Atmospheric Vapor Research Articles

The North American Monsoon buffers forests against the ongoing megadrought in the Southwestern United States.

The US Southwest has been entrenched in a two-decade-long megadrought (MD), the most severe since 800 CE, which threatens the long-term vitality and persistence of regional montane forests. Here, we report that in the face of record low winter precipitation and increasing atmospheric aridity, seasonal activity of the North American Monsoon (NAM) climate system brings sufficient precipitation during the height of the summer to alleviate extreme tree water stress. We studied seasonally resolved, tree-ring stable carbon isotope ratios across a 57-year time series (1960-2017) in 17 Ponderosa pine forests distributed across the NAM geographic domain. Our study focused on the isotope dynamics of latewood (LW), which is produced in association with NAM rains. During the MD, populations growing within the core region of the NAM operated at lower intrinsic and higher evaporative water-use efficiencies (WUEi and WUEE , respectively), compared to populations growing in the periphery of the NAM domain, indicating less physiological water stress in those populations with access to NAM moisture. The disparities in water-use efficiencies in periphery populations are due to a higher atmospheric vapor pressure deficit (VPD) and reduced access to summer soil moisture. The buffering advantage of the NAM, however, is weakening. We observed that since the MD, the relationship between WUEi and WUEE in forests within the core NAM domain is shifting toward a drought response similar to forests on the periphery of the NAM. After correcting for past increases in the atmospheric CO2 concentration, we were able to isolate the LW time-series responses to climate alone. This showed that the shift in the relation between WUEi and WUEE was driven by the extreme increases in MD-associated VPD, with little advantageous influence on stomatal conductance from increases in atmospheric CO2 concentration.

Design and Implementation of Montmorillonite Clay-Based Catalyst for Carbon Nanotube Synthesizing

In this study, a catalyst based on Montmorillonite clay was implemented for carbon nanotubes (CNTs) synthesizing. The kaolinite clay was used as a supporting material for iron-cobalt bimetallic catalytic nanoparticles. The CNTs have been synthesized by using atmospheric chemical vapor deposition (APCVD). To assess the quality of preparation both the catalyst and CNTs have been characterized by different techniques. The chemical bonding and interactions were verified by FT-IR. The general overview of microstructure was examined using SEM, while, the detailed structure and morphology were examined by HR-TEM, in addition to thermal analysis (DTA); surface area (BET); X-ray fluorescence (XRF), Raman spectroscopy, and XRD analysis. The results revealed that; Fe2O3 and Co3O4 NPs were uniformly assembled on the clay nanoplatelets. The specific BET surface area of the clay and catalyst was determined to be 46.12 and 57.06 m2/g respectively. Also, from XRD, the peaks at 26° and 42.7° confirm the presence of CNTs. The FTIR absorption bands, D, G, and G\ bands from the Raman spectrum confirm the hexagonal structure of the CNTs. The obtained results prove the high quality of CNTs preparation.

Unraveling Deposition Atmosphere Impact on Reproducibility of Perovskite Light-Emitting Diodes.

Manipulating the crystallization dynamics of perovskite emitters is an effective strategy for preparing high-performance perovskite light-emitting diodes (PeLEDs). In general, amorphous-like thermodynamically stable intermediates are desirable for a retarded and controllable crystallization process of perovskite emitters. Despite a variety of well-demonstrated strategies for crystallization control, it has been generally realized that perovskite thin-film emitters show problematic reproducibility. Here, we unraveled that the coordinating solvent vapor residues could raise deleterious influences on the formation of amorphous intermediate phases, which thus leads to varying crystal qualities from batch to batch. We demonstrated that undesirable crystalline intermediate phases tend to form with a strong coordination solvent vapor atmosphere, which alters the crystallization process and thus brings about additional ionic defects. By applying an inert gas flush strategy, this detrimental effect could be effectively mitigated, enabling PeLEDs with high reproducibility. This work provides new insight into the fabrication of efficient and reproducible perovskite optoelectronics.

Seaweed fertilizer improved drought tolerance of tomato seedlings in sandy soil

Global climate change has increased atmospheric transpiration and evaporation and decreased rainfall, and these changes have exacerbated water deficit-induced restrictions on agricultural production in arid and semi-arid areas. To test the influence of seaweed fertilization, a product of Qingdao Bright Moon Seaweed Group Co., Ltd®., on tomato drought response in sandy soils, on tomato drought response in sandy soils, a pot experiment was conducted in a greenhouse to measure biomass and leaf parameters, including chlorophyll concentration, relative water content, and carbohydrate and nitrogen content, under two water-availability scenarios including 85 ± 5% field water content and without irrigating treatment (chemical fertilization under well-watered conditions (WW), chemical fertilization under drought-stressed conditions (WD), seaweed fertilization under well-watered conditions (WW + SF), and seaweed fertilization under drought-stressed conditions (WD + SF)). The results showed that under water deficit stress, seaweed fertilization increased soil urease activity (429%) and soil ammonium nitrogen content, thereby increasing the nitrogen content available to the plants. Seaweed fertilization also enhanced the leaf proline content and water content of the plants, and decreased oxidative damage (low malondialdehyde content, which is lower 43.8% compared with WD). In addition, seaweed fertilization increased the leaf nitrogen content and reduced the nonstructural carbohydrate contentto maintain a relatively low total nonstructural carbohydrate/nitrogen (C/N) ratio. Taken together, seaweed fertilization-induced changes improved drought resistance in tomato seedlings and these results suggested that seaweed fertilization has the potential to improve crop drought resistance in sandy areas.

Trace Metals and Metalloids Present in Springwater of a Mining Area: Assessment Based on Chemical and Isotopic Data (δ2H, δ18O, 3H and 87Sr/86Sr)

The Taxco mining district is a well-known international producer of silver, jewelry, and precious metal handicrafts. Inappropriate disposal wastes from anthropogenic activities have been deteriorating the hydric resources and threatening the inhabitants’ health, since they use the springwater for human consumption and domestic activities. A multi-tracer approach combining measurements of hydrochemical data, trace elements, and isotopes δ2H, δ18O, 3H, and 87Sr/86Sr ratios was undertaken for 18 springwater samples. δ18O and δ2H indicate that the springwater comes from the rain and had experienced some degree of isotopic fractionation by atmospheric evaporation in some samples at lower altitudes. 3H values on the springwater showed the existence of old and new water. Three groups of springwater were identified according to age: local flow in rhyolites, intermediate flow through red beds to the outcrop point in sandstone and shales, and deep flow in greenschist. The results of this study show the utility of 87Sr/86Sr ratios in identifying the water–rock interactions and springwater flow paths, suggesting that more widespread use of the strontium isotopic fingerprint is warranted.

Self-Assembly and Sorting of Graphene Nanoplatelets and Spherical Colloidal Particles via Sessile Droplet Evaporation in Saturated Alcohol Vapor

We investigated the dried deposit patterns of quasi-two-dimensional graphene nanoplatelets (GNP) on hydrophilic glass via aqueous sessile droplet evaporation in a saturated alcohol vapor atmosphere. In addition, we studied both the size- and shape-dependent self-assembly and self-sorting of colloids by employing droplets containing bidispersed suspensions comprising GNP and bulk three-dimensional colloidal particles, e.g., polystyrene microspheres (PS). We report distinct self-sorting regimes as the PS diameter Dp varies between 0.1 and 6.4 μm. Under ambient air, the droplet evaporation does not yield discernible self-sorting between GNP and PS. Under saturated alcohol vapor, a critical Dp = 1.1 μm exists, for which the self-sorting does not occur. For Dp < 1.1 μm, the PS sort out from the bidispersed suspension to form the outermost ring of the deposit. The deposit pattern reverses for Dp > 1.1 μm, and GNP deposit on the outermost edge. We corroborate experimental observations with a theoretical model based on the size- and shape-dependent interfacial forces between the colloids.

Isotopic insights on quantitative assessments of interaction of eco-hydrological processes in multi-scale karst watersheds

The dynamics of hydrological processes and the storage mechanisms of karst water resources are the most important issues in karst hydrology. The impact of environmental changes on water quantity, and the evaluation and quantification of eco-hydrological processes remain poorly addressed. In this study, high-frequency continuous monitoring in multi-scale karst watersheds in Southwest China combined the approaches of water isotopes and the hybrid single-particle lagrangian integrated trajectory (HYSPLIT) model to identify the recharge mechanisms between atmospheric vapor, rainfall, surface water, and groundwater, and to reveal the interaction of eco-hydrological processes. The dominant moisture sources in Puding (PD) County were the Indian Ocean (43–69%) and local moisture (24–33%). The δ18O and deuterium excess (d-excess) values showed a positive correlation indicating that secondary or sub-cloud evaporation was prominent in the wet seasons. Karst water line-conditioned excess (lc-excess) indicated that karst water interacted with recent precipitation, groundwater, and evaporation across seasons. Owing to its specific hydrogeological structure, surface water and rainwater have a higher contribution rate to groundwater replenishment. The Chenqi stream replenished the Houzhai River mainly in the form of groundwater, with percentages ranging from 38.1 to 93.5% in the wet season, and 47.8–80.1% in the dry season. In the Houzhai outlet, surface water and groundwater interconverted frequently with a percentage of 45.6–49.1%. We believe this is the first systematic study to quantify the supply relationship between water vapor transport, rainfall, surface water and groundwater in the Chinese karst zone, making a significant move forward in the field of karst hydrological processes and improving the efficiency of water resource evaluation and management.

Disentangling the Key Drivers of Ecosystem Water-Use Efficiency in China’s Subtropical Forests Using an Improved Remote-Sensing-Driven Analytical Model

The subtropical forests in China play a pivotal part in the global and regional carbon–water cycle and in regulating the climate. Ecosystem water-use efficiency (WUE) is a crucial index for understanding the trade-off between ecosystem carbon gain and water consumption. However, the underlying mechanisms of the WUE in forest ecosystems, especially the different subtropical forests, have remained unclear. In this paper, we developed a simple framework for estimating forest WUE and revealing the underlying mechanisms of forest WUE changes via a series of numerical experiments. Validated by measured WUE, the simulated WUE from our developed WUE framework showed a good performance. In addition, we found that the subtropical forest WUE experienced a significant increasing trend during 2001–2018, especially in evergreen and deciduous broadleaf forests where the increasing rate was greatest (0.027 gC kg−1 H2O year−1, p &lt; 0.001). Further analysis indicated that the atmospheric CO2 concentration and vapor pressure deficits (VPD), rather than leaf area index (LAI), were the dominant drivers leading to the subtropical forest WUE changes. When summed for the whole subtropical forests, CO2 and VPD had an almost equal spatial impact on annual WUE change trends and accounted for 45.3% and 49.1% of the whole study area, respectively. This suggests that future forest management aiming to increase forest carbon uptake and protect water resources needs to pay more attention to the long-term impacts of climate change on forest WUE.

The Effectiveness of TiO2 Thermal Barrier Coating in Protecting IN738 LC Super Alloy in an Atmosphere of Sodium Sulfate and Sodium Chloride Vapor at High Temperature

Increasing the efficiency of work and extending the life of metal equipment, which operates under very harsh conditions, requires making the best complex changes in its crystalline structure and properties. In many of the properties of this equipment as a result of the formation of multi-layered metal and ceramic layers in the surface construction of the ingot, thus increasing the efficiency of the ingot and extending its life. The aluminizing was carried out in the presence of a thermal barrier yttrium oxide at 1000 oC, and the oxidation kinetics of the coated structures was studied at 1050 oC and in an atmosphere of mixture sodium chloride vapor and sodium sulfate.

Room-Temperature NO2 Sensing of CVD-Modified WS2–WSe2 Heterojunctions

Two-dimensional (2D) semiconducting heterojunction chemical sensors are in high demand because of their enhanced response, stability, and selectivity. However, fine-tuning heterojunctions using vapor deposition growth still needs further research. Our present study focuses on the ambient pressure chemical vapor deposition (CVD) synthesis of hexagonal tungsten sulfide-tungsten selenide (WS2–WSe2) p–p heterojunctions (as a 2D–2D arrangement). We use the liquid-phase exfoliation method to disperse bulk WS2 and WSe2 and decorate large flakes of WS2 with smaller WSe2 nanosheets in CVD. Electron microscopy and related surface investigations reveal their homogeneity on drop-casting. Two drops from the exfoliated heterojunction dispersion were drop-cast on a transducer to study the NO2 response and related sensing properties. The sensor showed long-term stability (>2 months), even at high humidity levels (40–90%). The gas-sensing properties of this layered p–p heterojunction-based nanocomposite strongly suggest an affinity toward NO2 gas, leading to improved response, high stability, independent of humidity effects, and high selectivity.

NDVI forest cover changes at high altitudes of the Sulaymaniyah Governorate of Kurdistan Region, northern Iraq, 1984−2021

ABSTRACT This study aims to demonstrate the extent of forest cover at high altitudes in Sulaymaniyah Governorate (Province) in the Kurdistan Region in northern Iraq, from 1984 to 2021 and discuss and explain the changes. The forest data were collected from the satellite digital images of the Landsat Thematic Mapper (TM) from 1984 to 2008 and Landsat Operational Land Imager (OLI) from 2014 to 2021. Data preprocessing preparation included employing a radiometric calibration to convert the images from radiance to Top Atmospheric Reflectance (TOA) in order to remove the cosine effect of different solar zenith angles. Next, a quick atmospheric correction (QUAC) was applied to remove atmospheric noise, particles, molecules and vapor from the data; then the basic equation of Normalized Difference Vegetation Index (NDVI) was applied to extract the forest data for 98 samples taken from across the study area. The study shows that forest cover more than doubled during the survey period: in 1984, 9.1% of the study area was covered by forest, but by 2021 forest cover had increased to 18.4%. We discuss how this increase in forest cover is related to better forest management and preservation by the government and by improving the population’s environmental awareness.

Ethylene for carbon doping of GaN by atmospheric pressure metal organic chemical vapor deposition

The carbon incorporation properties of GaN from ethylene and trimethylgallium precursors was studied by atmospheric pressure metal organic chemical vapor deposition. It is found that V-III ratio was the main restriction factor for carbon incorporation. Carbon concentration could be regulated effectively one order of magnitude by tuning V-III ratio for C2H4 doped GaN, and would be enhanced at relatively low V-III ratio for self-doped GaN. Low threading dislocation density and atomic flat surface of C2H4 doped GaN films was kept even if carbon doping concentration of 9E18/cm3 compared with UID-GaN and a high breakdown voltage of 2278 V at leakage current of 10µA was obtained in C2H4 doped GaN buffer layer.

Passivation Improvement of Poly‐SiOx Based TOPCon Contacts by Thermal Annealing in a Water Vapor Atmosphere: Mechanism Exploration and Application Research

AbstractPost‐treatment techniques of tunnel oxide passivated contact (TOPCon) structure are universally implemented via executing an additional hydrogenation process to optimize the passivation performance. However, the underlying physical mechanism and which method is most applicable are still being investigated. Herein, the effectiveness of thermal annealing in water vapor and N2 atmosphere is studied, which is both environmentally friendly and easy to operate. It is demonstrated that compared to other common hydrogenation techniques, the wet N2 outperforms in improving the passivation performance, which can be attributed to the neutralization of internal defects in poly‐Si and the optimization of structural densities, and interestingly, this gain effect is amplified when this contact is doped with oxygen impurity. A power conversion efficiency of 22.62% is achieved using this technology which verifies its reliability and applicability. A loss analysis based on numerical simulations, outlining ways to achieve higher conversion efficiency and highlighting the great potential of this technology is also provided. Extensive experiments and first‐principles calculations based on density‐functional theory are conducted to clarify the underlying dynamics, including the surface adsorption process and the potentiation mechanisms, revealing that passivation and neutralization of hydrogen atoms couple with the compactness optimization of the structure.

Do urban tree hydraulics limit their transpirational cooling? A comparison between temperate and hot arid climates

Evaporative cooling due to transpiration of urban trees in two contrasting climates is the subject of this study. Transpiration was studied experimentally on local tree species at ‘tree lab’ sites in Munich, Germany (temperate climate) and in Beer Sheva, Israel (hot arid climate), within various settings (park, street, square) with natural and sealed surface conditions. The comparison was based on linear relationship of midday canopy resistance to atmospheric vapor pressure deficit (VPD), where the slope is proportional to tree hydraulic conductance and midday stem water potential. Sap flux densities in all trees were similar but crown projected area (CPA) was larger in Beer Sheva, resulting in higher hydraulic resistance that limits transpirational cooling (regression slopes of 0.25–0.44 in Beer Sheva vs. 0.10–0.18 in Munich). The contribution of the transpirational cooling, studied as the proportion of latent heat to total available energy was about 40% less significant at noon hours in summer in Beer Sheva than in Munich. Results suggested that shading should be the main consideration in planting local trees in hot dry climates. The linear relationship of midday canopy resistance to VPD is proposed as an operative tool for comparing evaporative cooling between local trees in different climatic regions.

The shared evaporation history of three sub-Neptunes spanning the radius–period valley of a hyades star

ABSTRACT We model the evaporation histories of the three planets around K2-136, a K-dwarf in the Hyades open cluster with an age of 700 Myr. The star hosts three transiting planets, with radii of 1.0, 3.0, and 1.5 Earth radii, where the middle planet lies above the radius–period valley and the inner and outer planets are below. We use an XMM–Newton observation to measure the XUV radiation environment of the planets, finding that the X-ray activity of K2-136 is lower than predicted by models but typical of similar Hyades members. We estimate the internal structure of each planet, and model their evaporation histories using a range of structure and atmospheric escape formulations. While the precise X-ray irradiation history of the system may be uncertain, we exploit the fact that the three planets must have shared the same history. We find that the Earth-sized K2-136b is most likely rocky, with any primordial gaseous envelope being lost within a few Myr. The sub-Neptune, K2-136c, has an envelope contributing 1–1.7 per cent of its mass that is stable against evaporation thanks to the high mass of its rocky core, whilst the super-Earth, K2-136d, must have a mass at the upper end of the allowed range in order to retain any of its envelope. Our results are consistent with all three planets beginning as sub-Neptunes that have since been sculpted by atmospheric evaporation to their current states, stripping the envelope from planet b and removing most from planet d whilst preserving planet c above the radius-period valley.

Controlled and tunable growth of ambient stable 2D PtS2 thin film and its high-performance broadband photodetectors

PtS2, a group-10 transition metal dichalcogenide (TMDC), has recently attracted enormous interest owing to its tunable band gap (0.25–1.6 eV), high carrier mobility, and large current on-off ratio of the devices. In contrast to other TMDCs, the growth of PtS2 is more difficult, partly due to the nobility of Pt and partly due to the easier formation of the more stable PtS phase rather than PtS2. Herein, we investigate the effect of critical growth parameters like sulfur amount, Pt thickness and gas flow rate for the control and large area growth of PtS2 via thermal assisted conversion process in atmospheric chemical vapour deposition. The detailed characterization using Raman and X-ray photoelectron spectroscopy (XPS) suggests a controlled transition from PtS to PtS2, which can be obtained by fine tuning of these growth parameters. Furthermore, the optimized growth condition of PtS2 is highly reproducible and can be grown on varieties of substrates like SiO2/Si, sapphire, p-type Si, and even on flexible mica substrate. Finally, a high-performance PtS2 photodetector (PD) was fabricated on different substrates. The PD fabricated on SiO2/Si substrate with a detection range covering from visible to NIR region (400–1100 nm) showed a high responsivity and detectivity of 31.38 AW-1 and 3.92 × 1013 Jones, respectively, under 900 nm illumination at a low bias of 1 V. This work demonstrates an effective approach to control the growth of PtS2 on varieties of substrate for high-performance next-generation photodetector for NIR photodetection applications.

A pathway analysis method for quantifying the contributions of precipitation and potential evapotranspiration anomalies to soil moisture drought

Soil moisture drought, as one of the most important drought categories, is determined by both water supply (e.g., precipitation) and demand (e.g., potential evapotranspiration). To shed light on the underlying mechanisms driving soil moisture drought, the statistical multiple linear regression, machine learning, and modeling experiments methods have been pervasively used in early studies. However, these methods neglect the collinearity and interactions of climate variables, and thus cannot reflect the direct and indirect interaction of factors leading to soil moisture drought. To reveal the synergistic effects of water supply and demand on soil moisture drought, this study quantified the contributions of key drivers to the change of soil moisture drought by a path analysis method to exhibit the relationships between atmospheric movement state and soil moisture drought. Prior to applying the systematic path analysis model, we identified the spatial patterns of soil moisture droughts at different depths by using a state-of-art three-dimensional drought recognition method in China. Our results showed that precipitation deficits dominated the interannual variation of soil moisture drought while increasing potential evapotranspiration only had marginal intensification in drought. The response of soil moisture drought to potential evapotranspiration was magnified by drought deterioration, especially in basically severe drought conditions. The total column water vapor and the horizontal divergence of the vapor flux, as well as temperature, directly affected precipitation and potential evapotranspiration and led to soil moisture drought through various direct and indirect processes. This study highlighted that the interactions among precipitation, potential evapotranspiration, and atmospheric vapor movement state in space and time were important for understanding the drought development mechanisms.

Enhancement of Atmospheric Nucleation Precursors on Iodic Acid-Induced Nucleation: Predictive Model and Mechanism.

Iodic acid (IA) has recently been recognized as a key driver for new particle formation (NPF) in marine atmospheres. However, the knowledge of which atmospheric vapors can enhance IA-induced NPF remains limited. The unique halogen bond (XB)-forming capacity of IA makes it difficult to evaluate the enhancing potential (EP) of target compounds on IA-induced NPF based on widely studied sulfuric acid systems. Herein, we employed a three-step procedure to evaluate the EP of potential atmospheric nucleation precursors on IA-induced NPF. First, we evaluated the EP of 63 precursors by simulating the formation free energies (ΔG) of the IA-containing dimer clusters. Among all dimer clusters, 44 contained XBs, demonstrating that XBs are frequently formed. Based on the calculated ΔG values, a quantitative structure-activity relationship model was developed for evaluating the EP of other precursors. Second, amines and O/S-atom-containing acids were found to have high EP, with diethylamine (DEA) yielding the highest potential to enhance IA-induced nucleation by combining both the calculated ΔG and atmospheric concentration of considered 63 precursors. Finally, by studying larger (IA)1-3(DEA)1-3 clusters, we found that the IA-DEA system with merely 0.1 ppt (2.5×106 cm-3) DEA yields comparable nucleation rates to that of the IA-iodous acid system.

Differences in respiration components and their dominant regulating factors across three alpine grasslands on the Qinghai−Tibet Plateau

Greenhouse gases (GHGs) emissions from high-cold terrestrial ecosystems underlain by permafrost on the Qinghai–Tibet Plateau (QTP) have received widespread attention. However, the dominant factors regulating ecosystem respiration (Re) and its components (soil respiration Rs and heterotrophic respiration Rh) and how the differences in carbon emissions from different ecotypes and seasons remain are still unclear. We conducted a 2-year field investigation (August 2018 to October 2020) and applied the structural equation model (SEM) to clarify the changes in the factors controlling the respiration components during different seasons. The results indicate that the Re and its controlling factors in three alpine grassland ecosystems (alpine steppe, alpine meadow, and swamp meadow) vary with seasons. Furthermore, autotrophic respiration (Ra) contributes the most to the seasonal changes in Re. The Re gradually increases in the early growing season and rapidly decreases in the late growing season. Rh remains relatively stable during the year. Under these seasonal variations in the respiration components, the dominant factors controlling Re in the nongrowing season are the temperature of the atmosphere–soil interface (heat flux, atmospheric temperature, and soil temperature at 5 cm depth) and microbial activity (microbial carbon and pH) with the variable importance projections >1.5. During the growing season, the dominant factors regulating Re, Rs, and Rh are the soil temperature with a standardized direct effect (SDE) of 0.424, soil nutrient conditions (total nitrogen and pH) with SDEs of 0.570–0.614, and microbial activity (microbial carbon) with a SDE of 0.591, respectively. In addition, meteorological conditions have an important impact on the respiration components during the growing season. Specifically, the atmospheric vapor pressure is the dominant factor regulating the three respiration components (standardized total effects = 0.44−0.53, p < 0.001). The optimal soil water contents during the growing season (water content at which Re reaches the maximum) are 10% in the alpine steppe, 13%–15% in the alpine meadow, and 40%–43% in the swamp meadow, respectively. The effect of the soil water content on Re is more important in arid ecosystems (alpine steppe and alpine meadow) than in wet ecosystem (swamp meadow). The alleviation of water limitations in arid ecosystems may potentially increase Re.

Regulation of NDVI and ET negative responses to increased atmospheric vapor pressure deficit by water availability in global drylands

Atmospheric vapor pressure deficit (VPD, indicative of atmospheric water conditions) has been identified as a major driver of global vegetation dynamics. Drylands, including deserts, temperate grasslands, savannas, and dry forests, are more sensitive to water conditions and affect carbon, nitrogen, and water cycles. However, our knowledge is limited on the way increasing VPD affects vegetation growth and evapotranspiration (ET) in global drylands. In this study, we used long-term satellite datasets combined with multiple statistical analyses to examine the relationship between the satellite-derived normalized difference vegetation index (NDVI), a proxy for vegetation growth, and ET to VPD across global drylands. We found that significant decreases in NDVI and ET predominantly influenced the NDVI (RVPD − NDVI) and ET (RVPD − ET) responses to VPD in both the savannas and dry forests of South American, African, and Australian savannas and dry forests, as well as in temperate grasslands (e.g., Eurasian steppes and American prairies). Notably, more than 60% of global drylands exhibited significantly negative RVPD − NDVI and RVPD − ET values. In contrast, the percentage of significantly negative RVPD − NDVI and RVPD − ET decreased to &amp;lt;10% in cold drylands (&amp;gt;60° N). In predominantly warm drylands (60° N~60° S), negative VPD effects were significantly and positively regulated by soil water availability, as determined by multiple linear regression models. However, these significant regulatory effects were not observed in cold drylands. Moving-window analyses further revealed that temporal changes in RVPD − NDVI and RVPD − ET were positively correlated with changes in the Standardized Precipitation Evapotranspiration Index (SPEI). In warm drylands, areas with increasing RVPD − NDVI and RVPD − ET over time showed an increasing trend in the SPEI, whereas areas with a decreasing SPEI showed a negative trend in RVPD − NDVI and RVPD − ET values over time. Given the increasing atmospheric dryness due to climate change, this study highlighted the importance of re-evaluating the representation of the role of water availability in driving the response of the carbon-water cycle to increased VPD across global drylands.