External Water Vapor Research Articles

Anomalous Water Vapor Circulation in an Extreme Drought Event of the Mid‐Reaches of the Lancang‐Mekong River Basin

AbstractThe middle reaches of the Lancang‐Mekong River Basin (M‐LMRB) experienced a record‐breaking drought event in 2019, resulting in significant economic losses of approximately 650 million dollars and affecting a population of 17 million. However, the anomalous circulation and transportation processes of water vapor, which may have played a crucial role in inducing the extreme drought, have not been fully studied. In this study, we analyze the water vapor circulation during the 2019 drought event using the land‐atmosphere water balance and a backward trajectory model for moisture tracking. Our results indicate that the precipitation in the M‐LMRB from May to October 2019 was only 71.9% of the long‐term climatological mean (1959–2021). The low precipitation during this drought event can be attributed to less‐than‐normal external water vapor supply. Specifically, the backward trajectory model reveals a decrease in the amount of water vapor transported from the Indian Ocean, the Bay of Bengal, and the Pacific Ocean, which are the main moisture sources for precipitation in the region. Comparing the atmospheric circulation patterns in 2019 with the climatology, we identify anomalous anticyclone conditions in the Bay of Bengal, anomalous westerlies in the Northeast Indian Ocean, and an anomalous cyclone in the Western Pacific Ocean, collectively facilitating a stronger export of water vapor from the region. Therefore, the dynamic processes played a more significant role than thermodynamic processes in contributing to the 2019 extreme drought event.

Detection of helical water flows in sub-nanometer channels

Nanoscale flows of liquids can be revealed in various biological processes and underlie a wide range of nanofluidic applications. Though the integral characteristics of these systems, such as permeability and effective diffusion coefficient, can be measured in experiments, the behaviour of the flows within nanochannels is still a matter of speculation. Herein, we used a combination of quadrupolar solid-state NMR spectroscopy, computer simulation, and dynamic vapour sorption measurements to analyse water diffusion inside peptide nanochannels. We detected a helical water flow coexisting with a conventional axial flow that are independent of each other, immiscible, and associated with diffusion coefficients that may differ up to 3 orders of magnitude. The trajectory of the helical flow is dictated by the screw-like distribution of ionic groups within the channel walls, while its flux is governed by external water vapour pressure. Similar flows may occur in other types of nanochannels containing helicoidally distributed ionic groups and be exploited in various nanofluidic lab-on-a-chip devices.

Swelling of Thin Graphene Oxide Film in Water Vapor Studied by In Situ Spectroscopic Ellipsometry.

Graphene oxide (GO) is obtained by the chemical treatment of graphene sheets, resulting in decoration with oxygen-containing functional groups. In the work presented here, we examined marked changes that occur in a thin film of parallel aligned GO sheets when exposed to water vapor at various pressures. It was found that exceptionally fast and substantial water uptake and release occur that is accompanied by major changes in GO interlayer spacing. These characteristics were obtained in situ with spectroscopic ellipsometry. At 99% relative humidity (RH) and 25 °C, the interlayer spacing became 1.41 nm, which recovers to ∼0.8 nm within 30 s when exposed to 10% RH. Besides layer thickness values, uniaxial optical constants for the GO vs RH were derived from the ellipsometry data. Molar refraction theory was applied that indicated monolayer water formation at ∼91% RH at 25 °C upon water adsorption. Our findings contribute to the understanding of the interaction between GO and its environment. The very outspoken effect of external water vapor pressure on GO water content, interlayer spacing, and optical properties can be utilized in sensing and separation devices, subnanometer positioning, chemical switches, and environmentally aware materials.

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.

Evaluation and projection of the summer precipitation recycling over the Tibetan plateau based on CMIP6 GCMs

AbstractBased on ERA5 and 23 CMIP6 models under three Shared Socioeconomic Pathways (SSPs), we assess the performance of CMIP6 models in reproducing the summer precipitation, evaporation and precipitation recycling ratio (PRR) over the Tibetan plateau (TP) during 1981–2014. We also project future changes of the summer precipitation, evaporation, PRR and moisture transport over the TP during 2021–2100. CMIP6 models and their ensemble mean to reproduce the temporal and spatial characteristics of precipitation, evaporation, PRR and moisture transport over the TP. And the performance in simulating precipitation is better than that in simulating evaporation and PRR. The precipitation and evaporation under the three SSPs will increase, with the significant upward trends of 0.84%/decade ~2.79%/decade and 0.80%/decade ~2.14%/decade, respectively. However, the PRR will increase slightly (0.13%/decade) and then marginally reduce (−0.22%/decade). In the late 21st century, regional mean summer precipitation, evaporation and PRR over the TP in SSP5‐8.5 will change by about 20.13%, 17.14%, and −0.77%, respectively. From spatial distribution, precipitation will increase in most parts of the TP in the 21st century, especially in the western part of the plateau, reaching more than 50% in of the late 21st century, the area of PRR decreased gradually expanded, with the maximum reduction (15%–20%) of PRR in the western region. It indicates that more precipitation in the western of the plateau depends on the external moisture transport. The PRR in the southern part of the plateau will increase, with a maximum of more than 20%, which indicates the contribution of the external water vapour transport to the southern precipitation will decrease, and that of the internal cycle (local evaporation) to the local precipitation will increase. In conclusion, the increase of the regional mean precipitation over the TP in the near and mid‐21st century is mainly due to the local evaporation, while the increase of the summer precipitation in the late 21st century is due to both the local evaporation and the external water vapour advection, it shows that the precipitation generated by the inner circulation is becoming weaker and more dependent on the external water vapour transport.

Assessing spatiotemporal characteristics of atmospheric water cycle processes over the Tibetan Plateau using the WRF model and finer box model

The Tibetan Plateau (TP) is the highest and one of the most extensive plateaus in the world and serves as a hotspot of climate change. In the context of climate warming, changes in evapotranspiration (ET) and external water vapor transport have a significant impact on assessing atmospheric water cycle processes over the TP. By using the Weather Research and Forecasting (WRF) model for long-term simulations and the finer box model for the calculation of water vapor along the boundary of the TP, the external atmospheric water vapor transport and its spatiotemporal characteristics over the TP are finely described. The simulated precipitation and ET are well-simulated compared with observation. Research results show that: (1) The total water path on the TP decreases from southeast to northwest. Water vapor is mainly transported into the TP from the western and southern boundaries. The net water vapor flux transported from the western boundary to the TP by westerly wind is negative, while the net water vapor flux transported from the southern boundary to the TP by southerly wind is positive. (2) In spring and winter, water vapor is mainly transported into the TP by mid-latitude westerlies from the western boundary. In summer, water vapor transport controlled by mid-latitude westerlies weakens, and water vapor is mainly transported into the TP from the southern boundary. In autumn, water vapor controlled by mid-latitude westerlies gradually strengthens, and water vapor is mainly transported into the TP from the western boundary. In addition, the ratio of ET to precipitation on the TP is about 0.48, and the moisture recycling is about 0.37. Water vapor mainly comes from external water vapor transport.

Janus polysulfone gradient hollow fiber membranes with interfacial photothermal evaporation by optimization of water transport and thermal management

Interfacial solar evaporation is a promising technology to get fresh water from seawater, because it is free of fossil fuel consumption and carbon dioxide emission. Here, a Janus gradient polysulfone hollow fiber membrane (PSF HFM) with capillary force-driven water transport and 3D evaporation performance was constructed. Different from the traditional 3D evaporation architecture, internal water transport and external water vapor are generated simultaneously. Especially, the outer surface of the membrane can also effectively absorb heat from the environment for cold evaporation because its temperature is lower than the ambient temperature. The obtained 3D PSF HFMs showed a light absorption rate of 93.7 % under simulated sunlight, and an evaporation rate of 2.51 kg·m−2·h−1 under one sun at an ambient temperature of 25 ℃. The evaporation rate of 1.6 kg·m−2·h−1 could be obtained in simulated seawater. The effect of MWCNTs on the evaporation rate was evaluated, showing that the MWCNTs with special water transport pathways were conductive to evaporation process. Overall, this work demonstrates a new direction for the future development of solar-driven evaporation.

Physical Explanation for Paradoxical Climate Change in Semi-Arid Inland Eurasia Based on a Remodeled Precipitation Recycling Ratio and Clausius–Clapeyron Equation

Under global warming, the climate in semi-arid inland Eurasia (SAIE) has changed in an opposite manner, thereby seriously impacting the local ecological environment. However, the key influencing factors and physical mechanism remain inconclusive. In this paper, we remodel the precipitation recycling ratio (PRR) model to assess the contributions of moisture from different water vapor sources to local precipitation, analyze the characteristics of the PRR and precipitation in SAIE, and provide possible physical reasons based on the Clausius–Clapeyron equation. It is found that the PRR increased from 1970 to 2017 as the result of linear trend analysis, with obvious seasonality. Moreover, the component of precipitation contributed by locally evaporated moisture (Pl), and that contributed by advected moisture (Pa) as well as the total precipitation (P), increased during the past 48 years. In particular, the Pa, Pl, and P in autumn and winter all increased obviously during the past 20 years from the interdecadal change trend, as well as the PRR (Pl/P), which was opposite to the decrease in the total water vapor input I(Ω) in the horizontal direction. According to the Clausius–Clapeyron equation, one of the causes might be that global warming has accelerated the local water cycle and driven the increase in Pa, and the increase in atmospheric water holding capacity caused by global warming provides the power source. We suggest that the climate’s transformation from dry to wet in SAIE can only be temporary since SAIE is an inland area and the adjustment of atmospheric circulation did not lead to the increase in external water vapor.

Influence of water vapor influx on interdecadal change in summer precipitation over the source area of the Yellow River Basin

The source area of the Yellow River Basin (SYRB) is located in the northeastern Tibetan Plateau, and the precipitation in the SYRB is of great importance to the water resources throughout the whole basin. By analyzing the summer precipitation in the SYRB, we found that an 11.4% increase in precipitation occurred during 2003–2019 compared with 1982–2002. Such interdecadal increase of summer precipitation was due to significant changes of moisture contribution from external moisture source. In the past 38 years, 95.4% of the water vapor for summer precipitable water in the SYRB came from local evapotranspiration (10.6%), the Tibetan Plateau area (35.8%), central Eurasian area (22.5%), South Asia-northern Indian Ocean area (14.6%), South China Sea-western Pacific area (6.6%), and North Africa-West Asia area (5.3%). Thus, external water vapor supplied about 84.8% of summer precipitable water in the SYRB. Compared with 1990–2002, the relative growth rates of moisture contribution during 2003–2019 from the central Eurasian area, North Africa-West Asia area and South China Sea-western Pacific area increased by 2.40%, 4.55% and 15.07%, respectively. Such interdecadal changes were verified by evapotranspiration minus precipitation for it can illustrate the supply capacity of the moisture source. Water vapor supplies in these areas increased during 2003–2019, which greatly contributed to the increase of summer precipitation in the SYRB.

Environmentally friendly and antimicrobial bilayer structured fabrics with integrated interception and sterilization for personal protective mask

Personal protective mask (PPM) is becoming an effective and convenient apparatus to protect people from harmful air contaminant caused by air pollution and highly infectious respiratory disease. Most of the available PPM can barely possess high capture efficiency towards particulate matters (PMs) and antibacterial activity. Herein, an environmentally friendly and bilayer structured fabric with timely bactericidal efficacy was fabricated through the recombination of silver/zinc two-sides sputtered cotton (SAg/ZnC) and polylactic acid/polycaprolactone (PLA/PCL) composite nanofibers (CNF). A hydroelectricity stimulation was touched off inside the CNF@SAg/ZnC fabric profiting from the external water vapor and then the fabric was given antimicrobial function. The resulting CNF@SAg/ZnC fabric possess intriguing characters, such as high filtration efficiency towards PM0.3 (>99%) with the airflow rate fixed at 85 L/min−1, good antibacterial activity, favorable cell viability, excellent bactericidal ratio against Escherichia coli (99.33%) and Staphylococcus aureus (99.19%) when contact with bacteria for 20 min, and long-lasting durability (>12 h). This work is solely up to the requirements of biodegradable and high-performance media for public health protection, making it a good choice of multi-functional personal protective equipment.

Difference in the atmospheric water cycle over the Hengduan Mountains between wet and dry summers

The atmospheric water cycle over the Hengduan Mountains (HM) is crucial to the local and downstream ecosystem and social economy, while its characteristics and variability have not been thoroughly revealed yet. Based on a bulk method, the atmospheric water cycle over the HM and its difference between wet and dry summers is analysed in this study. Results show that the summer precipitation recycling ratio over the HM is 11.5% in climatology and is significantly and negatively correlated with precipitation there on interannual timescale. In wet summers, the precipitation recycling ratio decreases by 13% compared to dry summers. The origin of water vapour for precipitation over the HM is mainly contributed by the external water vapour transport (local evaporation) in wet (dry) summers. August is found to have the strongest climatological mean precipitation recycling ratio (15.2%) and atmospheric water cycle among 3 months in summer. Also in August, the difference in precipitation recycling ratio between wet and dry summers is largest. In wet summers, although the increase in the external moisture inflow is the largest in June (3.0 × 107 kg·s−1), the increase of precipitation is the largest in August (2.6 × 107 kg·s−1) due to its stronger atmospheric water cycle. Our study promotes the knowledge of the atmospheric water cycle over the HM and provides a new perspective to understand the interannual variations of the precipitation over the HM.

Short-Term Climatic Effect of Gyaring and Ngoring Lakes in the Yellow River Source Area, China

Based on the field observation and WRF-CLM model, the effects of Gyaring and Ngoring lakes on the short-term climate over the Yellow River source area during May to September have been studied through two experiments with and without the lakes. A backward water vapor transfer model was also employed to investigate the contribution of water vapor evapotranspiration from the Gyaring and Ngoring lakes and various surface types to the local precipitation. The results show that without the Gyaring and Ngoring lakes, the sensible heat is increased by 120%, whereas the latent heat is decreased by 58.5%, and the height of atmospheric boundary layer increases from 500 to 1,500–2,000 m during daytime over the lake area. The sum of sensible and latent heat fluxes in the lake area simulated by the experiment with and without the lakes is 185.8 and 130.3 W m−2, respectively. The precipitation amount over the lake area is significantly increased without considering the lake effect, generally by more than 20–40 mm. About 63.8% of the total precipitation in Gyaring and Ngoring lakes is contributed by the external water vapor sources. The evapotranspiration from the grassland is the secondary water vapor source for the precipitation in the Yellow River source area, and 25.2% of the total precipitation is contributed by this source. Around 4.2% of the total precipitation in the lake area is contributed by the evaporation from the Gyaring and Ngoring lakes.

Utilization of WRF 3D Meteorological Data to Calculate Slant Total Delay for InSAR Atmospheric Correction

The atmosphere introduces excess delays into the synthetic aperture radar (SAR) signal trajectory, especially in the troposphere. InSAR atmospheric correction methods include the use of SAR data and external water vapor products. The latter is more effective. However, since the removal of atmospheric effects should use atmospheric delay products in the direction of the line of sight (LOS), it is necessary to convert the zenith total delay to slant delay in the LOS direction. Conventionally, the zenith delay is divided by the cosine of the average incident angles to obtain slant phase delays. But this method could cause large errors because it ignores the atmospheric horizontal gradient change and the small-scale vertical structure. These problems can be solved by using three-dimensional atmospheric data simulated by numerical models, especially in the case of intense weather changes or complex terrain. However, few scholars paid attention to the application into InSAR atmospheric correction, because of the computation complexity and low efficiency. As the requirement for higher accuracy and the introduction of large errors caused by increasing incidence angles, it is significantly imperative to make the utmost of this method. Weather Research Forecast (WRF) model can provide the precipitate water vapor (PWV) and refraction index at different levels in the three dimensions, and then the slant total delay can be obtained for removing the atmospheric effect on the InSAR process. The results demonstrate that using 3D data can obtain more accurate slant total delay and improve the accuracy of surface deformation from InSAR technology.

Clumping Between Carbon Black and Titanium Dioxide Pigment by Water Vapor Absorption and Its Correlation with Electrophoretic Display.

Carbon black and titanium dioxide have been widely used as pigment particles for electrophoretic displays. However, the effect of external water vapor on these pigment particles has not yet been presented. Therefore, in this work, we report the clumping phenomenon between pigment particles as a result of water vapor absorption. To verify clumping between pigment particles, various analysis techniques were used, including scanning electron microscopy, atomic force microscopy, zeta potential measurement, and Raman spectroscopy. We examined the Raman spectrum of carbon black to demonstrate the effect of water vapor absorption on particles. According to the Raman spectrum analysis, the 2D and 2D' peak intensities were significantly increased; moreover, the full widths at half maximum were modified. Thus, we concluded that water vapor absorption on pigment particles can induce the clumping phenomenon on pigments. To protect an electrophoretic display device from external gas transmission, we applied a nanocomposites gas barrier film to the device. The device lifetime was consequently improved by 336%.

Anisotropy of atmospheric delay in InSAR and its effect on InSAR atmospheric correction

Reconstruction of interferometric synthetic aperture radar (InSAR) atmospheric delay maps is important for the correction of tropospheric artifacts in differential InSAR (D-InSAR) and for the improvement in persistent scatterer (PS) target identification in PS-InSAR. In this study, we explored the spatial structure of atmospheric delay datasets and assessed its effect on InSAR atmospheric delay correction. Two-dimensional (2D) experimental variogram maps of turbulent mixing components derived from 12 GPS zenith wet delay (ZWD) datasets, 12 MERIS ZWD datasets, and 3 ERS-1/2 tandem interferograms showed that spatial anisotropy is common in these datasets. An anisotropic variogram model was then developed and applied to fit the experimental variograms. The results showed that the proposed 2D anisotropic variogram model is superior to the isotropic model, with average improvements in 31.92 and 33.57% in terms of root-mean-square error and correlation coefficients, respectively. With the proposed anisotropic variogram model, the atmospheric delay maps were reconstructed by kriging interpolation and used to correct the atmospheric artifacts in InSAR interferograms. The results showed that the model considering the anisotropy of atmospheric delay produces better results than that with the isotropy assumption. Finally, the effects of the anisotropy ratio, sampling density, and correlation distance of external water vapor data on the atmospheric delay correction were investigated. The results showed that when the anisotropy ratio is less than 0.3, or the sampling density is less than 1% or more than 60%, the impact of anisotropy on kriging prediction is not obvious.

Spatiotemporal Distribution of Precipitation Recycling across the Arid Regions of Asia and Africa

The degree of water vapour recycling in terrestrial precipitation is still a debatable topic, particularly in arid regions. Here, the spatiotemporal evolution of evaporation, calculated via the water balance method [1], and the precipitation recycling ratio, calculated using a water recycling model [2], are investigated across Asia and Africa for the 1984-2013 time period. The results show that the precipitation recycling ratio in North Africa and China-Mongolia is stronger in summer but weaker in winter. However, it is stronger in winter and spring in West Asia but weaker in summer. Evaporation accounts for a small proportion of the precipitation uptake in arid regions, with external water vapour transportation exerting the primary influence on precipitation recycling. Increasing global temperatures and evaporation potentials over the past 30 years have driven the actual evaporation and precipitation recycling ratio increases in North Africa and West Asia and corresponding decreases in China-Mongolia.

Diffusive transport of water in magnesium chloride dihydrate under various external conditions for long term heat storage: A ReaxFF-MD study

Pure Magnesium chloride hydrates are exceptional materials for long term thermochemical heat storage. In a heat storage cycle, the material is charged by dehydration, taking up heat, and discharged by hydration, generating heat. On charging, the H2O molecules released by the dehydration reaction have to diffuse through the solid material. Gas–solid interactions play an important role in mass and heat transport throughout the volume of the storage materials. Under certain experimental conditions, the mass transport may become a rate-determining step. In order to simulate the complex reaction coupled diffusion process, a reliable MgCl2–H2O reactive forcefield (ReaxFF) is parameterized using a single parameter search algorithm. The parameters of ReaxFF are trained against a set of data obtained from density functional theory (DFT). ReaxFF-MD simulations are carried out on a 2D periodic slab of MgCl2⋅2H2O to simulate various possible operating conditions of temperature, external water vapor pressure, incomplete dehydration layers and various vacancy defects during a charging–discharging cycle. The diffusion coefficient of H2O through the 2D periodic slab of dihydrate is observed as 1.24±0.37×10−10 m2/sec at 300 K. The diffusivity increases with temperature and follows the Arrhenius equation. External water molecules impede the dehydration and promote the diffusion of water. The vacancies of MgCl2⋅2H2O molecules are characterized using vibrational density of states obtained from ReaxFF-MD simulations. The vacancy concentrations for MgCl2⋅2H2O molecules have been varied from 1.38% to 4.16%, which result in a diffusivity enhancement from 32.9% to 107.7% when compared with perfect slab. The incomplete hydration at the surface and the mid-layer increases diffusivity by 76.7% and 75.0%.

The Role of Application Techniques for High Performance Traditional Renders

Traditional renders based on lime had an aesthetic as well as a protective role for the historic masonry. They were applied in layers in order to ensure good adhesion and cohesion with the substrate but also in order to be functional. The technology of each layer was different in relation to the maximum grain size of the aggregates and the binder/aggregate ratio. Main requirements were the high water vapor permeability, the low water retention in order to avoid salt formation and the capacity of water absorption by capillarity of each layer should increase outwards. As moisture has a detrimental role in the thermal behavior of materials, an effort has been made to record the effect of layering in energy properties. Lime-based renders were tested in relation to their hybrid properties when different application techniques were followed. Two-layer renders with different technological characteristics in each layer were produced. Their behavior, in various deterioration mechanisms such as capillarity, external water uptake (measured by karsten tubes) and water vapor permeability was monitored. It seems that low porosity and adequate permeability is achieved in two-layer renders while the thermal conductivity was effective.

Vapor‐Activated Power Generation on Conductive Polymer

An efficient vapor‐activated power generator based on a 3D polypyrrole (PPy) framework was demonstrated for the first time. By constructing the anions gradient in the PPy, this specially designed PPy framework provided free ionic gradient with the assistant of absorbing water vapor to promote the spontaneous transport of ionic charge carriers, thus leading to the intermittent electric output with the change of external water vapor. A high voltage output of ≈60 mV and power density output of ≈6.9 mW m−2 were achieved under the moisture environment. More interestingly, it also exhibited power generation behaviors upon exposure to most of organic or inorganic vapors, indicating the potential new type of self‐powered vapor sensors for practical applications.

On the effect of water on the Fischer–Tropsch rate over a Co-based catalyst: The influence of the H2/CO ratio

The effect of water partial pressure on the Fischer–Tropsch (FT) rate of a cobalt catalyst supported on narrow-pore γ-Al2O3 was investigated at industrially relevant process conditions (483K, 30bar, pellet size: 53–90μm). Inlet water partial pressure was varied up to 9bar by external water vapour addition at different H2/CO molar ratios ranging from 1 to 3.The effect of water was found to be positive on FT-rate independently of the H2/CO ratio, but more significantly at H2-poor condition.Temperature-programmed hydrogenation (TPH) was used to verify the presence of unreactive carbon species on the catalyst after 22h on stream at the different conditions with and without exposure to about 9bar water. A higher temperature feature that could be associated to amorphous polymeric carbon was detected at H2-poor conditions but remained unchanged upon 2h of water exposure which did not result in a change in the amount of amorphous polymeric carbon detectable by TPH.