Increase In Water Vapor Content Research Articles

The increase of snowfall in Northeast China after the mid-1980s

We studied long-term variation of winter snowfall in Northeast China (NEC) for 1951–2010. Results show that NEC snowfall increased about 20% during 1986–2010 relative to 1951–1985. Further investigation suggests that the snowfall increase is closely associated with weakening of the East Asian winter monsoon (EAWM). The physical processes were portrayed by this research. Weakening of EAWM led to weakened cold air flow from the north, thus resulted in the warming of the surface ocean along the Northeast Asia coast and more water vapor evaporated from the ocean surface to the atmosphere and further transported to NEC. Also, because of EAWM weakening, more water vapor from south, east and west of NEC was transported to NEC, increasing water vapor content and hence snowfall there. From an atmospheric circulation viewpoint, EAWM weakening strengthened convergence at low levels and divergence at high levels, thereby favoring increased vertical convection and snowfall.

Increased water-vapor content in the atmosphere of tropical latitudes as a necessary condition for the genesis of tropical cyclones

The hypothesis about the interrelation of the integral water-vapor concentration (from data of microwave satellite systems) and plural tropical cyclogenesis in cyclonogenerating water areas of the World Ocean in 2001 is verified with the aid of the EVA-01 (IKI RAN) database (DB) with elements of the objectrelation type formed by the authors. It is experimentally proved in the work that there is a critical value of the integral water-vapor concentration (a peculiar necessary condition) at which the mature form of a tropical cyclone (TC) is formed with a lifetime exceeding 24 h. It is also experimentally proved that, in the same time interval, there is another group of TCs with a short lifetime (less than than 24 h) which do not possess a clearly pronounced boundary value of the water-vapor intensity and can be formed in a wide range of its values. The relations between the regions with an increased concentration of water vapor and genesis of TCs have become obvious only with the use of object-relation computer technologies.

Extratropical Influence on ITCZ Shifts in Slab Ocean Simulations of Global Warming

Abstract Recent studies with climate models have demonstrated the power of extratropical forcing in causing the intertropical convergence zone (ITCZ) to shift northward or southward, and paleoclimate data support the notion that there have been large shifts in the ITCZ over time. It is shown that similar notions apply to slab ocean simulations of global warming. Nine slab ocean model simulations from different modeling centers show a wide range of ITCZ shifts in response to doubling carbon dioxide concentrations, which are experienced in a rather zonally symmetric way in the tropics. Using an attribution strategy based on fundamental energetic constraints, it is shown that responses of clouds and ice in the extratropics explain much of the range of ITCZ responses. There are also some positive feedbacks within the tropics due to increasing water vapor content and high clouds in the new ITCZ location, which amplify the changes driven from the extratropics. This study shows the clear importance of simulating extratropical climate responses with fidelity, because in addition to their local importance, the impacts of these climate responses have a large nonlocal impact on rainfall in the tropics.

Oxidation of Hydrogen over Honeycomb Catalysts under the Presence of Water Vapor

Recovery of tritium released into working areas in nuclear fusion plants is a key issue for safety. A large volume of air in the last confinement of fusion power plants should be processed by air cleanup system (ACS). In ACS, tritium gas is oxidized by catalysts, and then tritiated water vapor is collected by adsorbents. This method can remove tritium effectively, whereas high throughput of air causes higher pressure loss in catalyst and adsorbent beds. The pressure loss can be reduced by replacing the packed bed of catalysts with the honeycomb catalysts. In this study, the oxidation experiments of hydrogen in humid gases over honeycomb-type catalysts were performed, and the influence of water vapor on the rate of catalytic oxidation was investigated. The result of the experiments suggests that the rate of catalytic oxidation decreases with increasing water vapor content and its influence varies depends on the temperature. It is also indicated the rate of oxidation substantially decreases at the lower temperatures even in the case where water vapor contents is considerably lower. Therefore, it is necessary to consider the decrease in the catalytic activity by coexistent water vapor.

Analysis of ultraviolet radiation in clear skies in Beijing and its affecting factors

Abstract Analyzing observational data for solar radiation, meteorological parameters and total ozone concentration during the period of January 1990 to December 1991 in Beijing enabled the development of an empirical method for estimation of UV irradiance (UVI) in clear skies. Predicted values from the model agreed well with observations. The mean relative bias for 24 months was 1.9%. UVI (290–400 nm) in clear sky conditions from 1979 to 1998 was calculated, and its long-term variation showed a declining trend of −3.89%, which was accompanied by a decrease in total O3 of −5.75%, a decrease in scattering factor (S/D, the ratio of solar scattered to direct radiation) of −20.79%, and an increase in water vapor content of +4.76%. It is hypothesized that many substances in the atmosphere, including volatile organic compounds (VOCs) and their oxidation products, very fine particles and others absorb and/or utilize UV energy. The long-term UVI trends and its main controlling factors in four seasons during the previous 2 decades are discussed, UV energy consumption by atmospheric chemical and photochemical processes, is especially important during summer.

Boron removal from metallurgical silicon using CaO-SiO 2-CaF 2 slags

The removal of boron from metallurgical silicon in slag system of CaO-SiO 2–10%CaF 2 was investigated. The partition coefficient of boron ( L B) between slag and silicon phase was studied under different conditions of slag basicity (CaO/SiO 2 ratio), temperature, mass ratio of slag to silicon and gas blowing. The results show that L B has a maximum value of 4.61 when the CaO/SiO 2 mass ratio is around 2 at 1 873 K. The logarithm of L B is linear to the reciprocal of temperatures in the range of 1 773-1 973 K. L B increases with the increase of mass ratio of slag to silicon, but it does not increase markedly when the ratio excesses 3. Gas blowing can significantly increase the removal of boron, and L B increases with the increase of water vapor content.

Hydrogen-induced self-assembly of helical carbon nanostructures from ethanol over SiO2 catalysts

Helical carbon nanostructures from ethanol over silica are successfully prepared through the addition of hydrogen during chemical vapor deposition. The helical structure formation appears to occur through hydrogen etching reactions enabling graphitic caps between neighboring tubes to merge, triggering the self-assembly of a helical structure. The experimental data is supported by thermodynamic calculations which correlate the hydrogen radical concentration with the observed efficiency of helical structure formation. Moreover, the calculations show an increase in water vapor content as one increases hydrogen addition. This can account for the improved crystallinity of the samples with higher hydrogen doses.

Effects of H2O and Particles on the Simultaneous Removal of SO2 and Fly Ash Using a Fluidized-Bed Sorbent/Catalyst Reactor

This study investigated the potential of a fluidized-bed sorbent/catalyst reactor for the simultaneous removals of SO2 and fly ash from a simulated flue gas containing different H2O and particles. Experimental results showed that the removal efficiency of particles and SO2 was 85%−96% and 5.75−2.97 mg SO2/g, respectively, as the H2O content was 1.5−5.3%. The activities of sorbent/catalysts for simultaneous removals of SO2 and particles were inhibited by H2O and particles, and the inhibition effects increased with the content of H2O. As the H2O content increased, the particle size distribution (PSD) of fine particles shifted to the coarse particles. The results of BET analysis show that the obstruction phenomenon of the sorbent/catalyst caused by the particles was diminished with the increased content of H2O. The results showed this aggregation phenomenon of fine particles shifted to the coarse particles may cause increased water vapor content in fluidized-bed sorbent/catalyst reactor.

Verification of moisture budgets during drifting snow conditions in a cold wind tunnel

Experiments in a cold wind tunnel were used to verify drifting snow sublimation models. A layer of drifting snow particles was formed over a sintered snow surface. Sublimation and drifting snow flux were estimated from two vertically resolved profile measurements separated along the flow path and were compared to a simple, one‐dimensional diffusion model of drift and drifting snow sublimation. The experiments show an increase in water vapor content of the air from drifting snow sublimation. The measured drifting snow sublimation appeared to be consistent with albeit somewhat larger than theoretical values found in the model study. Under wind tunnel conditions, particle number density appears to be the most important controlling factor on the sublimation rate. For experiments with external solar radiative forcing, the increase of the sublimation rate was also larger than theoretical predictions. The experiments suggest that irregular snow crystals and solar radiation might increase sublimation rates more than described by many drifting snow models.

Dilute Methane Treatment by Atmospheric Pressure Dielectric Barrier Discharge: Effects of Water Vapor

Oxidation of dilute methane in oxygen containing mixtures by atmospheric pressure dielectric barrier discharge at moderate temperature (below 150°C) has been studied with regard to the effect of water vapor. First, the impact of water vapor on methane conversion was studied in nitrogen. In dry nitrogen, methane was converted into hydrogen cyanide and hydrogen in the absence of oxidant. When water was added, it both acted as a scavenger in competition with methane for reactive nitrogen species and changed the reaction product speciation from HCN to carbon monoxide and carbon dioxide. The addition of water also led to the formation of hydrogen and nitrogen oxides. In the presence of oxygen, the addition of 1% water vapor enhanced methane conversion. Increasing water vapor content above 1% had a slight positive effect on methane conversion, and was found to enhance selectivity of the reaction products toward carbon dioxide over carbon monoxide.

Effect of Postoxidation Annealing on Reliability of Thermal Oxides Grown on n-Type 4H–SiC(0001) Wafer

The effects of two types of postoxidation annealing (POA) techniques on the reliability of thermal oxides grown on a 4H–SiC(0001) wafer have been investigated. Hydrogen POA at a high temperature of 800 °C is carried out for 30 min after dry oxidation at 1200 °C and it results in an improvement of the insulating properties of thermal oxides. The mode values of the field-to-breakdown (EBD) and charge-to-breakdown (QBD) of thermal oxides prepared by high-temperature hydrogen POA are 10.6 MV/cm and 0.39 C/cm2, respectively. On the other hand, pyrogenic reoxidation annealing (ROA) with a water vapor content above 25% at 950 °C for 180 min adversely affects the reliability of thermal oxides. Also, it is found that the reliability of thermal oxides on a 4H–SiC wafer prepared by pyrogenic ROA degrades with an increase in water vapor content in wet ambient.

Subcritical crack growth in silica aerogel

The sub-critical crack growth domain in hydrophilic silica aerogel was studied using the Double-Cleavage-Drilled-Compression test (DCDC). The effect of temperature and water vapor content on the crack growth rate is measured. The experiments are carried out between 295 and 383 K with relative air moisture ranging from 5% to 80% Rh. Like dense silica, crack growth velocities were found to decrease when increasing the temperature at a constant water vapor concentration. Surprisingly, the crack velocity also decreases when increasing water vapor content at constant temperature. Such a behavior is contrary to expected results usually encountered in glasses. An analogy with nitrogen adsorption experiments on the same aerogels is used to explain this behavior. We assume that a capillary condensation phenomenon of water vapor inside the aerogel porosity takes place, inducing internal compressive stresses.

Oxidative Hydrolysis in Water Vapor-Air Phase of CsI Radioaerosols Produced by CsI Sublimation from Metallic Surface

Behavior of CsI radioaerosols produced by CsI sublimation from a platinum support in argon, air, and water vapor-air mixture was studied. During 10-12 min of the vaporization at 900-1570 K, CsI radioaerosols undergo oxidative hydrolysis with atmospheric oxygen and water vapor to form CsOH aerosols and I2. The cesium-to-iodine ratio determined in various fractions shows that oxidation of CsI in argon is minimal and is caused by the presence of oxygen and water traces. Oxidative hydrolysis of CsI strongly increases with increasing water vapor content in the vapor-gas flow. The degree of oxidative hydrolysis of CsI in the gas flow depends not only on the content of water vapor and oxygen but also on the initial CsI/O2 molar ratio.

GPS observations in Thailand for hydrological applications

We report the delineation of the onset of the Asian Monsoon based on GPS sensing of water vapor in Thailand. We conducted GPS observations at five sites in Thailand since March 1998 under the hydrological project called GAME-T. The objective of the project is to clarify the water and energy cycle system in the Asian Monsoon area. As a preliminary analysis, we used data from March to June 1998 and estimated the water vapor content in the zenith direction (PWV) every 30 minutes using GIPSY software (GPS-PWV). A comparison of the resultant PWV with those estimated from rawinsonde data (Sonde-PWV) suggested that, generally, the long term trends of both GPS-PWV and Sonde-PWV are consistent and a rapid increase of water vapor content is visible in May, which corresponds to the onset of the Monsoon. However, systematic differences between GPS-PWV and Sonde-PWV are eminent. The RMS of the difference (RMSD) between Sonde-PWV and GPS-PWV reaches about 8.7 mm. This large RMSD can be reduced to about 5 mm by removing some unreliable sonde data and making a linear correction to Sonde-PWV. In addition, a comparison of GPS-PWV with other meteorological data (temperature, humidity, and rainfall) showed that there is a strong correlation between a rapid increase of GPS-PWV and heavy rainfall in Bangkok and in Chiang Mai, which may be used to judge the onset of the Monsoon in the area accurately.

Observational evidence of a wind direction signal in SSM/I passive microwave data

Recent experiments have demonstrated that a wind direction signal is apparent in passive microwave brightness temperature measurements of the sea surface. Extensive matches of Special Sensor Microwave Imager (SSM/I) brightness temperatures from several Defense Meteorological Satellite Program (DMSP) satellites, with wind direction measurements from both moored buoys and spaceborne scatterometers clearly show directional signals at 19, 37, and 85 GHz for both horizontal and vertical polarization. The wind direction signal obtained from the mooring matches is noisy due to the limited number of matches but varies little from satellite to satellite. The greater number of matches with the scatterometers results in a clearer directional signal and enables detailed studies of the dependence of the directional signal on environmental conditions. The amplitude of the mean directional signal increases with wind speed. The up/downwind asymmetry most prominent at vertical polarization varies mainly with wind speed, while the crosswind differences also vary with sea state and sea surface temperature. The variability about the mean directional signal is equal to or greater than the amplitude of the mean signal and increases with increasing water vapor content. Because of the large variability, large numbers of SSM/I observations under similar environmental conditions must be averaged before the directional signal is apparent. Comparisons between the observed directional signals and existing model predictions will lend insight into the physical mechanisms responsible for the signal.

Studying the extinction coefficient due to aerosol particles at different spectral bands in some regions at great Cairo

Extinction coefficient due to aerosol has been estimated by Pyrheliometric and Gorgie type Actinometric measurements in the industrial, urban areas and compared with agricultural areas. The measurements distributed over one year from June 1992 to May 1993 were made under clear sky for five spectral bands. The results show two maxima in hot wet and spring months and minimum in winter months, but there is a fluctuation in urban area. Diurnal variations show maximum at noon especially in the industrial area. Level of extinction coefficient in the industrial and urban area is greater than that of the agricultural area, except for hot wet months is due to the increase of water vapor content in agricultural area. Spectral distribution of the extinction coefficient decreases monotonically with wavelength. Size of particles in industrial area is greater than in urban and agricultural areas. The temperature and water vapor content have important rules in increasing the extinction coefficient of aerosols.

Influence of water vapor on the susceptibility to electric-field damage of KTiOPO4

We demonstrate that the susceptibilities of hydrothermal and flux grown KTiOPO4 (KTP) crystals to electric-field induced darkening increase with increasing water vapor content of the atmosphere surrounding the crystals. Infrared spectroscopy shows that hydrogen ions from the atmosphere migrate into the crystals in the presence of the applied electric field and charge compensate the formation of Ti3+ defects which are responsible for damage. These observations suggest that KTP-based electro-optic devices should be operated in a dry environment to reduce their susceptibility to damage.

The kinetics of the reduction of chromium oxide by hydrogen

The reduction kinetics has been studied as function of hydrogen partial pressures,pH2O/pH2 ratio, gas flow rate, and temperature. The reduction follows a linear time law and is dependent on the gas flow rate below a value of approximately 10 cm · s-1, since the rate is determined by the removal of the water vapor being formed. In this range the reduction rate may be calculated from gas dynamical data. At sufficiently high flow rates the phase boundary reaction is rate determining. The activation energy is 123 kJ · mol-1. The reduction rate is proportional to the square root of hydrogen pressure and decreases with increasing water vapor content.