Vapor Outflow Research Articles

Contribution of Recycled and External Advected Moisture to Precipitation and Its Inter‐Annual Variation Over the Tibetan Plateau

AbstractIn this study, we performed a high‐resolution simulation using the Weather Research and Forecasting model, integrated with water vapor tracers, covering the years 2005–2019. Our objective was to obtain deeper insights into the spatiotemporal dynamics of external advected and local evaporative water vapor, and to elucidate their impact on precipitation patterns across the Tibetan Plateau (TP). Our findings underscore that a significant proportion of TP's precipitation originates from external advected water vapor, primarily entering through the western and southern boundaries. During summer, stronger zonal and meridional water vapor transport, driven by prevailing westerly winds and the Asian monsoon, significantly influences seasonal and spatial precipitation variations. Additionally, we observed that the inter‐annual variation of precipitation is intricately linked to changes in the net water vapor influx, modulated by alterations in atmospheric circulation. We also analyze the Precipitation Recycling Ratio (PRR) which refers to the proportion of precipitation originated from local evaporative water vapor to the total precipitation, revealing distinctive elevation‐dependent variations aligned with grassland distribution. Notably, PRR exhibits asynchronous shifts with precipitation at different timescales, potentially linked to soil moisture‐precipitation feedback at intra‐annual scales. Moreover, the investigation highlights that inter‐annual variations in PRR are primarily linked to the inflow and outflow of water vapor as well as wind strength at 500 hPa, particularly prominent during colder seasons, while thermal factors carry comparable weight to dynamical factors in warmer seasons.

Anomalous Characteristics of Water Vapor Budget on the Tibetan Plateau under the Influence of Tropical Cyclones over the Bay of Bengal during Early Summer

Abstract Early summer is a peak time for tropical cyclone (TC) activities over the Bay of Bengal (BoB) and a period of South Asian monsoon onset, and the TCs during this time have a significant impact on the water vapor transport associated with monsoons. This study investigates the anomalous characteristics of the dynamic–thermal atmospheric circulation structure and water vapor budget over the Tibetan Plateau (TP) under the influence of BoB TCs generated in May from 1979 to 2020 with JTWC best track data and ERA5 data. Results reveal that a significant southerly water vapor channel forms from the BoB to the southeastern TP with a water vapor convergence near the Yarlung Zangbo Grand Canyon. A part of the water vapor is transported directly to the TP by deep southerly jet, while the other part is lifted by TCs and then climbs upward to the TP by two uplift processes occurring on the southern slope of the TP and over the TP respectively, which makes the whole troposphere over the southeastern TP warmer and wetter. It is found that anomalous southeasterly airflow in the northeast of TC circulation turns to anomalous southwesterly airflow forming an abnormal anticyclonic circulation over the southern TP in the middle and upper troposphere due to the diabatic heating effect. In this process, the TP acts as an anomalous water vapor sink with remarkable water vapor inflow through its southern boundary, with the main water vapor outflow through the eastern boundary, but a weak easterly water vapor backflow to the eastern TP in the lower troposphere. Significance Statement This study attempts to investigate the anomalous features of the water vapor budget over the Tibetan Plateau (TP) under the influence of the Bay of Bengal (BoB) tropical cyclones (TCs) during early summer. Results show that a significant southerly water vapor channel forms from the BoB to the southeastern TP with a water vapor convergence near the Yarlung Zangbo Grand Canyon. The TP acts as an anomalous water vapor sink with more and higher water vapor inflows through the southern boundary of the TP. A positive temperature and humidity anomaly can be found over the southeastern TP extending upward into the middle and upper troposphere. The results are helpful to understand how the BoB TCs affect the weather process over the TP.

Variation Characteristics of Summer Water Vapor Budget and Its Relationship with the Precipitation over the Sichuan Basin

Based on the daily precipitation data from the meteorological stations in Sichuan and the monthly average ERA-Interim reanalysis data from 1979 to 2016, the variation characteristics of summer water vapor budget in the Sichuan Basin and its relationship with precipitation are discussed in this study. The results show that, in summer, the water vapor in the Sichuan Basin and its four sub-basins flows in from the southern and western boundaries and flows out through the eastern and northern boundaries, and the basin is obviously a water vapor sink. From 1979 to 2016, the water vapor inflow from the southern and western boundaries significantly decreased, as well as the water vapor outflow through the eastern boundary. The summer precipitation in the Sichuan Basin is significantly positively correlated with the water vapor inflow at the southern boundary and net water vapor budget of the basin in the same period, and it is negatively correlated with the water vapor outflow at the northern boundary. The southern and northern boundaries are the two most important boundaries for the summer precipitation in the Sichuan Basin. Additionally, this study reveals that, under the multi-scale topography on the east side of the Tibet Plateau, the spatio-temporal distribution of precipitation in the Sichuan Basin results from the interactions between the unique topography of the Sichuan Basin and the different modes of water-vapor transport from low latitudes. The atmospheric circulation over the key area of air–sea interaction in the tropical region and its accompanying systems, as well as the anomalies of regional circulations and water vapor transport over the eastern China and Sichuan Basin, are the main reasons for the variation in summer precipitation in the Sichuan Basin.

Convection velocities in gas and liquid phases during fragmentation of droplets

The paper presents experimental research findings for the convection velocities in the gas and liquid phases during micro-explosive fragmentation of droplets heated on a solid surface. The experiments were conducted with two types of bi-component droplets: emulsified and unmixed ones. A scheme with an induction heater in the temperature range of 75–550 °C was used. The convection velocities were recorded in droplets during heating, rapid evaporation, partial fragmentation in the puffing regime and full fragmentation in the micro-explosion regime. Typical shapes and dimensions of the origins of vortex formation were distinguished. The velocities of vapor outflow from the surface of the droplet and secondary fragments as a result of droplet breakup were established. Their variation ranges were determined. The effect of the surface temperature, droplet dimensions, component composition of liquid and type of droplets on these velocities was identified. The research findings were compared with the previous data obtained in experiments with a droplet fixed on a holder in a hot air flow. We showed threshold convection velocities in droplets sufficient for their breakup during puffing and micro-explosion regimes. General approximations were derived for the convection velocities in the droplets under study versus the substrate temperature.

Role of the Tibetan Plateau in Northern Drought Induced by Changes in the Subtropical Westerly Jet

AbstractThe Tibetan Plateau (TP), the so-called water tower of Asia, plays an important role in the water cycle. However, few studies have linked the TP’s water vapor supply with the climate over North China. In this study, we found that changes in the subtropical westerly jet (SWJ) dynamically induce drought in North China, and the TP plays an important role in this relationship. During July–August for the period of 1981–2019, the SWJ center between 75° and 105°E obviously shifted northward at a rate of 0.04° per year. Correspondingly, the zonal winds in the southern subtropics were incredibly weakened, causing the outflow of water vapor from the TP to decrease dramatically. Combined with numerical simulations, we discovered that a reduction in water vapor transport from the TP can obviously decrease the precipitation over North China. Sensitivity experiments demonstrated that if the water vapor outflow from the eastern border of the TP decreases by 52.74%, the precipitation in North China will decrease by 12.69% due to a decrease in the local cloud fraction caused by a diminished water vapor content in the atmosphere. Therefore, although less water vapor transport occurs in the upper troposphere than in the lower troposphere, the impact of transport from the TP in the former on the downstream precipitation cannot be ignored.

Spatial-Temporal Distribution of Summer Extreme Precipitation in South China and Response of Tropical Ocean

In the study, the summer extreme precipitation in South China is divided into early rainy season (MJ) and late rainy season (JA). The percentile method (95%) is used to define the extreme precipitation threshold. Based on the international general definition method of extreme precipitation threshold: percentile method (95%), the extreme precipitation thresholds in flood season before and after South China are defined respectively. The total amount and frequency of extreme precipitation in flood season before and after 1979-2014 are calculated in this paper. The change trend of the two indicators is basically the same, and the two indicators have obvious interannual variation and an upward trend. According to the results of wavelet analysis of extreme precipitation frequency, the frequency of extreme precipitation in the first flood season mainly has a period of 3 - 5 years, while the frequency of extreme precipitation in the later flood season has a significant period of 6 - 8 years. The spatial distribution of extreme precipitation before and after the flood season shows that the extreme precipitation in the former flood season is mainly distributed in the central part of Guangdong, the northeast of Guangxi and the western part of Fujian, and the extreme precipitation in the latter flood season mainly occurs in the southern coastal area. The results show that there are different tropical SST regions affecting the extreme precipitation in South China. The former flood season is mainly the tropical Indian Ocean warm SST, and the latter flood season is mainly the tropical Pacific warm SST. The tropical Indian Ocean SST stimulates the anticyclonic anomaly over the South China Sea, which brings the southwest warm and humid air flow into South China, resulting in the increase of extreme precipitation in the first flood season of South China; the tropical Pacific SST stimulates the cyclonic anomaly over the South China Sea, which reduces the water vapor outflow caused by the seasonal northward jump of the subtropical high in South China, resulting in the increase of extreme precipitation in the later flood season of South China.

Nucleate boiling heat transfer and critical heat flux (CHF) from micro-pit surfaces

This paper studies pool boiling enhancement on the micro-pit surfaces. Microscale pits fabricated on plain surface are able to reduce boiling incipience superheat, and improve both nucleate boiling heat transfer coefficient and critical heat flux (CHF). Boiling enhancement magnitudes have a weak dependence on the micro-pit diameter, but increase monotonously with decreasing the pit depth. There exists an optimum pit-to-pit spacing for the maximum boiling enhancements, which is virtually identical to bubble departure diameter, and estimated using the capillary length. The major mechanism behind is that this spacing is favorable for alleviating hydrodynamic instabilities induced by the counterflow between liquid inflow and vapor outflow. The highest heat transfer coefficient and CHF using water as fluid under the present conditions are 70.0 kW/m2K and 165.7 W/cm2, improved by 58.8% and 33.7% compared to the plain surface, respectively, at micro-pit diameter of 100 μm, depth of 100 μm and spacing of 2.5 mm. Finally, a correlation devised for predicting the nucleate boiling heat transfer coefficient on the micro-pit surfaces by incorporating dimensionless pit depth is proposed, with MAE of 8.3%.

Reconsidered Method for Validation of Experimental Data for Direct Contact Condensers With Zero Vapor Outflow

Abstract Method presented in the paper is a reconsideration of the already published equations for a quick and reliable verification of experimental results related to direct contact condensers with zero vapor outflow. Both original and reconsidered methods presented by the author are confirmed by a large number of experimental data (more than 1250 total data points) which took over one decade of experiments on four different column types. Both methods draw the background in sound and simple theory and should be considered as very reliable while easy to use in practice.

Study the dynamics of hollow jet formation under vapor outflow from the supercritical state

The features of the unsteady process of a cavity formation inside the jet at a sudden outflow of water vapor through a thin nozzle from a pressure vessel, initially in a supercritical state, are studied. A numerical study was carried out by using the sonicFoam solver of the OpenFOAM library with the Peng-Robinson equation of state in a two-dimensional axisymmetric approximation. Visualization of the obtained solutions is presented in the form of pictures dynamics for fields of velocities and temperatures. It is shown that the mode of formation and maintenance of the cavity inside the jet is supported more than 100 μs from the beginning of the expiration process.

Formation of Small Clusters in the Free Expanding Water Vapor Plume

The results of calculations of water vapor outflow from a source, in which the pressure and temperature are maintained constant, into a vacuum through an orifice in the infinitely thin wall are presented. The calculations are carried out using the direct simulation Monte Carlo method when the processes of water cluster formation/decay in the flow field are taken into account. The vapor flow regimes transient with respect to the Knudsen number are considered. The effect of the cluster formation processes on the parameters of flow which becomes significant for the mole cluster fraction above 4%is analyzed. The effect of “freezing” the mole cluster concentrations with increase in the distance from the source is demonstrated. The influence of the probabilities of monomer and dimer association during pair collisions, used in the model, on themole dimer fraction is investigated. The results obtained are compared with the available experimental data.

Features of shock-wave and vortex processes simulation at depressurization of circuits with superheated water coolant

Formation and evolution of pressure waves on the barrier were numerically simulated at non-staionary outflow of the superheated vapor from the vessel. The simulation conditions were fully consistent with the experimental conditions (1982) [1]. The calculated pressure fields were calculated both at the initial stage of non-stationary vapor outflow and at the quasistationary flow of superheated vapor on the barrier. The dynamics of interaction between shock waves and vortex structures on the barrier was studied at quasi-stationary outflow of the superheated vapor, and the experimental pressure profile on the target was compared with the calculated pressure profile. Comparison of the experimental data and the calculation results has showed acceptable agreement between the pressure profiles on the target up to a distance from the target to the nozzle approximately X/D = 6.

Novel method for validation of experimental data for direct contact condensers with zero vapor outflow

Although contact condensers are extensively used for various industrial applications, procedures for calculation and sizing these vessels are scarce in the open literature. However, before new and reliable calculation procedures can be derived, it is important to obtain properly verified experimental results. In this paper, a novel validation procedure is introduced for the case of condensation of the complete amount of vapor that enters the device. The proposed procedure is based entirely on the theoretical model that must always be fulfilled in the aforementioned case. This fact makes it very useful in verification of experimental results for contact condensers with no vapor outflow.

Numerical simulation of precipitate formation during the boiling of salt solution in a geothermal reservoir

The process of precipitate formation during vapor outflow from a high-temperature geothermal reservoir saturated with a salt solution is investigated numerically. The evaporation regimes characterized by the formation of a phase transition front are considered. Comparison with the asymptotic solution obtained previously is performed. In the region of parameters where the self-similar solution exists the numerical solution approaches the asymptotic one in a short time. In the region where the asymptotic solution does not exist the numerical solution shows that the solid salt saturation monotonically increases with catastrophic growth in the last stage, which leads to the filling of the pores with solid salt and the total blocking of the flow.

Effect of particle size on the composition of lignin derived oligomers obtained by fast pyrolysis of beech wood

The effect of particle size on the yield and composition of lignin derived oligomers (also known as pyrolytic lignin (PL)) was studied in a fluidized bed reactor. Milled beech wood particles of sizes between 0.3 and 0.55 and cylinders of 3–14mm were pyrolyzed at 500°C. The lignin oligomers were isolated from bio-oil and analyzed using several analytical techniques (TG, Py-GC/MS, and 1H NMR). The yield of PL fraction decreased half when particle size raised from 0.3 to 3mm. DTG analysis of the PL showed higher loss rates between 200 and 600°C as particle size increased from 0.55 to 3–4mm. Py-GC/MS results suggested a dramatic decrease of methoxylated phenols (in line with the 1H NMR studies) and the loss of ether bonds when the particle size was increased from milled small particles of 0.3mm to cylinders with a diameter between 3 and 5mm. In general, most chemical changes and changes in PL yield occur between the milled particles (composed mainly of the cell wall) and cylinders with original wood structure. Comparing the milled particles to the cylinders with equal length (equal vapor outflow distance) but varied diameter, the effect on the yield of PL seems to be mainly due to the impact of thermally ejected oligomers on internal cell walls of biomass particles (mass transfer limitations).

Surface geomorphology of Jupiter Family Comets: A geologic process perspective

Recent spacecraft encounters with Jupiter Family Comets have revealed markedly diverse surface morphologies: Wild 2 is dominated by steep-walled and flat-floored depressions, Tempel 1 is relatively smooth and exhibits evidence for flows and layering, while Hartley 2 is bi-lobed with knobby terrain at its ends and a much smoother terrain in its middle. This diversity of surface morphologies has been interpreted as an evolutionary sequence (Belton, M.J.S. [2010]. Icarus 210, 881–897) where Jupiter Family Comets evolve from Wild 2 morphology, then to Tempel 1 morphology, and finally to Hartley 2 morphology. We propose instead that the diversity of surface morphology reflects geologic processing with diverse outcomes. In addition to impact cratering, we consider surface modification driven by the cometary activity which is responsible for gas and dust production. We consider eolian erosion that may be driven by the outflow of cometary vapor, making use of information from wind tunnel experiments and in situ studies of eolian erosion on Mars. We adopt the model of van der Waals cohesion recently proposed by Scheeres et al. (Scheeres, D., Hartzell, C., Sanchez, P., Swift, M. [2010]. Icarus 210, 968–984) and find that the average CO2 vapor outflow flux at Hartley 2 of 0.95×1017cm−2s−1 implies wind speeds sufficient to mobilize particles of 10cm size even close to the icy reservoirs where the vapor is evolved, below the surface. We suggest that particles are mobilized and entrained in flows within sub-surface outflow channels, emerging to be readily lifted into the coma, and fragmenting in the process. Although water production from Hartley 2 is greater, most of it is evolved in the coma from icy particles and does not contribute to eolian erosion of the nucleus. On the other hand, the much lower vapor outflow flux at Tempel 1 of 4×1014cm−2s−1 is insufficient, in the present model, to mobilize particles but is consistent with generating repeated fluidization episodes. The Wild 2 case is intermediate, with average outflow flux 7×1016cm−2s−1 which would be, in our model, sufficient to support eolian erosion. The steep-walled, flat-floor depressions on Wild 2 may have originated as impact features but have been subsequently modified by eolian erosion causing slope recession. We do not have definitive evidence to discriminate between an evolutionary sequence and diverse geologic outcomes, but we suggest future in situ observations at comets that may do so.

Modeling underwater penetration of LNG carrier

AbstractAn underwater breach of a tank in a double‐hulled LNG carrier poses several challenging questions to be addressed by an adequate model. This article describes a model that accounts for the following phenomena: (1) LNG tank vapor space pressure decreasing by the piston effect of outflow (the effect a decreasing water level pulling down the pressure); (2) LNG evaporation in the hull space and vapor outflow through the outer breach; (3) LNG outflow and gas inflow to the LNG tank at the inner breach; (4) Ice formation by LNG evaporative cooling. The model does not allow for localized ice build up at the inner breach constricting flow. Predictions show tank pressure, LNG outflow rates, water inflow rates over time, the duration of the event, and total LNG losses. Losses are shown to be considerably less with double‐hull than with single hull construction. © 2008 American Institute of Chemical Engineers Process Saf Prog, 2008

Internal mechanism of metastable liquid water crystallization and its effects on intracloud processes

Specific features of an internal freezing (crystallization) mechanism for both ordinary supercooled water and amorphous water (A-water) are considered. Amorphous water plays the role of an intermediate phase in condensation ice formation and is capable of metastable existence in the form of cloud drops. It is demonstrated that, after passing the crystallization front, the ice phase takes the liquid-phase volume and the excessive water mass is detached from the front in the form of free molecules, which escape through the liquid into the gaseous medium. The released energy of the phase transition is removed with these molecules, so that the formed ice retains the initial temperature of the liquid. A high-rate vapor outflow from the freezing drop generates (around the drop) a zone of microscale turbulence, which accelerates the mass exchange between cloud particle and vapor. Since the freezing frequency of drops in a cloud increases with their size, the effects of their freezing develop initially in time. At the same time, these effects initiate such processes that end in a complete evaporation of supercooled water drops and in a sharp enlargement of A-water and ice particles, i.e., in cloud transition to such a phase-mixed state where the liquid disperse phase consists of A-water drops. A reduction in the duration of the initial (fine-dispersed) stage of the evolution of clouds with their temperature lowering can be explained only by the development of microscale disturbances as a result of the freezing of drops.

Observations of Water Vapor Outflow from NML Cygnus

We report new observations of the far-infrared and submillimeter water vapor emission of NML Cygnus based on data gathered with the Infrared Space Observatory and the Submillimeter Wave Astronomy Satellite. We compare the emission from NML Cyg to that previously published for VY CMa and W Hya in an attempt to establish the validity of recently proposed models for the outflow from evolved stars. The data obtained support the contention by Ivezic & Elitzur that the atmospheres of evolved stars obey a set of scaling laws in which the optical depth of the outflow is the single most significant scaling parameter, affecting both the radiative transfer and the dynamics of the outflow. Specifically, we provide observations comparing the water vapor emission from NML Cyg, VY CMa, and W Hya and find, to the extent permitted by the quality of our data, that the results are in reasonable agreement with a model developed by Zubko & Elitzur. Using this model we derive a mass loss based on the dust opacities, spectral line fluxes, and outflow velocities of water vapor observed in the atmospheres of these oxygen-rich giants. For VY CMa and NML Cyg, we also obtain an estimate of the stellar mass.

Estimation of water requirement per unit carbon fixed byEucalyptus camaldulensis in semi-arid land of Western Australia

Afforestation in arid land is a promising method for carbon fixation, but the effective utilization of water is highly important and required. Thus, the evaluation of the amount of water per unit carbon fixed with the tree growth is required to minimize the amount of water supplied to the plants. In this research, a tree is regarded as a carbon fixation reactor with inflows of water and nutrients from roots, and CO2 as the carbon source from leaves with outflow of water vapor from leaves and accumulation in the tree itself. In the process of photosynthesis and respiration nutritional elements are dissolved in water flow in trees. They do not flow out by these reactions, but are accumulated in trees. Thus, we have treated the behaviour of nutrients as a marker to evaluate the water/carbon ratio.

557 GH[CLC]z[/CLC] Observations of Water Vapor Outflow from VY Canis Majoris and W Hydrae

We report the first detection of thermal water vapor emission in the 557 GHz, 110-101 ground-state transition of ortho-H2O toward VY Canis Majoris. In observations obtained with the Submillimeter Wave Astronomy Satellite, we measured a flux of ~450 Jy, in a spectrally resolved line centered on a velocity vLSR = 25 km s-1 with an FWHM of ~35 km s-1, somewhat dependent on the assumed line shape. We analyze the line shape in the context of three different radial outflow models for which we provide analytical expressions. We also detected a weaker 557 GHz emission line from W Hydrae. We find that these and other H2O emission-line strengths scale as suggested by Zubko and Elitzur.