scholarly journals The lightness of water vapor helps to stabilize tropical climate

2020 ◽  
Vol 6 (19) ◽  
pp. eaba1951 ◽  
Author(s):  
Seth D. Seidel ◽  
Da Yang
Keyword(s):  
Water Vapor ◽  
Longwave Radiation ◽  
Tropical Climate ◽  
Climate Feedback ◽  
Tropical Atmosphere ◽  
Radiative Effect ◽  
Buoyancy Effect ◽  
Moist Air ◽  
Dry Air ◽  
Earth’S Climate

Moist air is lighter than dry air at the same temperature, pressure, and volume because the molecular weight of water is less than that of dry air. We call this the vapor buoyancy effect. Although this effect is well documented, its impact on Earth’s climate has been overlooked. Here, we show that the lightness of water vapor helps to stabilize tropical climate by increasing the outgoing longwave radiation (OLR). In the tropical atmosphere, buoyancy is horizontally uniform. Then, the vapor buoyancy in the moist regions must be balanced by warmer temperatures in the dry regions of the tropical atmosphere. These higher temperatures increase tropical OLR. This radiative effect increases with warming, leading to a negative climate feedback. At a near present-day surface temperature, vapor buoyancy is responsible for a radiative effect of 1 W/m2 and a negative climate feedback of about 0.15 W/m2 per kelvin.

scholarly journals The Incredible Lightness of Water Vapor

2020 ◽  
Vol 33 (7) ◽  
pp. 2841-2851 ◽  
Author(s):  
Da Yang ◽  
Seth D. Seidel
Keyword(s):  
Water Vapor ◽  
Longwave Radiation ◽  
Tropical Atmosphere ◽  
Radiative Effect ◽  
Buoyancy Effect ◽  
Feedback Strength ◽  
Show Evidence ◽  
Temperature And Pressure ◽  
Earth’S Climate ◽  
Climate Studies

AbstractThe molar mass of water vapor is much less than that of dry air. This makes a moist parcel lighter than a dry parcel of the same temperature and pressure. This effect is referred to as the vapor buoyancy effect and has often been overlooked in climate studies. We propose that the vapor buoyancy effect increases Earth’s outgoing longwave radiation (OLR) and that this negative radiative effect increases with warming, stabilizing Earth’s climate. We illustrate this mechanism in an idealized tropical atmosphere, where there is no horizontal buoyancy gradient in the free troposphere. Temperature increases toward dry atmosphere columns to compensate the reduced vapor buoyancy, increasing OLR by O(1 W m−2) at the reference climate. In warmer climates, the temperature difference between moist and dry columns would increase as a result of increasing atmospheric water vapor, leading to enhanced radiative effect and thereby stabilizing Earth’s climate. We estimate that this feedback strength is about O(0.2 W m−2 K−1) in the idealized atmosphere, which compares to cloud feedback and surface albedo feedback in the current climate. We further show evidence from observations and real-gas radiative transfer calculations for a significant radiative effect of vapor buoyancy in the tropical atmosphere.

scholarly journals <i>A Tale of Two Dust Storms</i>: analysis of a complex dust event in the Middle East

2019 ◽  
Vol 12 (9) ◽  
pp. 5101-5118 ◽  
Author(s):  
Steven D. Miller ◽  
Louie D. Grasso ◽  
Qijing Bian ◽  
Sonia M. Kreidenweis ◽  
Jack F. Dostalek ◽  
...  
Keyword(s):  
Water Vapor ◽  
Mineral Dust ◽  
Weather Prediction ◽  
Detection Threshold ◽  
Dust Storms ◽  
Moist Air ◽  
Air Mass ◽  
Dry Air ◽  
Environmental Controls ◽  
Dust Detection

Abstract. Lofted mineral dust over data-sparse regions presents considerable challenges to satellite-based remote sensing methods and numerical weather prediction alike. The southwest Asia domain is replete with such examples, with its diverse array of dust sources, dust mineralogy, and meteorologically driven lofting mechanisms on multiple spatial and temporal scales. A microcosm of these challenges occurred over 3–4 August 2016 when two dust plumes, one lofted within an inland dry air mass and another embedded within a moist air mass, met over the southern Arabian Peninsula. Whereas conventional infrared-based techniques readily detected the dry air mass dust plume, they experienced marked difficulties in detecting the moist air mass dust plume, becoming apparent when visible reflectance revealed the plume crossing over an adjacent dark water background. In combining information from numerical modeling, multi-satellite and multi-sensor observations of lofted dust and moisture profiles, and idealized radiative transfer simulations, we develop a better understanding of the environmental controls of this event, characterizing the sensitivity of infrared-based dust detection to column water vapor, dust vertical extent, and dust optical properties. Differences in assumptions of dust complex refractive index translate to variations in the sign and magnitude of the split-window brightness temperature difference commonly used for detecting mineral dust. A multi-sensor technique for mitigating the radiative masking effects of water vapor via modulation of the split-window dust-detection threshold, predicated on idealized simulations tied to these driving factors, is proposed and demonstrated. The new technique, indexed to an independent description of the surface-to-500 hPa atmospheric column moisture, reveals parts of the missing dust plume embedded in the moist air mass, with the best performance realized over land surfaces.

scholarly journals Virtualization

2007 ◽  
Vol 64 (4) ◽  
pp. 1405-1409 ◽  
Author(s):  
Peter R. Bannon
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Relative Density ◽  
Moist Air ◽  
Dry Air ◽  
Equivalent Mass ◽  
Solid Water ◽  
Virtual Temperature ◽  
Mass Volume

Abstract The virtual temperature of a moist air parcel is defined as the temperature of a dry air parcel having the same mass, volume, and pressure. It is shown here that a virtual air parcel can be formed diabatically by warming the parcel to its virtual temperature while replacing its water vapor with the equivalent mass of dry air under isobaric, isochoric conditions. Conversely a saturated virtual air parcel can be formed diabatically by cooling the parcel to its saturated virtual temperature while replacing some of its dry air with the equivalent mass of water vapor under isobaric, isochoric conditions. These processes of virtualization can be represented on a vapor pressure–temperature diagram. This diagram facilitates the comparison of the relative density of two moist air parcels at the same pressure. The effects of liquid and/or solid water can also be included.

scholarly journals Effect of Ionizing Radiation on Moist Air Systems

1987 ◽  
Vol 112 ◽  
Author(s):  
Donald T. Reed ◽  
Richard A. Van Konynenburg
Keyword(s):  
Nitrous Oxide ◽  
Steady State ◽  
Water Vapor ◽  
Gas Phase ◽  
Radiation Chemistry ◽  
Water Systems ◽  
Gas Composition ◽  
Moist Air ◽  
Dry Air ◽  
Closed Systems

AbstractThe radiation chemistry of nitrogen/oxygen/water systems is reviewed. General radiolytic effects in dry nitrogen/oxygen systems are relatively well characterized. Irradiation results in the formation of steady state concentrations of ozone, nitrous oxide and nitrogen dioxide. In closed systems, the concentration observed depends on the total dose, temperature and initial gas composition. Only three studies have been published that focus on the radiation chemistry of nitrogen/oxygen/water homogeneous gas systems. Mixed phase work that is relevant to the gaseous system is also summarized. The presence of water vapor results in the formation of nitric acid and significantly changes the chemistry observed in dry air systems. Mechanistic evidence from the studies reviewed are summarized and discussed in relation to characterizing the gas phase during the containment period of a repository in tuff.

Converting Moist Air Into Water and Power

2008 ◽  
Author(s):  
Robert J. Vidmar
Keyword(s):  
Water Vapor ◽  
Heat Exchange ◽  
Latent Heat ◽  
Heat Exchangers ◽  
State Of The Art ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Ambient Water ◽  
Moist Air ◽  
Dry Air

A method to process moist air into dry air and water results in a surplus of energy for the process. The sun evaporates water everywhere on earth and expends 2.26 MJ/kg (429.9 Btu/lbm) for each kg (2.204 lbm) of water evaporated. A mass of 1 kg (2.204 lbm) of water with a mixing ratio of 0.3% in dry air represents 2.26 MJ (199 Btu) of latent heat energy distributed in a volume of approximately 333 cubic meters (11,759 cubic feet). A system is described by which ambient water vapor is enriched, condensed with the release of latent heat in a heat-exchange boiler, which vaporizes a working fluid used in a Rankine-cycle turbine generator system. Water vapor enrichment is achieved with a vapor-separation barrier. Fans draw moist air through an air-intake system which brings the air into contact with a large surface-area vapor-separation barrier. The intake of a compressor imposes a vacuum on the extraction side of the barrier at a pressure that is lower than the ambient water-vapor pressure. This pressure difference drives water vapor across the barrier into the compressor. A two-stage compressor is used to maintain the low pressure and convey water vapor at high temperature and near atmospheric pressure to a heat-exchange boiler. Two processes occur in the heat-exchange boiler: 1) water vapor condenses and is pumped out of the boiler, and 2) heat is transferred to a working fluid that vaporizes. The vaporized working fluid drives a turbine in a Rankine cycle with condenser. Exhaust heat from the turbine is dissipated with a water-cooled condenser. An air-cooled rock-bed system is suggested as an alternative, when water cooling is not possible. Current advances in materials, the efficiency of turbomachinery, and the effectiveness of heat exchangers suggest that a system can be conceived that is completely fueled by moist air and produces water and excess shaft horsepower that can be converted into electricity. The analysis treats turbomachinery and heat exchangers as ideal components constrained by the Carnot and isentropic efficiencies. Pumps and fans are treated as components with state-of-the-art efficiency. System computations for an ideal 100% efficient system indicate that approximately 25% of the latent heat can be converted to electricity. For a system made with contemporary state-of-the art components a yield of a few percent is predicted. Principles of operation and engineering details are quantified.

scholarly journals <i>A Tale of Two Dust Storms</i>: Analysis of a Complex Dust Event in the Middle East

2019 ◽  
Author(s):  
Steven D. Miller ◽  
Louie Grasso ◽  
Quijing Bian ◽  
Sonia Kreidenweis ◽  
Jack Dostalek ◽  
...  
Keyword(s):  
Water Vapor ◽  
Mineral Dust ◽  
Weather Prediction ◽  
Detection Threshold ◽  
Dust Storms ◽  
Moist Air ◽  
Air Mass ◽  
Dry Air ◽  
Environmental Controls ◽  
Dust Detection

Abstract. Lofted mineral dust over data-sparse regions presents considerable challenges to satellite-based remote sensing methods and numerical weather prediction alike. The Southwest Asia domain is replete with such examples, with its diverse array of dust sources, dust mineralogy, and meteorologically-driven lofting mechanisms on multiple spatial and temporal scales. A microcosm of these challenges occurred over 3–4 August 2016 when two dust plumes, one lofted within an inland dry air mass and another embedded within a moist air mass, met over the Southern Arabian Peninsula. Whereas conventional infrared-based techniques readily detected the dry air mass dust plume, they experienced marked difficulties in detecting the moist air mass dust plume, which only became apparent when visible reflectance revealed it crossing over an adjacent dark water background. In combining information from numerical modelling, multi-satellite/multi-sensor observations of lofted dust and moisture profiles, and idealized radiative transfer simulations, we develop a better understanding of the environmental controls of this event, characterizing the sensitivity of infrared-based dust detection to column water vapor, dust vertical extent, and dust optical properties. Differences in assumptions of dust complex refractive index translate to variations in the sign and magnitude of the split-window brightness temperature difference commonly used for detecting mineral dust. A multi-sensor technique for mitigating the radiative masking effects of water vapor via modulation of the split-window dust-detection threshold, predicated on idealized simulations tied to these driving factors, is proposed and demonstrated. The new technique, indexed to independent-sensor description of the surface-to-500 mb atmospheric column moisture, reveals parts of the missing dust plume embedded in the moist air mass, with best performance over land surfaces.

scholarly journals Physical Mechanisms of Tropical Climate Feedbacks Investigated Using Temperature and Moisture Trends*

2015 ◽  
Vol 28 (22) ◽  
pp. 8968-8987 ◽  
Author(s):  
A. J. Ferraro ◽  
F. H. Lambert ◽  
M. Collins ◽  
G. M. Miles
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Tropical Climate ◽  
Lapse Rate ◽  
Climate Feedback ◽  
Climate Projections ◽  
Tropospheric Temperature ◽  
Regional Pattern ◽  
Rate Feedback ◽  
Water Vapor Feedback

Abstract Tropical climate feedback mechanisms are assessed using satellite-observed and model-simulated trends in tropical tropospheric temperature from the MSU/AMSU instruments and upper-tropospheric humidity from the HIRS instruments. Despite discrepancies in the rates of tropospheric warming between observations and models, both are consistent with constant relative humidity over the period 1979–2008. Because uncertainties in satellite-observed tropical-mean trends preclude a constraint on tropical-mean trends in models regional features of the feedbacks are also explored. The regional pattern of the lapse rate feedback is primarily determined by the regional pattern of surface temperature changes, as tropical atmospheric warming is relatively horizontally uniform. The regional pattern of the water vapor feedback is influenced by the regional pattern of precipitation changes, with variations of 1–2 W m−2 K−1 across the tropics (compared to a tropical-mean feedback magnitude of 3.3–4 W m−2 K−1). Thus the geographical patterns of water vapor and lapse rate feedbacks are not correlated, but when the feedbacks are calculated in precipitation percentiles rather than in geographical space they are anticorrelated, with strong positive water vapor feedback associated with strong negative lapse rate feedback. The regional structure of the feedbacks is not related to the strength of the tropical-mean feedback in a subset of the climate models from the CMIP5 archive. Nevertheless the approach constitutes a useful process-based test of climate models and has the potential to be extended to constrain regional climate projections.

scholarly journals Post-Plasma Catalysis for Trichloroethylene Abatement with Ce-Doped Birnessite Downstream DC Corona Discharge Reactor

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 946
Author(s):  
Grêce Abdallah ◽  
Jean-Marc Giraudon ◽  
Rim Bitar ◽  
Nathalie De Geyter ◽  
Rino Morent ◽  
...  
Keyword(s):  
Corona Discharge ◽  
Active Oxygen Species ◽  
Surface Acidity ◽  
Good Stability ◽  
Ozone Decomposition ◽  
Moist Air ◽  
Plasma Catalysis ◽  
Dry Air ◽  
Water Tolerance ◽  
By Products

Trichloroethylene (TCE) removal was investigated in a post-plasma catalysis (PPC) configuration in nearly dry air (RH = 0.7%) and moist air (RH = 15%), using, for non-thermal plasma (NTP), a 10-pin-to-plate negative DC corona discharge and, for PPC, Ce0.01Mn as a catalyst, calcined at 400 °C (Ce0.01Mn-400) or treated with nitric acid (Ce0.01Mn-AT). One of the key points was to take advantage of the ozone emitted from NTP as a potential source of active oxygen species for further oxidation, at a very low temperature (100 °C), of untreated TCE and of potential gaseous hazardous by-products from the NTP. The plasma-assisted Ce0.01Mn-AT catalyst presented the best CO2 yield in dry air, with minimization of the formation of gaseous chlorinated by-products. This result was attributed to the high level of oxygen vacancies with a higher amount of Mn3+, improved specific surface area and strong surface acidity. These features also allow the promotion of ozone decomposition efficiency. Both catalysts exhibited good stability towards chlorine. Ce0.01Mn-AT tested in moist air (RH = 15%) showed good stability as a function of time, indicating good water tolerance also.

Transport properties of real moist air, dry air, steam, and water

2021 ◽  
pp. 1-9
Author(s):  
Sebastian Herrmann ◽  
Hans-Joachim Kretzschmar ◽  
Vikrant C. Aute ◽  
Donald P. Gatley ◽  
Eckhard Vogel
Keyword(s):  
Transport Properties ◽  
Moist Air ◽  
Dry Air

scholarly journals A Study of Moist Air Condensation Characteristics in a Transonic Flow System

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4052
Author(s):  
Jie Wang ◽  
Hongfang Gu
Keyword(s):  
Mach Number ◽  
Relative Humidity ◽  
Transonic Flow ◽  
Flow System ◽  
Plane Surface ◽  
Droplet Growth ◽  
Moist Air ◽  
Dry Air ◽  
Hydraulic Equipment ◽  
Non Equilibrium

When water vapor in moist air reaches supersaturation in a transonic flow system, non-equilibrium condensation forms a large number of droplets which may adversely affect the operation of some thermal-hydraulic equipment. For a better understanding of this non-equilibrium condensing phenomenon, a numerical model is applied to analyze moist air condensation in a transonic flow system by using the theory of nucleation and droplet growth. The Benson model is adopted to correct the liquid-plane surface tension equation for realistic results. The results show that the distributions of pressure, temperature and Mach number in moist air are significantly different from those in dry air. The dry air model exaggerates the Mach number by 19% and reduces both the pressure and the temperature by 34% at the nozzle exit as compared with the moist air model. At a Laval nozzle, for example, the nucleation rate, droplet number and condensation rate increase significantly with increasing relative humidity. The results also reveal the fact that the number of condensate droplets increases rapidly when moist air reaches 60% relative humidity. These findings provide a fundamental approach to account for the effect of condensate droplet formation on moist gas in a transonic flow system.

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