52 times of those of 18O/16O and (ii) shows isotope shifts in D/H, which are ~5 times of those in 18O/16O. In stratosphere and mesosphere "chemical'' fractionation, that are the oxidation of methane, re-cycling of H2O via the HOx family, and isotope exchange reactions are shown to considerably enhance the isotope ratios in the imported tropospheric H2O. Enrichments relative to the isotope ratios at the tropopause are used to derive the partitioning of tropospheric (unmodified), re-cycled and in situ generated H2O. The model reasonably predicts overall increases of the stable isotope ratios in H2O by ~23% for D/H, ~8.5% for 17O/16O, and ~14% for 18O/16O. The17O/16O and 18O/16O ratios in H2O are shown to be a measure of the partitioning of HOx that receives its O atom either from the reservoirs O2 or O3. In the entire middle atmosphere, MDF O2 is the major donator of oxygen atoms incorporated in OH and HO2 and thus in H2O. It is demonstrated that in the stratosphere mass-independent fractionation (MIF) in O3 in a first step is transferred to the NOx family and only in a second step to HOx and H2O. In contrast to CO2, O(1D) only plays a minor role in this MIF transfer. The major uncertainty in our calculation arises from the many badly quantified isotope exchange reactions and kinetic isotope fractionation factors.

  6. Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanet.

    PubMed

    Fraine, Jonathan; Deming, Drake; Benneke, Bjorn; Knutson, Heather; Jordán, Andrés; Espinoza, Néstor; Madhusudhan, Nikku; Wilkins, Ashlee; Todorov, Kamen

    2014-09-25

    Transmission spectroscopy has so far detected atomic and molecular absorption in Jupiter-sized exoplanets, but intense efforts to measure molecular absorption in the atmospheres of smaller (Neptune-sized) planets during transits have revealed only featureless spectra. From this it was concluded that the majority of small, warm planets evolve to sustain atmospheres with high mean molecular weights (little hydrogen), opaque clouds or scattering hazes, reducing our ability to observe the composition of these atmospheres. Here we report observations of the transmission spectrum of the exoplanet HAT-P-11b (which has a radius about four times that of Earth) from the optical wavelength range to the infrared. We detected water vapour absorption at a wavelength of 1.4 micrometres. The amplitude of the water absorption (approximately 250 parts per million) indicates that the planetary atmosphere is predominantly clear down to an altitude corresponding to about 1 millibar, and sufficiently rich in hydrogen to have a large scale height (over which the atmospheric pressure varies by a factor of e). The spectrum is indicative of a planetary atmosphere in which the abundance of heavy elements is no greater than about 700 times the solar value. This is in good agreement with the core-accretion theory of planet formation, in which a gas giant planet acquires its atmosphere by accreting hydrogen-rich gas directly from the protoplanetary nebula onto a large rocky or icy core. PMID:25254473

  7. Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanet

    NASA Astrophysics Data System (ADS)

    Fraine, Jonathan; Deming, Drake; Benneke, Bjorn; Knutson, Heather; Jordán, Andrés; Espinoza, Néstor; Madhusudhan, Nikku; Wilkins, Ashlee; Todorov, Kamen

    2014-09-01

    Transmission spectroscopy has so far detected atomic and molecular absorption in Jupiter-sized exoplanets, but intense efforts to measure molecular absorption in the atmospheres of smaller (Neptune-sized) planets during transits have revealed only featureless spectra. From this it was concluded that the majority of small, warm planets evolve to sustain atmospheres with high mean molecular weights (little hydrogen), opaque clouds or scattering hazes, reducing our ability to observe the composition of these atmospheres. Here we report observations of the transmission spectrum of the exoplanet HAT-P-11b (which has a radius about four times that of Earth) from the optical wavelength range to the infrared. We detected water vapour absorption at a wavelength of 1.4 micrometres. The amplitude of the water absorption (approximately 250 parts per million) indicates that the planetary atmosphere is predominantly clear down to an altitude corresponding to about 1 millibar, and sufficiently rich in hydrogen to have a large scale height (over which the atmospheric pressure varies by a factor of e). The spectrum is indicative of a planetary atmosphere in which the abundance of heavy elements is no greater than about 700 times the solar value. This is in good agreement with the core-accretion theory of planet formation, in which a gas giant planet acquires its atmosphere by accreting hydrogen-rich gas directly from the protoplanetary nebula onto a large rocky or icy core.

  8. The uncertainty of the atmospheric integrated water vapour estimated from GNSS observations

    NASA Astrophysics Data System (ADS)

    Ning, T.; Wang, J.; Elgered, G.; Dick, G.; Wickert, J.; Bradke, M.; Sommer, M.; Querel, R.; Smale, D.

    2016-01-01

    Within the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) there is a need for an assessment of the uncertainty in the integrated water vapour (IWV) in the atmosphere estimated from ground-based global navigation satellite system (GNSS) observations. All relevant error sources in GNSS-derived IWV are therefore essential to be investigated. We present two approaches, a statistical and a theoretical analysis, for the assessment of the uncertainty of the IWV. The method is valuable for all applications of GNSS IWV data in atmospheric research and weather forecast. It will be implemented to the GNSS IWV data stream for GRUAN in order to assign a specific uncertainty to each data point. In addition, specific recommendations are made to GRUAN on hardware, software, and data processing practices to minimise the IWV uncertainty. By combining the uncertainties associated with the input variables in the estimations of the IWV, we calculated the IWV uncertainties for several GRUAN sites with different weather conditions. The results show a similar relative importance of all uncertainty contributions where the uncertainties in the zenith total delay (ZTD) dominate the error budget of the IWV, contributing over 75 % of the total IWV uncertainty. The impact of the uncertainty associated with the conversion factor between the IWV and the zenith wet delay (ZWD) is proportional to the amount of water vapour and increases slightly for moist weather conditions. The GRUAN GNSS IWV uncertainty data will provide a quantified confidence to be used for the validation of other measurement techniques.

  9. Rotationally resolved water dimer spectra in atmospheric air and pure water vapour in the 188-258 GHz range.

    PubMed

    Serov, E A; Koshelev, M A; Odintsova, T A; Parshin, V V; Tretyakov, M Yu

    2014-12-21

    New experimental results regarding "warm" water dimer spectra under equilibrium conditions are presented. An almost equidistant series of six peaks corresponding to the merged individual lines of the bound dimer with consecutive rotational quantum numbers is studied in the 188-258 GHz frequency range in water vapour over a broad range of pressures and temperatures relevant to the Earth's atmosphere. The series is a continuation of the sequence detected earlier at lower frequencies at room temperature. The signal-to-noise ratio of the observed spectra allowed investigating their evolution, when water vapour was diluted by atmospheric air with partial pressure from 0 up to 540 Torr. Analysis of the obtained spectra permitted determining the dimerization constant as well as the hydrogen bond dissociation energy and the dimer spectral parameters, including the average coefficient of collisional broadening of individual lines by water vapour and air. The manifestation of metastable states of the dimer in the observed spectra is assessed. The contribution of three possible pair states of water molecules to the second virial coefficient is evaluated over the broad range of temperatures. The work supports the significant role of the water dimer in atmospheric absorption and related processes. PMID:25363156

  10. The uncertainty of the atmospheric integrated water vapour estimated from GNSS observations

    NASA Astrophysics Data System (ADS)

    Ning, T.; Wang, J.; Elgered, G.; Dick, G.; Wickert, J.; Bradke, M.; Sommer, M.

    2015-08-01

    Within the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) there is a need for an assessment of the uncertainty in the Integrated Water Vapour (IWV) in the atmosphere estimated from ground-based GNSS observations. All relevant error sources in GNSS-derived IWV is therefore essential to be investigated. We present two approaches, a statistical and a theoretical analysis, for the assessment of the uncertainty of the IWV. It will be implemented to the GNSS IWV data stream for GRUAN in order to obtain a specific uncertainty for each data point. In addition, specific recommendations are made to GRUAN on hardware, software, and data processing practices to minimize the IWV uncertainty. By combining the uncertainties associated with the input variables in the estimations of the IWV, we calculated the IWV uncertainties for several GRUAN sites with different weather conditions. The results show a similar relative importance of all uncertainty contributions where the uncertainties in the Zenith Total Delay (ZTD) dominate the error budget of the IWV contributing with over 75 % to the total IWV uncertainty. The impact of the uncertainty associated with the conversion factor between the IWV and the Zenith Wet Delay (ZWD) is proportional to the amount of water vapour and increases slightly for moist weather conditions. The GRUAN GNSS IWV uncertainty data will provide a quantified confidence to be used for the validation of other measurement techniques, taking the uncertainty into account from diurnal to decadal time scales.

  11. A rapid method for the sampling of atmospheric water vapour for isotopic analysis.

    PubMed

    Peters, Leon I; Yakir, Dan

    2010-01-01

    Analysis of the stable isotopic composition of atmospheric moisture is widely applied in the environmental sciences. Traditional methods for obtaining isotopic compositional data from ambient moisture have required complicated sampling procedures, expensive and sophisticated distillation lines, hazardous consumables, and lengthy treatments prior to analysis. Newer laser-based techniques are expensive and usually not suitable for large-scale field campaigns, especially in cases where access to mains power is not feasible or high spatial coverage is required. Here we outline the construction and usage of a novel vapour-sampling system based on a battery-operated Stirling cycle cooler, which is simple to operate, does not require any consumables, or post-collection distillation, and is light-weight and highly portable. We demonstrate the ability of this system to reproduce delta(18)O isotopic compositions of ambient water vapour, with samples taken simultaneously by a traditional cryogenic collection technique. Samples were collected over 1 h directly into autosampler vials and were analysed by mass spectrometry after pyrolysis of 1 microL aliquots to CO. This yielded an average error of < +/-0.5 per thousand, approximately equal to the signal-to-noise ratio of traditional approaches. This new system provides a rapid and reliable alternative to conventional cryogenic techniques, particularly in cases requiring high sample throughput or where access to distillation lines, slurry maintenance or mains power is not feasible. PMID:19960497

  12. NRT Atmospheric Water Vapour Retrieval on the Area of Poland at IGG WUELS AC

    NASA Astrophysics Data System (ADS)

    Kaplon, Jan; Bosy, Jaroslaw; Sierny, Jan; Hadas, Tomasz; Rohm, Witold; Wilgan, Karina; Ryczywolski, Marcin; Oruba, Artur; Kroszczynski, Krzysztof

    2013-04-01

    Global Navigation Satellite Systems (GNSS) are designed for positioning, navigation and amongst other possible applications it can also be used to derive information about the state of the atmosphere. Continuous observations from GNSS receivers provide an excellent tool for studying the neutral atmosphere, currently in near real-time. The Near Real-Time (NRT) neutral atmosphere and water vapour distribution models are currently obtained with high resolution from Ground Base Augmentation Systems (GBAS), where reference stations are equipped with GNSS and meteorological sensors. The Poland territory is covered by dense network of GNSS stations in the frame of GBAS system called ASG-EUPOS (www.asgeupos.pl). This system was established in year 2008 by the Head Office of Geodesy and Cartography in the frame of the EUPOS project (www.eupos.org) for providing positioning services. The GNSS data are available from 130 reference stations located in Poland and neighbour countries. The ground meteorological observations in the area of Poland and neighbour countries are available from ASG-EUPOS stations included in EUREF Permanent Network (EPN) stations, airports meteorological stations (METAR messages stations), and stations managed by national Institute of Meteorology and Water Management (SYNOP messages stations). Institute of Geodesy and Geoinformatics (IGG) of Wroclaw University of Environmental and Life Sciences had created permanent NRT service of ZTD (Zenith Total Delay) estimation for the area of Poland from GPS observations called IGGHZG. The first part of the paper presents the methodology of NRT GNSS data processing for ASG-EUPOS stations for ZTD estimation and its comparison to the results coming from EPN ACs and Military University of Technology in Warsaw AC (MUT AC). Second part covers the procedure of IWV (atmospheric Integrated Water Vapour content) estimation at IGG from IGGHZG product and ZHD (Zenith Hydrostatic Delay) derived from Saastamoinen formula (1972

  13. The summer 2012 Greenland heat wave: monitoring water vapour isotopic composition along an atmospheric river event

    NASA Astrophysics Data System (ADS)

    Bonne, Jean-Louis; Steen-Larsen, Hans Christian; Masson-Delmotte, Valérie; Sodemann, Harald; Lacour, Jean-Lionel; Risi, Camille; Werner, Martin; Clerbaux, Cathy; Fettweis, Xavier

    2014-05-01

    In July 2012, an extreme warm event occurred in Greenland, leading to surface melt over almost all the ice sheet. This event was recorded in the isotopic composition of water vapour measured by the IASI satellite along the transport pathway and at two sites where continuous in situ surface vapour isotopic measurements were conducted, situated at a coastal station of South Greenland (Ivittuut) and further North on top of the ice sheet (NEEM, NW Greenland). These observations allowed us to monitor the isotopic composition of the air mass at different stages of its advection towards Greenland, which can inform on processes along this trajectory, such as cloud properties and moisture sources. In addition, two simulations of this event, using the atmospheric general circulation models LMDZiso and ECHAM5wiso equipped with water stable isotopes and nudged towards large scale wind fields, are investigated. Furthermore, a regional high-resolution model was used to study the moisture transport to Greenland during this event using tagged water tracers of the North Atlantic ocean and coastal land evaporation. Using moisture source diagnostic based on the Lagrangian particle dispersion model Flexpart, we show that this 2012 heat wave event corresponds to moisture sources located over the subtropical Atlantic Ocean, where intense evaporation was caused by dry air masses associated with the US intense summer drought. This moisture was then advected northward along a narrow band, due to a very stationary surface cyclone southwest of Greenland, reached southern Greenland and Ivittuut coastal station on July 9th, travelled along the west coast of Greenland, continued eastwards above the ice sheet and arrived above the NEEM deep drilling camp on July 11th. Surface isotopic observations during the event show larger variations at NEEM than in Ivittuut, strongly reducing the isotopic and deuterium excess latitudinal gradient usually observed between South and North Greenland. This

  14. The impact of microwave absorber and radome geometries on GNSS measurements of station coordinates and atmospheric water vapour

    NASA Astrophysics Data System (ADS)

    Ning, T.; Elgered, G.; Johansson, J. M.

    2011-01-01

    We have used microwave absorbing material in different geometries around ground-based Global Navigation Satellite System (GNSS) antennas in order to mitigate multipath effects on the estimates of station coordinates and atmospheric water vapour. The influence of a hemispheric radome - of the same type as in the Swedish GPS network SWEPOS - was also investigated. Two GNSS stations at the Onsala Space Observatory were used forming a 12 m baseline. GPS data from October 2008 to November 2009 were analyzed by the GIPSY/OASIS II software using the Precise Point Positioning (PPP) processing strategy for five different elevation cutoff angles from 5° to 25°. We found that the use of the absorbing material decreases the offset in the estimated vertical component of the baseline from ˜27 mm to ˜4 mm when the elevation cutoff angle varies from 5° to 20°. The horizontal components are much less affected. The corresponding offset in the estimates of the atmospheric Integrated Water Vapour (IWV) decreases from ˜1.6 kg/m2 to ˜0.3 kg/m2. Changes less than 5 mm in the offsets in the vertical component of the baseline are seen for all five elevation cutoff angle solutions when the antenna was covered by a hemispheric radome. Using the radome affects the IWV estimates less than 0.4 kg/m2 for all different solutions. IWV comparisons between a Water Vapour Radiometer (WVR) and the GPS data give consistent results.

  15. Variability of winter-time middle atmospheric water vapour over the Arctic as observed with a ground-based microwave radiometer

    NASA Astrophysics Data System (ADS)

    Tschanz, Brigitte; Kivi, Rigel; Rüfenacht, Rolf; Kämpfer, Niklaus

    2014-05-01

    Middle atmospheric water vapour has a long chemical lifetime and can therefore be used as a tracer for dynamics. The ground-based microwave radiometer MIAWARA-C is designed for the use on campaigns and measures profiles of water vapour in the upper stratosphere and mesosphere and thus provides valuable data for the investigation of atmospheric processes. It has been operational for five years and has successfully participated in measurement campaigns under various climatic conditions in Germany, Switzerland, California, Finland and on la Réunion. The temporal resolution of the obtained water vapour profiles approximately 2 hours depending on tropospheric conditions. During two campaigns from January to June 2010 and from July 2011 to April 2013 in Sodankylä, Finland, MIAWARA-C monitored time series of polar middle atmospheric water vapour for three winters with three Sudden Stratospheric Warmings (SSW) occurring in early 2010, 2012 and 2013. The obtained time series are used to study the effects of the three SSWs on middle-atmospheric water vapour. During an SSW, humid mid- to low-latitude air is transported towards the polar region resulting in a fast increase in water vapour. The descent of water vapour after the SSW allows the estimation of the descent rate over the polar region as the normal wintertime circulation reforms. Results from the three SSWs are compared. The ground-based water vapour data is combined with sonde data of the Finnish Meteorological Institute and ground-based microwave wind measurements for one winter in order to obtain a more complete picture of the dynamics in the polar winter atmosphere.

  16. Comparison of atmospheric water vapour content with GNSS, Radiosonde, Microwave radiometer, and Lidar

    NASA Astrophysics Data System (ADS)

    Sohn, D.; Park, K.

    2012-12-01

    The increased amount of saturated water vapor due to the Earth's temperature rise frequently causes abnormal meteorological phenomena such as local severe rainfall in Korea. The National Institute of Meteorological Research of Korea Meteorological Administration (KMA) conducted observation experiments using a variety of water-vapor measuring equipments to improve the accuracy of weather forecasts and accurately measure the precipitable water vapor in the atmosphere. Equipments used were GNSS, water vapor radiometers (WVR), radiosonde, and LiDAR. For GNSS measurements we used two receivers that can collect not only GPS but also GLONASS signals: Trimble NetR5 and Septentrio PolaRx4. The two WVR makers are Raidometrics and RPG. For radiosonde observations, KMA launched Vaisala GPSondes every 6 hours during the experiment period. The LiDAR system was made locally by Hanbat University in Daejeon. Thus, we could obtain collocation experiment results from 6 different kinds of water vapor measurement and analyze the characteristics of each device.

  17. Temporal evolution of temperature and OH density produced by nanosecond repetitively pulsed discharges in water vapour at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Sainct, F. P.; Lacoste, D. A.; Kirkpatrick, M. J.; Odic, E.; Laux, C. O.

    2014-02-01

    We report on an experimental study of the temporal evolution of OH density and gas temperature in spark discharges created by nanosecond repetitively pulsed discharges in pure water vapour at 475 K and atmospheric pressure. The plasma was generated by 20 kV, 20 ns pulses, at a repetition frequency of 10 kHz. The temperature was measured during the discharge by optical emission spectroscopy of the second positive system of N2, and between two discharges by two-colour OH-planar laser induced fluorescence (OH-PLIF) using two pairs of rotational transitions. Between two successive discharges, the relative density of OH was measured by OH-PLIF and was found to decay very slowly, with a 1/e decay time of about 50 µs. With the use of a chemical kinetics model, the OH density was placed on an absolute scale.

  18. Systematic trend of water vapour absorption in red giant atmospheres revealed by high resolution TEXES 12 μm spectra

    NASA Astrophysics Data System (ADS)

    Ryde, N.; Lambert, J.; Farzone, M.; Richter, M. J.; Josselin, E.; Harper, G. M.; Eriksson, K.; Greathouse, T. K.

    2015-01-01

    Context. The structures of the outer atmospheres of red giants are very complex. Recent interpretations of a range of different observations have led to contradictory views of these regions. It is clear, however, that classical model photospheres are inadequate to describe the nature of the outer atmospheres. The notion of large optically thick molecular spheres around the stars (MOLspheres) has been invoked in order to explain spectro-interferometric observations and low- and high-resolution spectra. On the other hand high-resolution spectra in the mid-IR do not easily fit into this picture because they rule out any large sphere of water vapour in LTE surrounding red giants. Aims: In order to approach a unified scenario for these outer regions of red giants, more empirical evidence from different diagnostics are needed. Our aim here is to investigate high-resolution, mid-IR spectra for a range of red giants, spanning spectral types from early K to mid M. We want to study how the pure rotational lines of water vapour change with effective temperature, and whether we can find common properties that can put new constraints on the modelling of these regions, so that we can gain new insights. Methods: We have recorded mid-IR spectra at 12.2 - 12.4 μm at high spectral resolution of ten well-studied bright red giants, with TEXES mounted on the IRTF on Mauna Kea. These stars span effective temperatures from 3450 K to 4850 K. Results: We find that all red giants in our study cooler than 4300 K, spanning a wide range of effective temperatures (down to 3450 K), show water absorption lines stronger than expected and none are detected in emission, in line with what has been previously observed for a few stars. The strengths of the lines vary smoothly with spectral type. We identify several spectral features in the wavelength region that are undoubtedly formed in the photosphere. From a study of water-line ratios of the stars, we find that the excitation temperatures, in the

  19. Gravimetric phenotyping of whole plant transpiration responses to atmospheric vapour pressure deficit identifies genotypic variation in water use efficiency.

    PubMed

    Ryan, Annette C; Dodd, Ian C; Rothwell, Shane A; Jones, Ros; Tardieu, Francois; Draye, Xavier; Davies, William J

    2016-10-01

    There is increasing interest in rapidly identifying genotypes with improved water use efficiency, exemplified by the development of whole plant phenotyping platforms that automatically measure plant growth and water use. Transpirational responses to atmospheric vapour pressure deficit (VPD) and whole plant water use efficiency (WUE, defined as the accumulation of above ground biomass per unit of water used) were measured in 100 maize (Zea mays L.) genotypes. Using a glasshouse based phenotyping platform with naturally varying VPD (1.5-3.8kPa), a 2-fold variation in WUE was identified in well-watered plants. Regression analysis of transpiration versus VPD under these conditions, and subsequent whole plant gas exchange at imposed VPDs (0.8-3.4kPa) showed identical responses in specific genotypes. Genotype response of transpiration versus VPD fell into two categories: 1) a linear increase in transpiration rate with VPD with low (high WUE) or high (low WUE) transpiration rate at all VPDs, 2) a non-linear response with a pronounced change point at low VPD (high WUE) or high VPD (low WUE). In the latter group, high WUE genotypes required a significantly lower VPD before transpiration was restricted, and had a significantly lower rate of transpiration in response to VPD after this point, when compared to low WUE genotypes. Change point values were significantly positively correlated with stomatal sensitivity to VPD. A change point in stomatal response to VPD may explain why some genotypes show contradictory WUE rankings according to whether they are measured under glasshouse or field conditions. Furthermore, this novel use of a high throughput phenotyping platform successfully reproduced the gas exchange responses of individuals measured in whole plant chambers, accelerating the identification of plants with high WUE. PMID:27593468

  20. Variability of water vapour in the Arctic stratosphere

    NASA Astrophysics Data System (ADS)

    Thölix, L.; Backman, L.; Kivi, R.; Karpechko, A.

    2015-08-01

    This study evaluates the stratospheric water vapour distribution and variability in the Arctic. A FinROSE chemistry climate model simulation covering years 1990-2013 is compared to observations (satellite and frostpoint hygrometer soundings) and the sources of stratospheric water vapour are studied. According to observations and the simulations the water vapour concentration in the Arctic stratosphere started to increase after year 2006, but around 2011 the concentration started to decrease. Model calculations suggest that the increase in water vapour during 2006-2011 (at 56 hPa) is mostly explained by transport related processes, while the photochemically produced water vapour plays a relatively smaller role. The water vapour trend in the stratosphere may have contributed to increased ICE PSC occurrence. The increase of water vapour in the precense of the low winter temperatures in the Arctic stratosphere led to more frequent occurrence of ICE PSCs in the Arctic vortex. The polar vortex was unusually cold in early 2010 and allowed large scale formation of the polar stratospheric clouds. The cold pool in the stratosphere over the Northern polar latitudes was large and stable and a large scale persistent dehydration was observed. Polar stratospheric ice clouds and dehydration were observed at Sodankylä with accurate water vapour soundings in January and February 2010 during the LAPBIAT atmospheric sounding campaign. The observed changes in water vapour were reproduced by the model. Both the observed and simulated decrease of the water vapour in the dehydration layer was up to 1.5 ppm.

  1. Variability of water vapour in the Arctic stratosphere

    NASA Astrophysics Data System (ADS)

    Thölix, Laura; Backman, Leif; Kivi, Rigel; Karpechko, Alexey Yu.

    2016-04-01

    This study evaluates the stratospheric water vapour distribution and variability in the Arctic. A FinROSE chemistry transport model simulation covering the years 1990-2014 is compared to observations (satellite and frost point hygrometer soundings), and the sources of stratospheric water vapour are studied. In the simulations, the Arctic water vapour shows decadal variability with a magnitude of 0.8 ppm. Both observations and the simulations show an increase in the water vapour concentration in the Arctic stratosphere after the year 2006, but around 2012 the concentration started to decrease. Model calculations suggest that this increase in water vapour is mostly explained by transport-related processes, while the photochemically produced water vapour plays a relatively smaller role. The increase in water vapour in the presence of the low winter temperatures in the Arctic stratosphere led to more frequent occurrence of ice polar stratospheric clouds (PSCs) in the Arctic vortex. We perform a case study of ice PSC formation focusing on January 2010 when the polar vortex was unusually cold and allowed large-scale formation of PSCs. At the same time a large-scale persistent dehydration was observed. Ice PSCs and dehydration observed at Sodankylä with accurate water vapour soundings in January and February 2010 during the LAPBIAT (Lapland Atmosphere-Biosphere facility) atmospheric measurement campaign were well reproduced by the model. In particular, both the observed and simulated decrease in water vapour in the dehydration layer was up to 1.5 ppm.

  2. Enceladus' Water Vapour Plumes

    NASA Technical Reports Server (NTRS)

    Hansen, Candice J.; Esposito, L.; Colwell, J.; Hendrix, A.; Matson, Dennis; Parkinson, C.; Pryor, W.; Shemansky, D.; Stewart, I.; Tew, J.; Yung, Y.

    2006-01-01

    A viewgraph presentation on the discovery of Enceladus water vapor plumes is shown. Conservative modeling of this water vapor is also presented and also shows that Enceladus is the source of most of the water required to supply the neutrals in Saturn's system and resupply the E-ring against losses.

  3. Water Vapour Mixing Ratio Measurements in Potenza in the Frame of the International Network for the Detection of Atmospheric Composition Change - NDACC

    NASA Astrophysics Data System (ADS)

    De Rosa, Benedetto; Di Girolamo, Paolo; Summa, Donato; Stelitano, Dario; Mancini, Ignazio

    2016-06-01

    In November 2012 the University of BASILicata Raman Lidar system (BASIL) was approved to enter the International Network for the Detection of Atmospheric Composition Change (NDACC). This network includes more than 70 high-quality, remote-sensing research stations for observing and understanding the physical and chemical state of the upper troposphere and stratosphere and for assessing the impact of stratosphere changes on the underlying troposphere and on global climate. As part of this network, more than thirty groundbased Lidars deployed worldwide are routinely operated to monitor atmospheric ozone, temperature, aerosols, water vapour, and polar stratospheric clouds. In the frame of NDACC, BASIL performs measurements on a routine basis each Thursday, typically from local noon to midnight, covering a large portion of the daily cycle. Measurements from BASIL are included in the NDACC database both in terms of water vapour mixing ratio and temperature. This paper illustrates some measurement examples from BASIL, with a specific focus on water vapour measurements, with the goal to try and characterize the system performances.

  4. Detection of water vapour absorption around 363nm in measured atmospheric absorption spectra and its effect on DOAS evaluations

    NASA Astrophysics Data System (ADS)

    Lampel, Johannes; Polyansky, Oleg. L.; Kyuberis, Alexandra A.; Zobov, Nikolai F.; Tennyson, Jonathan; Lodi, Lorenzo; Pöhler, Denis; Frieß, Udo; Platt, Ulrich; Beirle, Steffen; Wagner, Thomas

    2016-04-01

    Water vapour is known to absorb light from the microwave region to the blue part of the visible spectrum at a decreasing magnitude. Ab-initio approaches to model individual absorption lines of the gaseous water molecule predict absorption lines until its dissociation limit at 243 nm. We present first evidence of water vapour absorption at 363 nm from field measurements based on the POKAZATEL absorption line list by Polyansky et al. (2016) using data from Multi-Axis differential optical absorption spectroscopy (MAX-DOAS) and Longpath (LP)-DOAS measurements. The predicted absorptions contribute significantly to the observed optical depths with up to 2 × 10‑3. Their magnitude correlates well (R2 = 0.89) to simultaneously measured well-established water vapour absorptions in the blue spectral range from 452-499 nm, but is underestimated by a factor of 2.6 ± 0.6 in the ab-initio model. At a spectral resolution of 0.5nm this leads to a maximum absorption cross-section value of 5.4 × 10‑27 cm2/molec at 362.3nm. The results are independent of the employed cross-section data to compensate for the overlayed absorption of the oxygen dimer O4. The newly found absorption can have a significant impact on the spectral retrieval of absorbing trace-gas species in the spectral range around 363 nm. Its effect on the spectral analysis of O4, HONO and OClO are discussed.

  5. Electron Transport in Water Vapour

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Satoru; Satoh, Kohki; Itoh, Hidenori

    2015-09-01

    Sets of electron collision cross sections for water vapour previously reported are examined by comparing calculated electron swarm parameters with measured parameters. Further, reliable cross section set of water vapour is estimated by the electron swarm method using Monte Carlo simulation to ensure the accuracy of the swarm parameter calculation. The values of an electron drift velocity, a longitudinal diffusion coefficient, and an effective ionisation coefficient calculated from Yousfi and Benabdessadok's set and those calculated from Itikawa and Mason's set do not necessarily agree with measured data. A new cross section set of water vapour, which consists of three kinds of rotational excitation, two kinds of vibrational excitation, three kinds of electron attachment, twenty-six kinds of electronic excitation, and six kinds of ionisation cross sections, and an elastic collision cross section, is estimated, and an anisotropic electron scattering for elastic and rotational excitation collision is considered. The swarm parameters calculated from the estimated cross section set is in good agreement with measured data in a wide range of reduced electric field.

  6. Measuring variations of δ18O and δ2H in atmospheric water vapour using laser spectroscopy: an instrument characterisation study

    NASA Astrophysics Data System (ADS)

    Aemisegger, F.; Sturm, P.; Graf, P.; Sodemann, H.; Pfahl, S.; Knohl, A.; Wernli, H.

    2012-02-01

    Variations of stable water isotopes in water vapour have become measurable at a measurement frequency of about 1 Hz in recent years using novel laser spectroscopic techniques. This enables us to perform continuous measurements for process-based investigations of the atmospheric water cycle at the time scales relevant for synoptic meteorology. An important prerequisite for the interpretation of data from automated field measurements lasting for several weeks or months is a detailed knowledge about instrument properties and the sources of measurement uncertainty. We present here a comprehensive characterisation and comparison study of two commercial laser spectroscopic systems based on cavity ring-down spectroscopy (Picarro) and off-axis integrated cavity output spectroscopy (Los Gatos Research). The uncertainty components of the measurements were first assessed in laboratory experiments, focussing on the effects of (i) water vapour mixing ratio, (ii) measurement stability, (iii) uncertainties due to calibration and (iv) response times of the isotope measurements due to adsorption-desorption processes on the tubing and measurement cavity walls. Based on the experience from our laboratory experiments we set up a one-week field campaign for comparing measurements of the ambient isotope signals of the two laser spectroscopic systems. The optimal calibration strategy determined for both instruments was applied as well as the correction functions for water vapour mixing ratio effects. The root mean square difference between the isotope signals from the two instruments during the field deployment was 2.3‰ for δ2H, 0.5‰ for δ18O and 3.1‰ for deuterium excess. These uncertainty estimates from field measurements compare well to those found in the laboratory experiments. The present quality of measurements from laser spectroscopic instruments combined with a calibration system opens new possibilities for investigating the atmospheric water cycle and the land-atmosphere

  7. Measuring variations of δ18O and δ2H in atmospheric water vapour using two commercial laser-based spectrometers: an instrument characterisation study

    NASA Astrophysics Data System (ADS)

    Aemisegger, F.; Sturm, P.; Graf, P.; Sodemann, H.; Pfahl, S.; Knohl, A.; Wernli, H.

    2012-07-01

    Variations of stable water isotopes in water vapour have become measurable at a measurement frequency of about 1 Hz in recent years using novel laser spectroscopic techniques. This enables us to perform continuous measurements for process-based investigations of the atmospheric water cycle at the time scales relevant for synoptic and mesoscale meteorology. An important prerequisite for the interpretation of data from automated field measurements lasting for several weeks or months is a detailed knowledge about instrument properties and the sources of measurement uncertainty. We present here a comprehensive characterisation and comparison study of two commercial laser spectroscopic systems based on cavity ring-down spectroscopy (Picarro) and off-axis integrated cavity output spectroscopy (Los Gatos Research). The uncertainty components of the measurements were first assessed in laboratory experiments, focussing on the effects of (i) water vapour mixing ratio, (ii) measurement stability, (iii) uncertainties due to calibration and (iv) response times of the isotope measurements due to adsorption-desorption processes on the tubing and measurement cavity walls. Based on the experience from our laboratory experiments, we set up a one-week field campaign for comparing measurements of the ambient isotope signals from the two laser spectroscopic systems. The optimal calibration strategy determined for both instruments was applied as well as the correction functions for water vapour mixing ratio effects. The root mean square difference between the isotope signals from the two instruments during the field deployment was 2.3‰ for δ2H, 0.5‰ for δ18O and 3.1‰ for deuterium excess. These uncertainty estimates from field measurements compare well to those found in the laboratory experiments. The present quality of measurements from laser spectroscopic instruments combined with a calibration system opens new possibilities for investigating the atmospheric water cycle and

  8. A water vapour monitor at Paranal Observatory

    NASA Astrophysics Data System (ADS)

    Kerber, Florian; Rose, Thomas; Chacón, Arlette; Cuevas, Omar; Czekala, Harald; Hanuschik, Reinhard; Momany, Yazan; Navarrete, Julio; Querel, Richard R.; Smette, Alain; van den Ancker, Mario E.; Cure, Michel; Naylor, David A.

    2012-09-01

    We present the performance characteristics of a water vapour monitor that has been permanently deployed at ESO's Paranal observatory as a part of the VISIR upgrade project. After a careful analysis of the requirements and an open call for tender, the Low Humidity and Temperature Profiling microwave radiometer (LHATPRO), manufactured by Radiometer Physics GmbH (RPG), has been selected. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.5 mm). The unit comprises the above humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared radiometer (~10 μm) for cloud detection. The instrument has been commissioned during a 2.5 week period in Oct/Nov 2011, by comparing its measurements of PWV and atmospheric profiles with the ones obtained by 22 radiosonde balloons. In parallel an IR radiometer (Univ. Lethbridge) has been operated, and various observations with ESO facility spectrographs have been taken. The RPG radiometer has been validated across the range 0.5 - 9 mm demonstrating an accuracy of better than 0.1 mm. The saturation limit of the radiometer is about 20 mm. Currently, the radiometer is being integrated into the Paranal infrastructure to serve as a high time-resolution monitor in support of VLT science operations. The water vapour radiometer's ability to provide high precision, high time resolution information on this important aspect of the atmosphere will be most useful for conducting IR observations with the VLT under optimal conditions.

  9. Is there a solar signal in lower stratospheric water vapour?

    NASA Astrophysics Data System (ADS)

    Schieferdecker, Tobias; Lossow, Stefan; Stiller, Gabriele; von Clarmann, Thomas

    2016-04-01

    A merged time series of stratospheric water vapour built from the Halogen Occultation Instrument (HALOE) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) data between 60 deg S and 60 deg N and 15 to 30 km, and covering the years 1992 to 2012, was analysed by multivariate linear regression, including an 11-year solar cycle proxy. Lower stratospheric water vapour was found to reveal a phase-shifted anti-correlation with the solar cycle, with lowest water vapour after solar maximum. The phase shift is composed of an inherent constant time lag of about 2 years and a second component following the stratospheric age of air. The amplitudes of the water vapour response are largest close to the tropical tropopause (up to 0.35 ppmv) and decrease with altitude and latitude. Including the solar cycle proxy in the regression results in linear trends of water vapour being negative over the full altitude/latitude range, while without the solar proxy, positive water vapour trends in the lower stratosphere were found. We conclude from these results that a solar signal seems to be generated at the tropical tropopause which is most likely imprinted on the stratospheric water vapour abundances and transported to higher altitudes and latitudes via the Brewer-Dobson circulation. Hence it is concluded that the tropical tropopause temperature at the final dehydration point of air may also be governed to some degree by the solar cycle. The negative water vapour trends obtained when considering the solar cycle impact on water vapour abundances can possibly solve the "water vapour conundrum" of increasing stratospheric water vapour abundances despite constant or even decreasing tropopause temperatures.

  10. Is there a solar signal in lower stratospheric water vapour?

    NASA Astrophysics Data System (ADS)

    Schieferdecker, T.; Lossow, S.; Stiller, G. P.; von Clarmann, T.

    2015-09-01

    A merged time series of stratospheric water vapour built from the Halogen Occultation Instrument (HALOE) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) data between 60° S and 60° N and 15 to 30 km and covering the years 1992 to 2012 was analysed by multivariate linear regression, including an 11-year solar cycle proxy. Lower stratospheric water vapour was found to reveal a phase-shifted anti-correlation with the solar cycle, with lowest water vapour after solar maximum. The phase shift is composed of an inherent constant time lag of about 2 years and a second component following the stratospheric age of air. The amplitudes of the water vapour response are largest close to the tropical tropopause (up to 0.35 ppmv) and decrease with altitude and latitude. Including the solar cycle proxy in the regression results in linear trends of water vapour being negative over the full altitude/latitude range, while without the solar proxy, positive water vapour trends in the lower stratosphere were found. We conclude from these results that a solar signal seems to be generated at the tropical tropopause which is most likely imprinted on the stratospheric water vapour abundances and transported to higher altitudes and latitudes via the Brewer-Dobson circulation. Hence it is concluded that the tropical tropopause temperature at the final dehydration point of air may also be governed to some degree by the solar cycle. The negative water vapour trends obtained when considering the solar cycle impact on water vapour abundances can possibly solve the "water vapour conundrum" of increasing stratospheric water vapour abundances despite constant or even decreasing tropopause temperatures.

  11. Contributions of evaporation, isotopic non-steady state transpiration and atmospheric mixing on the delta18O of water vapour in Pacific Northwest coniferous forests.

    PubMed

    Lai, Chun-Ta; Ehleringer, James R; Bond, Barbara J; Paw U, Kyaw Tha

    2006-01-01

    Changes in the 2H and 18O of atmospheric water vapour provide information for integrating aspects of gas exchange within forest canopies. In this study, we show that diurnal fluctuations in the oxygen isotope ratio (delta 18O) as high as 4% per hundred were observed for water vapour (delta (18)Ovp) above and within an old-growth coniferous forest in the Pacific Northwest region of the United States. Values of delta 18Ovp decreased in the morning, reached a minimum at midday, and recovered to early-morning values in the late afternoon, creating a nearly symmetrical diurnal pattern for two consecutive summer days. A mass balance budget was derived and assessed for the 18O of canopy water vapour over a 2-d period by considering the 18O-isoflux of canopy transpiration, soil evaporation and the air entering the canopy column. The budget was used to address two questions: (1) do delta 18O values of canopy water vapour reflect the biospheric influence, or are such signals swamped by atmospheric mixing? and (2) what mechanisms drive temporal variations of delta 18Ovp? Model calculations show that the entry of air into the canopy column resulted in an isotopically depleted 18O-isoflux in the morning of day 1, causing values of delta 18Ovp, to decrease. An isotopically enriched 18O-isoflux resulting from transpiration then offset this decreased delta 18Ovp later during the day. Contributions of 18O-isoflux from soil evaporation were relatively small on day 1 but were more significant on day 2, despite the small H2(16)O fluxes. From measurements of leaf water volume and sapflux, we determined the turnover time of leaf water in the needles of Douglas-fir trees as approximately 11 h at midday. Such an extended turnover time suggests that transpiration may not have occurred at the commonly assumed isotopic steady state. We tested a non-steady state model for predicting delta 18O of leaf water. Our model calculations show that assuming isotopic steady state increased isoflux of

  12. An investigation into the optimum thickness of titanium dioxide thin films synthesized by using atmospheric pressure chemical vapour deposition for use in photocatalytic water oxidation.

    PubMed

    Hyett, Geoffrey; Darr, Jawwad A; Mills, Andrew; Parkin, Ivan P

    2010-09-10

    Twenty eight films of titanium dioxide of varying thickness were synthesised by using atmospheric pressure chemical vapour deposition (CVD) of titanium(IV) chloride and ethyl acetate onto glass and titanium substrates. Fixed reaction conditions at a substrate temperature of 660 °C were used for all depositions, with varying deposition times of 5-60 seconds used to control the thickness of the samples. A sacrificial electron acceptor system composed of alkaline sodium persulfate was used to determine the rate at which these films could photo-oxidise water in the presence of 365 nm light. The results of this work showed that the optimum thickness for CVD films on titanium substrates for the purposes of water oxidation was ≈200 nm, and that a platinum coating on the reverse of such samples leads to a five-fold increase in the observed rate of water oxidation. PMID:20645333

  13. Emission, absorption and group delay of microwaves in the atmosphere in relation to water vapour content over the Indian subcontinent

    NASA Technical Reports Server (NTRS)

    Sen, A. K.; Gupta, A. K. D.; Karmakar, P. K.; Barman, S. D.; Bhattacharya, A. B.; Purkait, N.; Gupta, M. K. D.; Sehra, J. S.

    1985-01-01

    The advent of satellite communication for global coverage has apparently indicated a renewed interest in the studies of radio wave propagation through the atmosphere, in the VHF, UHF and microwave bands. The extensive measurements of atmosphere constituents, dynamics and radio meterological parameters during the Middle Atmosphere Program (MAP) have opened up further the possibilities of studying tropospheric radio wave propagation parameters, relevant to Earth/space link design. The three basic parameters of significance to radio propagation are thermal emission, absorption and group delay of the atmosphere, all of which are controlled largely by the water vapor content in the atmosphere, particular at microwave bands. As good emitters are also good absorbers, the atmospheric emission as well as the absorption attains a maximum at the frequency of 22.235 GHz, which is the peak of the water vapor line. The group delay is practically independent of frequency in the VHF, UHF and microwave bands. However, all three parameters exhibit a similar seasonal dependence originating presumably from the seasonal dependence of the water vapor content. Some of the interesting results obtained from analyses of radiosonde data over the Indian subcontinent collected by the India Meteorological Department is presented.

  14. EDITORIAL Metal vapour in atmospheric-pressure arcs Metal vapour in atmospheric-pressure arcs

    NASA Astrophysics Data System (ADS)

    Murphy, Anthony B.

    2010-11-01

    Metal vapour has a significant, and in some cases dominant, influence in many applications of atmospheric-pressure plasmas, including arc welding, circuit interruption and mineral processing. While the influence of metal vapour has long been recognized, it is only recently that diagnostic and computational tools have been sufficiently well-developed to allow this influence to be more thoroughly examined and understood. Some unexpected findings have resulted: for example, that the presence of metal vapour in gas-metal arc welding leads to local minima in the temperature and current density in the centre of the arc. It has become clear that the presence of metal vapour, as well as having intrinsic scientific interest, plays an important role in determining the values of critical parameters in industrial applications, such as the weld penetration in arc welding and the extinction time in circuit breakers. In gas-tungsten arc welding, metal vapour concentrations are formed by evaporation of the weld pool, and are relatively low, typically at most a few per cent. Moreover, the convective flow of the plasma near the weld pool tends to direct the metal vapour plume radially outwards. In gas-metal arc welding, in contrast, metal vapour concentrations can reach over 50%. In this case, the metal vapour is produced mainly by evaporation of the wire electrode, and the strong downwards convective flow below the electrode concentrates the metal vapour in the central region of the arc. The very different metal concentrations and distributions in the two welding processes mean that the metal vapour has markedly different influences on the arc. In gas-tungsten arc welding, the current density distribution is broadened near the weld pool by the influence of the metal vapour on the electrical conductivity of the plasma, and the arc voltage is decreased. In contrast, in gas-metal arc welding, the arc centre is cooled by increased radiative emission and the arc voltage is increased. In

  15. Global trends and variability in integrated water vapour from ground-based GPS data and atmospheric models

    NASA Astrophysics Data System (ADS)

    Bock, Olivier; Parracho, Ana; Bastin, Sophie; Hourdin, Frededic; Mellul, Lidia

    2016-04-01

    A high-quality, consistent, global, long-term dataset of integrated water vapour (IWV) was produced from Global Positioning System (GPS) measurements at more than 400 sites over the globe among which 120 sites have more than 15 years of data. The GPS delay data were converted to IWV using surface pressure and weighted mean temperature estimates from ERA-Interim reanalysis. A two-step screening method was developed to detect and remove outliers in the IWV data. It is based on: 1) GPS data processing information and delay formal errors, and 2) intercomparison with ERA-Interim reanalysis data. The GPS IWV data are also homogenized to correct for offsets due to instrumental changes and other unknown factors. The differential homogenization method uses ERA-Interim IWV as a reference. The resulting GPS data are used to document the mean distribution, the global trends and the variability of IWV over the period 1995-2010, and are analysed in coherence with precipitation and surface temperature data (from observations and ERA-Interim reanalysis). These data are also used to assess global climate model simulations extracted from the IPCC AR5 archive. Large coherent spatial patterns of moistening and drying are evidenced but significant discrepancies are also seen between GPS measurements, reanalysis and climate models in various regions. In terms of variability, the monthly mean anomalies are intercompared. The temporal correlation between GPS and the climate model simulations is overall quite small but the spatial variation of the magnitude of the anomalies is globally well simulated. GPS IWV data prove to be useful to validate global climate model simulations and highlight deficiencies in their representation of the water cycle.

  16. Multi-scale analysis of the impact of increased spatial resolution of soil moisture and atmospheric water vapour on convective precipitation

    NASA Astrophysics Data System (ADS)

    Khodayar, S.; Schaedler, G.; Kalthoff, N.

    2010-09-01

    The distribution of water vapour in the planetary boundary layer (PBL) and its development over time is one of the most important factors affecting precipitation processes. Despite the dense radiosonde network deployed during the Convective and Orographically-induced Precipitation Study (COPS), the high spatial variability of the water vapour field was not well resolved with respect to the detection of the initiation of convection. The first part of this investigation focuses on the impact of an increased resolution of the thermodynamics and dynamics of the PBL on the detection of the initiation of convection. The high spatial resolution was obtained using the synergy effect of data from the networks of radiosondes, automatic weather stations, synoptic stations, and especially Global Positioning Systems (GPSs). A method is introduced to combine GPS and radiosonde data to obtain a higher resolution representation of atmospheric water vapour. The gained spatial resolution successfully improved the representations of the areas where deep convection likelihood was high. Location and timing of the initiation of convection were critically influenced by the structure of the humidity field in the boundary-layer. The availability of moisture for precipitation is controlled by a number of processes including land surface processes, the latter are strongly influenced by spatially variable fields of soil moisture (SM) and land use. Therefore, an improved representation of both fields in regional model systems can be expected to produce better agreement between modelled and measured surface energy fluxes, boundary layer structure and precipitation. SM is currently one of the least assessed quantities with almost no data from operational monitoring networks available. However, during COPS an innovative measurement approach using a very high number of different SM sensors was introduced. The network consisted of newly developed low-cost SM sensors installed at 43 stations. Each

  17. Intercomparison of TCCON and MUSICA Water Vapour Products

    NASA Astrophysics Data System (ADS)

    Weaver, D.; Strong, K.; Deutscher, N. M.; Schneider, M.; Blumenstock, T.; Robinson, J.; Notholt, J.; Sherlock, V.; Griffith, D. W. T.; Barthlott, S.; García, O. E.; Smale, D.; Palm, M.; Jones, N. B.; Hase, F.; Kivi, R.; Ramos, Y. G.; Yoshimura, K.; Sepúlveda, E.; Gómez-Peláez, Á. J.; Gisi, M.; Kohlhepp, R.; Warneke, T.; Dohe, S.; Wiegele, A.; Christner, E.; Lejeune, B.; Demoulin, P.

    2014-12-01

    We present an intercomparison between the water vapour products from the Total Carbon Column Observing Network (TCCON) and the MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water (MUSICA), two datasets from ground-based Fourier Transform InfraRed (FTIR) spectrometers with good global representation. Where possible, comparisons to radiosondes are also included. The near-infrared TCCON measurements are optimized to provide precise monitoring of greenhouse gases for carbon cycle studies; however, TCCON's retrievals also produce water vapour products. The mid-infrared MUSICA products result from retrievals optimized to give precise and accurate information about H2O, HDO, and δD. The MUSICA water vapour products have been validated by extensive intercomparisons with H2O and δD in-situ measurements made from ground, radiosonde, and aircraft (Schneider et al. 2012, 2014), as well as by intercomparisons with satellite-based H2O and δD remote sensing measurements (Wiegele et al., 2014). This dataset provides a valuable reference point for other measurements of water vapour. This study is motivated by the limited intercomparisons performed for TCCON water vapour products and limited characterisation of their uncertainties. We compare MUSICA and TCCON products to assess the potential for TCCON measurements to contribute to studies of the water cycle, water vapour's role in climate and use as a tracer for atmospheric dynamics, and to evaluate the performance of climate models. The TCCON and MUSICA products result from measurements taken using the same FTIR instruments, enabling a comparison with constant instrumentation. The retrieval techniques differ, however, in their method and a priori information. We assess the impact of these differences and characterize the comparability of the TCCON and MUSICA datasets.

  18. Multispecies transmitter for DIAL sensing of atmospheric water vapour, methane and carbon dioxide in the 2 μm region

    NASA Astrophysics Data System (ADS)

    Mammez, Dominique; Cadiou, Erwan; Dherbecourt, Jean-Baptiste; Raybaut, Myriam; Melkonian, Jean-Michel; Godard, Antoine; Gorju, Guillaume; Pelon, Jacques; Lefebvre, Michel

    2015-10-01

    Integrated-path differential absorption lidar (IPDIAL) is an attractive technique to monitor greenhouse gases from space. For that purpose, suitable absorption lines have been identified as good candidates around 2.05 μm for CO2, 2.29 μm for CH4, and 2.06 μm for H2O. In this context, we have developed a high energy transmitter around 2 μm based on frequency conversion in a nested cavity doubly resonant optical parametric oscillator (NesCOPO) followed by high energy parametric amplification. This master oscillator power amplifier (MOPA) architecture enables the generation of tunable single-frequency high energy nanosecond pulses (tens of mJ) suitable for atmospheric DIAL applications. Moreover, taking advantage of the wide spectral coverage capability of the NesCOPO, we demonstrate the potential for this single emitter to address the aforementioned spectral lines, without the use of additional seeding devices. The emitter provides energies up to 20 mJ for the signal waves in the vicinity of CO2 and H2O lines, and 16 mJ at 2290 nm for the CH4 line. By implementing a control loop based on a wavemeter frequency measurement, the signal fluctuations can be maintained below 1 MHz rms for 10 s averaging time. Finally, from optical heterodyne analysis of the beat note between our emitter and a stabilized laser diode, the optical parametric source linewidth was estimated to be better than 60 MHz (Full width at half maximum).

  19. Impact of major volcanic eruptions on stratospheric water vapour

    NASA Astrophysics Data System (ADS)

    Löffler, Michael; Brinkop, Sabine; Jöckel, Patrick

    2016-05-01

    Volcanic eruptions can have a significant impact on the Earth's weather and climate system. Besides the subsequent tropospheric changes, the stratosphere is also influenced by large eruptions. Here changes in stratospheric water vapour after the two major volcanic eruptions of El Chichón in Mexico in 1982 and Mount Pinatubo on the Philippines in 1991 are investigated with chemistry-climate model simulations. This study is based on two simulations with specified dynamics of the European Centre for Medium-Range Weather Forecasts Hamburg - Modular Earth Submodel System (ECHAM/MESSy) Atmospheric Chemistry (EMAC) model, performed within the Earth System Chemistry integrated Modelling (ESCiMo) project, of which only one includes the long-wave volcanic forcing through prescribed aerosol optical properties. The results show a significant increase in stratospheric water vapour induced by the eruptions, resulting from increased heating rates and the subsequent changes in stratospheric and tropopause temperatures in the tropics. The tropical vertical advection and the South Asian summer monsoon are identified as sources for the additional water vapour in the stratosphere. Additionally, volcanic influences on tropospheric water vapour and El Niño-Southern Oscillation (ENSO) are evident, if the long-wave forcing is strong enough. Our results are corroborated by additional sensitivity simulations of the Mount Pinatubo period with reduced nudging and reduced volcanic aerosol extinction.

  20. A new portable generator to dynamically produce SI-traceable reference gas mixtures for VOCs and water vapour at atmospheric concentration

    NASA Astrophysics Data System (ADS)

    Guillevic, Myriam; Pascale, Céline; Ackermann, Andreas; Leuenberger, Daiana; Niederhauser, Bernhard

    2016-04-01

    In the framework of the KEY-VOCs and AtmoChem-ECV projects, we are currently developing new facilities to dynamically generate reference gas mixtures for a variety of reactive compounds, at concentrations measured in the atmosphere and in a SI-traceable way (i.e. the amount of substance fraction in mole per mole is traceable to SI-units). Here we present the realisation of such standards for water vapour in the range 1-10 μmol/mol and for volatile organic compounds (VOCs) such as limonene, alpha-pinene, MVK, MEK, in the nmol/mol range. The matrix gas can be nitrogen or synthetic air. Further development in gas purification techniques could make possible to use purified atmospheric air as carrier gas. The method is based on permeation and dynamic dilution: one permeator containing a pure substance (either water, limonene, MVK, MEK or α-pinene) is kept into a permeation chamber with a constant gas flow. The mass loss is precisely calibrated using a magnetic suspension balance. The carrier gas is purified beforehand from the compounds of interest to the required level, using commercially available purification cartridges. This primary mixture is then diluted to reach the required amount of substance fraction. All flows are piloted by mass flow controllers which makes the production process flexible and easily adaptable to generate the required concentration. All parts in contact with the gas mixture are passivated using coated surfaces, to reduce adsorption/desorption processes as much as possible. Two setups are currently developed: one already built and fixed in our laboratory in Bern as well as a portable generator that is still under construction and that could be used anywhere in the field. The permeation chamber of the portable generator has multiple individual cells allowing the generation of mixtures up to 5 different components if needed. Moreover the presented technique can be adapted and applied to a large variety of molecules (e.g., NO2, BTEX, CFCs

  1. On the vapour trail of an atmospheric imprint in insects.

    PubMed

    Ellwood, M D Farnon; Northfield, Roger G W; Mejia-Chang, Monica; Griffiths, Howard

    2011-08-23

    Terrestrial arthropods, at constant risk from desiccation, are highly sensitive to atmospheric temperature and humidity. A physiological marker of these abiotic conditions could highlight phenotypic adaptations, indicate niche partitioning, and predict responses to climate change for a group representing three-quarters of the Earth's animal species. We show that the (18)O composition of insect haemolymph is such a measure, providing a dynamic and quantitatively predictable signal for respiratory gas exchange and inputs from atmospheric humidity. Using American cockroaches (Periplaneta americana) under defined experimental conditions, we show that insects respiring at low humidity demonstrate the expected enrichment in the (18)O composition of haemolymph because of evaporation. At high humidity, however, diffusional influx of atmospheric water vapour into the animal forces haemolymph to become depleted in (18)O. Additionally, using cockroaches sampled from natural habitats, we show that the haemolymph (18)O signature is transferred to the organic material of the insect's exoskeleton. Insect cuticle, therefore, exhibits the mean atmospheric conditions surrounding the animals prior to moulting. This discovery will help to define the climatic tolerances of species and their habitat preferences, and offers a means of quantifying the balance between niche partitioning and 'neutral' processes in shaping complex tropical forest communities. PMID:21325310

  2. On the vapour trail of an atmospheric imprint in insects

    PubMed Central

    Ellwood, M. D. Farnon; Northfield, Roger G. W.; Mejia-Chang, Monica; Griffiths, Howard

    2011-01-01

    Terrestrial arthropods, at constant risk from desiccation, are highly sensitive to atmospheric temperature and humidity. A physiological marker of these abiotic conditions could highlight phenotypic adaptations, indicate niche partitioning, and predict responses to climate change for a group representing three-quarters of the Earth's animal species. We show that the 18O composition of insect haemolymph is such a measure, providing a dynamic and quantitatively predictable signal for respiratory gas exchange and inputs from atmospheric humidity. Using American cockroaches (Periplaneta americana) under defined experimental conditions, we show that insects respiring at low humidity demonstrate the expected enrichment in the 18O composition of haemolymph because of evaporation. At high humidity, however, diffusional influx of atmospheric water vapour into the animal forces haemolymph to become depleted in 18O. Additionally, using cockroaches sampled from natural habitats, we show that the haemolymph 18O signature is transferred to the organic material of the insect's exoskeleton. Insect cuticle, therefore, exhibits the mean atmospheric conditions surrounding the animals prior to moulting. This discovery will help to define the climatic tolerances of species and their habitat preferences, and offers a means of quantifying the balance between niche partitioning and ‘neutral’ processes in shaping complex tropical forest communities. PMID:21325310

  3. Combined Dial Sounding of Ozone, Water Vapour and Aerosol

    NASA Astrophysics Data System (ADS)

    Trickl, Thomas; Vogelmann, Hannes

    2016-06-01

    Routine high-quality lidar measurements of ozone, water vapour and aerosol at Garmisch-Partenkirchen since 2007 have made possible more comprehensive atmospheric studies and lead to a growing insight concerning the most frequently occurring long-range transport pathways. In this contribution we present as examples results on stratospheric layers travelling in the free troposphere for extended periods of time without eroding. In particular, we present a case of an intrusion layer that subsided over as many as fifteen days and survived the interference by strong Canadian fires. These results impose a challenge on atmospheric modelling that grossly overestimates free-tropospheric mixing.

  4. Water vapour correction of the daily 1 km AVHRR global land dataset: Part I validation and use of the Water Vapour input field

    USGS Publications Warehouse

    DeFelice, Thomas P.; Lloyd, D.; Meyer, D.J.; Baltzer, T. T.; Piraina, P.

    2003-01-01

    An atmospheric correction algorithm developed for the 1 km Advanced Very High Resolution Radiometer (AVHRR) global land dataset was modified to include a near real-time total column water vapour data input field to account for the natural variability of atmospheric water vapour. The real-time data input field used for this study is the Television and Infrared Observational Satellite (TIROS) Operational Vertical Sounder (TOVS) Pathfinder A global total column water vapour dataset. It was validated prior to its use in the AVHRR atmospheric correction process using two North American AVHRR scenes, namely 13 June and 28 November 1996. The validation results are consistent with those reported by others and entail a comparison between TOVS, radiosonde, experimental sounding, microwave radiometer, and data from a hand-held sunphotometer. The use of this data layer as input to the AVHRR atmospheric correction process is discussed.

  5. The Water Vapour Radiometer at Effelsberg

    NASA Astrophysics Data System (ADS)

    Roy, A. L.; Teuber, U.; Keller, R.

    We have installed a scanning 18 GHz to 26 GHz water vapour radiometer on the focus cabin of the Effelsberg 100 m telescope for tropospheric phase, delay and opacity correction during high-frequency VLBI observations. It is based on the design by Tahmoush & Rogers (2000) but with noise injection for calibration, weather-proof housing, and temperature stabilization. The radiometer is delivering data into an archive since July 2003, from which they are available for download. The data will be delivered automatically to PIs of EVN experiments in a calibration table attached by the EVN calibration pipeline. This paper describes the radiometer and its performance.

  6. Precipitable water vapour over La Silla Paranal Observatory

    NASA Astrophysics Data System (ADS)

    Kerber, F.

    2011-11-01

    In support of characterization of potential sites for the European Extremely Large Telescope (E-ELT) the European Southern Observatory (ESO), the Institute for Space Imaging Science (ISIS) and the astrometeorology group of the Universidad Valparaiso have jointly established an improved understanding of atmospheric precipitable water vapour (PWV) above ESO's La Silla Paranal Observatory. To this end we have statistically analysed 8 years worth of high resolution spectra taken with VLT-UVES to reconstruct the PWV history above Paranal. For Silla data from FEROS covering about 5 years have been used. In the analysis a radiative transfer model of Earth's atmosphere (BTRAM) developed by ISIS has been employed. In order to better understand the systematics involved three dedicated campaigns were conducted in May, August and November 2009 during which several instruments and methods were validated with respect to balloon-borne radiosondes, the established standard in atmospheric research. After correction for systematic effects a median PWV of 2.4 mm is found for Paranal whereas the value for La Silla is 3.7 mm. The results of the study were submitted to the E-ELT site selection advisory committee late in 2009. Valuable lessons for observatory operations have been learned and ESO is planning to permanently deploy a water vapour monitor on Paranal as part of the VISIR upgrade project. For the E-ELT we find that a stand-alone high time resolution PWV monitor will be essential for optimizing the scientific output.

  7. Electron swarm parameters in water vapour

    NASA Astrophysics Data System (ADS)

    Hasegawa, H.; Date, H.; Shimozuma, M.

    2007-04-01

    Electron swarm parameters, such as the drift velocity and the ionization coefficient, in water vapour have been measured for relatively wide ranges in reduced electric fields (E/N) at room temperature. The drift velocity (Wm) was obtained based upon the arrival-time spectra of electrons by using a double-shutter drift tube for the E/N from 60 to 1000 Td, while the first and second ionization coefficients (α and γ) were determined by the steady-state Townsend method from 50 to 3000 Td. A comparison between the results and other data in the literature shows that our results for both the drift velocity and the effective ionization coefficient are lower than those of the other data in the above ranges.

  8. A solar signal in lower stratospheric water vapour?

    NASA Astrophysics Data System (ADS)

    Schieferdecker, T.; Lossow, S.; Stiller, G. P.; von Clarmann, T.

    2015-04-01

    A merged time series of stratospheric water vapour built from HALOE and MIPAS data between 60° S and 60° N and 15 to 30 km and covering the years 1992 to 2012 was analyzed by multivariate linear regression including an 11 year solar cycle proxy. Lower stratospheric water vapour was found to reveal a phase-shifted anti-correlation with the solar cycle, with lowest water vapour after solar maximum. The phase shift is composed of an inherent constant time lag of about 2 years and a second component following the stratospheric age of air. The amplitudes of the water vapour response are largest close to the tropical tropopause (up to 0.35 ppmv) and decrease with altitude and latitude. Including the solar cycle proxy in the regression results in linear trends of water vapour being negative over the full altitude/latitude range, while without the solar proxy positive water wapour trends in the lowermost stratosphere were found. We conclude from these results that a solar signal generated at the tropical tropopause is imprinted on the stratospheric water vapour abundances and transported to higher altitudes and latitudes via the Brewer-Dobson circulation. Hence it is concluded that the tropical tropopause temperature at the final dehydration point of air is also governed to some degree by the solar cycle. The negative water vapour trends obtained when considering the solar cycle impact on water vapour abundances can solve the water vapour conundrum of increasing stratospheric water vapour abundances at constant or even decreasing tropopause temperatures.

  9. GPS tomographic experiment on water vapour dynamics in the troposphere over Lisbon

    NASA Astrophysics Data System (ADS)

    Benevides, Pedro; Catalao, Joao; Miranda, Pedro

    2015-04-01

    Quantification of the water vapour variability on the atmosphere remains a difficult task, affecting the weather prediction. Coarse water vapour resolution measurements in space and time affect the numerical weather prediction solution models causing artifacts in the prediction of severe weather phenomena. The GNSS atmospheric processing has been developed in the past years providing integrated water vapour estimates comparable with the meteorological sensor measurements, with studies registering 1 to 2 kg/m2 bias, but lack a vertical determination of the atmospheric processes. The GNSS tomography in the troposphere is one of the most promising techniques for sensing the three-dimensional water vapour state of the atmosphere. The determination of the integrated water vapour profile by means of the widely accepted GNSS meteorology techniques, allows the reconstruction of several slant path delay rays in the satellite line of view, providing an opportunity to sense the troposphere at tree-dimensions plus time. The tomographic system can estimate an image solution of the water vapour but impositions have to be introduced to the system of equations inversion because of the non-optimal GNSS observation geometry. Application of this technique on atmospheric processes like large convective precipitation or mesoscale water vapour circulation have been able to describe its local dynamic vertical variation. A 3D tomographic experiment was developed over an area of 60x60 km2 around Lisbon (Portugal). The GNSS network available composed by 9 receivers was used for an experiment of densification of the permanent network using 8 temporarily installed GPS receivers (totalling 17 stations). This study was performed during several weeks in July 2013, where a radiosonde campaign was also held in order to validate the tomographic inversion solution. 2D integrated water vapour maps directly obtained from the GNSS processing were also evaluated and local coastal breeze circulation

  10. Calibration of the Purple Crow Lidar vibrational Raman water-vapour mixing ratio and temperature measurements

    NASA Astrophysics Data System (ADS)

    Argall, P. S.; Sica, R. J.; Bryant, C. R.; Algara-Siller, M.; Schijns, H.

    2007-02-01

    Purple Crow Lidar (PCL) measurements of the vibrational Raman-shifted backscatter from water vapour and nitrogen molecules allows height profiles of the water-vapour mixing ratio to be measured from 500 m up into the lower stratosphere. In addition, the Raman nitrogen measurements allow the determination of temperature profiles from about 10 to 40 km altitude. However, external calibration of these measurements is necessary to compensate for instrumental effects, uncertainties in our knowledge of the relevant molecular cross sections, and atmospheric transmission. A comparison of the PCL-derived water-vapour concentration and temperature profiles with routine radiosonde measurements from Detroit and Buffalo on 37 and 141 nights, respectively, was undertaken to provide this calibration. The calibration is then applied to the measurements and monthly mean-temperature and water-vapour profiles are determined.

  11. [CO2-gas exchange of mosses following water vapour uptake].

    PubMed

    Lange, O L

    1969-03-01

    The CO2-gas exchange of dry mosses which were exposed to air of high water vapour content has been followed. Some moss species behave as do lichens and aerophilic green algae: they are able to take up enough water vapour to make a rather high photosynthetic activity possible. Other species lack this ability. They need liquid water for reactivation of photosynthesis, as do poikilohydric ferns and phanerogams. In this respect too the mosses are located between the real thallophytes and the cormophytes. From this point of view they are useful objects for studying the relationships between water vapour reactivation, morphological organisation and ecological capability. PMID:24504355

  12. A review of water recovery by vapour permeation through membranes.

    PubMed

    Bolto, Brian; Hoang, Manh; Xie, Zongli

    2012-02-01

    In vapour permeation the feed is a vapour, not a liquid as in pervaporation. The process employs a polymeric membrane as a semi-permeable barrier between the feed side under high pressure and the permeate side under low pressure. Separation is achieved by the different degrees to which components are dissolved in and diffuse through the membrane, the system working according to a solution-diffusion mechanism. The materials used in the membrane depend upon the types of compounds being separated, so water transport is favoured by hydrophilic material, whether organic or inorganic. The process is used for the dehydration of natural gas and various organic solvents, notably alcohol as biofuel, as well as the removal of water from air and its recovery from waste steam. Waste steam can be found in almost every plant/factory where steam is used. It is frequently contaminated and cannot be reused. Discharging the spent steam to the atmosphere is a serious energy loss and environmental issue. Recycling the steam can significantly improve the overall energy efficiency of an industry, which is responsible for massive CO(2) emissions. Steam separation at high fluxes and temperatures has been accomplished with a composite poly(vinyl alcohol) membrane containing silica nanoparticles, and also, less efficiently, with an inorganic zeolite membrane. PMID:22100055

  13. The millennium water vapour drop in chemistry-climate model simulations

    NASA Astrophysics Data System (ADS)

    Brinkop, Sabine; Dameris, Martin; Jöckel, Patrick; Garny, Hella; Lossow, Stefan; Stiller, Gabriele

    2016-07-01

    This study investigates the abrupt and severe water vapour decline in the stratosphere beginning in the year 2000 (the "millennium water vapour drop") and other similarly strong stratospheric water vapour reductions by means of various simulations with the state-of-the-art Chemistry-Climate Model (CCM) EMAC (ECHAM/MESSy Atmospheric Chemistry Model). The model simulations differ with respect to the prescribed sea surface temperatures (SSTs) and whether nudging is applied or not. The CCM EMAC is able to most closely reproduce the signature and pattern of the water vapour drop in agreement with those derived from satellite observations if the model is nudged. Model results confirm that this extraordinary water vapour decline is particularly obvious in the tropical lower stratosphere and is related to a large decrease in cold point temperature. The drop signal propagates under dilution to the higher stratosphere and to the poles via the Brewer-Dobson circulation (BDC). We found that the driving forces for this significant decline in water vapour mixing ratios are tropical sea surface temperature (SST) changes due to a coincidence with a preceding strong El Niño-Southern Oscillation event (1997/1998) followed by a strong La Niña event (1999/2000) and supported by the change of the westerly to the easterly phase of the equatorial stratospheric quasi-biennial oscillation (QBO) in 2000. Correct (observed) SSTs are important for triggering the strong decline in water vapour. There are indications that, at least partly, SSTs contribute to the long period of low water vapour values from 2001 to 2006. For this period, the specific dynamical state of the atmosphere (overall atmospheric large-scale wind and temperature distribution) is important as well, as it causes the observed persistent low cold point temperatures. These are induced by a period of increased upwelling, which, however, has no corresponding pronounced signature in SSTs anomalies in the tropics. Our free

  14. Precipitable Water Vapour at the ESO Observatories: The Skill of the Forecasts

    NASA Astrophysics Data System (ADS)

    Sarazin, M.; Kerber, F.; De Breuck, C.

    2013-06-01

    Atmospheric precipitable water vapour (PWV) above an observatory is a crucial parameter for the success and quality of submillimetre and mid-infrared science observations. High precision water vapour radiometers are deployed at the ESO observatories on Paranal (VLT) and Chajnantor (APEX and ALMA), providing continuous high time-resolution measurements of PWV. These data have been used to compare the actual conditions with the forecast delivered by the publicly available Global Forecast System provided by the National Oceanographic and Atmospheric Administration. The quality of these predictions has now reached a level at which it can contribute to optimising science operations.

  15. Observations and recent evolution of stratospheric water vapour isotopologues derived from satellite measurements

    NASA Astrophysics Data System (ADS)

    Urban, Joachim; Jones, Ashley; Lossow, Stefan; Murtagh, Donal

    Water vapour, a strong greenhouse gas and source gas of the HOx family, plays an essential role for dynamics and chemistry of the middle atmosphere. Global measurements of isotopologues of water vapour have been made by the Odin Sub-Millimetre Radiometer (SMR) during nearly nine years since 2001. The long-term evolution of stratospheric water vapour has been studied by extending the historical satellite time-series from SAGE and HALOE, available until 2005, to present day by using data from Odin and other more recently launched satellites (Envisat, ACE). The recent evolution and variability of the water vapour isotopologues H2O-17, H2O-18, and HDO, as well as related trace gases and temperature has also been analysed and results of this study will be presented. Comparison and combination of various stratospheric water vapour time-series moreover provides a critical test of the quality of the different new satellite water vapour data sets. Odin is a Swedish-led satellite project funded jointly by Sweden (SNSB), Canada (CSA), Fin-land (TEKES), and France (CNES), with support by the 3rd party mission programme of the European Space Agency (ESA).

  16. Contributions of Organic Vapours to Atmospheric Nanoparticle Growth

    NASA Astrophysics Data System (ADS)

    Wang, L.; Xu, W.; Khalizov, A. F.; Zhang, R.

    2010-12-01

    Atmospheric aerosol particles alter radiative balance of the earth-atmosphere system, impact the regional and global climate, and pose negative effects on human health. Aerosol nucleation events have been frequently observed under various tropospheric conditions and account for a major fraction of the total aerosol population. Although a number of studies suggest that organics are involved in both new particle formation and their subsequent growth, the fundamental chemical processes responsible for organic vapours’ contribution remain poorly understood. This work will focus on laboratory studies on the role of various organic vapours in sulphuric acid nanoparticles growth. Sulfuric acid nanoparticles of 4-20 nm diameter size are generated from homogeneous binary nucleation of H2SO4 and H2O vapors in a laminar flow reactor. The growth factor of H2SO4 nanoparticles exposed to organics including methyglyoxal, ethanol, 1-butanol, 1-heptanol, 1-decanol, and cis-pinonic acid is measured using a nano-tandem differential mobility analyzer (nano-TDMA). Also studied is the potential synergistic effect in the presence of two or more organic vapours to which sulphuric acid nanoparticles are exposed. The chemical compositions of H2SO4 particles exposed to the organics are analyzed by a thermal desorption-ion drift-chemical ionization mass spectrometer (TD-ID-CIMS), and the spectroscopic evolution of functional groups in H2SO4 particles of ~40 nm diameter size, deposited on ZnSe crystal and subsequently exposed to organics, is studied using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FT-IR). The combined techniques are used to elucidate the key factors in controlling atmospheric nanoparticle growth.

  17. Ground-based near-infrared observations of water vapour in the Venus troposphere

    NASA Astrophysics Data System (ADS)

    Chamberlain, Sarah; Bailey, Jeremy; Crisp, David; Meadows, Vikki

    2013-01-01

    We present a study of water vapour in the Venus troposphere obtained by modelling specific water vapour absorption bands within the 1.18 μm window. We compare the results with the normal technique of obtaining the abundance by matching the peak of the 1.18 μm window. Ground-based infrared imaging spectroscopy of the night side of Venus was obtained with the Anglo-Australian Telescope and IRIS2 instrument with a spectral resolving power of R ˜ 2400. The spectra have been fitted with modelled spectra simulated using the radiative transfer model VSTAR. We find a best fit abundance of 31 ppmv (-6 +9 ppmv), which is in agreement with recent results by Bézard et al. (Bézard, B., Fedorova, A., Bertaux, J.-L., Rodin, A., Korablev, O. [2011]. Icarus, 216, 173-183) using VEX/SPICAV (R ˜ 1700) and contrary to prior results by Bézard et al. (Bézard, B., de Bergh, C., Crisp, D., Maillard, J.P. [1990]. Nature, 345, 508-511) of 44 ppmv (±9 ppmv) using VEX/VIRTIS-M (R ˜ 200) data analyses. Comparison studies are made between water vapour abundances determined from the peak of the 1.18 μm window and abundances determined from different water vapour absorption features within the near infrared window. We find that water vapour abundances determined over the peak of the 1. 18 μm window results in plots with less scatter than those of the individual water vapour features and that analyses conducted over some individual water vapour features are more sensitive to variation in water vapour than those over the peak of the 1. 18 μm window. No evidence for horizontal spatial variations across the night side of the disk are found within the limits of our data with the exception of a possible small decrease in water vapour from the equator to the north pole. We present spectral ratios that show water vapour absorption from within the lowest 4 km of the Venus atmosphere only, and discuss the possible existence of a decreasing water vapour concentration towards the surface.

  18. Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau

    NASA Astrophysics Data System (ADS)

    Casado, Mathieu; Landais, Amaelle; Masson-Delmotte, Valérie; Genthon, Christophe; Kerstel, Erik; Kassi, Samir; Arnaud, Laurent; Picard, Ghislain; Prie, Frederic; Cattani, Olivier; Steen-Larsen, Hans-Christian; Vignon, Etienne; Cermak, Peter

    2016-07-01

    Water stable isotopes in central Antarctic ice cores are critical to quantify past temperature changes. Accurate temperature reconstructions require one to understand the processes controlling surface snow isotopic composition. Isotopic fractionation processes occurring in the atmosphere and controlling snowfall isotopic composition are well understood theoretically and implemented in atmospheric models. However, post-deposition processes are poorly documented and understood. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum between surface water vapour, precipitation, surface snow and buried snow. Here, we target the isotopic composition of water vapour at Concordia Station, where the oldest EPICA Dome C ice cores have been retrieved. While snowfall and surface snow sampling is routinely performed, accurate measurements of surface water vapour are challenging in such cold and dry conditions. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces. Two infrared spectrometers have been deployed at Concordia, allowing continuous, in situ measurements for 1 month in December 2014-January 2015. Comparison of the results from infrared spectroscopy with laboratory measurements of discrete samples trapped using cryogenic sampling validates the relevance of the method to measure isotopic composition in dry conditions. We observe very large diurnal cycles in isotopic composition well correlated with temperature diurnal cycles. Identification of different behaviours of isotopic composition in the water vapour associated with turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction. Even if the vapour isotopic composition seems to be, at least part of the time, at equilibrium with the local snow, the slope of δD against δ18O prevents us from identifying a unique origin leading

  19. Atmospheric pressure vapour phase decomposition: a proof of principle.

    PubMed

    Cinosi, Amedeo; Andriollo, Nunzio; Tibaldi, Francesca; Monticelli, Damiano

    2012-11-15

    In the present work we demonstrated that the digestion of difficult matrices (high boiling petrochemical fractions and distillation bottoms) can be achieved by oxidation with nitric acid vapours at atmospheric pressure employing simple laboratory glassware. The application of this procedure as a digestion method prior to Total Reflection X-Ray Fluorescence (TXRF) is presented, although the employment of other detection techniques may be foreseen. The method ensured a fast, less than half an hour, treatment time and detection limits in the range 20-100 μg/kg for As, Bi, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, Zn, whereas higher values were obtained for Ba, Ca, K, P, Rh, Ti and V (0.3-3 mg/kg). The potentialities and limitations of this procedure were discussed: the application to a broad range of matrices may be foreseen. PMID:23158304

  20. A preliminary zonal mean climatology of water vapour in the stratosphere and mesosphere

    NASA Astrophysics Data System (ADS)

    Pumphrey, Hugh C.; Rind, D.; Russell, J. M.; Harries, J. E.

    The Microwave Limb Sounder on the UARS satellite measures water vapour concentration in the stratosphere and mesosphere. Water vapour profiles are retrieved from radiance measurements using a version of the optimal estimation algorithm. This requires an a priori profile which is obtained from a climatology. The MLS retrieval currently uses the standard UARS pre-launch climatology, which contains water vapour based on a 2-D model constrained to LIMS data in the stratosphere. This climatology has several defects which affect the ability of MLS to retrieve water vapour. This paper presents a new climatology constructed from the HALOE (HALogen Occultation Experiment) and SAGE II (Stratospheric Aerosol and Gas Experiment) data, which have become available recently. The new climatology is more realistic in several ways, particularly in the mesosphere and near the tropopause. It is proving to be an improvement as an a priori for MLS retrievals and might also have other uses. The paper will present the climatology, show how it was constructed, and compare it to the UARS pre-launch climatology and to various other data. As it stands, this climatology is not suitable for a reference atmosphere, but it is an improvement on CIRA part III in some way simply because it contains more accurate data and shows a number of new features. Suggestions are made for constructing an improved reference climatology for middle atmosphere water vapour.

  1. The millennium water vapour drop in chemistry-climate model simulations

    NASA Astrophysics Data System (ADS)

    Brinkop, S.; Dameris, M.; Jöckel, P.; Garny, H.; Lossow, S.; Stiller, G.

    2015-09-01

    This study investigates the abrupt and severe water vapour decline in the stratosphere beginning in year 2000 (the "millennium water vapour drop") and other similar stratospheric water vapour drops by means of various simulations with the state-of-the-art Chemistry-Climate Model (CCM) EMAC (ECHAM/MESSy Atmospheric Chemistry Model). The CCM EMAC is able to reproduce the signature and pattern of the water vapour disturbances in agreement with those derived from satellite observations. Model data confirm that this extraordinary water vapour decline is in particular obvious in the tropical lower stratosphere. The starting point of the severe water vapour drop is identified in the tropical lower stratosphere and the start date is found to be in the early days of 2000. We show that the driving forces for this significant drop in water vapour mixing ratios are tropical sea surface temperature changes due to a preceding strong El Niño-Southern Oscillation event (1997/98), which was followed by a La Niña and supported by the prevailing western phase of the equatorial stratospheric quasi-biennial oscillation (QBO) at that time. This constellation of ENSO and QBO obviously lead to the outstanding anomalies in meteorological quantities which are identified in the equatorial atmosphere: (a) a distinct warming (up to 1 K) of the tropical upper troposphere (200 to 120 hPa) beginning in mid-1997 and lasting for about one and a half years, (b) a strong warming (up to 2.5 K) of the tropical lower stratosphere (100 to 50 hPa), beginning in early 1999 and ending in early 2000, and (c) a significantly enhanced upwelling at the tropopause in the late 1990s and an obviously reduced upwelling around the year 2000 followed by a period of enhanced upwelling again. These dynamically induced changes are unambiguously connected to the stratospheric water vapour anomaly. Similarly strong water vapour reductions are also found in other years, and seem to be a~typical feature after strong

  2. Adsorption of n-alkane vapours at the water surface.

    PubMed

    Biscay, Frédéric; Ghoufi, Aziz; Malfreyt, Patrice

    2011-06-21

    Monte Carlo simulations are reported here to predict the surface tension of the liquid-vapour interface of water upon adsorption of alkane vapours (methane to hexane). A decrease of the surface tension has been established from n-pentane. A correlation has been evidenced between the decrease of the surface tension and the absence of specific arrangement at the water surface for n-pentane and n-hexane. The thermodynamic stability of the adsorption layer and the absence of film for longer alkanes have been checked through the calculation of a potential of mean force. This complements the work recently published [Ghoufi et al., Phys. Chem. Chem. Phys., 2010, 12, 5203] concerning the adsorption of methane at the water surface. The decrease of the surface tension has been interpreted in terms of the degree of hydrogen bonding of water molecules at the liquid-vapour interface upon adsorption. PMID:21584320

  3. Water vapour variability in the high-latitude upper troposphere - Part 2: Impact of volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Sioris, Christopher E.; Zou, Jason; McElroy, C. Thomas; Boone, Chris D.; Sheese, Patrick E.; Bernath, Peter F.

    2016-02-01

    The impact of volcanic eruptions on water vapour in the high-latitude upper troposphere is studied using deseasonalized time series based on observations by the Atmospheric Chemistry Experiment (ACE) water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS). The two eruptions with the greatest impact on the high-latitude upper troposphere during the time frame of this satellite-based remote sensing mission are chosen. The Puyehue-Cordón Caulle volcanic eruption in June 2011 was the most explosive in the past 24 years and is shown to be able to account for the observed (50 ± 12) % increase in water vapour in the southern high-latitude upper troposphere in July 2011 after a minor adjustment for the simultaneous influence of the Antarctic oscillation. Eyjafjallajökull erupted in the spring of 2010, increasing water vapour in the upper troposphere at northern high latitudes significantly for a period of ˜ 1 month. These findings imply that extratropical volcanic eruptions in windy environments can lead to significant perturbations to high-latitude upper tropospheric humidity mostly due to entrainment of lower tropospheric moisture by wind-blown plumes. The Puyehue-Cordón Caulle eruption must be taken into account to properly determine the magnitude of the trend in southern high-latitude upper tropospheric water vapour over the last decade.

  4. The water vapour radiometer of Paranal: homogeneity of precipitable water vapour from two years of operations

    NASA Astrophysics Data System (ADS)

    Kerber, Florian; Querel, Richard R.; Neureiter, Bianca

    2015-04-01

    A Low Humidity and Temperature Profiling (LHATPRO) microwave radiometer, manufactured by Radiometer Physics GmbH (RPG), is used to monitor sky conditions over ESO's Paranal observatory in support of VLT science operations. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ∼2.4 mm). The instrument consists of a humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared camera (∼10 μm) for cloud detection. We present a statistical analysis of the homogeneity of all-sky PWV using 24 months of PWV observations. The question we tried to address was whether PWV is homogeneous enough across the sky such that service mode observations with the VLT can routinely be conducted with a user-provided constraint for PWV measured at zenith. We find the PWV over Paranal to be remarkably homogeneous across the sky down to 27.5° elevation with a median variation of 0.07 mm (rms). The homogeneity is a function of the absolute PWV but the relative variation is fairly constant at 2 to 3% (rms). Such variations will not be a significant issue for analysis of astronomical data. Users at ESO can specify PWV - measured at zenith - as an ambient constraint in service mode to enable, for instance, very demanding observations in the infrared. We conclude that in general it will not be necessary to add another observing constraint for PWV homogeneity to ensure integrity of observations. For demanding observations requiring very low PWV, where the relative variation is higher, the optimum support could be provided by observing with the LHATPRO in the same line-of-sight simultaneously. Such a mode of operations has already been tested but will have to be justified in terms of scientific gain before implementation can be considered. We plan to extend our analysis of PWV variations covering a larger parameters space

  5. One year observation of water vapour isotopic composition at Ivittuut, Southern Greenland

    NASA Astrophysics Data System (ADS)

    Bonne, Jean-Louis; Masson-Delmotte, Valérie; Delmotte, Marc; Cattani, Olivier; Sodemann, Harald; Risi, Camille

    2013-04-01

    In September 2011, an automatic continuous water vapour isotopic composition monitoring instrument has been installed in the atmospheric station of Ivittuut (61.21° N, 48.17° W), southern Greenland. Precipitation has been regularly sampled on site at event to weekly scales and analysed in our laboratory for isotopic composition. Meteorological parameters (temperature, pressure, relative humidity, wind speed and direction) and atmospheric composition (CO2, CH4, Atmospheric Potential Oxygen) are also continuously monitored at Ivittuut. The meteorological context of our observation period will be assessed by comparison with the local climatology. The water vapour analyser is a Picarro Wavelength Scanned Cavity Ring-Down Spectrometer (WS-CRDS, model L2120i). It is automatically and regularly calibrated on the VSMOW scale using measurements of the isotopic composition of vaporized reference water standards using the Picarro Syringe Delivery Module (SDM). As measurements are sensitive to humidity level, an experimentally estimated calibration response function is used to correct our isotopic measurements. After data treatment, successive isotopic measurements of reference waters have a standard deviation of around 0.35 per mil for δ18O and 2.3 per mil for δD. Our instrumentation protocol and data quality control method will be presented, together with our one year δ18O, δD and d-excess measurements in water vapour and precipitation. The relationship between surface water vapour isotopic composition and precipitation isotopic composition will be investigated based on a distillation model. Specific difficulties linked to our low maintenance remote station will also be discussed. The processes responsible for the synoptic variability of Ivittuut water vapour isotopic composition will be investigated by comparing our observational dataset with (i) atmospheric back-trajectories and (ii) results from an isotopically-enabled atmospheric general circulation model (AGCM

  6. Variations in mid tropospheric carbon dioxide, temperature and water vapour using satellite data during 2003-2011

    NASA Astrophysics Data System (ADS)

    Dhaka, Surendra

    2016-07-01

    In this presentation global, hemispherical and regional (India) variations in carbon dioxide, temperature and water vapour and their association is analysed using mid-tropospheric (300-500 hPa) Atmospheric Infra-red Sounder (AIRS) data for a period of 9 years (2003-2011). Mid-tropospheric carbon dioxide is observed to rise from ~372.61 ppm to ~392.94 ppm over the globe and 373.38 ppm to 392.48 ppm over India from 2003 to 2011. However no significant changes are observed in mid-tropospheric temperature and water vapour variations for the same period. De-trended data of temperature and water vapour shows a high correlation between them, but no significant correlation was observed between temperature and carbon dioxide over the studied regions. The absence of immediate co-relation between temperature and carbon dioxide is the evidence that rise in carbon dioxide in the atmosphere will not imply more absorption over the earth surface. This may be explained because of the absorbing effect of carbon dioxide which is very small as compared to water vapour. The role of water vapour is reinforced because unlike carbon dioxide, water vapour in the atmosphere is changing in tune with temperature.

  7. All-sky homogeneity of precipitable water vapour over Paranal

    NASA Astrophysics Data System (ADS)

    Querel, Richard R.; Kerber, Florian

    2014-08-01

    A Low Humidity and Temperature Profiling (LHATPRO) microwave radiometer, manufactured by Radiometer Physics GmbH (RPG), is used to monitor sky conditions over ESO's Paranal observatory in support of VLT science operations. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.4 mm). The instrument consists of a humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared camera (~10 μm) for cloud detection. We present, for the first time, a statistical analysis of the homogeneity of all-sky PWV using 21 months of periodic (every 6 hours) all-sky scans from the radiometer. These data provide unique insight into the spatial and temporal variation of atmospheric conditions relevant for astronomical observations, particularly in the infrared. We find the PWV over Paranal to be remarkably homogeneous across the sky down to 27.5° elevation with a median variation of 0.32 mm (peak to valley) or 0.07 mm (rms). The homogeneity is a function of the absolute PWV but the relative variation is fairly constant at 10-15% (peak to valley) and 3% (rms). Such variations will not be a significant issue for analysis of astronomical data. Users at ESO can specify PWV - measured at zenith - as an ambient constraint in service mode to enable, for instance, very demanding observations in the infrared that can only be conducted during periods of very good atmospheric transmission and hence low PWV. We conclude that in general it will not be necessary to add another observing constraint for PWV homogeneity to ensure integrity of observations. For demanding observations requiring very low PWV, where the relative variation is higher, the optimum support could be provided by observing with the LHATPRO in the same line-of-sight simultaneously. Such a mode of operations has already been tested but will have to be

  8. Enhanced water vapour flow in silica microchannels and interdiffusive water vapour flow through anodic aluminium oxide (AAO) membranes

    NASA Astrophysics Data System (ADS)

    Lei, Wenwen; McKenzie, David R.

    2015-12-01

    Enhanced liquid water flows through carbon nanotubes reinvigorated the study of moisture permeation through membranes and micro- and nano-channels. The study of water vapour through micro-and nano-channels has been neglected even though water vapour is as important as liquid water for industry, especially for encapsulation of electronic devices. Here we measure moisture flow rates in silica microchannels and interdiffusive water vapour flows in anodic aluminium oxide (AAO) membrane channels for the first time. We construct theory for the flow rates of the dominant modes of water transport through four previously defined standard configurations and benchmark it against our new measurements. The findings show that measurements of leak behaviour made using other molecules, such as helium, are not reliable. Single phase water vapour flow is overestimated by a helium measurement, while Washburn or capillary flow is underestimated or for all channels when boundary slip applies, to an extent that depends on the slip length for the liquid phase flows.

  9. Water vapour variability in the high-latitude upper troposphere - Part 2: Impact of volcanic emissions

    NASA Astrophysics Data System (ADS)

    Sioris, C. E.; Zou, J.; McElroy, C. T.; Boone, C. D.; Sheese, P. E.; Bernath, P. F.

    2015-09-01

    The impact of volcanic eruptions on water vapour in the region of the high latitude tropopause is studied using deseasonalized time series based on observations by the Atmospheric Chemistry Experiment (ACE) water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS). The three eruptions with the greatest impact on the high latitude upper troposphere during the time frame of this satellite-based remote sensing mission are chosen. The Puyehue-Cordón Caulle volcanic eruption in June 2011 was the most explosive eruption in the past 24 years and resulted in an observed (50 ± 12) % increase in water vapour in the southern high-latitude upper troposphere in July 2011 that persisted into September 2011. A pair of Northern Hemisphere volcanoes, namely Eyjafjallajökull and Nabro, erupted in 2010 and 2011 respectively, increasing water vapour in the upper troposphere at northern high latitudes significantly for a period of ~ 3 months following each eruption. Both had a volcanic explosivity index of 4. Nabro led to a statistically significant increase of ~ 1 ppm in lower stratospheric (13.5-15.5 km) water vapour at northern high-latitudes (60-90° N) in September 2011, when the brunt of its plume arrived in the Arctic. These findings imply that steam emitted into the high-latitude, upper troposphere during volcanic eruptions must be taken into account to properly determine the magnitude of the trend in water vapour over the last decade.

  10. Impact of major volcanic eruptions on stratospheric water vapour

    NASA Astrophysics Data System (ADS)

    Löffler, M.; Brinkop, S.; Jöckel, P.

    2015-12-01

    Volcanic eruptions can have significant impact on the earth's weather and climate system. Besides the subsequent tropospheric changes also the stratosphere is influenced by large eruptions. Here changes in stratospheric water vapour after the two major volcanic eruptions of El Chichón in Mexico in 1982 and Mount Pinatubo on the Philippines in 1991 are investigated with chemistry-climate model simulations. This study is based on two simulations with specified dynamics of the EMAC model, performed within the Earth System Chemistry integrated Modelling (ESCiMo) project, of which only one includes the volcanic forcing through prescribed aerosol optical properties. The results show a significant increase in stratospheric water vapour after the eruptions, resulting from increased heating rates and the subsequent changes in stratospheric and tropopause temperatures in the tropics. The tropical vertical advection and the South Asian summer monsoon are identified as important sources for the additional water vapour in the stratosphere. Additionally, volcanic influences on the tropospheric water vapour and ENSO are evident.

  11. ESA DUE GlobVapour water vapor products: Validation

    NASA Astrophysics Data System (ADS)

    Schneider, Nadine; Schröder, Marc; Lindstrot, Ramus; Preusker, Rene; Stengel, Martin; ESA DUE GlobVapour Consortium

    2013-05-01

    The main objective of the European Space Agency (ESA) Data User Element (DUE) GlobVapour project was the development of multi-annual global water vapor data sets. Since water vapour is a key climate variable it is important to have a good understanding of its behavior in the climate system. The ESA DUE GlobVapour project provides water vapor data, including error estimates, based on carefully calibrated and inter-calibrated satellite radiances in response to user requirements for long time series satellite observations. ESA DUE GlobVapour total columnar water vapor (TCWV) products derived from GOME/SCIA/GOME-2 (1996-2008) and SSM/I+MERIS (2003-2008) have been validated for the mentioned period, using satellite-based (AIRS, ATOVS) and ground-based measurements (radiosondes and microwave radiometer). The validation results are discussed in the following. The technical specifications on bias (1 kg/m2 for SSMI+MERIS and 2 kg/m2 for GOME/SCIA/GOME-2) are generally met. For more information, documents and data download follow the link: www.globvapour.info.

  12. ESA DUE GlobVapour water vapor products: Validation

    SciTech Connect

    Schneider, Nadine; Schroeder, Marc; Stengel, Martin; Lindstrot, Ramus; Preusker, Rene; Collaboration: ESA DUE GlobVapour Consortium

    2013-05-10

    The main objective of the European Space Agency (ESA) Data User Element (DUE) GlobVapour project was the development of multi-annual global water vapor data sets. Since water vapour is a key climate variable it is important to have a good understanding of its behavior in the climate system. The ESA DUE GlobVapour project provides water vapor data, including error estimates, based on carefully calibrated and inter-calibrated satellite radiances in response to user requirements for long time series satellite observations. ESA DUE GlobVapour total columnar water vapor (TCWV) products derived from GOME/SCIA/GOME-2 (1996-2008) and SSM/I+MERIS (2003-2008) have been validated for the mentioned period, using satellite-based (AIRS, ATOVS) and ground-based measurements (radiosondes and microwave radiometer). The validation results are discussed in the following. The technical specifications on bias (1 kg/m{sup 2} for SSMI+MERIS and 2 kg/m{sup 2} for GOME/SCIA/GOME-2) are generally met. For more information, documents and data download follow the link: www.globvapour.info.

  13. Breakdown and dc discharge in low-pressure water vapour

    NASA Astrophysics Data System (ADS)

    Sivoš, J.; Škoro, N.; Marić, D.; Malović, G.; Petrović, Z. Lj

    2015-10-01

    In this paper we report studies of basic properties of breakdown, low-current Townsend discharge and high-current discharge regimes in water vapour. Paschen curves and the corresponding distributions of emission intensities at low current were recorded in the range of pd (pressure x electrode gap) from 0.1 to 10 Torrcm covering the region of Paschen minimum. From the experimental profiles we obtained effective ionization coefficient of water vapour for the E/N range 650 Td-7 kTd and fitted the results by using the extended Townsend analytical formula. Using the obtained ionization coefficient, we calculated the effective yield of secondary electrons from the copper cathode. Results of the measurements of Volt-Ampere characteristics in water vapour were presented together with the images of the axial structure of the discharge in a wide range of discharge currents for two pd values. Recorded profiles showed development of the spatial structure of the discharge in different operating regimes. We were able to identify conditions where processes induced by heavy particles, probably fast hydrogen atoms, are dominant in inducing emission from the discharge. Finally, standard scaling laws were tested for low current and glow discharges in water vapour.

  14. Land cover change and water vapour flows: learning from Australia.

    PubMed Central

    Gordon, Line; Dunlop, Michael; Foran, Barney

    2003-01-01

    Australia is faced with large-scale dryland salinization problems, largely as a consequence of the clearing of native vegetation for cropland and grassland. We estimate the change in continental water vapour flow (evapotranspiration) of Australia during the past 200 years. During this period there has been a substantial decrease in woody vegetation and a corresponding increase in croplands and grasslands. The shift in land use has caused a ca. 10% decrease in water vapour flows from the continent. This reduction corresponds to an annual freshwater flow of almost 340 km(3). The society-induced alteration of freshwater flows is estimated at more than 15 times the volume of run-off freshwater that is diverted and actively managed in the Australian society. These substantial water vapour flow alterations were previously not addressed in water management but are now causing serious impacts on the Australian society and local economies. Global and continental freshwater assessments and policy often neglects the interplay between freshwater flows and landscape dynamics. Freshwater issues on both regional and global levels must be rethought and the interplay between terrestrial ecosystems and freshwater better incorporated in freshwater and ecosystem management. PMID:14728792

  15. Mesoscale modelling of water vapour in the tropical UTLS: two case studies from the HIBISCUS campaign

    NASA Astrophysics Data System (ADS)

    Marécal, V.; Durry, G.; Longo, K.; Freitas, S.; Rivière, E. D.; Pirre, M.

    2007-03-01

    In this study, we evaluate the ability of the BRAMS (Brazilian Regional Atmospheric Modeling System) mesoscale model compared to ECMWF global analysis to simulate the observed vertical variations of water vapour in the tropical upper troposphere and lower stratosphere (UTLS). The observations are balloon-borne measurements of water vapour mixing ratio and temperature from micro-SDLA (Tunable Diode Laser Spectrometer) instrument. Data from two balloon flights performed during the 2004 HIBISCUS field campaign are used to compare with the mesoscale simulations and to the ECMWF analysis. The observations exhibit fine scale vertical structures of water vapour of a few hundred meters height. The ECMWF vertical resolution (~1 km) is too coarse to capture these vertical structures in the UTLS. With a vertical resolution similar to ECMWF, the mesoscale model performs better than ECMWF analysis for water vapour in the upper troposphere and similarly or slightly worse for temperature. The BRAMS model with 250 m vertical resolution is able to capture more of the observed fine scale vertical variations of water vapour compared to runs with a coarser vertical resolution. This is mainly related to: (i) the enhanced vertical resolution in the UTLS and (ii) to the more detailed microphysical parameterization providing ice supersaturations as in the observations. In near saturated or supersaturated layers, the mesoscale model predicted relative humidity with respect to ice saturation is close to observations provided that the temperature profile is realistic. For temperature, the ECMWF analysis gives good results partly attributed to data assimilation. The analysis of the mesoscale model results showed that the vertical variations of the water vapour profile depends on the dynamics in unsaturated layer while the microphysical processes play a major role in saturated/supersaturated layers. In the lower stratosphere, the ECMWF model and the BRAMS model give very similar water vapour

  16. Study and mitigation of calibration error sources in a water vapour Raman lidar

    NASA Astrophysics Data System (ADS)

    David, Leslie; Bock, Olivier; Bosser, Pierre; Thom, Christian; Pelon, Jacques

    2014-05-01

    The monitoring of water vapour throughout the atmosphere is important for many scientific applications (weather forecasting, climate research, calibration of GNSS altimetry measurements). Measuring water vapour remains a technical challenge because of its high variability in space and time. The major issues are achieving long-term stability (e.g., for climate trends monitoring) and high accuracy (e.g. for calibration/validation applications). LAREG and LOEMI at Institut National de l'Information Géographique et Forestière (IGN) have developed a mobile scanning water vapour Raman lidar in collaboration with LATMOS at CNRS. This system aims at providing high accuracy water vapour measurements throughout the troposphere for calibrating GNSS wet delay signals and thus improving vertical positioning. Current developments aim at improving the calibration method and long term stability of the system to allow the Raman lidar to be used as a reference instrument. The IGN-LATMOS lidar was deployed in the DEMEVAP (Development of Methodologies for Water Vapour Measurement) campaign that took place in 2011 at the Observatoire de Haute Provence. The goals of DEMEVAP were to inter-compare different water vapour sounding techniques (lidars, operational and research radiosondes, GPS,…) and to study various calibration methods for the Raman lidar. A significant decrease of the signals and of the calibration constants of the IGN-LATMOS Raman lidar has been noticed all along the campaign. This led us to study the likely sources of uncertainty and drifts in each part of the instrument: emission, reception and detection. We inventoried several error sources as well as instability sources. The impact of the temperature dependence of the Raman lines on the filter transmission or the fluorescence in the fibre, are examples of the error sources. We investigated each error source and each instability source (uncontrolled laser beam jitter, temporal fluctuations of the photomultiplier

  17. A new test method for measuring the water vapour permeability of fabrics

    NASA Astrophysics Data System (ADS)

    Huang, Jianhua; Qian, Xiaoming

    2007-09-01

    The water vapour permeability of textile fabrics is a critical determinant of wearer comfort. Existing test methods are either time consuming or require large amounts of material. A new test apparatus was developed for characterizing the water vapour permeability of fabrics. An aluminium cylinder covered with waterproof and vapour permeable PTFE laminate is used for generating water vapour source on one side of the sample. A dry nitrogen sweep gas stream is used to carry water vapour away. The calculation of the rate of water vapour transmission across the fabric is based on the measurement of the relative humidity of the outgoing nitrogen stream. This new measuring apparatus offers a short test time and calls for a small sample size. The comparison measurements show that the test results correlated well with those obtained from ISO 11092 and ASTM E96. Therefore, this test method provides a new technique to accurately and precisely characterize the water vapour transport properties of fabrics.

  18. The CM SAF ATOVS tropospheric water vapour and temperature data record: overview of methodology and evaluation

    NASA Astrophysics Data System (ADS)

    Courcoux, N.; Schröder, M.

    2015-02-01

    Recently, the reprocessed Advanced Television Infrared Observation Satellite (TIROS)-N Operational Vertical Sounder (ATOVS) tropospheric water vapour and temperature data record has been released by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility on Climate Monitoring (CM SAF). ATOVS observations from the National Oceanic and Atmospheric Agency (NOAA)-15 through NOAA-19 and EUMETSAT's Meteorological operational (Metop-A) satellites have been consistently reprocessed to generate 13 years (1999-2011) of global water vapour and temperature daily and monthly means with a spatial resolution of 90 km × 90 km. After pre-processing, an optimal estimation scheme has been applied to the observations to simultaneously infer temperature and water vapour profiles. In a post-processing step an objective interpolation method (Kriging) has been applied to allow for gap filling. The product suite includes total precipitable water vapour (TPW), layer integrated water vapour (LPW) and layer mean temperature for five tropospheric layers, as well as specific humidity and temperature at six tropospheric levels and is referenced under doi:10.5676/EUM_SAF_CM/WVT_ATOVS/V001. To our knowledge this is the first time that the ATOVS record (1998-now) has been consistently reprocessed (1999-2011) to retrieve water vapour and temperature products. TPW and LPW products were compared to corresponding products from the Global Climate Observing System (GCOS) Upper-Air Network (GUAN) radiosonde observations and from the Atmospheric InfraRed Sounder (AIRS) version 5 satellite data record. The TPW shows a good agreement with the GUAN radiosonde data: average bias and root mean square error (RMSE) are -0.2 and 3.3 kg m-2, respectively. The maximum absolute (relative) bias and RMSE values decrease (increase) strongly with height. While the RMSE relative to AIRS is

  19. Pan-derived isotopic composition of atmospheric vapour in a Mediterranean wetland (Rhône River Delta, France).

    PubMed

    Vallet-Coulomb, Christine; Cartapanis, Olivier; Radakovitch, Olivier; Sonzogni, Corinne; Pichaud, Marc

    2010-03-01

    A continuous record of atmospheric vapour isotopic composition (delta(A)) can be derived from the isotope mass balance of a water body submitted to natural evaporation. In this paper, we present preliminary results of the application of this method to a drying evaporation pan, located in a Mediterranean wetland, during a two-month summer period. Results seem consistent with few atmospheric vapour data based on the assumption of isotopic equilibrium with precipitation, but we observed a shift between pan-derived delta(A) and the composition of vapour samples collected by cold trapping. These results suggest that further investigations are necessary to evaluate the effect of diurnal variations of atmospheric conditions on the applicability of the pan-evaporation method, and on the representative of grab atmospheric samples. We also propose a sensitivity analysis for evaluating the impact of the different measured components on delta(A) calculation, and show an improvement in the method efficiency as the pan is drying. PMID:20099185

  20. Multi-sensor Calibration and Validation of the NASA-ALVICE and UWO-PCL NDACC Water Vapour Lidars

    NASA Astrophysics Data System (ADS)

    Wing, R.; Sica, R. J.; Argall, S.; Whiteman, D.; Walker, M.; Rodrigues, P.; McCullough, E. M.; Cadriola, M.

    2012-12-01

    The Purple Crow Lidar (PCL) has recently participated in a water vapour validation campaign with the NASA/GSFC Atmospheric Laboratory for Validation Inter-agency Collaboration and Education (ALVICE) Lidar. The purpose of this calibration exercise is to ensure that water vapour measurements, submitted to the Network for the Detection of Atmospheric Composition Change (NDACC) data base, are of sufficient quality for use in detecting long term changes in water vapour mixing ratio, particularly in the upper troposphere and lower stratosphere (UTLS). The field campaign took place at the University of Western Ontario Environmental Research Field Station, near London, Ontario, Canada, from May 23rd to June 10th 2012 and resulted in 57 hours of measurements taken over 12 clear nights. On each night a minimum of one RS92 radiosonde was launched. In addition, 3 cryogenic frost-point hygrometer (CFH) sondes were launched on clear nights over the course of the campaign. Measurements were obtained from near the surface up to ~20 km by both lidar systems, the radiosondes, and the CFH balloons. These measurements will be used to calibrate profiles of water vapour mixing ratio by the newly relocated PCL. Initial comparisons between the sondes and lidars will be presented as well as derived corrections for the retrieval of water vapour mixing ratio in both the troposphere and lower stratosphere.

  1. Water vapour jets inside the plume of gas leaving Enceladus.

    PubMed

    Hansen, C J; Esposito, L W; Stewart, A I F; Meinke, B; Wallis, B; Colwell, J E; Hendrix, A R; Larsen, K; Pryor, W; Tian, F

    2008-11-27

    A plume of water vapour escapes from fissures crossing the south polar region of the Saturnian moon Enceladus. Tidal deformation of a thin surface crust above an internal ocean could result in tensile and compressive stresses that would affect the width of the fissures; therefore, the quantity of water vapour released at different locations in Enceladus' eccentric orbit is a crucial measurement of tidal control of venting. Here we report observations of an occultation of a star by the plume on 24 October 2007 that revealed four high-density gas jets superimposed on the background plume. The gas jet positions coincide with those of dust jets reported elsewhere inside the plume. The maximum water column density in the plume is about twice the density reported earlier. The density ratio does not agree with predictions-we should have seen less water than was observed in 2005. The ratio of the jets' bulk vertical velocities to their thermal velocities is 1.5 +/- 0.2, which supports the hypothesis that the source of the plume is liquid water, with gas accelerated to supersonic velocity in nozzle-like channels. PMID:19037310

  2. A microwave satellite water vapour column retrieval for polar winter conditions

    NASA Astrophysics Data System (ADS)

    Perro, Christopher; Lesins, Glen; Duck, Thomas J.; Cadeddu, Maria

    2016-05-01

    A new microwave satellite water vapour retrieval for the polar winter atmosphere is presented. The retrieval builds on the work of Miao et al. (2001) and Melsheimer and Heygster (2008), employing auxiliary information for atmospheric conditions and numerical optimization. It was tested using simulated and actual measurements from the Microwave Humidity Sounder (MHS) satellite instruments. Ground truth was provided by the G-band vapour radiometer (GVR) at Barrow, Alaska. For water vapour columns less than 6 kg m-2, comparisons between the retrieval and GVR result in a root mean square (RMS) deviation of 0.39 kg m-2 and a systematic bias of 0.08 kg m-2. These results are compared with RMS deviations and biases at Barrow for the retrieval of Melsheimer and Heygster (2008), the AIRS and MIRS satellite data products, and the ERA-Interim, NCEP, JRA-55, and ASR reanalyses. When applied to MHS measurements, the new retrieval produces a smaller RMS deviation and bias than for the earlier retrieval and satellite data products. The RMS deviations for the new retrieval were comparable to those for the ERA-Interim, JRA-55, and ASR reanalyses; however, the MHS retrievals have much finer horizontal resolution (15 km at nadir) and reveal more structure. The new retrieval can be used to obtain pan-Arctic maps of water vapour columns of unprecedented quality. It may also be applied to measurements from the Special Sensor Microwave/Temperature 2 (SSM/T2), Advanced Microwave Sounding Unit B (AMSU-B), Special Sensor Microwave Imager/Sounder (SSMIS), Advanced Technology Microwave Sounder (ATMS), and Chinese MicroWave Humidity Sounder (MWHS) instruments.

  3. Intercomparison of in-situ and remote sensing δD signals in tropospheric water vapour

    NASA Astrophysics Data System (ADS)

    Schneider, Matthias; González, Yenny; Dyroff, Christoph; Christner, Emanuel; García, Omaira; Wiegele, Andreas; Andrey, Javier; Barthlott, Sabine; Blumenstock, Thomas; Guirado, Carmen; Hase, Frank; Ramos, Ramon; Rodríguez, Sergio; Sepúveda, Eliezer

    2014-05-01

    The main mission of the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) is the generation of a quasi-global tropospheric water vapour isototopologue dataset of a good and well-documented quality. We present a first empirical validation of MUSICA's remote sensing δD products (ground-based FTIR within NDACC, Network for the Detection of Atmospheric Composition Change, and space-based with IASI, Infrared Atmospheric Sounding Interferometer, flown on METOP). As reference we use in-situ measurements made on the island of Tenerife at two different altitudes (2370 and 3550 m a.s.l., using two Picarro L2120-i water isotopologue analyzers) and aboard an aircraft (between 200 and 6800 m a.s.l., using the homemade ISOWAT instrument).

  4. Comparison of independent integrated water vapour estimates from GPS and sun photometer measurements and a meteorological model

    NASA Astrophysics Data System (ADS)

    Pugnaghi, S.; Boccolari, M.; Fazlagić, S.; Pacione, R.; Santangelo, R.; Vedel, H.; Vespe, F.

    Measurements using the Global Positioning System (GPS) are affected by the so-called tropospheric delay. Of this, the so-called wet delay is related mainly to the amount of water vapour along the path of the GPS signal through the troposphere. Precise knowledge of the abundance of water vapour, in space and time, is important for meteorology, both in forecasting and now-casting as well as in climate studies. Both because water vapour is the predecessor of precipitation, which is a forecast product, and because a very significant fraction of the energy released to the atmosphere comes from latent heat via water vapour. Despite the high variability of water vapour compared to other meteorological fields, like pressure and wind, water vapour observations are scarce; wherefore additional measurements of water vapour are expected to benefit meteorology. Water vapour is crucial for the development of the small scale, but sometimes very severe,precipitation events which are often seen at mid latitudes, and which are very hard to predict. In this work a comparison between radiometric (sun photometer) and GPS integrated water vapour (IWV) is presented. A sun photometer has been installed at the ENEA (Ente per le Nuove tecnologie, l'Energia e l'Ambiente) base of Lampedusa Island. The sun photometer is quite close (less then 4 km) to an ASI (Agenzia Spaziale Italiana) GPS permanent receiver. In Venezia an ASI GPS permanent receiver is collocated with another sun photometer. Both sun photometers are installed as part of the AERONET (AErosol and RObotic NETwork) program. A long record of sun photometric measurements, GPS data, and meteorological data is available for the Venezia site. A shorter record (summer period of the year 2000) is available for the station at Lampedusa. The comparison among the three different methods for water vapour delay estimation is presented. We find that the GPS and sun photometric data are better correlated (S.D. about 10 mm for the wet delay

  5. Validation of water vapour transport in the tropical tropopause region in coupled Chemistry Climate Models

    NASA Astrophysics Data System (ADS)

    Kremser, S.; Rex, M.; Langematz, U.; Dameris, M.; Wohltmann, I.

    2008-06-01

    In this study backward trajectories from the tropical lower stratosphere were calculated for the Northern Hemisphere (NH) winters 1995-1996, 1997-1998 (El Niño) and 1998-1999 (La Niña) and summers 1996, 1997 and 1999 using both ERA-40 reanalysis data of the European Centre for Medium-Range Weather Forecast (ECMWF) and coupled chemistry climate model (CCM) data. The calculated trajectories were analyzed to determine the distribution of points where individual air masses encounter the minimum temperature and thus minimum water vapour mixing ratio during their ascent through the tropical tropopause layer (TTL) into the stratosphere. The geographical distribution of these dehydration points and the local conditions there determine the overall water vapour entry into the stratosphere. Results of two CCMs are presented: the ECHAM4.L39(DLR)/CHEM (hereafter: E39/C) from the German Aerospace Center (DLR) and the Freie Universität Berlin Climate Middle Atmosphere Model with interactive chemistry (hereafter: FUB-CMAM-CHEM). In the FUB-CMAM-CHEM model the minimum temperatures are overestimated by about 7 K in Northern Hemisphere (NH) winter as well as in NH summer, resulting in too high water vapour entry values compared to ERA-40. However, the geographical distribution of dehydration points is fairly reproduced for NH winter 1995-1996 and 1998-1999 and in all boreal summers. The distribution of dehydration points suggests an influence of the Indian monsoon upon the water vapour transport. The E39/C model displays a temperature bias of about +3 K. Hence, the minimum water vapour mixing ratios are higher relative to ERA-40. The geographical distribution of dehydration points is satisfactory in NH winter 1995-1996 and 1997-1998 with respect to ERA-40. The distribution is not reproduced for the NH winter 1998-1999 (La Niña event) compared to ERA-40. There is excessive mass flux through warm regions e.g. Africa, leading to excessive water vapour flux in the NH winter and

  6. Phase correction of VLBI with water vapour radiometry

    NASA Astrophysics Data System (ADS)

    Roy, Alan; Rottmann, H.; Teuber, U.; Keller, R.

    We demonstrate phase correction of 3-mm VLBI observations using the scanning 18-GHz to 26GHz water vapour radiometer (WVR) at Effelsberg and we demonstrate an absolute accuracy of 15-mm in zenith path delay by comparing with GPS and radiosondes. This accuracy should provide significant improvement in astrometric phase-referencing observations. It is not good enough for geodetic VLBI to replace the tropospheric delay estimation but could be used to remove short-term path-length fluctuations and so improve the geodetic observables. We discuss lessons learned and opportunities for further improvement.

  7. Detecting vapour bubbles in simulations of metastable water

    SciTech Connect

    González, Miguel A.; Abascal, Jose L. F.; Valeriani, Chantal E-mail: cvaleriani@quim.ucm.es; Menzl, Georg; Geiger, Philipp; Dellago, Christoph E-mail: cvaleriani@quim.ucm.es; Aragones, Juan L.; Caupin, Frederic

    2014-11-14

    The investigation of cavitation in metastable liquids with molecular simulations requires an appropriate definition of the volume of the vapour bubble forming within the metastable liquid phase. Commonly used approaches for bubble detection exhibit two significant flaws: first, when applied to water they often identify the voids within the hydrogen bond network as bubbles thus masking the signature of emerging bubbles and, second, they lack thermodynamic consistency. Here, we present two grid-based methods, the M-method and the V-method, to detect bubbles in metastable water specifically designed to address these shortcomings. The M-method incorporates information about neighbouring grid cells to distinguish between liquid- and vapour-like cells, which allows for a very sensitive detection of small bubbles and high spatial resolution of the detected bubbles. The V-method is calibrated such that its estimates for the bubble volume correspond to the average change in system volume and are thus thermodynamically consistent. Both methods are computationally inexpensive such that they can be used in molecular dynamics and Monte Carlo simulations of cavitation. We illustrate them by computing the free energy barrier and the size of the critical bubble for cavitation in water at negative pressure.

  8. Detecting vapour bubbles in simulations of metastable water

    NASA Astrophysics Data System (ADS)

    González, Miguel A.; Menzl, Georg; Aragones, Juan L.; Geiger, Philipp; Caupin, Frederic; Abascal, Jose L. F.; Dellago, Christoph; Valeriani, Chantal

    2014-11-01

    The investigation of cavitation in metastable liquids with molecular simulations requires an appropriate definition of the volume of the vapour bubble forming within the metastable liquid phase. Commonly used approaches for bubble detection exhibit two significant flaws: first, when applied to water they often identify the voids within the hydrogen bond network as bubbles thus masking the signature of emerging bubbles and, second, they lack thermodynamic consistency. Here, we present two grid-based methods, the M-method and the V-method, to detect bubbles in metastable water specifically designed to address these shortcomings. The M-method incorporates information about neighbouring grid cells to distinguish between liquid- and vapour-like cells, which allows for a very sensitive detection of small bubbles and high spatial resolution of the detected bubbles. The V-method is calibrated such that its estimates for the bubble volume correspond to the average change in system volume and are thus thermodynamically consistent. Both methods are computationally inexpensive such that they can be used in molecular dynamics and Monte Carlo simulations of cavitation. We illustrate them by computing the free energy barrier and the size of the critical bubble for cavitation in water at negative pressure.

  9. The seasonal cycle of water vapour on Mars from assimilation of Thermal Emission Spectrometer data

    NASA Astrophysics Data System (ADS)

    Steele, Liam J.; Lewis, Stephen R.; Patel, Manish R.; Montmessin, Franck; Forget, François; Smith, Michael D.

    2014-07-01

    We present for the first time an assimilation of Thermal Emission Spectrometer (TES) water vapour column data into a Mars global climate model (MGCM). We discuss the seasonal cycle of water vapour, the processes responsible for the observed water vapour distribution, and the cross-hemispheric water transport. The assimilation scheme is shown to be robust in producing consistent reanalyses, and the global water vapour column error is reduced to around 2-4 pr μm depending on season. Wave activity is shown to play an important role in the water vapour distribution, with topographically steered flows around the Hellas and Argyre basins acting to increase transport in these regions in all seasons. At high northern latitudes, zonal wavenumber 1 and 2 stationary waves during northern summer are responsible for spreading the sublimed water vapour away from the pole. Transport by the zonal wavenumber 2 waves occurs primarily to the west of Tharsis and Arabia Terra and, combined with the effects of western boundary currents, this leads to peak water vapour column abundances here as observed by numerous spacecraft. A net transport of water to the northern hemisphere over the course of one Mars year is calculated, primarily because of the large northwards flux of water vapour which occurs during the local dust storm around LS=240-260°. Finally, outlying frost deposits that surround the north polar cap are shown to be important in creating the peak water vapour column abundances observed during northern summer.

  10. The Seasonal Cycle of Water Vapour on Mars from Assimilation of Thermal Emission Spectrometer Data

    NASA Technical Reports Server (NTRS)

    Steele, Liam J.; Lewis, Stephen R.; Patel, Manish R.; Montmessin, Franck; Forget, Francois; Smith, Michael D.

    2014-01-01

    We present for the first time an assimilation of Thermal Emission Spectrometer (TES) water vapour column data into a Mars global climate model (MGCM). We discuss the seasonal cycle of water vapour, the processes responsible for the observed water vapour distribution, and the cross-hemispheric water transport. The assimilation scheme is shown to be robust in producing consistent reanalyses, and the global water vapour column error is reduced to around 2-4 pr micron depending on season. Wave activity is shown to play an important role in the water vapour distribution, with topographically steered flows around the Hellas and Argyre basins acting to increase transport in these regions in all seasons. At high northern latitudes, zonal wavenumber 1 and 2 stationary waves during northern summer are responsible for spreading the sublimed water vapour away from the pole. Transport by the zonal wavenumber 2 waves occurs primarily to the west of Tharsis and Arabia Terra and, combined with the effects of western boundary currents, this leads to peak water vapour column abundances here as observed by numerous spacecraft. A net transport of water to the northern hemisphere over the course of one Mars year is calculated, primarily because of the large northwards flux of water vapour which occurs during the local dust storm around L(sub S) = 240-260deg. Finally, outlying frost deposits that surround the north polar cap are shown to be important in creating the peak water vapour column abundances observed during northern summer.

  11. Southern Greenland water vapour isotopic composition at the crossroads of Atlantic and Arctic moisture

    NASA Astrophysics Data System (ADS)

    Bonne, J. L.; Steen-Larsen, H. C.; Risi, C. M.; Werner, M.; Sodemann, H.; Lacour, J. L.; Fettweis, X.; Cesana, G.; Delmotte, M.; Cattani, O.; Clerbaux, C.; Sveinbjörnsdottir, A. E.; Masson-Delmotte, V.

    2014-12-01

    , depicting the northward propagation of an isotopic signal inherited from the meteorological conditions during evaporation. Overall, our observations provide valuable information for interpreting Greenland ice core records as well as for evaluating water vapour isotopic simulations in atmospheric models.

  12. Seasonally-Active Water on Mars: Vapour, Ice, Adsorbate, and the Possibility of Liquid

    NASA Astrophysics Data System (ADS)

    Richardson, M. I.

    2002-12-01

    Seasonally-active water can be defined to include any water reservoir that communicates with other reservoirs on time scales of a year or shorter. It is the interaction of these water reservoirs, under the influence of varying solar radiation and in conjunction with surface and atmospheric temperatures, that determines the phase-stability field for water at the surface, and the distribution of water in various forms below, on, and above the surface. The atmosphere is the critical, dynamical link in this cycling system, and also (fortunately) one of the easiest to observe. Viking and Mars Global Surveyor observations paint a strongly asymmetric picture of the global seasonal water cycle, tied proximately to planetary eccentricity, and the existence of residual ice caps of different composition at the two poles. The northern summer experiences the largest water vapour columns, and is associated with sublimation from the northern residual water ice cap. The southern summer residual carbon dioxide ice cap is cold trap for water. Asymmetry in the water cycle is an unsolved problem. Possible solutions may involve the current timing of perihelion (the water cap resides at the pole experiencing the longer but cooler summer), the trapping of water ice in the northern hemisphere by tropical water ice clouds, and the bias in the annual-average, zonal-mean atmospheric circulation resulting from the zonal-mean difference in the elevation of the northern and southern hemispheres. Adsorbed and frozen water have proven harder to constrain. Recent Odyssey Gamma Ray Spectrometer results suggest substantial ground ice in the mid- and high-latitudes, but this water is likely below the seasonal skin depth for two reasons: the GRS results are best fit with such a model, and GCM models of the water cycle produce dramatically unrealistic atmospheric vapour distributions when such a very near surface, GRS-like distribution is initialized - ultimately removing the water to the northern and

  13. Airborne and satellite remote sensing of the mid-infrared water vapour continuum.

    PubMed

    Newman, Stuart M; Green, Paul D; Ptashnik, Igor V; Gardiner, Tom D; Coleman, Marc D; McPheat, Robert A; Smith, Kevin M

    2012-06-13

    Remote sensing of the atmosphere from space plays an increasingly important role in weather forecasting. Exploiting observations from the latest generation of weather satellites relies on an accurate knowledge of fundamental spectroscopy, including the water vapour continuum absorption. Field campaigns involving the Facility for Airborne Atmospheric Measurements research aircraft have collected a comprehensive dataset, comprising remotely sensed infrared radiance observations collocated with accurate measurements of the temperature and humidity structure of the atmosphere. These field measurements have been used to validate the strength of the infrared water vapour continuum in comparison with the latest laboratory measurements. The recent substantial changes to self-continuum coefficients in the widely used MT_CKD (Mlawer-Tobin-Clough-Kneizys-Davies) model between 2400 and 3200 cm(-1) are shown to be appropriate and in agreement with field measurements. Results for the foreign continuum in the 1300-2000 cm(-1) band suggest a weak temperature dependence that is not currently included in atmospheric models. A one-dimensional variational retrieval experiment is performed that shows a small positive benefit from using new laboratory-derived continuum coefficients for humidity retrievals. PMID:22547235

  14. Quantification of uncertainties of water vapour column retrievals using future instruments

    NASA Astrophysics Data System (ADS)

    Diedrich, H.; Preusker, R.; Lindstrot, R.; Fischer, J.

    2012-09-01

    This study presents a quantification of uncertainties of water vapour retrievals based on near infrared measurements of upcoming instruments. The concepts of three scheduled spectrometer were taken into account: OLCI (Ocean and Land Color Instrument) on Sentinel-3, METimage on MetOp (Meteorological Operational Satellite) and FCI (Flexible Combined Imager) on MTG (Meteosat Third Generation). Optimal estimation theory was used to estimate the error of an hypothetical total water vapour column retrieval for 27 different atmospheric cases. The errors range from 100% in very dry cases to 2% in humid cases with a very high surface albedo. Generally the absolute uncertainties increase with higher water vapour column content due to H2O-saturation and decrease with a brighter surface albedo. Uncertainties increase with higher aerosol optical thickness, apart from very dark cases. Overall the METimage channel setting enables the most accurate retrievals. The retrieval using the MTG-FCI buildup has the highest uncertainties apart from very bright cases. A retrieval using two absorption channels increases the accuracy, in some cases by one order of magnitude, in comparison to a retrieval using just one absorption channel. On the other hand, a retrieval using three absorption channels has no significant advantage over a two-absorption channel retrieval. Furthermore, the optimal position of the absorption channels was determined using the concept of the "information content". For a single channel retrieval a channel at 900 or 915 nm has the highest mean information contents over all cases. The second absorption channel is ideally weakly correlated with the first one, thus positioned at 935 nm, in a region with stronger water vapour absorption.

  15. Quantification of uncertainties of water vapour column retrievals using future instruments

    NASA Astrophysics Data System (ADS)

    Diedrich, H.; Preusker, R.; Lindstrot, R.; Fischer, J.

    2013-02-01

    This study presents a quantification of uncertainties of total column water vapour retrievals based on simulated near-infrared measurements of upcoming instruments. The concepts of three scheduled spectrometers were taken into account: OLCI (Ocean and Land Color Instrument) on Sentinel-3, METimage on an EPS-SG (EUMETSAT Polar System - Second Generation) satellite and FCI (Flexible Combined Imager) on MTG (Meteosat Third Generation). Optimal estimation theory was used to estimate the error of a hypothetical total water vapour column retrieval for 27 different atmospheric cases. The errors range from 100% in very dry cases to 2% in humid cases with a very high surface albedo. Generally, the absolute uncertainties increase with higher water vapour column content due to H2O-saturation and decrease with a brighter surface albedo. Uncertainties increase with higher aerosol optical thickness, apart from very dark cases. Overall, the METimage channel setting enables the most accurate retrievals. The retrieval using the MTG-FCI build-up has the highest uncertainties apart from very bright cases. On the one hand, a retrieval using two absorption channels increases the accuracy, in some cases by one order of magnitude, in comparison to a retrieval using just one absorption channel. On the other hand, a retrieval using three absorption channels has no significant advantage over a two-absorption channel retrieval. Furthermore, the optimal position of the absorption channels was determined using the concept of the "information content". For a single channel retrieval, a channel at 900 or 915 nm has the highest mean information content over all cases. The second absorption channel is ideally weakly correlated with the first one, and therefore positioned at 935 nm, in a region with stronger water vapour absorption.

  16. UTLS water vapour from SCIAMACHY limb measurementsV3.01 (2002-2012)

    NASA Astrophysics Data System (ADS)

    Weigel, K.; Rozanov, A.; Azam, F.; Bramstedt, K.; Damadeo, R.; Eichmann, K.-U.; Gebhardt, C.; Hurst, D.; Kraemer, M.; Lossow, S.; Read, W.; Spelten, N.; Stiller, G. P.; Walker, K. A.; Weber, M.; Bovensmann, H.; Burrows, J. P.

    2016-01-01

    The SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) aboard the Envisat satellite provided measurements from August 2002 until April 2012. SCIAMACHY measured the scattered or direct sunlight using different observation geometries. The limb viewing geometry allows the retrieval of water vapour at about 10-25 km height from the near-infrared spectral range (1353-1410 nm). These data cover the upper troposphere and lower stratosphere (UTLS), a region in the atmosphere which is of special interest for a variety of dynamical and chemical processes as well as for the radiative forcing. Here, the latest data version of water vapour (V3.01) from SCIAMACHY limb measurements is presented and validated by comparisons with data sets from other satellite and in situ measurements. Considering retrieval tests and the results of these comparisons, the V3.01 data are reliable from about 11 to 23 km and the best results are found in the middle of the profiles between about 14 and 20 km. Above 20 km in the extra tropics V3.01 is drier than all other data sets. Additionally, for altitudes above about 19 km, the vertical resolution of the retrieved profile is not sufficient to resolve signals with a short vertical structure like the tape recorder. Below 14 km, SCIAMACHY water vapour V3.01 is wetter than most collocated data sets, but the high variability of water vapour in the troposphere complicates the comparison. For 14-20 km height, the expected errors from the retrieval and simulations and the mean differences to collocated data sets are usually smaller than 10 % when the resolution of the SCIAMACHY data is taken into account. In general, the temporal changes agree well with collocated data sets except for the Northern Hemisphere extratropical stratosphere, where larger differences are observed. This indicates a possible drift in V3.01 most probably caused by the incomplete treatment of volcanic aerosols in the retrieval. In all other regions a

  17. Infra-red measurements of stratospheric composition. I - The balloon instrument and water vapour measurements

    NASA Technical Reports Server (NTRS)

    Chaloner, C. P.; Drummond, J. R.; Houghton, J. T.; Roscoe, H. K.; Jarnot, R. F.

    1978-01-01

    The design and construction of a balloon-borne instrument for remote-sensing of stratospheric composition is described. Thermal emission from the constituents is detected and the spectral selectivity of the instrument is tailored to a specific gas by the use of a cell of the same gas in the optical path of the radiometer. The pressure of the gas in the cell is cycled and the resultant transmission function is shown to be highly selective to radiation from the same gas in the atmosphere. The first flight of the instrument and the retrieval of a water vapour profile in the range 15-40 km is described.

  18. Absolute high spectral resolution measurements of surface solar radiation for detection of water vapour continuum absorption.

    PubMed

    Gardiner, T D; Coleman, M; Browning, H; Tallis, L; Ptashnik, I V; Shine, K P

    2012-06-13

    Solar-pointing Fourier transform infrared (FTIR) spectroscopy offers the capability to measure both the fine scale and broadband spectral structure of atmospheric transmission simultaneously across wide spectral regions. It is therefore suited to the study of both water vapour monomer and continuum absorption behaviours. However, in order to properly address this issue, it is necessary to radiatively calibrate the FTIR instrument response. A solar-pointing high-resolution FTIR spectrometer was deployed as part of the 'Continuum Absorption by Visible and Infrared radiation and its Atmospheric Relevance' (CAVIAR) consortium project. This paper describes the radiative calibration process using an ultra-high-temperature blackbody and the consideration of the related influence factors. The result is a radiatively calibrated measurement of the solar irradiation at the ground across the IR region from 2000 to 10 000 cm(-1) with an uncertainty of between 3.3 and 5.9 per cent. This measurement is shown to be in good general agreement with a radiative-transfer model. The results from the CAVIAR field measurements are being used in ongoing studies of atmospheric absorbers, in particular the water vapour continuum. PMID:22547234

  19. The millennium water vapour drop in the stratosphere in chemistry-climate model simulations

    NASA Astrophysics Data System (ADS)

    Brinkop, Sabine; Dameris, Martin; Joeckel, Patrick; Garny, Hella; Lossow, Stefan; Stiller, Gabriele

    2015-04-01

    This study investigates the millennium water vapour drop, the abrupt and severe water vapour decline in the stratosphere beginning in year 2000, by means of various simulations using the Chemistry-Climate Model (CCM) EMAC. Since the beginning 1980s, balloon borne stratospheric water vapour measurements and corresponding satellite measurements starting in the early 1990s indicated a long-term steady increase of water vapour concentrations. However, the multi-year data sets also show significant fluctuations on different time scales. In the year 2000, an extraordinary sudden drop of stratospheric water vapour concentration has been observed followed by persistent low values for several years. Solomon et al. (2010) showed that this drop slowed down the rate of increase in global surface temperature over the following decade by about 25%. So far, the stratospheric water vapour variations observed by satellite from 1992 to 2012 are not reproduced by CCM simulations forced by observed changes in sea surface temperatures, greenhouse gases and ozone-depleting substances (Gettelman et al., 2010, Randel and Jensen, 2013). However, the CCM EMAC is able to reproduce the signature and pattern of the water vapour disturbances in agreement with those derived from observations. In this paper we present results of a hierarchy of simulations with the CCM EMAC, demonstrating that it is possible to retrace the observed water vapour fluctuations in the stratosphere (incl. the millennium drop), if suitable inner and outer boundary conditions are applied.

  20. The effects of urbanization on water vapour pressure in a semi-arid climate

    NASA Astrophysics Data System (ADS)

    Çiçek, I.; Türkoğlu, N.

    2009-01-01

    This study evaluates data from Aksaray, a medium sized urban city, and Cihanbeyli, a small town in Turkey, in order to show the effects of urbanization on water vapour pressure. Data taken at 07:00, 14:00 and 21:00 h and daily means were analyzed to identify the daily changes in water vapour pressure and temperatures. In Aksaray, positive urban heat island values were observed in all months except during afternoon hours. At all observation times during winter, weak water vapour pressure differences were recorded. During summer, on the other hand, positive water vapour differences were seen during afternoon and evening hours. A more humid city at afternoon hours is not typical of other mid-latitude countries. This is thought to be mainly related to the semi-arid climatic conditions in the area. Water vapour differences were seen to have a decreasing trend except during afternoon hours. As for temperature differences, an increase was seen during morning and evening hours, while a decrease was seen during afternoon hours and in daily means. A new trend was observed to start after the 1980s in both sets of data, which coincides with rapid population growth in Aksaray. Negative correlations were seen between water vapour pressure and temperature differences. No increase in water vapour pressure due to urbanization was observed in Aksaray. The decreasing evapotranspiration and the urban geometry appear to be the most influential factors in determining the water vapour pressure in Aksaray.

  1. Condensation of water vapour on moss-dominated biological soil crust, NW China

    NASA Astrophysics Data System (ADS)

    Wang, Xin-Ping; Pan, Yan-Xia; Hu, Rui; Zhang, Ya-Feng; Zhang, Hao

    2014-03-01

    Characteristics of water vapour condensation, including the onset, duration, and amount of water vapour condensation on moss-dominated biological soil crust (BSC) and dune sand were studied under simulated conditions with varying air temperature and relative humidity. The simulations were performed in a plant growth chamber using an electronic balance recording the weight of condensation. There was a positive linear correlation between the water vapour condensation and relative humidity while the mean temperature was negatively linearly related to amounts of water vapour condensation for both soil surfaces. The amount of water vapour condensation on BSC and dune sand can be described by the difference between air temperature and dew point with an exponential function, indicating that when the difference of air temperature and dew point exceeds a value of 35.3◦C, there will be zero water vapour condensed on BSC. In contrast, when the difference of air temperature and dew point exceeds a value of 20.4◦C, the water vapour condensation will be zero for dune sand. In general, when the air is fully saturated with water and the dew point is equal to the current air temperature, the water vapour condensed on BSC attained its maximum value of 0.398 mm, whereas it was 0.058 mm for dune sand. In comparison, water vapour condensed on BSC was at a relatively high temperature and low relative humidity, while we did not detect water vapour condensation on the dune sand under the similar conditions. Physical and chemical analyses of the samples pointed to a greater porosity, high content of fine particles, and high salinity for BSC compared to the dune sand. These results highlight that soil physicochemical properties are the likely factors influencing the mechanism of water vapour condensation under specific meteorological conditions, as onset was earlier and the duration was longer for water vapour condensation on BSC in comparison with that of dune sand. This contributed to

  2. Atmospheric pressure chemical vapour deposition of vanadium oxides

    NASA Astrophysics Data System (ADS)

    Manning, Troy Darrell

    The APCVD of vanadium(IV) oxide thin films from halide precursors was investigated. It was found that the phase of vanadium oxide obtained could be controlled by the reactor temperature and precursor ratio. For vanadium(IV) chloride and water, reactor temperatures > 550 °C and an excess of water over VCI4 was required to produce VO2 thin films. For vanadium(V) oxytrichloride and water, reactor temperatures > 550 °C and an excess of water over VOCI3 also produced VO2 but required low total gas flow rates (< 1 L min 1) for complete coverage of the substrate. Vanadium(IV) oxide thin films doped with metal ions (W, Cr, Nb, Ti, Mo or Sn) were also prepared by the APCVD process in order to reduce the thermochromic transition temperature (TC) from 68 °C for the undoped material to < 30 °C. The most successful dopant was tungsten, introduced into the VOCl3, and water system as WCI6, which lowered T to 5 °C for a 3 atom% tungsten doped thin film. Tungsten (VI) ethoxide was introduced into the VCI4 and water system and reduced TC, of VO2, to 42 °C for a 1 atom% tungsten doped thin film. Chromium, introduced as CrCO2Cl2, formed a chromium vanadium oxide that did not display any thermochromic properties. Niobium, introduced as NbCl5 into the VOCl3 system, reduced TC of VO2, but the amount of niobium introduced could not be easily controlled. Molybdenum, introduced as MoCI5, also reduced TC of VO2, but the form of the molybdenum appeared to be different from that required for complete control of TC, Titanium, introduced as TiCl4, produced phase segregated films of VO2 and TiO2, with interesting multifunctional properties and a reduced TC. Tin, introduced as SnCl4, also formed a phase segregated material of VO2, and SnO2, with a slightly reduced TC.

  3. Recent advances in measurement of the water vapour continuum in the far-infrared spectral region.

    PubMed

    Green, Paul D; Newman, Stuart M; Beeby, Ralph J; Murray, Jonathan E; Pickering, Juliet C; Harries, John E

    2012-06-13

    We present a new derivation of the foreign-broadened water vapour continuum in the far-infrared (far-IR) pure rotation band between 24 μm and 120 μm (85-420 cm(-1)) from field data collected in flight campaigns of the Continuum Absorption by Visible and IR radiation and Atmospheric Relevance (CAVIAR) project with Imperial College's Tropospheric Airborne Fourier Transform Spectrometer (TAFTS) far-IR spectro-radiometer instrument onboard the Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft; and compare this new derivation with those recently published in the literature in this spectral band. This new dataset validates the current Mlawer-Tobin-Clough-Kneizys-Davies (MT-CKD) 2.5 model parametrization above 300 cm(-1), but indicates the need to strengthen the parametrization below 300 cm(-1), by up to 50 per cent at 100 cm(-1). Data recorded at a number of flight altitudes have allowed measurements within a wide range of column water vapour environments, greatly increasing the sensitivity of this analysis to the continuum strength. PMID:22547236

  4. A new microwave spectrometer for ground-based observations of water vapour

    NASA Astrophysics Data System (ADS)

    Hallgren, K.; Hartogh, P.; Jarchow, C.

    2013-05-01

    We have developed a new, high time-resolution, microwave heterodyne spectrometer for observations of water vapour in the middle atmosphere. It measures the rotational transition of water vapour at 22.235 GHz in the vertical and horizontal polarisation. The two polarisations are averaged in order to optimise the signal-to-noise ratio. The different polarisations have separate, but identical, signal chains consisting of a 22 GHz cooled HEMT amplifier, a second, warm, 22 GHz HEMT booster amplifier, an IF stage and a Chirp Transform Spectrometer (CTS) backend. Continuous calibration with two internal loads kept at temperatures close to the observed atmosphere, a wobbling optical table to reduce standing waves in the optical path and the low receiver temperature ensures a time resolution of an order of magnitude better than what has been achieved by earlier instruments. The error sources in the retrieved spectrum are discussed and the data is compared and validated against EOS-MLS on the NASA Aura satellite. The profiles are found to be in good agreement with each other.

  5. A global climatology of total columnar water vapour from SSM/I and MERIS

    NASA Astrophysics Data System (ADS)

    Lindstrot, R.; Stengel, M.; Schröder, M.; Fischer, J.; Preusker, R.; Schneider, N.; Steenbergen, T.

    2014-01-01

    A global time series of total columnar water vapour from combined data of the Medium Resolution Imaging Spectrometer (MERIS) onboard ESA's Environmental Satellite (ENVISAT) and the Special Sensor Microwave/Imager (SSM/I) onboard the satellite series of the US Defense Meteorological Satellite Program (DMSP) is presented. The unique dataset, generated in the framework of the ESA Data User Element (DUE) GlobVapour project, combines atmospheric water vapour observations over land and ocean, derived from measurements in the near infrared and the microwave range, respectively. Daily composites and monthly means of total columnar water vapour are available as global maps on rectangular latitude-longitude grids with a spatial resolution of 0.05° × 0.05° over land and 0.5° × 0.5° over ocean for the years 2003 to 2008. The data is stored in NetCDF files and is fully compliant with the NetCDF Climate Forecast convention. Through the combination of high quality microwave observations and near infrared observations over ocean and land surfaces, respectively, the dataset provides global coverage. The combination of both products is carried out such that the individual properties of the microwave and near-infrared products, in particular their uncertainties, are not changed and therefore well defined. Due to the global coverage and the provided uncertainty estimates this data set is potentially of high value for climate research. The SSM/I-MERIS TCWV data set is freely available via the GlobVapour project web page with associated doi (doi:10.5676/DFE/WV_COMB/FP). In this paper, the details of the dataset generation, i.e. the satellite data used, the retrieval techniques and merging approaches are presented. The derived level 3 products are compared to global radiosonde data from the GCOS upper air network (GUAN), showing a high agreement with a root mean square deviation of roughly 4.4 kg m-2 and a small

  6. A global climatology of total columnar water vapour from SSM/I and MERIS

    NASA Astrophysics Data System (ADS)

    Lindstrot, R.; Stengel, M.; Schröder, M.; Fischer, J.; Preusker, R.; Schneider, N.; Steenbergen, T.; Bojkov, B. R.

    2014-06-01

    A global time series of total columnar water vapour from combined data of the Medium Resolution Imaging Spectrometer (MERIS) onboard ESA's Environmental Satellite (ENVISAT) and the Special Sensor Microwave/Imager (SSM/I) onboard the satellite series of the US Defense Meteorological Satellite Program (DMSP) is presented. The unique data set, generated in the framework of the ESA Data User Element (DUE) GlobVapour project, combines atmospheric water vapour observations over land and ocean, derived from measurements in the near-infrared and the microwave range, respectively. Daily composites and monthly means of total columnar water vapour are available as global maps on rectangular latitude-longitude grids with a spatial resolution of 0.05° × 0.05° over land and 0.5° × 0.5° over ocean for the years 2003 to 2008. The data are stored in NetCDF files and is fully compliant with the NetCDF Climate Forecast convention. Through the combination of high-quality microwave observations and near-infrared observations over ocean and land surfaces, respectively, the data set provides global coverage. The combination of both products is carried out such that the individual properties of the microwave and near-infrared products, in particular their uncertainties, are not modified by the merging process and are therefore well defined. Due to the global coverage and the provided uncertainty estimates this data set is potentially of high value for climate research. The SSM/I-MERIS TCWV data set is freely available via the GlobVapour project web page (www.globvapour.info) with associated doi:10.5676/DFE/WV_COMB/FP. In this paper, the details of the data set generation, i.e. the satellite data used, the retrieval techniques and merging approaches, are presented. The derived level 3 products are compared to global radiosonde data from the GCOS upper air

  7. Analysis of atmospheric concentrations of quinones and polycyclic aromatic hydrocarbons in vapour and particulate phases

    NASA Astrophysics Data System (ADS)

    Delgado-Saborit, Juana Maria; Alam, Mohammed S.; Godri Pollitt, Krystal J.; Stark, Christopher; Harrison, Roy M.

    2013-10-01

    Polycyclic aromatic hydrocarbons (PAH) are often measured in studies of atmospheric chemistry or health effects of air pollution, due to their known human carcinogenicity. In recent years, PAH quinone derivatives have also become a focus of interest, primarily because they can contribute to oxidative stress. This work reports concentrations of 17 PAH and 15 quinones measured in air samples collected at a trafficked roadside. Data are presented for four compounds not previously reported in ambient air: 2-methyl-1,4-naphthoquinone, 2,6-di-tert-butyl-1,4-benzoquinone, methyl-1,4-benzoquinone and 2,3-dimethylanthraquinone, and a large vapour phase component is measured, not analysed in most earlier studies. Analyses are reported also for SRM 1649a and 1649b, including many compounds (8 for SRM 1649a and 12 for SRM 1649b) for which concentrations have not previously been reported. This work assesses the vapour/particle phase distribution of PAHs and quinones in relation to their molecular weight, vapour pressure, polarity and Henry's Law constant, finding that both molecular weight and vapour pressure (which are correlated) are good predictors of the partitioning.

  8. Airborne hygrometer calibration inter-comparison against a metrological water vapour standard

    NASA Astrophysics Data System (ADS)

    Smorgon, Denis; Boese, Norbert; Ebert, Volker

    2014-05-01

    Water vapour is the most important atmospheric greenhouse gas, which causes a major feedback to warming and other changes in the climate system. Knowledge of the distribution of water vapour and its climate induced changes is especially important in the upper troposphere and lower stratosphere (UT/LS) where vapour plays a critical role in atmospheric radiative balance, cirrus cloud formation, and photochemistry. But, our understanding of water in the UT/LS is limited by significant uncertainties in current UT/LS water measurements. One of the most comprehensive inter-comparison campaigns for airborne hygrometers, termed AQUAVIT (AV1) [1], took place in 2007 at the AIDA chamber at the Karlsruhe Institute of Technology (KIT) in Germany. AV1 was a well-defined, referred, blind inter-comparison of 22 airborne field instruments from 17 international research groups. One major metrological deficit of AV1, however, was, that no traceable reference instrument participated in the inter-comparison experiments and that the calibration procedures of the participating instruments were not monitored or interrogated. Consequently a follow-up inter-comparison was organized in April 2013, which for the first time also provides a traceable link to the international humidity scale. This AQUAVIT2 (AV2) campaign (details see: http://www.imk-aaf.kit.edu/aquavit/index.php/Main_Page) was again located at KIT/AIDA and organised by an international organizing committee including KIT, PTB, FZJ and others. Generally AV2 is divided in two parallel comparisons: 1) AV2-A uses the AIDA chamber for a simultaneous comparison of all instruments (incl. sampling and in-situ instruments) over a broad range of conditions characteristic for the UT/LS; 2) AV2-B, about which this paper is reporting, is a sequential comparison of selected hygrometers and (when possible) their reference calibration infrastructures by means of a chilled mirror hygrometer traced back to the primary National humidity standard

  9. Stable isotope ratios in rainfall and water vapour at Bangalore, Southern India during the monsoon period of 2013

    NASA Astrophysics Data System (ADS)

    Peethambaran, Rahul; Ghosh, Prosenjit

    2015-04-01

    Rainwater and water vapour were collected during monsoon rainfall from Bangalore station to identifying the signature of moisture sources. Moisture responsible for the rainfall originates from Arabian Sea and Bay of Bengal and advected to the station together with vapour generated from the local . Total no of samples includes 72 for water vapour and 81 for rainwater respectively. The mean difference between water vapour and rainwater was found to be -13.27±2.5 ‰ for δ18O, -100±9 ‰ for δD, which was calculated from monthly mean values of water vapour and rainwater. The most enriched samples of rainwater and water vapour were found during the pre monsoon months which correspond to temperature maximum at the study location. Lighter isotopic ratios were recorded in samples collected during the starting of monsoon showers which goes to further depletion in δ18O during the period of post monsoon. This was mainly due to the change in the prevailing wind direction from southwest to northeast. Local Meteoric Water Line (LMWL) generated for rainwater (d = 7.49 δ 18O + 5.2555, R² = 0.93) equation suggesting enrichment due to evaporation. Local Vapour Line (LVL) (d = 7.5248 δ 18O + 6.6534,R² = 0.8957) indicates the dominance of vapor from local source. The time series of d-xcess of rainwater and water vapor reveals large variability, coinciding with the presence of transported and local sources. It was observed that rainwater and water vapor exhibits higher values indicating re-evaporation from the region. Repetition of this feature demonstrated pattern of moisture recycling in the atmosphere and the contribution of continental evaporation and transpiration. The sensitivity of isotopes to the sudden change in wind direction was documented by an abrupt variations in the isotope values. Such changes in wind patterns were mostly associated with the prevalence of low pressure depression systems during the monsoon periods. Detailed analysis on role of wind patterns and

  10. Assessment of UTLS water vapour measurements from limb-sounders within the SPARC Data Initiative

    NASA Astrophysics Data System (ADS)

    Hegglin, M. I.; Tegtmeier, S.; Anderson, J.; Froidevaux, L.; Fuller, R. A.; Funke, B.; Jones, A. K.; Kyrola, E. T.; Lingenfelser, G. S.; Lumpe, J. D.; Remsberg, E. E.; Rozanov, A.; Toohey, M.; Urban, J.; von Clarmann, T.; Walker, K. A.; Wang, H.

    2012-12-01

    The last few decades represent a "golden age" of stratospheric composition measurements that were crucial in advancing our understanding of atmospheric processes and their role in climate. It is likely that the future stratosphere will not be as well measured as it is now. It is important to capture existing knowledge on current and recent instruments before this knowledge is lost. In this contribution we will present a comprehensive comparison of UTLS water vapour measurements obtained from a multi-national set of limb-viewing satellite instruments within the SPARC Data Initiative. We will highlight key results, such as the physical consistency of the different data sets in reproducing the tape recorder, polar vortex dehydration, interannual variability, and seasonal cycles. We will discuss potential reasons for the differences and implications for the use of the data sets in merging and model validation activities, as well as for the interpretation of atmospheric trends and processes.

  11. Ground-based GPS-derived Precipitable Water Vapour Estimates for Climate Application in Australia

    NASA Astrophysics Data System (ADS)

    Choy, Suelynn; Dawson, John; Jia, Minghai; Kuleshov, Yuriy

    2013-04-01

    Atmospheric water vapour is a critical component of the greenhouse effect and plays a significant role in the global climate system. The knowledge of the long-term spatial and temporal variability of water vapour is vital for understanding climate change. The Global Positioning System (GPS) has long offered the prospect of retrieving column integrated Precipitable Water Vapour (PWV) profiles from the time-varying tropospheric Zenith Path Delay (ZPD), which can be retrieved by stochastic filtering of the GPS measurements. However, observing GPS-PWV for climate studies requires a homogenous and long-term time series of GPS data. We present a regional reanalysis of GPS data focussing on the Australian Regional GPS Network stations from 1997 to 2012 (15 years). These stations are selectively chosen to provide a representative regional distribution of GPS sites on the Australian continent while ensuring conventional meteorological observations (surface-based data) are available for PWV conversion and other PWV sensors (e.g. upper-air data from radiosondes) for validation purposes. The research work is divided into three components: 1) estimation of homogenous long-term tropospheric ZPD from GPS measurements that are accurate, stable and consistent; 2) conversion of tropospheric ZPD to PWV estimates given surface temperature and pressure readings, and 3) intertechnique comparison and validation of the GPS-derived PWV. The derived data will be used to investigate the secular trend and seasonal variation PWV time series and its implications for climate application. This research represents the first attempt to utilise the Australian regional network of GPS stations to study the climate processes and variations from the long-term time series of GPS-PWV.

  12. Water vapour foreign-continuum absorption in near-infrared windows from laboratory measurements.

    PubMed

    Ptashnik, Igor V; McPheat, Robert A; Shine, Keith P; Smith, Kevin M; Williams, R Gary

    2012-06-13

    For a long time, it has been believed that atmospheric absorption of radiation within wavelength regions of relatively high infrared transmittance (so-called 'windows') was dominated by the water vapour self-continuum, that is, spectrally smooth absorption caused by H(2)O--H(2)O pair interaction. Absorption due to the foreign continuum (i.e. caused mostly by H(2)O--N(2) bimolecular absorption in the Earth's atmosphere) was considered to be negligible in the windows. We report new retrievals of the water vapour foreign continuum from high-resolution laboratory measurements at temperatures between 350 and 430 K in four near-infrared windows between 1.1 and 5 μm (9000-2000 cm(-1)). Our results indicate that the foreign continuum in these windows has a very weak temperature dependence and is typically between one and two orders of magnitude stronger than that given in representations of the continuum currently used in many climate and weather prediction models. This indicates that absorption owing to the foreign continuum may be comparable to the self-continuum under atmospheric conditions in the investigated windows. The calculated global-average clear-sky atmospheric absorption of solar radiation is increased by approximately 0.46 W m(-2) (or 0.6% of the total clear-sky absorption) by using these new measurements when compared with calculations applying the widely used MTCKD (Mlawer-Tobin-Clough-Kneizys-Davies) foreign-continuum model. PMID:22547232

  13. Retrieval of Temperature and Water Vapour From Multiple Channel Lidar Systems Using an Optimal Estimation Method

    NASA Astrophysics Data System (ADS)

    Sica, Robert; Haefele, Alexander

    2015-04-01

    While the application of optimal estimation methods (OEMs) is well-known for the retrieval of atmospheric parameters from passive instruments, active instruments have typically not employed the OEM. For instance, the measurement of temperature in the middle atmosphere with Rayleigh-scatter lidars is an important technique for assessing atmospheric change. Current retrieval schemes for these temperatures have several shortcomings which can be overcome using an OEM. Forward models have been constructed that fully characterize the measurement and allow the simultaneous retrieval of temperature, dead time and background. The OEM allows a full uncertainty budget to be obtained on a per profile basis that includes, in addition to the statistical uncertainties, the smoothing error and uncertainties due to Rayleigh extinction, ozone absorption, the lidar constant, nonlinearity in the counting system, variation of the Rayleigh-scatter cross section with altitude, pressure, acceleration due to gravity and the variation of mean molecular mass with altitude. The vertical resolution of the temperature profile is found at each height, and a quantitative determination is made of the maximum height to which the retrieval is valid. A single temperature profile can be retrieved from measurements with multiple channels that cover different height ranges, vertical resolutions and even different detection methods. The OEM employed is shown to give robust estimates of temperature consistent with previous methods, while requiring minimal computational time. Retrieval of water vapour mixing ratio from vibrational Raman scattering lidar measurements is another example where an OEM offers a considerable advantage over the standard analysis technique, with the same advantages as discussed above for Rayleigh-scatter temperatures but with an additional benefit. The conversion of the lidar measurement into mixing ratio requires a calibration constant to be employed. Using OEM the calibration

  14. Retrieval of Temperature and Water Vapour from Multiple Channel Lidar Systems Using an Optimal Estimation Method

    NASA Astrophysics Data System (ADS)

    Sica, Robert; Haefele, Alexander

    2016-04-01

    While the application of optimal estimation methods (OEMs) is well-known for the retrieval of atmospheric parameters from passive instruments, active instruments have typically not employed the OEM. For instance, the measurement of temperature in the middle atmosphere with Rayleigh-scatter lidars is an important technique for assessing atmospheric change. Current retrieval schemes for these temperatures have several shortcomings which can be overcome using an OEM. Forward models have been constructed that fully characterize the measurement and allow the simultaneous retrieval of temperature, dead time and background. The OEM allows a full uncertainty budget to be obtained on a per profile basis that includes, in addition to the statistical uncertainties, the smoothing error and uncertainties due to Rayleigh extinction, ozone absorption, the lidar constant, nonlinearity in the counting system, variation of the Rayleigh-scatter cross section with altitude, pressure, acceleration due to gravity and the variation of mean molecular mass with altitude. The vertical resolution of the temperature profile is found at each height, and a quantitative determination is made of the maximum height to which the retrieval is valid. A single temperature profile can be retrieved from measurements with multiple channels that cover different height ranges, vertical resolutions and even different detection methods. The OEM employed is shown to give robust estimates of temperature consistent with previous methods, while requiring minimal computational time. Retrieval of water vapour mixing ratio from vibrational Raman scattering lidar measurements is another example where an OEM offers a considerable advantage over the standard analysis technique, with the same advantages as discussed above for Rayleigh-scatter temperatures but with an additional benefit. The conversion of the lidar measurement into mixing ratio requires a calibration constant to be employed. Using OEM the calibration

  15. Pressure effects on water vapour lines: beyond the Voigt profile.

    PubMed

    Ngo, N H; Tran, H; Gamache, R R; Hartmann, J M

    2012-06-13

    A short overview of recent results on the effects of pressure (collisions) regarding the shape of isolated infrared lines of water vapour is presented. The first part of this study considers the basic collisional quantities, which are the pressure-broadening and -shifting coefficients, central parameters of the Lorentzian (and Voigt) profile and thus of any sophisticated line-shape model. Through comparisons of measured values with semi-classical calculations, the influences of the molecular states (both rotational and vibrational) involved and of the temperature are analysed. This shows the relatively unusual behaviour of H(2)O broadening, with evidence of a significant vibrational dependence and the fact that the broadening coefficient (in cm(-1) atm(-1)) of some lines increases with temperature. In the second part of this study, line shapes beyond the Voigt model are considered, thus now taking 'velocity effects' into account. These include both the influence of collisionally induced velocity changes that lead to the so-called Dicke narrowing and the influence of the dependence of collisional parameters on the speed of the radiating molecule. Experimental evidence of deviations from the Voigt shape is presented and analysed. The interest of classical molecular dynamics simulations, to model velocity changes, together with semi-classical calculations of the speed-dependent collisional parameters for line-shape predictions from 'first principles', are discussed. PMID:22547229

  16. Measurements of mesospheric water vapour, aerosols and temperatures with the Spectral Absorption Line Imager (SALI-AT)

    NASA Astrophysics Data System (ADS)

    Shepherd, M. G.; Mullins, M.; Brown, S.; Sargoytchev, S. I.

    2001-08-01

    Water vapour concentration is one of the most important, yet one of the least known quantities of the mesosphere. Knowledge of water vapour concentration is the key to understanding many mesospheric processes, including the one that is primary focus of our investigation, mesospheric clouds (MC). The processes of formation and occurrence parameters of MC constitute an interesting problem in their own right, but recently evidence has been provided which suggests that they are a critical indicator of atmospheric change. The aim of the SALI-AT experiment is to make simultaneous (although not strictly collocated) measurements of water vapour, aerosols and temperature in the mesosphere and the mesopause region under twilight condition in the presence of mesospheric clouds. The water vapour will be measured in the regime of solar occultation utilizing a water vapour absorption band at 936 nm wavelength employing the SALI (Spectral Absorption Line Imager) instrument concept. A three-channel zenith photometer, AT-3, with wavelengths of 385 nm, 525 nm, and 1040 nm will measure Mie and Rayleigh scattering giving both mesospheric temperature profiles and the particle size distribution. Both instruments are small, low cost and low mass. It is envisioned that the SALI-AT experiment be flown on a small rocket - the Improved Orion/Hotel payload configuration, from the Andoya Rocket range, Norway. Alternatively the instrument can be flown as a "passenger" on larger rocket carrying other experiments. In either case flight costs are relatively low. Some performance simulations are presented showing that the instrument we have designed will be sufficiently sensitive to measure water vapor in concentrations that are expected at the summer mesopause, about 85 km height.

  17. Design Of A Geosynchronous SAR System For Water-Vapour Maps And Deformation Estimation

    NASA Astrophysics Data System (ADS)

    Guarnieri, Andrea Monti; Perletta, Luca; Rocca, Fabio; Scapin, Diego; Tebaldini, Stefano; Broquetas, Antoni; Ruiz, Josep

    2012-01-01

    In this paper, we propose a geosynchronous SAR concept that makes use of dual frequencies to achieve WIDE and SPOT coverage, aiming at continuous monitoring of deformation and generation of water vapour maps at high space-temporal resolution.

  18. Mesoscale modelling of water vapour in the tropical UTLS: two case studies from the HIBISCUS campaign

    NASA Astrophysics Data System (ADS)

    Marécal, V.; Durry, G.; Longo, K.; Freitas, S.; Rivière, E. D.; Pirre, M.

    2006-08-01

    In this study, we evaluate the ability of the BRAMS mesoscale model compared to ECMWF global analysis to simulate the observed vertical variations of water vapour in the tropical upper troposphere and lower stratosphere (UTLS). The observations are balloon-borne measurements of water vapour mixing ratio and temperature from micro-SDLA (Tunable Diode Laser Spectrometer) instrument. Data from two balloon flights performed during the 2004 HIBISCUS field campaign are used to compare with the mesoscale simulations and to ECMWF analysis. The mesoscale model performs significantly better than ECMWF analysis for water vapour in the upper troposphere and similarly or slightly worse for temperature. The improvement provided by the mesoscale model for water vapour comes mainly from (i) the enhanced vertical resolution in the UTLS (250 m for BRAMS and ~1 km for ECMWF model) and (ii) the more detailed microphysical parameterization providing ice supersaturations as in the observations. The ECMWF vertical resolution (~1 km) is too coarse to capture the observed fine scale vertical variations of water vapour in the UTLS. In near saturated or supersaturated layers, the mesoscale model relative humidity with respect to ice saturation is close to observations provided that the temperature profile is realistic. For temperature, ECMWF analysis gives good results partly thanks to data assimilation. The analysis of the mesoscale model results showed that in undersaturated layers, the water vapour profile depends mainly on the dynamics. In saturated/supersaturated layers, microphysical processes play an important role and have to be taken into account on top of the dynamical processes to understand the water vapour profiles. In the lower stratosphere, the ECMWF model and the BRAMS model give very similar water vapour profiles that are significantly dryer than micro-SDLA measurements. This similarity comes from the fact that BRAMS is initialised using ECMWF analysis and that no mesoscale

  19. Vertical structure of stratospheric water vapour trends derived from merged satellite data

    NASA Astrophysics Data System (ADS)

    Hegglin, M. I.; Plummer, D. A.; Shepherd, T. G.; Scinocca, J. F.; Anderson, J.; Froidevaux, L.; Funke, B.; Hurst, D.; Rozanov, A.; Urban, J.; von Clarmann, T.; Walker, K. A.; Wang, H. J.; Tegtmeier, S.; Weigel, K.

    2014-10-01

    Stratospheric water vapour is a powerful greenhouse gas. The longest available record from balloon observations over Boulder, Colorado, USA shows increases in stratospheric water vapour concentrations that cannot be fully explained by observed changes in the main drivers, tropical tropopause temperatures and methane. Satellite observations could help resolve the issue, but constructing a reliable long-term data record from individual short satellite records is challenging. Here we present an approach to merge satellite data sets with the help of a chemistry-climate model nudged to observed meteorology. We use the models' water vapour as a transfer function between data sets that overcomes issues arising from instrument drift and short overlap periods. In the lower stratosphere, our water vapour record extends back to 1988 and water vapour concentrations largely follow tropical tropopause temperatures. Lower and mid-stratospheric long-term trends are negative, and the trends from Boulder are shown not to be globally representative. In the upper stratosphere, our record extends back to 1986 and shows positive long-term trends. The altitudinal differences in the trends are explained by methane oxidation together with a strengthened lower-stratospheric and a weakened upper-stratospheric circulation inferred by this analysis. Our results call into question previous estimates of surface radiative forcing based on presumed global long-term increases in water vapour concentrations in the lower stratosphere.

  20. Calibration of a water vapour Raman lidar with a kite-based humidity sensor

    NASA Astrophysics Data System (ADS)

    Totems, Julien; Chazette, Patrick

    2016-03-01

    We present a calibration method for a water vapour Raman lidar using a meteorological probe lifted by a kite, flown steadily above the lidar site, within the framework of the Hydrological Cycle in the Mediterranean Experiment (HyMeX) and Chemistry-Aerosol Mediterranean Experiment (ChArMEx) campaigns. The experiment was carried out in Menorca (Spain) during June 2013, using the mobile water vapour and aerosol lidar WALI. Calibration using a kite demonstrated a much better degree of co-location with the lidar system than that which could be achieved with radiosondes, and it allowed us to determine the overlap function and calibration factor simultaneously. The range-dependent water vapour lidar calibration was thus determined with an uncertainty of 2 % in the 90-8000 m altitude range. Lidar water vapour measurements are further compared with radiosondes, showing very good agreement in the lower troposphere (1-5 km) and a relative difference and standard deviation of 5 and 9 % respectively. Moreover, a reasonable agreement with MODIS-integrated water vapour content is found, with a relative mean and standard deviation of 3 and 16 % respectively. However, a discrepancy is found with AERONET retrievals, showing the latter to be underestimated by 28 %. Reanalyses by the ECMWF/IFS numerical weather prediction model also agree with the temporal evolution highlighted with the lidar, with no measurable drift in integrated water vapour content over the period.

  1. Preliminary tropospheric ozone DIAL, water vapour, and aerosol lidar measurements during ARC-IONS

    NASA Astrophysics Data System (ADS)

    Strawbridge, Kevin B.; Firanski, Bernard J.

    2009-09-01

    A new lidar instrument, dubbed AeRO (Aerosol Raman Ozone) Lidar, is being developed at Environment Canada's Centre For Atmospheric Research Experiments (CARE). The new system will use three lasers to simultaneously measure ozone, water vapour and aerosol profiles (including extinction) from near ground to the tropopause. The main thrust will focus on understanding Air Quality within the airshed with the capability of looking at Stratospheric Tropospheric Exchange (STE) processes to determine the magnitude and frequency of such events leading to elevated levels of tropospheric ozone. In addition a wind profiler through a partnership with University of Western Ontario will soon be deployed to CARE to provide complementary observations of the tropopause. The lidar participated in the ARC-IONS field campaign during April and July of 2008. During the field campaign, daily ozonesondes were released to further compliment the lidar measurements. Details of the system design and preliminary results from the lidar measurements will be presented.

  2. Formation of formic acid and organic peroxides in the ozonolysis of ethene with added water vapour

    NASA Astrophysics Data System (ADS)

    Horie, Osamu; Neeb, Peter; Limbach, Stefan; Moortgat, Geert K.

    1994-07-01

    Ozonolysis of C2H4 was carried out in a 580 l glass reaction vessel at 1-5 ppm reactant concentrations, with added water vapour. Under dry conditions ([H2O]0 = 0.5 ppm), HCHO, CO, CO2, (CHO)2O (formic acid anhydride), H2O2, and CH3OOH were identified as the reaction products. Under wet conditions ([H2O]0 = 2 × 104 ppm), HCOOH yields approaching ca. 20% of the converted C2H4, were observed, while no (CHO)2O was formed. Hydroxymethyl hydroperoxide, HOCH2OOH, was observed as the major peroxide, and found to be formed only in the presence of water vapour. Direct reactions of H2O vapour with the excited CH2OO* radicals and with stabilized CH2OO radicals are postulated to explain the formation of HCOOH and HOCH2OOH in the presence of water vapour, respectively.

  3. A decrease in mesospheric water vapour detected in South-Korea in February 2008; from observation to interpretation.

    NASA Astrophysics Data System (ADS)

    de Wachter, Evelyn; Kaempfer, Niklaus; Flury, Thomas; Ka, Soohyun; Oh, Jung Jin

    Since November 2006, the University of Bern in Switzerland has been operating a ground-based microwave [GBMW] radiometer in Seoul, S-Korea [37.32N, 126.57E]. At the end of February 2008 we observed a significant decrease in mesospheric water vapour of more than 2 ppmv [around 40Trajectories were calculated and the temperature and wind field distribution in the northern hemisphere was analyzed. We validated the trajectory model results by a match tech-nique with other GBMW radiometer data from stations of the Network for the Detection of Atmospheric Composition Change [NDACC]. In addition, we investigated the possible impact of the major sudden stratospheric warming [SSW], which occured in February 2008 at midlat-itudes, to the mesospheric region, leaving signatures in the water vapour distribution at the observation site in Seoul.

  4. Ground-based remote sensing of tropospheric water vapour isotopologues within the project MUSICA

    NASA Astrophysics Data System (ADS)

    Schneider, M.; Barthlott, S.; Hase, F.; González, Y.; Yoshimura, K.; García, O. E.; Sepúlveda, E.; Gomez-Pelaez, A.; Gisi, M.; Kohlhepp, R.; Dohe, S.; Blumenstock, T.; Strong, K.; Weaver, D.; Palm, M.; Deutscher, N. M.; Warneke, T.; Notholt, J.; Lejeune, B.; Demoulin, P.; Jones, N.; Griffith, D. W. T.; Smale, D.; Robinson, J.

    2012-08-01

    Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water), long-term tropospheric water vapour isotopologues data records are provided for ten globally distributed ground-based mid-infrared remote sensing stations of the NDACC (Network for the Detection of Atmospheric Composition Change). We present a new method allowing for an extensive and straightforward characterisation of the complex nature of such isotopologue remote sensing datasets. We demonstrate that the MUSICA humidity profiles are representative for most of the troposphere with a vertical resolution ranging from about 2 km (in the lower troposphere) to 8 km (in the upper troposphere) and with an estimated precision of better than 10%. We find that the sensitivity with respect to the isotopologue composition is limited to the lower and middle troposphere, whereby we estimate a precision of about 30‰ for the ratio between the two isotopologues HD16O and H216O. The measurement noise, the applied atmospheric temperature profiles, the uncertainty in the spectral baseline, and interferences from humidity are the leading error sources. We introduce an a posteriori correction method of the humidity interference error and we recommend applying it for isotopologue ratio remote sensing datasets in general. In addition, we present mid-infrared CO2 retrievals and use them for demonstrating the MUSICA network-wide data consistency. In order to indicate the potential of long-term isotopologue remote sensing data if provided with a well-documented quality, we present a climatology and compare it to simulations of an isotope incorporated AGCM (Atmospheric General Circulation Model). We identify differences in the multi-year mean and seasonal cycles that significantly exceed the estimated errors, thereby indicating deficits in the modeled atmospheric water cycle.

  5. Ground-based remote sensing of tropospheric water vapour isotopologues within the project MUSICA

    NASA Astrophysics Data System (ADS)

    Schneider, M.; Barthlott, S.; Hase, F.; González, Y.; Yoshimura, K.; García, O. E.; Sepúlveda, E.; Gomez-Pelaez, A.; Gisi, M.; Kohlhepp, R.; Dohe, S.; Blumenstock, T.; Wiegele, A.; Christner, E.; Strong, K.; Weaver, D.; Palm, M.; Deutscher, N. M.; Warneke, T.; Notholt, J.; Lejeune, B.; Demoulin, P.; Jones, N.; Griffith, D. W. T.; Smale, D.; Robinson, J.

    2012-12-01

    Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water), long-term tropospheric water vapour isotopologue data records are provided for ten globally distributed ground-based mid-infrared remote sensing stations of the NDACC (Network for the Detection of Atmospheric Composition Change). We present a new method allowing for an extensive and straightforward characterisation of the complex nature of such isotopologue remote sensing datasets. We demonstrate that the MUSICA humidity profiles are representative for most of the troposphere with a vertical resolution ranging from about 2 km (in the lower troposphere) to 8 km (in the upper troposphere) and with an estimated precision of better than 10%. We find that the sensitivity with respect to the isotopologue composition is limited to the lower and middle troposphere, whereby we estimate a precision of about 30‰ for the ratio between the two isotopologues HD16O and H216O. The measurement noise, the applied atmospheric temperature profiles, the uncertainty in the spectral baseline, and the cross-dependence on humidity are the leading error sources. We introduce an a posteriori correction method of the cross-dependence on humidity, and we recommend applying it to isotopologue ratio remote sensing datasets in general. In addition, we present mid-infrared CO2 retrievals and use them for demonstrating the MUSICA network-wide data consistency. In order to indicate the potential of long-term isotopologue remote sensing data if provided with a well-documented quality, we present a climatology and compare it to simulations of an isotope incorporated AGCM (Atmospheric General Circulation Model). We identify differences in the multi-year mean and seasonal cycles that significantly exceed the estimated errors, thereby indicating deficits in the modeled atmospheric water cycle.

  6. Long-term series of tropospheric water vapour amounts and HDO/H2O ratio profiles above Jungfraujoch.

    NASA Astrophysics Data System (ADS)

    Lejeune, B.; Mahieu, E.; Schneider, M.; Hase, F.; Servais, C.; Demoulin, P.

    2012-04-01

    Water vapour is a crucial climate variable involved in many processes which widely determine the energy budget of our planet. In particular, water vapour is the dominant greenhouse gas in the Earth's atmosphere and its radiative forcing is maximum in the middle and upper troposphere. Because of the extremely high variability of water vapour concentration in time and space, it is challenging for the available relevant measurement techniques to provide a consistent data set useful for trend analyses and climate studies. Schneider et al. (2006a) showed that ground-based Fourier Transform Infrared (FTIR) spectroscopy, performed from mountain observatories, allows for the detection of H2O variabilities up to the tropopause. Furthermore, the FTIR measurements allow the retrieval of HDO amounts and therefore the monitoring of HDO/H2O ratio profiles whose variations act as markers for the source and history of the atmospheric water vapour. In the framework of the MUSICA European project (Multi-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water, http://www.imk-asf.kit.edu/english/musica.php), a new approach has been developed and optimized by M. Schneider and F. Hase, using the PROFFIT algorithm, to consistently retrieve tropospheric water vapour profiles from high-resolution ground-based infrared solar spectra and so taking benefit from available long-term data sets of ground-based observations. The retrieval of the water isotopologues is performed on a logarithmic scale from 14 micro-windows located in the 2600-3100 cm-1 region. Other important features of this new retrieval strategy are: a speed dependant Voigt line shape model, a joint temperature profile retrieval and an interspecies constraint for the HDO/H2O profiles. In this contribution, we will combine the quality of the MUSICA strategy and of our observations, which are recorded on a regular basis with FTIR spectrometers, under clear-sky conditions, at the NDACC site

  7. Water Vapour GNSS Based Tomography For Wet Delay Compensation In In-SAR Applications

    NASA Astrophysics Data System (ADS)

    Notarpietro, Riccardo; Cucca, Manuela; Perona, Giovanni

    2010-05-01

    One of the most challenging exploitation of GNSS signals for meteorological applications is the retrieval of Water Vapor tridimensional distribution. The real-time (or quasi real-time) knowledge of such distributions could be very useful for several applications: from operative meteorology to atmospheric modeling, or for atmospheric compensation purposes applied for example to SAR or In-SAR observations, in order to improve land remote sensing. In the framework of the European Space Agency project METAWAVE (Mitigation of Electromagnetic Transmission errors induced by Atmospheric Water Vapor Effects), several techniques were investigated in order to find out an In-SAR data compensation strategy for the propagation delay effects due to Water Vapour. Thanks to METAWAVE, a quite dense GPS network (7 dual frequency GPS receivers) was deployed over COMO area and was used for an extensive measurement campaign. The acquired L1 and L2 carrier phase observations were processed in terms of hourly averaged Zenith Wet Delays. These vertical information were mapped along the correspondent line of sights (by up-sampling at 30 second sample times the 15 minutes GPS satellites positions obtained from IGS files) and inverted using a tomographic procedure. The used algorithm performs a first reconstruction (namely, the tomographic pre-processing) based on generalized inversion mechanisms, in order to define a low resolution first guess for the next step. This second step inverts GPS observables using a more refined algebraic tomographic reconstruction algorithm, to improve both vertical and horizontal resolution. Results of this inversion are Wet Refractivity maps distributed over an area of 16 km x 20 km (x 10 km height) around the COMO city, characterized by horizontal resolutions varying from 2 km to 4 km and vertical resolution of 500m. This contribution deals with the description of the results obtained evaluating Water Vapour path delays from such Wet Refractivity maps

  8. Water vapour transport in the tropical tropopause region in coupled Chemistry-Climate Models and ERA-40 reanalysis data

    NASA Astrophysics Data System (ADS)

    Kremser, Stefanie; Wohltmann, Ingo; Rex, Markus; Langematz, Ulrike; Dameris, Martin; Kunze, Markus

    2009-04-01

    In this study backward trajectories from the tropical lower stratosphere were calculated for the Northern Hemisphere (NH) winters 1995-1996, 1997-1998 (El Niño) and 1998-1999 (La Niña) and summers 1996, 1997 and 1999 using both ERA-40 reanalysis data of the European Centre for Medium-Range Weather Forecast (ECMWF) and coupled Chemistry-Climate Model (CCM) data. The calculated trajectories were analysed to determine the distribution of points where individual air masses encounter the minimum temperature and thus minimum water vapour mixing ratio during their ascent through the tropical tropopause layer (TTL) into the stratosphere. The geographical distribution of these dehydration points and the local conditions there determine the overall water vapour entry into the stratosphere. Results of two CCMs are presented: the ECHAM4.L39(DLR)/CHEM (hereafter: E39/C) from the German Aerospace Center (DLR) and the Freie Universität Berlin Climate Middle Atmosphere Model with interactive chemistry (hereafter: FUB-CMAM-CHEM). In the FUB-CMAM-CHEM model the minimum temperatures are overestimated by about 9 K in NH winter and about 3 K in NH summer, resulting in too high water vapour entry values compared to ERA-40. However, the geographical distribution of dehydration points is fairly similar to ERA-40 for NH winter 1995-1996 and 1998-1999. The distribution of dehydration points in the boreal summer 1996 suggests an influence of the Indian monsoon upon the water vapour transport. The E39/C model displays a temperature bias of about +5 K. Hence, the minimum water vapour mixing ratios are higher relative to ERA-40. The geographical distribution of dehydration points is fairly well in NH winter 1995-1996 and 1997-1998 with respect to ERA-40. The distribution is not reproduced for the NH winter 1998-1999 (La Niña event) compared to ERA-40. There is an excessive water vapour flux through warm regions e.g. Africa in the NH winter and summer. The possible influence of the Indian

  9. Forecasting the precipitable water vapour content: validation for astronomical observatories using radiosoundings

    NASA Astrophysics Data System (ADS)

    Pérez-Jordán, G.; Castro-Almazán, J. A.; Muñoz-Tuñón, C.; Codina, B.; Vernin, J.

    2015-09-01

    The atmospheric precipitable water vapour content (PWV) strongly affects astronomical observations in the infrared (IR). We have validated the Weather Research and Forecasting (WRF) mesoscale numerical weather prediction (NWP) model as an operational forecasting tool for PWV. In the validation, we used atmospheric radiosounding data obtained directly at the Roque de los Muchachos Observatory [ORM: ≈2200 metres above sea level (masl)] during three intensive runs and an aditional verification sample of 1 yr of radiosonde data from World Meteorological Organization (WMO) station 60018 in Güímar (Tenerife, TFE: ≈105 masl). These data sets allowed us to calibrate the model at the observatory site and to validate it under different PWV and atmospheric conditions. The ability of the WRF model in forecasting the PWV at astronomical observatories and the effects of horizontal model grid size on the computed PWV and vertical profiles of humidity are discussed. An excellent agreement between model forecasts and observations was found at both locations, with correlations above 0.9 in all cases. Subtle but significant differences between model horizontal resolutions have been found, the 3 km grid size being the most accurate and the one selected for future work. Absolute calibrations are given for the lowest and finest grid resolutions. The median PWV values obtained were 3.8 and 18.3 mm at ORM and TFE, respectively. WRF forecasts will complement the PWV measured by the GPS monitoring system at the Canarian Observatories.

  10. Kinetic model of water vapour adsorption by gluten-free starch

    NASA Astrophysics Data System (ADS)

    Ocieczek, Aneta; Kostek, Robert; Ruszkowska, Millena

    2015-01-01

    This study evaluated the kinetics of water vapour adsorption on the surface of starch molecules derived from wheat. The aim of the study was to determine an equation that would allow estimation of water content in tested material in any timepoint of the adsorption process aimed at settling a balance with the environment. An adsorption isotherm of water vapour on starch granules was drawn. The parameters of the Guggenheim, Anderson, and De Boer equation were determined by characterizing the tested product and adsorption process. The equation of kinetics of water vapour adsorption on the surface of starch was determined based on the Guggenheim, Anderson, and De Boer model describing the state of equilibrium and on the model of a first-order linear inert element describing the changes in water content over time.

  11. Sensitivity of polar stratospheric cloud formation to changes in water vapour and temperature

    NASA Astrophysics Data System (ADS)

    Khosrawi, F.; Urban, J.; Lossow, S.; Stiller, G.; Weigel, K.; Braesicke, P.; Pitts, M. C.; Rozanov, A.; Burrows, J. P.; Murtagh, D.

    2016-01-01

    More than a decade ago it was suggested that a cooling of stratospheric temperatures by 1 K or an increase of 1 ppmv of stratospheric water vapour could promote denitrification, the permanent removal of nitrogen species from the stratosphere by solid polar stratospheric cloud (PSC) particles. In fact, during the two Arctic winters 2009/10 and 2010/11 the strongest denitrification in the recent decade was observed. Sensitivity studies along air parcel trajectories are performed to test how a future stratospheric water vapour (H2O) increase of 1 ppmv or a temperature decrease of 1 K would affect PSC formation. We perform our study based on measurements made during the Arctic winter 2010/11. Air parcel trajectories were calculated 6 days backward in time based on PSCs detected by CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder satellite observations). The sensitivity study was performed on single trajectories as well as on a trajectory ensemble. The sensitivity study shows a clear prolongation of the potential for PSC formation and PSC existence when the temperature in the stratosphere is decreased by 1 K and water vapour is increased by 1 ppmv. Based on 15 years of satellite measurements (2000-2014) from UARS/HALOE, Envisat/MIPAS, Odin/SMR, Aura/MLS, Envisat/SCIAMACHY and SCISAT/ACE-FTS it is further investigated if there is a decrease in temperature and/or increase of water vapour (H2O) observed in the polar regions similar to that observed at midlatitudes and in the tropics. Performing linear regression analyses we derive from the Envisat/MIPAS (2002-2012) and Aura/MLS (2004-2014) observations predominantly positive changes in the potential temperature range 350 to 1000 K. The linear changes in water vapour derived from Envisat/MIPAS observations are largely insignificant, while those from Aura/MLS are mostly significant. For the temperature neither of the two instruments indicate any significant changes. Given the strong inter-annual variation observed in

  12. A global view on near-surface deuterated water vapour - First results from SCIAMACHY onboard ENVISAT

    NASA Astrophysics Data System (ADS)

    Frankenberg, C.; Aben, I.; Butz, A.; Griffith, D.; Hase, F.; Schneider, M.; Schrijver, H.; Warneke, T.; Roeckmann, T.

    2008-12-01

    Water vapour is by far the most important greenhouse gas in the atmosphere and an accurate knowledge of hydrological cycles and their feedback mechanisms is therefore indispensable for reliable climate predictions. The relative abundance of HDO provides a deeper insight into hydrological cycles as evaporation and condensation processes deplete heavy water in the gas phase. Only recently, global measurements of HDO depletions in the middle to lower troposphere were performed by the Tropospheric Emission Spectrometer (TES) aboard the Aura spacecraft. Global measurements of the isotopic composition of near-surface water vapor are so far missing. The SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) instrument aboard the European Space Agency (ESA)'s environmental research satellite ENVISAT records the intensity of solar radiation, reflected from the Earth surface or the atmosphere, at moderate spectral resolution between 240 and 2390 nm. Its potential to simultaneously retrieve HDO and H2O total columns with high sensitivity toward the surface has so far not been exploited. Here, we present first retrievals of the near-global relative deuterated water vapor distribution from SCIAMACHY. Large scale features such as the latitudinal effect or continental gradients in North-America can be nicely observed. Even small scale features such as relatively high HDO abundances above the Red Sea can be observed. Comparisons with ground-based Fourier Transform measurements (FTS) indicate that also retrievals at high latitude sites such as Ny Alesund (79deg N) are feasible. We will present near-global measurements from SCIAMACHY, including long-term means showing pronounced large-scale as well as small-scale features. Further, we report on large seasonal variations, being higher than those observed by TES. For selected stations in tropical, mid and high-latitude sites, we show comparisons with ground-based direct sun FTS measurements.

  13. Initial evaluation of airborne water vapour measurements by the IAGOS-GHG CRDS system

    NASA Astrophysics Data System (ADS)

    Filges, Annette; Gerbig, Christoph; Smit, Herman G. J.; Krämer, Martina; Spelten, Nicole

    2013-04-01

    Accurate and reliable airborne measurements of water vapour are still a challenge. Presently, no airborne humidity sensor exists that covers the entire range of water vapour content between the surface and the upper troposphere/lower stratosphere (UT/LS) region with sufficient accuracy and time resolution. Nevertheless , these data are a pre-requisite to study the underlying processes in the chemistry and physics of the atmosphere. The DENCHAR project (Development and Evaluation of Novel Compact Hygrometer for Airborne Research) addresses this deficit by developing and characterizing novel or improved compact airborne hygrometers for different airborne applications within EUFAR (European Facility for Airborne Research). As part of the DENCHAR inter-comparison campaign in Hohn (Germany), 23 May - 1 June 2011, a commercial gas analyzer (G2401-m, Picarro Inc.,US), based on cavity ring-down spectroscopy (CRDS), was installed on a Learjet to measure water vapour, CO2, CH4 and CO. The CRDS components are identical to those chosen for integration aboard commercial airliner within IAGOS (In-service Aircraft for a Global Observing System). Thus the campaign allowed for the initial assessment validation of the long-term IAGOS H2O measurements by CRDS against reference instruments with a long performance record (FISH, the Fast In-situ Stratospheric Hygrometer, and CR2 frostpoint hygrometer, both research centre Juelich). The inlet system, a one meter long 1/8" FEP-tube connected to a Rosemount TAT housing (model 102BX, deiced) installed on a window plate of the aircraft, was designed to eliminate sampling of larger aerosols, ice particles, and water droplets, and provides about 90% of ram-pressure. In combination with a lowered sample flow of 0.1 slpm (corresponding to a 4 second response time), this ensured a fully controlled sample pressure in the cavity of 140 torr throughout an aircraft altitude operating range up to 12.5 km without the need of an upstream sampling pump

  14. [CO2-exchange of some lichens after absorption of water vapour].

    PubMed

    Bertsch, A

    1966-06-01

    The relation between CO2-exchange and water content of the lichens Evernia divaricata, E. prunastri, Ramalina thrausta and R. farinacea was investigated. The dry thalli absorb water vapour up to 70% of their dry weight. This uptake of water vapour is sufficient to reactivate the CO2-exchange. In equilibrium with the vapour pressure of the nearly saturated air the apparent CO2-uptake amounts to 90% of the value obtained after imbibition with liquid water. Even in unsaturated air the CO2-exchange is reactivated and the compensation point is reached between 80 and 85% relative humidity (saturation deficit at 10°C: 1,85-1,38 mm Hg). PMID:24557739

  15. Verification of H2O lines from the HITRAN database for remote sensing of the water vapour isotopic composition

    NASA Astrophysics Data System (ADS)

    Rokotyan, N. V.; Zakharov, V. I.; Sinitsa, L. N.; Voronin, B. A.; Lavrentieva, N. N.; Dudaryonok, A. S.

    2015-11-01

    The quality of the spectroscopic line parameters from the HITRAN Database for remote sensing of the water vapour isotopic composition of the atmosphere is widely discussed. In this research we show that the HITRAN-2008 data for H2O isotopologues in the near infrared spectral range (4000-6400 cm-1) is reasonably good. The HITRAN data was tested with independent calculation (ab initio et al.). For the evaluation we've used two following criteria: a quality of the fitting of atmospheric spectra measured at the Ural Atmospheric Station (UAS, Kourovka) with the high-resolution Fourier-transform infrared spectrometer and an agreement between the retrieved HDO/H2O relative concentration ratios in the atmospheric column and the results of the simulation of the isotopic general circulation model ECHAM5-wiso (validated for Kourovka region).

  16. EDITORIAL: The global atmospheric water cycle

    NASA Astrophysics Data System (ADS)

    Bengtsson, Lennart

    2010-06-01

    Water vapour plays a key role in the Earth's energy balance. Almost 50% of the absorbed solar radiation at the surface is used to cool the surface, through evaporation, and warm the atmosphere, through release of latent heat. Latent heat is the single largest factor in warming the atmosphere and in transporting heat from low to high latitudes. Water vapour is also the dominant greenhouse gas and contributes to a warming of the climate system by some 24°C (Kondratev 1972). However, water vapour is a passive component in the troposphere as it is uniquely determined by temperature and should therefore be seen as a part of the climate feedback system. In this short overview, we will first describe the water on planet Earth and the role of the hydrological cycle: the way water vapour is transported between oceans and continents and the return of water via rivers to the oceans. Generally water vapour is well observed and analysed; however, there are considerable obstacles to observing precipitation, in particular over the oceans. The response of the hydrological cycle to global warming is far reaching. Because different physical processes control the change in water vapour and evaporation/precipitation, this leads to a more extreme distribution of precipitation making, in general, wet areas wetter and dry areas dryer. Another consequence is a transition towards more intense precipitation. It is to be expected that the changes in the hydrological cycle as a consequence of climate warming may be more severe that the temperature changes. Water on planet Earth The total amount of available water on the Earth amounts to some 1.5 x 109 km3. The dominant part of this, 1.4 x 109 km3, resides in the oceans. About 29 x 106 km3 are locked up in land ice and glaciers and some 15 x 106 km3 are estimated to exist as groundwater. If all land ice and glaciers were to melt the sea level would rise some 80 m (Baumgartner and Reichel 1975). 13 x 103 km3 of water vapour are found in the

  17. The measurement of water vapour transfer rate through clothing system with air gap between layers

    NASA Astrophysics Data System (ADS)

    Oh, Ae-Gyeong

    2008-02-01

    The experiments described in this paper are designed to test the water vapour transfer rates through outdoor clothing system with air gap between layers under conditions more closely actual wear. It was adopted distance of 5 mm to ensure no disturbance of the air gap thickness between layers throughout the measurement period with all fabrics. The results have indicated that the water vapour transfer rates of clothing system decrease very slightly with time, it is shown that they approached nearly equilibrium state throughout the experiment. It is revealed that the water vapour transfer rates of the clothing system were ordered into groups determined by the type of waterproof breathable fabric as a shell layer being ordered.

  18. VAPOUR IS THE PRINCIPAL SOURCE OF WATER IMBIBED BY SEED IN UNSATURATED SOILS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The assumption that seeds imbibe most of the water they require for germination as liquid through seed-to-soil contact has been a dominant factor in germination research and seeding technology. Under most conditions seed is exposed to water vapour during imbibition, but the relative contributions of...

  19. Recent decadal trends in Iberian water vapour: GPS analysis and WRF process study

    NASA Astrophysics Data System (ADS)

    Miranda, Pedro M. A.; Nogueira, Miguel; Semedo, Alvaro; Benevides, Pedro; Catalao, Joao; Costa, Vera

    2016-04-01

    A 24-year simulation of the recent Iberian climate, using the WRF model at 9km resolution forced by ERA-Interim reanalysis (1989-2012), is analysed for the decadal evolution of the upwelling forcing coastal wind and for column integrated Precipitable water vapour (PWV). Results indicate that, unlike what was found by Bakun et al. (2009) for the Peruvian region, a statistically significant trend in the upwelling favourable (northerly) wind has been accompanied by a corresponding decrease in PWV, not only inland but also over the coastal waters. Such increase is consistent with a reinforced northerly coastal jet in the maritime boundary layer contributing to atmospheric Ekman pumping of dry continental air into the coastal region. Diagnostics of the prevalence of the Iberian thermal low following Hoinka and Castro (2003) also show a positive trend in its frequency during an extended summer period (April to September). These results are consistent with recent studies indicating an upward trend in the frequency of upwelling in SW Iberia (Alves and Miranda 2013), and may be relevant for climate change applications as an increase in coastal upwelling (Miranda et al 2013) may lead to substantial regional impacts in the subtropics. The same analysis with ERA-Interim reanalysis data, which was used to force the WRF simulations, does not reveal the same signal in PWV, and indeed correlates poorly with the GPS observations, indicating that the data assimilation process makes the water vapour data in reanalysis unusable for climate change purposes. The good correlation between the WRF simulated data and GPS observations allow for a detailed analysis of the processes involved in the evolution of the PWV field. Akcnowledgements: Study done within FCT Grant RECI/GEO-MET/0380/2012, financially supported by FCT Grant UID/ GEO/50019/2013-IDL Alves JMR, Miranda PMA (2013) Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses, Tellus A 2013, http

  20. How accurately can we measure the water vapour content with astronomical spectra?

    NASA Astrophysics Data System (ADS)

    Kausch, Wolfgang; Noll, Stefan; Smette, Alain; Kimeswenger, Stefan; Kerber, Florian; Jones, Amy M.; Szyszka, Cezary; Unterguggenberger, Stefanie

    2014-05-01

    Light from astronomical objects unavoidably has to pass through the Earth's atmosphere when being observed by ground-based telescopes. Thus, the fingerprint of the atmospheric state at the time of the observation is present in any spectrum taken by astronomical spectrographs due to absorption and emission arising in the atmosphere. The Very Large Telescope (VLT), operated by the European Southern Observatory, is one of the world's largest telescope facilities located at Cerro Paranal in the Chilean Atacama Desert offering a wide selection of various instruments. One of the most versatile instruments is X-Shooter. This medium resolution Echelle spectrograph covers the entire wavelength regime from 0.3 to 2.5 μm and is mounted on one of the 8m-class telescopes of the VLT. Due to its versatility, it is widely used, which leads to a good temporal coverage. We have recently developed the software package molecfit, a tool used to model and correct for atmospheric absorption lines visible in astronomical spectra. It is based on the radiative transfer code LBLRTM, the HITRAN line parameter database, the GDAS atmospheric profiles, and local meteorological data. A by-product is the determination of the amount of precipitable water vapour (PWV) above the observatory, as well as several other molecules, including CO2. In this poster, we investigate the accuracy of this method. We have used a set of X-Shooter spectra of so-called telluric standard stars, which are hot and bright stars showing nearly no intrinsic spectral features in the near infrared regime. Thus, most absorption features present in these spectra are related to the absorption arising in the Earth's atmosphere. For each spectrum, we have determined the PWV with our molecfit code and compared it with direct measurements achieved by the LHATPRO radiometer recently installed at Cerro Paranal. Therefore we have extended the results obtained by Kerber et al. (2012, Proc. SPIE, 8446) on a long time scale. Due to the

  1. The radiative impact of major volcanic eruptions on stratospheric water vapour

    NASA Astrophysics Data System (ADS)

    Löffler, Michael; Brinkop, Sabine; Jöckel, Patrick

    2016-04-01

    Volcanic eruptions can have significant impact on the earth's weather and climate system. Besides the subsequent tropospheric changes also the stratosphere is influenced by large eruptions. Here changes in stratospheric water vapour after the two major volcanic eruptions of El Chichón in Mexico in 1982 and Mount Pinatubo on the Philippines in 1991 are investigated with chemistry-climate model simulations. This study is based on two simulations with specified dynamics of the EMAC model, performed within the Earth System Chemistry integrated Modelling (ESCiMo) project, of which only one includes the volcanic forcing through prescribed aerosol optical properties. The results show a significant increase in stratospheric water vapour after the eruptions, resulting from increased heating rates and the subsequent changes in stratospheric and tropopause temperatures in the tropics. The tropical vertical advection and the South Asian summer monsoon are identified as important sources for the additional water vapour in the stratosphere. Additionally, volcanic influences on the tropospheric water vapour and ENSO are evident.

  2. Mars atmospheric water

    NASA Technical Reports Server (NTRS)

    Clancy, R. T.; Grossman, A. W.; Muhleman, D. O.

    1992-01-01

    We indicate the Dec. 3-4 spectrum averaged over the morning limb of Mars. Two synthetic spectra indicate the expected line emission for 3 precipitable microns of water with a uniform vertical distribution (dotted) and a vertical distribution in which water decreases rapidly above 20 km altitude if Mars atmospheric temperatures are approximately 20 K cooler than implied by the Viking Infrared Thermal Mapping (IRTM) and lander descent observations. Such cooler atmospheric temperatures have been argued on the basis of ground-based microwave observations of Mars atmospheric CO. Our 3 pr micron column abundance for water can be compared to the global value of approximately 6 pr microns, observation for the same season with the Viking MAWD experiment in 1977. We will investigate the latitude and diurnal variations when the data corresponding to the second day of observations are reduced. We also plan to compare these VLA water observations with a very complementary set of Hubble Space Telescope ozone observations. Ultraviolet (220-330 nm) spectra and imates of Mars were obtained on Dec. 13 1990 as part of a general Mars observing program with the Hubble Space Telescope.

  3. Seasonal comparisons of retrieved temperature and water vapour between ACE-FTS and COSMIC.

    NASA Astrophysics Data System (ADS)

    Olsen, Kevin; Toon, Geoff; Boone, Chris; Strong, Kim

    2015-04-01

    Motivated by the selection of a high-resolution solar occultation Fourier transform spectrometer (FTS) to fly to Mars, we developed new algorithms for retrieving vertical profiles of temperature and pressure from spectra. We present temperature retrieval results from remote sensing spectra collected by the Canadian Space Agency's (CSA) Atmospheric Chemistry Experiment (ACE), which recently celebrated its tenth year in orbit. ACE utilizes a high-resolution (0.02 cm-1) Fourier Transform Spectrometer (FTS) operating between 750-4400 cm-1 in limb-scanning mode using the sun as a light source (solar occultation). We compare our retrieved profiles to those of the ACE Science Team and the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC). COSMIC is a group of six small satellites that use signals from GPS satellites to measure water vapour pressure an temperature via radio occultation. We have collected five sets of zonal and seasonal coincidences with a tight criteria of 150 km and 1 hour. Retrieved H2O profiles from both satellites will also be presented for these data sets. Compared to ACE, we can achieve T differences between 1 and 5 K below 50 km, perform less well between 50 and 100 km. Compared to COSMIC, available below 40 km, we perform similarly, while the ACE retrievals are in close agreement.

  4. EDITORIAL: The global atmospheric water cycle

    NASA Astrophysics Data System (ADS)

    Bengtsson, Lennart

    2010-06-01

    Water vapour plays a key role in the Earth's energy balance. Almost 50% of the absorbed solar radiation at the surface is used to cool the surface, through evaporation, and warm the atmosphere, through release of latent heat. Latent heat is the single largest factor in warming the atmosphere and in transporting heat from low to high latitudes. Water vapour is also the dominant greenhouse gas and contributes to a warming of the climate system by some 24°C (Kondratev 1972). However, water vapour is a passive component in the troposphere as it is uniquely determined by temperature and should therefore be seen as a part of the climate feedback system. In this short overview, we will first describe the water on planet Earth and the role of the hydrological cycle: the way water vapour is transported between oceans and continents and the return of water via rivers to the oceans. Generally water vapour is well observed and analysed; however, there are considerable obstacles to observing precipitation, in particular over the oceans. The response of the hydrological cycle to global warming is far reaching. Because different physical processes control the change in water vapour and evaporation/precipitation, this leads to a more extreme distribution of precipitation making, in general, wet areas wetter and dry areas dryer. Another consequence is a transition towards more intense precipitation. It is to be expected that the changes in the hydrological cycle as a consequence of climate warming may be more severe that the temperature changes. Water on planet Earth The total amount of available water on the Earth amounts to some 1.5 x 109 km3. The dominant part of this, 1.4 x 109 km3, resides in the oceans. About 29 x 106 km3 are locked up in land ice and glaciers and some 15 x 106 km3 are estimated to exist as groundwater. If all land ice and glaciers were to melt the sea level would rise some 80 m (Baumgartner and Reichel 1975). 13 x 103 km3 of water vapour are found in the

  5. Water vapour variability during Indian monsoon over Trivandrum observed using Microwave Radiometer and GPS

    NASA Astrophysics Data System (ADS)

    Raju, Suresh C.; Krishna Moorthy, K.; Ramachandran Pillai, Renju; Uma, K. N.; Saha, Korak

    2012-07-01

    The Indian summer monsoon is a highly regular synoptic event, providing most of the annual rainfall received over the sub-continent. Trivandrum, at the southwestern tip of Indian peninsula, is considered as the gate way of Indian monsoon, with its climatological onset on June 01. During this season, the region, experiences large seasonal variation in water vapor, rain fall and wind (speed and direction) in the troposphere. The variability in water vapor and wind information are the vital parameters in forecasting the onset of monsoon. This study focuses on water vapor measurements over the tropical coastal station Trivandrum (8.5oN & 76.9oE) using microwave techniques and the analyses with an effort to link the seasonal variability of water vapor with the onset of monsoon. At Trivandrum a hyper-spectral microwave radiometer profiler (MRP) and a Triple-frequency global positioning system receiver (GPS) have been in regular operation since April 2010. A station-dependent simple empirical relation suitable for the equatorial atmospheric condition is formulated to map the nonhydrostatic component of GPS tropospheric delay to the PWV, based on the columnar water vapor estimated from the multi-year daily radiosonde ascends from Trivandrum. A trained artificial neural network (ANN) with climatological atmospheric data of Trivandrum, is employed to derive the water vapor from the MRP brightness temperature measurements. The accuracy, reliability and consistency of PWV measurements over the tropical coastal station from these two independent instruments are assessed by comparing PWV derived from MRP and GPS measurements which resulted an rms deviation of <1.2mm (with correlation coefficient of ~0.98). This confirms the PWV derived over Trivandrum from microwave measurements are accurate even during the monsoon period in the presence of clouds and rain. PWV from microwave radiometer measurements for more than two years are used to study the water vapour variability during

  6. Leidenfrost vapour layer moderation of the drag crisis and trajectories of superhydrophobic and hydrophilic spheres falling in water.

    PubMed

    Vakarelski, Ivan U; Chan, Derek Y C; Thoroddsen, Sigurdur T

    2014-08-21

    We investigate the dynamic effects of a Leidenfrost vapour layer sustained on the surface of heated steel spheres during free fall in water. We find that a stable vapour layer sustained on the textured superhydrophobic surface of spheres falling through 95 °C water can reduce the hydrodynamic drag by up to 75% and stabilize the sphere trajectory for the Reynolds number between 10(4) and 10(6), spanning the drag crisis in the absence of the vapour layer. For hydrophilic spheres under the same conditions, the transition to drag reduction and trajectory stability occurs abruptly at a temperature different from the static Leidenfrost point. The observed drag reduction effects are attributed to the disruption of the viscous boundary layer by the vapour layer whose thickness depends on the water temperature. Both the drag reduction and the trajectory stabilization effects are expected to have significant implications for development of sustainable vapour layer based technologies. PMID:24849267

  7. ZWD2PW - A Global Model for the Conversion of Zenith Wet Delays to Precipitable Water Vapour

    NASA Astrophysics Data System (ADS)

    Rozsa, S.; Juni, I.

    2015-12-01

    Water vapor plays an important role as a basic climate variable in the thermodynamics and dynamics of the storm systems at the atmosphere and in the hydrological cycle on the local, regional and global scales. Recently the precipitable water vapour content (PW) is estimated using the zenith wet delay (ZWD) derived from ground-based GNSS data. This study introduces a new global model for the conversion of zenith wet delays (ZWD) obtained from GNSS observations to precipitable water vapour (PW). The model was developed using a monthly mean ERA-Interim global numerical weather model datasets of 14 years between 2001-2014. The 1°×1° global grids of 37 pressure levels of temperature, relative humidity and the geopotential were collected from the ECMWF and the ZWD and PW values as well as the mean temperature of the water vapour (Tm) were calculated for each gridpoint. Afterwards a direct and an indirect method was used to derive the global grids of the parameters used for the computation of the conversion factor between ZWD and PW. In the indirect method the conversion factor is computed as a function of the mean temperature of water vapour, where Tm is estimated as an empirical function of the surface temperature. The direct method models the conversion factor as a polynomial function of the surface temperature. The global grids of the model parameters were derived for both of the approaches. The results show that the global climate strongly affects the parameters of the conversion formulae. It is well known that the most widely used conversion formulae were derived from North American and European radiosonde observations only. Our results show that the relative differences in terms of the conversion factors reach the level of 10%, which can lead a similar relative error in PW estimation. The ZWD2PW model is also validated by a global set of radiosonde observations and the results show that it can be efficiently used for the conversion of ZWD to PW globally

  8. Simulation of the isotopic composition of stratospheric water vapour - Part 2: Investigation of HDO / H2O variations

    NASA Astrophysics Data System (ADS)

    Eichinger, R.; Jöckel, P.; Lossow, S.

    2015-06-01

    Studying the isotopic composition of water vapour in the lower stratosphere can reveal the driving mechanisms of changes in the stratospheric water vapour budget and therefore help to explain the trends and variations of stratospheric water vapour during recent decades. We equipped a global chemistry climate model with a description of the water isotopologue HDO, comprising its physical and chemical fractionation effects throughout the hydrological cycle. We use this model to improve our understanding of the processes which determine the patterns in the stratospheric water isotope composition and in the water vapour budget itself. The link between the water vapour budget and its isotopic composition in the tropical stratosphere is presented through their correlation in a simulated 21-year time series. The two quantities depend on the same processes; however, they are influenced with different strengths. A sensitivity experiment shows that fractionation effects during the oxidation of methane have a damping effect on the stratospheric tape recorder signal in the water isotope ratio. Moreover, the chemically produced high water isotope ratios overshadow the tape recorder in the upper stratosphere. Investigating the origin of the boreal-summer signal of isotopically enriched water vapour reveals that in-mixing of old stratospheric air from the extratropics and the intrusion of tropospheric water vapour into the stratosphere complement each other in order to create the stratospheric isotope ratio tape recorder signal. For this, the effect of ice lofting in monsoon systems is shown to play a crucial role. Furthermore, we describe a possible pathway of isotopically enriched water vapour through the tropopause into the tropical stratosphere.

  9. Validation of GOME-2/Metop total column water vapour with ground-based and in situ measurements

    NASA Astrophysics Data System (ADS)

    Kalakoski, Niilo; Kujanpää, Jukka; Sofieva, Viktoria; Tamminen, Johanna; Grossi, Margherita; Valks, Pieter

    2016-04-01

    The total column water vapour product from the Global Ozone Monitoring Experiment-2 on board Metop-A and Metop-B satellites (GOME-2/Metop-A and GOME-2/Metop-B) produced by the Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) is compared with co-located radiosonde observations and global positioning system (GPS) retrievals. The validation is performed using recently reprocessed data by the GOME Data Processor (GDP) version 4.7. The time periods for the validation are January 2007-July 2013 (GOME-2A) and December 2012-July 2013 (GOME-2B). The radiosonde data are from the Integrated Global Radiosonde Archive (IGRA) maintained by the National Climatic Data Center (NCDC). The ground-based GPS observations from the COSMIC/SuomiNet network are used as the second independent data source. We find a good general agreement between the GOME-2 and the radiosonde/GPS data. The median relative difference of GOME-2 to the radiosonde observations is -2.7 % for GOME-2A and -0.3 % for GOME-2B. Against the GPS, the median relative differences are 4.9 % and 3.2 % for GOME-2A and B, respectively. For water vapour total columns below 10 kg m-2, large wet biases are observed, especially against the GPS retrievals. Conversely, at values above 50 kg m-2, GOME-2 generally underestimates both ground-based observations.

  10. Comparison of GOME-2/Metop total column water vapour with ground-based and in situ measurements

    NASA Astrophysics Data System (ADS)

    Kalakoski, N.; Kujanpää, J.; Sofieva, V.; Tamminen, J.; Grossi, M.; Valks, P.

    2014-12-01

    Total column water vapour product from the Global Ozone Monitoring Experiment-2 on board Metop-A and Metop-B satellites (GOME-2/Metop-A and GOME-2/Metop-B) produced by the Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) is compared with co-located radiosonde and Global Positioning System (GPS) observations. The comparisons are performed using recently reprocessed data by the GOME Data Processor (GDP) version 4.7. The comparisons are performed for the period of January 2007-July 2013 (GOME-2A) and from December 2012 to July 2013 (GOME-2B). Radiosonde data are from the Integrated Global Radiosonde Archive (IGRA) maintained by National Climatic Data Center (NCDC) and screened for soundings with incomplete tropospheric column. Ground-based GPS observations from COSMIC/SuomiNet network are used as the second independent data source. Good general agreement between GOME-2 and the ground-based observations is found. The median relative difference of GOME-2 to radiosonde observations is -2.7% for GOME-2A and -0.3% for GOME-2B. Against GPS observations, the median relative differences are 4.9 and 3.2% for GOME-2A and B, respectively. For water vapour total columns below 10 kg m-2, large wet biases are observed, especially against GPS observations. Conversely, at values above 50 kg m-2, GOME-2 generally underestimates both ground-based observations.

  11. Validation of two independent retrievals of SCIAMACHY water vapour columns using radiosonde data

    NASA Astrophysics Data System (ADS)

    du Piesanie, A.; Piters, A. J. M.; Aben, I.; Schrijver, H.; Wang, P.; Noël, S.

    2013-10-01

    Two independently derived SCIAMACHY total water vapour column (WVC) products are compared with integrated water vapour data calculated from radiosonde measurements, and with each other. The two SCIAMACHY WVC products are retrieved with two different retrieval algorithms applied in the visible and short-wave infrared wavelength regions respectively. The first SCIAMACHY WVC product used in the comparison is ESA's level 2 version 5.01 WVC product derived with the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS) retrieval algorithm applied in the visible wavelength range (SCIAMACHY-ESA). The second SCIAMACHY WVC product is derived using the iterative maximum likelihood method (IMLM) in the short-wave infrared wavelength range and developed by Netherlands Institute for Space Research (SCIAMACHY-IMLM). Both SCIAMACHY WVC products are compared with collocated water vapour amounts determined from daily relative humidity radiosonde measurements obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) radiosonde network. The SCIAMACHY-ESA WVC product is compared with radiosonde-derived WVC amounts for an 18-month period from February 2010 to mid-August 2011, and the SCIAMACHY-IMLM WVC amounts are compared with radiosonde WVC amounts for the two individual years of 2004 and 2009. In addition the WVC amounts from SCIAMACHY-ESA and SCIAMACHY-IMLM are also compared with each other for a 1-month period for June 2009. The AMC-DOAS method used to retrieve SCIAMACHY-ESA WVC is able to correct for water vapour present below the clouds and can be used during cloudy conditions over both land and ocean surfaces. Results indicate a good agreement between the WVC amounts of SCIAMACHY-ESA and that of radiosondes, with a mean difference of -0.32 g cm-2 for all collocated cases. Overall the SCIAMACHY-ESA WVC amounts are smaller than the radiosonde WVC amounts, especially over oceans. For cloudy conditions the WVC bias has a clear dependence on

  12. Insight from ozone and water vapour on transport in the tropical tropopause layer (TTL)

    NASA Astrophysics Data System (ADS)

    Ploeger, F.; Fueglistaler, S.; Grooß, J.-U.; Günther, G.; Konopka, P.; Liu, Y. S.; Müller, R.; Ravegnani, F.; Schiller, C.; Ulanovski, A.; Riese, M.

    2011-01-01

    We explore the potential of ozone observations to constrain transport processes in the tropical tropopause layer (TTL), and contrast it with insights that can be obtained from water vapour. Global fields from Halogen Occultation Experiment (HALOE) and in-situ observations are predicted using a backtrajectory approach that captures advection, instantaneous freeze-drying and photolytical ozone production. Two different representations of transport (kinematic and diabatic 3-month backtrajectories based on ERA-Interim data) are used to evaluate the sensitivity to differences in transport. Results show that mean profiles and seasonality of both tracers can be reasonably reconstructed. Water vapour predictions are similar for both transport representations, but predictions for ozone are systematically higher for kinematic transport. Compared to global HALOE observations, the diabatic model prediction underestimates the vertical ozone gradient. Comparison of the kinematic prediction with observations obtained during the tropical SCOUT-O3 campaign shows a large high bias above 390 K potential temperature. We show that ozone predictions and vertical dispersion of the trajectories are highly correlated, rendering ozone an interesting tracer for aspects of transport to which water vapour is not sensitive. We show that dispersion and mean upwelling have similar effects on ozone profiles, with slower upwelling and larger dispersion both leading to higher ozone concentrations. Analyses of tropical upwelling based on mean transport characteristics, and model validation have to take into account this ambiguity between tropical ozone production and in-mixing from the stratosphere. In turn, ozone provides constraints on transport in the TTL and lower stratosphere that cannot be obtained from water vapour.

  13. Computational implementation of interfacial kinetic transport theory for water vapour transport in porous media

    PubMed Central

    Albaalbaki, Bashar; Hill, Reghan J.

    2014-01-01

    A computational framework is developed for applying interfacial kinetic transport theory to predict water vapour permeability of porous media. Modified conservation equations furnish spatially periodic disturbances from which the average flux and, thus, the effective diffusivity is obtained. The equations are solved exactly for a model porous medium comprising parallel layers of gas and solid with arbitrary solid volume fraction. From the microscale effective diffusivity, a two-point boundary-value problem is solved at the macroscale to furnish the water vapour transport rate in membranes subjected to a finite RH differential. Then, the microscale model is implemented using a computational framework (extended finite-element method) to examine the role of particle size, aspect ratio and positioning for periodic arrays of aligned super-ellipses (model particles that pack with high density). We show that the transverse water vapour permeability can be reduced by an order of magnitude only when fibres with a high-aspect ratio cross section are packed in a periodic staggered configuration. Maximum permeability is achieved at intermediate micro-structural length scales, where gas-phase diffusion is enhanced by surface diffusion, but not limited by interfacial-exchange kinetics. The two-dimensional computations demonstrated here are intended to motivate further efforts to develop efficient computational solutions for realistic three-dimensional microstructures. PMID:24399918

  14. Atomic-scale Studies of Uranium Oxidation and Corrosion by Water Vapour

    PubMed Central

    Martin, T. L.; Coe, C.; Bagot, P. A. J.; Morrall, P.; Smith, G. D. W; Scott, T.; Moody, M. P.

    2016-01-01

    Understanding the corrosion of uranium is important for its safe, long-term storage. Uranium metal corrodes rapidly in air, but the exact mechanism remains subject to debate. Atom Probe Tomography was used to investigate the surface microstructure of metallic depleted uranium specimens following polishing and exposure to moist air. A complex, corrugated metal-oxide interface was observed, with approximately 60 at.% oxygen content within the oxide. Interestingly, a very thin (~5 nm) interfacial layer of uranium hydride was observed at the oxide-metal interface. Exposure to deuterated water vapour produced an equivalent deuteride signal at the metal-oxide interface, confirming the hydride as originating via the water vapour oxidation mechanism. Hydroxide ions were detected uniformly throughout the oxide, yet showed reduced prominence at the metal interface. These results support a proposed mechanism for the oxidation of uranium in water vapour environments where the transport of hydroxyl species and the formation of hydride are key to understanding the observed behaviour. PMID:27403638

  15. Atomic-scale Studies of Uranium Oxidation and Corrosion by Water Vapour

    NASA Astrophysics Data System (ADS)

    Martin, T. L.; Coe, C.; Bagot, P. A. J.; Morrall, P.; Smith, G. D. W.; Scott, T.; Moody, M. P.

    2016-07-01

    Understanding the corrosion of uranium is important for its safe, long-term storage. Uranium metal corrodes rapidly in air, but the exact mechanism remains subject to debate. Atom Probe Tomography was used to investigate the surface microstructure of metallic depleted uranium specimens following polishing and exposure to moist air. A complex, corrugated metal-oxide interface was observed, with approximately 60 at.% oxygen content within the oxide. Interestingly, a very thin (~5 nm) interfacial layer of uranium hydride was observed at the oxide-metal interface. Exposure to deuterated water vapour produced an equivalent deuteride signal at the metal-oxide interface, confirming the hydride as originating via the water vapour oxidation mechanism. Hydroxide ions were detected uniformly throughout the oxide, yet showed reduced prominence at the metal interface. These results support a proposed mechanism for the oxidation of uranium in water vapour environments where the transport of hydroxyl species and the formation of hydride are key to understanding the observed behaviour.

  16. Atomic-scale Studies of Uranium Oxidation and Corrosion by Water Vapour.

    PubMed

    Martin, T L; Coe, C; Bagot, P A J; Morrall, P; Smith, G D W; Scott, T; Moody, M P

    2016-01-01

    Understanding the corrosion of uranium is important for its safe, long-term storage. Uranium metal corrodes rapidly in air, but the exact mechanism remains subject to debate. Atom Probe Tomography was used to investigate the surface microstructure of metallic depleted uranium specimens following polishing and exposure to moist air. A complex, corrugated metal-oxide interface was observed, with approximately 60 at.% oxygen content within the oxide. Interestingly, a very thin (~5 nm) interfacial layer of uranium hydride was observed at the oxide-metal interface. Exposure to deuterated water vapour produced an equivalent deuteride signal at the metal-oxide interface, confirming the hydride as originating via the water vapour oxidation mechanism. Hydroxide ions were detected uniformly throughout the oxide, yet showed reduced prominence at the metal interface. These results support a proposed mechanism for the oxidation of uranium in water vapour environments where the transport of hydroxyl species and the formation of hydride are key to understanding the observed behaviour. PMID:27403638

  17. Isotopes in the Arctic atmospheric water cycle

    NASA Astrophysics Data System (ADS)

    Bonne, Jean-Louis; Werner, Martin; Meyer, Hanno; Kipfstuhl, Sepp; Rabe, Benjamin; Behrens, Melanie; Schönicke, Lutz; Steen Larsen, Hans Christian; Masson-Delmotte, Valérie

    2016-04-01

    The ISO-ARC project aims at documenting the Arctic atmospheric hydrological cycle, by assessing the imprint of the marine boundary conditions (e.g. temperature variations, circulation changes, or meltwater input) to the isotopic composition of the atmospheric water cycle (H218O and HDO) with a focus on North Atlantic and Arctic oceans. For this purpose, two continuous monitoring water vapour stable isotopes cavity ring-down spectrometers have been installed in July 2015: on-board the Polarstern research vessel and in the Siberian Lena delta Samoylov research station (N 72° 22', E 126° 29'). The Polarstern measurements cover the summer 2015 Arctic campaign from July to mid-October, including six weeks in the Fram Strait region in July- August, followed by a campaign reaching the North Pole and a transect from the Norwegian Sea to the North Sea. These vapour observations are completed by water isotopic measurements in samples from the surface ocean water for Polarstern and from precipitation in Samoylov and Tiksi (120 km south-east of the station). A custom-made designed automatic calibration system has been implemented in a comparable manner for both vapour instruments, based on the injection of different liquid water standards, which are completely vaporised in dry air at high temperature. Subsequent humidity level can be adjusted from 2000 to at least 30000 ppm. For a better resilience, an independent calibration system has been added on the Samoylov instrument, allowing measurements of one standard at humidity levels ranging from 2000 to 15000 ppm: dry air is introduced in a tank containing a large amount of liquid water standard, undergoing evaporation under a controlled environment. The measurement protocol includes an automatic calibration every 25 hours. First instrument characterisation experiments depict a significant isotope-humidity effect at low humidity, dependant on the isotopic composition of the standard. For ambient air, our first isotope

  18. Understanding climatic controls on Svalbard water vapour and precipitation isotopic composition

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, Valérie; Steen-Larsen, Hans-Christian; Zanetti, Nathalie; Cattani, Olivier; Maturilli, Marion; Debatin, Siegrid; Terzer, Stefan; Bonne, Jean-Louis; Schneider, Matthias

    2015-04-01

    We investigate the meteorological and climatic controls on the isotopic composition of vapour and precipitation at Ny Alesund, Svalbard. This is based on the IAEA database of monthly precipitation isotopic composition data spanning 1993-2012 as well as new measurements performed using a PICARRO CRDS analyzer deployed since June 2014 at Ny Alesund. The precipitation data depict a strong decoupling between oxygen 18 and temperature at the seasonal scale and for monthly anomalies. While a relationship is observed between winter precipitation isotopic composition and temperature, this disappears during summer, at the inter-annual scale. Moreover, the deuterium versus oxygen 18 relationship depicts different meteoric water lines in winter and summer, consistent with the strong seasonal cycle of deuterium excess, and indicating shifts in moisture origin. The continuous water vapour data (investigated from July to December 2014 so far) show in contrast a tight relationship between hourly oxygen 18 data and surface temperature and humidity, as well as strong antiphase between deuterium excess and oxygen 18. No significant diurnal variability is observed. We show how precipitation intermittency strongly alters the sampling provided by precipitation data and distorts the relationship with local temperature. The surface vapour deuterium data are compared with FTIR retrievals. The importance of changes in air mass origins is also assessed by comparison with moisture backtrajectories.

  19. Characterization of sorption properties of selected soils from Lublin region by using water vapour adsorption method

    NASA Astrophysics Data System (ADS)

    Skic, Kamil; Boguta, Patrycja; Sokołowska, Zofia

    2016-04-01

    *The studies were carried out within the framework of a research project. The project was financed from funds of National Science Center on the base of decision number DEC-2013/11/D/NZ9/02545 Among many methods proposed to study sorption properties of soils an analysis of adsorption/ desorption isotherm is probably the easiest and most convenient one. It characterizes both quantity and quality of mineral and organic components and also their physical and physicochemical properties. The main aim of this study is comparison of sorption properties of selected Polish soils by using water vapour adsorption method. Samples were taken from the depth of 0-20 cm, from the Lublin region, eastern Poland. Soils were selected on the basis of their different physicochemical properties and were classified as: Haplic Fluvisol, Haplic Chernozem, Mollic Gleysol, Rendzic Phaeozem, Stagnic Luvisol, Haplic Cambisol (WG WRB 2006). Data taken from experimental adsorption isotherms were used to determine parameters of monolayer capacity, specific surface area and the total amount of vapour adsorbed at relative pressure of 0.974. Obtained adsorption and desorption isotherms reviled that adsorbate molecules interacted with the soil particles in different extent. Similar monolayer capacity was observed for Haplic Fluvisol, Haplic Chernozem and Stagnic Luvisol, while for Mollic Gleysol was more than 4 times higher. Mollic Gleysol was also characterized by highest values of specific surface area as well as quantity of adsorbed vapour at relative pressure of 0.974. Higher sorption was caused by presence of soil colloids which contains functional groups of a polar nature (mainly hydroxyls, phenolic and carboxyls). These groups similarly to silicates, oxides, hydratable cations as well as electric charge form adsorption centres for water vapour molecules.

  20. Warm water vapour in the sooty outflow from a luminous carbon star.

    PubMed

    Decin, L; Agúndez, M; Barlow, M J; Daniel, F; Cernicharo, J; Lombaert, R; De Beck, E; Royer, P; Vandenbussche, B; Wesson, R; Polehampton, E T; Blommaert, J A D L; De Meester, W; Exter, K; Feuchtgruber, H; Gear, W K; Gomez, H L; Groenewegen, M A T; Guélin, M; Hargrave, P C; Huygen, R; Imhof, P; Ivison, R J; Jean, C; Kahane, C; Kerschbaum, F; Leeks, S J; Lim, T; Matsuura, M; Olofsson, G; Posch, T; Regibo, S; Savini, G; Sibthorpe, B; Swinyard, B M; Yates, J A; Waelkens, C

    2010-09-01

    The detection of circumstellar water vapour around the ageing carbon star IRC +10216 challenged the current understanding of chemistry in old stars, because water was predicted to be almost absent in carbon-rich stars. Several explanations for the water were postulated, including the vaporization of icy bodies (comets or dwarf planets) in orbit around the star, grain surface reactions, and photochemistry in the outer circumstellar envelope. With a single water line detected so far from this one carbon-rich evolved star, it is difficult to discriminate between the different mechanisms proposed. Here we report the detection of dozens of water vapour lines in the far-infrared and sub-millimetre spectrum of IRC +10216 using the Herschel satellite. This includes some high-excitation lines with energies corresponding to approximately 1,000 K, which can be explained only if water is present in the warm inner sooty region of the envelope. A plausible explanation for the warm water appears to be the penetration of ultraviolet photons deep into a clumpy circumstellar envelope. This mechanism also triggers the formation of other molecules, such as ammonia, whose observed abundances are much higher than hitherto predicted. PMID:20811453

  1. Electron drift velocities in He and water mixtures: Measurements and an assessment of the water vapour cross-section sets

    SciTech Connect

    Urquijo, J. de; Juárez, A. M.; Basurto, E.; Ness, K. F.; Robson, R. E.; White, R. D.; Brunger, M. J.

    2014-07-07

    The drift velocity of electrons in mixtures of gaseous water and helium is measured over the range of reduced electric fields 0.1–300 Td using a pulsed-Townsend technique. Admixtures of 1% and 2% water to helium are found to produce negative differential conductivity (NDC), despite NDC being absent from the pure gases. The measured drift velocities are used as a further discriminative assessment on the accuracy and completeness of a recently proposed set of electron-water vapour cross-sections [K. F. Ness, R. E. Robson, M. J. Brunger, and R. D. White, J. Chem. Phys. 136, 024318 (2012)]. A refinement of the momentum transfer cross-section for electron-water vapour scattering is presented, which ensures self-consistency with the measured drift velocities in mixtures with helium to within approximately 5% over the range of reduced fields considered.

  2. Total ozone column, water vapour and aerosol effects on erythemal and global solar irradiance in Marsaxlokk, Malta

    NASA Astrophysics Data System (ADS)

    Bilbao, Julia; Román, Roberto; Yousif, Charles; Mateos, David; de Miguel, Argimiro

    2014-12-01

    Observations of erythemal (UVER; 280-400 nm) and total solar shortwave irradiance (SW; 305-2800 nm), total ozone column (TOC), water vapour column (w), aerosol optical depth (AOD) and Ångström exponent (α) were carried out at Marsaxlokk, in south-east Malta. These measurements were recorded during a measurement campaign between May and October 2012, aimed at studying the influence of atmospheric compounds on solar radiation transfer through the atmosphere. The effects of TOC, AOD and w on UVER and SW (global, diffuse and direct) irradiance were quantified using irradiance values under cloud-free conditions at different fixed solar zenith angles (SZA). Results show that UVER (but not SW) irradiance correlates well with TOC. UVER variations ranged between -0.24% DU-1 and -0.32% DU-1 with all changes being statistically significant. Global SW irradiance varies with water vapour column between -2.44% cm-1 and -4.53% cm-1, these results proving statistically significant and diminishing when SZA increases. The irradiance variations range between 42.15% cm-1 and 20.30% cm-1 for diffuse SW when SZA varies between 20° and 70°. The effect of aerosols on global UVER is stronger than on global SW. Aerosols cause a UVER reduction of between 28.12% and 52.41% and a global SW reduction between 13.46% and 41.41% per AOD550 unit. Empirical results show that solar position plays a determinant role, that there is a negligible effect of ozone on SW radiation, and stronger attenuation by aerosol particles in UVER radiation.

  3. Localized sources of water vapour on the dwarf planet (1) Ceres.

    PubMed

    Küppers, Michael; O'Rourke, Laurence; Bockelée-Morvan, Dominique; Zakharov, Vladimir; Lee, Seungwon; von Allmen, Paul; Carry, Benoît; Teyssier, David; Marston, Anthony; Müller, Thomas; Crovisier, Jacques; Barucci, M Antonietta; Moreno, Raphael

    2014-01-23

    The 'snowline' conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Models suggest that some of the icy bodies may have migrated into the asteroid belt. Recent observations indicate the presence of water ice on the surface of some asteroids, with sublimation a potential reason for the dust activity observed on others. Hydrated minerals have been found on the surface of the largest object in the asteroid belt, the dwarf planet (1) Ceres, which is thought to be differentiated into a silicate core with an icy mantle. The presence of water vapour around Ceres was suggested by a marginal detection of the photodissociation product of water, hydroxyl (ref. 12), but could not be confirmed by later, more sensitive observations. Here we report the detection of water vapour around Ceres, with at least 10(26) molecules being produced per second, originating from localized sources that seem to be linked to mid-latitude regions on the surface. The water evaporation could be due to comet-like sublimation or to cryo-volcanism, in which volcanoes erupt volatiles such as water instead of molten rocks. PMID:24451541

  4. Stable isotopes in monsoon precipitation and water vapour in Nagqu, Tibet, and their implications for monsoon moisture

    NASA Astrophysics Data System (ADS)

    He, Siyuan; Richards, Keith

    2016-09-01

    Understanding climate variations over the Qinghai-Tibetan plateau has become essential because the high plateau sustains various ecosystems and water sources, and impacts on the Asian monsoon system. This paper provides new information from isotopic signals in meteoric water and atmospheric water vapour on the Qinghai-Tibetan Plateau using high frequency observation data over a relatively short period. The aim is to explore temporal moisture changes and annual variations at the onset and during the summer monsoon season at a transitional site with respect to the monsoon influence. Data show that high frequency and short period observations can reveal typical moisture changes from the pre-monsoon to the monsoon seasons (2010), and the large variation in isotopic signals in different years with respect to active/inactive periods during a mature phase of the monsoon (2011), especially inferring from the temporal changes in the d-excess of precipitation and its relationship with δ18O values, when higher d-excess is found in the pre-monsoon precipitation. In this transition zone on a daily basis, δ18O values in precipitation are controlled mainly by the amount of rainfall during the monsoon season, while temperature seems more important before the onset of monsoon. Furthermore, the "amount effect" is significant for night-time rain events. From comparison of signals in both the precipitation and water vapour, an inconsistent relationship between d-excess values suggests various moisture fluxes are active in a short period. The temporal pattern of isotopic signal change from the onset of the monsoon to the mature monsoon phase provides information about the larger circulation dynamics of the Asian monsoon.

  5. Influence of water and water vapour on the characteristics of KI treated HgI 2 detectors

    NASA Astrophysics Data System (ADS)

    Ponpon, J. P.; Amann, M.; Sieskind, M.

    After being cleaned using a potassium iodide solution in water followed by a water rinse, the surface of mercuric iodide is covered by a chemical complex identified as being KHgI 3·H 2O. This compound can adsorb large quantities of water and its electrical properties are strongly sensitive to water and water vapour. The consequences on the manufacturing and storing conditions (especially the relative humidity), of mercuric iodide-based devices are therefore of great concern. They are illustrated by the study of the electrical and spectrometric properties of HgI 2 nuclear radiation detectors.

  6. Water vapour is a pre-oviposition attractant for the malaria vector Anopheles gambiae sensu stricto

    PubMed Central

    2013-01-01

    Background To date no semiochemicals affecting the pre-oviposition behaviour of the malaria vector Anopheles gambiae sensu lato have been described. Water vapour must be the major chemical signal emanating from a potential larval habitat, and although one might expect that gravid An. gambiae s.l. detect and respond to water vapour in their search for an aquatic habitat, this has never been experimentally confirmed for this species. This study aimed to investigate the role of relative humidity or water vapour as a general cue for inducing gravid An. gambiae sensu stricto to make orientated movements towards the source. Methods Three experiments were carried out with insectary-reared An. gambiae s.s. One with unfed females and two with gravid females during their peak oviposition time in the early evening. First, unfed females and gravid females were tested separately in still air where a humidity difference was established between opposite ends of a WHO bioassay tube and mosquitoes released individually in the centre of the tube. Movement of mosquitoes to either low or high humidity was recorded. Additionally, gravid mosquitoes were released into a larger air-flow olfactometer and responses measured towards collection chambers that contained cups filled with water or empty cups. Results Unfed females equally dispersed in the small bioassay tubes to areas of high and low humidity (mean 50% (95% confidence interval (CI) 38-62%). In contrast, gravid females were 2.4 times (95% CI 1.3-4.7) more likely to move towards high humidity than unfed females. The results were even more pronounced in the airflow olfactometer. Gravid females were 10.6 times (95% CI 5.4-20.8) more likely to enter the chamber with water than a dry chamber. Conclusions Water vapour is a strong pre-oviposition attractant to gravid An. gambiae s.s. in still and moving air and is likely to be a general cue used by mosquitoes for locating aquatic habitats. PMID:24120083

  7. Localized sources of water vapour on the dwarf planet (1) Ceres

    NASA Astrophysics Data System (ADS)

    Küppers, M.; O'Rourke, L.; Bockelée-Morvan, D.; Zakharov, V.; Lee, S.; von Allmen, P.; Carry, B.; Teyssier, D.; Marston, A.; Müller, T.; Crovisier, J.; Barucci, A.; Moreno, R.

    2014-07-01

    We report the detection of water vapour on (1) Ceres, the first unambiguous discovery of water on an object in the asteroid main belt. Most of the water vapour stems from localized regions at low latitude, possibly from surface features known from adaptive-optics observations. We suggest either cometary-type sublimation from the near surface or cryovolcanism as the origin of the waver vapour [1]. The snowline conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Recently, the detection of dust emission from ''main-belt comets'' [2] and of hydration features and possible water ice absorption on some main-belt asteroids [3], together with theories of migration of small bodies in the solar system [4], cast some doubts on the classical picture. Ceres is thought to be differentiated into an icy core and a silicate mantle [5] and hydrated minerals were found on infrared spectra of its surface [6]. A marginal detection of OH, a photodissociation product of water was reported in 1991 [7], but questioned by later, more sensitive observations [8]. We observed Ceres with the Heterodyne Instrument for the Far Infrared (HIFI) [9] on the Herschel Space Observatory [10] in the context of the MACH 11 guaranteed time program and with a follow-up DDT program. The observations took place in Nov. 2011, Oct. 2012, and March 2013. We searched for the signature of water in the ground state line of ortho-water at 556.936 GHz. After a non- detection in the first observation, an absorption line is clearly visible in all other observations. In March 2013, water is detected in emission as well (at 3 sigma level). The production rate of water on Ceres is a few times 10^{26} s^{-1}. The signal from the water vapour from Ceres was found to be linearly polarized during some of the observations, with the absorption being stronger in the horizontal branch. The measured line-area ratio of up to 2.5 between H and V

  8. Experimental determination and theoretical framework of kinetic fractionation at the water vapour-ice interface at low temperature

    NASA Astrophysics Data System (ADS)

    Casado, Mathieu; Cauquoin, Alexandre; Landais, Amaelle; Israel, Dan; Orsi, Anaïs; Pangui, Edouard; Landsberg, Janek; Kerstel, Erik; Prie, Frederic; Doussin, Jean-François

    2016-02-01

    Water isotopes are commonly used for climate reconstruction from ice cores. The different heavy isotopes of water such as H218O, H217O or HDO give information about local temperature but also temperature and humidity of water vapour sources. Quantification of these parameters relies on the good knowledge of equilibrium and kinetic isotopic fractionation at each step of the water cycle. One of the strongest limitations when interpreting water isotopes in remote Antarctic ice cores is the formulation of the isotopic fractionation at solid condensation (vapour to ice). This classical formulation also implies a good knowledge of coefficients for equilibrium fractionation and water vapour diffusion in air as well as supersaturation in clouds. The uncertainties associated with these different parameters make the formulation of isotopic fractionation at solid condensation only empirical. Here, we make use (1) of recent development in the measurements of water isotopes in the water vapour through infra-red spectroscopy and (2) of the possibility to measure accurately 17O-excess of water to test the classical formulation and parameterization of isotopic fractionation at solid condensation. A first experiment involving very strong supersaturation evidences a strong kinetic effect on 17O-excess at solid condensation, similar to d-excess. It also shows the limits of the classical formulation of water isotopic fractionation during solid condensation estimation at very low temperature. A second experiment performed in a cloud chamber under controlled conditions uses cavity ring down spectrometers (CRDS) to determine the spatial variability of water vapour isotopic composition due to diffusion (kinetic effect) during solid condensation. The spatial variability of water vapour isotopic composition can be relatively well reproduced by the resolution of diffusion toward a cold plate. This preliminary study opens new perspectives to revisit the classical formulation of water isotopic

  9. Mass spectrometric investigation of the ionic species in a dielectric barrier discharge operating in helium-water vapour mixtures

    NASA Astrophysics Data System (ADS)

    Abd-Allah, Z.; Sawtell, D. A. G.; McKay, K.; West, G. T.; Kelly, P. J.; Bradley, J. W.

    2015-03-01

    Using advanced mass spectrometry the chemistry of ionic species present in an atmospheric-pressure parallel plate dielectric barrier discharge (DBD) with a single dielectric on the powered electrode have been identified. The discharge was driven in helium with controllable concentrations of water vapour using an excitation frequency of 10 kHz and an applied voltage of 1.2 kV. Both negative and positive ions were identified and their relative intensity determined with variation of water concentration in the discharge, inter-electrode spacing, gas residence time and nominal applied power. The most abundant negative ions were of the family \\text{O}{{\\text{H}}-}{{≤ft({{\\text{H}}2}\\text{O}\\right)}n} , while the positive ions were dominated by those of the form {{{H}}^ + }{{{(}}{{{H}}_2}{{O)}}_n} , with n up to 9 in both cases. Negative and positive ions responded in a similar way to changes in the operating parameters, with the particular response depending on the ion mass. Increasing the inter-electrode spacing and the water concentration in the discharge led to an increase in the intensity of large mass ionic water clusters. However, increasing the residence time of the species in the plasma region and increasing the applied power resulted in fragmentation of large water clusters to produce smaller ions.

  10. Validation of two independent retrievals of SCIAMACHY water vapour columns using radiosonde data

    NASA Astrophysics Data System (ADS)

    du Piesanie, A.; Piters, A. J. M.; Aben, I.; Schrijver, H.; Wang, P.; Noël, S.

    2013-01-01

    Two independently derived SCIAMACHY total water vapour column (WVC) products are compared with integrated water vapour data calculated from radiosonde measurements, and with each other. The two SCIAMACHY WVC products are retrieved with two different retrieval algorithms applied in the visible and short wave infrared wavelength regions respectively. The first SCIAMACHY WVC product used in the comparison is ESA's level 2 version 5.01 WVC product derived with the Air Mass Corrected Differential Absorption Spectroscopy (AMC-DOAS) retrieval algorithm (SCIAMACHY-ESA). The second SCIAMACHY WVC product is derived using the Iterative Maximum Likelihood Method (IMLM) developed by Netherlands Institute for Space Research (SCIAMACHY-IMLM). Both SCIAMACHY WVC products are compared with collocated water vapour amounts determined from daily relative humidity radiosonde measurements obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) radiosonde network, over an 18 month and 2 yr period respectively. Results indicate a good agreement between the WVC amounts of SCIAMACHY-ESA and the radiosonde, and a mean difference of 0.03 g cm-2 is found for cloud free conditions. Overall the SCIAMACHY-ESA WVC amounts are smaller than the radiosonde WVC amounts, especially over oceans. For cloudy conditions the WVC bias has a clear dependence on the cloud top height and increases with increasing cloud top heights larger than approximately 2 km. A likely cause for this could be the different vertical profile shapes of water vapour and O2 leading to different relative changes in their optical thickness, which makes the AMF correction method used in the algorithm less suitable for high clouds. The SCIAMACHY-IMLM WVC amounts compare well to the radiosonde WVC amounts during cloud free conditions over land. A mean difference of 0.08 g cm-2 is found which is consistent with previous results when comparing daily averaged SCIAMACHY-IMLM WVC amounts with ECMWF model data globally

  11. Water vapour isotopic exchange by epiphytic bromeliads in tropical dry forests reflects niche differentiation and climatic signals.

    PubMed

    Reyes-García, Casandra; Mejia-Chang, Monica; Jones, Glyn D; Griffiths, Howard

    2008-06-01

    The 18O signals in leaf water (delta18O(lw)) and organic material were dominated by atmospheric water vapour 18O signals (delta18O(vap)) in tank and atmospheric life forms of epiphytic bromeliads with crassulacean acid metabolism (CAM), from a seasonally dry forest in Mexico. Under field conditions, the mean delta18O(lw) for all species was constant during the course of the day and systematically increased from wet to dry seasons (from 0 to +6 per thousand), when relative water content (RWC) diminished from 70 to 30%. In the greenhouse, progressive enrichment from base to leaf tip was observed at low night-time humidity; under high humidity, the leaf tip equilibrated faster with delta18O(vap) than the other leaf sections. Laboratory manipulations using an isotopically depleted water source showed that delta18O(vap) was more rapidly incorporated than liquid water. Our data were consistent with a Craig-Gordon (C-G) model as modified by Helliker and Griffiths predicting that the influx and exchange of delta18O(vap) control delta18O(lw) in certain epiphytic life forms, despite progressive tissue water loss. We use delta18O(lw) signals to define water-use strategies for the coexisting species which are consistent with habitat preference under natural conditions and life form. Bulk organic matter (delta18O(org)) is used to predict the deltaO18(vap) signal at the time of leaf expansion. PMID:18266906

  12. Water vapour permeability of poly(lactic acid): Crystallinity and the tortuous path model

    NASA Astrophysics Data System (ADS)

    Duan, Z.; Thomas, N. L.

    2014-02-01

    The water vapour transmission rates (WVTR) through samples of polylactic acid of different crystallinities have been measured. Three different grades of commercial poly(lactic acid) (PLA) were used with different ratios of L-lactide and D-lactide to give a range of crystallinities from 0% to 50%. Sheets of PLA were prepared by melt compounding followed by compression moulding and annealing at different temperatures and for different times to give the range of crystallinities required. Crystallinity was measured by differential scanning calorimetry and the morphology of the samples was observed under crossed polars in a transmitted light microscope. Water vapour transmission rates through the films were measured at 38 °C and at a relative humidity of 90%. It was found that the measured values of WVTR decreased linearly with increasing crystallinity of the PLA from 0% to 50%. The results are discussed in terms of the effect of crystallinity on solubility and shown to fit the "Tortuous Path Model." The model was also successfully used to explain published data on water permeability of polyethylene terephthalate.

  13. Carbon dioxide and water vapour fluxes for one year above a temperate grazed grassland

    NASA Astrophysics Data System (ADS)

    Jaksic, V.; Kiely, G.; Albertson, J.; Scanlon, T.

    2003-04-01

    The Dripsey flux site in Cork, Ireland is a perennial ryegrass (C3 category) pasture and is grazed for approximately 8 to 10 months of the year. The lands are fertilised with approximately 200kg/ha/year of nitrogen. The flux tower monitoring carbon dioxide, water vapour and energy was established in June 2001 and we have continuous data since then. The site also includes streamflow hydrology and stream water chemistry. We present the results and analysis for carbon dioxide and water vapour for the year July 1, 2001 to July 1, 2002. The accumulated evapotranspiration amounts to 522mm/annum compared to 1600mm/annum of rainfall. The one year carbon sequestration is 3.9t/ha. The estimated carbon in the grass and silage is 3.6t/ha. This suggests that the soils in these pastures are a sink for approximately 0.3t carbon per hectare. This work is part of a five year (2002-2006) research project funded by the Irish Environmental Protection Agency.

  14. Water vapour and hydrogen in the terrestrial-planet-forming region of a protoplanetary disk.

    PubMed

    Eisner, J A

    2007-05-31

    Planetary systems (ours included) formed in disks of dust and gas around young stars. Disks are an integral part of the star and planet formation process, and knowledge of the distribution and temperature of inner-disk material is crucial for understanding terrestrial planet formation, giant planet migration, and accretion onto the central star. Although the inner regions of protoplanetary disks in nearby star-forming regions subtend only a few nano-radians, near-infrared interferometry has recently enabled the spatial resolution of these terrestrial zones. Most observations have probed only dust, which typically dominates the near-infrared emission. Here I report spectrally dispersed near-infrared interferometric observations that probe the gas (which dominates the mass and dynamics of the inner disk), in addition to the dust, within one astronomical unit (1 au, the Sun-Earth distance) of the young star MWC 480. I resolve gas, including water vapour and atomic hydrogen, interior to the edge of the dust disk; this contrasts with results of previous spectrally dispersed interferometry observations. Interactions of this accreting gas with migrating planets may lead to short-period exoplanets like those detected around main-sequence stars. The observed water vapour is probably produced by the sublimation of migrating icy bodies, and provides a potential reservoir of water for terrestrial planets. PMID:17538613

  15. A comparison of standard methods for measuring water vapour permeability of fabrics

    NASA Astrophysics Data System (ADS)

    McCullough, Elizabeth A.; Kwon, Myoungsook; Shim, Huensup

    2003-08-01

    It is difficult for outdoor apparel manufacturers to interpret the technical information provided by fabric suppliers concerning fabric 'breathability' properties because different methods and test conditions are used. In addition, fabrics with hydrophilic components change their properties under different humidity conditions. The purpose of this study was to measure the water vapour permeability and evaporative resistance of 26 different waterproof, windproof and breathable shell fabrics using five standard test methods. The water vapour transmission rate (WVTR) was measured using the ASTM E 96 upright and inverted cup tests with water, the JIS L 1099 desiccant inverted cup test and the new ASTM F 2298 standard using the dynamic moisture permeation cell (DMPC). The evaporative resistance was measured using the ISO 11092 sweating hot plate test. The WVTRs were consistently highest when measured with the desiccant inverted cup, followed by the inverted cup, DMPC and upright cup. The upright cup was significantly correlated with the DMPC (0.97), and the desiccant inverted cup was correlated to the sweating hot plate (-0.91).

  16. Rain scavenging of tritiated water vapour: a numerical Eulerian stationary model.

    PubMed

    Atanassov, D; Galeriu, D

    2011-01-01

    The tradition in tritium washout modeling is to unite the washout model with a Gaussian plume model describing dispersion of tritium vapour in the atmosphere. In the present study, an alternative approach is proposed. A numerical Eulerian model that describes washout independently of dispersion is developed. The sensitivity analysis to model parameters has shown that the washout process is influenced most significantly by rainfall parameters and air temperature: different raindrop size distributions cause differences of up to about 70% in the washout outputs; a change of 15°C in the air temperature causes an effect of about 50%. Results are presented showing calculated values of washout outputs (tritium concentration in rain, tritium downward flux, washout coefficient) for different tritium vapour profiles, rainfall rates and air temperatures. The general conclusion is that the washout process is too complex to be described comprehensively by the simple washout coefficient concept. We suggest the approach proposed here for directly calculating the tritium downward flux and concentration in the rainwater is preferable. PMID:20934237

  17. Discovery of water vapour around IRC+10216 as evidence for comets orbiting another star

    NASA Astrophysics Data System (ADS)

    Melnick, Gary J.; Neufeld, David A.; Ford, K. E. Saavik; Hollenbach, David J.; Ashby, Matthew L. N.

    2001-07-01

    Since 1995, planets with masses comparable to that of Jupiter have been discovered around approximately 60 stars. These planets have not been seen directly, but their presence has been inferred from the small reflex motions that they gravitationally induce on the star they orbit; these motions result in small periodic wavelength shifts in the stellar spectrum. The presence of analogues of the smaller bodies in our Solar System cannot, however, be determined using this technique, because the induced reflex motions are too small-so an alternative approach is needed. Here we report the observation of circumstellar water vapour around the ageing carbon star IRC+10216 water is not expected in measurable quantities around such a star. The only plausible explanation for this water is that the recent evolution of IRC+10216, which has been accompanied by a prodigious increase in its luminosity, is causing the vaporization of a collection of orbiting icy bodies-a process considered in an earlier theoretical study.

  18. Development of a GNSS water vapour tomography system using algebraic reconstruction techniques

    NASA Astrophysics Data System (ADS)

    Bender, Michael; Dick, Galina; Ge, Maorong; Deng, Zhiguo; Wickert, Jens; Kahle, Hans-Gert; Raabe, Armin; Tetzlaff, Gerd

    2011-05-01

    A GNSS water vapour tomography system developed to reconstruct spatially resolved humidity fields in the troposphere is described. The tomography system was designed to process the slant path delays of about 270 German GNSS stations in near real-time with a temporal resolution of 30 min, a horizontal resolution of 40 km and a vertical resolution of 500 m or better. After a short introduction to the GPS slant delay processing the framework of the GNSS tomography is described in detail. Different implementations of the iterative algebraic reconstruction techniques (ART) used to invert the linear inverse problem are discussed. It was found that the multiplicative techniques (MART) provide the best results with least processing time, i.e., a tomographic reconstruction of about 26,000 slant delays on a 8280 cell grid can be obtained in less than 10 min. Different iterative reconstruction techniques are compared with respect to their convergence behaviour and some numerical parameters. The inversion can be considerably stabilized by using additional non-GNSS observations and implementing various constraints. Different strategies for initialising the tomography and utilizing extra information are discussed. At last an example of a reconstructed field of the wet refractivity is presented and compared to the corresponding distribution of the integrated water vapour, an analysis of a numerical weather model (COSMO-DE) and some radiosonde profiles.

  19. Analysis of the sorption properties of different soils using water vapour adsorption and potentiometric titration methods

    NASA Astrophysics Data System (ADS)

    Skic, Kamil; Boguta, Patrycja; Sokołowska, Zofia

    2016-07-01

    Parameters of specific surface area as well as surface charge were used to determine and compare sorption properties of soils with different physicochemical characteristics. The gravimetric method was used to obtain water vapour isotherms and then specific surface areas, whereas surface charge was estimated from potentiometric titration curves. The specific surface area varied from 12.55 to 132.69 m2 g-1 for Haplic Cambisol and Mollic Gleysol soil, respectively, and generally decreased with pH (R=0.835; α = 0.05) and when bulk density (R=-0.736; α = 0.05) as well as ash content (R=-0.751; α = 0.05) increased. In the case of surface charge, the values ranged from 63.00 to 844.67 μmol g-1 Haplic Fluvisol and Mollic Gleysol, respecively. Organic matter gave significant contributions to the specific surface area and cation exchange capacity due to the large surface area and numerous surface functional groups, containing adsorption sites for water vapour molecules and for ions. The values of cation exchange capacity and specific surface area correlated linearly at the level of R=0.985; α = 0.05.

  20. Post-wildfire effects on carbon and water vapour dynamics in a Spanish black pine forest.

    PubMed

    Dadi, T; Rubio, E; Martínez-García, E; López-Serrano, F R; Andrés-Abellán, M; García-Morote, F A; De las Heras, J

    2015-04-01

    Two eddy covariance systems were installed in a high-severity burned zone (BZ) and an adjacent unburned (UNB) zone to monitor water vapour and carbon dioxide fluxes for 21 months (from June 2011 to February 2013) at a Spanish black pine forest affected by a stand-replacing wildfire and located in a mountainous area of central-eastern Spain. The differences between both sites were significant especially during the growing season, affecting gross primary productivity (GPP) more than ecosystem respiration (Reco). Net ecosystem exchange (NEE) for 2012 was -3.97 and 1.80 t C ha(-1) year(-1) for the unburned and burned sites, respectively, the GPP being 64% lower for the BZ than the UNB zone. Evapotranspiration (ET) at the UNB was 18% greater than at the BZ. Difference between sites was 160 mm during the whole studied period. This study reflects the effect of one of the major disturbances that can affect Mediterranean ecosystems, showing that carbon fluxes are more dramatically concerned than water vapour fluxes. PMID:25432426

  1. Evaluation of balloon and satellite water vapour measurements in the Southern tropical UTLS during the HIBISCUS campaign

    NASA Astrophysics Data System (ADS)

    Montoux, N.; Hauchecorne, A.; Pommereau, J.-P.; Durry, G.; Morel, B.; Jones, R. L.; Lefèvre, F.; Bencherif, H.

    2007-05-01

    Among the objectives of the HIBISCUS campaign was the study of water vapour in the tropical upper troposphere and lower stratosphere (UTLS) by balloon borne in situ and remote sensing, offering a unique opportunity for evaluating the performances of balloon and satellite water vapour data available at the southern tropics in February-April 2004. Instruments evaluated include balloon borne in situ tunable diode laser spectrometer (μ SDLA) and surface acoustic wave hygrometer (SAW), and remote sensing with a near IR spectrometer (SAOZ) flown on a circumnavigating long duration balloon. The satellite systems available are those of AIRS/AMSU (v4), SAGE-II (v6.2), HALOE (v19), MIPAS (v4.62) and GOMOS (v6.0). In the stratosphere between 20-25 km, three satellite instruments, HALOE, SAGE-II and MIPAS, are showing very consistent results (nearly constant mixing ratios), while AIRS, GOMOS and the SAOZ balloon are displaying a slight increase with altitude. Considering the previous studies, the first three appear the most precise at this level, HALOE being the less variable (5%), close to the atmospheric variability shown by the REPROBUS/ECMWF Chemistry-Transport model. The three others are showing significantly larger variability, AIRS being the most variable (35%), followed by GOMOS (25%) and SAOZ (20%). Lower down in the Tropical Tropopause Layer between 14-20 km, HALOE and SAGE-II are showing marked minimum mixing ratios around 17-19 km, not seen by all others. For HALOE, this might be related to an altitude registration error already identified on ozone, while for SAGE-II, a possible explanation could be the persistence of the dry bias displayed by previous retrieval versions, not completely removed in version 6.2. On average, MIPAS is consistent with AIRS, GOMOS and SAOZ, not displaying the dry bias observed in past versions, but a fast degradation of precision below 20 km. Compared to satellites, the μ SDLA measurements shows systematically larger humidity although

  2. Experimental determination and theoretical framework of kinetic fractionation at the water vapour - ice interface at low temperature.

    NASA Astrophysics Data System (ADS)

    Casado, M.; Prie, F.

    2015-12-01

    Isotopic fraction of water enables climate reconstruction from ice cores. The use of different heavy isotopes of water such as H218O, H217O or HDO gives information about local temperature but also temperature and humidity of water vapour sources. Quantification of these parameters relies on the good knowledge of equilibrium and kinetic isotopic fractionation at each step of the water cycle. The strongest limitation when interpreting water isotopes in remote Antarctic ice cores is the formulation of the isotopic fractionation at solid condensation (vapour to ice). This classical formulation also implies a good knowledge of coefficients for equilibrium fractionation and water vapour diffusion in air as well as supersaturation in clouds. The uncertainties lying on these different parameters make the formulation of isotopic fractionation at solid condensation only empirical. Here, we make use (1) of recent development in the measurements of water isotopes in the water vapour through infra-red spectroscopy and (2) of the possibility to measure accurately 17O-excess of water to test the classical formulation and parameterization of isotopic fractionation at solid condensation. A first experiment involving very strong supersaturation evidences a strong kinetic effect on 17O-excess on solid condensation, similar to d-excess. It also shows the limits of the classical formulation of water isotopic fractionation during solid condensation estimation at very low temperature. A second experiment performed in a cloud chamber in controlled conditions uses CRDS instruments to depict the spatial variability of water vapour isotopic composition due to diffusion (kinetic effect) during solid condensation. These experiments are in agreement with a new theoretical model that we present for the competition between diffusions of different isotopes. This preliminary study opens new perspectives to revisit the classical formulation of water isotopic fractionation during solid condensation

  3. The impact of deep overshooting convection on the water vapour and trace gas distribution in the TTL and lower stratosphere

    NASA Astrophysics Data System (ADS)

    Frey, W.; Schofield, R.; Hoor, P. M.; Ravegnani, F.; Ulanovsky, A.; Viciani, S.; D'Amato, F.; Lane, T. P.

    2014-12-01

    Overshooting convection penetrating the tropical tropopause layer (TTL) and the lower stratosphere has a significant impact on the redistribution of water vapour and further trace gases. This is of importance for the stratospheric water vapour budget, which plays a central role in radiative and chemical processes. Modelling studies and in situ measurements show the hydration potential of convective overshooting partly by direct injection of ice particles into the stratosphere and subsequent sublimation. However, processes leading to dehydration of the TTL may also impact the stratospheric humidity by limiting the amount of water vapour carried aloft. While the large scale drives some of the dehydrating processes, others are of convective origin, for example gravity waves and cooling associated with overshooting turrets. Furthermore, downdrafts may transport dry and ozone rich air masses from the stratosphere into the TTL. Improving our understanding of overshooting convection and its influence on TTL water vapour will ultimately place better constraints on the budget of water vapour in the stratosphere.In this study we use three-dimensional cloud resolving (WRF-ARW) simulations of a deep convective thunderstorm (Hector) to study the redistribution of water vapour and trace gases in the upper TTL/lower stratosphere. Passive tracers are initialised to investigate the transport of air masses. The simulations focus on an Hector event that has been probed by aircraft during the SCOUT-O3 field campaign. Observations were performed in and around overshoots that even penetrated the stratosphere. These observations as well as the model simulations show downward transport and mixing of air masses from the stratosphere, though less strong and more localised in the simulation. Furthermore, the simulations shows a layering of hydrated and dehydrated air masses post-convection in the upper TTL and lower stratosphere. Here we use the model to explain the processes causing the

  4. Stratospheric temperatures in Antarctic winter: Does the 40-year record confirm midlatitude trends in stratospheric water vapour?

    NASA Astrophysics Data System (ADS)

    Roscoe, H. K.; Colwell, S. R.; Shanklin, J. D.

    2003-04-01

    Water vapour is a potent greenhouse gas, and the observed increases in water vapour in the stratosphere act to cool it. Possible changes in stratospheric temperatures are important for future ozone loss because colder temperatures in the edge region of the Antarctic ozone hole act to increase polar stratospheric clouds there, and so delay recovery of the ozone hole. Trends in lower-stratospheric temperature within the core of the Antarctic vortex in winter should be a unique indicator of trends in stratospheric water vapour, because neither changes in CO2 nor in ozone have a large effect on temperature in the lower stratosphere in the dark. Here, measured stratospheric temperatures southward of 70°S in winter are presented and their quality and corrections discussed. The character and magnitude of the long-term changes at Halley (76°S) are similar from 100 to 70 hPa and at 50 hPa, whether corrected for sonde changes or not, and are also similar to those at other Antarctic sites. We found no significant trend in temperatures at Halley between 1960 and 2000, which is inconsistent with the change calculated from the trend in lower-stratospheric water vapour in northern hemisphere midlatitudes between 1960 and 2000. Over the shorter interval between 1980 and 2000 at Halley, the change in temperature was-1.8 ± 0.6 K, in agreement with the change calculated from the trend in stratospheric water vapour in northern hemisphere midlatitudes between 1980 and 2000. The differences between these periods are discussed in terms of: possible fortuitous agreement between 1980 and 2000; the poorer representation and quality of the measurements of stratospheric water vapour between 1960 and 1980; and a possible large variation in the rate of oxidation of CH4 to H2O in the upper stratosphere between 1960 and 1980. Such a variation in oxidation rate was observed by satellite between 1992 and 1999.

  5. How do leaf hydraulics limit stomatal conductance at high water vapour pressure deficits?

    PubMed

    Bunce, James A

    2006-08-01

    A reduction in leaf stomatal conductance (g) with increasing leaf-to-air difference in water vapour pressure (D) is nearly ubiquitous. Ecological comparisons of sensitivity have led to the hypothesis that the reduction in g with increasing D serves to maintain leaf water potentials above those that would cause loss of hydraulic conductance. A reduction in leaf water potential is commonly hypothesized to cause stomatal closure at high D. The importance of these particular hydraulic factors was tested by exposing Abutilon theophrasti, Glycine max, Gossypium hirsutum and Xanthium strumarium to D high enough to reduce g and then decreasing ambient carbon dioxide concentration ([CO2]), and observing the resulting changes in g, transpiration rate and leaf water potential, and their reversibility. Reducing the [CO2] at high D increased g and transpiration rate and lowered leaf water potential. The abnormally high transpiration rates did not result in reductions in hydraulic conductance. Results indicate that low water potential effects on g at high D could be overcome by low [CO2], and that even lower leaf water potentials did not cause a reduction in hydraulic conductance in these well-watered plants. Reduced g at high D in these species resulted primarily from increased stomatal sensitivity to [CO2] at high D, and this increased sensitivity may mediate stomatal responses to leaf hydraulics at high D. PMID:16898024

  6. Simulation of the isotopic composition of stratospheric water vapour - Part 1: Description and evaluation of the EMAC model

    NASA Astrophysics Data System (ADS)

    Eichinger, R.; Jockel, P.; Brinkop, S.; Werner, M.; Lossow, S.

    2015-05-01

    This modelling study aims at an improved understanding of the processes that determine the water vapour budget in the stratosphere by means of the investigation of water isotope ratios. An additional (and separate from the actual) hydrological cycle has been introduced into the chemistry-climate model EMAC, including the water isotopologues HDO and H218O and their physical fractionation processes. Additionally an explicit computation of the contribution of methane oxidation to H2O and HDO has been incorporated. The model expansions allow detailed analyses of water vapour and its isotope ratio with respect to deuterium throughout the stratosphere and in the transition region to the troposphere. In order to assure the correct representation of the water isotopologues in the model's hydrological cycle, the expanded system has been evaluated in several steps. The physical fractionation effects have been evaluated by comparison of the simulated isotopic composition of precipitation with measurements from a ground-based network (GNIP) and with the results from the isotopologue-enabled general circulation model ECHAM5-wiso. The model's representation of the chemical HDO precursor CH3D in the stratosphere has been confirmed by a comparison with chemical transport models (1-D, CHEM2D) and measurements from radiosonde flights. Finally, the simulated stratospheric HDO and the isotopic composition of water vapour have been evaluated, with respect to retrievals from three different satellite instruments (MIPAS, ACE-FTS, SMR). Discrepancies in stratospheric water vapour isotope ratios between two of the three satellite retrievals can now partly be explained.

  7. Simulation of the isotopic composition of stratospheric water vapour - Part 1: Description and evaluation of the EMAC model

    NASA Astrophysics Data System (ADS)

    Eichinger, R.; Jöckel, P.; Brinkop, S.; Werner, M.; Lossow, S.

    2014-09-01

    This modelling study aims on an improved understanding of the processes, that determine the water vapour budget in the stratosphere by means of the investigation of water isotope ratios. At first, a separate hydrological cycle has been introduced into the chemistry-climate model EMAC, including the water isotopologues HDO and H218O and their physical fractionation processes. Additionally an explicit computation of the contribution of methane oxidation to HDO has been incorporated. The model expansions allow detailed analyses of water vapour and its isotope ratio with respect to deuterium throughout the stratosphere and in the transition region to the troposphere. In order to assure the correct representation of the water isotopologues in the model's hydrological cycle, the expanded system has been evaluated in several steps. The physical fractionation effects have been evaluated by comparison of the simulated isotopic composition of precipitation with measurements from a ground-based network (GNIP) and with the results from the isotopologue-enabled general circulation model ECHAM5-wiso. The model's representation of the chemical HDO precursor CH3D in the stratosphere has been confirmed by a comparison with chemical transport models (CHEM1D, CHEM2D) and measurements from radiosonde flights. Finally, the simulated stratospheric HDO and the isotopic composition of water vapour have been evaluated, with respect to retrievals from three different satellite instruments (MIPAS, ACE-FTS, SMR). Discrepancies in stratospheric water vapour isotope ratios between two of the three satellite retrievals can now partly be explained.

  8. Effect of resin hydrophilicity on water-vapour permeability of dental adhesive films.

    PubMed

    King, Nigel M; Hiraishi, Noriko; Yiu, Cynthia K Y; Pashley, Edna L; Loushine, Robert J; Rueggeberg, Fred A; Pashley, David H; Tay, Franklin R

    2005-10-01

    This study examined the water-vapour permeability of thin polymerized resin films fabricated from five co-monomer blends of increasing degrees of hydrophilicity, as measured by their Hoy's solubility parameters. Neat resin films were prepared from five experimental light-curable resins (n = 10). Each film was mounted in a Fisher permeability cup with 8 g of water placed inside the cup. The experiments were conducted in a modified twin-outlet desiccator connected to a vacuum pump in one outlet to permit a continuous airflow to encourage water evaporation. Weight losses by water evaporation were measured at 3, 6, 9, 24, 30, and 48 h by using an analytical balance. Additional resin films were examined by using transmission electron microscopy (TEM) after immersion in ammoniacal silver nitrate. A significant correlation was observed between the cumulative water loss at 48 h and the Hoy's total cohesive energy density (delta(t)). Transmission electron microscopy revealed silver-filled channels along film peripheries and silver grains of decreasing dimensions toward the film centres in co-monomer blends 3, 4, and 5 of increasing hydrophilicity. Hydrophilic dentin adhesives polymerized in thin films are prone to water loss by evaporation. This probably accounts for the water droplets seen on the surface of vital-bonded dentin after the application of simplified dentin adhesives. PMID:16202033

  9. The Earth as an extrasolar transiting planet. II. HARPS and UVES detection of water vapour, biogenic O2, and O3

    NASA Astrophysics Data System (ADS)

    Arnold, L.; Ehrenreich, D.; Vidal-Madjar, A.; Dumusque, X.; Nitschelm, C.; Querel, R. R.; Hedelt, P.; Berthier, J.; Lovis, C.; Moutou, C.; Ferlet, R.; Crooker, D.

    2014-04-01

    Context. The atmospheric composition of transiting exoplanets can be characterized during transit by spectroscopy. Detections of several chemical species have previously been reported in the atmosphere of gaseous giant exoplanets. For the transit of an Earth twin, models predict that biogenic oxygen (O2) and ozone (O3) atmospheric gases should be detectable, as well as water vapour (H2O), a molecule linked to habitability as we know it on Earth. Aims: The aim is to measure the Earth radius versus wavelength λ - or the atmosphere thickness h(λ) - at the highest spectral resolution available to fully characterize the signature of Earth seen as a transiting exoplanet. Methods: We present observations of the Moon eclipse of December 21, 2010. Seen from the Moon, the Earth eclipses the Sun and opens access to the Earth atmosphere transmission spectrum. We used two different ESO spectrographs (HARPS and UVES) to take penumbra and umbra high-resolution spectra from ≈3100 to 10 400 Å. A change of the quantity of water vapour above the telescope compromised the quality of the UVES data. We corrected for this effect in the data processing. We analyzed the data by three different methods. The first method is based on the analysis of pairs of penumbra spectra. The second makes use of a single penumbra spectrum, and the third of all penumbra and umbra spectra. Results: Profiles h(λ) are obtained with the three methods for both instruments. The first method gives the best result, in agreement with a model. The second method seems to be more sensitive to the Doppler shift of solar spectral lines with respect to the telluric lines. The third method makes use of umbra spectra, which bias the result by increasing the overall negative slope of h(λ). It can be corrected for this a posteriori from results with the first method. The three methods clearly show the spectral signature of the Rayleigh scattering in the Earth atmosphere and the bands of H2O, O2, and O3. Sodium is

  10. Chemical vapour deposition enhanced by atmospheric microwave plasmas: a large-scale industrial process or the next nanomanufacturing tool?

    NASA Astrophysics Data System (ADS)

    Belmonte, T.; Gries, T.; Cardoso, R. P.; Arnoult, G.; Kosior, F.; Henrion, G.

    2011-04-01

    This paper describes several specific aspects of atmospheric plasma deposition carried out with a microwave resonant cavity. Deposition over a wide substrate is first studied. We show that high deposition rates (several hundreds of μm h-1) are due to localization of fluxes on the substrate by convection when slightly turbulent flows are used. Next, we describe possible routes to localize deposition over a nanometre-sized area. Scaling down atmospheric plasma deposition is possible and two strategies to reach nanometre scales are described. Finally, we study self-organization of SiO2 nanodots deposited by chemical vapour deposition at atmospheric pressure enhanced by an Ar-O2 micro-afterglow operating at high temperature (>1200 K). When the film being deposited is thin enough (~500 nm) nanodots are obtained and they can be assembled into threads to create patterned surfaces. When the coating becomes thicker (~1 µm), and for relatively high content in HMDSO, SiO2 walls forming hexagonal cells are obtained.

  11. OT1_dneufeld_2: The puzzle of water vapour in carbon-rich stars

    NASA Astrophysics Data System (ADS)

    Neufeld, D.

    2010-07-01

    Using the HIFI instrument, we will address the puzzling - but widespread - appearance of water vapour in carbon-rich stars. Following up on detections of water in ALL SIX carbon-rich AGB stars observed to date in a pilot study performed in the HIFISTARS Key Program, we will target additional water transitions in four stars already observed or expected to show the most luminous water emissions. The target stars are CIT6, IRAC 15194-5155, V Cygni, and S Cep, and the additional transitions are the 4(22)-3(31) and 3(12) - 2(21) transitions at 916 GHz and 1153 GHz. Combined with spectra already obtained for the low-lying water transitions, and interpreted in the context of water excitation models, the proposed observations will place strong constraints upon the location of the emitting water. We will therefore be able to distinguish between various hypotheses that have been proposed for the origin of the observed water: the vaporization of orbiting comets or dwarf planets; catalytic formation on dust grains; or chemical processes initiated by the photodissociation of CO. In addition, we will carry out deep integrations to observe the lowest 1(11) - 0(00) transition of para-water at 1113 GHz in two carbon-rich AGB stars: IRAS+40540 and V Hya; here, ortho-water has been securely detected but existing observations of the 1113 GHz para-water line yield weak detections that lack the signal-to-noise ratio needed to constrain the ortho-to-para ratio.

  12. Representativeness of total column water vapour retrievals from instruments on polar orbiting satellites

    NASA Astrophysics Data System (ADS)

    Diedrich, Hannes; Wittchen, Falco; Preusker, René; Fischer, Jürgen

    2016-07-01

    The remote sensing of total column water vapour (TCWV) from polar orbiting, sun-synchronous satellite spectrometers such as the Medium Resolution Imaging Spectrometer (MERIS) on board of ENVISAT and the Moderate Imaging Spectroradiometer (MODIS) on board of Aqua and Terra enables observations on a high spatial resolution and a high accuracy over land surfaces. The observations serve studies about small-scale variations of water vapour as well as the detection of local and global trends. However, depending on the swath width of the sensor, the temporal sampling is low and the observations of TCWV are limited to cloud-free land scenes. This study quantifies the representativeness of a single TCWV observation at the time of the satellite overpass under cloud-free conditions by investigating the diurnal cycle of TCWV using 9 years of a 2-hourly TCWV data set from global GNSS (Global Navigation Satellite Systems) stations. It turns out that the TCWV observed at 10:30 local time (LT) is generally lower than the daily mean TCWV by 0.65 mm (4 %) on average for cloud-free cases. Averaging over all GNSS stations, the monthly mean TCWV at 10:30 LT, constrained to cases that are cloud-free, is 5 mm (25 %) lower than the monthly mean TCWV at 10:30 LT of all cases. Additionally, the diurnal variability of TCWV is assessed. For the majority of GNSS stations, the amplitude of the averaged diurnal cycle ranges between 1 and 5 % of the daily mean with a minimum between 06:00 and 10:00 LT and maximum between 16:00 and 20:00 LT. However, a high variability of TCWV on an individual day is detected. On average, the TCWV standard deviation is about 15 % regarding the daily mean.

  13. Usefulness of satellite water vapour imagery in forecasting strong convection: A flash-flood case study

    NASA Astrophysics Data System (ADS)

    Georgiev, Christo G.; Kozinarova, Gergana

    Using a case study of a severe convective event as an example, a framework for interpreting 6.2 µm channel satellite imagery that enables to indicate upper-level conditioning of the convective environment is presented and discussed. In order to illustrate the approach, all convective cells during the summer of 2007 that produced precipitations over Bulgaria are considered. They are classified regarding the observed moisture pattern in mid-upper levels as well as the low-level conditions of air humidity and convergence of the flow. Water vapour (WV) images are used to study the evolution of the upper-level moist and dry structures. The proposed interpretation is that the role of the upper-level dry boundaries identified in the WV imagery as favoured areas for the initiation of deep moist convection cannot be understood (and hence cannot be forecasted accurately) by considering them in isolation from the dynamic rate at which they are maintained. The paper examines the 23 June 2006 flash flood in Sofia city as a case, in which the operational forecast of the National Institute of Meteorology and Hydrology of Bulgaria based on the mesoscale NWP model ALADIN underestimated the severity of the convective process. A comparison between the satellite water vapour imagery and the corresponding geopotential field of the dynamical tropopause, expressed in terms of potential vorticity (PV), shows an error in the performance of the ARPEGE operational numerical model. There is an obvious mismatch between the PV anomaly structure and the dry zone of the imagery. The forecast field shows underestimation of the tropopause height gradient and displacement of the PV anomaly to the southwest of the real position seen in the satellite image. It is concluded that the observed poor forecast is a result of the ARPEGE failure to treat correctly the interaction between the PV anomaly and the low-level warm anomaly.

  14. Water vapour intercomparison effort in the frame of HyMeX-SOP1

    NASA Astrophysics Data System (ADS)

    Summa, Donato; Di Girolamo, Paolo; Stelitano, Dario; Cacciani, Marco; Flamant, Cyrille; Chazette, Patrick; Ducrocq, Véronique; Nuret, Mathieu; Fourié, Nadia; Richard, Evelyne

    2014-05-01

    A water vapour intercomparison effort, involving airborne and ground-based water vapour lidar systems and mesoscale models, was carried out in the framework of the international HyMeX (Hydrological cycle in the Mediterranean Experiment) dedicated to the hydrological cycle and related high-impact events. Within HyMeX, a major field campaign was dedicated to heavy precipitation and flash flood events from 5 September to 6 November 2012. The 2 month field campaign took place over the Northwestern Mediterranean Sea and its surrounding coastal regions in France, Italy, and Spain. The main objective of this work is to provide accurate error estimates for the lidar systems i.e. the ground-based Raman lidar BASIL and the CNRS DIAL Leandre 2 on board the ATR42, as well as use BASIL data to validate mesoscale model results from the MESO NH and Arome WMED. The effort will benefit from the few dedicated ATR42 flights in the frame of the EUFAR Project "WaLiTemp". In the present work our attention was focused on two specific case studies: 13 September and 2 October in the altitude region 0.5 - 5.5 km. Comparisons between the ground-based Raman lidar BASIL and the airborne CNRS DIAL indicate a mean relative bias between the two sensors of 6.5%, while comparisons between BASIL and CNRS DIAL vs. the radiosondes indicate a bias of 2.6 and -3.5 %, respectively. The bias of BASIL vs. the ATR insitu sensor indicate a bias of -20.4 %. Specific attention will also be dedicated to the WALI/BASIL intercomparison effort which took place in Candillargues on 30 October 2012. Specific results from this intercomparison effort and from the intercomparison between BASIL and Meso-NH/AROME-WMed will be illustrated and discussed at the Conference.

  15. Leaf expansion of soybean subjected to high and low atmospheric vapour pressure deficits.

    PubMed

    Devi, M Jyostna; Taliercio, Earl W; Sinclair, Thomas R

    2015-04-01

    Vapour pressure deficit (VPD) is considered an important environmental factor that might affect leaf expansion and transpiration rate (TR) in plants. Two slow-wilting soybean (Glycine max (L.) Merr.) genotypes PI 416937 and PI 471938 along with commercial cultivar Hutcheson were subjected to low (1.2-1.6 kPa) and high VPD (2.8-3 kPa) environments to study their leaf expansion and TR over five days. Among the three genotypes, PI 416937 had the lowest increase in its TR (34%) at high VPD compared with low VPD and the greatest decrease in leaf area (31%). In contrast, Hutcheson had the highest increase in TR (87%) under high VPD and the lowest decrease in leaf expansion rate (18%). Expansin and extensin genes were isolated in PI 416937 to determine if changes in leaf expansion were associated with changes at the molecular level. The four studied genes were all suppressed after five days in the high VPD environment. PMID:25618144

  16. Leaf expansion of soybean subjected to high and low atmospheric vapour pressure deficits

    PubMed Central

    Devi, M. Jyostna; Taliercio, Earl W.; Sinclair, Thomas R.

    2015-01-01

    Vapour pressure deficit (VPD) is considered an important environmental factor that might affect leaf expansion and transpiration rate (TR) in plants. Two slow-wilting soybean (Glycine max (L.) Merr.) genotypes PI 416937 and PI 471938 along with commercial cultivar Hutcheson were subjected to low (1.2–1.6 kPa) and high VPD (2.8–3 kPa) environments to study their leaf expansion and TR over five days. Among the three genotypes, PI 416937 had the lowest increase in its TR (34%) at high VPD compared with low VPD and the greatest decrease in leaf area (31%). In contrast, Hutcheson had the highest increase in TR (87%) under high VPD and the lowest decrease in leaf expansion rate (18%). Expansin and extensin genes were isolated in PI 416937 to determine if changes in leaf expansion were associated with changes at the molecular level. The four studied genes were all suppressed after five days in the high VPD environment. PMID:25618144

  17. The kinetics and mechanism of the uranium-water vapour reaction — an evaluation of some published work

    NASA Astrophysics Data System (ADS)

    Ritchie, A. G.

    1984-04-01

    The published results of Grimes and Morris on the rate of the uranium-water vapour reaction which were obtained using interferometry have been recalculated using the best values derived from the literature for the complex refractive indices of uranium and uranium dioxide (3.1-3.91 for uranium and 2.2-0.51 for uranium dioxide). The kinetics have been described by Haycock's model and the linear rate constant is given by K 1 = 1.3 × 10 4P {1}/{2}H 2O exp( - 9.0 kcal/RT )mg U/cm 2 h, where PH 2O is the water vapour pressure in torr or K 1 = 3.48 × 10 8r {1}/{2} exp( -14.1 kcal/RT)mg U/cm 2 h, where r is the fractional relative humidity, R is the gas constant and T is the absolute temperature. A mechanism is described which accounts for the observed dependence of the rate of uranium-water vapour reaction on the square root of the water vapour pressure.

  18. CFD simulation of water vapour condensation in the presence of non-condensable gas in vertical cylindrical condensers.

    PubMed

    Li, Jun-De

    2013-02-01

    This paper presents the simulation of the condensation of water vapour in the presence of non-condensable gas using computational fluid dynamics (CFD) for turbulent flows in a vertical cylindrical condenser tube. The simulation accounts for the turbulent flow of the gas mixture, the condenser wall and the turbulent flow of the coolant in the annular channel with no assumptions of constant wall temperature or heat flux. The condensate film is assumed to occupy a negligible volume and its effect on the condensation of the water vapour has been taken into account by imposing a set of boundary conditions. A new strategy is used to overcome the limitation of the currently available commercial CFD package to solve the simultaneous simulation of flows involving multispecies and fluids of gas and liquid in separate channels. The results from the CFD simulations are compared with the experimental results from the literature for the condensation of water vapour with air as the non-condensable gas and for inlet mass fraction of the water vapour from 0.66 to 0.98. The CFD simulation results in general agree well with the directly measured quantities and it is found that the variation of heat flux in the condenser tube is more complex than a simple polynomial curve fit. The CFD results also show that, at least for flows involving high water vapour content, the axial velocity of the gas mixture at the interface between the gas mixture and the condensate film is in general not small and cannot be neglected. PMID:24850953

  19. CFD simulation of water vapour condensation in the presence of non-condensable gas in vertical cylindrical condensers

    PubMed Central

    Li, Jun-De

    2013-01-01

    This paper presents the simulation of the condensation of water vapour in the presence of non-condensable gas using computational fluid dynamics (CFD) for turbulent flows in a vertical cylindrical condenser tube. The simulation accounts for the turbulent flow of the gas mixture, the condenser wall and the turbulent flow of the coolant in the annular channel with no assumptions of constant wall temperature or heat flux. The condensate film is assumed to occupy a negligible volume and its effect on the condensation of the water vapour has been taken into account by imposing a set of boundary conditions. A new strategy is used to overcome the limitation of the currently available commercial CFD package to solve the simultaneous simulation of flows involving multispecies and fluids of gas and liquid in separate channels. The results from the CFD simulations are compared with the experimental results from the literature for the condensation of water vapour with air as the non-condensable gas and for inlet mass fraction of the water vapour from 0.66 to 0.98. The CFD simulation results in general agree well with the directly measured quantities and it is found that the variation of heat flux in the condenser tube is more complex than a simple polynomial curve fit. The CFD results also show that, at least for flows involving high water vapour content, the axial velocity of the gas mixture at the interface between the gas mixture and the condensate film is in general not small and cannot be neglected. PMID:24850953

  20. Seasonal snow cover in the Qilian Mountains of Northwest China: Its dependence on oasis seasonal evolution and lowland production of water vapour

    NASA Astrophysics Data System (ADS)

    Bourque, Charles P.-A.; Mir, Matin A.

    2012-08-01

    SummaryBack and forth exchange of water vapour and liquid water from oases at the base of the Qilian Mountains (NW China) and from the Qilian Mountains to oases as surface and shallow subsurface flow has been previously shown by model simulation to be a potentially important mechanism in the long-term stabilisation of oases in westcentral Gansu (Bourque and Hassan, 2009). In a subsequent re-examination of oasis self-support, we use monthly snow-cover patterns in the Qilian Mountains to determine the extent oasis vegetation and evapotranspiration in the low-lying portions of the upper and middle Shiyang and Hei River watersheds control snowfall dynamics in the Qilian Mountains. Monthly snow-cover area (SCA) in the watersheds is simulated with a spatially-distributed model designed to address differences in (i) topography along the prevailing wind direction, (ii) water-vapour production and transport, (iii) in-mountain production of precipitation, and (iv) precipitation phase changes. Seasonal variations in oasis vegetation, surface temperature (for model input), and SCA (for model validation) are described as separate timeseries of monthly composites of enhanced vegetation index, land surface temperature, and normalised difference snow index generated from MODIS optical reflectance and thermal emission data. Comparisons of modelled and snow-index-based estimates of SCA in the Shiyang and Hei River watersheds for the hydrological year, from August 2004 to July 2005, provide nearly similar spatiotemporal patterns; overlap between SCA's exceeds 60% for most months. An exception to this is in mid-summer of 2004, where overlap between SCA's is <30%. Agreement between monthly SCA's reinforces the importance of oasis-vegetation dynamics and mass transfer of water vapour to the atmosphere in guiding seasonal formation of precipitation and snow-cover dynamics in the Qilian Mountains.

  1. Influence of atmospheric vapour pressure deficit on ozone responses of snap bean (Phaseolus vulgaris L.) genotypes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two genotypes of snapbean (Phaseolus vulgaris L.), one known to be sensitive to ozone and the other resistant, were examined to determine their response to atmospheric vapor pressure deficit (VPD) in the presence and absence of ozone. Plants were grown in Outdoor Plant Environment Chambers in combin...

  2. An evaluation of materials and methods for vapour measurement of the isotopic composition of pore water in deep, unsaturated zones.

    PubMed

    Pratt, Dyan L; Lu, Mengna; Lee Barbour, S; Jim Hendry, M

    2016-01-01

    The development of in situ vapour sampling methods to measure δ(2)H and δ(18)O in pore water of deep, unsaturated soil profiles, including mine tailings and waste rock, is required to improve our ability to track water migration through these deposits. To develop appropriate field sampling methods, a laboratory study was first undertaken to evaluate potential materials and sampling methods to collect and analyse vapour samples from unsaturated mine waste. Field methods were developed based on these findings and tested at two mine sites using either on-site analyses with a portable isotope laser spectrometer or sample collection and storage prior to laboratory analyses. The field sites included a series of deep (>50 m) multiport profiles within a coal waste rock dump and open wells installed in a sand tailings dyke at an oil sands mine. Laboratory results show that memory effects in sample bags and tubing require 3-5 pore volumes of vapour flushing prior to sample collection and sample storage times are limited to 24 h. Field sampling highlighted a number of challenges including the need to correct for sample humidity and in situ temperature. Best results were obtained when a portable laser spectrometer was used to measure vapour samples in situ. PMID:27002493

  3. Temperature Humidity Dissimilarity and Heat-to-water-vapour Transport Efficiency Above and Within a Pine Forest Canopy: the Role of the Bowen Ratio

    NASA Astrophysics Data System (ADS)

    Lamaud, E.; Irvine, M.

    2006-07-01

    Over the past 15 years atmospheric surface-layer experiments over heterogeneous canopies have shown that the vertical transfer of sensible heat and water vapour exhibit a strong dissimilarity. In particular, the sensible-heat-to-water-vapour transport efficiencies generally exceed unity. One of the main consequences is that evaporation (latent heat flux) computed by the flux-variance method is overestimated, as persistently demonstrated by comparisons with evaporation obtained with the eddy-correlation method. Various authors proposed to take into account the temperature humidity dissimilarity to extend the applicability of the flux-variance method in order to compute evaporation from non-uniform surfaces. They attempted to connect the sensible-heat-to-water-vapour transport efficiency (λ) to the correlation coefficient between temperature and humidity turbulent fluctuations ( R Tq ). This approach was found to be successful over ‘wet’ surfaces for which λ can be approximated by R Tq and ‘dry’ surfaces for which λ can be approximated by 1/ R Tq . However, no solution has been proposed until now for intermediate hydrological conditions. We investigated this question using eddy-correlation measurements above and inside a pine forest canopy. For both levels, our data present a strong likeness with previously published results over heterogeneous surfaces. In particular, they confirm that λ is R Tq in wet conditions and 1/ R Tq in dry conditions. Moreover, we defined the range of the Bowen ratio ( Bo) values for which those two approximations are valid (below 0.1 and greater than 1, respectively) and established a relationship between λ, R Tq and Bo for the intermediate range of Bo. We are confident that this new parameterization will enlarge the applicability of the flux-variance method to all kinds of heterogeneous surfaces in various hydrological conditions

  4. Influence of Ar + ion bombardment on the initial interaction of water vapour with polycrystalline magnesium surfaces

    NASA Astrophysics Data System (ADS)

    Splinter, S. J.; McIntyre, N. S.; Palumbo, G.

    1994-01-01

    The room temperature interaction of water vapour with magnesium surfaces irradiated with Ar + ions in the dose range θ = 10 to 2000 ions/surface atom and ion energy range 1 to 5 keV has been systematically studied by Auger electron spectroscopy (AES). The character of the kinetics of water interaction with irradiated surfaces has been found to be dependent upon the total ion bombardment dose and the ion energy and to change with the level of water exposure. The effect of ion bombardment was found to be most pronounced in the oxide nucleation and growth stage of the oxidation process. The dissociative chemisorption and final bulk thickening regimes were only weakly affected by prior irradiation. The results have been interpreted based on the assumption of competition between the effects of radiation defects (vacancies, vacancy clusters, dislocation loops) and implanted argon atoms on the oxidation process. The effect of vacancy-type defects was speculated to be the provision of adsorption sites of high sticking probability and nucleation sites of reduced activation energy for place exchange and subsequent island growth. The effect of implanted argon atoms was speculated to be the blocking of adsorption and nucleation sites and interference with oxide island ordering. At relatively high water exposures (20 L) there was enhanced penetration of oxygen into the magnesium lattice postulated to occur along dislocation emergence points. No such enhanced penetration was observed for shorter water exposures (0.3 L). The limiting thickness of the oxide layer formed on magnesium at room temperature was not found to be affected by the level of prior ion bombardment.

  5. Water vapour masers in long-period variable stars. I. RX Bootis and SV Pegasi

    NASA Astrophysics Data System (ADS)

    Winnberg, A.; Engels, D.; Brand, J.; Baldacci, L.; Walmsley, C. M.

    2008-05-01

    Context: Water vapour maser emission from late-type stars characterises them as asymptotic-giant-branch stars with oxygen-rich chemistry that are losing mass at a substantial rate. Further conclusions on the properties of the stars, however, are hampered by the strong variability of the emission. Aims: We wish to understand the reasons for the strong variability of H2O masers in circumstellar shells of late-type stars. In this paper we study RX Bootis and SV Pegasi as representatives of semiregular variable stars (SRVs). Methods: We monitored RX Boo and SV Peg in the 22-GHz maser line of water vapour with single-dish telescopes. The monitoring period covered two decades for RX Boo (1987-2007) and 12 years for SV Peg (1990-1995, 2000-2007). In addition, maps were obtained of RX Boo with the Very Large Array over several years. Results: We find that most of the emission in the circumstellar shell of RX Boo is located in an incomplete ring with an inner radius of 91 mas (15 AU). A velocity gradient is found in a NW-SE direction. The maser region can be modelled as a shell with a thickness of 22 AU, which is only partially filled. The gas crossing time is 16.5 years. The ring-like structure and the velocity gradient remained stable for at least 11 years, while the maser line profiles varied strongly. This suggests that the spatial asymmetry is not accidental, so that either the mass loss process or the maser excitation conditions in RX Boo are not spherically symmetric. The strong variability of the maser spectral features is mainly due to incoherent intensity fluctuations of maser emission spots, which have lifetimes of the order of 1 year. We found no correlation between the optical and the maser variability in either star. The variability properties of the SV Peg masers do not differ substantially from those of RX Boo. There were fewer spectral features present, and the range of variations was narrower. The maser was active on the >10-Jy level only 1990-1992 and

  6. Observations of precipitable water vapour over complex topography of Ethiopia from ground-based GPS, FTIR, radiosonde and ERA-Interim reanalysis

    NASA Astrophysics Data System (ADS)

    Mengistu Tsidu, G.; Blumenstock, T.; Hase, F.

    2014-09-01

    Water vapour is one of the most important green house gases. Long-term changes in the amount of water vapour in the atmosphere need to be monitored not only for its direct role as a green house gas but also because of its role in amplifying other feedbacks in general circulation models. In recent decades, monitoring of water vapour on regular and continuous basis is becoming possible as a result of increase in the number of deployed Global Positioning Satellite (GPS) ground-based receivers at a faster pace. However, Horn of Africa region remains a data void region in this regard until recently when some GPS ground-receiver stations have been deployed to monitor tectonic movements in the Great Rift Valley. This study seizes this opportunity and the installation of Fourier Transform Infrared Spectrometer (FTIR) at Addis Ababa to assess the quality and comparability of Precipitable Water Vapour (PWV) from GPS, FTIR, radiosonde and ERA-Interim over Ethiopia. The PWVs from the three instruments and reanalysis show good correlation in the range from 0.83 to 0.92. The radiosonde PWV shows dry bias with respect to other observations and reanalysis. ERA-Interim PWV shows wet bias with respect to all while GPS PWV exhibits wet bias with respect to FTIR. The intercomparison between GPS and ERA-Interim is extended to seven other GPS stations in the country. Despite the sensitivity of GPS PWV to uncertainty in surface pressure in general, observed surface pressure is used only at four GPS stations. The gain obtained from using observed surface pressure in terms of reducing bias and strengthening correlation is significant but shows some variations among the GPS sites. In contrast to comparison at Addis Ababa, the comparison between GPS and ERA-Interim PWVs over seven other GPS stations shows difference in the magnitude and sign of bias of ERA-Interim with respect to GPS PWV from station to station. This variation is also visible across different seasons. The main cause of the

  7. Water vapour emission in vegetable fuel: absorption cell measurements and detection limits of our CO II Dial system

    NASA Astrophysics Data System (ADS)

    Bellecci, C.; De Leo, L.; Gaudio, P.; Gelfusa, M.; Lo Feudo, T.; Martellucci, S.; Richetta, M.

    2006-09-01

    Forest fires can be the cause of serious environmental and economic damages. For this reason a considerable effort has been directed toward the forest protection and fire fighting. In the early forest fire detection, Lidar technique present considerable advantages compared to the passive detection methods based on infrared cameras currently in common use, due its higher sensitivity and ability to accurately locate the fire. The combustion phase of the vegetable matter causes a great amount of water vapour emission, thus the water molecule behaviour will be studied to obtain a fire detection system ready and efficient also before the flame propagation. A first evaluation of increment of the water vapour concentration compared to standard one will be estimated by a numerical simulation. These results will be compared with the experimental measurements carried out into a cell with a CO II Dial system, burning different kinds of vegetable fuel. Our results and their comparison will be reported in this paper.

  8. Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water.

    PubMed

    Lau, Gabriel V; Ford, Ian J; Hunt, Patricia A; Müller, Erich A; Jackson, George

    2015-03-21

    The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derived for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and spherical fluid interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the spherical interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a spherical interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 Å, below which the tension is found to decrease again. In the case of spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 Å; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large

  9. Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water

    SciTech Connect

    Lau, Gabriel V.; Müller, Erich A.; Jackson, George; Ford, Ian J.; Hunt, Patricia A.

    2015-03-21

    The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derived for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and spherical fluid interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the spherical interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a spherical interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 Å, below which the tension is found to decrease again. In the case of spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 Å; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large

  10. Development of a new mini-invasive tumour hyperthermia probe using high-temperature water vapour.

    PubMed

    Yu, Tian-Hua; Zhou, Yi-Xin; Liu, Jing

    2004-01-01

    A new mini-invasive hyperthermia probe using high-temperature water vapour for deep regional tumour treatment was developed in this paper. The vacuum insulation mechanism was incorporated into the probe to avoid heating damage to the normal tissues around the edge of the insertion path. To better understand the heat transfer behaviour in living tissues due to operation of the probe, theoretical models based on the Pennes' equation were established and two closed form analytical solutions under constant flux or temperature heating at the tip of probe were obtained. Parametric studies were performed to investigate the influence of various parameters on the temperature response of tissues heated by the probe. Further, several simulating experiments on the actual heating performance of the probe fabricated in this paper were conducted on the in vitro biological materials (fresh pork) and phantom gel. It was demonstrated that the probe can cause a high enough temperature over the treatment area to thermally destroy the tumour tissue in due time, while the temperature over the surrounding healthy tissues can be kept below a safe threshold value. This mini-invasive heating probe may have significant applications in future clinical tumour hyperthermia. PMID:15371007

  11. On the inclusion of GPS precipitable water vapour in the nowcasting of rainfall

    NASA Astrophysics Data System (ADS)

    Benevides, P.; Catalao, J.; Miranda, P. M. A.

    2015-12-01

    The temporal behaviour of precipitable water vapour (PWV) retrieved from GPS delay data is analysed in a number of case studies of intense precipitation in the Lisbon area, in the period 2010-2012 and in a continuous annual cycle of 2012 observations. Such behaviour is found to correlate positively with the probability of precipitation, especially in cases of severe rainfall. The evolution of the GPS PWV in a few stations is analysed by a least-squares fitting of a broken line tendency, made by a temporal sequence of ascents and descents over the data. It is found that most severe rainfall events occur in descending trends after a long ascending period and that the most intense events occur after steep ascents in PWV. A simple algorithm, forecasting rain in the 6 h after a steep ascent of the GPS PWV in a single station, is found to produce reasonable forecasts of the occurrence of precipitation in the nearby region, without significant misses in what concerns larger rain events, but with a substantial amount of false alarms. It is suggested that this method could be improved by the analysis of 2-D or 3-D time-varying GPS PWV fields or by its joint use with other meteorological data relevant to nowcast precipitation.

  12. On the inclusion of GPS precipitable water vapour in the nowcasting of rainfall

    NASA Astrophysics Data System (ADS)

    Benevides, P.; Catalao, J.; Miranda, P. M. A.

    2015-06-01

    The temporal behaviour of Precipitable Water Vapour (PWV) retrieved from GPS delay data is analysed in a number of case studies of intense precipitation in the Lisbon area, in the period 2010-2012, and in a continuous annual cycle of 2012 observations. Such behaviour is found to correlate positively with the probability of precipitation, especially in cases of severe rainfall. The evolution of the GPS PWV in a few stations is analysed by a least-squares fitting of a broken line tendency, made by a temporal sequence of ascents and descents over the data. It is found that most severe rainfall event occurs in descending trends after a long ascending period, and that the most intense events occur after steep ascents in PWV. A simple algorithm, forecasting rain in the 6 h after a steep ascent of the GPS PWV in a single station is found to produce reasonable forecasts of the occurrence of precipitation in the nearby region, without significant misses in what concerns larger rain events, but with a substantial amount of false alarms. It is suggested that this method could be improved by the analysis of 2-D or 3-D time varying GPS PWV fields, or by its joint use with other meteorological data relevant to nowcast precipitation.

  13. Analysis of long time series of precipitable water vapour from GPS, DORIS and NWP models

    NASA Astrophysics Data System (ADS)

    Bock, Olivier; Willis, Pascal

    2013-04-01

    The analysis of GPS and DORIS measurements provides accurate estimates of zenith tropospheric delay (ZTD) and total column water vapour (TCWV). Such measurements are now available for more than 15 years from permanent ground-based stations which cover quite homogenously the globe and receive increasing interest for meteorology and climate research. This work assesses the quality of operational and reprocessed GPS and DORIS datasets. Regarding GPS, two solutions produced by JPL as contributions to IGS (repro1, covering period 1995-2007, and trop_new, covering period 2001-2010) are compared. An independent reprocessed solution produced by IGN (sgn_repro1, covering period 2004-2010) is also used in the intercomparison. Differences due to different data processing procedures and errors in metadata and discontinuities due to changes in data processing procedures are evidenced in the operational solution. A reprocessed DORIS solution (IGN solution, period 1993-2008) is also compared to GPS and to the ECMWF reanalysis (ERA-Interim). The impact of changes in GPS or DORIS equipment on the quality of the ZTD estimates is investigated. The reprocessed GPS and DORIS ZTD estimates are converted into TCWV and analysed globally and for different regions. The TCWV time series reveal significant variability at various timescales (inter-annual, seasonal, intra-seasonal and synoptic) and look very promising for validating independent observational datasets (e.g., radiosondes and satellite products) and models (reanalyses, climate models).

  14. Determination of the amount of physical adsorption of water vapour on platinum-iridium surfaces

    NASA Astrophysics Data System (ADS)

    Mizushima, S.; Ueda, K.; Ooiwa, A.; Fujii, K.

    2015-08-01

    This paper presents the measurement of the physical adsorption of water vapour on platinum-iridium surfaces using a vacuum mass comparator. This value is of importance for redefining the kilogram, which will be realized under vacuum in the near future. Mirror-polished artefacts, consisting of a reference artefact and a test artefact, were manufactured for this experiment. The surface area difference between the reference and test artefacts was 226.2 cm2. This surface area difference was approximately 3.2 times the geometric surface area of the prototype of the kilogram made of platinum-iridium (71.7 cm2). The measurement results indicate that the amount of physical adsorption at a relative humidity of 50% is 0.0129 μg cm{{-}2} , with a standard uncertainty of 0.0016 μg cm{{-}2} . This value is 0.03 to 0.16 times that observed in other studies.

  15. Study of water vapour permeability of protein and gum-based edible films by a photothermal method

    NASA Astrophysics Data System (ADS)

    Tomás, S. A.; Saavedra, R.; Cruz, A.; Pedroza-Islas, R.; San Martín, E.

    2005-06-01

    The water vapour permeability of protein and gum-based edible films was studied by means of a photothermal method. The films were prepared with two basic ingredients, whey protein concentrate and mesquite gum, according to the proportions 75:25, 50:50, 25:75, and 0:100 (weight:weight). The water vapour diffusion coefficient of the analyzed films was found within the interval 0.37 × 10-6 to 2.04 × 10-6 cm^2/s, increasing linearly by increasing the mesquite gum composition in the films. The incorporation of mesquite gum in films produces less effective moisture barriers due to its highly hydrophilic property.

  16. SIGNAL : Water vapour flux variability and local wind field investigations within five differently managed agroforestry sites across Germany

    NASA Astrophysics Data System (ADS)

    Markwitz, Christian; Siebicke, Lukas; Knohl, Alexander

    2016-04-01

    Optimising soil water uptake and ground water consumption in mono-specific agricultural systems plays an important role for sustainable land management. By including tree alleys into the agricultural landscape, called agroforestry (AF), the wind flow is modified leading to a presumably favourable microclimate behind the tree alleys. We expect that this zone is characterized by increased air temperature and atmospheric water vapour content, compared to mono-specific fields. This would extend the growing season and increase the yield production behind the tree alleys. Within the SIGNAL (Sustainable Intensification of Agriculture through Agroforestry) project the evapotranspiration (ET) variability and the local wind field of agroforestry sites compared to mono-specific agricultural systems is investigated. Our study is based on the comparison of five differently managed agroforestry sites across Germany. All site feature one agroforestry plot and one reference plot, which represents a mono-specific cropped system. Each plot is equipped with an eddy-covariance tower, including a high frequency 3D SONIC anemometer and instruments gathering standard meteorological parameter as pressure, temperature, relative humidity, precipitation, ground heat flux, net- and global radiation. The Surface Energy Budget (SEB) method will be used to calculate evapotranspiration QE as QE = ‑ QN ‑ QH ‑ QG ‑ Res by measuring the sensible heat flux, QH, with the eddy covariance method, the radiation balance, QN and the ground heat flux, QG. QH and QN will be measured continuously long-term. We will quantify site specific energy balance non-closure, Res, by temporarily measuring QE, using eddy covariance and a roving tower and then solving the SEB equation for Res. The short term Res will be used to then continuously derive QE from the SEB method. We will compare measured evapotranspiration rates from the SEB method to modelled evapotranspiration of the agroforestry systems through

  17. Atmospheric correction for inland waters

    NASA Astrophysics Data System (ADS)

    Vidot, Jerome; Santer, Richard P.

    2004-02-01

    Inland waters are an increasingly valuable natural resource with major impacts and benefits for population and environment. As the spatial resolution is improved for "ocean color" satellite sensors, such observations become relevant to monitor water quality for lakes. We first demonstrated that the required atmospheric correction cannot be conducted using the standard algorithms developed for ocean. The ocean color sensors have spectral bands that allow characterization of aerosol over dark land pixels (vegetation in the blue and in the red spectral bands). It is possible to use a representative aerosol model in the atmospheric correction over inland waters after validating the spatial homogeneity of the aerosol model in the lake vicinity. The performance of this new algorithm is illustrated on SeaWiFS scenes of the Balaton (Hungary; the Constance, Germany) lakes. We illustrated the good spatial homogeneity of the aerosols and the meaningfulness of the water leaving radiances derived over these two lakes. We also addressed the specificity of the computation of the Fresnel reflection. The direct to diffuse term of this Fresnel contribution is reduced because of the limited size of the lake. Based on the primary scattering approximation, we propose a simple formulation of this component.

  18. Preparation and characterization of CS-g-PNIPAAm microgels and application in a water vapour-permeable fabric.

    PubMed

    Wang, Weiling; Yu, Weidong

    2015-01-01

    Chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAAm) was synthesised using sonication with and without the crosslinker, N,N'-methylenebisacrylamide (MBA). FTIR, variable-temperature (1)H NMR spectroscopy, atomic force microscopy, UV-vis spectrophotometry, differential scanning calorimetry, and dynamic light scattering were used to characterize the microgels' chemical constituents, structures, morphologies, lower critical solution temperatures (LCSTs), and thermo- and pH-responsiveness. The chemical structures of the two CS-g-PNIPAAm materials were found to be similar and both exhibited dual responsiveness towards temperature and pH. The microgel containing MBA had a higher LCST, smaller diameter, and more compact structure, but exhibited opposite pH- and similar thermo-responsiveness. Although the structure of the microgel particles prepared without crosslinking was unstable, the stability of the crosslinked microgel particles enabled them to be finished onto fabric. Because the microgel prepared with MBA retains thermosensitivity, it can be used to impart controllable water vapour permeability properties. The incorporation of the MBA-crosslinked CS-g-PNIPAAm microgel particles in cotton fabric was accomplished by a simple pad-dry-cure procedure from an aqueous microparticle dispersion. The water vapour permeation of the finished fabric was measured at 25 and 40°C and 50 and 90% relative humidities. The finished fabric displayed an obviously high water vapour permeability at 40°C. PMID:25965451

  19. High resolution Raman lidar measurements for the characterization of the water vapour inflow in the frame of the Hydrological Cycle in the Mediterranean Experiment

    NASA Astrophysics Data System (ADS)

    Di Girolamo, Paolo; Cacciani, Marco; Stelitano, Dario; Summa, Donato

    2013-04-01

    The University of BASILicata Raman Lidar system (BASIL) was deployed in Candillargues (Southern France, Lat: 43°37' N, Long: 4° 4' E) in the frame of the Hydrological Cycle in the Mediterranean Experiment - HyMeX. Within this experiment a major field campaign (Special Observation Period 1-SOP1, September to November 2012) took place over the Northwestern Mediterranean Sea and its surrounding coastal regions in France, Italy and Spain, with a specific focus on the study of heavy precipitation and flash-flood events. During HyMeX-SOP1, BASIL operated between 5 September and 5 November 2012, collecting more than 600 hours of measurements, distributed over 51 measurement days and 19 intensive observation periods (IOPs). The major feature of BASIL is represented by its capability to perform 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 (Di Girolamo et al., 2004, 2006, 2009). This makes it an ideal tool for the characterization of the water vapour inflow in Southern France, which is important piece of information to improve the comprehension and forecasting capabilities of heavy precipitations in the Northwestern Mediterranean basin. Preliminary measurements from this field deployment will be illustrated and discussed at the Conference. These measurements allow to monitor and characterize the marine atmospheric flow that transport moist and conditionaly unstable air towards the coasts, which is feeding into the HPE events in Southern France. Measurements from BASIL can also be used to better characterize Planetary Boundary Layer moisture transport mechanisms from the surface to deep-convection systems. Besides temperature and water vapour, BASIL also provides measurements of the particle (aerosol/cloud) backscattering coefficient at 355, 532 and 1064 nm, of the particle extinction coefficient at 355 and 532

  20. From GNSS and meteorological data to NRT 4D water vapour distribution - GNSS meteorology activities at WUELS

    NASA Astrophysics Data System (ADS)

    Bosy, Jaroslaw; Kaplon, Jan; Rohm, Witold; Sierny, Jan; Wilgan, Karina; Hadas, Tomasz; Hordyniec, Pawel

    2014-05-01

    The GNSS and Meteo group at Wroclaw University of Environmental and Life Sciences (WUELS), Poland is continuously working on GNSS meteorology since 2010. Currently group maintain real-time (RT) service collecting GNSS and meteorological data and near real-time (NRT) services for estimation of Zenith Troposphere Delay (ZTD), Zenith Hydrostatic Delay (ZHD), Integrated Water Vapour (IWV) and GNSS tomography over the territory of Poland. Data are obtained with high resolution from EUREF Permanent Network (EPN) stations and Ground Base Augmentation System (GBAS) called ASG-EUPOS (www.asgeupos.pl). The GNSS data are available from 124 reference stations located in Poland and neighbour countries, with the average 70km distance between stations. The ground meteorological observations in the area of Poland and neighbour countries are available from: ASG-EUPOS stations included in EUREF Permanent Network (EPN), airport meteorological stations (METAR messages stations) and stations managed by national Institute of Meteorology and Water Management (SYNOP messages stations). The first part of the paper presents the methodology of ASG-EUPOS GNSS data processing for NRT ZTD and ZTD horizontal gradients estimation in double-differenced mode (under Bernese GNSS Software V5.0) as well as new results from PPP mode (under Bernese GNSS Software V5.2) and their validation with respect to Rapid and Final troposphere products. The second part is describing the quality assessment of meteorological parameters interpolation methods for determination of ZHD at GNSS sites performed on GNSS stations equipped with meteorological sensors. The third part concerns on the comparisons of ZTD from GNSS data and meteorological parameters from SYNOP stations with data from COAMPS numerical weather prediction system (NWP) and IWV calculation. The fourth part presents the development of GNSS tomography model TOMO2. The last part describes methods of above products validation and visualization over the

  1. Vapour dynamics during magma-water interaction experiments: hydromagmatic origins of submarine volcaniclastic particles (limu o Pele)

    NASA Astrophysics Data System (ADS)

    Schipper, C. Ian; Sonder, Ingo; Schmid, Andrea; White, James D. L.; Dürig, Tobias; Zimanowski, Bernd; Büttner, Ralf

    2013-03-01

    Recent observations have shattered the long-held theory that deep-sea (>500 m) explosive eruptions are impossible; however, determining the dynamics of unobserved eruptions requires interpretation of the deposits they produce. For accurate interpretation to be possible, the relative abilities of explosive magmatic degassing and non-explosive magma-water interaction to produce characteristic submarine volcaniclastic particles such as `limu o Pele' (bubble wall shards of glass) must be established. We experimentally address this problem by pouring remelted basalt (1300 °C, anhydrous) into a transparent, water-filled reservoir, recording the interaction with a high-speed video camera and applying existing heat transfer models. We performed the experiments under moderate to high degrees of water subcooling (˜8 l of water at 58 and 3 °C), with ˜0.1 to 0.15 kg of melt poured at ˜10-2 kg s-1. Videos show the non-explosive, hydromagmatic blowing and bursting of isolated melt bubbles to form limu o Pele particles that are indistinguishable from those found in submarine volcaniclastic deposits. Pool boiling around growing melt bubbles progresses from metastable vapour film insulation, through vapour film retraction/collapse, to direct melt-water contact. These stages are linked to the evolution of melt-water heat transfer to verify the inverse relationship between vapour film stability and the degree of water subcooling. The direct contact stage in particular explains the extremely rapid quench rates determined from glass relaxation speedometry for natural limu. Since our experimentally produced limu is made entirely by the entrapping of ambient water in degassed basaltic melt, we argue that the presence of fast-quenched limu o Pele in natural deposits is not diagnostic of volatile-driven explosive eruptions. This must be taken into account if submarine eruption dynamics are to be accurately inferred from the deposits and particles they produce.

  2. The impact of temperature resolution on trajectory modeling of stratospheric water vapour

    NASA Astrophysics Data System (ADS)

    Wang, T.; Dessler, A. E.; Schoeberl, M. R.; Randel, W. J.; Kim, J.-E.

    2014-11-01

    Lagrangian trajectories driven by reanalysis meteorological fields are frequently used to study water vapour (H2O) in the stratosphere, in which the tropical cold-point temperatures regulate H2O amount entering the stratosphere. Therefore, the accuracy of temperatures in the tropical tropopause layer (TTL) is of great importance for trajectory studies. Currently, most reanalyses, such as the NASA MERRA (Modern Era Retrospective-Analysis for Research and Applications), only provide temperatures with ~1.2 km vertical resolution in the TTL, which has been argued to introduce uncertainties in the simulations. In this paper, we quantify this uncertainty by comparing the trajectory results using MERRA temperatures on model levels (traj.MER-T) to those using temperatures in finite resolutions, including GPS temperatures (traj.GPS-T) and MERRA temperatures adjusted to recover wave-induced variability underrepresented by the current ~1.2 km vertical resolution (traj.MER-Twave). Comparing with traj.MER-T, traj.GPS-T has little impact on simulated stratospheric H2O (changes ~0.1 ppmv), whereas traj.MER-Twave tends to dry air by 0.2-0.3 ppmv. The bimodal dehydration peaks in traj.MER-T due to limited vertical resolution disappear in traj.GPS-T and traj.MER-Twave by allowing the cold-point tropopause to be found at finer vertical levels. Despite these differences in absolute values of predicted H2O and vertical dehydration patterns, there is virtually no difference in the interannual variability in different runs. Overall, we find that the finite resolution of temperature has limited impact on predicted H2O in the trajectory model.

  3. Modelling the Effect of Fruit Growth on Surface Conductance to Water Vapour Diffusion

    PubMed Central

    GIBERT, CAROLINE; LESCOURRET, FRANÇOISE; GÉNARD, MICHEL; VERCAMBRE, GILLES; PÉREZ PASTOR, ALEJANDRO

    2005-01-01

    • Background and Aims A model of fruit surface conductance to water vapour diffusion driven by fruit growth is proposed. It computes the total fruit conductance by integrating each of its components: stomata, cuticle and cracks. • Methods The stomatal conductance is computed from the stomatal density per fruit and the specific stomatal conductance. The cuticular component is equal to the proportion of cuticle per fruit multiplied by its specific conductance. Cracks are assumed to be generated when pulp expansion rate exceeds cuticle expansion rate. A constant percentage of cracks is assumed to heal each day. The proportion of cracks to total fruit surface area multiplied by the specific crack conductance accounts for the crack component. The model was applied to peach fruit (Prunus persica) and its parameters were estimated from field experiments with various crop load and irrigation regimes. • Key Results The predictions were in good agreement with the experimental measurements and for the different conditions (irrigation and crop load). Total fruit surface conductance decreased during early growth as stomatal density, and hence the contribution of the stomatal conductance, decreased from 80 to 20 % with fruit expansion. Cracks were generated for fruits exhibiting high growth rates during late growth and the crack component could account for up to 60 % of the total conductance during the rapid fruit growth. The cuticular contribution was slightly variable (around 20 %). Sensitivity analysis revealed that simulated conductance was highly affected by stomatal parameters during the early period of growth and by both crack and stomatal parameters during the late period. Large fruit growth rate leads to earlier and greater increase of conductance due to higher crack occurrence. Conversely, low fruit growth rate accounts for a delayed and lower increase of conductance. • Conclusions By predicting crack occurrence during fruit growth, this model could be helpful

  4. Coupled Oxygen and Hydrogen Isotope Analysis of Water Along the Soil-Plant- Atmosphere Continuum

    NASA Astrophysics Data System (ADS)

    Huang, Z.; Webb, E. A.; Longstaffe, F. J.

    2008-12-01

    The oxygen and hydrogen isotope compositions of water within a plant vary with transpiration rates and the isotopic composition of soil water. Both of these parameters are affected by temperature and relative humidity. A controlled-temperature, growth-chamber experiment was conducted to determine the relationships among temperature, relative humidity, soil water evaporation and plant-water isotope composition in cattails and horsetails. Typha, a cattail species that grows in wetland conditions, and Equisetum, a horsetail species that prefers dry soils, were each grown in four chambers at 15, 20, 25 and 30 degrees Celsius. The oxygen and hydrogen isotope compositions of watering water, soil water, vapour in the growth chambers and plant water from the leaves and stems were analyzed throughout the eight-month long artificial growing season. Although the oxygen isotope composition of the watering water remained constant, the soil water, atmospheric vapour and plant water were progressively enriched in oxygen-18 and deuterium in each of the four chambers from low to high temperatures as a result of increasing evaporation. The oxygen isotope composition of plant water along the length of a single stem or leaf was increasingly enriched in the heavier isotopes towards the apex. There was no significant difference in the magnitude of this trend between species. These results indicate that the isotopic composition of plant water is primarily controlled by environmental conditions. The oxygen isotope composition of the water vapour in the growing chamber increased with temperature, consistent with equilibration between the vapour and the oxygen-18 enriched soil and plant water reservoirs. The magnitude and interaction of these variables, as measured for these modern samples of cattails and horsetails, should be useful in calibrating paleoclimate proxies based on fossilized plant materials (e.g., cellulose, phytoliths).

  5. The role of molecular hydrogen and methane oxidation in the water vapour budget of the stratosphere

    NASA Technical Reports Server (NTRS)

    Le Texier, H.; Solomon, S.; Garcia, R. R.

    1988-01-01

    The detailed photochemistry of methane oxidation has been studied in a coupled chemical/dynamical model of the middle atmosphere. The photochemistry of formaldehyde plays an important role in determining the production of water vapor from methane oxidation. At high latitudes, the production and transport of molecular hydrogen is particularly important in determining the water vapor distribution. It is shown that the ratio of the methane vertical gradient to the water vapor vertical gradient at any particular latitude should not be expected to be precisely 2, due both to photochemical and dynamical effects. Modeled H2O profiles are compared with measurements from the Limb Infrared Monitor of the Stratosphere (LIMS) experiment at various latitudes. Molecular hydrogen is shown to be responsible for the formation of a secondary maximum displayed by the model water vapor profiles in high latitude summer, a feature also found in the LIMS data.

  6. Partitioning understory evapotranspiration in semi-arid ecosystems in Namibia using the isotopic composition of water vapour

    NASA Astrophysics Data System (ADS)

    de Blécourt, Marleen; Gaj, Marcel; Holtorf, Kim-Kirsten; Gröngröft, Alexander; Brokate, Ralph; Himmelsbach, Thomas; Eschenbach, Annette

    2016-04-01

    In dry environments with a sparse vegetation cover, understory evapotranspiration is a major component of the ecosystem water balance. Consequently, knowledge on the size of evapotranspiration fluxes and the driving factors is important for our understanding of the hydrological cycle. Understory evapotranspiration is made up of soil evaporation and plant transpiration. Soil evaporation can be measured directly from patches free of vegetation. However, when understory vegetation is present distinguishing between soil evaporation and plant transpiration is challenging. In this study, we aim to partition understory evapotranspiration based on an approach that combines the measurements of water-vapour fluxes using the closed chamber method with measurements of the isotopic composition of water vapour. The measurements were done in the framework of SASSCAL (Southern African Science Service Centre for Climate Change and Adaptive Land Management). The study sites were located in three different semi-arid ecosystems in Namibia: thornbush savanna, Baikiaea woodland and shrubland. At each site measurements were done under tree canopies as well as at unshaded areas between the canopies. We measured evaporation from the bare soil and evapotranspiration from patches covered with herbaceous species and shrubs using a transparent chamber connected with an infrared gas analyser (LI-8100A, LICOR Inc.). The stable isotope composition of water vapour inside the chamber and depth profiles of soil water stable isotopes were determined in-situ using a tuneable off-axis integrated cavity output spectroscope (OA-ICOS, Los Gatos Research, DLT 100). Xylem samples were extracted using the cryogenic vacuum extraction method and the isotopic composition of the extracted water was measured subsequently with a cavity-ring-down spectrometer (CRDS L2120-i, Picarro Inc.). We will present the quantified fluxes of understory evapotranspiration measured in the three different ecosystems, show the

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

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, H. C.; Johnsen, S. J.; Masson-Delmotte, V.; Stenni, B.; Risi, C.; Sodemann, H.; Balslev-Clausen, D.; Blunier, T.; Dahl-Jensen, D.; Ellehøj, M. D.; Falourd, S.; Gkinis, V.; Grindsted, A.; Jouzel, J.; Popp, T.; Sheldon, S.; Simonsen, S. B.; Sjolte, J.; Steffensen, J. P.; Sperlich, P.; Sveinbjörnsdóttir, A. E.; Vinther, B. M.; White, J. W. C.

    2013-01-01

    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.

  8. The Effect of Climate Change on Ozone Depletion through Changes in Stratospheric Water Vapour

    NASA Technical Reports Server (NTRS)

    Kirk-Davidoff, Daniel B.; Hintsa, Eric J.; Anderson, James G.; Keith, David W.

    1999-01-01

    Several studies have predicted substantial increases in Arctic ozone depletion due to the stratospheric cooling induced by increasing atmospheric CO2 concentrations. But climate change may additionally influence Arctic ozone depletion through changes in the water vapor cycle. Here we investigate this possibility by combining predictions of tropical tropopause temperatures from a general circulation model with results from a one-dimensional radiative convective model, recent progress in understanding the stratospheric water vapor budget, modelling of heterogeneous reaction rates and the results of a general circulation model on the radiative effect of increased water vapor. Whereas most of the stratosphere will cool as greenhouse-gas concentrations increase, the tropical tropopause may become warmer, resulting in an increase of the mean saturation mixing ratio of water vapor and hence an increased transport of water vapor from the troposphere to the stratosphere. Stratospheric water vapor concentration in the polar regions determines both the critical temperature below which heterogeneous reactions on cold aerosols become important (the mechanism driving enhanced ozone depletion) and the temperature of the Arctic vortex itself. Our results indicate that ozone loss in the later winter and spring Arctic vortex depends critically on water vapor variations which are forced by sea surface temperature changes in the tropics. This potentially important effect has not been taken into account in previous scenarios of Arctic ozone loss under climate change conditions.

  9. Positive water vapour feedback in climate models confirmed by satellite data

    NASA Technical Reports Server (NTRS)

    Rind, D.; Lerner, J.; Chiou, E.-W.; Chu, W.; Larsen, J.; Mccormick, M. P.; Mcmaster, L.

    1991-01-01

    It has recently been suggested that GCMs used to evaluate climate change overestimate the greenhouse effect due to increased concentrations of trace gases in the atmosphere. Here, new satellite-generated water vapor data are used to compare summer and winter moisture values in regions of the middle and upper troposphere that have previously been difficult to observe with confidence. It is found that, as the hemispheres warm, increased convection leads to increased water vapor above 500 mbar in approximate quantitative agreement with results from current climate models. The same conclusion is reached by comparing the tropical western and eastern Pacific regions. Thus, water vapor feedback is not overestimated in models and should amplify the climate response to increased trace-gas concentrations.

  10. Assessment of small-scale integrated water vapour variability during HOPE

    NASA Astrophysics Data System (ADS)

    Steinke, S.; Eikenberg, S.; Löhnert, U.; Dick, G.; Klocke, D.; Di Girolamo, P.; Crewell, S.

    2015-03-01

    The spatio-temporal variability of integrated water vapour (IWV) on small scales of less than 10 km and hours is assessed with data from the 2 months of the High Definition Clouds and Precipitation for advancing Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE). The statistical intercomparison of the unique set of observations during HOPE (microwave radiometer (MWR), Global Positioning System (GPS), sun photometer, radiosondes, Raman lidar, infrared and near-infrared Moderate Resolution Imaging Spectroradiometer (MODIS) on the satellites Aqua and Terra) measuring close together reveals a good agreement in terms of random differences (standard deviation ≤1 kg m-2) and correlation coefficient (≥ 0.98). The exception is MODIS, which appears to suffer from insufficient cloud filtering. For a case study during HOPE featuring a typical boundary layer development, the IWV variability in time and space on scales of less than 10 km and less than 1 h is investigated in detail. For this purpose, the measurements are complemented by simulations with the novel ICOsahedral Nonhydrostatic modelling framework (ICON), which for this study has a horizontal resolution of 156 m. These runs show that differences in space of 3-4 km or time of 10-15 min induce IWV variabilities on the order of 0.4 kg m-2. This model finding is confirmed by observed time series from two MWRs approximately 3 km apart with a comparable temporal resolution of a few seconds. Standard deviations of IWV derived from MWR measurements reveal a high variability (> 1 kg m-2) even at very short time scales of a few minutes. These cannot be captured by the temporally lower-resolved instruments and by operational numerical weather prediction models such as COSMO-DE (an application of the Consortium for Small-scale Modelling covering Germany) of Deutscher Wetterdienst, which is included in the comparison. However, for time scales larger than 1 h, a sampling resolution of 15 min is

  11. Assessment of small-scale integrated water vapour variability during HOPE

    NASA Astrophysics Data System (ADS)

    Steinke, S.; Eikenberg, S.; Löhnert, U.; Dick, G.; Klocke, D.; Di Girolamo, P.; Crewell, S.

    2014-09-01

    The spatio-temporal variability of integrated water vapour (IWV) on small-scales of less than 10 km and hours is assessed with data from the two months of the High Definition Clouds and Precipitation for advancing Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE). The statistical intercomparison of the unique set of observations during HOPE (microwave radiometer (MWR), Global Positioning System (GPS), sunphotometer, radiosondes, Raman Lidar, infrared and near infrared Moderate Resolution Imaging Spectroradiometer (MODIS) on the satellites Aqua and Terra) measuring close together reveals a good agreement in terms of standard deviation (≤ 1 kg m-2) and correlation coefficient (≥ 0.98). The exception is MODIS, which appears to suffer from insufficient cloud filtering. For a case study during HOPE featuring a typical boundary layer development, the IWV variability in time and space on scales of less than 10 km and less than 1 h is investigated in detail. For this purpose, the measurements are complemented by simulations with the novel ICOsahedral Non-hydrostatic modelling framework (ICON) which for this study has a horizontal resolution of 156 m. These runs show that differences in space of 3-4 km or time of 10-15 min induce IWV variabilities in the order of 4 kg m-2. This model finding is confirmed by observed time series from two MWRs approximately 3 km apart with a comparable temporal resolution of a few seconds. Standard deviations of IWV derived from MWR measurements reveal a high variability (> 1 kg m-2) even at very short time scales of a few minutes. These cannot be captured by the temporally lower resolved instruments and by operational numerical weather prediction models such as COSMO-DE (an application of the Consortium for Small-scale Modelling covering Germany) of Deutscher Wetterdienst, which is included in the comparison. However, for time scales larger than 1 h, a sampling resolution of 15 min is sufficient to capture the

  12. Evaluation of Trichloroethylene vapour fluxes using measurements at the soil-air interface and in the atmosphere close to the soil surface

    NASA Astrophysics Data System (ADS)

    Cotel, Solenn; Nagel, Vincent; Schäfer, Gerhard; Marzougui, Salsabil; Razakarisoa, Olivier; Millet, Maurice

    2013-04-01

    Industrialization during the 19th and 20th century led to the use of chemical products such as chlorinated solvents, e.g., trichloroethylene (TCE). At locations where volatile organic compounds were accidentally spilled on the soil during transport or leaked from their storage places, they could have migrated vertically through the unsaturated zone towards the underlying groundwater. As a result of their high volatility a large vapour plume is consequently formed. Understanding when, at which concentrations and how long, these pollutants will be present in soil, groundwater, atmosphere or indoor air, still remains a challenge up to date. This study was conducted as part of a broader experiment of TCE multiphase mass transfer in a large (25m×12m×3m) well-instrumented artificial basin. TCE was injected as liquid phase in the vadose zone and experiments were conducted during several months. Firstly, TCE vapour fluxes were experimentally determined in two different ways: (a) direct measurements at the soil-air interface using a flux chamber and (b) evaluations based on measurements of TCE concentrations in the air above the soil surface using a modular experimental flume (5m×1m×1m) with a fixed air flow. Secondly, numerical simulations were conducted to analyse the differences between these two types of fluxes. Several positions of the flume on the soil surface were tested. Based on the TCE concentrations measured in the air, vapour fluxes were determined with the aerodynamic method using the modified Thornthwaite-Holzmann equation. It assumes that the concentrations and velocities are temporally and spatially constant in horizontal planes and requires data on the gradients of concentration, horizontal wind velocity and temperature. TCE vapour fluxes measured at the soil-air interface decrease with distance from the source zone. However, this decrease was either high, at the first stage of experiment (120μg/(m2s) near the source zone compared to 1,1μg/(m2s) 2m

  13. Evaluation of balloon and satellite water vapour measurements in the Southern tropical and subtropical UTLS during the HIBISCUS campaign

    NASA Astrophysics Data System (ADS)

    Montoux, N.; Hauchecorne, A.; Pommereau, J.-P.; Lefèvre, F.; Durry, G.; Jones, R. L.; Rozanov, A.; Dhomse, S.; Burrows, J. P.; Morel, B.; Bencherif, H.

    2009-07-01

    Balloon water vapour in situ and remote measurements in the tropical upper troposphere and lower stratosphere (UTLS) obtained during the HIBISCUS campaign around 20° S in Brazil in February-March 2004 using a tunable diode laser (μSDLA), a surface acoustic wave (SAW) and a Vis-NIR solar occultation spectrometer (SAOZ) on a long duration balloon, have been used for evaluating the performances of satellite borne remote water vapour instruments available at the same latitude and measurement period. In the stratosphere, HALOE displays the best precision (2.5%), followed by SAGE II (7%), MIPAS (10%), SAOZ (20-25%) and SCIAMACHY (35%), all of which show approximately constant H2O mixing ratios between 20-25 km. Compared to HALOE of ±10% accuracy between 0.1-100 hPa, SAGE II and SAOZ show insignificant biases, MIPAS is wetter by 10% and SCIAMACHY dryer by 20%. The currently available GOMOS profiles of 25% precision show a positive vertical gradient in error for identified reasons. Compared to these, the water vapour of the Reprobus Chemistry Transport Model, forced at pressures higher than 95 hPa by the ECMWF analyses, is dryer by about 1 ppmv (20%). In the lower stratosphere between 16-20 km, most notable features are the steep degradation of MIPAS precision below 18 km, and the appearance of biases between instruments far larger than their quoted total uncertainty. HALOE and SAGE II (after spectral adjustment for reducing the bias with HALOE at northern mid-latitudes) both show decreases of water vapour with a minimum at the tropopause not seen by other instruments or the model, possibly attributable to an increasing error in the HALOE altitude registration. Between 16-18 km where the water vapour concentration shows little horizontal variability, and where the μSDLA balloon measurements are not perturbed by outgassing, the average mixing ratios reported by the remote sensing instruments are substantially lower than the 4-5 ppmv observed by the μSDLA. Differences

  14. In situ measurements of nitric oxide, water vapour and ozone from an aircraft

    NASA Technical Reports Server (NTRS)

    Briehl, D. C.; Hilsenrath, E.; Ridley, B. A.; Schiff, H. I.

    1974-01-01

    This paper describes flight tests of prototype instruments for the NASA global atmospheric sampling program (GASP). Three gas sampling instruments were included in the installation: (1) a chemiluminescent nitric oxide monitor; (2) an ultraviolet absorption ozone monitor; and (3) an aluminum oxide water vapor hygrometer. Results indicate the range and kind of variability in NO, H2O, and O3 that can be expected in routine tropospheric air sampling. They have also demonstrated the need for increasing instrument sensitivities, particularly in NO measurement.

  15. Precipitable water vapour contents at "local" scale: a comparative study on GNSS-derived data versus modelled ones from ECMWF operational models

    NASA Astrophysics Data System (ADS)

    Riccardi, Umberto; Tammaro, Umberto; Boy, Jean-Paul; Masson, Frederic; Capuano, Paolo

    2016-04-01

    We present a comparative study between GNSS-derived precipitable water (PW) contents and modelled data from ECMWF operational models. Nearly 4 years of PW contents derived from meteorological and GNSS data are analyzed. We use GNSS data from a geodetic monitoring network of the Neapolitan active volcanoes managed by INGV as well as from some GPS stations installed on purpose. We compare PW time series retrieved from GNSS observations with those coming from models. The total water vapour content of the atmosphere can be derived by modelling from the vertical profile of the specific humidity. We use ECMWF operational models available at a horizontal resolution of about 15 km, 3-hourly samples. The number of vertical model levels is 91 up to mid 2013 and 137 afterwards. We recomputed the surface pressure on the real Earth surface, which differs from the orography, i.e. the smooth surface of the atmospheric model, by propagating the pressure from the orography to the surface. A very good agreement is achieved between PW retrieved from GNSS observations and computed from models using the highest time and space resolution (0.15 degree, 3-hourly 91-137 layers) operational models. We even focus our analysis on the occasion of some extreme raining events hitting Campania region (Italy).

  16. A high-resolution extraterrestrial solar spectrum and water vapour continuum at near infrared wavelengths from ground-based spectrometer measurements

    NASA Astrophysics Data System (ADS)

    Menang, K. P.

    A high resolution extraterrestrial solar spectrum (CAVIAR solar spectrum) and water vapour continuum have been derived in near infrared windows from 2000-10000 cm-1 (105μm), by applying the Langley technique to calibrated ground-based high-resolution Fourier transform spectrometer measurements, made under clear-sky conditions. The effect of the choice of an extraterrestrial solar spectrum for radiative transfer calculations of clear-sky absorption and heating rates in the near infrared was also studied. There is a good agreement between the solar lines strengths and positions of the CAVIAR solar spectrum and those from both high-resolution satellite and ground-based measurements in their regions of spectral overlap. However, there are significant differences between the structure of the CAVIAR solar spectrum and spectra from models. Many of the detected lines are missing from widely-used modelled extraterrestrial solar spectrum. The absolute level and hence wavenumber-integrated solar irradiance of the CAVIAR solar spectrum was also found to be 8% lower than the satellite-based Thuillier et al spectra from 5200-10000 cm-1. Using different extraterrestrial solar spectra for radiative transfer calculations in the near infrared led to differences of up to about 11 W m-2 (8.2%) in the absorbed solar irradiance while the tropospheric and stratospheric heating rates could respectively differ by up to about 0.13K day-1 (8.1%) and 0.19 K day-1 (7.6%) for an overhead Sun and mid-latitude summer atmosphere. This work has shown that the widely-used empirically modelled continuum may be underestimating the strength of the water vapour continuum from 2000-10000 cm-1, with the derived continuum up to more than 2 orders of magnitude stronger at some wavenumbers in the windows. The derived continuum is also stronger than that implied by laboratory measurements, by a factor of up to 40 in some spectral regions.

  17. The GEWEX water vapour assessment (G-VAP) - first results from inter-comparisons and stability analysis.

    NASA Astrophysics Data System (ADS)

    Schröder, Marc; Lockhoff, Maarit; Shi, Lei; Fennig, Karsten

    2014-05-01

    In a Joint Letter from the Global Climate Observing System (GCOS) and the World Climate Research Programme (WCRP) the general need for coordinated international assessments of climate products was formulated. Such assessments are important mechanisms for improvements and to enhance and promote utilisation. The GEWEX Radiation Panel (GRP, renamed to GEWEX Data and Assessment Panel - GDAP) has initiated a Water Vapor Assessment in 2011, further on referred to as G-VAP. The major purpose of G-VAP is to: • Quantify the state of the art in water vapour products being constructed for climate applications, and by this; • Support the selection process of suitable water vapour products by GDAP for its production of globally consistent water and energy cycle products. The usage of products within GDAP activities essentially implies to study long-term data records. Since the start of G-VAP in 2011 two workshops have been conducted. The results of these workshops together with feedback from the first GDAP meeting were used for setting up the G-VAP assessment plan. This plan (available at www.gewex-vap.org) summarizes scope and goals of the assessement, introduces science questions and provides details on the planned technical and scientific activities. Major elements of G-VAP are: • All three parts of the GCOS Essential Climate Variables (ECV) on water vapour and their consistency are considered: Total Column Water Vapour, Upper Tropospheric Humidity as well as water vapour profiles and their related temperature profiles; • The assessment focuses on overall characteristics of participating satellite data records and reanalyses as determined from inter-comparison and comparisons against in situ observations as well as against ground-based products; • In this characterisation process the data records are not ranked according to their quality. Rather, the application areas and requirements of the individual data records as well as the GEWEX requirements are documented

  18. Effect of temperature and relative humidity on the water vapour permeability and mechanical properties of cassava starch and soy protein concentrate based edible films.

    PubMed

    Chinma, C E; Ariahu, C C; Alakali, J S

    2015-04-01

    The effect of temperature and relative humidity on the water vapour permeability (WVP) and mechanical properties of cassava starch and soy protein concentrate (SPC) based edible films containing 20 % glycerol level were studied. Tensile strength and elastic modulus of edible films increased with increase in temperature and decreased with increase in relative humidity, while elongation at break decreased. Water vapour permeability of the films increased (2.6-4.3 g.mm/m(2).day.kPa) with increase in temperature and relative humidity. The temperature dependence of water vapour permeation of cassava starch-soy protein concentrate films followed Arrhenius relationship. Activation energy (Ea) of water vapour permeation of cassava starch-soy protein concentrate edible films ranged from 1.9 to 5.3 kJ/mol (R (2)  ≥ 0.93) and increased with increase in SPC addition. The Ea values were lower for the bio-films than for polyvinylidene chloride, polypropylene and polyethylene which are an indication of low water vapour permeability of the developed biofilms compared to those synthetic films. PMID:25829623

  19. INTRODUCTION: Anticipated changes in the global atmospheric water cycle

    NASA Astrophysics Data System (ADS)

    Allan, Richard P.; Liepert, Beate G.

    2010-06-01

    The atmospheric branch of the water cycle, although containing just a tiny fraction of the Earth's total water reserves, presents a crucial interface between the physical climate (such as large-scale rainfall patterns) and the ecosystems upon which human societies ultimately depend. Because of the central importance of water in the Earth system, the question of how the water cycle is changing, and how it may alter in future as a result of anthropogenic changes, present one of the greatest challenges of this century. The recent Intergovernmental Panel on Climate Change report on Climate Change and Water (Bates et al 2008) highlighted the increasingly strong evidence of change in the global water cycle and associated environmental consequences. It is of critical importance to climate prediction and adaptation strategies that key processes in the atmospheric water cycle are precisely understood and determined, from evaporation at the surface of the ocean, transport by the atmosphere, condensation as cloud and eventual precipitation, and run-off through rivers following interaction with the land surface, sub-surface, ice, snow and vegetation. The purpose of this special focus issue of Environmental Research Letters on anticipated changes in the global atmospheric water cycle is to consolidate the recent substantial advances in understanding past, present and future changes in the global water cycle through evidence built upon theoretical understanding, backed up by observations and borne out by climate model simulations. Thermodynamic rises in water vapour provide a central constraint, as discussed in a guest editorial by Bengtsson (2010). Theoretical implications of the Clausius-Clapeyron equation are presented by O'Gorman and Muller (2010) and with reference to a simple model (Sherwood 2010) while observed humidity changes confirm these anticipated responses at the land and ocean surface (Willett et al 2008). Rises in low-level moisture are thought to fuel an

  20. Photocatalytic property of titanium dioxide thin films deposited by radio frequency magnetron sputtering in argon and water vapour plasma

    NASA Astrophysics Data System (ADS)

    Sirghi, L.; Hatanaka, Y.; Sakaguchi, K.

    2015-10-01

    The present work is investigating the photocatalytic activity of TiO2 thin films deposited by radiofrequency magnetron sputtering of a pure TiO2 target in Ar and Ar/H2O (pressure ratio 40/3) plasmas. Optical absorption, structure, surface morphology and chemical structure of the deposited films were comparatively studied. The films were amorphous and included a large amount of hydroxyl groups (about 5% of oxygen atoms were bounded to hydrogen) irrespective of the intentional content of water in the deposition chamber. Incorporation of hydroxyl groups in the film deposited in pure Ar plasma is explained as contamination of the working gas with water molecules desorbed by plasma from the deposition chamber walls. However, intentional input of water vapour into the discharge chamber decreased the deposition speed and roughness of the deposited films. The good photocatalytic activity of the deposited films could be attributed hydroxyl groups in their structures.

  1. Determination of permeation parameters of experimental PET films coated with SiOx to ethyl acetate, oxygen and water vapour.

    PubMed

    Adamantiadi, A; Badeka, A; Kontominas, M G

    2001-11-01

    The permeation parameters of conventional PET films, films coated with SiOx and SiOx-coated films laminated to LDPE were determined for ethyl acetate using the permeation cell/gas chromatography method. Permeation to O2 and water vapour was also determined to monitor overall changes in the barrier properties of the experimental films. Coating of the PET film was achieved by a 'directed evaporation' method that increased the yield of the coating process from 30-35 to > 70%. It was shown that the SiOx coating increased the film barrier to ethyl acetate by approximately 20-30 times. Permeation values showed low reproducibility, indicating the need for further development and standardization of the 'directed evaporation' web-coating process. The barrier to oxygen and water vapour increased by 20-25 and 12-14 times respectively after coating. The web-coating speed did not seem to influence the barrier properties of the films. Permeation coefficients, diffusion coefficients and solubility coefficients were calculated for all samples. PMID:11665733

  2. Radiometric Investigation of Water Vapour Movement in Wood-based Composites by Means of Cold and Thermal Neutrons

    NASA Astrophysics Data System (ADS)

    Solbrig, K.; Frühwald, K.; Ressel, J. B.; Mannes, D.; Schillinger, B.; Schulz, M.

    Wood-based composites are industrially produced panels made of resin-blended wood furnish material consolidated by hot pressing. Precise knowledge of the physical interrelations, such as heat and mass transfer induced densification and curing, are inevitable to control process performance and final product properties. Neutron radiography is able to distinguish between moisture and wood matter movement and thus to provide quantitative information considering the hot pressing process where only models exist. To this end, preliminary experiments were carried out utilising both cold and thermal neutrons to visualise and to quantify the water vapour movement within wood-based composites heated under sealing within a simplified mimicry of the hot pressing process conditions. Neutron radiography of this rather fast process was found to be feasible in general. The evaluation of the time-resolved image data maps the relative water content distribution within the sample during 9 min process time. A presumed wavefront-like vapour movement was confirmed. Hence, the results enhance the understanding of heat and mass transfer inside consolidated resin-blended wood furnish. These preliminary experiments prove neutron radiography as viable method for further comprehensive in-situ investigations of the hot pressing process of wood-based composites.

  3. Profiling atmospheric water vapor by microwave radiometry

    NASA Technical Reports Server (NTRS)

    Wang, J. R.; Wilheit, T. T.; Szejwach, G.; Gesell, L. H.; Nieman, R. A.; Niver, D. S.; Krupp, B. M.; Gagliano, J. A.; King, J. L.

    1983-01-01

    High-altitude microwave radiometric observations at frequencies near 92 and 183.3 GHz were used to study the potential of retrieving atmospheric water vapor profiles over both land and water. An algorithm based on an extended kalman-Bucy filter was implemented and applied for the water vapor retrieval. The results show great promise in atmospheric water vapor profiling by microwave radiometry heretofore not attainable at lower frequencies.

  4. Water for food and nature in drought-prone tropics: vapour shift in rain-fed agriculture.

    PubMed Central

    Rockström, Johan

    2003-01-01

    This paper quantifies the eco-hydrological challenge up until 2050 of producing food in balance with goods and services generated by water-dependent ecosystems in nature. Particular focus is given to the savannah zone, covering 40% of the land area in the world, where water scarcity constitutes a serious constraint to sustainable development. The analysis indicates an urgent need for a new green revolution, which focuses on upgrading rain-fed agriculture. Water requirements to produce adequate diets for humans are shown to be relatively generic irrespective of hydro-climate, amounting to a global average of 1,300 m(3) cap(-1) yr(-1). Present food production requires an estimated 6,800 km(3) yr(-1) of consumptive green water (5,000 km(3) yr(-1) in rain-fed agriculture and 1,800 km(3) yr(-1) from irrigated crops). Without considering water productivity gains, an additional 5,800 km(3) yr(-1) of water is needed to feed a growing population in 2,050 and eradicate malnutrition. It is shown that the bulk of this water will be used in rain-fed agriculture. A dynamic analysis of water productivity and management options indicates that large 'crop per drop' improvements can be achieved at the farm level. Vapour shift in favour of productive green water flow as crop transpiration could result in relative water savings of 500 km(3) yr(-1) in semi-arid rain-fed agriculture. PMID:14728794

  5. Effects of ultraviolet irradiation, pulsed electric field, hot water and ethanol vapours treatment on functional properties of mung bean sprouts.

    PubMed

    Goyal, Ankit; Siddiqui, Saleem; Upadhyay, Neelam; Soni, Jyoti

    2014-04-01

    The present investigation was conducted with the objective to study the effects of various treatments and storage conditions on ascorbic acid, total phenols, antioxidant activity and polyphenol oxidase activity of mung bean sprouts. The sprouts subjected to various treatments viz., pulsed electric field (PEF) (10,000 V for 10 s), hot water dip (HWD) (50 °C for 2 min), ethanol vapours (1 h) and UV-Irradiation (10 kJm(-2) in laminar flow chamber for 1 h); and then stored at room (25 ± 1 °C) and low (7 ± 1 °C) temperature conditions. The sprouts were analyzed regularly at 24 h interval till end of shelf life. Different treatments given to sprouts resulted in differential effect on various parameters. The ascorbic acid, total phenols and antioxidant activity were highest in ethanol vapours treated sprouts. There was a general decrease in polyphenol oxidase activity by various treatments. During storage ascorbic acid, total phenols and antioxidant activity of sprouts first increased and then decreased significantly, however, for polyphenol oxidase activity a progressive increase with increase in storage period was observed. The trends were similar at room and low temperature storage conditions. Thus, it can be concluded that the ethanol vapours significantly improved the ascorbic acid content, total phenols and antioxidant activity of mung bean sprouts, both at room as well as low temperature conditions of storage. PMID:24741164

  6. Observations of precipitable water vapour over complex topography of Ethiopia from ground-based GPS, FTIR, radiosonde and ERA-Interim reanalysis

    NASA Astrophysics Data System (ADS)

    Mengistu Tsidu, G.; Blumenstock, T.; Hase, F.

    2015-08-01

    Water vapour is one of the most important greenhouse gases. Long-term changes in the amount of water vapour in the atmosphere need to be monitored not only for its direct role as a greenhouse gas but also because of its role in amplifying other feedbacks such as clouds and albedo. In recent decades, monitoring of water vapour on a regular and continuous basis has become possible as a result of the steady increase in the number of deployed global positioning satellite (GPS) ground-based receivers. However, the Horn of Africa remained a data-void region in this regard until recently, when some GPS ground-receiver stations were deployed to monitor tectonic movements in the Great Rift Valley. This study seizes this opportunity and the installation of a Fourier transform infrared spectrometer (FTIR) at Addis Ababa to assess the quality and comparability of precipitable water vapour (PWV) from GPS, FTIR, radiosonde and interim ECMWF Re-Analysis (ERA-Interim) over Ethiopia. The PWV from the three instruments and the reanalysis show good correlation, with correlation coefficients in the range from 0.83 to 0.92. On average, GPS shows the highest PWV followed by FTIR and radiosonde observations. ERA-Interim is higher than all measurements with a bias of 4.6 mm compared to GPS. The intercomparison between GPS and ERA-Interim was extended to seven other GPS stations in the country. Only four out of eight GPS stations included simultaneous surface pressure observations. Uncertainty in the model surface pressure of 1 hPa can cause up to 0.35 mm error in GPS PWV. The gain obtained from using observed surface pressure in terms of reducing bias and strengthening correlation is significant but shows some variations among the GPS sites. The comparison between GPS and ERA-Interim PWV over the seven other GPS stations shows differences in the magnitude and sign of bias of ERA-Interim with respect to GPS PWV from station to station. This feature is also prevalent in diurnal and seasonal

  7. Carbon and water vapour exchange in a recently burned east boreal jack pine stand, Quebec, Canada

    NASA Astrophysics Data System (ADS)

    Nugent, K.; Strachan, I. B.

    2013-12-01

    The circumpolar boreal forest is an extensive carbon (C) reservoir, storing an estimated 88 petagrams (Pg) of C in vegetation biomass with an additional 471 PgC residing within the soil itself. In the North American boreal, fire disturbance acts as the main stand-renewing agent along an approximate 100-year return interval. However, recent studies suggest that fire intensity and severity are increasing, driven by disproportionate climate warming of the northern latitudes. While estimates of direct C emissions from combustion are becoming more accurate, indirect loss due to post-fire effects on decomposition and regeneration has only recently become a focus of research. Paradoxically, it has been estimated that post-fire C releases are in the order of three times the amount directly released during initial combustion. In this study, we examine carbon and water exchange in a 6-year old, post-burn, jack pine stand located in the eastern James Bay region of the Canadian boreal; an area currently under-represented in fire studies. Over 1.5 years, covering two growing seasons and the spring and fall transitions, we measured net CO2 and energy exchange at the ecosystem level using an eddy covariance tower, and supplemented this with chamber measurements of soil respiration. At this stage of recovery, while demonstrating diurnal and seasonal patterns of exchange, overall the site was a net source of C and water to the atmosphere with brief periods of C sink.

  8. Discussion of band selection and methodologies for the estimation of precipitable water vapour from AVIRIS data

    NASA Technical Reports Server (NTRS)

    Schanzer, Dena; Staenz, Karl

    1992-01-01

    An Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data set acquired over Canal Flats, B.C., on 14 Aug. 1990, was used for the purpose of developing methodologies for surface reflectance retrieval using the 5S atmospheric code. A scene of Rogers Dry Lake, California (23 Jul. 1990), acquired within three weeks of the Canal Flats scene, was used as a potential reference for radiometric calibration purposes and for comparison with other studies using primarily LOWTRAN7. Previous attempts at surface reflectance retrieval indicated that reflectance values in the gaseous absorption bands had the poorest accuracy. Modifications to 5S to use 1 nm step size, in order to make fuller use of the 20 cm(sup -1) resolution of the gaseous absorption data, resulted in some improvement in the accuracy of the retrieved surface reflectance. Estimates of precipitable water vapor using non-linear least squares regression and simple ratioing techniques such as the CIBR (Continuum Interpolated Band Ratio) technique or the narrow/wide technique, which relate ratios of combinations of bands to precipitable water vapor through calibration curves, were found to vary widely. The estimates depended on the bands used for the estimation; none provided entirely satisfactory surface reflectance curves.

  9. Raman water vapour concentration measurements for reduction of false alarms in forest fire detection

    NASA Astrophysics Data System (ADS)

    Bellecci, C.; Gaudio, P.; Gelfusa, M.; Lo Feudo, T.; Malizia, A.; Richetta, M.; Ventura, P.

    2009-09-01

    Forest fires can be the cause of environmental catastrophe, with the natural outcomes of serious ecological and economic damages, together with the possibility to endanger human safety. At the aim to reduce this catastrophe several author have been shown that the Laser light scattering can be uses to reveals the particulate emitted in the smoke. Infact experimental and theoretical investigations have shown that lidar is a powerful tool to detect the tenuous smoke plumes produced by forest fires at an early stage. In early 90's Arbolino and Andreucci have shown the theoretical possibility to detect the particulate emitted in atmosphere from smoke forest fire. Vilar at all have shown experimentally the possibility to measure the density variation in atmosphere due to plume emitted in forest fire event. Gaudio at all. have already shown that it is possible to evaluate water vapor emitted in smoke of vegetable fuel using a CO2 dial system. In this paper a theoretical model to evaluate the capabilities of a lidar system in fire surveillance of wooded areas will be presented. In particular we intend propose a technique to minimizing the false alarm in the detection of forest fire by lidar based on a measurement of second components emitted in a combustion process. Usually to detect a fire alarm a rapid increase of aerosol amount is measured. If the backscattering signal report a peak, the presences of a forest fire will be probable. Our idea to confirm this hypothesis is measure the second components emitted in a forest fire at the aim to minimize the false alarm. The simulated measurements of the humidity amount within the smoke plume will be carried out by means of Raman analysis. Fixing the burning rate of the vegetable-fuels, the maximum range of detection will be evaluated.

  10. Tagging Water Sources in Atmospheric Models

    NASA Technical Reports Server (NTRS)

    Bosilovich, M.

    2003-01-01

    Tagging of water sources in atmospheric models allows for quantitative diagnostics of how water is transported from its source region to its sink region. In this presentation, we review how this methodology is applied to global atmospheric models. We will present several applications of the methodology. In one example, the regional sources of water for the North American Monsoon system are evaluated by tagging the surface evaporation. In another example, the tagged water is used to quantify the global water cycling rate and residence time. We will also discuss the need for more research and the importance of these diagnostics in water cycle studies.

  11. Measurements of Isotopic Composition of Vapour on the Antarctic Plateau

    NASA Astrophysics Data System (ADS)

    Casado, M.; Landais, A.; Masson-Delmotte, V.; Genthon, C.; Prie, F.; Kerstel, E.; Kassi, S.; Arnaud, L.; Steen-Larsen, H. C.; Vignon, E.

    2015-12-01

    The oldest ice core records are obtained on the East Antarctic plateau. The composition in stable isotopes of water (δ18O, δD, δ17O) permits to reconstruct the past climatic conditions over the ice sheet and also at the evaporation source. Paleothermometer accuracy relies on good knowledge of processes affecting the isotopic composition of surface snow in Polar Regions. Both simple models such as Rayleigh distillation and global atmospheric models with isotopes provide good prediction of precipitation isotopic composition in East Antarctica but post deposition processes can alter isotopic composition on site, in particular exchanges with local vapour. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum water vapour - precipitation - surface snow - buried snow. While precipitation and snow sampling are routinely performed in Antarctica, climatic conditions in Concordia, very cold (-55°C in average) and very dry (less than 1000ppmv), impose difficult conditions to measure the water vapour isotopic composition. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces (down to 20ppmv). Here we present the results of a campaign of measurement of isotopic composition in Concordia in 2014/2015. Two infrared spectrometers have been deployed or the first time on top of the East Antarctic Plateau allowing a continuous vapour measurement for a month. Comparison of the results from infrared spectroscopy with cryogenic trapping validates the relevance of the method to measure isotopic composition in dry conditions. Identification of different behaviour of isotopic composition in the water vapour associated to turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction.

  12. Determining Atmospheric Pressure Using a Water Barometer

    NASA Astrophysics Data System (ADS)

    Lohrengel, C. Frederick; Larson, Paul R.

    2012-12-01

    The atmosphere is an envelope of compressible gases that surrounds Earth. Because of its compressibility and nonuniform heating by the Sun, it is in constant motion. The atmosphere exerts pressure on Earth's surface, but that pressure is in constant flux. This experiment allows students to directly measure atmospheric pressure by measuring the mass of the water that is used as the fluid medium in the barometer. Simple calculations based upon the mass of water collected from the barometer yield the mass of the atmosphere per square unit of area at the site where the experiment is conducted.

  13. Applications of a Passive Satellite-borne Microwave Retrieval of Water Vapour Column during the Arctic Winter.

    NASA Astrophysics Data System (ADS)

    Perro, C. W.; Lesins, G. B.; Duck, T. J.; Cadeddu, M. P.

    2015-12-01

    A water vapor column retrieval for use during the Arctic Winter is presented. The retrieval, known as PLDC15, uses data from several passive microwave satellite instruments which measure brightness temperatures near the 183 GHz water vapor absorption line in conjunction with a priori information. Comparisons to a ground truth in Barrow, Alaska, the G-Band Vapor Radiometer (GVR), gives a standard deviation of 0.39 kg m-2 and a bias of 0.07 kg m-2 for water vapor column less than 6 kg m-2. This error is smaller when compared to other microwave techniques and comparable to re-analyses datasets while having a higher spatial resolution (< 40 km) with significantly more structure (See attached figure for water vapour column comparison of a) PLDC15 retrieval and b) Arctic System Reanalysis dataset). Pan-Arctic maps of water vapor column are produced many times daily using the large number of datasets from passive microwave instruments that are available. The PLDC15 retrieval is used for several purposes. A comparison to Arctic Radiosonde measurements of water vapor column is shown to assess the Radiosondes capability of measuring water vapor at various locations in the Arctic in terms of standard deviation and bias. Using the high resolution maps of water vapor column, estimates of water vapor contribution from ice leads can be obtained, particularly in 2013 and 2015 at which time there was a considerable number of leads. The PLDC15 retrieval can further be used to improve re-analysis data sets, for numerical weather prediction models, and water vapor budgets of the Arctic.

  14. Lidar Observations of Low-level Wind Reversals over the Gulf of Lion and Characterization of Their Impact on the Water Vapour Variability

    NASA Astrophysics Data System (ADS)

    Di Girolamo, Paolo; Flamant, Cyrille; Cacciani, Marco; Summa, Donato; Stelitano, Dario; Mancini, Ignazio; Richard, Evelyne; Ducrocq, Véronique; Nuret, Mathieu; Said, Frédérique

    2016-06-01

    Water vapour measurements from a ground-based Raman lidar and an airborne differential absorption lidar, complemented by high resolution numerical simulations from two mesoscale models (Arome-WMED and MESO-NH), are considered to investigate transition events from Mistral/Tramontane to southerly marine flow taking place over the Gulf of Lion in Southern France in the time frame September-October 2012, during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) Special Observation Period 1 (SOP1). Low-level wind reversals associated with these transitions are found to have a strong impact on water vapour transport, leading to a large variability of the water vapour vertical and horizontal distribution. The high spatial and temporal resolution of the lidar data allow to monitor the time evolution of the three-dimensional water vapour field during these transitions from predominantly northerly Mistral/Tramontane flow to a predominantly southerly flow, allowing to identify the quite sharp separation between these flows, which is also quite well captured by the mesoscale models.

  15. Developing and testing a low cost method for high resolution measurements of volcanic water vapour emissions at Vulcano and Mt. Etna

    NASA Astrophysics Data System (ADS)

    Pering, Tom D.; McGonigle, Andrew J. S.; Tamburello, Giancarlo; Aiuppa, Alessandro; Bitetto, Marcello; Rubino, Cosimo

    2015-04-01

    The most voluminous of emissions from volcanoes are from water vapour (H2O) (Carroll and Holloway, 1994), however, measurements of this species receive little focus due to the difficulty of independent measurement, largely a result of high atmospheric background concentrations which often undergo rapid fluctuations. A feasible method of measuring H2O emissions at high temporal and spatial resolutions would therefore be highly valuable. We describe a new and low-cost method combining modified web cameras (i.e. with infrared filters removed) with measurements of temperature and relative humidity to produce high resolution measurements (≈ 0.25 Hz) of H2O emissions. The cameras are affixed with near-infrared filters at points where water vapour absorbs (940 nm) and doesn't absorb (850 nm) incident light. Absorption of H2O is then determined by using Lambert-Beer's law on a pixel by pixel basis, producing a high spatial resolution image. The system is then calibrated by placing a Multi-GAS unit within the gas source and camera field-of-view, which measures; SO2, CO2, H2S and relative humidity. By combining the point measurements of the Multi-GAS unit with pixel values for absorption, first correcting for the width of the gas source (generally a Gaussian distribution), a calibration curve is produced which allows the conversion of absorption values to mass of water within a pixel. In combination with relative humidity measurements made outside of the plume it is then possible to subtract the non-volcanic background H2O concentration to produce a high resolution calibrated volcanic H2O flux. This technique is demonstrated in detail at the active fumarolic system on Vulcano (Aeolian Islands, Italy). Data processing and image acquisition was completed in Matlab® using a purpose built code. The technique is also demonstrated for the plume of the North-East Crater of Mt. Etna (Sicily, Italy). Here, contemporaneously acquired measurements of SO2 using a UV camera, combined

  16. Remote sensing of water vapour from the synergy of Raman lidar, GPS and in-situ observations during the DEMEVAP 2011 campaign

    NASA Astrophysics Data System (ADS)

    Bock, Olivier; David, Leslie; Bosser, Pierre; Thom, Christian; Pelon, Jacques; Keckhut, Philippe; Sarkissian, Alain; Bourcy, Thomas; Tzanos, Diane; Tournois, Guy

    2013-04-01

    The DEMEVAP (DEvelopment of MEthods for remote sensing of water VAPor) project aims at developing improved reference humidity sounding methods based on the combined used of scanning Raman lidars, ground-based sensors and GPS. The goal is to achieve absolute accuracy better than 3% on the column integrated water vapour (IWV). An intensive observing period was conducted in September-October 2011 at Observatoire de Haute Provence (OHP), France, with the aim of intercomparing several different techniques and instruments. It involved two Raman lidars, four radiosonde measurement systems, five GPS stations, a stellar spectrometer, and several ground-based capacitive and dew-point sensors. Observations were collected over 17 nights during which 26 balloons were released which carried a total of 79 radiosondes. Most of the balloons carried 3 or 4 different sonde types simultaneously (Vaisala RS92, MODEM M2K2-DC and M10, and Meteolabor Snow-White). The comparison of IWV measurements from the four radiosonde types to GPS reveals biases of -11% to +7%. Comparison of water vapour profiles from the radiosondes to the IGN scanning Raman lidar profiles reveals mostly dry and wet biases in the radiosondes data in dry layers in the middle and upper troposphere. Several Raman lidar calibration methods are evaluated which adjust the lidar measurements either on ground-based capacitive or dew-point sensors measurements, on radiosonde data or on GPS PWV data. Another method adjusts the lidar calibration constant as an extra parameter during GPS processing. All these methods show a good degree of consistency and yield a repeatability of 2 to 5% during the first 3-week period of the experiment. A drift in the calibration constant is observed throughout the full time of the experiment which is partly explained by a temperature-dependent bias in the lidar measurements induced by the progressive cooling of the atmosphere. Modelling and correcting this effect or modifying the Raman lidar

  17. Retrieval of Land Surface Resistance to Water Vapour Transfer Using Complementary Relationship and Remote Sensing

    NASA Astrophysics Data System (ADS)

    Tanguy, M.; Baille, A. Gonzalez-Real, M.; Taylor, C.

    2011-01-01

    In this study, we propose an alternative way to derive the surface-to-air gradient of vapour pressure (Δes), the land surface resistance (rs), and a derived aridity index by coupling a simple prognostic model (based on the complementary relationship) to evapotranspiration (E) estimates provided by the triangle/trapezoidal method (Jiang & Islam, 1999). This method requires a combination of remotely sensed data and few ground measurements, and is based on the use of the ratio E to potential evaporation (Ep) to derive the surface humidity prevailing at a given pixel. The method was applied to four sites in Western Africa, and the study of the temporal evolution of Δes and rs showed seasonal variations which are consistent with the wet and dry seasons that characterises the climate at these sites. We then propose a new dryness index, the surface aridity index (SAI) derived from the Δes - rs space, which proved to be a useful tool to assess the aridity state over a region.

  18. Assessing Atmospheric Water Injection from Oceanic Impacts

    NASA Technical Reports Server (NTRS)

    Pierazzo, E.

    2005-01-01

    Collisions of asteroids and comets with the Earth s surface are rare events that punctuate the geologic record. Due to the vastness of Earth s oceans, oceanic impacts of asteroids or comets are expected to be about 4 times more frequent than land impacts. The resulting injections of oceanic water into the upper atmosphere can have important repercussions on Earth s climate and atmospheric circulation. However, the duration and overall effect of these large injections are still unconstrained. This work addresses atmospheric injections of large amounts of water in oceanic impacts.

  19. Atmospheric radiation model for water surfaces

    NASA Technical Reports Server (NTRS)

    Turner, R. E.; Gaskill, D. W.; Lierzer, J. R.

    1982-01-01

    An atmospheric correction model was extended to account for various atmospheric radiation components in remotely sensed data. Components such as the atmospheric path radiance which results from singly scattered sky radiation specularly reflected by the water surface are considered. A component which is referred to as the virtual Sun path radiance, i.e. the singly scattered path radiance which results from the solar radiation which is specularly reflected by the water surface is also considered. These atmospheric radiation components are coded into a computer program for the analysis of multispectral remote sensor data over the Great Lakes of the United States. The user must know certain parameters, such as the visibility or spectral optical thickness of the atmosphere and the geometry of the sensor with respect to the Sun and the target elements under investigation.

  20. INTRODUCTION: Anticipated changes in the global atmospheric water cycle

    NASA Astrophysics Data System (ADS)

    Allan, Richard P.; Liepert, Beate G.

    2010-06-01

    The atmospheric branch of the water cycle, although containing just a tiny fraction of the Earth's total water reserves, presents a crucial interface between the physical climate (such as large-scale rainfall patterns) and the ecosystems upon which human societies ultimately depend. Because of the central importance of water in the Earth system, the question of how the water cycle is changing, and how it may alter in future as a result of anthropogenic changes, present one of the greatest challenges of this century. The recent Intergovernmental Panel on Climate Change report on Climate Change and Water (Bates et al 2008) highlighted the increasingly strong evidence of change in the global water cycle and associated environmental consequences. It is of critical importance to climate prediction and adaptation strategies that key processes in the atmospheric water cycle are precisely understood and determined, from evaporation at the surface of the ocean, transport by the atmosphere, condensation as cloud and eventual precipitation, and run-off through rivers following interaction with the land surface, sub-surface, ice, snow and vegetation. The purpose of this special focus issue of Environmental Research Letters on anticipated changes in the global atmospheric water cycle is to consolidate the recent substantial advances in understanding past, present and future changes in the global water cycle through evidence built upon theoretical understanding, backed up by observations and borne out by climate model simulations. Thermodynamic rises in water vapour provide a central constraint, as discussed in a guest editorial by Bengtsson (2010). Theoretical implications of the Clausius-Clapeyron equation are presented by O'Gorman and Muller (2010) and with reference to a simple model (Sherwood 2010) while observed humidity changes confirm these anticipated responses at the land and ocean surface (Willett et al 2008). Rises in low-level moisture are thought to fuel an

  1. Perspective: Water cluster mediated atmospheric chemistry

    SciTech Connect

    Vaida, Veronica

    2011-07-14

    The importance of water in atmospheric and environmental chemistry initiated recent studies with results documenting catalysis, suppression and anti-catalysis of thermal and photochemical reactions due to hydrogen bonding of reagents with water. Water, even one water molecule in binary complexes, has been shown by quantum chemistry to stabilize the transition state and lower its energy. However, new results underscore the need to evaluate the relative competing rates between reaction and dissipation to elucidate the role of water in chemistry. Water clusters have been used successfully as models for reactions in gas-phase, in aqueous condensed phases and at aqueous surfaces. Opportunities for experimental and theoretical chemical physics to make fundamental new discoveries abound. Work in this field is timely given the importance of water in atmospheric and environmental chemistry.

  2. Water vapour absorption in the penicillate millipede Polyxenus lagurus (Diplopoda: Penicillata: Polyxenida): microcalorimetric analysis of uptake kinetics.

    PubMed

    Wright, Jonathan C; Westh, Peter

    2006-07-01

    The aberrant millipedes of the order Polyxenida are minute animals that inhabit xeric microclimates of bark and rock faces. The lichens and algae that provide their main food substrates tolerate extensive dehydration, effectively eliminating a liquid water source during periods of drought. In this study, we used microcalorimetry to test whether Polyxenus lagurus (L.) exploits active water vapour absorption (WVA) for water replenishment. Individual animals were pre-desiccated to 10-20% mass-loss and heat fluxes then monitored using a TAM 2277 microcalorimeter. The calorimetric cell was exposed to an air stream increasing progressively in humidity from 84% to 96%. WVA was distinguishable as large exothermic fluxes seen in > or = 86% RH. Owing to very small and opposing heat fluxes from metabolism and passive water loss, the measured flux provided a good measure of water uptake. WVA showed an uptake threshold of 85% RH and linear sorption kinetics until >94% RH, when uptake became asymptotic. Uptake was rapid, and would allow recovery from 20% dehydration (by mass) in little over 5 h. The uptake flux scales proportional, variant mass (0.61), suggesting an area-limited mechanism. Polyxenus possesses a cryptonephric system, analogous to that of tenebrionid beetle larvae. Measurements of water absorption and desorption from faecal pellets voided in different humidities gave an estimated rectal humidity of 85.5%. The close congruence between this value and the WVA threshold provides evidence for a cryptonephric uptake mechanism derived independently from that of tenebrionids. Polyxenus represents the first documented example of WVA in the myriapod classes. PMID:16788032

  3. The effect of water vapour on the normalized difference vegetation index derived for the Sahelian region from NOAA AVHRR data

    NASA Technical Reports Server (NTRS)

    Justice, Christopher O.; Eck, T. F.; Tanre, Didier; Holben, B. N.

    1991-01-01

    The near-infrared channel of the NOAA advanced very high resolution radiometer (AVHRR) contains a water vapor absorption band that affects the determination of the normalized difference vegetation index (NDVI). Daily and seasonal variations in atmospheric water vapor within the Sahel are shown to affect the use of the NDVI for the estimation of primary production. This water vapor effect is quantified for the Sahel by radiative transfer modeling and empirically using observations made in Mali in 1986.

  4. Accuracy assessment of water vapour measurements from in-situ and remote sensing techniques during the DEMEVAP 2011 campaign

    NASA Astrophysics Data System (ADS)

    BOCK, Olivier; Bosser, Pierre; David, Leslie; Thom, Christian; Pelon, Jacques; Hoareau, Christophe; Keckhut, Philippe; Sarkissian, Alain; Pazmino, Andrea; Goutail, Florence; Legain, Dominique; Tzanos, Diane; Bourcy, Thomas; Poujol, Guillaume; Tournois, Guy

    2014-05-01

    The Development of Methodologies for Water Vapour Measurement (DEMEVAP) project aims at assessing and improving humidity sounding techniques and establishing a reference system based on the combination of Raman lidars, ground-based sensors and GPS. Such a system may be used for climate monitoring, radiosonde bias detection and correction, satellite measurement calibration/validation, and mm-level geodetic positioning with Global Navigation Satellite Systems. A field experiment was conducted in September-October 2011 at Observatoire de Haute Provence (OHP). Two Raman lidars (IGN mobile lidar and OHP NDACC lidar), a stellar spectrometer (SOPHIE), a differential absorption spectrometer (SAOZ), a sun photometer (AERONET), 5 GPS receivers and 4 types of radiosondes (Vaisala RS92, MODEM M2K2-DC and M10, and Meteolabor Snow-White) participated in the campaign. A total of 26 balloons with multiple radiosondes were flown during 16 clear nights. This paper presents preliminary findings from the analysis of all these datasets. Several classical Raman lidar calibration methods are evaluated which use either Vaisala RS92 measurements, point capacitive humidity measurements, or GPS integrated water vapour (IWV) measurements. A novel method proposed by Bosser et al. (2010) is also tested. It consists in calibrating the lidar measurements during the GPS data processing. The methods achieve a repeatability of 4-5 %. Changes in calibration factor of IGN Raman lidar are evidenced which are attributed to frequent optical re-alignments. When modelling and correcting the changes as a linear function of time, the precision of the calibration factors improves to 2-3 %. However, the variations in the calibration factor, and hence the absolute accuracy, between methods and types of reference data remain at the level of 7 %. The intercomparison of radiosonde measurements shows good agreement between RS92 and Snow-White measurements up to 12 km. An overall dry bias is found in the

  5. Accuracy assessment of water vapour measurements from in situ and remote sensing techniques during the DEMEVAP 2011 campaign at OHP

    NASA Astrophysics Data System (ADS)

    Bock, O.; Bosser, P.; Bourcy, T.; David, L.; Goutail, F.; Hoareau, C.; Keckhut, P.; Legain, D.; Pazmino, A.; Pelon, J.; Pipis, K.; Poujol, G.; Sarkissian, A.; Thom, C.; Tournois, G.; Tzanos, D.

    2013-10-01

    The Development of Methodologies for Water Vapour Measurement (DEMEVAP) project aims at assessing and improving humidity sounding techniques and establishing a reference system based on the combination of Raman lidars, ground-based sensors and GPS. Such a system may be used for climate monitoring, radiosonde bias detection and correction, satellite measurement calibration/validation, and mm-level geodetic positioning with Global Navigation Satellite Systems. A field experiment was conducted in September-October 2011 at Observatoire de Haute-Provence (OHP). Two Raman lidars (IGN mobile lidar and OHP NDACC lidar), a stellar spectrometer (SOPHIE), a differential absorption spectrometer (SAOZ), a sun photometer (AERONET), 5 GPS receivers and 4 types of radiosondes (Vaisala RS92, MODEM M2K2-DC and M10, and Meteolabor Snow White) participated in the campaign. A total of 26 balloons with multiple radiosondes were flown during 16 clear nights. This paper presents preliminary findings from the analysis of all these data sets. Several classical Raman lidar calibration methods are evaluated which use either Vaisala RS92 measurements, point capacitive humidity measurements, or GPS integrated water vapour (IWV) measurements. A novel method proposed by Bosser et al. (2010) is also tested. It consists in calibrating the lidar measurements during the GPS data processing. The methods achieve a repeatability of 4-5%. Changes in the calibration factor of IGN Raman lidar are evidenced which are attributed to frequent optical re-alignments. When modelling and correcting the changes as a linear function of time, the precision of the calibration factors improves to 2-3%. However, the variations in the calibration factor, and hence the absolute accuracy, between methods and types of reference data remain at the level of 7%. The intercomparison of radiosonde measurements shows good agreement between RS92 and Snow White measurements up to 12 km. An overall dry bias is found in the

  6. Vapour pressures and hygroscopicity of semi-volatile organic components in ternary organic/inorganic/water aerosol droplet trapped by aerosol optical tweezers

    NASA Astrophysics Data System (ADS)

    Cai, Chen; Zhang, Yunhong

    2016-04-01

    Knowledge of the vapour pressures of semi-volatile organic compounds is of critical importance in determining their partitioning behaviour into atmospheric aerosol. Quantifying the gas/particle partitioning of organic compounds is of great importance since at present published results of the vapour pressures of compounds of interest (typically with vapour pressures lower than 0.01 Pa) can be different by several orders of magnitude and influences on SVOCs evaporation from participation of inorganic compounds remains unclear. In this study we present a new method for the retrieval of SVOCs vapour pressures from single aerosol droplets in an aerosol optical tweezers system. Measurements of the concentration of SVOC (derived from experimentally determined RI) and radius of SVOC aqueous droplets are correlated in an expression derived from the Maxwell gas phase diffusion equation for the determination of vapour pressure. ( ) dmi-= 4π dr3Conc + dConcir3 = 4πrMiDi,gas-(p ‑ p) dt 3 dt i dt RT i,∞ i,r Relationship between r dr/dt (nm2s‑1) and r2dConcentration/dt (nm2gL‑1s‑1) is presented, in which the slope is derived for determination of hygroscopic line whilst the axis intercept can be determined to estimate vapour pressure. Briefly the method relies on the levitation of a droplet (3-7 μm radius) in an aerosol optical tweezers system. In this system the droplet acts as a microcavity and the size and refractive index of the particle can be extracted by using Mie theory to fit the positions of the "whispering gallery modes" in the cavity enhanced Raman spectroscopy fingerprint. The vapour pressure can then be extracted from the correlation between the rate of change of particle radius with the rate of change of composition (refractive index, n). We will show that information about the hygroscopicity of the particle and how this changes as the particle evaporates can also be determined from the changing slopes of these plots.

  7. Comparisons of xylem sap flow and water vapour flux at the stand level and derivation of canopy conductance for Scots pine

    NASA Astrophysics Data System (ADS)

    Granier, A.; Biron, P.; Köstner, B.; Gay, L. W.; Najjar, G.

    1996-03-01

    Simultaneous measurements of xylem sap flow and water vapour flux over a Scots pine ( Pinus sylvestris) forest (Hartheim, Germany), were carried out during the Hartheim Experiment (HartX), an intensive observation campaign of the international programme REKLIP. Sap flow was measured every 30 min using both radial constant heating (Granier, 1985) and two types of Cermak sap flowmeters installed on 24 trees selected to cover a wide range of the diameter classes of the stand (min 8 cm; max 17.5 cm). Available energy was high during the observation period (5.5 to 6.9 mm.day-1), and daily cumulated sap flow on a ground area basis varied between 2.0 and 2.7 mm day-1 depending on climate conditions. Maximum hourly values of sap flow reached 0.33 mm h-1, i.e., 230 W m-2. Comparisons of sap flow with water vapour flux as measured with two OPEC (One Propeller Eddy Correlation, University of Arizona) systems showed a time lag between the two methods, sap flow lagging about 90 min behind vapour flux. After taking into account this time lag in the sap flow data set, a good agreement was found between both methods: sap flow = 0.745* vapour flux, r 2 = 0.86. The difference between the two estimates was due to understory transpiration. Canopy conductance ( g c ) was calculated from sap flow measurements using the reverse form of Penman-Monteith equation and climatic data measured 4 m above the canopy. Variations of g c were well correlated ( r 2 = 0.85) with global radiation ( R) and vapour pressure deficit ( vpd). The quantitative expression for g c = f ( R, vpd) was very similar to that previously found with maritime pine ( Pinus pinaster) in the forest of Les Landes, South Western France.

  8. Water, vapour and heat transport in concrete cells for storing radioactive waste

    NASA Astrophysics Data System (ADS)

    Carme Chaparro, M.; Saaltink, Maarten W.

    2016-08-01

    Water is collected from a drain situated at the centre of a concrete cell that stores radioactive waste at 'El Cabril', which is the low and intermediate level radioactive waste disposal facility of Spain. This indicates flow of water within the cell. 2D numerical models have been made in order to reproduce and understand the processes that take place inside the cell. Temperature and relative humidity measured by sensors in the cells and thermo-hydraulic parameters from laboratory test have been used. Results show that this phenomenon is caused by capillary rise from the phreatic level, evaporation and condensation within the cell produced by temperature gradients caused by seasonal temperature fluctuations outside. At the centre of the cell, flow of gas and convection also play a role. Three remedial actions have been studied that may avoid the leakage of water from the drain.

  9. Molecular dynamics simulation of vapour-liquid nucleation of water with constant energy

    NASA Astrophysics Data System (ADS)

    Duška, Michal; Němec, Tomáš; Hrubý, Jan; Vinš, Václav; Planková, Barbora

    2015-05-01

    The paper describes molecular dynamics study of nucleation of water in NVE ensemble. The numerical simulation was performed with the DL_POLY. The metastable steam consisting of 10976 water molecules with TIP4P/2005 potential was driven on the desired energy level by a simulation at constant temperature, and then the nucleation at constant energy was studied for several tens of nanoseconds, which was sufficient for clusters to evolve at hundred molecules size. The results were compared with the previously published results and the classical nucleation theory predictions.

  10. Era-40 Water Vapour and Ozone Fields Compared With Measurements From The Mozaic Programme

    NASA Astrophysics Data System (ADS)

    Oikonomou, E. K.; O'Neil, A.

    The atmosphere of Mercury is eroded quickly by photoionization and electron impact ionization. Resulting ions are affected by both magnetic and electric field forces due to their small energy. The escape flux of these ions from Mercury's magnetosphere is believed to respond to the degree of solar wind - Hermean magnetosphere interaction. We present the structure of the Hermean magnetosphere obtained by the Toffoletto- Hill (JGR 98, 1339, 1993) model of an open magnetosphere, and supplement it with the Ding et al. (Phys. Space Plasmas, 1996) potential solver to represent the convection electric field. We calculate the fractional escape rate of sodium, potassium and argon ions as a function of the interplanetary magnetic field (IMF) direction and magnitude.

  11. A water-vapour giga-maser in the active galaxy TXFS2226-184.

    PubMed

    Koekemoer, A M; Henkel, C; Greenhill, L J; Dey, A; van Breugel, W; Codella, C; Antonucci, R

    1995-12-14

    Active galactic nuclei are thought to be powered by gas falling into a massive black hole; the different types of active galaxy may arise because we view them through a thick torus of molecular gas at varying angles of inclination. One way to determine whether the black hole is surrounded by a torus, which would obscure the accretion disk around the black hole along certain lines of sight, is to search for water masers, as these exist only in regions with plentiful molecular gas. Since the first detection of an extra-galactic water maser in 1979, they have come to be associated primarily with active galaxies, and have even been used to probe the mass of the central engine. Here we report the detection of a water giga-maser in the radio galaxy TXFS2226-184. The strength of the emission supports a recently proposed theory of maser pumping that allows for even more powerful masers, which might be detectable at cosmological distances. Water masers may accordingly provide a way to determine distances to galaxies outside the usual distance ladder, providing an independent calibration of the Hubble constant. PMID:7501016

  12. Balloon-borne cryogenic frost-point hygrometer observations of water vapour in the tropical upper troposphere and lower stratosphere over India: First results

    NASA Astrophysics Data System (ADS)

    Sunilkumar, S. V.; Muhsin, M.; Emmanuel, Maria; Ramkumar, Geetha; Rajeev, K.; Sijikumar, S.

    2016-03-01

    Balloon-borne cryogenic frost-point hygrometer (CFH) observations of water vapour in the upper troposphere and lower stratosphere (UTLS) region carried out over India, from Trivandrum [8.5°N, 76.9°E] and Hyderabad [17.5°N, 78.6°E], were compared with that obtained from quasi-collocated Aura-Microwave Limb Sounder (MLS) satellite observations. Comparisons show a small dry bias for MLS in the stratosphere. Saturated or super-saturation layers observed near the base of tropical tropopause layer (TTL) are consistent with the quasi-collocated space-based observations of tropical cirrus from KALPANA-1 and CALIPSO. Disturbance of large scale waves in the upper troposphere appears to modulate the water vapour and cirrus distribution.

  13. Rapid nanosheets and nanowires formation by thermal oxidation of iron in water vapour and their applications as Cr(VI) adsorbent

    NASA Astrophysics Data System (ADS)

    Budiman, Faisal; Bashirom, Nurulhuda; Tan, Wai Kian; Razak, Khairunisak Abdul; Matsuda, Atsunori; Lockman, Zainovia

    2016-09-01

    Thermal oxidation of iron foil was done at 400 °C and 500 °C in for 2 h to form multilayered oxide scale with outer oxide layer of α-Fe2O3 comprising of nanowires and nanosheets respectively. Iron oxidized at 300 °C formed a rather compact film with no noticeable nanostructures. The morphologies of oxide formed in different oxidation environment (water vapour or dry air) were compared; densely packed nanostructures were produced in water vapour compared to dry air. Time variation study indicated rapid growth of nanostructure whereby for 1 min at 500 °C dense nanowires with some noticeable nanosheets were already observed. The nanowires and nanosheets were used to adsorb Cr(VI) from aqueous solution. Adsorption of 10 ppm of Cr(VI) on the nanowires and nanosheets was found to be successful with much faster removal efficiency for the nanosheets. Both samples displayed complete adsorption for less than 1 h.

  14. G305.8 - 0.2 water vapour source: A young object

    NASA Astrophysics Data System (ADS)

    Vilas-Boas, J. W. S.; Scalise, E., Jr.; Sanzovo, C. G.

    1991-09-01

    Observations of water vapor and silicon monoxide masers were conducted in the direction of G305.8-0.2. No SiO maser emission above 7 Jy of flux density was detected. The short-time variability of the H20 maser together with the absence of compact radio continuum emission suggests that the excitation energy of the maser could originate from an O7-O9 protostar in its earlier evolutionary stages.

  15. Springtime stratospheric water vapour in the Southern Hemisphere as measured by MLS. [Microwave Limb Sounder

    NASA Technical Reports Server (NTRS)

    Harwood, R. S.; Carr, E. S.; Froidevaux, L.; Jarnot, R. F.; Lahoz, W. A.; Lau, C. L.; Peckham, G. E.; Read, W. G.; Ricaud, P. D.; Suttie, R. A.

    1993-01-01

    The effects of the break-up of the Antarctic vortex on the water vapor distribution are studied using MLS measurements of water vapor made during September 1991 and November 1991. In early November at 22 hPa a moist area is found within the polar vortex, consistent with an observed descent of order 10 km and strong radiative cooling. As the vortex erodes (beginning of November 1991), parcels of moist air become detached from the edge of the vortex and mix rapidly (within 2-3 days) with drier mid-latitude air. When the vortex breaks up (mid-November), larger parcels of moist air from both the edge and the inner vortex migrate to mid-latitudes. These parcels have a longer lifetime than those produced by vortex erosion, probably because they are correlated with higher potential vorticity gradients. The break-up of the vortex is accompanied by a mean adiabatic equatorward transport resulting in a significant increase in midstratospheric water vapor values at mid-latitudes in late spring.

  16. Assessment of adequate quality and collocation of reference measurements with space-borne hyperspectral infrared instruments to validate retrievals of temperature and water vapour

    NASA Astrophysics Data System (ADS)

    Calbet, X.

    2016-01-01

    A method is presented to assess whether a given reference ground-based point observation, typically a radiosonde measurement, is adequately collocated and sufficiently representative of space-borne hyperspectral infrared instrument measurements. Once this assessment is made, the ground-based data can be used to validate and potentially calibrate, with a high degree of accuracy, the hyperspectral retrievals of temperature and water vapour.

  17. Study of transport of oxygen and water vapour between cells in valve regulated lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Culpin, Barry; Peters, Ken

    Valve-regulated lead-acid batteries are maintenance free, safer, office compatible, and have higher volume efficiency than conventional designs. They are universally used in telecommunications and uninterruptible power supply systems. With the electrolyte immobilized in the separator or as a gel, it is feasible for a monobloc battery to have cells that are not fully sealed from one another, that is to have a common gas space, with certain attendant benefits. This study demonstrates that small differences in the saturation level, acid strength or operating temperature of the cells in such designs can initiate a cycle that may subsequently result in failure if the movement of oxygen and water vapour between cells is unrestricted. Cells that are initially out-of-balance will go further out-of-balance at an ever-increasing rate. This situation can also arise in monobloc designs with sealed cells if the intercell seal is inadequate or incomplete. Battery failure is associated with a re-distribution of water between the cells with some drying out and having high impedance. The preferential oxygen absorption in those cells produces heavily sulfated negative plates. Results on batteries tested under a range of overcharge conditions and temperatures are presented to illustrate these effects. The rate at which the cycle occurs depends on the initial relative density of the acid, the temperature or saturation imbalance between the cells, and the size of the interconnecting gas space. Batteries operating under a continuous cycling regime, particularly those with high overcharge currents and voltages that generate large volumes of oxygen, are more prone to this type of failure mode than batteries operating under low overcharge, intermittent cycling, or float conditions.

  18. Derivation of water vapour absorption cross-sections in the red region

    NASA Technical Reports Server (NTRS)

    Lal, M.; Chakrabarty, D. K.

    1994-01-01

    Absorption spectrum in 436 to 448 nm wavelength region gives NO2 and O3 column densities. This spectrum can also give H2O column density. The spectrum in the range of 655 to 667 nm contains absorption due to NO3 and H2O. Combining the absorption spectra in the wavelength ranges of 436 to 448 and 655 to 667 nm, water vapor absorption cross-sections in this range comes out to be of the order of 2.0 x 10(exp -24) cm(exp -2).

  19. Uranium metal reactions with hydrogen and water vapour and the reactivity of the uranium hydride produced

    SciTech Connect

    Godfrey, H.; Broan, C.; Goddard, D.; Hodge, N.; Woodhouse, G.; Diggle, A.; Orr, R.

    2013-07-01

    Within the nuclear industry, metallic uranium has been used as a fuel. If this metal is stored in a hydrogen rich environment then the uranium metal can react with the hydrogen to form uranium hydride which can be pyrophoric when exposed to air. The UK National Nuclear Laboratory has been carrying out a programme of research for Sellafield Limited to investigate the conditions required for the formation and persistence of uranium hydride and the reactivity of the material formed. The experimental results presented here have described new results characterising uranium hydride formed from bulk uranium at 50 and 160 C. degrees and measurements of the hydrolysis kinetics of these materials in liquid water. It has been shown that there is an increase in the proportion of alpha-uranium hydride in material formed at lower temperatures and that there is an increase in the rate of reaction with water of uranium hydride formed at lower temperatures. This may at least in part be attributable to a difference in the reaction rate between alpha and beta-uranium hydride. A striking observation is the strong dependence of the hydrolysis reaction rate on the temperature of preparation of the uranium hydride. For example, the reaction rate of uranium hydride prepared at 50 C. degrees was over ten times higher than that prepared at 160 C. degrees at 20% extent of reaction. The decrease in reaction rate with the extent of reaction also depended on the temperature of uranium hydride preparation.

  20. Validation of Aura MLS retrievals of temperature, water vapour and ozone in the upper troposphere and lower-middle stratosphere over the Tibetan Plateau during boreal summer

    NASA Astrophysics Data System (ADS)

    Yan, Xiaolu; Wright, Jonathon S.; Zheng, Xiangdong; Livesey, Nathaniel J.; Vömel, Holger; Zhou, Xiuji

    2016-08-01

    We validate Aura Microwave Limb Sounder (MLS) version 3 (v3) and version 4 (v4) retrievals of summertime temperature, water vapour and ozone in the upper troposphere and lower-middle stratosphere (UTLS; 10-316 hPa) against balloon soundings collected during the Study of Ozone, Aerosols and Radiation over the Tibetan Plateau (SOAR-TP). Mean v3 and v4 profiles of temperature, water vapour and ozone in this region during the measurement campaigns are almost identical through most of the stratosphere (10-68 hPa), but differ in several respects in the upper troposphere and tropopause layer. Differences in v4 relative to v3 include slightly colder mean temperatures from 100 to 316 hPa, smaller mean water vapour mixing ratios in the upper troposphere (215-316 hPa) and a more vertically homogeneous profile of mean ozone mixing ratios below the climatological tropopause (100-316 hPa). These changes substantially improve agreement between ozonesondes and MLS ozone retrievals in the upper troposphere, but slightly worsen existing cold and dry biases at these levels. Aura MLS temperature profiles contain significant cold biases relative to collocated temperature measurements in several layers of the lower-middle stratosphere and in the upper troposphere. MLS retrievals of water vapour volume mixing ratio generally compare well with collocated measurements, excepting a substantial dry bias (-32 ± 11 % in v4) that extends through most of the upper troposphere (121-261 hPa). MLS retrievals of ozone volume mixing ratio are biased high relative to collocated ozonesondes in the stratosphere (18-83 hPa), but are biased low at 100 hPa. The largest relative biases in ozone retrievals (approximately +70 %) are located at 83 hPa. MLS v4 offers substantial benefits relative to v3, particularly with respect to water vapour and ozone. Key improvements include larger data yields, reduced noise in the upper troposphere and smaller fluctuations in the bias profile at pressures larger than 100

  1. Estimation of precipitable water vapour using kinematic GNSS precise point positioning over an altitude range of 1 km

    NASA Astrophysics Data System (ADS)

    Webb, S. R.; Penna, N. T.; Clarke, P. J.; Webster, S.; Martin, I.

    2013-12-01

    The estimation of total precipitable water vapour (PWV) using kinematic GNSS has been investigated since around 2001, aiming to extend the use of static ground-based GNSS, from which PWV estimates are now operationally assimilated into numerical weather prediction models. To date, kinematic GNSS PWV studies suggest a PWV measurement agreement with radiosondes of 2-3 mm, almost commensurate with static GNSS measurement accuracy, but only shipborne experiments have so far been carried out. As a first step towards extending such sea level-based studies to platforms that operate at a range of altitudes, such as airplanes or land based vehicles, the kinematic GNSS estimation of PWV over an exactly repeated trajectory is considered. A data set was collected from a GNSS receiver and antenna mounted on a carriage of the Snowdon Mountain Railway, UK, which continually ascends and descends through 950 m of vertical relief. Static GNSS reference receivers were installed at the top and bottom of the altitude profile, and derived zenith wet delay (ZWD) was interpolated to the altitude of the train to provide reference values together with profile estimates from the 100 m resolution runs of the Met Office's Unified Model. We demonstrate similar GNSS accuracies as obtained from previous shipborne studies, namely a double difference relative kinematic GNSS ZWD accuracy within 14 mm, and a kinematic GNSS precise point positioning ZWD accuracy within 15 mm. The latter is a more typical airborne PWV estimation scenario i.e. without the reliance on ground-based GNSS reference stations. We show that the kinematic GPS-only precise point positioning ZWD estimation is enhanced by also incorporating GLONASS observations.

  2. Modified TEWL in vitro measurements on transdermal patches with different additives with regard to water vapour permeability kinetics.

    PubMed

    Fokuhl, Joana; Müller-Goymann, Christel C

    2013-02-28

    Water vapour permeability (WVP) and water absorption capacity (WAC) influence physicochemical properties and wearability of transdermal patches considerably. For determination of WVP, a modified transepidermal water loss (TEWL) measurement was developed. These measurements continuously measure WVP of transdermal patches in vitro along with time required to reach steady state, and its magnitude according to the type of polymer used. Additionally, WAC of the patches was examined and related to WVP. According to literature in the field of WVP determination, usually selected points are taken from the evaporation time curve and averaged over a given time span without knowing whether steady state has already been reached or not. The latter causes errors upon averaging. The advantage of the in vitro TEWL measurement presented includes reproducibly adjustable conditions for every time span desired, thus providing information on the kinetics of the experiment and avoiding biased results from averaging. Knowing the shape of the evaporation time curve and thus the kinetics of the experiment allows for focusing on the relevant part of the measurement, i.e. the determination of the steady state level and the time to reach it. Four different polymers (P1-P4) based on sugar-modified polyacrylates were investigated with regard to WVP and WAC of the matrices prepared thereof along with the influence of drug loading and the incorporation of a variety of additives commonly used for transdermal patches. A clear correlation between WVP and the hydrophilicity in terms of the number of free hydroxyl groups of the polymer was elaborated. Additives of higher hydrophilicity compared to that of the polymer itself led to higher WVPs and vice versa. The combination of the model drug lidocaine in its free base form together with the additive succinic acid (Suc) resulted in ionization of the drug and thus in substantially increased WVPs. Addition of α-tocopherol acetate (Toc) into P3 and P4 and

  3. Advanced Atmospheric Water Vapor DIAL Detection System

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Elsayed-Ali, Hani E.; DeYoung, Russell J. (Technical Monitor)

    2000-01-01

    Measurement of atmospheric water vapor is very important for understanding the Earth's climate and water cycle. The remote sensing Differential Absorption Lidar (DIAL) technique is a powerful method to perform such measurement from aircraft and space. This thesis describes a new advanced detection system, which incorporates major improvements regarding sensitivity and size. These improvements include a low noise advanced avalanche photodiode detector, a custom analog circuit, a 14-bit digitizer, a microcontroller for on board averaging and finally a fast computer interface. This thesis describes the design and validation of this new water vapor DIAL detection system which was integrated onto a small Printed Circuit Board (PCB) with minimal weight and power consumption. Comparing its measurements to an existing DIAL system for aerosol and water vapor profiling validated the detection system.

  4. Total column water vapour measurements from GOME-2 MetOp-A and MetOp-B

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Valks, P.; Loyola, D.; Aberle, B.; Slijkhuis, S.; Wagner, T.; Beirle, S.; Lang, R.

    2015-03-01

    Knowledge of the total column water vapour (TCWV) global distribution is fundamental for climate analysis and weather monitoring. In this work, we present the retrieval algorithm used to derive the operational TCWV from the GOME-2 sensors aboard EUMETSAT's MetOp-A and MetOp-B satellites and perform an extensive inter-comparison in order to evaluate their consistency and temporal stability. For the analysis, the GOME-2 data sets are generated by DLR in the framework of the EUMETSAT O3M-SAF project using the GOME Data Processor (GDP) version 4.7. The retrieval algorithm is based on a classical Differential Optical Absorption Spectroscopy (DOAS) method and combines a H2O and O2 retrieval for the computation of the trace gas vertical column density. We introduce a further enhancement in the quality of the H2O total column by optimizing the cloud screening and developing an empirical correction in order to eliminate the instrument scan angle dependencies. The overall consistency between measurements from the newer GOME-2 instrument on board of the MetOp-B platform and the GOME-2/MetOp-A data is evaluated in the overlap period (December 2012-June 2014). Furthermore, we compare GOME-2 results with independent TCWV data from the ECMWF ERA-Interim reanalysis, with SSMIS satellite measurements during the full period January 2007-June 2014 and against the combined SSM/I + MERIS satellite data set developed in the framework of the ESA DUE GlobVapour project (January 2007-December 2008). Global mean biases as small as ±0.035 g cm-2 are found between GOME-2A and all other data sets. The combined SSM/I-MERIS sample and the ECMWF ERA-Interim data set are typically drier than the GOME-2 retrievals, while on average GOME-2 data overestimate the SSMIS measurements by only 0.006 g cm-2. However, the size of these biases is seasonally dependent. Monthly average differences can be as large as 0.1 g cm-2, based on the analysis against SSMIS measurements, which include only data over

  5. Rate Constants for the Reactions of OH with CO, NO and NO2, and of HO2 with NO2 in the Presence of Water Vapour at Lower-Tropospheric Conditions

    NASA Astrophysics Data System (ADS)

    Rolletter, Michael; Fuchs, Hendrik; Novelli, Anna; Ehlers, Christian; Hofzumahaus, Andreas

    2016-04-01

    Recent studies have shown that the chemistry of gaseous nitrous acid (HONO) in the lower troposphere is not fully understood. Aside from heterogenous reactions, the daytime HONO formation in the gas-phase is not well understood (Li et al., Science, 2014). For a better understanding of HONO in the gas-phase, we have reinvestigated the reaction rate constants of important tropospheric reactions of the HOx radical family (OH and HO2) with nitrogen oxides at realistic conditions of the lower troposphere (at ambient temperature/pressure and in humid air). In this study we apply a direct pump and probe technique with high accuracy, using small radical concentrations to avoid secondary chemistry. Pulsed laser photolysis/laser-induced fluorescence (LP/LIF) was used to investigate the reaction rate constants of OH with CO, NO, NO2, and HO2 with NO2 in synthetic air at different water vapor concentrations (up to 5 x 1017 molecules cm‑3). Photolysis of ozone in the presence of gaseous water was the source of OH. The reactions took place in a flow-tube at room temperature and atmospheric pressure. The chemical decay of the radicals was monitored by laser-induced fluorescence detection in a low-pressure cell, which sampled air continuously from the end of the flow-tube. Knowing the reactant concentrations subsequently allowed to calculate the bimolecular reaction rate constants at 1 atm from the pseudo-first-order decays. In order to observe HO2 reactions, OH was converted into HO2 with an excess of CO in the flow-tube. The newly measured rate constants for OH with CO, NO and NO2 agree very well with current recommendations by NASA/JPL and IUPAC and have an improved accuracy (uncertainty < 5%). These rate coefficients are independent of the presence of water vapour. The measured rate constant of HO2 with NO2 was found to depend significantly on the water-vapour concentration (probably due to formation of HO2*H2O complexes) and to exceed current recommendations by NASA/JPL and

  6. A dilute Cu(Ni) alloy for synthesis of large-area Bernal stacked bilayer graphene using atmospheric pressure chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Madito, M. J.; Bello, A.; Dangbegnon, J. K.; Oliphant, C. J.; Jordaan, W. A.; Momodu, D. Y.; Masikhwa, T. M.; Barzegar, F.; Fabiane, M.; Manyala, N.

    2016-01-01

    A bilayer graphene film obtained on copper (Cu) foil is known to have a significant fraction of non-Bernal (AB) stacking and on copper/nickel (Cu/Ni) thin films is known to grow over a large-area with AB stacking. In this study, annealed Cu foils for graphene growth were doped with small concentrations of Ni to obtain dilute Cu(Ni) alloys in which the hydrocarbon decomposition rate of Cu will be enhanced by Ni during synthesis of large-area AB-stacked bilayer graphene using atmospheric pressure chemical vapour deposition. The Ni doped concentration and the Ni homogeneous distribution in Cu foil were confirmed with inductively coupled plasma optical emission spectrometry and proton-induced X-ray emission. An electron backscatter diffraction map showed that Cu foils have a single (001) surface orientation which leads to a uniform growth rate on Cu surface in early stages of graphene growth and also leads to a uniform Ni surface concentration distribution through segregation kinetics. The increase in Ni surface concentration in foils was investigated with time-of-flight secondary ion mass spectrometry. The quality of graphene, the number of graphene layers, and the layers stacking order in synthesized bilayer graphene films were confirmed by Raman and electron diffraction measurements. A four point probe station was used to measure the sheet resistance of graphene films. As compared to Cu foil, the prepared dilute Cu(Ni) alloy demonstrated the good capability of growing large-area AB-stacked bilayer graphene film by increasing Ni content in Cu surface layer.

  7. Low-cost and easy experiments about water in the atmosphere

    NASA Astrophysics Data System (ADS)

    Costa, M.; Mazon, J.

    2012-04-01

    Atmospheric water represents only the 0,001% of the total water in the hydrosphere. Despite this tiny percentage, the physical changes water experiences in the atmosphere are essential for the conservation of this substance in our planet. Often, the understanding of the presence of water in the Earth's atmosphere and its physical changes inside this gas layer are difficult for most secondary and primary school students. We present 5 examples of simple practical activities that will facilitate students to think about and understand some important concepts about atmospheric water. Two of the basic principles to bear in mind when designing these activities are the use of cheap and easy to find materials and the simplicity of the construction and development of each activity. This simplicity makes it possible for the students to easily carry the experiments in the classroom or in the laboratory, using only a part of a class session. We think that the use of these kinds of activities enables us to work some basic concepts about atmospheric water with the students which lead to a more meaningful understanding, not only of these concepts but also of many other processes related to this part of the hydrosphere, such as meteorological phenomena, erosion, floods, etc. Here we present a brief description of the five experiments we suggest: 1- a crazy thermometer? Using water at the same temperature of the air, a piece of paper and two thermometers, we can easily "build" a dry and a wet bulb thermometer. Making questions about the differences between the temperatures of both thermometers we can understand what the air's humidity is and how we can calculate it. 2- what are clouds made of? Most of people think that clouds are made of water vapour. Observing what happens with the air above a small container filled with warm water when we approach a tray containing ice, we can conduct a Socratic dialogue that allows us to understand that clouds are made of ice or liquid water

  8. Ferric ion induced enhancement of ultraviolet vapour generation coupled with atomic fluorescence spectrometry for the determination of ultratrace inorganic arsenic in surface water.

    PubMed

    Wang, Yuelong; Lin, Lingling; Liu, Jixin; Mao, Xuefei; Wang, Jianhua; Qin, Deyuan

    2016-02-21

    A novel method of ultraviolet vapour generation (UVG) coupled with atomic fluorescence spectrometry (AFS) was developed for the determination of ultratrace inorganic arsenic (iAs) in surface water. In this work, different ferric species were utilised for the first time as an enhancement reagent for the ultraviolet vapour generation of As(III), and their UVG efficiencies for volatile species of arsenic were investigated. 15 mg L(-1) of ferric chloride provided the greatest enhancement of approximately 10-fold, using 20% acetic acid combined with 4% formic acid with 30 s ultraviolet irradiation at 200 mL min(-1) Ar/H2 flow rate. Under the optimised conditions, the linear range was 1.0 μg L(-1)-100.0 μg L(-1), and the spiked recoveries were 92%-98%. The limit of detection was 0.05 μg L(-1) for iAs, and the relative standard deviation (RSD) value of the repeated measurements was 2.0% (n = 11). This method was successfully applied to the determination of ultratrace iAs in tap water, river water, and lake water samples using 0.2% H2SO4 (v : v) as the sample preserver. The obtained values for the water samples of certified reference materials (CRMs) including GSB-Z50004-200431, GBW08605 and GBW(E)080390 were all within the certified ranges. PMID:26765360

  9. The importance of the poikilohydric nature of lichens as natural tracers for delta18O of ambient vapour

    NASA Astrophysics Data System (ADS)

    Hartard, Britta; Cuntz, Matthias; Lakatos, Michael; Máguas, Cristina

    2010-05-01

    The stable isotope composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in poikilohydric organisms (i.e. lichens and bryophytes), where relative water content equilibrate with the surrounding humidity conditions and that are able to use distinct water sources such as precipitation, dew, fog and also water vapour. Moreover, lichens are ubiquitous organisms, and on a global scale, they are found in nearly all terrestrial ecosystems and also within these ecosystems they inhabit many microhabitats. As poikilohydric. especially green algal lichens are known to photosynthetically reactivate solely upon uptake of atmospheric moisture, even at non-saturated ambient humidity conditions. To understand basic isotope exchange processes on non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrates with the isotopic composition of surrounding water vapour. We found that the thallus water of lichens exposed to high relative humidity shows fast isotopic equilibration with the surrounding vapour regardless of whether the lichen experiences water loss or vapour uptake. The time until isotopic equilibrium is achieved depends on the initial water status as well as on the lichen's specific morphology. It ranged from 5 to 12h in previously dried lichens to approximately 40h in lichens previously rehydrated with liquid water of distinct isotopic composition. Even though markedly slower, isotopic equilibration between leaf water and ambient vapour may also occur in homoiohydric plants exposed to high relative humidity. At low relative humidity, however, the apparent vapour pressure deficit between the evaporative sites and the ambient air and the increased stomatal diffusion resistance generally causes leaf water enrichment. In contrast, poikilohydric lichens lack

  10. Validation of GOME-2/MetOp-A total water vapour column using reference radiosonde data from the GRUAN network

    NASA Astrophysics Data System (ADS)

    Antón, M.; Loyola, D.; Román, R.; Vömel, H.

    2015-03-01

    The main goal of this paper is to validate the total water vapour column (TWVC) measured by the Global Ozone Monitoring Experiment-2 (GOME-2) satellite sensor and generated using the GOME Data Processor (GDP) retrieval algorithm developed by the German Aerospace Centre (DLR). For this purpose, spatially and temporally collocated TWVC data from highly accurate sounding measurements for the period January 2009-May 2014 at six sites are used. These balloon-borne data are provided by the GCOS Reference Upper-Air Network (GRUAN). The correlation between GOME-2 and sounding TWVC data is reasonably good (determination coefficient, R2, of 0.89) when all available radiosondes (1400) are employed in the inter-comparison. When cloud-free cases (544) are selected by means of the satellite cloud fraction (CF < 5%), the correlation exhibits a remarkable improvement (R2 ~ 0.95). Nevertheless, the analysis of the relative differences between GOME-2 and GRUAN data shows a mean absolute bias error (weighted with the combined uncertainty derived from the estimated errors of both data sets) of 15% for all-sky conditions (9% for cloud-free cases). These results evidence a notable bias in the satellite TWVC data against the reference balloon-borne measurements, partially related to the cloudy conditions during the satellite overpass. The detailed analysis of the influence of cloud properties - CF, cloud top albedo (CTA) and cloud top pressure (CTP) - on the satellite-sounding differences reveals, as expected, a large effect of clouds in the GOME-2 TWVC data. For instance, the relative differences exhibit a large negative dependence on CTA, varying from -6 to -23% when CTA rises from 0.3 to 0.8. Furthermore, the satellite-sounding TWVC differences show a strong dependence on the satellite solar zenith angle (SZA) for values above 50°. Hence the smallest relative differences found in this satellite-sounding comparison are achieved for those cloud-free cases with satellite SZA below 50

  11. Adding constraints by in situ informations to optimal estimation retrievals of tropospheric water vapour profiles from microwave radiometry

    NASA Astrophysics Data System (ADS)

    Bleisch, R.; Kämpfer, N.

    2012-11-01

    The optimal estimation method is a widely used method to invert species profiles from spectra observed by a microwave radiometer. The classical retrieval is constrained by the a priori profile and the corresponding covariance matrix, which is a “soft” constraining of the retrieved profile to a certain range of values. However, in some cases a “hard” constraining of the profile to a fixed value known from other measurements would be desirable.This work presents an approach to introduce such “hard” retrieval constraints (fixed-points) into optimal estimation retrievals by adapting the a priori covariance matrix.Its application is tested on the example of the retrieval of tropospheric water vapour volume mixing ratio (vmr) profiles from spectra of the MIAWARA radiometer operated by the Institute of Applied Physics, University of Bern. Thereby the cloud base height is one candidate to deliver a fixed-point, as the corresponding vmr value can be determined by assuming a relative humidity of 100%.As a test, the approach is applied to spectra simulated from balloon soundings. The cloud base height is derived from these same balloon soundings. The results show a significant improvement of the retrieval performance for all cases with liquid clouds except for fog.Afterwards the approach is also applied to real MIAWARA data. Thereby the measurements of a ceilometer and an infrared sensor (both installed close to the instrument) are used to derive a fixed-point.In principle, the application on real data also works. However the retrieval performance is limited, because we are currently not able to determine the vmr value at fixed-point altitude with suitable precision. The cloud base temperature, needed for the calculation of the vmr value at fixed-point altitude, is determined indirectly from measurements of an infrared sensor attached to the instruments or by for example interpolating data from ECMWF-reanalysis. In both cases the precision is not very high, with

  12. Validation of GOME-2/MetOp-A total water vapour column using reference radiosonde data from GRUAN network

    NASA Astrophysics Data System (ADS)

    Antón, M.; Loyola, D.; Román, R.; Vömel, H.

    2014-09-01

    The main goal of this article is to validate the total water vapour column (TWVC) measured by the Global Ozone Monitoring Experiment-2 (GOME-2) satellite sensor and generated using the GOME Data Processor (GDP) retrieval algorithm developed by the German Aerospace Center (DLR). For this purpose, spatially and temporally collocated TWVC data from highly accurate sounding measurements for the period January 2009-May 2014 at six sites are used. These balloon-borne data are provided by GCOS Reference Upper-Air Network (GRUAN). The correlation between GOME-2 and sounding TWVC data is reasonably good (determination coefficient (R2) of 0.89) when all available radiosondes (1400) are employed in the inter-comparison. When cloud-free cases (544) are selected by means of the satellite cloud fraction (CF), the correlation exhibits a remarkable improvement (R2 ~ 0.95). Nevertheless, analyzing the six datasets together, the relative differences between GOME-2 and GRUAN data shows mean values (in absolute term) of 19% for all-sky conditions and 14% for cloud-free cases, which evidences a notable bias in the satellite TWVC data against the reference balloon-borne measurements. The satellite-sounding TWVC differences show a strong solar zenith angle (SZA) dependence for values above 50° with a stable behaviour for values below this zenith angle. The smallest relative differences found in the inter-comparison (between -5 and +3%) are achieved for those cloud-free cases with SZA below 50°. Furthermore, the detailed analysis of the influence of cloud properties (CF, cloud top albedo (CTA) and cloud top pressure (CTP)) on the satellite-sounding differences reveals, as expected, a large effect of clouds in the GOME-2 TWVC data. For instance, the relative differences exhibit a large negative dependence on CTA, varying from +5 to -20% when CTA rises from 0.3 to 0.9. Finally, the satellite-sounding differences also show a negative dependence on the reference TWVC values, changing from

  13. Modeling of Revitalization of Atmospheric Water

    NASA Technical Reports Server (NTRS)

    Coker, Robert; Knox, Jim

    2014-01-01

    The Atmosphere Revitalization Recovery and Environmental Monitoring (ARREM) project was initiated in September of 2011 as part of the Advanced Exploration Systems (AES) program. Under the ARREM project, testing of sub-scale and full-scale systems has been combined with multiphysics computer simulations for evaluation and optimization of subsystem approaches. In particular, this paper describes the testing and modeling of the water desiccant subsystem of the carbon dioxide removal assembly (CDRA). The goal is a full system predictive model of CDRA to guide system optimization and development.

  14. Mercury vapour suppression by various liquid media.

    PubMed

    Sutow, E J; Foong, W C; Rizkalla, A S; Jones, D W; Power, N L

    1994-09-01

    Fresh and used photographic fixer, Merconvap and water were evaluated for their ability to suppress the vapourization of mercury. Mercury vapour concentration above the four test storage liquids was measured at various times between 10 min and 335 days, using a mercury vapour measuring instrument. The data were analysed using a Student-Newman-Keuls multiple comparison test (P = 0.05). The results showed that fresh and used fixer and Merconvap suppressed the vapourization of mercury to below the detection limit of the measuring instrument (0.01 mg/m3). Water was much less effective compared with the other liquids and showed an increase in mercury vapour concentration with log t. PMID:7996339

  15. Escape of atmospheres and loss of water

    NASA Technical Reports Server (NTRS)

    Hunten, D. M.; Donahue, T. M.; Walker, J. C. G.; Kasting, J. F.

    1989-01-01

    The properties and limitations of several loss processes for atmospheric gases are presented and discussed. They include thermal loss (Jeans and hydrodynamic); nonthermal loss (all processes involve charged particles); and impact erosion, including thermal escape from a molten body heated by rapid accretion. Hydrodynamic escape, or 'blowoff', is of particular interest because it offers the prospect of processing large quantities of gas and enriching the remainder in heavy elements and isotopes. In a second part, the water budgets and likely evolutionary histories of Venus, Earth and Mars are assessed. Although it is tempting to associate the great D/H enrichment on Venus with loss of a large initial endowment, a steady state with juvenile water (perhaps from comets) is equally probable.

  16. Water soluble heptakis(6-deoxy-6-thio)cyclomaltoheptaose capped gold nanoparticles via metal vapour synthesis: NMR structural characterization and complexation properties.

    PubMed

    Uccello-Barretta, Gloria; Evangelisti, Claudio; Balzano, Federica; Vanni, Letizia; Aiello, Federica; Jicsinszky, Laszlo

    2011-05-01

    The complexation of heptakis(6-deoxy-6-thio)cyclomaltoheptaose to gold nanoparticles prepared by using the Metal Vapour Synthesis (MVS) led to water soluble gold nanoaggregates, thermally stable at 25°C. The role of gold concentration in the MVS-derived starting solution as well as of the cyclodextrin to gold molar ratio on the size of cyclodextrin-capped gold nanoparticles were investigated. The ability of cyclodextrin bonded to gold nanoparticles to include deoxycytidine was also probed in comparison with that of 1-thio-β-D-glucose sodium salt. PMID:21367401

  17. Measurement of the absorption line profiles of water vapour isotopomers at 1.39 {mu}m using the methods of diode laser spectroscopy

    SciTech Connect

    Kuz'michev, A S; Nadezhdinskii, Aleksandr I; Ponurovskii, Ya Ya

    2011-07-31

    The issues related to high-precision measurement of the absorption line profiles of water vapour and its isotopomers using the methods of diode laser spectroscopy in the near IR range aimed at the analysis and detection of greenhouse gases are considered. The absorption line shape of H{sub 2}{sup 16}O is investigated as a function of pressure of different buffer gases. The influence of the instrument function of the diode laser (DL) on the precision of measuring the line profile is studied. From fitting the profile of Doppler-broadened H{sub 2}{sup 16}O absorption line to a model profile the lasing line width of the DL with a fibre pigtail is determined. The frequencies and intensities of absorption lines of water isotopomers H{sub 2}{sup 16}O, H{sub 2}{sup 17}O, H{sub 2}{sup 18}O, and HDO are measured in the range of DL oscillation. Analytical spectral regions are chosen for distant probing of water vapour using an airborne lab. (laser spectroscopy)

  18. Effect of densifying the GNSS GBAS network on monitoring the troposphere zenith total delay and precipitable water vapour content during severe weather events

    NASA Astrophysics Data System (ADS)

    Kapłon, Jan; Stankunavicius, Gintautas

    2016-04-01

    The dense ground based augmentation networks can provide the important information for monitoring the state of neutral atmosphere. The GNSS&METEO research group at Wroclaw University of Environmental and Life Sciences (WUELS) is operating the self-developed near real-time service estimating the troposphere parameters from GNSS data for the area of Poland. The service is operational since December 2012 and it's results calculated from ASG-EUPOS GBAS network (120 stations) data are supporting the EGVAP (http://egvap.dmi.dk) project. At first the zenith troposphere delays (ZTD) were calculated in hourly intervals, but since September 2015 the service was upgraded to include SmartNet GBAS network (Leica Geosystems Polska - 150 stations). The upgrade included as well: increasing the result interval to 30 minutes, upgrade from Bernese GPS Software v. 5.0 to Bernese GNSS Software v. 5.2 and estimation of the ZTD and it's horizontal gradients. Processing includes nowadays 270 stations. The densification of network from 70 km of mean distance between stations to 40 km created the opportunity to investigate on it's impact on resolution of estimated ZTD and integrated water vapour content (IWV) fields during the weather events of high intensity. Increase in density of ZTD measurements allows to define better the meso-scale features within different synoptic systems (e.g. frontal waves, meso-scale convective systems, squall lines etc). These meso-scale structures, as a rule are short living but fast developing and hardly predictable by numerical models. Even so, such limited size systems can produce very hazardous phenomena - like widespread squalls and thunderstorms, tornadoes, heavy rains, snowfalls, hail etc. because of prevalence of Cb clouds with high concentration of IWV. Study deals with two meteorological events: 2015-09-01 with the devastating squalls and rainfall bringing 2M Euro loss of property in northern Poland and 2015-10-12 with the very active front bringing

  19. Effects of ultraviolet irradiation, pulsed electric field, hot water dip and ethanol vapours treatment on keeping and sensory quality of mung bean (Vigna radiata L. Wilczek) sprouts.

    PubMed

    Goyal, Ankit; Siddiqui, Saleem

    2014-10-01

    The objective of this research work was to evaluate the effects of UV- irradiation, pulsed electric field (PEF), hot water dip (HWD) and ethanol vapours on the quality and storage life of mung bean sprouts (Vigna radiata L. Wilczek). The sprouts were subjected to various treatments viz., UV-Irradiation (10 kJm(-2) in laminar flow chamber for 1 h), PEF (10,000 V for 10s), HWD (50 °C for 2 min) and ethanol vapours (1 h); and then stored in thermocol cups wrapped with perforated cling films at room (25 ± 1 °C) and low (7 ± 1 °C) temperature conditions. The sprouts were analyzed regularly at 24 h interval for sprout length, sprout weight, total soluble solids (TSS), titratable acidity, non-enzymatic browning, total plate count and overall acceptability. Sprout length and weight increased during storage. There was no significant effect of various treatments on sprout length and weight, except in ethanol treatment, where suppression was observed. HWD showed higher TSS and acidity than that of control. The least browning was observed in ethanol treatment. The total plate count was not significantly affected by various treatments. Overall acceptability under various treatments decreased during storage period both at room and low temperature. Hot water and ethanol vapour treated sprouts showed higher acceptability than other treatments. However, the acceptability scores for sprouts remained within the acceptable range (≥6) up to 72 h at room temperature and 120 h at low temperature conditions. PMID:25328209

  20. Impact of water vapour and carbon dioxide on surface composition of C{sub 3}A polymorphs studied by X-ray photoelectron spectroscopy

    SciTech Connect

    Dubina, E.; Plank, J.; Black, L.

    2015-07-15

    The surface specific analytical method, X-ray photoelectron spectroscopy (XPS), has been used to study the effects of water vapour and CO{sub 2} on the cubic and orthorhombic polymorphs of C{sub 3}A. Significant differences between the two polymorphs were observed in the XPS spectra. Upon exposure to water vapour, both polymorphs produced C{sub 4}AH{sub 13} on their surfaces. Additionally, the sodium-doped o-C{sub 3}A developed NaOH and traces of C{sub 3}AH{sub 6} on its surface. Subsequent carbonation yielded mono carboaluminate on both polymorphs. Large amounts of Na{sub 2}CO{sub 3} also formed on the surface of o-C{sub 3}A as a result of carbonation of NaOH. Furthermore, the extent of carbonation was much more pronounced for o-C{sub 3}A{sub o} than for c-C{sub 3}A.

  1. Intensities and self-broadening coefficients of the strongest water vapour lines in the 2.7 and 6.25 μm absorption bands

    NASA Astrophysics Data System (ADS)

    Ptashnik, Igor V.; McPheat, Robert; Polyansky, Oleg L.; Shine, Keith P.; Smith, Kevin M.

    2016-07-01

    Intensities and self-broadening coefficients are presented for about 460 of the strongest water vapour lines in the spectral regions 1400-1840 cm-1 and 3440-3970 cm-1 at room temperature, obtained from rather unique measurements using a 5-mm-path-length cell. The retrieved spectral line parameters are compared with those in the HITRAN database ver. 2008 and 2012 and with recent ab-initio calculations. Both the retrieved intensities and half-widths are on average in reasonable agreement with those in HITRAN-2012. Maximum systematic differences do not exceed 4% for intensities (1600 cm-1 band) and 7% for self-broadening coefficients (3600 cm-1 band). For many lines however significant disagreements were detected with the HITRAN-2012 data, exceeding the average uncertainty of the retrieval. In addition, water vapour line parameters for 5300 cm-1 (1.9 μm) band reported by us in 2005 were also compared with HITRAN-2012, and show average differences of 4-5% for both intensities and half-widths.

  2. Impact of Pt additives on the surface reactions between SnO2, water vapour, CO and H2; an operando investigation.

    PubMed

    Großmann, Katharina; Wicker, Susanne; Weimar, Udo; Barsan, Nicolae

    2013-11-28

    The impact of Pt doping on the surface reactions between tin dioxide, water vapour, CO and H2 was investigated by a combination of simultaneously performed operando DRIFT (Diffuse Reflectance Infrared Fourier Transform) spectroscopy, DC resistance measurements and analysis of the reaction products by using a MS (Mass Spectrometer). Both undoped and Pt doped tin dioxide sensors were exposed to different test gases in synthetic air or in N2 backgrounds. The approach made it possible to identify the differences between the two materials with respect to their surface chemistry and their impact on the gas sensing performance. The main finding is that the presence of Pt changes the reaction partners' nature for water vapour and H2 on the one hand, and CO on the other hand when the sensors are operated in air. In this way the cross interference effect of humidity, which is responsible for the loss of CO sensing performance for the sensors based on undoped SnO2, is reversed. PMID:24105035

  3. Characterization of simultaneous heat and mass transfer phenomena for water vapour condensation on a solid surface in an abiotic environment--application to bioprocesses.

    PubMed

    Tiwari, Akhilesh; Kondjoyan, Alain; Fontaine, Jean-Pierre

    2012-07-01

    The phenomenon of heat and mass transfer by condensation of water vapour from humid air involves several key concepts in aerobic bioreactors. The high performance of bioreactors results from optimised interactions between biological processes and multiphase heat and mass transfer. Indeed in various processes such as submerged fermenters and solid-state fermenters, gas/liquid transfer need to be well controlled, as it is involved at the microorganism interface and for the control of the global process. For the theoretical prediction of such phenomena, mathematical models require heat and mass transfer coefficients. To date, very few data have been validated concerning mass transfer coefficients from humid air inflows relevant to those bioprocesses. Our study focussed on the condensation process of water vapour and developed an experimental set-up and protocol to study the velocity profiles and the mass flux on a small size horizontal flat plate in controlled environmental conditions. A closed circuit wind tunnel facility was used to control the temperature, hygrometry and hydrodynamics of the flow. The temperature of the active surface was controlled and kept isothermal below the dew point to induce condensation, by the use of thermoelectricity. The experiments were performed at ambient temperature for a relative humidity between 35-65% and for a velocity of 1.0 ms⁻¹. The obtained data are analysed and compared to available theoretical calculations on condensation mass flux. PMID:22367641

  4. Vapour pressures, aqueous solubility, Henry's law constants and air/water partition coefficients of 1,8-dichlorooctane and 1,8-dibromooctane.

    PubMed

    Sarraute, Sabine; Mokbel, Ilham; Costa Gomes, Margarida F; Majer, Vladimir; Delepine, Hervé; Jose, Jacques

    2006-09-01

    New data on the vapour pressures and aqueous solubility of 1,8-dichlorooctane and 1,8-dibromooctane are reported as a function of temperature between 20 degrees C and 80 degrees C and 1 degrees C and 40 degrees C, respectively. For the vapour pressures, a static method was used during the measurements which have an estimated uncertainty between 3% and 5%. The aqueous solubilities were determined using a dynamic saturation column method and the values are accurate to within +/-10%. 1,8-Dichlorooctane is more volatile than 1,8-dibromooctane in the temperature range covered (p(sat) varies from 3 to 250 Pa and from 0.53 to 62 Pa, respectively) and is also approximately three times more soluble in water (mole fraction solubilities at 25 degrees C of 5.95 x 10(-7) and 1.92 x 10(-7), respectively). A combination of the two sets of data allowed the calculation of the Henry's law constants and the air water partition coefficients. A simple group contribution concept was used to rationalize the data obtained. PMID:16530806

  5. Leaf Stomatal Responses to Vapour Pressure Deficit Under Current and CO2- Enriched Atmosphere Explained by the Economics of gas Exchange

    NASA Astrophysics Data System (ADS)

    Palmroth, S.; Katul, G. G.; Oren, R.

    2008-12-01

    Climate models predict that warming caused by increasing atmospheric greenhouse gases will not be accompanied with a change in atmospheric relative humidity (RH) but will cause an exponential increase in vapor pressure deficit (D). Predictions of water cycling in future climates are sensitive to the response of stomatal conductance (g) to all these changes. In currently used ecosystem models, the simulation of CO2 and water vapor exchange through stomata is typically based on empirical or semi-empirical stomatal responses to environmental stimuli. Depending on the formulation, stomata respond to either D or RH and, consequently, g predicted under future climate scenarios will greatly differ. In difference to the semi- empirical formulations of g, the tradeoffs between leaf-level carbon gain in photosynthesis and water loss in transpiration can be analyzed using the economics of gas exchange. First presented by Cowan (1977) and Cowan and Farquhar (1977; hereafter CF77) and reformulated by Berninger and Hari (1993; hereafter BH93), the cost (water loss) to benefit (carbon gain) analysis was framed as an economic optimization where the daily carbon gain is maximized for a given loss of water. While the assumptions on the form of the underlying functions differ between CF77 and BH93, we show that the optimal solutions can be made identical where the solution is independent of the time scale of flux integration. The stomatal control over gas exchange is described through a concept of invariant 'cost of water', without a priori specification of stomatal response to D or atmospheric CO2. The expressions are "emergent properties" of the optimization theory. These emergent responses are compared with data from studies from a wide range of conditions and are shown to be consistent with (1) the onset of an apparent "feed-forward" mechanism, (2) the sensitivity of stomatal conductance to D, and (3) the nonlinear variation in intercellular CO2 concentration with increasing D

  6. A comparison of integrated water vapour measurements of MERIS with COSMO-DE and COSMO-EU model outputs

    NASA Astrophysics Data System (ADS)

    Leinweber, Ronny; Fischer, Jürgen

    2010-05-01

    We present an advanced algorithm for the retrieval of atmospheric integrated water vapor (IWV) over cloud free land areas from satellite data acquired by the Medium Resolution Imaging Spectrometer MERIS on board ENVISAT. The proposed algorithm is based on inverse modeling of radiative transfer simulations by using an artificial neural network. The new algorithm includes the spectral variability of the surface reflectance. Extensive validation provided by a comparison of the retrieved MERIS water vapor concentrations to three different sources of in-situ measurements: measurements of integrated water vapor taken by Microwave Water Radiometers (MWR) on the ARM-SGP site in Oklahoma / USA, by ground based GPS stations in Germany as well as by radio soundings over central Europe. The validation was done for a period of three years from January 2003 to December 2005. For this long validation period a very high agreement with MWR and GPS in-situ data is found. The root mean square deviation is 1.40mm and the bias is 0.11mm for MWR data. For GPS the root mean square deviation is 1.22mm and the bias is 0.97mm. The agreement between MERIS and Radio sonde measurements is good, with a root mean square deviation of 2.28mm and a bias of 1.63mm. Further on we used the new algorithm for a comparison with IWV simulations of two coupled regional climate models, namely the COSMO-DE model covering the area of Germany and the COMSO-EU model covering the area of Europe. The comparison was performed for a period of six years (2005 - 2009).

  7. Atmospheric water on Mars, energy estimates for extraction

    NASA Technical Reports Server (NTRS)

    Meyer, Tom

    1991-01-01

    The Mars atmosphere is considered as a resource for water to support a human expedition. Information obtained from the Viking mission is used to estimate the near-surface water vapor level. The variability over the diurnal cycle is examined and periods of greatest water abundance are identified. Various methods for extracting atmospheric water are discussed including energy costs and the means for optimizing water extraction techniques.

  8. Concentration effects on laser-based δ18 O and δ2 H measurements and implications for the calibration of vapour measurements with liquid standards.

    PubMed

    Schmidt, Markus; Maseyk, Kadmiel; Lett, Céline; Biron, Philippe; Richard, Patricia; Bariac, Thierry; Seibt, Ulli

    2010-12-30

    Recently available isotope ratio infrared spectroscopy can directly measure the isotopic composition of atmospheric water vapour (δ(18) O, δ(2) H), overcoming one of the main limitations of isotope ratio mass spectrometry (IRMS) methods. Calibrating these gas-phase instruments requires the vapourisation of liquid standards since primary standards in principle are liquids. Here we test the viability of calibrating a wavelength-scanned cavity ring-down spectroscopy (CRDS) instrument with vapourised liquid standards. We also quantify the dependency of the measured isotope values on the water concentration for a range of isotopic compositions. In both liquid and vapour samples, we found an increase in δ(18) O and δ(2) H with water vapour concentration. For δ(18) O, the slope of this increase was similar for liquid and vapour, with a slight positive relationship with sample δ-value. For δ(2) H, we found diverging patterns for liquid and vapour samples, with no dependence on δ-value for vapour, but a decreasing slope for liquid samples. We also quantified tubing memory effects to step changes in isotopic composition, avoiding concurrent changes in the water vapour concentration. Dekabon tubing exhibited much stronger, concentration-dependent, memory effects for δ(2) H than stainless steel or perfluoroalkoxy (PFA) tubing. Direct vapour measurements with CRDS in a controlled experimental chamber agreed well with results obtained from vapour simultaneously collected in cold traps analysed by CRDS and IRMS. We conclude that vapour measurements can be calibrated reliably with liquid standards. We demonstrate how to take the concentration dependencies of the δ-values into account. Copyright © 2010 John Wiley & Sons, Ltd. PMID:21080508

  9. Determining Atmospheric Pressure Using a Water Barometer

    ERIC Educational Resources Information Center

    Lohrengel, C. Frederick, II; Larson, Paul R.

    2012-01-01

    The atmosphere is an envelope of compressible gases that surrounds Earth. Because of its compressibility and nonuniform heating by the Sun, it is in constant motion. The atmosphere exerts pressure on Earth's surface, but that pressure is in constant flux. This experiment allows students to directly measure atmospheric pressure by measuring the…

  10. Accuracy assessment of water vapour measurements from in-situ and remote sensing techniques during the DEMEVAP 2011 campaign at OHP

    NASA Astrophysics Data System (ADS)

    Bock, O.; Bosser, P.; Bourcy, T.; David, L.; Goutail, F.; Hoareau, C.; Keckhut, P.; Legain, D.; Pazmino, A.; Pelon, J.; Pipis, K.; Poujol, G.; Sarkissian, A.; Thom, C.; Tournois, G.; Tzanos, D.

    2013-04-01

    The Development of Methodologies for Water Vapour Measurement (DEMEVAP) project aims at assessing and improving humidity sounding techniques and establishing a reference system based on the combination of Raman lidars, ground-based sensors and GPS. Such a system may be used for climate monitoring, radiosonde bias detection and correction, satellite measurement calibration/validation, and mm-level geodetic positioning with Global Navigation Satellite Systems. A field experiment was conducted in September-October 2011 at Observatoire de Haute Provence. Two Raman lidars, a stellar spectrometer (SOPHIE), a differential absorption spectrometer (SAOZ), a sun photometer (AERONET), 5 GPS receivers and 4 types of radiosondes (Vaisala RS92, MODEM M2K2-DC and M10, and Meteolabor Snow-White) participated in the campaign. A total of 26 balloons with multiple radiosondes were flown during 16 clear nights. This paper presents preliminary findings from the analysis of all these datasets. Several classical Raman lidar calibration methods are evaluated which use either Vaisala RS92 measurements, point capacitive humidity measurements, or GPS integrated water vapour (IWV) measurements. A novel method proposed by Bosser et al. (2010) is also tested. It consists in calibrating the lidar measurements during the GPS data processing. The methods achieve a repeatability of 4-5%. A drift in the IGN-LATMOS Raman lidar calibration of 15% over the 45 days of the experiment is evidenced but not yet explained. When this drift is removed, the precision of the calibration factors improves to 2-3%. However, the variations in the absolute calibration factor between methods and types of reference data remain at the level of 7%. The intercomparison of radiosonde measurements shows good agreement between RS92 and Snow-White measurements up to 12 km. An overall dry bias is found in the measurements from both MODEM radiosondes. Investigation of situations with low RH values (<10%) in the lower and middle

  11. Heterogeneous ice nucleation and water uptake by field-collected atmospheric particles below 273 K

    SciTech Connect

    Wang, Bingbing; Laskin, Alexander; Roedel, Tobias R.; Gilles, Marry K.; Moffet, Ryan C.; Tivanski, Alexei V.; Knopf, Daniel A.

    2012-09-25

    Atmospheric ice formation induced by particles with complex chemical and physical properties through heterogeneous nucleation is not well understood. Heterogeneous ice nucleation and water uptake by ambient particles collected from urban environments in Los Angeles and Mexico City are presented. Using a vapour controlled cooling system equipped with an optical microscopy, the range of onset conditions for ice nucleation and water uptake by the collected particles was determined as a function of temperature (200{273 K) and relative humidity with respect to ice (RHice) up to water saturation. Three distinctly different types of authentic atmospheric particles were investigated including soot particles associated with organics/inorganics, inorganic particles of marine origin coated with organic material, and Pb/Zn containing inorganic particles apportioned to anthropogenic emissions relevant to waste incineration. Single particle characterization was provided by micro-spectroscopic analyses using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption ne structure spectroscopy (STXM/NEXAFS). Above 230 K, signicant differences in water uptake and immersion freezing effciencies of the different particle types were observed. Below 230 K, the particles exhibited high deposition ice nucleation effciencies and formed ice at RHice values well below homogeneous ice nucleation limits. The data show that the chemical composition of these eld{collected particles plays an important role in determining water uptake and immersion freezing. Heterogeneous ice nucleation rate coeffcients, cumulative ice nuclei (IN) spectrum, and IN activated fraction for deposition ice nucleation are derived. The presented ice nucleation data demonstrate that anthropogenic and marine particles comprising of various chemical and physical properties exhibit distinctly different ice

  12. Well-controlled metal co-catalysts synthesised by chemical vapour impregnation for photocatalytic hydrogen production and water purification.

    PubMed

    Su, Ren; Forde, Michael M; He, Qian; Shen, Yanbin; Wang, Xueqin; Dimitratos, Nikolaos; Wendt, Stefan; Huang, Yudong; Iversen, Bo B; Kiely, Christopher J; Besenbacher, Flemming; Hutchings, Graham J

    2014-10-28

    As co-catalyst materials, metal nanoparticles (NPs) play crucial roles in heterogeneous photocatalysis. The photocatalytic performance strongly relies on the physical properties (i.e., composition, microstructure, and surface impurities) of the metal NPs. Here we report a convenient chemical vapour impregnation (CVI) approach for the deposition of monometallic-, alloyed, and core-shell structured metal co-catalysts onto the TiO2 photocatalyst. The as-synthesised metal NPs are highly dispersed on the support and show narrow size distributions, which suit photocatalysis applications. More importantly, the surfaces of the as-synthesised metal NPs are free of protecting ligands, enabling the photocatalysts to be ready to use without further treatment. The effect of the metal identity, the alloy chemical composition, and the microstructure on the photocatalytic performance has been investigated for hydrogen production and phenol decomposition. Whilst the photocatalytic H2 production performance can be greatly enhanced by using the core-shell structured co-catalyst (Pdshell-Aucore and Ptshell-Aucore), the Ptshell-Aucore modified TiO2 yields enhanced quantum efficiency but a reduced effective decomposition of phenol to CO2 compared to that of the monometallic counterparts. We consider the CVI approach provides a feasible and elegant process for the decoration of photocatalyst materials. PMID:24970298

  13. Modelling vapour transport in Surtseyan bombs

    NASA Astrophysics Data System (ADS)

    McGuinness, Mark J.; Greenbank, Emma; Schipper, C. Ian

    2016-05-01

    We address questions that arise if a slurry containing liquid water is enclosed in a ball of hot viscous vesicular magma ejected as a bomb in the context of a Surtseyan eruption. We derive a mathematical model for transient changes in temperature and pressure due to flashing of liquid water to vapour inside the bomb. The magnitude of the transient pressure changes that are typically generated are calculated together with their dependence on material properties. A single criterion to determine whether the bomb will fragment as a result of the pressure changes is derived. Timescales for ejection of water vapour from a bomb that remains intact are also revealed.

  14. Cirrus and water vapour transport in the tropical tropopause layer - Part 2: Roles of ice nucleation and sedimentation, cloud dynamics, and moisture conditions

    NASA Astrophysics Data System (ADS)

    Dinh, T.; Fueglistaler, S.; Durran, D.; Ackerman, T.

    2014-11-01

    A high-resolution, two-dimensional numerical model is used to study the moisture redistribution following homogeneous ice nucleation induced by Kelvin waves in the tropical tropopause layer (TTL). We compare results for dry/moist initial conditions and three levels of complexity for the representation of cloud processes: complete microphysics and cloud radiative effects, likewise but without radiative effects, and instantaneous removal of moisture in excess of saturation upon nucleation. Cloud evolution and moisture redistribution are found to be sensitive to initial conditions and cloud processes. Ice sedimentation leads to a downward flux of water, whereas the cloud radiative heating induces upward advection of the cloudy air. The latter results in an upward (downward) flux of water vapour if the cloudy air is moister (drier) than the environment, which is typically when the environment is subsaturated (supersaturated). Only a fraction (~25% or less) of the cloud experiences nucleation. Post-nucleation processes (ice depositional growth, sedimentation, and sublimation) are important to cloud morphology, and both dehydrated and hydrated layers may be indicators of TTL cirrus occurrence. The calculation with instantaneous removal of moisture not only misses the hydration but also underestimates dehydration due to (i) nucleation before reaching the minimum saturation mixing ratio, and (ii) lack of moisture removal from sedimenting ice particles below the nucleation level. The sensitivity to initial conditions and cloud processes suggests that it is difficult to reach generic, quantitative estimates of cloud-induced moisture redistribution on the basis of case-by-case calculations.

  15. On-line separation for the speciation of mercury in natural waters by flow injection-cold vapour-atomic absorption spectrometry.

    PubMed

    Sanz, Jon; Raposo, Juan Carlos; Larreta, Joana; Martinez-Arkarazo, Irantzu; de Diego, Alberto; Madariaga, Juan Manuel

    2004-10-01

    Inorganic mercury and methylmercury are determined in natural waters by injecting the filtered samples onto a low cost commercial flow injection system in which an anion exchange microcolumn is inserted after the injection loop (FIA-IE). If hydrochloric acid is used as the carrier solution, the HgCl4(2-) species (inorganic mercury) will be retained by the anion exchanger while the CH3HgCI species (methylmercury) will flow through the resin with negligible retention. Four anion exchangers and seven elution agents were checked, in a batch mode, to search for the best conditions for optimal separation and elution of both species. Dowex M-41 and L-cysteine were finally selected. Mercury detection was performed by cold vapour-electrothermal atomic adsorption spectrometry (HG-ETAAS). Both systems were coupled to perform the continuous on-line separation/detection of both inorganic mercury and methylmercury species. Separation and detection conditions were optimized by two chemometric approaches: full factorial design and central composite design. A limit of detection of 0.4 microg L(-1) was obtained for both mercury species (RSD < 3.0% for 20 microg L(-1) inorganic and methylmercury solutions). The method was applied to mercury speciation in natural waters of the Nerbioi-lbaizabal estuary (Bilbao, North of Spain) and recoveries of more than 95% were obtained. PMID:15537077

  16. Atmospheric corrections for satellite water quality studies

    NASA Technical Reports Server (NTRS)

    Piech, K. R.; Schott, J. R.

    1975-01-01

    Variations in the relative value of the blue and green reflectances of a lake can be correlated with important optical and biological parameters measured from surface vessels. Measurement of the relative reflectance values from color film imagery requires removal of atmospheric effects. Data processing is particularly crucial because: (1) lakes are the darkest objects in a scene; (2) minor reflectance changes can correspond to important physical changes; (3) lake systems extend over broad areas in which atmospheric conditions may fluctuate; (4) seasonal changes are of importance; and, (5) effects of weather are important, precluding flights under only ideal weather conditions. Data processing can be accomplished through microdensitometry of scene shadow areas. Measurements of reflectance ratios can be made to an accuracy of plus or minus 12%, sufficient to permit monitoring of important eutrophication indices.

  17. Interactive effects of soil water deficit and air vapour pressure deficit on mesophyll conductance to CO2 in Vitis vinifera and Olea europaea.

    PubMed

    Perez-Martin, A; Flexas, J; Ribas-Carbó, M; Bota, J; Tomás, M; Infante, J M; Diaz-Espejo, A

    2009-01-01

    The present work aims to study the interactive effect of drought stress and high vapour pressure deficit (VPD) on leaf gas exchange, and especially on mesophyll conductance to CO(2) (g(m)), in two woody species of great agronomical importance in the Mediterranean basin: Vitis vinifera L. cv. Tempranillo and Olea europaea L. cv. Manzanilla. Plants were grown in specially designed outdoor chambers with ambient and below ambient VPD, under both well-irrigated and drought conditions. g(m) was estimated by the variable J method from simultaneous measurements of gas exchange and fluorescence. In both species, the response to soil water deficit was larger in g(s) than in g(m), and more important than the response to VPD. Olea europaea was apparently more sensitive to VPD, so that plants growing in more humid chambers showed higher g(s) and g(m). In V. vinifera, in contrast, soil water deficit dominated the response of g(s) and g(m). Consequently, changes in g(m)/g(s) were more related to VPD in O. europaea and to soil water deficit in V. vinifera. Most of the limitations of photosynthesis were diffusional and especially due to stomatal closure. No biochemical limitation was detected. The results showed that structural parameters played an important role in determining g(m) during the acclimation process. Although the relationship between leaf mass per unit area (M(A)) with g(m) was scattered, it imposed a limitation to the maximum g(m) achievable, with higher values of M(A) in O. europaea at lower g(m) values. M(A) decreased under water stress in O. europaea but it increased in V. vinifera. This resulted in a negative relationship between M(A) and the CO(2) draw-down between substomatal cavities and chloroplasts in O. europaea, while being positive in V. vinifera. PMID:19457982

  18. Factors governing water condensation in the Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Colburn, David S.; Pollack, J. B.; Haberle, Robert M.

    1988-01-01

    Modeling results are presented suggesting a diurnal condensation cycle at high altitudes at some seasons and latitudes. In a previous paper, the use of atmospheric optical depth measurements at the Viking lander site to show diurnal variability of water condensation at different seasons of the Mars year was described. Factors influencing the amount of condensation include latitude, season, atmospheric dust content and water vapor content at the observation site. A one-dimensional radiative-convective model is used herein based on the diabatic heating routines under development for the Mars General Circulation Model. The model predicts atmospheric temperature profiles at any latitude, season, time of day and dust load. From these profiles and an estimate of the water vapor, one can estimate the maximum occurring at an early morning hour (AM) and the minimum in the late afternoon (PM). Measured variations in the atmospheric optical density between AM and PM measurements were interpreted as differences in AM and PM condensation.

  19. Determining the stable isotope composition of pore water from saturated and unsaturated zone core: improvements to the direct vapour equilibration laser spectrometry method

    NASA Astrophysics Data System (ADS)

    Hendry, M. J.; Schmeling, E.; Wassenaar, L. I.; Barbour, S. L.; Pratt, D.

    2015-11-01

    A method to measure the δ2H and δ18O composition of pore waters in saturated and unsaturated geologic core samples using direct vapour equilibration and laser spectrometry (DVE-LS) was first described in 2008, and has since been rapidly adopted. Here, we describe a number of important methodological improvements and limitations encountered in routine application of DVE-LS over several years. Generally, good comparative agreement, as well as accuracy, is obtained between core pore water isotopic data obtained using DVE-LS and that measured on water squeezed from the same core. In complex hydrogeologic settings, high-resolution DVE-LS depth profiles provide greater spatial resolution of isotopic profiles compared to long-screened or nested piezometers. When fluid is used during drilling and coring (e.g. water rotary or wet sonic drill methods), spiking the drill fluid with 2H can be conducted to identify core contamination. DVE-LS analyses yield accurate formational isotopic data for fine-textured core (e.g. clay, shale) samples, but are less effective for cores obtained from saturated permeable (e.g. sand, gravels) geologic media or on chip samples that are easily contaminated by wet rotary drilling fluid. Data obtained from DVE-LS analyses of core samples collected using wet (contamination by drill water) and dry sonic (water loss by heating) methods were also problematic. Accurate DVE-LS results can be obtained on core samples with gravimetric water contents > 5 % by increasing the sample size tested. Inexpensive Ziploc™ gas-sampling bags were determined to be as good as, if not better than, other, more expensive specialty bags. Sample storage in sample bags provides acceptable results for up to 10 days of storage; however, measurable water loss, as well as evaporitic isotopic enrichment, occurs for samples stored for up to 6 months. With appropriate care taken during sample collection and storage, the DVE-LS approach for obtaining high-resolution pore water

  20. Mechanical properties and water vapour permeability of film from Haruan (Channa striatus) and fusidic acid spray for wound dressing and wound healing.

    PubMed

    Febriyenti; Noor, Azmin Mohd; Bai, Saringat Bin

    2010-04-01

    Aerosol is a new dosage form for wound dressing and wound healing. Concentrate of aerosols which were prepared for wound dressing and wound healing will produced films after sprayed onto the surface of wounds. The aim of this study is to evaluate the mechanical and water vapour permeability properties of the films from the aerosol concentrates. Film forming dispersions contained Haruan extract and Fusidic acid as the active ingredients, hydroxypropyl methylcellulose (HPMC) as polymer and polyethylene glycol (PEG) 400, glycerin and propylene glycol as plasticizers. Haruan extract is used to promote healing and Fusidic acid is added in formula as antibiotic to prevent the infections. The films were prepared by using casting technique. Based on the results, it is concluded that films produced from Formula E1, E2 and F4 possessed good elongation at break but low tensile strength. All Formula E, Formula F4 and F5 were permeable but Formula F5 was brittle and would peel off by themselves from the Petri dish. PMID:20363692

  1. Analysis of carbon dioxide, water vapour and energy fluxes over an Indian teak mixed deciduous forest for winter and summer months using eddy covariance technique

    NASA Astrophysics Data System (ADS)

    Jha, Chandra Shekhar; Thumaty, Kiran Chand; Rodda, Suraj Reddy; Sonakia, Ajit; Dadhwal, Vinay Kumar

    2013-10-01

    In the present study, we report initial results on analysis of carbon dioxide (CO2), water vapour (H2O), and energy fluxes (sensible and latent heat flux) over teak mixed deciduous forests of Madhya Pradesh, central India, during winter (November 2011 and January 2012) and summer (February-May 2012) seasons using eddy covariance flux tower datasets. During the study period, continuous fast response measurements of CO2, H2O and heat fluxes above the canopy were carried out at 10 Hz and averaged for 30 minutes. Concurrently, slow response measurements of meteorological parameters are also being carried out. Diurnal and seasonal variations of CO2, H2O and heat fluxes were analysed and correlated with the meteorological variables. The study showed strong influence of leaf off and on scenario on the CO2, H2O and energy fluxes due to prevalence of deciduous vegetation type in the study area. Maximum amount of CO2 was sequestered for photosynthesis during winter (monthly mean of mol/m2/s) compared to summer (monthly mean of mol/m2/s). Energy flux analysis (weekly mean) showed more energy being portioned into latent heat during winter (668 W/m2) and sensible heat during summer (718 W/m2).

  2. Robust, spatially scanning, open-path TDLAS hygrometer using retro-reflective foils for fast tomographic 2-D water vapour concentration field measurements

    NASA Astrophysics Data System (ADS)

    Seidel, A.; Wagner, S.; Dreizler, A.; Ebert, V.

    2014-12-01

    We have developed a fast, spatially direct scanning tunable diode laser absorption spectrometer (dTDLAS) that combines four polygon-mirror based scanning units with low-cost retro-reflective foils. With this instrument, tomographic measurements of absolute 2-D water vapour concentration profiles are possible without any calibration using a reference gas. A spatial area of 0.8 m × 0.8 m was covered, which allows for application in soil physics, where greenhouse gas emission from certain soil structures shall be monitored. The whole concentration field was measured with up to 2.5 Hz. In this paper, we present the setup and spectroscopic performance of the instrument regarding the influence of the polygon rotation speed and mode on the absorption signal. Homogeneous H2O distributions were measured and compared to a single channel, bi-static reference TDLAS spectrometer for validation of the instrument. Good accuracy and precision with errors of less than 6% of the absolute concentration and length and bandwidth normalized detection limits of up to 1.1 ppmv · m · √Hz-1 were achieved. The spectrometer is a robust and easy to set up instrument for tomographic reconstructions of 2-D-concentration fields that can be considered a good basis for future field measurements in environmental research.

  3. Isotopic composition of atmospheric moisture from pan water evaporation measurements.

    PubMed

    Devi, Pooja; Jain, Ashok Kumar; Rao, M Someshwer; Kumar, Bhishm

    2015-01-01

    A continuous and reliable time series data of the stable isotopic composition of atmospheric moisture is an important requirement for the wider applicability of isotope mass balance methods in atmospheric and water balance studies. This requires routine sampling of atmospheric moisture by an appropriate technique and analysis of moisture for its isotopic composition. We have, therefore, used a much simpler method based on an isotope mass balance approach to derive the isotopic composition of atmospheric moisture using a class-A drying evaporation pan. We have carried out the study by collecting water samples from a class-A drying evaporation pan and also by collecting atmospheric moisture using the cryogenic trap method at the National Institute of Hydrology, Roorkee, India, during a pre-monsoon period. We compared the isotopic composition of atmospheric moisture obtained by using the class-A drying evaporation pan method with the cryogenic trap method. The results obtained from the evaporation pan water compare well with the cryogenic based method. Thus, the study establishes a cost-effective means of maintaining time series data of the isotopic composition of atmospheric moisture at meteorological observatories. The conclusions drawn in the present study are based on experiments conducted at Roorkee, India, and may be examined at other regions for its general applicability. PMID:26332982

  4. Lidar simulation. [measurement of atmospheric water vapor via optical radar

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The feasibility of measuring atmospheric water vapor via orbital lidar is estimated. The calculation starts with laser radar equations representing backscatter with and without molecular line absorption; the magnitudes of off-line backscatter are demonstrated. Extensive prior data on water line strengths are summarized to indicate the available sensitivity to water vapor concentration. Several lidar situations are considered starting with uniform and perturbed atmospheres at 0, 3, 10 and 20 kM (stratosphere) altitudes. These simulations are indicative of results to be obtained in ground truth measurements (ground-based and airborne). An approximate treatment of polar observations is also given. Vertical atmospheric soundings from orbit and from ground stations are calculated. Errors are discussed as regards their propagation through the lidar equation to render the measured water vapor concentration imprecise; conclusions are given as to required laser energy and feasible altitude resolution.

  5. Carbon dioxide and water vapour exchange in a tropical dry forest as influenced by the North American Monsoon System (NAMS)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To better understand the effects and relationship between precipitation, net ecosystem carbon dioxide (NEE) and water vapor exchange (ET), we report a study conducted in the tropical dry forest (TDF) in the northwest of Mexico. Ecosystem gas exchange was measured using the eddy correlation technique...

  6. Characterisation and source attribution of the semi-volatile organic content of atmospheric particles and associated vapour phase in Birmingham, UK

    NASA Astrophysics Data System (ADS)

    Harrad, Stuart; Hassoun, Suzanne; Callén Romero, María. S.; Harrison, Roy M.

    Concentrations of n-alkanes, petroleum biomarkers such as hopanes and steranes, n-alkanoic acids, n-alkanols, polycyclic aromatic hydrocarbons (PAH), dicarboxylic acids, and selected oxygenated PAH were separately determined in total suspended particulate matter and associated vapour phase in ambient air in Birmingham, UK. Samples were taken simultaneously at two locations on 24 separate occasions every 1-2 weeks between August 1999 and August 2000. Site A was 10 m from a busy road, 800 m from site B that was located within the "green space" of the University of Birmingham campus. Despite some differences in concentrations of some compounds, data from this study is in line with that reported in London, UK and in California. Differences between Sites A and B in both concentrations and carbon preference indices are consistent with greater traffic inputs at Site A, with some evidence of an appreciable biogenic input of n-alkanols and n-alkanes at the less-traffic influenced and more vegetated Site B. The biogenic input at Site B appears greater in the spring and summer months and suggests that biogenic emissions are appreciable even in British urban areas. Secondary formation mechanisms for some compounds including dicarboxylic acids and oxygenated PAH like fluoren-9-one are indicated by the lack of any significant intersite difference in concentrations. Intersite differences in concentrations provide new evidence that while petroleum biomarkers arise predominantly from local traffic, regional as well as local sources play an important rôle for the higher molecular weight PAH which exist predominantly in the particle phase.

  7. Fiber-based lidar for atmospheric water-vapor measurements.

    PubMed

    Little, L M; Papen, G C

    2001-07-20

    The design and evaluation of a prototype fiber-based lidar system for autonomous measurement of atmospheric water vapor are presented. The system components are described, along with current limitations and options for improvement. Atmospheric measurements show good agreement with modeled signal returns from 400 to 1000 m but are limited below 400 m as a result of errors in signal processing caused by violation of the assumptions used in the derivation of the differential absorption lidar equation. PMID:18360367

  8. Open- vs. closed-path eddy covariance measurements of the net ecosystem carbon dioxide and water vapour exchange: a long-term perspective.

    PubMed

    Haslwanter, Alois; Hammerle, Albin; Wohlfahrt, Georg

    2009-02-01

    The differential design, deployment and data post-processing of open- (OP) and closed-path (CP) eddy covariance systems is a potential source of bias for ongoing global flux synthesis activities. Here we use a unique six year data set of concurrent CP and OP carbon dioxide (CO2) and water vapour (H2O) eddy covariance flux measurements above a temperate mountain grassland in Austria to explore the consequences of these differences on a long-term basis. The theoretically based transfer function approach was able to account and correct for the differences in low-pass filtering between the two systems. Corrected CO2 and H2O fluxes exhibited excellent 1:1 correspondence, but the CP system tended to underestimate OP H2O fluxes during conditions of high air temperature, wind speed and global radiation, large sun angles and low relative humidity. Corrections for self-heating of the OP infra-red gas analyser had a very small effect on these relationships. Energy balance closure was slightly more favourable for the OP system. No significant differences were found for the random flux uncertainty of both systems. A larger fraction of OP data had to be excluded because of obstructions of the infra-red path by water and snow. This, however, did not translate into a correspondingly larger fraction of accepted CP flux values, because of a larger percentage of CP flux data failing on the stationarity test. Integrated over the annual cycle, the CP system yielded on average a more positive net ecosystem CO2 exchange (25 vs. 0 gC m(-2) y(-1)) and a lower evapotranspiration (465 vs. 549 mm y(-1)) as compared to the OP system. PMID:24465069

  9. Open- vs. closed-path eddy covariance measurements of the net ecosystem carbon dioxide and water vapour exchange: a long-term perspective

    PubMed Central

    Haslwanter, Alois; Hammerle, Albin; Wohlfahrt, Georg

    2014-01-01

    The differential design, deployment and data post-processing of open- (OP) and closed-path (CP) eddy covariance systems is a potential source of bias for ongoing global flux synthesis activities. Here we use a unique six year data set of concurrent CP and OP carbon dioxide (CO2) and water vapour (H2O) eddy covariance flux measurements above a temperate mountain grassland in Austria to explore the consequences of these differences on a long-term basis. The theoretically based transfer function approach was able to account and correct for the differences in low-pass filtering between the two systems. Corrected CO2 and H2O fluxes exhibited excellent 1:1 correspondence, but the CP system tended to underestimate OP H2O fluxes during conditions of high air temperature, wind speed and global radiation, large sun angles and low relative humidity. Corrections for self-heating of the OP infra-red gas analyser had a very small effect on these relationships. Energy balance closure was slightly more favourable for the OP system. No significant differences were found for the random flux uncertainty of both systems. A larger fraction of OP data had to be excluded because of obstructions of the infra-red path by water and snow. This, however, did not translate into a correspondingly larger fraction of accepted CP flux values, because of a larger percentage of CP flux data failing on the stationarity test. Integrated over the annual cycle, the CP system yielded on average a more positive net ecosystem CO2 exchange (25 vs. 0 gC m−2 y−1) and a lower evapotranspiration (465 vs. 549 mm y−1) as compared to the OP system. PMID:24465069

  10. OPERA: An Atmospheric Correction for Land and Water

    NASA Astrophysics Data System (ADS)

    Sterckx, Sindy; Knaeps, Els; Adriaensen, Stefan; Reusen, Ils; De Keukelaere, Liesbeth; Hunter, Peter; Giardino, Claudia; Odermatt, Daniel

    2015-12-01

    Atmospheric correction is one of the most important part of the pre-processing of satellite remotely sensed data used to retrieve bio-geophysical paramters. In this paper we present the scene and sensor generic atmospheric correction scheme ‘OPERA’ allowing to correct both land and water areas in the remote sensing image. OPERA can now be used to correct for atmospheric effects in scenes acquired by MERIS, Landsat-8, hyperspectral sensors and will be applicable to Sentinel-3 and Sentinel-2.

  11. Modeling of the Process of Three-Isotope (H, D, T) Exchange Between Hydrogen Gas and Water Vapour on Pt-SDBC Catalyst over a Wide Range of Deuterium Concentration

    SciTech Connect

    Fedorchenko, O.A.; Alekseev, I.A.; Tchijov, A.S.; Uborsky, V.V.

    2005-07-15

    The large scale studies of Combined Electrolysis and Catalytic Exchange (CECE) process in Petersburg Nuclear Physics Institute showed a complicated influence of various factors on the process caused by the presence of two simultaneous isotope exchange sub processes: counter-current phase exchange (between liquid water and water vapour) and co-current catalytic exchange (between hydrogen gas and water vapour). A laboratory scale set-up of glass made apparatuses was established in such a way that it allows us to study phase and catalytic exchange apart. A computer model of the set-up has been developed.The catalytic isotope exchange model formulation is presented. A collection of reversible chemical reactions is accompanied by diffusion of the gaseous reactants and reaction products in the pores of catalyst carrier. This has some interesting features that are demonstrated. Thus it was noted that the flow rates ratio (gas to vapour - {lambda} = G/V) as well as the concentrations of reactants exert influence on the process efficiency.

  12. The delayed impact of a summer drought on the carbon and water vapour fluxes exchanged by a European beech forest

    NASA Astrophysics Data System (ADS)

    Longdoz, B.; Gross, P.; Bréda, N.; Granier, A.

    2012-12-01

    The Hesse experimental site is located in a beech homogeneous forest in the North-East of France. It is equipped since 1997 (15 years of measurements) with an eddy covariance system (net ecosystem exchange NEE and ecosystem evapotranspiration ET) and some sensors measuring meteorological and soil environmental factors. In addition regular field campaigns are performed to monitor the trees growth and phenology. The occurrence of a severe drought during 2003 with precipitations equivalent to only 66% of the mean annual value lead to important modification in the ecosystem behaviour. A direct impact on NEE, ET and tree growth was clearly seen when the quantity of extractable water (soil water that can extracted by tree roots) pass below 40% of its maximum. This threshold seems to be similar for different tested European forests. In addition to this disturbance, the lack of carbohydrate storage induced, during the following season, a large reduction of the Leaf Area Index and beech radial growth. This was not the only delayed effect of soil water stress as parameters determining the Gross Primary Productivity (GPP) as the assimilation rate at light saturation or quantum yield were also significantly influenced. When comparing the potential annual GPP (corresponding to the estimation from GPP dependence on climatic and soil conditions where conditions averaged over the 15 measuring years are used), the 2004 was the lowest one over the 1995-2011 period when years impacted by thinning were excluded. This shows the structural consequence of soil drought. The ability of the inter-annual ecosystem models to reproduce these observations is a good quality test for their carbon storage and partitioning components.

  13. Profiling of Atmospheric Water Vapor with MIR and LASE

    NASA Technical Reports Server (NTRS)

    Wang, J. R.; Racette, P.; Triesly, M. E.; Browell, E. V.; Ismail, S.; Chang, L. A.; Hildebrand, Peter H. (Technical Monitor)

    2001-01-01

    This paper presents the first and the only simultaneous measurements of water vapor by MIR (Millimeter-wave Imaging Radiometer) and LASE (Lidar Atmospheric Sounding Experiment) on board the same ER-2 aircraft. Water vapor is one of the most important constituents in the Earth's atmosphere, as its spatial and temporal variations affect a wide spectrum of meteorological phenomena ranging from the formation of clouds to the development of severe storms. Its concentration, as measured in terms of relative humidity, determines the extinction coefficient of atmospheric aerosol particles and therefore visibility. These considerations point to the need for effective and frequent measurements of the atmospheric water vapor. The MIR and LASE instruments provide measurements of water vapor profiles with two markedly different techniques. LASE can give water vapor profiles with excellent vertical resolution under clear condition, while MIR can retrieve water vapor profiles with a crude vertical resolution even under a moderate cloud cover. Additionally, millimeter-wave measurements are relatively simple and provide better spatial coverage.

  14. Atmospheric Precorrected Differential Absorption technique to retrieve columnar water vapor

    SciTech Connect

    Schlaepfer, D.; Itten, K.I.; Borel, C.C.; Keller, J.

    1998-09-01

    Differential absorption techniques are suitable to retrieve the total column water vapor contents from imaging spectroscopy data. A technique called Atmospheric Precorrected Differential Absorption (APDA) is derived directly from simplified radiative transfer equations. It combines a partial atmospheric correction with a differential absorption technique. The atmospheric path radiance term is iteratively corrected during the retrieval of water vapor. This improves the results especially over low background albedos. The error of the method for various ground reflectance spectra is below 7% for most of the spectra. The channel combinations for two test cases are then defined, using a quantitative procedure, which is based on MODTRAN simulations and the image itself. An error analysis indicates that the influence of aerosols and channel calibration is minimal. The APDA technique is then applied to two AVIRIS images acquired in 1991 and 1995. The accuracy of the measured water vapor columns is within a range of {+-}5% compared to ground truth radiosonde data.

  15. High-resolution terahertz atmospheric water vapor continuum measurements

    NASA Astrophysics Data System (ADS)

    Slocum, David M.; Goyette, Thomas M.; Giles, Robert H.

    2014-05-01

    The terahertz frequency regime is often used as the `chemical fingerprint' region of the electromagnetic spectrum due to the large number of rotational and vibrational transitions of many molecules of interest. This region of the spectrum has particular utility for applications such as pollution monitoring and the detection of energetic chemicals using remote sensing over long path lengths through the atmosphere. Although there has been much attention to atmospheric effects over narrow frequency windows, accurate measurements across a wide spectrum are lacking. The water vapor continuum absorption is an excess absorption that is unaccounted for in resonant line spectrum simulations. Currently a semiempirical model is employed to account for this absorption, however more measurements are necessary to properly describe the continuum absorption in this region. Fourier Transform Spectroscopy measurements from previous work are enhanced with high-resolution broadband measurements in the atmospheric transmission window at 1.5THz. The transmission of broadband terahertz radiation through pure water vapor as well as air with varying relative humidity levels was recorded for multiple path lengths. The pure water vapor measurements provide accurate determination of the line broadening parameters and experimental measurements of the transition strengths of the lines in the frequency region. Also these measurements coupled with the atmospheric air measurements allow the water vapor continuum absorption to be independently identified at 1.5THz. Simulations from an atmospheric absorption model using parameters from the HITRAN database are compared with the current and previous experimental results.

  16. Atmospheric correction of AVIRIS data in ocean waters

    NASA Technical Reports Server (NTRS)

    Terrie, Gregory; Arnone, Robert

    1992-01-01

    Hyperspectral data offers unique capabilities for characterizing the ocean environment. The spectral characterization of the composition of ocean waters can be organized into biological and terrigenous components. Biological photosynthetic pigments in ocean waters have unique spectral ocean color signatures which can be associated with different biological species. Additionally, suspended sediment has different scattering coefficients which result in ocean color signatures. Measuring the spatial distributions of these components in the maritime environments provides important tools for understanding and monitoring the ocean environment. These tools have significant applications in pollution, carbon cycle, current and water mass detection, location of fronts and eddies, sewage discharge and fate etc. Ocean color was used from satellite for describing the spatial variability of chlorophyll, water clarity (K(sub 490)), suspended sediment concentration, currents etc. Additionally, with improved atmospheric correction methods, ocean color results produced global products of spectral water leaving radiance (L(sub W)). Ocean color results clearly indicated strong applications for characterizing the spatial and temporal variability of bio-optical oceanography. These studies were largely the results of advanced atmospheric correction techniques applied to multispectral imagery. The atmosphere contributes approximately 80 percent - 90 percent of the satellite received radiance in the blue-green portion of the spectrum. In deep ocean waters, maximum transmission of visible radiance is achieved at 490nm. Conversely, nearly all of the light is absorbed by the water at wavelengths greater than about 650nm and thus appears black. These spectral ocean properties are exploited by algorithms developed for the atmospheric correction used in satellite ocean color processing. The objective was to apply atmospheric correction techniques that were used for procesing satellite Coastal

  17. Atmospheric solar heating rate in the water vapor bands

    NASA Technical Reports Server (NTRS)

    Chou, Ming-Dah

    1986-01-01

    The total absorption of solar radiation by water vapor in clear atmospheres is parameterized as a simple function of the scaled water vapor amount. For applications to cloudy and hazy atmospheres, the flux-weighted k-distribution functions are computed for individual absorption bands and for the total near-infrared region. The parameterization is based upon monochromatic calculations and follows essentially the scaling approximation of Chou and Arking, but the effect of temperature variation with height is taken into account in order to enhance the accuracy. Furthermore, the spectral range is extended to cover the two weak bands centered at 0.72 and 0.82 micron. Comparisons with monochromatic calculations show that the atmospheric heating rate and the surface radiation can be accurately computed from the parameterization. Comparisons are also made with other parameterizations. It is found that the absorption of solar radiation can be computed reasonably well using the Goody band model and the Curtis-Godson approximation.

  18. Annual Book of ASTM Standards, Part 23: Water; Atmospheric Analysis.

    ERIC Educational Resources Information Center

    American Society for Testing and Materials, Philadelphia, PA.

    Standards for water and atmospheric analysis are compiled in this segment, Part 23, of the American Society for Testing and Materials (ASTM) annual book of standards. It contains all current formally approved ASTM standard and tentative test methods, definitions, recommended practices, proposed methods, classifications, and specifications. One…

  19. Atmospheric correction for Landsat 8 over case 2 waters

    NASA Astrophysics Data System (ADS)

    Concha, Javier A.; Schott, John R.

    2015-09-01

    The most interaction between humankind and water occurs in coastal and inland waters (Case 2 waters) at a scale of tens or hundred of meters, but there is not yet an ocean color product at this spatial scale. Landsat 8 is a promising candidate to address the remote sensing of these kinds of waters due to its improved signal-to-noise ratio (SNR), spectral resolution, 12-bit quantization, and high spatial resolution. Standard atmospheric correction algorithms developed for heritage ocean color instruments (e.g. MODIS, SeaWiFS) require a sufficient SNR in two bands where the water-leaving signal is negligible, which is not always possible, particularly for Landsat 8's bands. The model-based empirical line method (MoB-ELM) atmospheric algorithm for Landsat 8 imagery does not rely on this assumption. In this work, we evaluate the performance of this algorithm. We compare the MoB-ELM algorithm with in situ data and with three standard atmospheric correction algorithms. The results from our algorithm are comparable with the standard algorithms in some bands when comparing remote-sensing reflectances. When compared with in situ remote-sensing reflectance, the MoB-ELM perform similar to the standard algorithm in most cases. A comparison of retrieved chlorophyll-a concentration was perform as well, showing that the MoB- ELM outperforms the rest at high concentrations commonly found in Case 2 waters. These results show that our atmospheric correction algorithm allows one to use Landsat 8 to study Case 2 waters as an alternative to heritage ocean color satellites.

  20. Water loss from Venus: Implications for the Earth's early atmosphere

    NASA Technical Reports Server (NTRS)

    Richardson, S. M.; Pollack, J. B.; Reynolds, R. T.

    1985-01-01

    The atmosphere of Venus outgassed rapidly as a result of planetary heating during accretion, resulting in massive water loss. The processes affecting atmospheric chemistry following accretion have consisted largely of hydrogen escape and internal re-equilibrium. The initial bulk composition of Venus and Earth are assumed to have been roughly similar. Chemical speciation on Venus was controlled by the temperature and oxygen buffering capacity of the surface magma. It is also assumed that the surfaces of planetary bodies of the inner solar system were partly or wholly molten during accretion with a temperature estimated at 1273 to 1573 K. To investigate the range of reasonable initial atmospheric compositions on Venus, limits have to be set for the proportion of total hydrogen and the buffered fugacity of oxygen. Using the C/H ratio of 0.033 set for Earth, virtually all of the water generated during outgassing must later have been lost in order to bring the current CO2/H2O ratio for Venus up to its observed value of 10 sup 4 to 10 sup 5. The proportion of H2O decreases in model atmospheres with successfully higher C/H values, ultimately approaching the depleted values currently observed on Venus. Increasing C/H also results in a rapid increase in CO/H2O and provides an efficient mechanism for water loss by the reaction CO+H2O = CO2 + H2. This reaction, plus water loss mechanisms involving crustal iron, could have removed a very large volume of water from the Venusian atmosphere, even at a low C/H value.

  1. Heat of freezing for supercooled water: measurements at atmospheric pressure.

    PubMed

    Cantrell, Will; Kostinski, Alexander; Szedlak, Anthony; Johnson, Alexandria

    2011-06-16

    Unlike reversible phase transitions, the amount of heat released upon freezing of a metastable supercooled liquid depends on the degree of supercooling. Although terrestrial supercooled water is ubiquitous and has implications for cloud dynamics and nucleation, measurements of its heat of freezing are scarce. We have performed calorimetric measurements of the heat released by freezing water at atmospheric pressure as a function of supercooling. Our measurements show that the heat of freezing can be considerably below one predicted from a reversible hydrostatic process. Our measurements also indicate that the state of the resulting ice is not fully specified by the final pressure and temperature; the ice is likely to be strained on a variety of scales, implying a higher vapor pressure. This would reduce the vapor gradient between supercooled water and ice in mixed phase atmospheric clouds. PMID:21087023

  2. Atmospheric water uptake by an atacama desert shrub.

    PubMed

    Mooney, H A; Gulmon, S L; Ehleringer, J; Rundel, P W

    1980-08-01

    Nolana mollis, a succulent-leaved shrub of the extreme coastal desert of Chile, has the capacity to condense water on its leaves out of unsaturated atmospheres, Metabolic energy would have to be expended to move this water either from the leaf surface directly to the mesophyll or, when dripped to the soil, from there into the roots. Because of the unusual aridity of its habitat and of the utilization of water-use-efficient metabolism by Nolana, at least during certain periods, such an energy expenditure could be effective. PMID:17821192

  3. Electron deposition in water vapor, with atmospheric applications.

    NASA Technical Reports Server (NTRS)

    Olivero, J. J.; Stagat, R. W.; Green, A. E. S.

    1972-01-01

    Examination of the consequences of electron impact on water vapor in terms of the microscopic details of excitation, dissociation, ionization, and combinations of these processes. Basic electron-impact cross-section data are assembled in many forms and are incorporated into semianalytic functions suitable for analysis with digital computers. Energy deposition in water vapor is discussed, and the energy loss function is presented, along with the 'electron volts per ion pair' and the efficiencies of energy loss in various processes. Several applications of electron and water-vapor interactions in the atmospheric sciences are considered, in particular, H2O comets, aurora and airglow, and lightning.

  4. Follow The Water: The Ultimate WFC3 Exoplanet Atmosphere Survey

    NASA Astrophysics Data System (ADS)

    Bean, Jacob

    2013-10-01

    Recent surveys have revealed an amazing, and yet unexplained, diversity of planets orbiting other stars. Studying the atmospheres of representative exoplanets is the key next step in leveraging these detections to further transform our understanding of planet formation and planetary physics. This is because a planet's atmosphere is a fossil record of its primordial origins and controls its size and appearance.We propose an intensive and comprehensive exoplanet atmosphere Large Treasury survey using the unrivaled capabilities of the WFC3 IR instrument to measure high-precision transmission, dayside emission, and phase-resolved emission spectra over a broad wavelength range for eight planetary Rosetta Stones. These data will yield unprecedented constraints on the abundances of water, elemental abundance ratios, thermal profiles, chemistries, presence of clouds and hazes, and dynamics of exoplanet atmospheres. Just detecting the atmospheres of these planets is not enough anymore. Revealing the fundamental properties of exoplanet atmospheres to investigate their nature and origins requires high-precision spectroscopy that is sensitive to spectral features from multiple chemical species and altitudes, and such data can only be obtained with an intensive HST program. A survey is mandatory to put the individual objects in a broader context, and to get at the underlying physics that results in a diverse array of emergent properties. This Treasury program will have no proprietary period in order to accelerate the progress of the field. This program is urgently needed to prepare for the future characterization of habitable exoplanets using JWST.

  5. ANALYTICAL MODELS OF EXOPLANETARY ATMOSPHERES. I. ATMOSPHERIC DYNAMICS VIA THE SHALLOW WATER SYSTEM

    SciTech Connect

    Heng, Kevin; Workman, Jared E-mail: jworkman@coloradomesa.edu

    2014-08-01

    Within the context of exoplanetary atmospheres, we present a comprehensive linear analysis of forced, damped, magnetized shallow water systems, exploring the effects of dimensionality, geometry (Cartesian, pseudo-spherical, and spherical), rotation, magnetic tension, and hydrodynamic and magnetic sources of friction. Across a broad range of conditions, we find that the key governing equation for atmospheres and quantum harmonic oscillators are identical, even when forcing (stellar irradiation), sources of friction (molecular viscosity, Rayleigh drag, and magnetic drag), and magnetic tension are included. The global atmospheric structure is largely controlled by a single key parameter that involves the Rossby and Prandtl numbers. This near-universality breaks down when either molecular viscosity or magnetic drag acts non-uniformly across latitude or a poloidal magnetic field is present, suggesting that these effects will introduce qualitative changes to the familiar chevron-shaped feature witnessed in simulations of atmospheric circulation. We also find that hydrodynamic and magnetic sources of friction have dissimilar phase signatures and affect the flow in fundamentally different ways, implying that using Rayleigh drag to mimic magnetic drag is inaccurate. We exhaustively lay down the theoretical formalism (dispersion relations, governing equations, and time-dependent wave solutions) for a broad suite of models. In all situations, we derive the steady state of an atmosphere, which is relevant to interpreting infrared phase and eclipse maps of exoplanetary atmospheres. We elucidate a pinching effect that confines the atmospheric structure to be near the equator. Our suite of analytical models may be used to develop decisively physical intuition and as a reference point for three-dimensional magnetohydrodynamic simulations of atmospheric circulation.

  6. Thermochemistry of substellar atmospheres: Water, oxygen, sulfur, and phosphorus

    NASA Astrophysics Data System (ADS)

    Visscher, Channon Wayne

    2006-09-01

    Thermochemical equilibrium and kinetic calculations are used to investigate atmospheric chemistry in substellar objects: giant planets, extrasolar giant planets (EGPs), and brown dwarfs. These studies include an assessment of the water and total oxygen inventories in the interiors of Jupiter and Saturn, and detailed modeling of sulfur and phosphorus chemistry in the atmospheres of substellar objects. In the first part of the dissertation, the water and total oxygen abundances in the deep atmospheres of Jupiter and Saturn are determined by considering the effects of H 2 O and O on the chemistry of CO, PH 3 , and SiH 4 . On Jupiter, the observed CO abundance indicates a water abundance of 0.4--1.4 times the protosolar H 2 O/H 2 ratio (8.96 × 10 -4 ). On Saturn, a combination of CO and PH 3 chemical constraints requires a water abundance of 1.9--6.1 times the protosolar abundance. Combining these results with Si mass balance considerations gives a total oxygen abundance of 0.7--1.7 and 3.2--6.4 times the protosolar O/H 2 ratio (1.16 × 10 -3 ) on Jupiter and Saturn, respectively. In both planets, oxygen is less enriched than other heavy elements (such as carbon) relative to hydrogen and the solar system composition. These results provide important constraints for giant planet formation mechanisms and models of tropospheric chemistry. The second part of the dissertation is a detailed study of sulfur and phosphorus chemistry in substellar atmospheres. The chemical behavior of individual S- and P-bearing gases and condensates is determined as a function of temperature, total pressure, and metallicity. Aside from minor amounts of sulfur removed by metal sulfide cloud formation, H 2 S is approximately representative of the sulfur inventory throughout substellar atmospheres. Silicon sulfide (SiS) is a potential tracer of weather in EGPs and L dwarfs. Phosphorus chemistry is considerably more complex than that of sulfur. Disequilibrium abundances of PH 3 approximately

  7. Clouds and climate: Ability of atmospheric particles to uptake water

    NASA Astrophysics Data System (ADS)

    Farnham, Gabriella Joy Engelhart

    Atmospheric aerosols have significant impacts on human health, visibility and climate. Their interactions with water alter deposition within the human respiratory system, change particle optical properties, and change cloud microphysics by serving as cloud condensation nuclei (CCN). These clouds have a considerable influence on climate by reflecting incoming solar radiation, which provides a negative forcing, or cooling effect on earth's climate due to increased reflectivity. Our current understanding of the interactions of aerosols with clouds and climate is limited; the parameterizations needed for modeling predictions of climate can be aided by constraints from laboratory and in-situ experiments. Much of the uncertainty regarding the water uptake by atmospheric particles resides in organic aerosols. This thesis utilizes smog chamber techniques to study the CCN activity of biogenic secondary organic aerosol (SOA) including isoprene, monoterpene and sesquiterpene precursors. Particular emphasis is placed on comparison to Kohler theory, surface tension, solubility, droplet growth kinetics and volatility. The work also studies the CCN activity of a less controlled mixture of primary aerosol from biomass burning and the potential for transformation in the atmosphere via oxidation. Finally, this dissertation utilizes a dry-ambient aerosol size spectrometer (DAASS) to study the water content of aged atmospheric particles in a remote environment. We find monoterpene and isoprene SOA serve as good CCN. The water soluble component of sesquiterpene SOA has similar properties to those observed for monoterpene SOA meaning that a predictive understanding of SOA CCN may require knowledge of the water soluble fraction, but not its exact speciation. Sesquiterpene SOA CCN activity is particularly sensitive to temperature, suggesting that the CCN active fraction of the SOA is semi-volatile. Biomass burning experiments reveal that the CCN characteristics of primary aerosols

  8. Hurricane Isabel, Amount of Atmospheric Water Vapor Observed By AIRS

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site] Figure 1

    These false-color images show the amount of atmospheric water vapor observed by AIRS two weeks prior to the passage of Hurricane Isabel, and then when it was a Category 5 storm. The region shown includes parts of South America and the West Indies. Puerto Rico is the large island below the upper left corner.

    Total water vapor represents the depth of a layer if all the water vapor in the atmosphere were to condense and fall to the surface. The color bar on the right sides of the plots give the thickness of this layer in millimeters (mm). The first image, from August 28, shows typical tropical water vapor amounts over the ocean: between roughly 25 and 50 mm, or 1 to 2 inches. The highest values of roughly 80 mm, seen as a red blob over South America, corresponds to intense thunderstorms. Thunderstorms pull in water vapor from surrounding regions and concentrate it, with much of it then falling as rain.

    Figure 1 shows total water during the passage of Hurricane Isabel on September 13. The storm is apparent: the ring of moderate values surrounding a very strong maximum of 100 mm. Total water of more than 80 mm is unusual, and these values correspond to the intense thunderstorms contained within Isabel. The thunderstorms--and the large values of total water--are fed by evaporation from the ocean in the hurricane's high winds. The water vapor near the center of the storm does not remain there long, since hurricane rain rates as high 50 mm (2 inches) per hour imply rapid cycling of the water we observe. Away from the storm the amount of total water vapor is rather low, associated with fair weather where air that ascended near the storm's eye returns to earth, having dropped its moisture as rain. Also seen in the second images are two small regions of about 70 mm of total water over south America. These are yet more thunderstorms, though likely much more benign than those in Isabel.

    The

  9. Column atmospheric water vapor and vegetation liquid water retrievals from airborne imaging spectrometer data

    SciTech Connect

    Bo-Cai Gao; Goetz, A.F.H. )

    1990-03-20

    High spatial resolution column atmospheric water vapor amounts were derived from spectral data collected by the airborne visible-infrared imaging spectrometer (AVIRIS). The quantitative derivation is made by curve fitting observed spectra with calculated spectra in the 1.14-{mu}m and 0.94-{mu}m water vapor band absorption regions using an atmospheric model, a narrow-band spectral model, and a nonlinear least squares fitting technique. The derivation makes use of the facts that (1) the reflectances of many ground targets vary approximately linearly with wavelength in the 0.94- and 1.14-{mu}m water vapor band absorption regions, (2) the scattered radiation near 1 {mu}m is small compared with the directly reflected radiation when the atmospheric aerosol concentrations are low, and (3) the scattered radiation in the lower part of the atmosphere is subjected to the water vapor absorption. Based on the analyses of an AVIRIS data set that was acquired within an hour of radiosonde launch, it appears that the accuracy approaches the precision. The derived column water vapor amounts are independent of the absolute surface reflectances. It now appears feasible to derive high spatial resolution column water vapor amounts over land areas from satellite altitude with the proposed high resolution imaging spectrometer (HIRIS). Curve fitting of spectra near 1 {mu}m from areas covered with vegetation, using an atmospheric model and a simplified vegetation reflectance model, indicates that both the amount of atmospheric water vapor and the moisture content of vegetation can be retrieved simultaneously because the band centers of liquid water in vegetation and the atmospheric water vapor are offset by approximately 0.05 {mu}m.

  10. NLTE water lines in Betelgeuse-like atmospheres

    NASA Astrophysics Data System (ADS)

    Lambert, J.; Josselin, E.; Ryde, N.; Faure, A.

    2013-05-01

    The interpretation of water lines in red supergiant stellar atmospheres has been much debated over the past decade. The introduction of the so-called MOLspheres to account for near-infrared "extra" absorption has been controversial. We propose that non-LTE effects should be taken into account before considering any extra-photospheric contribution. After a brief introduction on the radiative transfer treatment and the inadequacy of classical treatments in the case of large-scale systems such as molecules, we present a new code, based on preconditioned Krylov subspace methods. Preliminary results suggest that NLTE effects lead to deeper water bands, as well as extra cooling.

  11. Water inventories on Earth and Mars: Clues to atmosphere formation

    NASA Technical Reports Server (NTRS)

    Carr, M. H.

    1992-01-01

    Water is distributed differently on Earth and on Mars and the differences may have implications for the accretion of the two planets and the formation of their atmospheres. The Earth's mantle appears to contain at least several times the water content of the Martian mantle even accounting for differences in plate tectonics. One explanation is that the Earth's surface melted during accretion, as a result of development of a steam atmosphere, thereby allowing impact-devolitalized water at the surface to dissolve into the Earth's interior. In contrast, because of Mars' smaller size and greater distance from the Sun, the Martian surface may not have melted, so that the devolatilized water could not dissolve into the surface. A second possibility is suggested by the siderophile elements in the Earth's mantle, which indicates the Earth acquired a volatile-rich veneer after the core formed. Mars may have acquired a late volatile-rich veneer, but it did not get folded into the interior as with the Earth, but instead remained as a water rich veneer. This perception of Mars with a wet surface but dry interior is consistent with our knowledge of Mars' geologic history.

  12. Proposed reference model for middle atmosphere water vapor

    NASA Astrophysics Data System (ADS)

    Chiou, E. W.; Remsberg, E. E.; Rodgers, C. D.; Munro, R.; Bevilacqua, R. M.; McCormick, M. P.; Russell, J. M.

    Several new and significant satellite data sets on middle atmosphere water vapor have been produced recently. They include data from the Stratospheric Aerosol and Gas Experiment II (SAGE II) and the Nimbus-7 Stratospheric and Mesospheric Sounder (SAMS) experiment. The SAGE II data provide an estimate of interannual variability of water vapor in the stratosphere. The SAMS data are appropriate for the upper stratosphere and lower mesosphere. We combine these two data sets with those from the Nimbus-7 Limb Infrared Monitor of the Stratosphere (LIMS) experiment to update the COSPAR interim reference model for water vapor. Water vapor profiles from the Spacelab 3 Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment, ground-based microwave, and in situ balloon and aircraft measurements have been used to check the quality of the satellite data sets. The updated reference model is given as a function of latitude and pressure altitude and now covers all four seasons. Tabulations are included for these seasonal water vapor mixing ratios (in ppmv) and their estimated errors (in percent).

  13. Water and acid soluble trace metals in atmospheric particles

    NASA Technical Reports Server (NTRS)

    Lindberg, S. E.; Harriss, R. C.

    1983-01-01

    Continental aerosols are collected above a deciduous forest in eastern Tennessee and subjected to selective extractions to determine the water-soluble and acid-leachable concentrations of Cd, Mn, Pb, and Zn. The combined contributions of these metals to the total aerosol mass is 0.5 percent, with approximately 70 percent of this attributable to Pb alone. A substantial fraction (approximately 50 percent or more) of the acid-leachable metals is soluble in distilled water. In general, this water-soluble fraction increases with decreasing particle size and with increasing frequency of atmospheric water vapor saturation during the sampling period. The pattern of relative solubilities (Zn being greater than Mn, which is approximately equal to Cd, which is greater than Pb) is found to be similar to the general order of the thermodynamic solubilities of the most probable salts of these elements in continental aerosols with mixed fossil fuel and soil sources.

  14. Atmospheric cloud water contains a diverse bacterial community

    SciTech Connect

    Kourtev, P. S.; Hill, Kimberly A.; Shepson, Paul B.; Konopka, Allan

    2011-06-15

    Atmospheric cloud water contains an active microbial community which can impact climate, human health and ecosystem processes in terrestrial and aquatic systems. Most studies on the composition of microbial communities in clouds have been performed with orographic clouds that are typically in direct contact with the ground. We collected water samples from cumulus clouds above the upper U.S. Midwest. The cloud water was analyzed for the diversity of bacterial phylotypes by denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S rRNA gene amplicons. DGGE analyses of bacterial communities detected 17e21 bands per sample. Sequencing confirmed the presence of a diverse bacterial community; sequences from seven bacterial phyla were retrieved. Cloud water bacterial communities appeared to be dominated by members of the cyanobacteria, proteobacteria, actinobacteria and firmicutes.

  15. Venus: new microwave measurements show no atmospheric water vapor.

    PubMed

    Janssen, M A; Hills, R E; Thornton, D D; Welch, W J

    1973-03-01

    Two sets of passive radio observations of Venus-measurements of the spectrum of the disk temperature near the 1-centimeter wavelength, and interferometric measurements of the planetary limb darkening at the 1.35-centimeter water vapor resonance-show no evidence of water vapor in the lower atmosphere of Venus. The upper limit of 2 x 10(-3) for the mixing ratio of water vapor is substantially less than the amounts derived from the Venera space probes (0.5 x 10(-2) to 2.5 x 10(-2)). This amount of water vapor cannot produce dense clouds, and it is doubtful that it may contribute significantly to a greenhouse effect. PMID:17842164

  16. Thermal shallow water models of geostrophic turbulence in Jovian atmospheres

    SciTech Connect

    Warneford, Emma S. Dellar, Paul J.

    2014-01-15

    Conventional shallow water theory successfully reproduces many key features of the Jovian atmosphere: a mixture of coherent vortices and stable, large-scale, zonal jets whose amplitude decreases with distance from the equator. However, both freely decaying and forced-dissipative simulations of the shallow water equations in Jovian parameter regimes invariably yield retrograde equatorial jets, while Jupiter itself has a strong prograde equatorial jet. Simulations by Scott and Polvani [“Equatorial superrotation in shallow atmospheres,” Geophys. Res. Lett. 35, L24202 (2008)] have produced prograde equatorial jets through the addition of a model for radiative relaxation in the shallow water height equation. However, their model does not conserve mass or momentum in the active layer, and produces mid-latitude jets much weaker than the equatorial jet. We present the thermal shallow water equations as an alternative model for Jovian atmospheres. These equations permit horizontal variations in the thermodynamic properties of the fluid within the active layer. We incorporate a radiative relaxation term in the separate temperature equation, leaving the mass and momentum conservation equations untouched. Simulations of this model in the Jovian regime yield a strong prograde equatorial jet, and larger amplitude mid-latitude jets than the Scott and Polvani model. For both models, the slope of the non-zonal energy spectra is consistent with the classic Kolmogorov scaling, and the slope of the zonal energy spectra is consistent with the much steeper spectrum observed for Jupiter. We also perform simulations of the thermal shallow water equations for Neptunian parameter values, with a radiative relaxation time scale calculated for the same 25 mbar pressure level we used for Jupiter. These Neptunian simulations reproduce the broad, retrograde equatorial jet and prograde mid-latitude jets seen in observations. The much longer radiative time scale for the colder planet Neptune

  17. Natural chlorine and fluorine in the atmosphere, water and precipitation

    NASA Technical Reports Server (NTRS)

    Friend, James P.

    1990-01-01

    The geochemical cycles of chlorine and fluorine are surveyed and summarized as framework for the understanding of the global natural abundances of these species in the atmosphere, water, and precipitation. In the cycles the fluxes into and out of the atmosphere can be balanced within the limits of our knowledge of the natural sources and sinks. Sea salt from the ocean surfaces represent the predominant portion of the source of chlorine. It is also an important source of atmospheric fluorine, but volcanoes are likely to be more important fluorine sources. Dry deposition of sea salt returns about 85 percent of the salt released there. Precipitation removes the remainder. Most of the sea salt materials are considered to be cyclic, moving through sea spray over the oceans and either directly back to the oceans or deposited dry and in precipitation on land, whence it runs off into rivers and streams and returns to the oceans. Most of the natural chlorine in the atmosphere is in the form of particulate chloride ion with lesser amounts as gaseous inorganic chloride and methyl chloride vapor. Fluorine is emitted from volcanoes primarily as HF. It is possible that HF may be released directly form the ocean surface but this has not been confirmed by observation. HCl and most likely HF gases are released into the atmosphere by sea salt aerosols. The mechanism for the release is likely to be the provision of protons from the so-called excess sulfate and HNO3. Sea salt aerosol contains fluorine as F(-), MgF(+), CaF(+), and NaF. The concentrations of the various species of chlorine and fluorine that characterize primarily natural, unpolluted atmospheres are summarized in tables and are discussed in relation to their fluxes through the geochemical cycle.

  18. The seasonal and global behavior of water vapor in the Mars atmosphere - Complete global results of the Viking atmospheric water detector experiment

    NASA Technical Reports Server (NTRS)

    Jakosky, B. M.; Farmer, C. B.

    1982-01-01

    A key question regarding the evolution of Mars is related to the behavior of its volatiles. The present investigation is concerned with the global and seasonal abundances of water vapor in the Mars atmosphere as mapped by the Viking Mars Atmospheric Water Detector (MAWD) instrument for almost 1-1/2 Martian years from June 1976 to April 1979. Attention is given to the implications of the observed variations for determining the relative importance of those processes which may be controlling the vapor cycle on a seasonal basis. The processes considered include buffering of the atmosphere water by a surface or subsurface reservior of ground ice, physically adsorbed water, or chemically bound water. Other processes are related to the supply of water from the residual or seasonal north polar ice cap, the redistribution of the vapor resulting from atmospheric circulation, and control of the vapor holding capacity of the atmosphere by the local atmospheric temperatures.

  19. Formation of Organic Molecules and Water in Warm Disk Atmospheres

    NASA Astrophysics Data System (ADS)

    Najita, Joan R.; Ádámkovics, Máté; Glassgold, Alfred E.

    2011-12-01

    Observations from Spitzer and ground-based infrared spectroscopy reveal significant diversity in the molecular emission from the inner few AU of T Tauri disks. We explore theoretically the possible origin of this diversity by expanding on our earlier thermal-chemical model of disk atmospheres. We consider how variations in grain settling, X-ray irradiation, accretion-related mechanical heating, and the oxygen-to-carbon ratio can affect the thermal and chemical properties of the atmosphere at 0.25-40 AU. We find that these model parameters can account for many properties of the detected molecular emission. The column density of the warm (200-2000 K) molecular atmosphere is sensitive to grain settling and the efficiency of accretion-related heating, which may account, at least in part, for the large range in molecular emission fluxes that have been observed. The dependence of the atmospheric properties on the model parameters may also help to explain trends that have been reported in the literature between molecular emission strength and mid-infrared color, stellar accretion rate, and disk mass. We discuss whether some of the differences between our model results and the observations (e.g., for water) indicate a role for vertical transport and freezeout in the disk midplane. We also discuss how planetesimal formation in the outer disk (beyond the snowline) may imprint a chemical signature on the inner few AU of the disk and speculate on possible observational tracers of this process.

  20. Aqueous-Phase Photochemical Production of Oxidants in Atmospheric Waters.

    NASA Astrophysics Data System (ADS)

    Allen, John Morrison

    1992-01-01

    The photochemical formation and subsequent reactions of oxidants plays an important role in the overall chemistry of the atmosphere. Much of the interest in atmospheric oxidation reactions has been fueled by the environmental consequences of the oxidation of sulfur dioxide (SO _2) forming sulfuric acid (H_2 SO_4). Oxidation reactions also play a crucial role in other atmospheric chemical transformations such as: (1) the destruction of tropospheric ozone, (2) redox cycling of transition metals, and (3) oxidation of organic compounds. Much of the research pertaining to atmospheric oxidant formation and the reactions that these oxidants undergo has centered upon gas-phase photochemical oxidant formation and: (1) subsequent reactions in the gas phase, or (2) partitioning of oxidants into cloud and fog drops and subsequent reactions in the aqueous phase. Only a very limited amount of data is available concerning aqueous -phase photochemical sources of oxidants in cloud and fog drops. The focus of one aspect of the work presented in this dissertation is upon the aqueous-phase sunlight photochemical formation of oxidants in authentic cloud and fog water samples from across the United States and Canada. It will be demonstrated that atmospheric waters typically absorb solar ultraviolet radiation at wavelengths ranging from 290 to 340 nm. This absorption is due to the presence of chemical constituents in the cloud and fog waters that contain chromophoric functional groups that give rise to the formation of: (1) singlet molecular oxygen O_2(^1Delta_ {rm g}), (2) peroxyl radicals (HO _2cdot and RO_2 cdot), (3) peroxides (HOOH, ROOH, and ROOR '), and (4) hydroxyl radical ( cdotOH). This work will demonstrate that aqueous-phase photochemical reactions are a significant and in some cases dominant source of these oxidants in cloud and fog drops. The transition metal catalyzed oxidation of SO _2 to H_2SO _4 by molecular oxygen has been extensively studied. This reaction is thought

  1. Atmosphere and water quality monitoring on Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Niu, William

    1990-01-01

    In Space Station Freedom air and water will be supplied in closed loop systems. The monitoring of air and water qualities will ensure the crew health for the long mission duration. The Atmosphere Composition Monitor consists of the following major instruments: (1) a single focusing mass spectrometer to monitor major air constituents and control the oxygen/nitrogen addition for the Space Station; (2) a gas chromatograph/mass spectrometer to detect trace contaminants; (3) a non-dispersive infrared spectrometer to determine carbon monoxide concentration; and (4) a laser particle counter for measuring particulates in the air. An overview of the design and development concepts for the air and water quality monitors is presented.

  2. Effects of the atmosphere on the detection of surface changes from Landsat multispectral scanner data

    USGS Publications Warehouse

    Otterman, Joseph; Robinove, Charles J.

    1981-01-01

    These effects on the monitoring of surface changes by the use of Landsat MSS data are discussed in terms of departures of the actual atmosphere at the time of a satellite passage from a ‘minima’ atmosphere having no aerosols and characterized by gaseous absorption corresponding to minimal water vapour amounts.

  3. Riparian ecohydrology: regulation of water flux from the ground to the atmosphere in the Middle Rio Grande, New Mexico

    NASA Astrophysics Data System (ADS)

    Cleverly, James R.; Dahm, Clifford N.; Thibault, James R.; McDonnell, Dianne E.; Allred Coonrod, Julie E.

    2006-10-01

    During the previous decade, the south-western United States has faced declining water resources and escalating forest fires due to long-term regional drought. Competing demands for water resources require a careful accounting of the basin water budget. Water lost to the atmosphere through riparian evapotranspiration (ET) is believed to rank in the top third of water budget depletions. To better manage depletions in a large river system, patterns of riparian ET must be better understood. This paper provides a general overview of the ecological, hydrological, and atmospheric issues surrounding riparian ET in the Middle Rio Grande (MRG) of New Mexico. Long-term measurements of ET, water table depth, and micro-meteorological conditions have been made at sites dominated by native cottonwood (Populus deltoides) forests and non-native saltcedar (Tamarix chinensis) thickets along the MRG. Over periods longer than one week, groundwater and leaf area index (LAI) dynamics relate well with ET rates. Evapotranspiration from P. deltoides forests was unaffected by annual drought conditions in much of the MRG where the water table is maintained within 3 m of the surface. Evapotranspiration from a dense Tamarix chinensis thicket did not decline with increasing groundwater depth; instead, ET increased by 50%, from 6 mm/day to 9 mm/day, as the water table receded at nearly 7 cm/day. Leaf area index of the T. chinensis thicket, likewise, increased during groundwater decline. Leaf area index can be manipulated as well following removal of non-native species. When T. chinensis and non-native Russian olive (Elaeagnus angustifolia) were removed from a P. deltoides understory, water salvaged through reduced ET was 26 cm/yr in relation to ET measured at reference sites. To investigate correlates to short-term variations in ET, stepwise multiple linear regression was used to evaluate atmospheric conditions under which ET is elevated or depressed. At the P. deltoides-dominated sites, ET

  4. Martian atmospheric chemistry during the time of low water abundance

    NASA Technical Reports Server (NTRS)

    Nair, Hari; Allen, Mark; Yung, Yuk L.; Clancy, R. Todd

    1992-01-01

    The importance of odd hydrogen (or HO(x)) radicals in the catalytic recombination of carbon monoxide and oxygen in the Martian atmosphere is a well known fact. The inclusion of recent chemical kinetics data, specifically temperature-dependent CO2 absorption cross sections, into our one dimensional photochemical model shows that HO(x) is too efficient in this regard. The absorption cross sections of CO2 are smaller than previously assumed; this leads to a reduction in the photolysis rate of CO2 while the photolysis rate of H2O has increased. As a consequence the predicted mixing ratio of CO in our models is substantially less than the observed value of 6.5(10)(exp -4). Simultaneous measurements of water, ozone, and carbon monoxide were obtained in the Martian atmosphere in early Dec. 1990 (L(sub s) for Mars was 344 deg.).

  5. Solar geoengineering, atmospheric water vapor transport, and land plants

    NASA Astrophysics Data System (ADS)

    Caldeira, Ken; Cao, Long

    2015-04-01

    This work, using the GeoMIP database supplemented by additional simulations, discusses how solar geoengineering, as projected by the climate models, affects temperature and the hydrological cycle, and how this in turn is related to projected changes in net primary productivity (NPP). Solar geoengineering simulations typically exhibit reduced precipitation. Solar geoengineering reduces precipitation because solar geoengineering reduces evaporation. Evaporation precedes precipitation, and, globally, evaporation equals precipitation. CO2 tends to reduce evaporation through two main mechanisms: (1) CO2 tends to stabilize the atmosphere especially over the ocean, leading to a moister atmospheric boundary layer over the ocean. This moistening of the boundary layer suppresses evaporation. (2) CO2 tends to diminish evapotranspiration, at least in most land-surface models, because higher atmospheric CO2 concentrations allow leaves to close their stomata and avoid water loss. In most high-CO2 simulations, these effects of CO2 which tend to suppress evaporation are masked by the tendency of CO2-warming effect to increase evaporation. In a geoengineering simulation, with the warming effect of CO2 largely offset by the solar geoengineering, the evaporation suppressing characteristics of CO2 are no longer masked and are clearly exhibited. Decreased precipitation in solar geoengineering simulations is a bit like ocean acidification - an effect of high CO2 concentrations that is not offset by solar geoengineering. Locally, precipitation ultimately either evaporates (much of that through the leaves of plants) or runs off through groundwater to streams and rivers. On long time scales, runoff equals precipitation minus evaporation, and thus, water runoff generated at a location is equal to the net atmospheric transport of water to that location. Runoff typically occurs where there is substantial soil moisture, at least seasonally. Locations where there is enough water to maintain

  6. Rapid and long-term effects of water deficit on gas exchange and hydraulic conductance of silver birch trees grown under varying atmospheric humidity

    PubMed Central

    2014-01-01

    Background Effects of water deficit on plant water status, gas exchange and hydraulic conductance were investigated in Betula pendula under artificially manipulated air humidity in Eastern Estonia. The study was aimed to broaden an understanding of the ability of trees to acclimate with the increasing atmospheric humidity predicted for northern Europe. Rapidly-induced water deficit was imposed by dehydrating cut branches in open-air conditions; long-term water deficit was generated by seasonal drought. Results The rapid water deficit quantified by leaf (ΨL) and branch water potentials (ΨB) had a significant (P < 0.001) effect on gas exchange parameters, while inclusion of ΨB in models resulted in a considerably better fit than those including ΨL, which supports the idea that stomatal openness is regulated to prevent stem rather than leaf xylem dysfunction. Under moderate water deficit (ΨL≥-1.55 MPa), leaf conductance to water vapour (gL), transpiration rate and leaf hydraulic conductance (KL) were higher (P < 0.05) and leaf temperature lower in trees grown in elevated air humidity (H treatment) than in control trees (C treatment). Under severe water deficit (ΨL<-1.55 MPa), the treatments showed no difference. The humidification manipulation influenced most of the studied characteristics, while the effect was to a great extent realized through changes in soil water availability, i.e. due to higher soil water potential in H treatment. Two functional characteristics (gL, KL) exhibited higher (P < 0.05) sensitivity to water deficit in trees grown under increased air humidity. Conclusions The experiment supported the hypothesis that physiological traits in trees acclimated to higher air humidity exhibit higher sensitivity to rapid water deficit with respect to two characteristics - leaf conductance to water vapour and leaf hydraulic conductance. Disproportionate changes in sensitivity of stomatal versus leaf hydraulic conductance to water deficit

  7. Improved Atmospheric Correction for AVIRIS Spectra from Inland Waters

    NASA Technical Reports Server (NTRS)

    Gastil, Mary; Melack, John M.

    1998-01-01

    Remote sensing reflectance (Rrs) cannot be measured directly. Comparison of Rrs calculated from field measurements to Rrs calculated from AVIRIS spectra and the atmospheric radiative transfer model modtran provides a measure of the accuracy of our method. That and other comparisons are presented here as a validation of a method of retrieving Rrs from inland waters from AVIRIS radiance. The method of collecting field measurements for Rrs is described in Hamilton, 1993. Retrieval of Rrs from AVIRIS using modtran was developed from Carder, 1993. AVIRIS radiance is reduced by the path radiance modeled by modtran and divided by one-way transmission. Skylight, modeled by modtran, specularly reflected from the lake surface, is then subtracted from this radiance, leaving only that radiance which has come from under water. This water-leaving radiance is then normalized by the downwelling irradiance incident at the surface as modeled by modtran. Our improved retrieval of Rrs has allowed us to fit a single curve to a set of 134 pairs of AVIRIS Rrs and measured chlorophyll gathered on eight experiments at Mono Lake. Previously, spectra from different surveys varied more due to lingering atmospheric effects and/or radiometric calibration imprecision than they varied due to chlorophyll.

  8. Linking Hydrology and Atmospheric Sciences in Continental Water Dynamics Modeling

    NASA Astrophysics Data System (ADS)

    David, C. H.; Gochis, D. J.; Maidment, D. R.; Wilhelmi, O.

    2006-12-01

    Atmospheric observation and model output datasets as well as hydrologic datasets are increasingly becoming available on a continental scale. Although the availability of these datasets could allow large-scale water dynamics modeling, the different objects and semantics used in atmospheric science and hydrology set barriers to their interoperability. Recent work has demonstrated the feasibility for modeling terrestrial water dynamics for the continental United States of America. Continental water dynamics defines the interaction of the hydrosphere, the land surface and subsurface at spatial scales ranging from point to continent. The improved version of the National Hydrographic Dataset (NHDPlus, an integrated suite of geospatial datasets stored in a vector and raster GIS format) was used as hydrologic and elevation data input to the Noah community Land Surface Model, developed at NCAR. Noah was successfully run on a watershed in the Ohio River Basin with NHDPlus inputs. The use of NHDPlus as input data for Noah is a crucial improvement for community modeling efforts allowing users to by-pass much of the time consumed in Digital Elevation Model and hydrological network processing. Furthermore, the community Noah land surface model, in its hydrologically-enhanced configuration, is capable of providing flow inputs for a river dynamics model. Continued enhancement of Noah will, as a consequence, be beneficial to the atmospheric science community as well as to the hydrologic community. Ongoing research foci include using a diversity of weather drivers as an input to Noah, and investigation of how to use land surface model outputs for river forecasting, using both the ArcHydro and OpenMI frameworks.

  9. Water vapor measurement system in global atmospheric sampling program, appendix

    NASA Technical Reports Server (NTRS)

    Englund, D. R.; Dudzinski, T. J.

    1982-01-01

    The water vapor measurement system used in the NASA Global Atmospheric Sampling Program (GASP) is described. The system used a modified version of a commercially available dew/frostpoint hygrometer with a thermoelectrically cooled mirror sensor. The modifications extended the range of the hygrometer to enable air sample measurements with frostpoint temperatures down to -80 C at altitudes of 6 to 13 km. Other modifications were made to permit automatic, unattended operation in an aircraft environment. This report described the hygrometer, its integration with the GASP system, its calibration, and operational aspects including measurement errors. The estimated uncertainty of the dew/frostpoint measurements was + or - 1.7 Celsius.

  10. Semivolatile organic compounds in urban and over-water atmospheres

    NASA Astrophysics Data System (ADS)

    Offenberg, John H., Jr.

    Concentrations of semi-volatile organic contaminants were measured both in air and precipitation in and downwind of Chicago, IL and Baltimore, MD as part of the A_tmospheric E_xchange O_ver L_akes and O_ceans_ (AEOLOS) project. Precipitation events were collected simultaneously in the city and over the water to measure increased wet depositional fluxes of polychlorinated biphenyls to Lake Michigan during May and July 1994 and January 1995. Elevated atmospheric concentrations in Chicago, IL increase atmospheric loadings of PCBs to Lake Michigan by at least a factor of two over regional background levels. Precipitation loadings, bidirectional gas exchange and dry deposition combine to increase measured surface water concentrations of PCBs in Lake Michigan during periods of southwesterly winds which transport the urban air mass across the lake. PCB concentrations in surface waters were higher during winter than in spring or summer, but PAH concentrations did not vary significantly with season. However, when placed in historical context, Lake Michigan PCB concentrations have declined ten fold over fourteen years from 1980 to 1994. Size segregated airborne particulate samples collected around and over southern Lake Michigan show geometric mean diameters of polycyclic aromatic hydrocarbons that are correlated with the compound's sub-cooled liquid vapor pressures. More volatile compounds were found on larger particles. The slope of the relationship between GMD and vapor pressure depends on the transit time from the shoreline, suggesting that higher wind speeds induce faster dry deposition of large particles. Measured gas/particle partitioning of these compounds is modeled according to a three dimensional multiple linear regression that includes the influences of vapor pressure, particle size and measured aerosol fractional organic carbon content. Each of these terms is significant in the full model but, addition of the latter two terms appears to be practically

  11. Importance of Rain Evaporation and Continental Convection in the Tropical Water Cycle

    NASA Technical Reports Server (NTRS)

    Worden, John; Noone, David; Bowman, Kevin; Beer, R.; Eldering, A.; Fisher, B.; Gunson, M.; Goldman, Aaron; Kulawik, S. S.; Lampel, Michael; Osterman, Gregory; Rinsland, Curtis P.; Rogders, Clive; Sander, Stanley; Shepard, Mark; Webster, Christopher R.; Worden, H. M.

    2007-01-01

    Atmospheric moisture cycling is an important aspect of the Earth's climate system, yet the processes determining atmospheric humidity are poorly understood. For example, direct evaporation of rain contributes significantly to the heat and moisture budgets of clouds, but few observations of these processes are available. Similarly, the relative contributions to atmospheric moisture over land from local evaporation and humidity from oceanic sources are uncertain. Lighter isotopes of water vapour preferentially evaporate whereas heavier isotopes preferentially condense and the isotopic composition of ocean water is known. Here we use this information combined with global measurements of the isotopic composition of tropospheric water vapour from the Tropospheric Emission Spectrometer (TES) aboard the Aura spacecraft, to investigate aspects of the atmospheric hydrological cycle that are not well constrained by observations of precipitation or atmospheric vapour content. Our measurements of the isotopic composition of water vapour near tropical clouds suggest that rainfall evaporation contributes significantly to lower troposphere humidity, with typically 20% and up to 50% of rainfall evaporating near convective clouds. Over the tropical continents the isotopic signature of tropospheric water vapour differs significantly from that of precipitation, suggesting that convection of vapour from both oceanic sources and evapotranspiration are the dominant moisture sources. Our measurements allow an assessment of the intensity of the present hydrological cycle and will help identify any future changes as they occur.

  12. Atmospheric Photochemistry

    NASA Technical Reports Server (NTRS)

    Massey, Harrie; Potter, A. E.

    1961-01-01

    The upper atmosphere offers a vast photochemical laboratory free from solid surfaces, so all reactions take place in the gaseous phase. At 30 km altitude the pressure has fallen to about one-hundredth of that at ground level, and we shall, rather arbitrarily, regard the upper atmosphere as beginning at that height. By a little less than 100 km the pressure has fallen to 10(exp -3) mm Hg and is decreasing by a power of ten for every 15 km increase in altitude. Essentially we are concerned then with the photochemistry of a nitrogen-oxygen mixture under low-pressure conditions in which photo-ionization, as well as photodissociation, plays an important part. Account must also be taken of the presence of rare constituents, such as water vapour and its decomposition products, including particularly hydroxyl, oxides of carbon, methane and, strangely enough, sodium, lithium and calcium. Many curious and unfamiliar reactions occur in the upper atmosphere. Some of them are luminescent, causing the atmosphere to emit a dim light called the airglow. Others, between gaseous ions and neutral molecules, are almost a complete mystery at this time. Similar interesting phenomena must occur in other planetary atmospheres, and they might be predicted if sufficient chemical information were available.

  13. Habitability of waterworlds: runaway greenhouses, atmospheric expansion, and multiple climate states of pure water atmospheres.

    PubMed

    Goldblatt, Colin

    2015-05-01

    There are four different stable climate states for pure water atmospheres, as might exist on so-called "waterworlds." I map these as a function of solar constant for planets ranging in size from Mars-sized to 10 Earth-mass. The states are as follows: globally ice covered (Ts ⪅ 245 K), cold and damp (270 ⪅ Ts ⪅ 290 K), hot and moist (350 ⪅ Ts ⪅ 550 K), and very hot and dry (Tsx2A86;900 K). No stable climate exists for 290 ⪅ T s ⪅ 350 K or 550 ⪅ Ts ⪅ 900 K. The union of hot moist and cold damp climates describes the liquid water habitable zone, the width and location of which depends on planet mass. At each solar constant, two or three different climate states are stable. This is a consequence of strong nonlinearities in both thermal emission and the net absorption of sunlight. Across the range of planet sizes, I account for the atmospheres expanding to high altitudes as they warm. The emitting and absorbing surfaces (optical depth of unity) move to high altitude, making their area larger than the planet surface, so more thermal radiation is emitted and more sunlight absorbed (the former dominates). The atmospheres of small planets expand more due to weaker gravity; the effective runaway greenhouse threshold is about 35 W m(-2) higher for Mars, 10 W m(-2) higher for Earth or Venus, but only a few W m(-2) higher for a 10 Earth-mass planet. There is an underlying (expansion-neglected) trend of increasing runaway greenhouse threshold with planetary size (40 W m(-2) higher for a 10 Earth-mass planet than for Mars). Summing these opposing trends means that Venus-sized (or slightly smaller) planets are most susceptible to a runaway greenhouse. The habitable zone for pure water atmospheres is very narrow, with an insolation range of 0.07 times the solar constant. A wider habitable zone requires background gas and greenhouse gas: N2 and CO2 on Earth, which are biologically controlled. Thus, habitability depends on inhabitance. PMID:25984919

  14. Habitability of Waterworlds: Runaway Greenhouses, Atmospheric Expansion, and Multiple Climate States of Pure Water Atmospheres

    PubMed Central

    2015-01-01

    Abstract There are four different stable climate states for pure water atmospheres, as might exist on so-called “waterworlds.” I map these as a function of solar constant for planets ranging in size from Mars-sized to 10 Earth-mass. The states are as follows: globally ice covered (Ts⪅245 K), cold and damp (270⪅Ts⪅290 K), hot and moist (350⪅Ts⪅550 K), and very hot and dry (Tsx2A86;900 K). No stable climate exists for 290⪅Ts ⪅350 K or 550⪅Ts⪅900 K. The union of hot moist and cold damp climates describes the liquid water habitable zone, the width and location of which depends on planet mass. At each solar constant, two or three different climate states are stable. This is a consequence of strong nonlinearities in both thermal emission and the net absorption of sunlight. Across the range of planet sizes, I account for the atmospheres expanding to high altitudes as they warm. The emitting and absorbing surfaces (optical depth of unity) move to high altitude, making their area larger than the planet surface, so more thermal radiation is emitted and more sunlight absorbed (the former dominates). The atmospheres of small planets expand more due to weaker gravity; the effective runaway greenhouse threshold is about 35 W m−2 higher for Mars, 10 W m−2 higher for Earth or Venus, but only a few W m−2 higher for a 10 Earth-mass planet. There is an underlying (expansion-neglected) trend of increasing runaway greenhouse threshold with planetary size (40 W m−2 higher for a 10 Earth-mass planet than for Mars). Summing these opposing trends means that Venus-sized (or slightly smaller) planets are most susceptible to a runaway greenhouse. The habitable zone for pure water atmospheres is very narrow, with an insolation range of 0.07 times the solar constant. A wider habitable zone requires background gas and greenhouse gas: N2 and CO2 on Earth, which are biologically controlled. Thus, habitability depends on inhabitance. Key Words

  15. Effect of Upper Atmospheric Water on Martian Photochemistry and Water Loss

    NASA Astrophysics Data System (ADS)

    Chaffin, M.; Deighan, J.; Stewart, I. F.; Schneider, N. M.

    2014-12-01

    Volatile loss to space may have dominated the history of the Martian climate, removing a substantial fraction of the water initially present on the planet over the last four billion years. Until recently, the atomic H component of this loss was thought to be relatively constant in time, based on arguments from Mariner data that the source of the escaping H was molecular hydrogen, with an atmospheric lifetime of decades. New data gathered by the SPectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) instrument on the European Space Agency's Mars Express mission has shown that H escape varies by more than an order of magnitude in Fall 2007 alone, requiring a different parent molecule for the escaping atomic H. Using a completely new 1D time-dependent photochemical model of the Martian atmosphere, we investigate the effect of transient upper atmospheric water vapor on H and O escape to space and the abundance of minor species throughout the atmosphere. We demonstrate that detached water layers between 40-100 km, recently discovered by the infrared channel of SPICAM, produce an order of magnitude increase in the escape rate of H from the Martian atmosphere to space on a timescale of months. This provides an explanation for the observed H escape variation, adding to evidence that the upper, middle, and lower atmosphere of Mars are more tightly coupled in time than was previously expected. Implications for MAVEN measurements and for reconstructing the history of Martian water loss and the oxidation state of the crust will be discussed. Support for this work was provided by the NASA Earth and Space Science Fellowship Program, Award Number NNX11AP49H.

  16. Water Deposition into Titan atmosphere from Saturn's E-ring

    NASA Astrophysics Data System (ADS)

    Juhasz, A.; Horanyi, M.; Kempf, S.; Srama, R.

    2013-12-01

    Cassini's discovery of the geologically active regions on the south polar region of Enceladus allowed the identification of these active plumes as the primary source of Saturn's E-ring. Micron and submicron sized ice particles are supplied from the plumes to sustain the entire E-ring. In situ measurements by the Cassini Cosmic Dust Analyzer (CDA) also led to the recognition that the E-ring extends way beyond its originally recognized limits of 4 - 8 Saturn radii (Rs), reaching beyond 20 Rs, engulfing Titan, Saturn's largest moon. Ice grains entrained in the plumes experience radiation pressure and plasma drag perturbations and their orbits slowly evolve outward. Simultaneously, the ice particles are exposed to energetic ion bombardment, leading to their mass loss due to sputtering. Initially micron sized particles from Enceladus take about 500 years to reach the orbit of Titan, arriving there as approximately 0.1-0.3 micron sized particles. Due to their large eccentricities, these small grains enter Titan's atmosphere with speeds v > 1 km/s,sufficiently fast to ablate, delivering on the order of 5 g/s of water. This presentation will discuss the resulting profiles of water vapor deposition rates as function of altitude in Titan's atmosphere.

  17. Numerical implementation and oceanographic application of the thermodynamic potentials of liquid water, water vapour, ice, seawater and humid air - Part 2: The library routines

    NASA Astrophysics Data System (ADS)

    Wright, D. G.; Feistel, R.; Reissmann, J. H.; Miyagawa, K.; Jackett, D. R.; Wagner, W.; Overhoff, U.; Guder, C.; Feistel, A.; Marion, G. M.

    2010-07-01

    The SCOR/IAPSO1 Working Group 127 on Thermodynamics and Equation of State of Seawater has prepared recommendations for new methods and algorithms for numerical estimation of the the thermophysical properties of seawater. As an outcome of this work, a new International Thermodynamic Equation of Seawater (TEOS-10) was endorsed by IOC/UNESCO2 in June 2009 as the official replacement and extension of the 1980 International Equation of State, EOS-80. As part of this new standard a source code package has been prepared that is now made freely available to users via the World Wide Web. This package includes two libraries referred to as the SIA (Sea-Ice-Air) library and the GSW (Gibbs SeaWater) library. Information on the GSW library may be found on the TEOS-10 web site (http://www.TEOS-10.org). This publication provides an introduction to the SIA library which contains routines to calculate various thermodynamic properties as discussed in the companion paper. The SIA library is very comprehensive, including routines to deal with fluid water, ice, seawater and humid air as well as equilibrium states involving various combinations of these, with equivalent code developed in different languages. The code is hierachically structured in modules that support (i) almost unlimited extension with respect to additional properties or relations, (ii) an extraction of self-contained sub-libraries, (iii) separate updating of the empirical thermodynamic potentials, and (iv) code verification on different platforms and between different languages. Error trapping is implemented to identify when one or more of the primary routines are accessed significantly beyond their established range of validity. The initial version of the SIA library is available in Visual Basic and FORTRAN as a supplement to this publication and updates will be maintained on the TEOS-10 web site. 1SCOR/IAPSO: Scientific Committee on Oceanic Research

  18. Exchange of water vapor between the atmosphere and surface of Mars.

    NASA Technical Reports Server (NTRS)

    Leovy, C. B.

    1973-01-01

    A model for exchange of water from the atmosphere to condensing CO2 caps is developed. The rate of water condensation in the caps is assumed to be proportional to the meridional heat flux. It follows that the amount of water condensed in the caps varies inversely with the amount of CO2 condensed. The seasonal phase of the release of water from the caps is not consistent with observed variations in the abundance of atmospheric water. Seasonal variations of atmospheric water abundance are most consistent with vapor exchange between the atmosphere and permafrost in the subtropics.

  19. Production of sulphate-rich vapour during the Chicxulub impact and implications for ocean acidification

    NASA Astrophysics Data System (ADS)

    Ohno, Sohsuke; Kadono, Toshihiko; Kurosawa, Kosuke; Hamura, Taiga; Sakaiya, Tatsuhiro; Shigemori, Keisuke; Hironaka, Yoichiro; Sano, Takayoshi; Watari, Takeshi; Otani, Kazuto; Matsui, Takafumi; Sugita, Seiji

    2014-04-01

    The mass extinction event at the Cretaceous/Palaeogene boundary 65.5 Myr ago has been widely attributed to the Chicxulub impact, but the mechanisms of extinction remain debated. In the oceans, near-surface planktonic foraminifera suffered severe declines, in contrast to the relatively high survival rates of bottom-dwelling benthic foraminifera. The vapour produced by an impact into Chicxulub's target rocks, which include sulphate-rich anhydrite, could have led to global acid rain, which can explain the pattern of oceanic extinctions. However, it has been suggested that most of the sulphur in the target rocks would have been released as sulphur dioxide and would have stayed in the stratosphere for a long time. Here we show, from impact experiments into anhydrite at velocities exceeding 10 km s-1, that sulphur trioxide dominates over sulphur dioxide in the resulting vapour cloud. Our experiments suggest that the Chicxulub impact released a huge quantity of sulphur trioxide into the atmosphere, where it would have rapidly combined with water vapour to form sulphuric acid aerosol particles. We also find, using a theoretical model of aerosol coagulation following the Chicxulub impact, that larger silicate particles ejected during the impact efficiently scavenge sulphuric acid aerosol particles and deliver the sulphuric acid to the surface within a few days. The rapid surface deposition of sulphuric acid would cause severe ocean acidification and account for preferential extinction of planktonic over benthic foraminifera.

  20. Automated continuous monitoring of inorganic and total mercury in wastewater and other waters by flow-injection analysis and cold-vapour atomic absorption spectrometry

    PubMed Central

    Birnie, S. E.

    1988-01-01

    An automated continuous monitoring system for the determination of inorganic and total mercury by flow-injection analysis followed by cold-vapour atomic absorption spectrometry is described. The method uses a typical flow-injection manifold where digestion and reduction of the injected sample takes place. Mercury is removed by aeration from the flowing stream in a specially designed air-liquid separator and swept into a silica cell for absorption measurement at a wavelength of 253.7 nm. A calibration curve up to 10 μg Hg ml-1 using three different path length cells is obtained with a detection limit of 0.02 μg Hg ml-1. The sampling rate of an injection every 3 min produces 20 results per hour from a flowing stream. PMID:18925201

  1. Mars atmospheric water vapor abundance: 1996-1997

    NASA Astrophysics Data System (ADS)

    Sprague, A. L.; Hunten, D. M.; Doose, L. R.; Hill, R. E.

    2003-05-01

    Measurements of martian atmospheric water vapor made throughout Ls = 18.0°-146.4° (October 3, 1996-July 12, 1997) show changes in Mars humidity on hourly, daily, and seasonal time scales. Because our observing program during the 1996-1997 Mars apparition did not include concomitant measurement of nearby CO 2 bands, high northern latitude data were corrected for dust and aerosol extinction assuming an optical depth of 0.8, consistent with ground-based and HST imaging of northern dust storms. All other measurements with airmass greater than 3.5 were corrected using a total optical depth of 0.5. Three dominant results from this data set are as follows: (1) pre- and post-opposition measurements made with the slit crossing many hours of local time on Mars' Earth-facing disk show a distinct diurnal pattern with highest abundances around and slightly after noon with low abundances in the late afternoon, (2) measurements of water vapor over the Mars Pathfinder landing site (Carl Sagan Memorial Station) on July 12, 1997, found 21 ppt μm in the spatial sector centered near 19° latitude, 36° longitude while abundances around the site varied from as low as 6 to as high as 28 ppt μm, and (3) water vapor abundance is patchy on hourly and daily time scales but follows the usual seasonal trends.

  2. The slant path atmospheric refraction calibrator - An instrument to measure the microwave propagation delays induced by atmospheric water vapor

    NASA Technical Reports Server (NTRS)

    Walter, Steven J.; Bender, Peter L.

    1992-01-01

    The water vapor-induced propagation delay experienced by a radio signal traversing the atmosphere is characterized by the Slant Path Atmospheric Refraction Calibrator (SPARC), which measures the difference in the travel times between an optical and a microwave signal propagating along the same atmospheric path with an accuracy of 15 picosec or better. Attention is given to the theoretical and experimental issues involved in measuring the delay induced by water vapor; SPARC measurements conducted along a 13.35-km ground-based path are presented, illustrating the instrument's stability, precision, and accuracy.

  3. A synthesis of atmospheric mercury depletion event chemistry linking atmosphere, snow and water

    NASA Astrophysics Data System (ADS)

    Steffen, A.; Douglas, T.; Amyot, M.; Ariya, P.; Aspmo, K.; Berg, T.; Bottenheim, J.; Brooks, S.; Cobbett, F.; Dastoor, A.; Dommergue, A.; Ebinghaus, R.; Ferrari, C.; Gardfeldt, K.; Goodsite, M. E.; Lean, D.; Poulain, A.; Scherz, C.; Skov, H.; Sommar, J.; Temme, C.

    2007-07-01

    It was discovered in 1995 that, during the spring time, unexpectedly low concentrations of gaseous elemental mercury (GEM) occurred in the Arctic air. This was surprising for a pollutant known to have a long residence time in the atmosphere; however conditions appeared to exist in the Arctic that promoted this depletion of mercury (Hg). This phenomenon is termed atmospheric mercury depletion events (AMDEs) and its discovery has revolutionized our understanding of the cycling of Hg in Polar Regions while stimulating a significant amount of research to understand its impact to this fragile ecosystem. Shortly after the discovery was made in Canada, AMDEs were confirmed to occur throughout the Arctic, sub-Artic and Antarctic coasts. It is now known that, through a series of photochemically initiated reactions involving halogens, GEM is converted to a more reactive species and is subsequently associated to particles in the air and/or deposited to the polar environment. AMDEs are a means by which Hg is transferred from the atmosphere to the environment that was previously unknown. In this article we review the history of Hg in Polar Regions, the methods used to collect Hg in different environmental media, research results of the current understanding of AMDEs from field, laboratory and modeling work, how Hg cycles around the environment after AMDEs, gaps in our current knowledge and the future impacts that AMDEs may have on polar environments. The research presented has shown that while considerable improvements in methodology to measure Hg have been made the main limitation remains knowing the speciation of Hg in the various media. The processes that drive AMDEs and how they occur are discussed. As well, the roles that the snow pack, oceans, fresh water and the sea ice play in the cycling of Hg are presented. It has been found that deposition of Hg from AMDEs occurs at marine coasts and not far inland and that a fraction of the deposited Hg does not remain in the same

  4. Comparison of time series of integrated water vapor measured using radiosonde, GPS and microwave radiometer at the CNR-IMAA Atmospheric Observatory

    NASA Astrophysics Data System (ADS)

    Amato, Franceso; Rosoldi, Marco; Madonna, Fabio

    2015-04-01

    Information about the amount and spatial distribution of atmospheric water vapor is essential to improve our knowledge of weather forecasting and climate change. Water vapor is highly variable in space and time depending on the complex interplay of several phenomena like convection, precipitation, turbulence, etc. It remains one of the most poorly characterized meteorological parameters. Remarkable progress in using of Global Navigation Satellite Systems (GNSS), in particular GPS, for the monitoring of atmospheric water vapor has been achieved during the last decades. Various studies have demonstrated that GPS could provide accurate water vapor estimates for the study of the atmosphere. Different GPS data processing provided within the scientific community made use of various tropospheric models that primarily differs for the assumptions on the vertical refractivity profiles and the mapping of the vertical delay with elevation angles. This works compares several models based on the use of surface meteorological data. In order to calculate the Integrated Water Vapour (IWV), an algorithm for calculating the zenith tropospheric delay was implemented. It is based upon different mapping functions (Niell, Saastamoinen, Chao and Herring Mapping Functions). Observations are performed at the Istituto di Metodologie per l'Analisi Ambientale (IMAA) GPS station located in Tito Scalo, Potenza (40.60N, 15.72E), from July to December 2014, in the framework of OSCAR project (Observation System for Climate Application at Regional scale). The retrieved values of the IWV using the GPS are systematically compared with the other estimation of IWV collected at CIAO (CNR-IMAA Atmospheric Observatory) using the other available measurement techniques. In particular, in this work the compared IWV are retrieved from: 1. a Trimble GPS antenna (data processed by the GPS-Met network, see gpsmet.nooa.gov); 2. a Novatel GPS antenna (data locally processed using a software developed at CIAO); 3

  5. A eutectic gold vapour laser

    NASA Astrophysics Data System (ADS)

    Tou, T. Y.; Cheak, K. E.; Low, K. S.

    This paper presents a eutectic gold vapour laser (EGVL) which uses the eutectic alloy of gold and silicon, Au/3.15Si, as the lasant. It was observed that, at low input power operation, the presence of the silicon vapour could increase the output of the 627.8 nm laser line by (50-60)% when compared with a gold vapour laser (GVL) which uses pure gold as the lasant. The improved laser output for the EGVL may be explained by an increased electron density, as a result of Penning ionization of silicon atoms. However, for higher input power operation, the EGVL showed a slower rate of increase in its laser output power and was overtaken by GVLs at a tube operating temperature of around 1650°C. This may be explained by a lowering of the electron temperature owing to increasing inelastic collisions between the electrons and silicon atoms which, although excited, may not produce additional electrons.

  6. The ignitability of petrol vapours and potential for vapour phase explosion by use of TASER® law enforcement electronic control device.

    PubMed

    Clarke, C; Andrews, S P

    2014-12-01

    An experimental study was made of the potential of the TASER-X26™ law enforcement electronic control device to ignite petrol vapours if used by an officer to incapacitate a person soaked in petrol, or within a flammable atmosphere containing petrol vapour. Bench scale tests have shown that a wooden mannequin with pig skin covering the chest was a suitable representation of a human target. Full scale tests using the mannequin have shown that the arc from a TASER-X26™ is capable of igniting petrol/air vapours on a petrol-soaked person. Further tests in a 1/5 scale and a full scale compartment have shown that if a TASER is used within a compartment, a petrol vapour explosion (deflagration) may be achieved. It is evident from this research that if used in a flammable vapour rich environment, the device could prove fatal not only to the target but the TASER® operator as well. PMID:25498927

  7. Seasonal and global behavior of water vapor in the Mars atmosphere: Complete global results of the Viking atmospheric water detector experiment

    SciTech Connect

    Jakosky, B.M.; Farmer, C.B.

    1982-04-10

    The water vapor content of the Mars atmosphere was measured from the Viking Orbiter Mars Atmospheric Water Detectors (MAWD) for a period of more than 1 Martian year, from June 1976 through April 1979. Results are presented in the form of global maps of column abundance for 24 periods throughout each Mars year. The data reduction incorporates spatial and seasonal variations in surface pressure and supplements earlier published versions of less complete data.

  8. International Space Station Atmosphere Control and Supply, Atmosphere Revitalization, and Water Recovery and Management Subsystem - Verification for Node 1

    NASA Technical Reports Server (NTRS)

    Williams, David E.

    2007-01-01

    The International Space Station (ISS) Node 1 Environmental Control and Life Support (ECLS) System is comprised of five subsystems: Atmosphere Control and Supply (ACS), Atmosphere Revitalization (AR), Fire Detection and Suppression (FDS), Temperature and Humidity Control (THC), and Water Recovery and Management (WRM). This paper provides a summary of the nominal operation of the Node 1 ACS, AR, and WRM design and detailed Element Verification methodologies utilized during the Qualification phase for Node 1.

  9. Tm:germanate Fiber Laser for Planetary Water Vapor Atmospheric Profiling

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; De Young, Russell

    2009-01-01

    The atmospheric profiling of water vapor is necessary for finding life on Mars and weather on Earth. The design and performance of a water vapor lidar based on a Tm:germanate fiber laser is presented.

  10. Latitudinal survey of middle atmospheric water vapor revealed by shipboard microwave spectroscopy. Master's thesis

    SciTech Connect

    Schrader, M.L.

    1994-05-01

    Water vapor is one of the most important greenhouse gases and is an important tracer of atmospheric motions in the middle atmosphere. It also plays an important role in the chemistry of the middle atmosphere and through its photodissociation by solar radiation, it is the major source of hydrogen escaping to space. Ground-based microwave measurements conducted in the 1980s have provided a fair understanding of the seasonal variation of mesospheric water vapor in the northern hemisphere mid-latitudes, but the global distribution of water vapor in the middle atmosphere is only beginning to be revealed by space-based measurements.

  11. Vapour Intrusion into Buildings - A Literature Review

    EPA Science Inventory

    This chapter provides a review of recent research on vapour intrusion of volatile organic compounds (VOCs) into buildings. The chapter builds on a report from Tillman and Weaver (2005) which reviewed the literature on vapour intrusion through 2005. Firstly, the term ‘vapour intru...

  12. Water solubility in rhyolitic silicate melts at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Ryan, Amy; Russell, Kelly; Nichols, Alexander; Porritt, Lucy; Friedlander, Elizabeth

    2014-05-01

    High temperature (900-1100 °C) experiments have been conducted to measure the solubility of water in a rhyolitic melt at atmospheric pressure (1 atm) and to quantify the magnitude of retrograde solubility at low pressure. Individual cores (1 cm x 1 cm) of crystal- and bubble-free rhyolitic obsidian from Hrafntinnugryggur, Krafla (Iceland) were held in a furnace at 900-1100 °C for 0.25 to 20 hours. During this time, the uniform bubble-free cores vesiculate to produce variably swollen bubble-rich run products. The volume change in each core reflects the volume of bubbles produced in each experiment and depends on the experimental temperature and the time held at that temperature. The run product volumes for isothermal experiments (e.g., 950 °C) increase non-linearly with increasing time (e.g., 0.18 cm3 at 1.5 h, 0.96 cm3 at 12.5 h) until reaching a maximum value, after which the volume does not change appreciably. We take this plateau in the isothermal volume:time curve as coinciding with the 1 atm. solubility limit for the rhyolite at this temperature. With increasing temperature, the slope and final horizontal plateaus of the volume:time curves increase such that samples from the higher temperature suites vesiculate more, as well as more rapidly (e.g., 0.85 cm3 after 0.5 hours, 1.78 cm3 after 1 hour at 1100 °C). The variations in the maximum volume of bubbles produced for each temperature constrain the retrograde solubility of water in the melt at 1 atm. Fourier transform infrared spectroscopy (FTIR) analyses of the residual water content of the glass in the starting material and in the most vesiculated sample from each temperature suite shows a decrease in the water content of the glass from an initial 0.114 wt% (σ 0.013) to 0.098 wt% (σ 0.010), 0.087 wt% (σ 0.009), 0.093 wt% (σ 0.008), 0.090 wt% (σ 0.006) and 0.108 wt% (σ 0.010) for 900 °C, 950 °C, 1000 °C, 1050 °C and 1100 °C respectively. This change in the solubility of water at different

  13. On-line speciation of inorganic and methyl mercury in waters and fish tissues using polyaniline micro-column and flow injection-chemical vapour generation-inductively coupled plasma mass spectrometry (FI-CVG-ICPMS).

    PubMed

    Krishna, M V Balarama; Chandrasekaran, K; Karunasagar, D

    2010-04-15

    A simple and efficient method for the determination of ultra-trace amounts of inorganic mercury (iHg) and methylmercury (MeHg) in waters and fish tissues was developed using a micro-column filled with polyaniline (PANI) coupled online to flow injection-chemical vapour generation-inductively coupled plasma mass spectrometry (FI-CVG-ICPMS) system. Preliminary studies indicated that inorganic and methyl mercury species could be separated on PANI column in two different speciation approaches. At pH <3, only iHg could be sorbed and almost no adsorption of MeHg was found (speciation procedure 1). If the sample solution pH is approximately 7, both MeHg and iHg species could be sorbed on the PANI column. Subsequently both the Hg species were selectively eluted with 2% HCl and a mixture of 2% HCl and 0.02% thiourea respectively (speciation procedure 2). The adsorption percentage of iHg on the PANI column was unchanged even with acidity of the sample solution increased to 6 mol L(-1). Therefore, an acidic solution (5 mol L(-1) HCl), used for ultra-sound assisted extraction of the mercury species from biological samples, was used directly to separate MeHg from iHg in the fish tissues (tuna fish ERM-CE 463, ERM-CE 464 and IAEA-350) by PANI column using speciation procedure 1. The determined values were in good agreement with certified values. Under optimal conditions, the limits of detection (LODs) were 2.52 pg and 3.24 pg for iHg and MeHg (as Hg) respectively. The developed method was applied successfully to the direct determination of iHg and MeHg in various waters (tap water, lake water, ground water and sea-water) and the recoveries for the spiked samples were in the range of 96-102% for both the Hg species. PMID:20188947

  14. Comparing Stable Water Isotope Variation in Atmospheric Moisture Observed over Coastal Water and Forests

    NASA Astrophysics Data System (ADS)

    Lai, C. T.; Rambo, J. P.; Welp, L. R.; Bible, K.; Hollinger, D. Y.

    2014-12-01

    Stable oxygen (δ18O) and hydrogen (δD) isotopologues of atmospheric moisture are strongly influenced by large-scale synoptic weather cycles, surface evapotranspiration and boundary layer mixing. Atmospheric water isotope variation has been shown to empirically relate to relative humidity (Rh) of near surface moisture, and to a less degree, air temperature. Continuous δ18O and δD measurements are becoming more available, providing new opportunities to investigate processes that control isotope variability. This study shows the comparison of δ18O and δD measured at a continental location and over coastal waters for 3 seasons (spring to fall, 2014). The surface moisture isotope measurements were made using two LGR spectroscopy water vapor isotope analyzers (Los Gatos Research Inc.), one operated in an old-growth coniferous forest at Wind River field station, WA (45.8205°N, 121.9519°W), and another sampling marine air over seawater at the Scripps Pier in San Diego, CA (32.8654°N, 117.2536°W), USA. Isotope variations were measured at 1Hz and data were reported as hourly averages with an overall accuracy of ±0.1‰ for δ18O, ±0.5‰ for δ2H. Day-to-day variations in δ18O and δD are shown strongly influenced by synoptic weather events at both locations. Boundary layer mixing between surface moisture and the dry air entrained from the free troposphere exerts a midday maximum and a consistent diel pattern in deuterium excess (dx). At the forest site, surface moisture also interacts with leaf water through transpiration during the day and re-equilibration at night. The latter occurs by retro-diffusion of atmospheric H2O molecules into leaf intercellular space, which becomes intensified as Rh increaes after nightfall, and continues until sunrise, to counter-balance the evaporative isotopic enrichment in leaf water on a daily basis. These vegetation effects lead to negative dx values consistently observed at nighttime in this continental location that were not

  15. Atmospheric nitrogen deposition in estuarine and coastal waters: Biogeochemical and water quality impacts

    SciTech Connect

    Paerl, H.W.; Peierls, B.L.; Fogel, M.L.; Aguilar, C. |

    1994-12-31

    Atmospheric deposition (AD) is a significant source of biologically-available ``new`` nitrogen in N-limited estuarine and coastal ocean waters. From 10 to over 50% of ``new`` N inputs are attributable to AD in waters ``downwind`` of emissions. In situ microcosm and mesocosm bioassays indicate that this ``new`` N source can enhance microalgal primary production and may alter community composition. Relative to terrestrial and regenerated N inputs, the dominant AD-N sources, NO{sub 3}k{sup {minus}}, NH{sub 4}{sup {plus}}, and dissolves organic nitrogen (DON) reveal stable N isotope ratios ({delta}{sup 15}N) generally deplete in {sup 15}N. The relatively low {delta}{sup 15}N ratio of AD-N has been used as a tracer of the incorporation and fate of this ``new`` N source in receiving water. Diagnostic biomarker molecules, including proteins and pigments (chlorophylls), indicate rapid algal utilization and transformation of AD-N. Seasonal production and N isotope studies in mixed and stratified North Carolina Atlantic coastal and offshore (i.e. Gulf Stream) waters indicate a marked impact of AD-N on microbial production. AD-N is an important and thus far poorly recognized source of ``new`` N in N-limited waters; these waters characterized a large proportion of the world`s estuarine and coastal zones. AD-N may additionally play a role in recently-noted coastal eutrophication and algal nuisance bloom dynamics.

  16. CO2-fluxing collapses metal mobility in magmatic vapour

    DOE PAGESBeta

    van Hinsberg, V. J.; Berlo, K.; Migdisov, A. A.; Williams-Jones, A. E.

    2016-05-18

    Magmatic systems host many types of ore deposits, including world-class deposits of copper and gold. Magmas are commonly an important source of metals and ore-forming fluids in these systems. In many magmatic-hydrothermal systems, low-density aqueous fluids, or vapours, are significant metal carriers. Such vapours are water-dominated shallowly, but fluxing of CO2-rich vapour exsolved from deeper magma is now recognised as ubiquitous during open-system magma degassing. Furthermore, we show that such CO2-fluxing leads to a sharp drop in element solubility, up to a factor of 10,000 for Cu, and thereby provides a highly efficient, but as yet unrecognised mechanism for metalmore » deposition.« less

  17. CW-Cavity Ring Down Spectroscopy of deuterated water in the 1.58 μm atmospheric transparency window

    NASA Astrophysics Data System (ADS)

    Liu, A.-W.; Naumenko, O. V.; Kassi, S.; Campargue, A.

    2014-05-01

    The spectrum of water vapour enriched in deuterium has been recorded by highly sensitive CW-Cavity Ring Down Spectroscopy in the 5855-6802 cm-1 spectral region. The studied region includes the 1.58 μm atmospheric transparency window of particular interest for remote sensing. More than 8000 absorption lines belonging to eight water isotopologues - H216O, H218O HD16O, D216O, HD18O, D218O, HD17O and D217O - were identified. The spectrum was assigned using both the IUPAC database of experimental transitions and energy levels, and accurate variational calculations. Overall, 1396 and 1277 experimental energy levels belonging to 18 and 16 upper vibrational states were retrieved for the HD16O and D216O species, respectively. 773 energy levels are newly derived. New experimental information concerns the high J (up to 20) and high Ka (up to 12) energy levels of the (101), (021), (040), (210), (120) states of HD16O and of the (111), (031), (210), (012), (130) states of D216O. While only a few energy levels were available, the rotational structure of the (130) and (220) states of HD16O could be analysed in detail. Rotational sublevels of the (140) state of D216O are reported for the first time. A detailed comparison of the derived energy levels with the values recommended by an IUPAC task group is presented. In particular, a significant improvement is evidenced for a number of quasi degenerate energy levels of HD16O. The obtained results are also discussed in relation with several recent studies.

  18. The water cycles of water-soluble organic salts of atmospheric importance

    NASA Astrophysics Data System (ADS)

    Peng, Changgeng; Chan, Chak K.

    In this study, the water cycles of nine water-soluble organic salts of atmospheric interest were studied using an electrodynamic balance (EDB) at 25°C. Sodium formate, sodium acetate, sodium succinate, sodium pyruvate and sodium methanesulfonate (Na-MSA) particles crystallize as the relative humidity (RH) decreases and they deliquesce as the RH increases. Sodium oxalate and ammonium oxalate form supersaturated particles at low RH before crystallization but they do not deliquesce even at RH=90%. Sodium malonate and sodium maleate particles neither crystallize nor deliquesce. These two salts absorb and evaporate water reversibly without hysteresis. In most cases, the solid states of single particles resulting from the crystallization of supersaturated droplets do not form the most thermodynamically stable state found in bulk studies. Sodium formate, sodium oxalate, ammonium oxalate, sodium succinate, sodium pyruvate and Na-MSA form anhydrous particles after crystallization. Sodium acetate forms particles with a water/salt molar ratio of 0.5 after crystallization. In salts with several hydrated states including sodium formate and sodium acetate, the particles deliquesce at the lowest deliquescence relative humidity (DRH) of the hydrates. Except sodium oxalate and ammonium oxalate, all the salts studied here are as hygroscopic as typical inorganic hygroscopic aerosols. The hygroscopic organic salts have a growth factor of 1.76-2.18 from RH=10-90%, comparable to that of typical hygroscopic inorganic salts such as NaCl and (NH 4) 2SO 4. Further study of other atmospheric water-soluble organic compounds and their mixtures with inorganic salts is needed to explain the field observations of the hygroscopic growth of ambient aerosols.

  19. Land atmosphere exchange of water and energy in global change modeling

    SciTech Connect

    Dickinson, R.E.

    1995-06-01

    The biosphere is crucially coupled to the atmosphere through exchanges of water and energy and these exchanges are important for the modeling of global climate change. Key surface properties for modeling inputs to the atmosphere are albedo, aerodynamic roughness, canopy resistance to water flux and water holding capacity of soils. This paper indicates how these affect climate models and what are current limitations in specifying them. One of the recent surprises from research in this area is the strong effect these processes can have on the atmospheric hydrological cycle, and especially precipitation. Modeling of the surface energy and water processes determines such important quantities as surface temperature and moisture availability for vegetation and runoff, and in general, the physical environment for the biosphere. Global atmospheric models are still inadequate for provision of realistic inputs of solar energy and precipitation, but are improving. Ultimately, their success depends on improved treatments of the atmospheric hydrological cycle, which is a key question for current climate research.

  20. Atmospheric Dynamics Deduced from UARS Using Middle Atmosphere ISAMS Carbon Monoxide and Upper-Tropospheric MLS Water Vapor and Ice Data

    NASA Technical Reports Server (NTRS)

    Standford, John L.

    2002-01-01

    This project involved analyses of atmospheric constituent data fields, carbon monoxide in the upper stratospheric/lower mesosphere, and water vapor in the upper troposphere. The observational data analyses were compared with atmospheric models.

  1. On the global relationships between photosynthetic water-use efficiency, leaf mass per unit area and atmospheric demand in woody and herbaceous plants

    NASA Astrophysics Data System (ADS)

    Letts, M. G.; Fox, T. A.; Gulias, J.; Galmes, J.; Hikosaka, K.; Wright, I.; Flexas, J.; Awada, T.; Rodriguez-Calcerrada, J.; Tobita, H.

    2013-12-01

    A global dataset was compiled including woody and herbaceous C3 species from forest, Mediterranean and grassland-shrubland ecosystems, to elucidate the dependency of photosynthetic water-use efficiency on vapour pressure deficit (D) and leaf traits. Mean leaf mass per unit area (LMA) was lower and mass-based leaf nitrogen content (Nmass) was higher in herbaceous species. Higher mean stomatal conductance (gs), transpiration rate (E) and net CO2 assimilation rate under light saturating conditions (Amax) were observed in herbs, but photosynthetic and intrinsic water-use efficiencies (WUE = Amax/E and WUEi = Amax/gs) were lower than in woody plants. Woody species maintained stricter stomatal regulation of water loss at low D, resulting in a steeper positive and linear relationship between log D and log E. Herbaceous species possessed very high gs at low D, resulting in higher ratio of substomatal to atmospheric CO2 concentrations (ci/ca) and E, but lower WUE and WUEi than woody plants, despite higher Amax. The lower WUE and higher rates of gas exchange were most pronounced in herbs with low LMA and high Nmass. Photosynthetic water use also differed between species from grassland-shrubland and Mediterranean or forest environments. Water-use efficiency showed no relationship with either D or LMA in grassland-shrubland species, but showed a negative relationship with D in forest and chaparral. The distinct photosynthetic water-use of woody and herbaceous plants is consistent with the opportunistic growth strategy of herbs and the more conservative growth strategy of woody species. Further research is recommended to examine the implications of these functional group and ecosystem differences in the contexts of climate and atmospheric change.

  2. O the Role of Water Growth in Atmospheric Aerosol

    NASA Astrophysics Data System (ADS)

    Pitchford, Marc Lynn

    1992-01-01

    Atmospheric particle growth by condensation of water vapor was investigated using sophisticated particle growth and compositional measurements made during the Winter of 1990 at Grand Canyon National Park, AZ. Growth measurements by the Tandem Differential Mobility Analyzer (TDMA) and fine particle compositional analysis data were examined to assess the nature of the particles and the applicability of certain growth and composition models. A model was developed to estimate the sulfate to ammonium ion concentration ratio by apportioning measured hydrogen concentrations between organic and sulfate aerosol components. The model had insufficient resolution for this data to determine the ion ratio. The overall volume fraction of soluble material as determined by chemical analysis of particle samples was apportioned between high growth and low growth particles by a model based upon TDMA measured growth data. Growth data indicate the simultaneous presence of two, and occasionally three, types of particles. At relative humidities above about 78%, particles split into two distinguishable growth categories. Most of the particles grew considerably (categorized as more hygroscopic), while a small fraction of the particles grew slightly (categorized as less hygroscopic). On a few days, particles separated by growth at relative humidities in the mid-60% range, with a small fraction of the particles having high growth. At higher relative humidities these particles became indistinguishable from the more hygroscopic particles. Sulfate species dominate the soluble fraction most days, with nitrates occasionally in comparable concentrations. The model to estimate the soluble fraction of the particles in the more and less hygroscopic growth categories also determines the soluble material growth characteristic, which is assumed to be the same for all particles in any individual TDMA measurement. The predicted growth characteristics for the soluble material is in good agreement with

  3. Light propagation through atomic vapours

    NASA Astrophysics Data System (ADS)

    Siddons, Paul

    2014-05-01

    This tutorial presents the theory necessary to model the propagation of light through an atomic vapour. The history of atom-light interaction theories is reviewed, and examples of resulting applications are provided. A numerical model is developed and results presented. Analytic solutions to the theory are found, based on approximations to the numerical work. These solutions are found to be in excellent agreement with experimental measurements.

  4. Evaluating the vapour shift concept in agriculture: some aspects

    NASA Astrophysics Data System (ADS)

    Schmidt, S.; Metselaar, K.; van Dam, J. C.; Klik, A.

    2009-04-01

    Human population growth leads to an increasing pressure on freshwater resources. By 2050 Falkenmark et al. (2004) estimate a global water deficit for crop production of 5800 km3.y-1. This has important consequences for management of fresh water resources at different scales, and new strategies at different scales are required. One of the strategies suggested is that of managing crops in such a way that the use of rainfall and irrigation is shifted as much as possible from evaporation towards transpiration, a so-called vapour shift. The suggested savings are in the order of 330 km3.y-1, and are based on estimates of the magnitude of three processes: Reducing early season evaporation; increasing canopy cover; and increasing yield levels. The vapour shift concept was evaluated empirically, and in a simulation study. The empirical evaluation using results for wheat, maize, millet, cotton, and barley suggests the estimate of potential savings is 37% lower than the estimate by Falkenmark et al. (2004). The uncertainty is large and due to the limited number of experiments in which a separation of evapotranspiration in evaporation and transpiration has been made over the entire growing season. This suggests that theoretical support for the vapour shift concept should become more important. In the simulation approach two management options, mulching and planting density, are evaluated for a site in India for an irrigated wheat crop using a simulation approach for water limited crop yield. Given the simulation model used, and the management options investigated, the assumption implicit in the vapour shift concept - decreasing evaporation with increasing yield level - does not hold in irrigated areas, or in areas in which water is the most limiting factor. This suggests that vapour shift will be largest in those areas where nutrients and pests- and diseases are still limiting or reducing crop yields, and measures are taken to reduce those limitations.

  5. HDO in the Martian atmosphere: implications for the abundance of crustal water.

    PubMed

    Yung, Y L; Wen, J S; Pinto, J P; Allen, M; Pierce, K K; Paulson, S

    1988-01-01

    The physical and chemical processes that lead to the preferential escape of hydrogen over deuterium in the Martian atmosphere are studied in detail using a one-dimensional photochemical model. Comparison of our theory with recent observations of HDO suggests that, averaged over the planet, Mars contains 0.2 m of crustal water that is exchangeable with the atmosphere. Our estimate is considerably lower than recent estimates of subsurface water on Mars based on geomorphological analysis of Viking images. The estimate can be reconciled if only a small fraction of crustal water can exchange with the atmosphere. PMID:11538666

  6. HDO in the Martian atmosphere - implications for the abundance of crustal water

    SciTech Connect

    Yung, Y.L.; Wen, J.S.; Pinto, J.P.; Pierce, K.K.; Allen, M.

    1988-10-01

    A one-dimensional photochemical model is presently used to ascertain the nature of those chemical and physical processes of the Martian atmosphere responsible for the preferential escape of hydrogen over deuterium. A comparison of the present theoretical considerations with recent HDO observations indicates that Mars contains 0.2 m of (globally averaged) crustal water that is exchangeable with the atmosphere. This estimate, which is substantially lower than those obtained for Martian subsurface water on the basis of Viking image-derived geomorphological analyses, can be reconciled only if a small fration of the crustal water is exchangeable with the atmosphere. 67 references.

  7. History of water loss and atmospheric O2 buildup on rocky exoplanets near M dwarfs

    NASA Astrophysics Data System (ADS)

    Tian, Feng

    2015-12-01

    It is recently proposed that early stellar luminosity evolution of M dwarfs leads to severe water loss and the buildup of massive O2 atmospheres on rocky exoplanets in the habitable zone of these stars if interactions of such O2 atmospheres with planetary surfaces are inefficient. Here we show that even without considering atmosphere-surface interactions, the existence of a massive O2 atmosphere on such exoplanets is not an unavoidable consequence around M0-M3 stars and depends on stellar XUV properties, the mass of the exoplanets, and most importantly the initial planetary water inventories. In the case of inefficient atmosphere-surface interactions, the distribution of atmospheric O2 contents on these exoplanets should be bi-modal and such a distribution could be verified by future surveys of rocky exoplanets.

  8. Maintaining Atmospheric Mass and Water Balance Within Reanalysis

    NASA Technical Reports Server (NTRS)

    Takacs, Lawrence L.; Suarez, Max; Todling, Ricardo

    2015-01-01

    This report describes the modifications implemented into the Goddard Earth Observing System Version-5 (GEOS-5) Atmospheric Data Assimilation System (ADAS) to maintain global conservation of dry atmospheric mass as well as to preserve the model balance of globally integrated precipitation and surface evaporation during reanalysis. Section 1 begins with a review of these global quantities from four current reanalysis efforts. Section 2 introduces the modifications necessary to preserve these constraints within the atmospheric general circulation model (AGCM), the Gridpoint Statistical Interpolation (GSI) analysis procedure, and the Incremental Analysis Update (IAU) algorithm. Section 3 presents experiments quantifying the impact of the new procedure. Section 4 shows preliminary results from its use within the GMAO MERRA-2 Reanalysis project. Section 5 concludes with a summary.

  9. The Martian atmospheric water cycle as viewed from a terrestrial perspective

    NASA Technical Reports Server (NTRS)

    Zurek, Richard W.

    1988-01-01

    It is noted that the conditions of temperature and pressure that characterize the atmosphere of Mars are similar to those found in the Earth's stratosphere. Of particular significance is the fact that liquid water is unstable in both environments. Thus, it is expected that terrestrial studies of the dynamical behavior of stratospheric water should benefit the understanding of water transport on Mars as well.

  10. Describing the Components of the Water Transport in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Montmessin, F.; Haberle, R. M.; forget, F.; Rannou, P.; Cabane, M.

    2003-01-01

    In this paper, we examine the meteorological components driving water transport in the Martian atmosphere. A particular emphasis is given to the role of residual mean circulation and water ice clouds in determining the geographical partitioning of water vapor and frost.

  11. The use of coupled atmospheric and hydrological models for water-resources management in headwater basins

    USGS Publications Warehouse

    Leavesley, G.; Hay, L.

    1998-01-01

    Coupled atmospheric and hydrological models provide an opportunity for the improved management of water resources in headwater basins. Issues currently limiting full implementation of coupled-model methodologies include (a) the degree of uncertainty in the accuracy of precipitation and other meteorological variables simulated by atmospheric models, and (b) the problem of discordant scales between atmospheric and bydrological models. Alternative methodologies being developed to address these issues are reviewed.

  12. Using stable isotopes to determine sources of evaporated water to the atmosphere in the Amazon basin

    NASA Astrophysics Data System (ADS)

    Martinelli, Luiz Antonio; Victoria, Reynaldo Luiz; Silveira Lobo Sternberg, Leonel; Ribeiro, Aristides; Zacharias Moreira, Marcelo

    1996-09-01

    The return of water in vapor form from the land to the atmosphere, via plant transpiration and evaporation, is fundamental for the maintenance of the regional water cycle in the Amazon basin. Whereas transpiration, the dominant process, has the extensive vegetation cover as a large single source, evaporation can have several sources, and their relative importance and location are poorly known. The isotopic composition (δ 18O and δD) of water from various sources was used to see whether or not specific sources of water vapor to the atmosphere could be determined. It is well established that natural waters fall on a line called the meteoric water line (MWL; the regression of δ 18O × δD), with slope equal to eight and an intercept equal to ten. When a water body loses water via evaporation the slope become smaller than eight, typically 5-6. We estimated the slope of the regression of δ 18O × δD for several potential sources. We analyzed 1273 samples: 500 of rainfall, 409 of river water, 134 of lake water, 164 of soil water, 40 of throughfall and stemflow water, and 26 of shallow ground-water. We found that large rivers and lakes are likely contributors of evaporated water to the atmosphere. However, as they cover only a small area of the basin, other sources are needed. Probably, evaporated water originates from several small sources that were not detected by the isotopic composition of our data.

  13. Water cycle dynamic increases resilience of vegetation under higher atmospheric carbon dioxide concentration

    NASA Astrophysics Data System (ADS)

    Lemordant, L. A.; Gentine, P.; Stéfanon, M.; Drobinski, P. J.; Fatichi, S.

    2015-12-01

    Plant stomata couple the energy, water and carbon cycles. Photosynthesis requires stomata to open to take up carbon dioxide. In the process water vapor is released as transpiration. As atmospheric CO2 concentration rises, for the same amount of CO2 uptake, less water vapor is transpired, translating into higher water use efficiency. Reduced water vapor losses will increase soil water storage if the leaf area coverage remains similar. This will in turn alter the surface energy partitioning: more heat will be dissipated as sensible heat flux, resulting in possibly higher surface temperatures. In contrast with this common hypothesis, our study shows that the water saved during the growing season by increased WUE can be mobilized by the vegetation and help reduce the maximum temperature of mid-latitude heat waves. The large scale meteorological conditions of 2003 are the basis of four regional model simulations coupling an atmospheric model to a surface model. We performed two simulations with respectively 2003 (CTL) and 2100 (FUT) atmospheric CO2 applied to both the atmospheric and surface models. A third (RAD) and a fourth (FER) simulations are run with 2100 CO2 concentration applied to respectively the atmospheric model only and the surface model only. RAD investigates the impact of the radiative forcing, and FER the response to vegetation CO2 fertilization. Our results show that the water saved through higher water use efficiency during the growing season enabled by higher atmospheric carbon dioxide concentrations helps the vegetation to cope during severe heat and dryness conditions in the summer of mid-latitude climate. These results demonstrate that consideration of the vegetation carbon cycle is essential to model the seasonal water cycle dynamic and land-atmosphere interactions, and enhance the accuracy of the model outputs especially for extreme events. They also have important implications for the future of agriculture, water resources management, ecosystems

  14. Simulating the Vapour Phase Air/Water Exchange of p,p′-DDE, p,p′-DDT, Lindane, and 2,3,7,8-Tetrachlorodibenzodioxin

    EPA Science Inventory

    Uncertainties in our understanding of gaseous air/water exchange have emerged as major sources of concern in efforts to construct global and regional mass balances of both the green house gas carbon dioxide and semi-volatile persistent, bioaccumulative and toxic chemicals. Hoff e...

  15. Leidenfrost point and estimate of the vapour layer thickness

    NASA Astrophysics Data System (ADS)

    Gianino, Concetto

    2008-11-01

    In this article I describe an experiment involving the Leidenfrost phenomenon, which is the long lifetime of a water drop when it is deposited on a metal that is much hotter than the boiling point of water. The experiment was carried out with high-school students. The Leidenfrost point is measured and the heat laws are used to estimate the thickness of the vapour layer, d≈0.06 mm, which prevents the drop from touching the hotplate.

  16. Relating GRACE terrestrial water storage variations to global fields of atmospheric forcing

    NASA Astrophysics Data System (ADS)

    Humphrey, Vincent; Gudmundsson, Lukas; Isabelle Seneviratne, Sonia

    2015-04-01

    Synoptic, seasonal and inter-annual fluctuations in atmospheric dynamics all influence terrestrial water storage, with impacts on ecosystems functions, human activities and land-climate interactions. Here we explore to which degree atmospheric variables can explain GRACE estimates of terrestrial water storage on different time scales. Since 2012, the most recent GRACE gravity field solutions (Release 05) can be used to monitor global changes in terrestrial water storage with an unprecedented level of accuracy over more than a decade. In addition, the release of associated gridded and post-processed products facilitates comparisons with other global datasets such as land surface model outputs or satellite observations. We investigate how decadal trends, inter-annual fluctuations as well as monthly anomalies of the seasonal cycle of terrestrial water storage can be related to fields of atmospheric forcing, including e.g. precipitation and temperature as estimated in global reanalysis products using statistical techniques. In the majority of the locations with high signal to noise ratio, both short and long-term fluctuations of total terrestrial water storage can be reconstructed to a large degree based on available atmospheric forcing. However, in some locations atmospheric forcing alone is not sufficient to explain the total change in water storage, suggesting strong influence of other processes. Within that framework, the question of an amplification or attenuation of atmospheric forcing through land-surface feedbacks and changes in long term water storage is discussed, also with respect to uncertainties and potential systematic biases in the results.

  17. The Interaction of Spacecraft Cabin Atmospheric Quality and Water Processing System Performance

    NASA Technical Reports Server (NTRS)

    Perry, Jay L.; Croomes, Scott D. (Technical Monitor)

    2002-01-01

    Although designed to remove organic contaminants from a variety of waste water streams, the planned U.S.- and present Russian-provided water processing systems onboard the International Space Station (ISS) have capacity limits for some of the more common volatile cleaning solvents used for housekeeping purposes. Using large quantities of volatile cleaning solvents during the ground processing and in-flight operational phases of a crewed spacecraft such as the ISS can lead to significant challenges to the water processing systems. To understand the challenges facing the management of water processing capacity, the relationship between cabin atmospheric quality and humidity condensate loading is presented. This relationship is developed as a tool to determine the cabin atmospheric loading that may compromise water processing system performance. A comparison of cabin atmospheric loading with volatile cleaning solvents from ISS, Mir, and Shuttle are presented to predict acceptable limits to maintain optimal water processing system performance.

  18. Performance modeling of ultraviolet Raman lidar systems for daytime profiling of atmospheric water vapor

    NASA Technical Reports Server (NTRS)

    Ferrare, R. A.; Whiteman, D. N.; Melfi, S. H.; Goldsmith, J. E. M.; Bisson, S. E.; Lapp, M.

    1991-01-01

    We describe preliminary results from a comprehensive computer model developed to guide optimization of a Raman lidar system for measuring daytime profiles of atmospheric water vapor, emphasizing an ultraviolet, solar-blind approach.

  19. A simplified method to estimate atmospheric water vapor using MODIS near-infrared data

    NASA Astrophysics Data System (ADS)

    Wang, Xinming; Gu, Xiaoping; Wu, Zhanping

    2016-03-01

    Atmospheric water vapor plays a significant role in the study of climate change and hydrological cycle processes. In order to acquire the accurate distribution of atmospheric water vapor which is varying with time, location, and altitude, it is necessary to monitor it at high spatial and temporal resolution. Unfortunately, it is difficult to map the spatial distribution of atmospheric water vapor due to the lack of meteorological instrumentation at adequate spatial and temporal observation scales. This paper introduces a simplified method to retrieve Precipitable Water Vapor (PWV) using the ratio of the apparent reflectance values of the 18th and 19th band of Moderate Resolution Imaging Spectroradiometer (MODIS). Compared to the EOS PWV products of the same time and area, the PWV estimated using this simplified method is closer to the radiosonde results which is considered as the true PWV value. Results reveal that this simplified method is applicable over cloud-free atmospheric conditions of the mid-latitude regions.

  20. Contamination of surface-water bodies after reactor accidents by the erosion of atmospherically deposited radionuclides.

    PubMed

    Helton, J C; Muller, A B; Bayer, A

    1985-06-01

    Reactor safety analyses usually do not consider the population risk which might result from the contamination of surface-water bodies after reactor accidents by the erosion of atmospherically deposited radionuclides. This paper is intended to provide perspective on the reasonableness of this omission. Data are presented which are suggestive of the rates at which atmospherically deposited radionuclides might erode into surface-water bodies. These rates are used in the calculation of potential health effects resulting from surface-water contamination due to such erosion. These health effects are compared with predicted health effects due to atmospheric and terrestrial pathways after reactor accidents. The presented results support the belief that the contamination of surface-water bodies after reactor accidents by the erosion of atmospherically deposited radionuclides is not a major contributor to the risk associated with such accidents. PMID:3997527

  1. Atmospheric moisture transport and fresh water flux over oceans derived from spacebased sensors

    NASA Technical Reports Server (NTRS)

    Liu, W. T.; Tang, W.

    2001-01-01

    preliminary results will be shown to demonstrate the application of spacebased IMT and fresh water flux in ocean-atmosphere-land interaction studies, such as the hydrologica balance on Amazon rainfall and Indian monsoon.

  2. Stratospheric Temperatures and Water Loss from Moist Greenhouse Atmospheres of Earth-like Planets

    NASA Astrophysics Data System (ADS)

    Kasting, James F.; Chen, Howard; Kopparapu, Ravi K.

    2015-11-01

    A radiative-convective climate model is used to calculate stratospheric temperatures and water vapor concentrations for ozone-free atmospheres warmer than that of modern Earth. Cold, dry stratospheres are predicted at low surface temperatures, in agreement with recent 3D calculations. However, at surface temperatures above 350 K, the stratosphere warms and water vapor becomes a major upper atmospheric constituent, allowing water to be lost by photodissociation and hydrogen escape. Hence, a moist greenhouse explanation for loss of water from Venus, or some exoplanet receiving a comparable amount of stellar radiation, remains a viable hypothesis. Temperatures in the upper parts of such atmospheres are well below those estimated for a gray atmosphere, and this factor should be taken into account when performing inverse climate calculations to determine habitable zone boundaries using 1D models.

  3. Atmospheric water balance over oceanic regions as estimated from satellite, merged, and reanalysis data

    NASA Astrophysics Data System (ADS)

    Park, Hyo-Jin; Shin, Dong-Bin; Yoo, Jung-Moon

    2013-05-01

    The column integrated atmospheric water balance over the ocean was examined using satellite-based and merged data sets for the period from 2000 to 2005. The data sets for the components of the atmospheric water balance include evaporation from the HOAPS, GSSTF, and OAFlux and precipitation from the HOAPS, CMAP, and GPCP. The water vapor tendency was derived from water vapor data of HOAPS. The product for water vapor flux convergence estimated using satellite observation data was used. The atmospheric balance components from the MERRA reanalysis data were also examined. Residuals of the atmospheric water balance equation were estimated using nine possible combinations of the data sets over the ocean between 60°N and 60°S. The results showed that there was considerable disagreement in the residual intensities and distributions from the different combinations of the data sets. In particular, the residuals in the estimations of the satellite-based atmospheric budget appear to be large over the oceanic areas with heavy precipitation such as the intertropical convergence zone, South Pacific convergence zone, and monsoon regions. The lack of closure of the atmospheric water cycle may be attributed to the uncertainties in the data sets and approximations in the atmospheric water balance equation. Meanwhile, the anomalies of the residuals from the nine combinations of the data sets are in good agreement with their variability patterns. These results suggest that significant consideration is needed when applying the data sets of water budget components to quantitative water budget studies, while climate variability analysis based on the residuals may produce similar results.

  4. Multi-year GNSS monitoring of atmospheric IWV over Central and South America for climate studies

    NASA Astrophysics Data System (ADS)

    Bianchi, Clara Eugenia; Mendoza, Luciano Pedro Oscar; Fernández, Laura Isabel; Natali, María Paula; Meza, Amalia Margarita; Francisco Moirano, Juan

    2016-07-01

    Atmospheric water vapour has been acknowledged as an essential climate variable. Weather prediction and hazard assessment systems benefit from real-time observations, whereas long-term records contribute to climate studies. Nowadays, ground-based global navigation satellite system (GNSS) products have become widely employed, complementing satellite observations over the oceans. Although the past decade has seen a significant development of the GNSS infrastructure in Central and South America, its potential for atmospheric water vapour monitoring has not been fully exploited. With this in mind, we have performed a regional, 7-year-long and homogeneous analysis, comprising 136 GNSS tracking stations, obtaining high-rate and continuous observations of column-integrated water vapour and troposphere zenith total delay. As a preliminary application for this data set, we have estimated local water vapour trends, their significance, and their relation with specific climate regimes. We have found evidence of drying at temperate regions in South America, at a rate of about 2 % per decade, while a slow moistening of the troposphere over tropical regions is also weakly suggested by our results. Furthermore, we have assessed the regional performance of the empirical model GPT2w to blindly estimate troposphere delays. The model reproduces the observed mean delays fairly well, including their annual and semi-annual variations. Nevertheless, a long-term evaluation has shown systematical biases, up to 20 mm, probably inherited from the underlying atmospheric reanalysis. Additionally, the complete data set has been made openly available as supplementary material.

  5. Hoplia coerulea, a porous natural photonic structure as template of optical vapour sensor

    NASA Astrophysics Data System (ADS)

    Mouchet, Sébastien; Su, Bao-Lian; Tabarrant, Tijani; Lucas, Stéphane; Deparis, Olivier

    2013-05-01

    Natural photonic structures found on the cuticle of insects are known to give rise to astonishing structural colours. These ordered porous structures are made of biopolymers, such as chitin, and some of them possess the property to change colour according to the surrounding atmosphere composition. This phenomenon is still not completely understood. We investigated the structure found on the cuticle of the male beetle Hoplia coerulea (Scarabaeidae). The structure, in this case, consists in a 1D periodic porous multilayer inside scales, reflecting incident light in the blue. The colour variations were quantified by reflectance spectral measurements using water, ethanol and acetone vapours. A 1D scattering matrix formalism was used for modelling light reflection on the photonic multilayer. The origin of the reported colour changes has to be tracked in variations of the effective refractive index and of the photonic structure dimensions. This remarkable phenomenon observed for a non-open but still porous multilayer could be very interesting for vapour sensing applications and smart glass windows.

  6. Investigating the Source, Transport, and Isotope Composition of Water in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Griffis, T. J.; Schultz, N. M.; Lee, X.

    2011-12-01

    The isotope composition of water (liquid and vapor phases) can provide important insights regarding the source of water used by plants, the origins of atmospheric water vapor, and the sources of carbon dioxide. In recent years there have been significant advances in the ability to quantify the isotope composition of water and water vapor using optical isotope techniques. We have used and helped develop some of these techniques to determine the isotope composition of soil and plant waters, to measure the isoflux of water vapor between the land surface and atmosphere, and to examine the isotope composition of water vapor and deuterium excess in the atmospheric boundary layer. In this presentation we will discuss three related issues: 1) Identification and correction of spectral contamination in soil and plant water samples using optical techniques; 2) The benefits and practical limitations of quantifying the isotope composition of evapotranspiration using the eddy covariance approach; and 3) The scientific value and feasibility of tracking the long-term (seasonal and interannual) behavior of the isotope composition of water vapor and deuterium excess in the atmospheric boundary layer. A few short stories will be provided from experiments conducted in the lab, at the field scale, and from a very tall tower at the University of Minnesota from 2008 to 2011.

  7. Rate constant for the reaction of OH with methyl iodide, a re-determination by flash photolysis of water vapour and time resolved resonance fluorescence of OH

    NASA Astrophysics Data System (ADS)

    Zhang, Shaoliang; Strekowski, Rafal; Zetzsch, Cornelius

    2010-05-01

    Methyl iodide is a major source gas for atmospheric iodine, and it is mainly emitted from the ocean. Aqueous-phase reactions, such as hydrolysis and exchange reactions with chloride control its emissions to the atmosphere, where its lifetime is limited to less than a week, mainly by photolysis. A minor contribution to the loss processes in the troposphere is the gas-phase reaction with OH radicals, that has been investigated by several authors. On the other hand, this reaction turned out to be uncertain in spite of interest in nuclear safety after the International Phebus Fission Product programme, initiated in 1988. Some of the most important observed phenomena with regard to the chemistry of iodine were not predicted, clearly showing the need for carrying out rate constant determinations for the reactions of I2 and CH3I with OH, which is a major oxidant product from the air radiolysis under accident conditions. We have measured the rate constant for the reaction OH + CH3I - H2O + CH2I in He at 260 mbar in the temperature range from 298 to 362 K. OH radicals were produced by flash photolysis of H2O in the vacuum-UV at wavelengths > 115 nm using a Xe flash lamp with a MgF2 window. Time profiles of OH radicals are monitored by resonance fluorescence of the A2 Σ - X2 Π transition at 308 nm, induced by the emission from a microwave discharge of a flow of He and H2O, a few Torr each. The signal is monitored by photon counting and multichannel scaling, collecting the counts from 50 flashes each, obtaind by pulsed photolysis of various mixtures of H2O and CH3I under slow-flow conditions. Decays of OH in the presence of CH3I are observed to be exponential, and the decay rates are found to be linearly dependent on the concentration of CH3I. Rate constants, k ± 2σ (in units of 10-14 cm3 s-1) of 4.14±0.20, 6.33±0.68, 7.31±1.18 and 8.24±1.60 at 298, 326, 352 and 362 K, respectively, are obtained from linear regressions and lead to an Arrhenius expression of k = 1.5

  8. Carbon Dioxide in Exoplanetary Atmospheres: Rarely Dominant Compared to Carbon Monoxide and Water in Hot, Hydrogen-dominated Atmospheres

    NASA Astrophysics Data System (ADS)

    Heng, Kevin; Lyons, James R.

    2016-02-01

    We present a comprehensive study of the abundance of carbon dioxide in exoplanetary atmospheres in hot, hydrogen-dominated atmospheres. We construct novel analytical models of systems in chemical equilibrium that include carbon monoxide, carbon dioxide, water, methane and acetylene and relate the equilibrium constants of the chemical reactions to temperature and pressure via the tabulated Gibbs free energies. We prove that such chemical systems may be described by a quintic equation for the mixing ratio of methane. By examining the abundances of these molecules across a broad range of temperatures (spanning equilibrium temperatures from 600 to 2500 K), pressures (via temperature-pressure profiles that explore albedo and opacity variations) and carbon-to-oxygen ratios, we conclude that carbon dioxide is subdominant compared to carbon monoxide and water. Atmospheric mixing does not alter this conclusion if carbon dioxide is subdominant everywhere in the atmosphere. Carbon dioxide and carbon monoxide may attain comparable abundances if the metallicity is greatly enhanced, but this property is negated by temperatures above 1000 K. For hydrogen-dominated atmospheres, our generic result has the implication that retrieval studies may wish to set the subdominance of carbon dioxide as a prior of the calculation and not let its abundance completely roam free as a fitting parameter, because it directly affects the inferred value of the carbon-to-oxygen ratio and may produce unphysical conclusions. We discuss the relevance of these implications for the hot Jupiter WASP-12b and suggest that some of the previous results are chemically impossible. The relative abundance of carbon dioxide to acetylene is potentially a sensitive diagnostic of the carbon-to-oxygen ratio.

  9. Atmospheric water mapping with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), Mountain Pass, California

    NASA Technical Reports Server (NTRS)

    Conel, James E.; Green, Robert O.; Carrere, Veronique; Margolis, Jack S.; Alley, Ronald E.; Vane, Gregg; Bruegge, Carol J.; Gary, Bruce L.

    1988-01-01

    Observations are given of the spatial variation of atmospheric precipitable water using the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) over a desert area in eastern California, derived using a band ratio method and the 940 nm atmospheric water band and 870 nm continuum radiances. The ratios yield total path water from curves of growth supplied by the LOWTRAN 7 atmospheric model. An independent validation of the AVIRIS-derived column abundance at a point is supplied by a spectral hygrometer calibrated with respect to radiosonde observations. Water values conform to topography and fall off with surface elevation. The edge of the water vapor boundary layer defined by topography is thought to have been recovered. The ratio method yields column abundance estimates of good precision and high spatial resolution.

  10. Modelling tritium flux from water to atmosphere: application to the Loire River.

    PubMed

    Marang, L; Siclet, F; Luck, M; Maro, D; Tenailleau, L; Jean-Baptiste, P; Fourré, E; Fontugne, M

    2011-03-01

    Tritium (³H or T) is one of the major radionuclides released by nuclear power plants (NPP) into rivers. However, tritiated water (HTO) flux from water to air is seldom considered when assessing health effects of such releases. The aim of this paper is to present the result of a research program, called LORA, conducted on the Loire River (France). To improve our understanding of HTO flux from surface water to air, three field campaigns were organised during the NPP's radioactive releases to measure simultaneously the activity concentrations in air on the riverbank, using an innovative system, and in river water. The measurements showed that during radioactive releases, water vapour was enriched in ³H. These results were used to calibrate exchange velocities. The average of these estimated exchange velocities was more than one order of magnitude higher than those calculated in the literature from indoor experiments. The variability of these values was also larger, showing that outdoor studies cover a wide range of conditions influencing HTO flux. No correlation was observed between exchanges velocities and meteorological conditions. However, there was a significant difference between day and night with a higher value observed during the day. Two approaches used to calculate HTO evaporation from water (i.e. the approach based on water evaporation and the approach considering that HTO follows its own concentration gradient) were included in a hydrodynamic model, which was used to evaluate HTO air activity along the Loire River. In conclusion, only the approach considering that HTO follows its own gradient led to a good agreement between measurements and predictions. A one-year simulation was done to estimate the contribution of this process to the dose. Its contribution can be considered as negligible in this case compared to the other pathways such as ingestion of water or foodstuffs. PMID:21255883

  11. Vapor hydrogen and oxygen isotopes reflect water of combustion in the urban atmosphere.

    PubMed

    Gorski, Galen; Strong, Courtenay; Good, Stephen P; Bares, Ryan; Ehleringer, James R; Bowen, Gabriel J

    2015-03-17

    Anthropogenic modification of the water cycle involves a diversity of processes, many of which have been studied intensively using models and observations. Effective tools for measuring the contribution and fate of combustion-derived water vapor in the atmosphere are lacking, however, and this flux has received relatively little attention. We provide theoretical estimates and a first set of measurements demonstrating that water of combustion is characterized by a distinctive combination of H and O isotope ratios. We show that during periods of relatively low humidity and/or atmospheric stagnation, this isotopic signature can be used to quantify the concentration of water of combustion in the atmospheric boundary layer over Salt Lake City. Combustion-derived vapor concentrations vary between periods of atmospheric stratification and mixing, both on multiday and diurnal timescales, and respond over periods of hours to variations in surface emissions. Our estimates suggest that up to 13% of the boundary layer vapor during the period of study was derived from combustion sources, and both the temporal pattern and magnitude of this contribution were closely reproduced by an independent atmospheric model forced with a fossil fuel emissions data product. Our findings suggest potential for water vapor isotope ratio measurements to be used in conjunction with other tracers to refine the apportionment of urban emissions, and imply that water vapor emissions associated with combustion may be a significant component of the water budget of the urban boundary layer, with potential implications for urban climate, ecohydrology, and photochemistry. PMID:25733906

  12. A Plant-Based Proxy for the Oxygen Isotope Ratio of Atmospheric Water Vapor

    NASA Astrophysics Data System (ADS)

    Helliker, B.

    2007-12-01

    Atmospheric water vapor is a major component of the global hydrological cycle, but the isotopic balance of vapor is largely unknown. It is shown here that the oxygen isotope ratio of leaf water in the epiphytic Crassulacean acid metabolism (CAM) plant Tillandsia usneoides (Spanish Moss) is controlled by the oxygen isotope ratio of atmospheric water vapor in both field and lab studies. Assuming that the leaf-water isotopic signature (and hence the atmospheric water vapor signature) is recorded in plant organic material, the atmospheric water vapor oxygen isotope ratios for Miami, Florida (USA) were reconstructed for several years from 1878 to 2005 using contemporary and herbarium specimens. T. usneoides ranges from Virginia, USA southwards through the tropics to Argentina, and the CAM epiphytic lifeform is widespread in other species. Therefore, epiphytes may be used to reconstruct the isotope ratio of atmospheric water for spatial scales that span over 60° of latitude and temporal scales that cover the last century of global temperature increase.

  13. Vapor hydrogen and oxygen isotopes reflect water of combustion in the urban atmosphere

    PubMed Central

    Gorski, Galen; Strong, Courtenay; Good, Stephen P.; Bares, Ryan; Ehleringer, James R.; Bowen, Gabriel J.

    2015-01-01

    Anthropogenic modification of the water cycle involves a diversity of processes, many of which have been studied intensively using models and observations. Effective tools for measuring the contribution and fate of combustion-derived water vapor in the atmosphere are lacking, however, and this flux has received relatively little attention. We provide theoretical estimates and a first set of measurements demonstrating that water of combustion is characterized by a distinctive combination of H and O isotope ratios. We show that during periods of relatively low humidity and/or atmospheric stagnation, this isotopic signature can be used to quantify the concentration of water of combustion in the atmospheric boundary layer over Salt Lake City. Combustion-derived vapor concentrations vary between periods of atmospheric stratification and mixing, both on multiday and diurnal timescales, and respond over periods of hours to variations in surface emissions. Our estimates suggest that up to 13% of the boundary layer vapor during the period of study was derived from combustion sources, and both the temporal pattern and magnitude of this contribution were closely reproduced by an independent atmospheric model forced with a fossil fuel emissions data product. Our findings suggest potential for water vapor isotope ratio measurements to be used in conjunction with other tracers to refine the apportionment of urban emissions, and imply that water vapor emissions associated with combustion may be a significant component of the water budget of the urban boundary layer, with potential implications for urban climate, ecohydrology, and photochemistry. PMID:25733906

  14. Atmospheric correction of aviris data in ocean waters. Final report

    SciTech Connect

    Terrie, G.; Armone, R.

    1992-06-01

    Hyperspectral data offers unique capabilities for characterizing the ocean environment. The spectral characterization of the composition of ocean waters can be organized into biological and terrigenous components. Biological photosynthetic pigments in ocean waters have unique spectral ocean color signatures which can be associated with different biological species. Additionally, suspended sediment has different scattering coefficients which result in ocean color signatures. Measuring the spatial distributions of these components in the maritime environments provides important tools for understanding and monitoring the ocean environment. These tools have significant applications in pollution, carbon cycle, current and water mass detection, location of fronts and eddies, sewage discharge and fate etc.

  15. No sodium in the vapour plumes of Enceladus.

    PubMed

    Schneider, Nicholas M; Burger, Matthew H; Schaller, Emily L; Brown, Michael E; Johnson, Robert E; Kargel, Jeffrey S; Dougherty, Michele K; Achilleos, Nicholas A

    2009-06-25

    The discovery of water vapour and ice particles erupting from Saturn's moon Enceladus fuelled speculation that an internal ocean was the source. Alternatively, the source might be ice warmed, melted or crushed by tectonic motions. Sodium chloride (that is, salt) is expected to be present in a long-lived ocean in contact with a rocky core. Here we report a ground-based spectroscopic search for atomic sodium near Enceladus that places an upper limit on the mixing ratio in the vapour plumes orders of magnitude below the expected ocean salinity. The low sodium content of escaping vapour, together with the small fraction of salt-bearing particles, argues against a situation in which a near-surface geyser is fuelled by a salty ocean through cracks in the crust. The lack of observable sodium in the vapour is consistent with a wide variety of alternative eruption sources, including a deep ocean, a freshwater reservoir, or ice. The existing data may be insufficient to distinguish between these hypotheses. PMID:19553993

  16. Time-dependent calculations of molten pool formation and thermal plasma with metal vapour in gas tungsten arc welding

    NASA Astrophysics Data System (ADS)

    Tanaka, M.; Yamamoto, K.; Tashiro, S.; Nakata, K.; Yamamoto, E.; Yamazaki, K.; Suzuki, K.; Murphy, A. B.; Lowke, J. J.

    2010-11-01

    A gas tungsten arc (GTA) was modelled taking into account the contamination of the plasma by metal vapour from the molten anode. The whole region of GTA atmosphere including the tungsten cathode, the arc plasma and the anode was treated using a unified numerical model. A viscosity approximation was used to express the diffusion coefficient in terms of viscosity of the shielding gas and metal vapour. The transient two-dimensional distributions of temperature, velocity of plasma flow and iron vapour concentration were predicted, together with the molten pool as a function of time for a 150 A arc current at atmospheric pressure, both for helium and argon gases. It was shown that the thermal plasma in the GTA was influenced by iron vapour from the molten pool surface and that the concentration of iron vapour in the plasma was dependent on the temperature of the molten pool. GTA on high sulfur stainless steel was calculated to discuss the differences between a low sulfur and a high sulfur stainless steel anode. Helium was selected as the shielding gas because a helium GTA produces more metal vapour than an argon GTA. In the GTA on a high sulfur stainless steel anode, iron vapour and current path were constricted. Radiative emission density in the GTA on high sulfur stainless steel was also concentrated in the centre area of the arc plasma together with the iron vapour although the temperature distributions were almost the same as that in the case of a low sulfur stainless steel anode.

  17. The effect of atmospheric water vapor on automatic classification of ERTS data

    NASA Technical Reports Server (NTRS)

    Pitts, D. E.; Mcallum, W. E.; Dillinger, A. E.

    1974-01-01

    Absorption by atmospheric water vapor changes the spectral signatures collected by multispectral scanners if channels are not chosen to avoid the atmospheric water bands. For ERTS (Earth Resources Technology Satellite), the Multispectral Scanner band 7 (MSS 7, .8 to 1.1 micron) is the only band significantly affected. Line-by-line atmospheric absorption calculations showed that this effect can multiply the intensity by factors ranging from .77 to 1.0. If horizontal gradients in atmospheric water exist between training fields and the rest of the scene, errors are introduced in automatic classification of the imagery. The degradation of the classification of corn and soybeans was determined by using actual ERTS data and simulating the absorption effects on the MSS 7 band.

  18. Retrieval of water vapor profiles from atmospheric radio-occultations

    NASA Technical Reports Server (NTRS)

    Juarez, M. de la Torre; Nilsson, P. M.

    2002-01-01

    We illustrate a novel method to extract water vapor with high vertical resolution, using the refractivity profiles without ancillary data. We also discuss the estimated accuracies and sources of error.

  19. Characteristics of turbulence driven atmospheric blur over coastal water

    NASA Astrophysics Data System (ADS)

    de Jong, Arie N.; Schwering, Piet B. W.; Benoist, Koen W.; Gunter, Willem H.; Vrahimis, George; October, Faith J.

    2014-10-01

    For users of Electro-Optical (EO) sensors at sea, knowledge on their resolution is of key operational importance for the prediction of the obtainable classification ranges. Small targets may be located at ranges of 20 km and more and the present day sensor pixel size may be as small as 10 μrad. In this type of scenarios, sensor resolution will be limited by blur, generated by atmospheric turbulence, easily being greater than 30 μrad (at 20 km range). Predictions of the blur size are generally based upon the theory, developed by Fried [1]. In this theory, the turbulence strength is characterized by the structure parameter for the refractive index Cn 2, of which data are assumed to be available from secondary instruments. The theory predicts the atmospheric Modulation Transfer Function (MTF), which can be incorporated into the total system MTF, used in range performance predictions, as described by Holst [2]. Validation of blur predictions by measurements is a complex effort due to the rapid variations of the blur with time and the problems associated with the simultaneous acquisition of proper Cn 2 data. During the FATMOSE trial, carried out over a range of 15.7 km in the False Bay near Simon's Town (South Africa) from November 2009 to October 2010, these data were collected in a large variety of atmospheric conditions [3]. In stead of the atmospheric MTF, the horizontal and vertical line spread function (LSF) was measured with a camera with 5 μrad resolution. Various methods for the determination of the LSF and the associated problems are discussed in the paper. The width of the LSF is via its Fourier transform directly related to the MTF. Cn 2 data were collected with a standard BLS scintillometer over a nearby range. Additional Cn 2 data were obtained via conversion of the scintillation data from the same camera and from a high speed transmissometer, collecting data over the same range. Comparisons between blur and Beam Wander predictions and measurements from

  20. Numerical implementation and oceanographic application of the thermodynamic potentials of water, vapour, ice, seawater and air - Part 2: The library routines

    NASA Astrophysics Data System (ADS)

    Wright, D. G.; Feistel, R.; Reissmann, J. H.; Miyagawa, K.; Jackett, D. R.; Wagner, W.; Overhoff, U.; Guder, C.; Feistel, A.; Marion, G. M.

    2010-03-01

    The SCOR/IAPSO1 Working Group 127 on Thermodynamics and Equation of State of Seawater has prepared recommendations for new methods and algorithms for numerical estimation of the thermophysical properties of seawater. As an outcome of this work, a new International Thermodynamic Equation of Seawater (TEOS-10) was endorsed by IOC/UNESCO2 in June 2009 as the official replacement and extension of the 1980 International Equation of State, EOS-80. As part of this new standard a source code package has been prepared that is now made freely available to users via the World Wide Web. This package includes two libraries referred to as the SIA (Sea-Ice-Air) library and the GSW (Gibbs SeaWater) library. Information on the GSW library may be found on the TEOS-10 web site (http://www.TEOS-10.org). This publication provides an introduction to the SIA library which contains routines to calculate various thermodynamic properties as discussed in the companion paper. The SIA library is very comprehensive, including routines to deal with fluid water, ice, seawater and humid air as well as equilibrium states involving various combinations of these, with equivalent code developed in different languages. The code is hierachically structured in modules that support (i) almost unlimited extension with respect to additional properties or relations, (ii) an extraction of self-contained sub-libraries, (iii) separate updating of the empirical thermodynamic potentials, and (iv) code verification on different platforms and between different languages. Error trapping is implemented to identify when one or more of the primary routines are accessed significantly beyond their established range of validity. The initial version of the SIA library is available in Visual Basic and FORTRAN as a supplement to this publication and updates will be maintained on the TEOS-10 web site. 1 SCOR/IAPSO: Scientific Committee on Oceanic Research

  1. A new look at the atmospheric water cycle: measurements of water vapor and its main isotopologue using SCIAMACHY

    NASA Astrophysics Data System (ADS)

    Scheepmaker, Remco; Frankenberg, Christian; Aben, Ilse; Schrijver, Hans; Gloudemans, Annemieke; Roeckmann, Thomas; Yoshimura, Kei

    2010-05-01

    Water vapor is by far the most important greenhouse gas in the atmosphere. As a warmer atmosphere can contain more water vapor, a positive feedback effect with respect to climate change is expected. The distribution of water vapor is very inhomogeneous and variable, unlike that of other greenhouse gases. In the light of climate reconstructions and predictions, it is therefore crucial to better understand the water cycle and its response to past and present climate change. The relative abundance of the heavy water isotopologue HDO provides a deeper insight in the water cycle, as evaporation and condensation processes deplete heavy water in the gas phase. In the application of isotopologues, however, the space-borne retrieval of atmospheric water vapor isotopologues near the surface has so far been overlooked. We provide, for the first time (Frankenberg et al., Science 2009), global HDO/H2O abundances using the Scanning Imaging Absorption spectroMeter for Atmospheric CHartography (SCIAMACHY) instrument onboard ENVISAT. This allows for an entirely new perspective on the near-surface distribution of water vapor isotopologues. We are using the 2.3 micron (SWIR) window of SCIAMACHY, which is also used for the first time (Schrijver et al., AMT 2009) to derive total water vapor columns. Because of this wavelength range, and because SCIAMACHY is an absorption spectrometer, we are sensitive down to the lowest parts of the atmosphere where most of the water vapor resides. We further exploit a novel method to correct for the scattering effects of an ice layer on the SWIR detector and in order to further improve the accuracy of our HDO/H2O dataset, we derived an improved spectral linelist for H2O in the 2.3 micron window. The total water vapor columns have been validated with collocated ECMWF data and show good agreement. First results of atmospheric HDO/H2O show an expected latitudinal gradient, but also strong evaporation signals over the Red Sea and highly depleted values

  2. Impact of soil water property parameterization on atmospheric boundary layer simulation

    NASA Astrophysics Data System (ADS)

    Cuenca, Richard H.; Ek, Michael; Mahrt, Larry

    1996-03-01

    Both the form of functional relationships applied for soil water properties and the natural field-scale variability of such properties can significantly impact simulation of the soil-plant-atmosphere system on a diurnal timescale. Various input parameters for soil water properties including effective saturation, residual water content, anerobiosis point, field capacity, and permanent wilting point are incorporated into functions describing soil water retention, hydraulic conductivity, diffusivity, sorptivity, and the plant sink function. The perception of the meaning of these values and their variation within a natural environment often differs from the perspective of the soil physicist, plant physiologist, and atmospheric scientist. This article investigates the sensitivity of energy balance and boundary layer simulation to different soil water property functions using the Oregon State University coupled atmosphere-plant-soil (CAPS) simulation model under bare soil conditions. The soil parameterizations tested in the CAPS model include those of Clapp and Hornberger [1978], van Genuchten [1980], and Cosby et al. [1984] using initial atmospheric conditions from June 16, 1986 in Hydrologic Atmospheric Pilot Experiment-Modélisation du Bilan Hydrique (HAPEX-MOBILHY). For the bare soil case these results demonstrate unexpected model sensitivity to soil water property parameterization in partitioning all components of the diurnal energy balance and corresponding boundary layer development.

  3. The interpretation of data from the Viking Mars Atmospheric Water Detectors (MAWD): Some points for discussion

    NASA Technical Reports Server (NTRS)

    Clifford, Stephen M.

    1988-01-01

    Properly interpreted, water vapor column abundance measurements can provide important insights into many of the processes that govern the diurnal, seasonal, and climatic cycles of atmospheric water on Mars. The uncertain distribution of water vapor complicates this analysis. It is argued that if a significant fraction of the total atmospheric vapor content is concentrated within the lowermost scale height, then the hemispheric asymmetry in zonally averaged topography/air mass might itself explain the observed gradient in the annual and zonally averaged vapor abundance.

  4. Water cycles in closed ecological systems: effects of atmospheric pressure

    NASA Technical Reports Server (NTRS)

    Rygalov, Vadim Y.; Fowler, Philip A.; Metz, Joannah M.; Wheeler, Raymond M.; Bucklin, Ray A.; Sager, J. C. (Principal Investigator)

    2002-01-01

    In bioregenerative life support systems that use plants to generate food and oxygen, the largest mass flux between the plants and their surrounding environment will be water. This water cycle is a consequence of the continuous change of state (evaporation-condensation) from liquid to gas through the process of transpiration and the need to transfer heat (cool) and dehumidify the plant growth chamber. Evapotranspiration rates for full plant canopies can range from 1 to 10 L m-2 d-1 (1 to 10 mm m-2 d-1), with the rates depending primarily on the vapor pressure deficit (VPD) between the leaves and the air inside the plant growth chamber. VPD in turn is dependent on the air temperature, leaf temperature, and current value of relative humidity (RH). Concepts for developing closed plant growth systems, such as greenhouses for Mars, have been discussed for many years and the feasibility of such systems will depend on the overall system costs and reliability. One approach for reducing system costs would be to reduce the operating pressure within the greenhouse to reduce structural mass and gas leakage. But managing plant growth environments at low pressures (e.g., controlling humidity and heat exchange) may be difficult, and the effects of low-pressure environments on plant growth and system water cycling need further study. We present experimental evidence to show that water saturation pressures in air under isothermal conditions are only slightly affected by total pressure, but the overall water flux from evaporating surfaces can increase as pressure decreases. Mathematical models describing these observations are presented, along with discussion of the importance for considering "water cycles" in closed bioregenerative life support systems.

  5. Water cycles in closed ecological systems: effects of atmospheric pressure.

    PubMed

    Rygalov, Vadim Y; Fowler, Philip A; Metz, Joannah M; Wheeler, Raymond M; Bucklin, Ray A

    2002-01-01

    In bioregenerative life support systems that use plants to generate food and oxygen, the largest mass flux between the plants and their surrounding environment will be water. This water cycle is a consequence of the continuous change of state (evaporation-condensation) from liquid to gas through the process of transpiration and the need to transfer heat (cool) and dehumidify the plant growth chamber. Evapotranspiration rates for full plant canopies can range from ~1 to 10 L m-2 d-1 (~1 to 10 mm m-2 d-1), with the rates depending primarily on the vapor pressure deficit (VPD) between the leaves and the air inside the plant growth chamber. VPD in turn is dependent on the air temperature, leaf temperature, and current value of relative humidity (RH). Concepts for developing closed plant growth systems, such as greenhouses for Mars, have been discussed for many years and the feasibility of such systems will depend on the overall system costs and reliability. One approach for reducing system costs would be to reduce the operating pressure within the greenhouse to reduce structural mass and gas leakage. But managing plant growth environments at low pressures (e.g., controlling humidity and heat exchange) may be difficult, and the effects of low-pressure environments on plant growth and system water cycling need further study. We present experimental evidence to show that water saturation pressures in air under isothermal conditions are only slightly affected by total pressure, but the overall water flux from evaporating surfaces can increase as pressure decreases. Mathematical models describing these observations are presented, along with discussion of the importance for considering "water cycles" in closed bioregenerative life support systems. PMID:12481804

  6. Water in the atmosphere of HD 209458b from 3.6-8 μm IRAC photometric observations in primary transit

    NASA Astrophysics Data System (ADS)

    Beaulieu, J. P.; Kipping, D. M.; Batista, V.; Tinetti, G.; Ribas, I.; Carey, S.; Noriega-Crespo, J. A.; Griffith, C. A.; Campanella, G.; Dong, S.; Tennyson, J.; Barber, R. J.; Deroo, P.; Fossey, S. J.; Liang, D.; Swain, M. R.; Yung, Y.; Allard, N.

    2010-12-01

    The hot Jupiter HD 209458b was observed during primary transit at 3.6, 4.5, 5.8 and 8.0 μm using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We describe the procedures we adopted to correct for the systematic effects present in the IRAC data and the subsequent analysis. The light curves were fitted including limb-darkening effects and fitted using Markov Chain Monte Carlo and prayer-bead Monte Carlo techniques, obtaining almost identical results. The final depth measurements obtained by a combined Markov Chain Monte Carlo fit are at 3.6 μm, 1.469 ± 0.013 and 1.448 ± 0.013 per cent; at 4.5 μm, 1.478 ± 0.017 per cent; at 5.8 μm, 1.549 ± 0.015 per cent; and at 8.0 μm, 1.535 ± 0.011 per cent. Our results clearly indicate the presence of water in the planetary atmosphere. Our broad-band photometric measurements with IRAC prevent us from determining the additional presence of other molecules such as CO, CO2 and methane for which spectroscopy is needed. While water vapour with a mixing ratio of ? combined with thermal profiles retrieved from the day side may provide a very good fit to our observations, this data set alone is unable to resolve completely the degeneracy between water abundance and atmospheric thermal profile.

  7. Coupling between plant leaf water and atmospheric vapor: insights from isotopic analyses

    NASA Astrophysics Data System (ADS)

    Rambo, J. P.; Lai, C.

    2012-12-01

    We measured stable isotopic composition of leaf water and atmospheric water vapor in an old growth forest in the Pacific Northwest of U.S.A. in the summer of 2011. A LGR cavity-enhanced absorption spectroscopy analyzer was used to measure hourly 18O/16O and 2H/1H ratios of atmospheric water vapor (δ18Ov and δDv) at three canopy heights (1m, 10m and 60m aboveground). Modeling studies show that transpiration plays an important role in controlling δ18Ov and δDv v