Surface Vapor Pressure Research Articles

Recent and near‐term future changes in impacts‐relevant seasonal hydroclimate in the world's Mediterranean climate regions

AbstractChange over recent decades in the world's five Mediterranean Climate Regions (MCRs) of quantities of relevance to water resources, ecosystems and fire are examined for all seasons and placed in the context of changes in large‐scale circulation. Near‐term future projections are also presented. It is concluded that, based upon agreement between observational data sets and modelling frameworks, there is strong evidence of radiatively‐driven drying of the Chilean MCR in all seasons and southwest Australia in winter. Observed drying trends in California in fall, southwest southern Africa in fall, the Pacific Northwest in summer and the Mediterranean in summer agree with radiatively‐forced models but are not reproduced in a model that also includes historical sea surface temperature (SST) forcing, raising doubt about the human‐origin of these trends. Observed drying in the Mediterranean in winter is stronger than can be accounted for by radiative forcing alone and is also outside the range of the SST‐forced ensemble. It is shown that near surface vapour pressure deficit (VPD) is increasing almost everywhere but that, surprisingly, this is contributed to in the Southern Hemisphere subtropics to mid‐latitudes by a decline in low‐level specific humidity. The Southern Hemisphere drying, in terms of precipitation and specific humidity, is related to a poleward shift and strengthening of the westerlies with eddy‐driven subsidence on the equatorward side. Model projections indicate continued drying of Southern Hemisphere MCRs in winter and spring, despite ozone recovery and year‐round drying in the Mediterranean. Projections for the North American MCR are uncertain, with a large contribution from internal variability, with the exception of drying in the Pacific Northwest in summer. Overall the results indicate continued aridification of MCRs other than in North America with important implications for water resources, agriculture and ecosystems.

A study of evaporation duct characteristics in the South China Sea during the Winter of 2017

The evaporation duct (ED) near the sea surface is the most frequent type of duct that traps and redirects electromagnetic waves over longer or shorter distances. This study uses radiosonde data from the South China Sea Two-Island Monsoon Experiment (SCSTIMX) in 2017 and the Weather Research and Forecasting (WRF) model to study the ED and ED height (EDH). We enhanced the vertical resolution to 26 layers in the lowest 134 m. The simulations indicate that EDs were prevalent throughout the South China Sea (SCS) area in winter 2017, where the prevailing surface winds are strong northeasterly. The EDH exhibits diurnal variations and significant variability across the SCS. The WRF simulations of ED and EDH generally agree with observations of the trajectory of Taiwan-O.R.1. Our results indicate that the WRF model can simulate the pattern of ED and EDH over SCS. Results reveal that Yonsei University (YSU) boundary layer (BL) parameterization more accurately simulates the vertical temperature and humidity variations in the lower atmosphere, with stronger winds and higher EDH in most areas. The YSU and the Medium Range Forecast Model (MRF) BL schemes show similar ED patterns to the Taiwan-O.R.1 SCS radiosonde observations but consistently underestimate the EDH. While strong surface winds in the winter SCS may contribute to a higher EDH, the strong surface wind-induced vertical mixing also modifies sea surface air temperature, relative humidity, and vapor pressure, affecting the vertical refractivity. Our results indicate that sea surface air temperature is a more reliable factor affecting EDH in the simulations.

Molecular dynamics simulation of vapor-liquid equilibrium in 1-alkanol unary systems: a study of surface tension, density, and vapor pressure of TraPPE-UA force field

Molecular dynamics simulation of vapor-liquid equilibrium in 1-alkanol unary systems: a study of surface tension, density, and vapor pressure of TraPPE-UA force field

Improving the Forecasts of Surface Latent Heat Fluxes and Surface Air Temperature in the GRAPES Global Forecast System

The GRAPES (Global/Regional Assimilation and Prediction System) global medium-range forecast system (GRAPES_GFS) is a new generation numerical weather forecast model developed by the China Meteorological Administration (CMA). However, the forecasts of surface latent heat fluxes and surface air temperature have systematic biases, which affect the forecasts of atmospheric dynamics by modifying the lower boundary conditions and degrading the application of GRAPES_GFS since the 2 m air temperature is one of the key components of weather forecast products. Here, we add a soil resistance term to reduce soil evaporation, which ultimately reduces the positive forecast bias of the land surface latent heat flux. We also reduce the positive forecast bias of the ocean surface latent heat flux by considering the effect of salinity in the calculation of the ocean surface vapor pressure and by adjusting the parameterizations of roughness length for the exchanges in momentum, heat, and moisture between the ocean surface and atmosphere. Moreover, we modify the parameterization of the roughness length for the exchanges in heat and moisture between the land surface and atmosphere to reduce the cold bias of the nighttime 2 m air temperature forecast over areas with lower vegetation height. We also consider the supercooled soil water to reduce the warm forecast bias of the 2 m air temperature over northern China during winter. These modified parameterizations are incorporated into the GRAPES_GFS and show good performance based on a set of evaluation experiments. This paper highlights the importance of the representations of the land/ocean surface and boundary layer processes in the forecasting of surface heat fluxes and 2 m air temperature.

Deep and Comprehensive Study on the Impact of Different Phosphazene‐Based Flame‐Retardant Additives on Electrolyte Properties, Performance, and Durability of High‐Voltage LMNO‐Based Lithium‐Ion Batteries

Herein, the formulation of safe electrolytes for Li‐ion batteries based on phosphazene as a flame‐retardant (FR) is achieved. Three molecules are studied: hexafluorocyclotriphosphazene (FR1), (ethoxy)pentafluorocyclotriphosphazene (FR2), and pentafluoro(phenoxy)cyclotriphosphazene (FR3). By using a conventional electrolyte (LiPF6 salt in an ethylene carbonate/diethyl carbonate solvents mixture), FR's minimum percentages are defined to quantify their efficiency as FRs. Fluoroethylene carbonate is also added to the electrolyte (2 wt%). The surface tensions, vapor pressures, and transport properties of formulated electrolytes are measured to highlight the impact of the FR additives. Then, these electrolytes are tested in half and full electrochemical devices: Li|LiMn1.5Ni0.5O4 (LMNO) and graphite|LMNO between C/10 and C/2 at 20 °C. Flammability tests show that 3% of FR1, 5% of FR2, or 15% of FR3 are needed to make the electrolytes nonflammable. The transport properties of electrolytes based on FR1 and FR2 remain unchanged compared to the conventional electrolyte. Finally, the graphite|LMNO devices lose only 5% of the initial capacity after 100 cycles with the electrolytes based on FR1 and FR2, hence, confirming the latter's potential as an efficient FR for high‐voltage Li‐ion batteries.

Accumulated soil moisture deficit better indicates the effect of soil water stress on light use efficiency of grasslands during drought years

Light use efficiency (LUE) models have been widely used in the estimation of gross primary productivity (GPP). However, many studies indicated that current LUE models generally overestimate GPP during drought years. Recent studies also showed that soil moisture (SM) regulated LUE during drought years, indicating the necessity of adding SM-related stress scalars in LUE models. Meanwhile, considering the persistence characteristic of drought, the effect of SM stress on LUE is expected to be not only instantaneous but also accumulated. However, it is unclear whether the accumulated SM stress can better capture LUE. Thus, based on observations from grassland flux sites in the United States and Australia, we compared the effectiveness of concurrent soil moisture deficit (SMD), lagged soil moisture deficit (LSMD), and accumulated soil moisture deficit (ASMD) in capturing actual LUE during drought years. ASMD had more stable and stronger linear correlations with LUE than SMD and LSMD at almost all the sites. Furthermore, ASMD outperformed water stress scalars commonly used in LUE models such as the Land Surface Water Index (LSWI) and vapor pressure deficit (VPD) for tracking actual LUE during drought years. The introduction of ASMD improved the accuracy of the LUE model for simulating grassland GPP during drought years (with a R2 and RMSE of 0.88 and 1.06 g C m−2 d−1). Our study highlights the accumulated effect of SM in regulating LUE, and proves that ASMD has the potential in improving the performance of the existing LUE models during drought years.

Experimental study of the surface vapor pressure of a microencapsulated phase change material slurry liquid desiccant within the entire temperature range of a dehumidification system

The surface vapor pressure is a critical physical property of a liquid desiccant, which has a direct influence on the mass transfer driving force in the dehumidification and regeneration process. In this study, a measurement system for the surface vapor pressure of the microencapsulated phase change materials slurry (MPCMS) was built using a static method. The surface vapor pressure of the MPCMS at 293.2 K–353.2 K was measured, which covered the entire range of dehumidification and regeneration. Experimental results showed that the surface vapor pressure of the MPCMS decreased compared with that of the pure LiCl solution. The surface vapor pressure drop ratio of the MPCMS increased with increasing MicroPCM and LiCl mass concentrations. The phase transition of the MicroPCMs intensified the drop in the MPCMS surface vapor pressure. When the MicroPCM and LiCl mass concentrations were 2 % and 40 %, respectively, and at the phase transition temperature of 303.2 K, the vapor pressure drop ratio reached a maximum of 17 %. A correlation for the MPCMS surface vapor pressure calculation was proposed, and the deviation between the calculated and measured values was less than 10 %. The results of this study provide basic data for the future development of the MPCMS liquid desiccant system.

Mapping Climate Parameters over the Territory of Botswana Using GMT and Gridded Surface Data from TerraClimate

This articles presents a new series of maps showing the climate and environmental variability of Botswana. Situated in southern Africa, Botswana has an arid to semi-arid climate, which significantly varies in its different regions: Kalahari Desert, Makgadikgadi Pan and Okavango Delta. While desert regions are prone to droughts and periods of extreme heat during the summer months, other regions experience heavy downpours, as well as episodic and unpredictable rains that affect agricultural activities. Such climatic variations affect social and economic aspects of life in Botswana. This study aimed to visualise the non-linear correlations between the topography and climate setting at the country’s scale. Variables included T °C min, T °C max, precipitation, soil moisture, evapotranspiration (PET and AET), downward surface shortwave radiation, vapour pressure and vapour pressure deficit (VPD), wind speed and Palmer Drought Severity Index (PDSI). The dataset was taken from the TerraClimate source and GEBCO for topographic mapping. The mapping approach included the use of Generic Mapping Tools (GMT), a console-based scripting toolset, which enables the use of a scripting method of automated mapping. Several GMT modules were used to derive a set of climate parameters for Botswana. The data were supplemented with the adjusted cartographic elements and inspected by the Geospatial Data Abstraction Library (GDAL). The PDSI in Botswana in 2018 shows stepwise variation with seven areas of drought: (1) −3.7 to −2.2. (extreme); (2) −2.2 to −0.8 (strong, southern Kalahari); (3) −0.8 to 0.7 (significant, central Kalahari; (4) 0.7 to 2.1 (moderate); (5) 2.1 to 3.5 (lesser); (6) 3.5 to 4.9 (low); (7) 4.9 to 6.4 (least). The VPD has a general trend towards the south-western region (Kalahari Desert, up to 3.3), while it is lower in the north-eastern region of Botswana (up to 1.4). Other values vary respectively, as demonstrated in the presented 12 maps of climate and environmental inventory in Botswana.

Variation of Relative Humidity as Seen through Linking Water Vapor to Air Temperature: An Assessment of Interannual Variations in the Near-Surface Atmosphere

It has generally been regarded that, in the warming climate, atmospheric water vapor may increase due to the enhancement in surface evaporation, which is expected from the Clausius–Clapeyron (C–C) equation, along with the assumption that relative humidity experiences small changes. If the variation in relative humidity is small, the response of water vapor to temperature will be closely in line with the C–C equation. However, whether relative humidity experiences large or small changes needs be assessed, and the change of relative humidity should be compared with the change in surface–air temperature. In this study, we link surface vapor pressure, which characterizes atmospheric water vapor, to surface-air temperature, and treat both the temperature and relative humidity as influencing factors. A method based on linear regression is applied to compare the interannual variabilities of relative humidity and temperature in the interannual variation in surface vapor pressure. Whether the year-to-year perturbation of relative humidity is important, compared with the perturbation in surface-air temperature, is explored Results show that, at high latitudes of both hemispheres, the variation in vapor pressure is dominated by air temperature, and relative humidity has small positive contributions. Thus, the variation in relative humidity over these regions is comparably small, and the response of water vapor to temperature can well follow the C–C equation. Differently, at mid-low latitudes, especially on land, air temperature plays a negative role in the variation in vapor pressure. Relative humidity offsets the negative contribution and dominates the variation in vapor pressure, suggesting that the variation in the relative humidity over these regions is comparably large. Hence, the response of water vapor to temperature deviate from the C–C equation. Analysis indicates that the different results of the dominance from the two influencing factors are affected by the dual effects of precipitation or wet-air transport over land. Both precipitation and the transport of cold wet air could break the C–C relation between water vapor pressure and temperature.

西北干旱区泡泡刺灌丛的降雨再分配特征及影响因素分析

定量分析植被冠层对降雨再分配过程的影响, 是认识陆地生态系统水文循环的重要环节。然而, 由于干旱区天然植被分布稀疏、形态结构特殊, 其降雨再分配过程的测算较为困难, 相关研究较少, 特别是关于荒漠低矮灌丛的降雨再分配研究鲜有报道。本文以河西走廊中段临泽绿洲—荒漠过渡带的天然建群种泡泡刺灌丛(Nitraria sphaerocarpa)为研究对象, 基于3年逐个单次降雨事件的观测数据分析了生长季泡泡刺灌丛的降雨再分配特征及主要影响因素, 量化了泡泡刺灌丛覆盖下实际进入土壤的有效降雨量及其空间分布特征。结果表明：(1)生长季泡泡刺灌丛的平均穿透率、树干茎流率和冠层截留损失率分别为87.89%、1.61%和10.50%；(2)降雨量是影响泡泡刺灌丛降雨再分配特征的关键气象因素, 其与穿透雨量、树干茎流量、冠层截留损失量之间具有显著的统计关系(P < 0.001)；(3)与干旱区其他稀疏植被相比, 泡泡刺灌丛的穿透率和集流率较高, 冠层截留损失率较低, 与其特殊的植被形态特征有关, 相关分析的结果表明, 泡泡刺灌丛的穿透雨量与植被面积指数和株高呈显著的负相关关系(P < 0.001), 树干茎流量与树干倾角呈显著的正相关关系(P < 0.01)。这些研究结果增进了我们对于绿洲—荒漠过渡带植被对局地水文过程影响的认识, 为合理估算干旱区稀疏植被覆盖下的冠层截留损失提供了方法参考。;Analyzing quantitatively the effect of vegetation canopy on rainfall partitioning is an important part for better understanding the hydrological cycle in terrestrial ecosystems, which is particularly useful for hydrologic budget estimation, hydrological models' establishment and afforestation projects' implement in drylands. However, it is difficult to measure and calculate its rainfall partitioning process of the natural vegetation in the drylands due to its sparse distribution and special morphological structure, and very few field measurements have conducted specially for the natural desert dwarf shrub species, which distributed widely in the oasis-desert ectone of northwestern China. Here we present results of the partitioning of rainfall into throughfall (TF), stemflow (SF) and interception loss (IL) by a shrub species Nitraria sphaerocarpa, a naturally dominant species of Linze oasis-desert ecotone in the middle part of the Hexi Corridor, based on the observation data during the growing season for 3 years. Consequently, the effective rainfall that actually enters the soil and its spatial distribution characteristics beneath the N. sphaerocarpa canopy are quantified. We also analyze the influencing factors for rainfall partitioning by N. sphaerocarpa canopy. The results show that: (1) on average, the measured throughfall, stemflow and derived interception loss by N. sphaerocarpa during growing season account for 87.89%, 1.61% and 10.50% of gross rainfall amount, respectively. The average funneling ratio for N. sphaerocarpa is (129.66 ±93.01) and its canopy storage capacity is 0.42 mm. N. sphaerocarpa's throughfall is produced from rainfall events with total amount more than 0.2 mm, while its stemflow does not occur following rainfall events less than 1.5 mm. (2) Rainfall amount is the key meteorological factor affecting the rainfall partitioning characteristics. There are significant correlations between rainfall amount and throughfall, stemflow and interception loss (P < 0.001). Other meteorological variables like canopy surface temperature, atmospheric temperature, atmospheric humidity and vapor pressure can also affect rainfall redistribution process. (3) Compared with other sparse vegetation in drylands, the N. sphaerocarpa has higher throughfall percentage and funneling ratio, but lower interception loss percentage. Special canopy morphology of N. sphaerocarpa may play an important role in its pattern of rainfall partitioning. Pearson correlation analysis shows that throughfall has significantly negative correlation with plant area index (PAI) and shrub height (P < 0.001), and stemflow has positive correlation with stem orientation (P < 0.01). Other canopy morphology like bark roughness, leaf shape and canopy form, which lack of quantitative description, are also vital for rainfall partitioning patterns. The results might improve better understanding of shrubs' role on the local hydrological processes in oasis-desert ecotone, and provide a reasonable method for estimating interception loss by sparse vegetation in drylands.

Al coverage of AlN(0001) surface and Al vapor pressure – Thermodynamic assessment based on ab initio calculations

Ab initio calculations were used to determine physical properties of AlN(0001) surface under Al coverage. It was shown that Al atoms are adsorbed in T4 sites for very low Al coverage, up to θAl=1/4 monolayers (ML). For higher Al coverage, θAl=1/4ML up to θAl=1ML the adlayer becomes disordered and corrugated vertically. In this coverage range (0<θAl≤1ML) the Al bonding energy is independent on the coverage and equal to EadsDFT≅5.0eV. For higher coverage, 1ML≤θAl≤7/6ML, the Al adlayer becomes ordered and atomically flat. The Al adsorption energy in this range is EadsDFT≈6.0eV, i.e. much higher. For higher coverage, θAl>1.25ML, the Al adatoms are located in the second layer. The adsorption energy is reduced to EadsDFT=3.97eV at θAl=1.25ML and linearly increasing to EadsDFT=4.88eV for the coverage increase up to θAl=2ML. Full thermodynamic analysis identified two regions in equilibrium with Al vapor: first at very low pressures where θAl≤10-3ML and the second for higher pressures which is 1ML≤θAl≤7/6ML. The second region is relevant for physical vapor transport (PVT) AlN growth. The nitrogen adsorption process, important for PVT AlN growth, takes place at single or double Al layer covered AlN(0001) surface.

Spatial pattern of lake evaporation increases under global warming linked to regional hydroclimate change

Lakes are critical natural resources that are vulnerable to climate change. In a warmer climate, lake evaporation is projected to increase globally, but with substantial variation between regions. Here, based on ensemble projections of climate and lake models and an attribution method, we show that future lake evaporation increase is strongly modulated by regional hydroclimate change. Specifically, a drying hydroclimate will amplify evaporation increase by enlarging surface vapor pressure deficit and reducing cloud shortwave reflection. Future lake evaporation increase is amplified in tropical America, the Mediterranean and Southeast China with drier future hydroclimates, and dampened in high latitudes and the Tibetan Plateau with wetter future hydroclimates. Such spatially coupled changes in lake evaporation and hydroclimate have important implications on regional lake water balance and volume change, which can aggravate water scarcity and flood risks.

Impact of geophysical and anthropogenic factors on wildfire size: a spatiotemporal data-driven risk assessment approach using statistical learning

Wildfire spread is a stochastic phenomenon driven by a multitude of geophysical and anthropogenic factors. In this study, we propose a spatiotemporal data-driven risk assessment framework to understand the effect of various geophysical/anthropogenic factors on wildfire size, leveraging a systematic machine learning approach. We apply this framework in the state of California–the most vulnerable US state to wildfires. Using county-level annual wildfire data from 2001–2015, and various geophysical (e.g., land cover, wind, surface temperature) and anthropogenic features (e.g., population density, housing type), we trained, tested, and validated a suite of ensemble tree-based learning algorithms to identify and evaluate the key factors associated with wildfire size. The Extreme Gradient Boosting (XGBoost) algorithm outperformed all the other models in terms of generalization performance, categorization of important features, and risk performance. We found that standard deviations of meteorological variables with long-tailed distributions play a key role in predicting wildfire size. Specifically, the top ten factors associated with high risk of larger wildfires include larger standard deviations of surface temperature and vapor pressure deficit, higher wind gust, more grassy and barren land covers, lower night-time boundary layer height and higher population density. Our proposed risk assessment framework will help federal/state decision-makers to adequately plan for wildfire risk mitigation and resource allocation strategies.

Experimental study on the liquid desiccant dehumidification performance of microencapsulated phase change materials slurry

In this study, the idea of using microencapsulated phase change materials slurry (MPCMS) as a liquid desiccant to achieve “auto internally cooled” dehumidification was verified and investigated experimentally. The results indicated that, the addition of MicroPCMs to LiCl solution significantly improved the dehumidification performance, the temperature-rise of the liquid desiccant could be effectively restrained, and the dehumidification performance of the MPCMS improved with the increase in the amount of MicroPCMs. When the mass concentration of the MicroPCMs reached 2.0%, the moisture removal rate and dehumidification effectiveness increased by 24.0% and 23.1%, respectively. The contribution ratio of the phase change endothermic effect of MicroPCMs to the dehumidification enhancement was 50–60%, the reduction of the MPCMS surface vapor pressure also played an important role. The impact of several factors on the dehumidification performance, including the mass concentration of the MicroPCMs, temperature and flow rate of the MPCMS, process air inlet state, and flow rate were analyzed. The dehumidification performance was improved most significantly when the MPCMS inlet temperature was close to the onset phase transformation temperature of the MicroPCMs. In addition, empirical correlations with mean relative deviations of 5.1% and 12.74% were proposed to predict the dehumidification effectiveness and the Sherwood number. • The effect of MicroPCMs on dehumidification performance is verified experimentally. • Moisture removal rate/dehumidification efficiency of MPCMS are enhanced greatly. • The temperature-rise of liquid desiccant can be restrained by the MicroPCMs. • The slurry inlet temperature and the concentration of MicroPCMs are critical. • Empirical correlations are proposed to predict dehumidification efficiency and Sh.

Polymer-Water Interaction Enabled Intelligent Moisture Regulation in Hydrogels.

The water-vapor transition is critical for hydrogels in a collection of applications. However, how the polymer-water interaction along with the nature of the structure affect the macroscopic water-vapor transition remains a challenging question to answer. In this work, we tested the moisture transfer behaviors of a series of hydrogels at different humidities and found some hydrogels capable of lowering their surface vapor pressure to stop dehydration at low humidity and absorbing water from ambient air to recover toward initial states at high humidity. Through molecular dynamic simulations, we demonstrate that water inside these hydrogels undergoes increasing intensive intermolecular bonding during evaporation. The increased intermolecular bonding reduces the vapor pressure of the hydrogels and leads to the self-regulation. More interestingly, we demonstrate the self-regulation is closely related to the Young's modulus of hydrogels. These results provide further insight into the mechanism of the water-vapor transition in hydrogels and show potential in a broad range of future applications.

Interfacial properties of binary mixtures of Lennard-Jones chains in planar interfaces by molecular dynamics simulation.

Binary mixtures of fully flexible linear tangent chains composed of bonded Lennard-Jones interaction sites (monomers) were studied using the molecular dynamics simulation in the NVT ensemble. Their interfacial properties were investigated in planar interfaces by direct simulation of an explicit liquid film in equilibrium with its vapor. A method for the calculation of long-range interactions in inhomogeneous fluids was implemented to take into account the potential truncation effects. Surface tension and the pressure tensor were calculated via the classical Irving-Kirkwood method; vapor pressure, orthobaric densities, density profiles, and Gibbs relative adsorption of the volatile component with respect to the heavy component were also obtained. The properties were studied as a function of the temperature, molar concentration of the heavy component, and the asymmetry of the mixture. According to the results of this work, the temperature loses influence on the surface tension, vapor pressure, and Gibbs relative adsorption curves as the molecular length of the heavy component increases. This suggests that the universal behavior observed in pure fluids of Lennard-Jones chains also holds for binary mixtures. The contribution of the long-range interactions turned out to account for about 60%, 20%, and 10% of the surface tension, vapor pressure, and orthobaric density final values, respectively. This contribution was even larger at high temperatures and for large molecules. Strong enrichment of the volatile component at the interface was observed in the asymmetric mixtures. One of these mixtures even showed a barotropic effect at elevated pressures and a class III phase behavior.

Will land use land cover change drive atmospheric conditions to become more conducive to wildfires in the United States?

AbstractThe increase in wildfire risk in the United States in recent decades has been linked to rapid growth of the wildland‐urban interface and to changing climate. While there have been numerous studies on wildfires and climate change, few have separately assessed the impact of climate response to land‐use‐land‐cover change (LULCC) on wildfires. In this study, we analyse two 10‐year regional climate simulations driven by the current (2011) and future (2100) land‐use‐land‐cover patterns to assess modifications by the projected LULCC to the frequency and severity of fire‐prone atmospheric conditions described by two fire weather indices, the Canadian Forest Fire Weather Index and the Hot‐Dry‐Windy Index. The simulation corresponding to future land‐use‐land‐cover pattern yields higher surface temperature and vapour pressure deficit and lower precipitation compared to the simulation with the current pattern in areas where urbanized landscapes replace forests and grasslands, such as along the Piedmont and outside the Chicagoland region, while in areas where croplands replace forests, such as the southeast Coastal Plains, the results are reversed. These changes to local and regional atmospheric conditions lead to longer fire seasons and more extreme fire‐weather conditions in much of the eastern United States, specifically in the Southeast and Ohio River Valley where significant urban expansion is projected by the end of the century. Whereas in Southern California where some highly flammable shrublands will be replaced by urban or crop lands, fire‐prone atmospheric conditions are likely to be less frequent and less extreme in the future. However, much of California moves towards a year‐round fire season under the projected LULCC. The results suggest that by altering atmospheric conditions, LULCC may play an important role in determining fire regime, but the effects are highly heterogeneous and regionalized.

Experimental Study on the Regeneration Process of the Dehumidification System of Lithium Bromide Solution Based on Computer

Dehumidification is a common problem in production and life. solution dehumidification method is to use salt solution with strong hygroscopicity as dehumidifier, the salt solution is in direct communicate with the treated air because of the pressure variance between the water vapor force on the side of the salt solution and the water vapor force of the treated air, the moisture is driven to transfer between the air and the hygroscopic solution, thus the change of air humidity is realized. In short, the high concentration of lithium bromide and other aqueous solutions absorb the water vapor in the atmosphere by the force difference between the water vapor and the treated air, thus completing the dehumidification process of the air. After the solution absorbs water in the air, it needs to be concentrated and regenerated to restore moisture absorption capacity. Many scholars at home and abroad have studied the solution dehumidification system. Florida Solar Energy Center Swami proposed a system for regeneration of solutions using roofs as solar absorbing surfaces in 1998. Nelson dehumidification performance of Li Cl solution as dehumidifier was studied. Due to the fact that the surface vapor pressure, specific heat capacity, corrosion and other physical and chemical properties of lithium bromide are better than those of lithium chloride and calcium chloride under the same PH and equal concentration, I have studied the regeneration process of dehumidification system of lithium bromide solution based on computer.

Insights into evaporation from the surface of capillary porous media gained by discrete pore network simulations

Reliable prediction of the drying rate from the surface of a porous medium remains a scientific challenge due to complex interactions between the gas-side boundary layer and porous medium structure. One way to tackle this issue is to opt for a mesoscale pore network model. Two parameter functions (i.e. surface vapor pressure–surface saturation, and the surface vapor transport coefficient–surface vapor concentration relationship) are assessed from the pore network modeling, which can be used in the frame of a continuum model to couple the porous medium with the boundary layer. Moreover, emendation factors are introduced to link the normalized evaporation rate from the wet part of the porous medium surface with the surface wetness or surface saturation. Their evaluation shows that the normalized evaporation rate contributed from wet patches tends to surface saturation with increasing intensity of drying, whereas a similar but weaker trend can be observed with surface wetness. This correlation provides, especially in case of enhanced and non-isothermal drying processes, a simple method for coupling the wet surface region with the gas-side boundary layer in a two-equation continuum model. We have also evaluated the evaporation rate from the wet surface region by inserting pore network modeling data into a modified version of Schlünder's model. The results are not encouraging the derivation of continuum model boundary conditions according to Schlünder, neither for the whole medium surface nor for its wet part.

Experimental investigation into the integration of solid desiccant packed beds with oscillating heat pipes for energy efficient isothermal adsorption processes

The heat of adsorption released during physical adsorption of water vapour on solid desiccants increases its surface vapour pressure consequently decreasing its adsorption capacity. In packed beds, this raises the bed temperature subsequently increasing the cooling load and energy required for the regeneration of the solid desiccants. In this study, we experimentally investigated helically coiled oscillating heat pipes (HCOHPs) using ethanol, methanol and deionized water respectively as working fluids integrated with packed beds of varying configurations towards isothermal adsorption. The results show average bed temperature reduction varied with heat output from the bed and the thermal performance of the HCOHPs. The fully packed bed (FPB) integrated with the ethanol HCOHP (EOHP) achieved maximum average bed temperature reduction of 14.0 °C. The annulus packed bed (APB) integrated with the water HCOHP (WOHP) achieved a temperature drop of 10.1 °C. Adsorption peak temperature reductions on the other hand were strongly dependent on HCOHP start-up. Maximum adsorption peak temperature reduction of 20.8 °C in Mass Transfer Zone (MTZ) 1 was attained by the FPB-EOHP integrated system. For the APB, maximum adsorption peak temperature reduction of 13.2 °C in MTZ 3 was recorded for Small APB (SAPB)-Methanol HCOHP (MOHP) integrated system. Adsorption rates in the FPB were influenced by the mal-distribution of flow within the bed and increased slightly on integration with the HCOHPs. Maximum adsorption rates of 1.47 × 10−06 kg/s was achieved by the FPB-EOHP. For the APB, the SAPB-WOHP achieved maximum adsorption rates of 1.21 × 10−05kg/s. The adsorption rates in the Medium APB (MAPB) on the other hand did not appear to be influenced on integration with the HCOHPs. Overall, performances of the integrated systems were found to be influenced partly by the packed bed configuration, the HCOHPs’ performance and the heat transfer resistance between the evaporators and the vessel walls. We recommend further optimization of the system parameters and investigation of its regeneration potential for future practical applications.