Atmospheric Vapor Research Articles

Disentangling the effects of vapor pressure deficit on northern terrestrial vegetation productivity.

The impact of atmospheric vapor pressure deficit (VPD) on plant photosynthesis has long been acknowledged, but large interactions with air temperature (T) and soil moisture (SM) still hinder a complete understanding of the influence of VPD on vegetation production across various climate zones. Here, we found a diverging response of productivity to VPD in the Northern Hemisphere by excluding interactive effects of VPD with T and SM. The interactions between VPD and T/SM not only offset the potential positive impact of warming on vegetation productivity but also amplifies the negative effect of soil drying. Notably, for high-latitude ecosystems, there occurs a pronounced shift in vegetation productivity's response to VPD during the growing season when VPD surpasses a threshold of 3.5 to 4.0 hectopascals. These results yield previously unknown insights into the role of VPD in terrestrial ecosystems and enhance our comprehension of the terrestrial carbon cycle's response to global warming.

A cool runaway greenhouse without surface magma ocean.

Water vapour atmospheres with content equivalent to the Earth's oceans, resulting from impacts1 or a high insolation2,3, were found to yield a surface magma ocean4,5. This was, however, a consequence of assuming a fully convective structure2-11. Here, we report using a consistent climate model that pure steam atmospheres are commonly shaped by radiative layers, making their thermal structure strongly dependent on the stellar spectrum and internal heat flow. The surface is cooler when an adiabatic profile is not imposed; melting Earth's crust requires an insolation several times higher than today, which will not happen during the main sequence of the Sun. Venus's surface can solidify before the steam atmosphere escapes, which is the opposite of previous works4,5. Around the reddest stars (Teff < 3,000 K), surface magma oceans cannot form by stellar forcing alone, whatever the water content. These findings affect observable signatures of steam atmospheres and exoplanet mass-radius relationships, drastically changing current constraints on the water content of TRAPPIST-1 planets. Unlike adiabatic structures, radiative-convective profiles are sensitive to opacities. New measurements of poorly constrained high-pressure opacities, in particular far from the H2O absorption bands, are thus necessary to refine models of steam atmospheres, which are important stages in terrestrial planet evolution.

MyClim: Microclimate data handling and standardised analyses in R

Abstract Microclimates have been recognised as one of the key drivers in global change biology. Durable microclimate loggers, detailed in‐situ measurements and sophisticated modelling tools are increasingly available, but a lack of standardised workflows for microclimate data handling hinders synthesis across the studies and thus progress in the global change biology. To overcome these limitations, we developed an R package myClim for microclimate data processing, storage and analyses. The myClim package supports complete workflow for microclimate data handling, including reading raw logger data files, their preprocessing and cleaning, time‐series' aggregation, calculation of ecologically relevant microclimatic variables, data export and storage. The myClim package stores data in a size‐efficient, hierarchical structure which respects the hierarchy of field microclimate measurement (locality &gt; loggers &gt; sensors). For imported microclimatic data, myClim provides an informative summary and automatically detects and corrects common issues like duplicated and wrongly ordered measurements. The myClim package also provides advanced functions for microclimate data aggregation to various timescales (e.g. days, months, years or growing seasons) as well as tools for sensor calibration, data conversion and joining of multiple microclimatic time series. The myClim package provides advanced functions for standardised calculation of ecologically relevant microclimatic variables like freezing and growing degree days, snow cover period, soil volumetric water content and atmospheric vapour pressure deficit. Calculated microclimatic variables are stored efficiently in myClim data format and can be easily exported to long or wide tables for further analyses and visualisations. Adopting myClim can facilitate large‐scale syntheses, boost data sharing and increase the comparability and reproducibility of microclimatic studies. The stable version of myClim is available on CRAN (https://cran.r‐project.org/web/packages/myClim) and the development version is available on GitHub (https://github.com/ibot‐geoecology/myClim).

Two-dimensional growth of Cu-based materials with a nonvolatile resistive switching behavior

Two-dimensional (2D) crystals have attracted much attention to the application in next-generation non-volatile memories due to their interesting structures and features. Herein, we report the controllable synthesis of 2D Cu2SxSe1– x crystals via a facile ambient pressure vapor deposition method. And the planar and vertical devices on the synthesized Cu2SxSe1– x crystals demonstrate a stable nonvolatile resistance switching. Most importantly, the planar Cu2SxSe1–x devices show a bipolar resistance switching behavior with a memory window of ∼103 and a relatively low operating voltage (<1 V). While the vertical Cu2SxSe1–x device exhibits a unipolar switching behavior with a large memory window of ∼105. Our findings in this work broaden the horizon for the in-situ synthesis of 2D materials and enlighten the possibility of related applications in neural synapse and artificial intelligence.

Energy Surplus and an Atmosphere‐Land‐Surface “Tug of War” Control Future Evapotranspiration

AbstractThe 21st century evapotranspiration (ET) trends over the continental U.S. are assessed using innovative, energy‐based principles. Annual ET is projected to increase with high confidence at the rate of 20 mm for every 1℃ of rise in near‐surface air temperature, or 0.45 or 0.98 mm/year/year, depending on the emission scenario. The ET trajectory is dominated (58%) by the increase of land‐surface net radiative energy. An enhancement of the fraction of energy taken up by ET becomes a more important controller (53%) in late 21st century, under the high emission scenario. This increase is explained by the “tug of war” between atmospheric vapor demand and land‐surface ability to supply water. An assessment of future water availability (precipitation minus ET) shows no significant changes at the continental scale. This outcome nevertheless hides strong spatial variability, emphasizing the role of ET in shaping the distribution of water availability among human populations.

Nonuniformity of magnetization processes of a cobalt-based amorphous alloys in the as-quenched state

The magnetization processes nonuniformity of an amorphous cobalt-based soft-magnetic alloy AMAG-172 (Co-Ni-Fe-Cr-Mn-Si-B) in the as-quenched state were studied. Studies have shown that the main reason of the magnetic characteristics and magnetization processes nonuniformity is the nonuniformity of internal stresses due to the alloy manufacture method. An indirect characteristic of internal stresses is the domains volume with orthogonal magnetization. The observed bimodal field dependence of the magnetic permeability and the field shift of the hysteresis loops in the region of 180-degree domain walls displacement are a consequence of the nonuniformity of the alloy over its thickness. The field shift and the asymmetry of hysteresis loops are explained in terms of the formation of a unidirectional exchange anisotropy at the interface between the ferromagnetic and antiferromagnetic phases of the planar magnetization components oriented along the ribbon axis. The field shift disappearance and the asymmetry of the hysteresis loops along the width of the tape can be interpreted as a decrease in the thickness of the CoO oxide antiferromagnetic layer due to the difference in the concentrations and depth of oxygen and hydrogen atoms penetration induced into the surface of the tape during the manufacture of the tape as a result of interaction with atmospheric vapor.

Effects of plasma treatment on surface insulation properties of epoxy composites

The surface of epoxy composite material working in DC electric field for a long time is easy to accumulate charge and cause flashover, which seriously reduces its insulation level and poses a threat to the safe operation of electrical equipment. In this study, SiO x films were deposited on the surface of nano-SiO2/ER nanoparticles by atmospheric pressure dielectric barrier discharge plasma vapor deposition technology using ethyl nor-silicate as a precursor. The effects of different deposition time on the deposition effect and the pressure level of the film surface were studied. Scanning electron microscope and atomic force microscope were used to characterize the surface morphology of the material, and the flashover voltage before and after deposition was measured. The results show that SiO x films of different thicknesses can be formed on the surface of the material at different times of plasma deposition. After extending the deposition time of the film, the film becomes more uniform and dense, the surface roughness of the material decreases continuously, and the electrical conductivity and flashover voltage along the surface increases continuously. After 10 min plasma treatment, the conductivity increased from 1.78×10−16 S to 2.3×10−13 S, while the flashover voltage along the surface increased from 19.29 kV to 22.66 kV, an increase of about 17.5%.

Structure and tribological properties of MoSe2 films prepared by two-step process

In order to extend the application range of solid lubricant MoSe2, a two-step process was adopted to prepare the MoSe2 film. Namely, the MoSex precursor layer was firstly deposited on the substrate by magnetron sputtering method, and then selenized in a Se vapor atmosphere to obtain MoSe2 film. The effects of the sputtering and selenization process on the structure and tribological properties of the films were investigated. The results show that the two-step prepared MoSe2 films exhibit a preferential orientation with (002) basal plane parallel to the substrate and an improved crystallinity. The prepared MoSe2 film has good wear resistance and lubricating performance in an ambient air environment, with the lowest average friction coefficient of 0.0443 and a specific wear rate of 1.03×10−5 mm3/(N·m). In addition, the lubrication effects of MoSe2 films through the adhesion mechanism and fill in-repair mechanism were further discussed.

Plants lacking OST1 show conditional stomatal closure and wildtype-like growth sensitivity at high VPD.

Climate change-associated rise in VPD (atmospheric vapor pressure deficit) results in increased plant transpiration and reduced stomatal conductance, photosynthesis, biomass, and yield. High VPD-induced stomatal closure of Arabidopsis is an active process regulated via the kinase SnRK2.6 (OPEN STOMATA 1, OST1). Here, we performed gas exchange, leaf water potential and rosette growth measurements to study, whether (1) high VPD-induced stomatal closure is detected in plants carrying loss-of-function mutations in OST1 (ost1-3) when they are grown at reduced soil water content or measured at increased air temperature; (2) ost1-3 plants expressing OST1 construct with no ABA-activation domain, but intact ABA-independent activation, show stronger stomatal VPD response compared with ost1-3 plants; and (3) rosette area and biomass of ost1-3 are more affected by growth at high VPD compared with Col-0. The stomata of well-watered ost1-3 plants were insensitive to high VPD regardless of air temperature, but in deficit-irrigated ost1-3, leaf water potential decreased the most and stomata closed at high VPD. Differences between VPD-induced stomatal closures of ost1-3 plants and ost1-3 plants expressing OST1 with no ABA-activation domain point at gradual VPD-induced ABA-independent activation of OST1. High VPD conditions led to similar reductions in rosette area and specific leaf area of well-watered Col-0 and ost1-3 plants. Rosette dry mass was unaffected by high VPD. Our results show that OST1 loss-of-function plants display conditional stomatal closure and no extra sensitivity of rosette area growth compared with Col-0 wildtype under high VPD conditions.

DREAM

Context. The population of close-in exoplanets features a desert of hot Neptunes whose origin remains uncertain. These planets may have lost their atmosphere, eroding into mini-Neptunes and rocky super-Earths below the desert. Direct observations of evaporating atmospheres are essential to derive mass-loss estimates and constrain this scenario. The metastable He I triplet at 1083.3 nm represents a powerful diagnostic of atmospheric evaporation because it traces the hot gas in extended exoplanet atmospheres while being observed from the ground. In addition, it is located at the bright near-infrared stellar continuum and is very weakly affected by interstellar medium (ISM) absorption. Aims. We carried out a homogeneous He I transmission spectroscopy survey, targeting a selected sample of nine planets along the different edges of the desert, to interpret the absorption line profile with evaporation models and to better understand the role of photoevaporation in the desert formation. Methods. We observed one transit per planet using the high-resolution, near-infrared spectrograph GIANO-B mounted on the Telescopio Nazionale Galileo telescope. We focused our analysis on the He I triplet, based on a comparison of the in-transit and out-of-transit observations, and we computed high-resolution transmission spectra. We then employed the 1D p-winds model to calculate the planetary thermospheric structures and to interpret the observed transmission spectra. Results. We found no signatures of planetary absorption in the He I triplet in any of the investigated targets. We thus provided 3 σ upper-limit estimations on the thermosphere absorption, temperature and mass loss, and combined them with past measurements to search for correlations with parameters such as the stellar mass and XUV flux, which are thought to be key drivers in the formation of the He I triplet. Conclusions. These results strengthen the importance of performing homogeneous surveys and analyses in bringing clarity to He I detections and (thereby) to plausible Neptunian desert origins. Our findings corroborate literature expectations that state the He I absorption signal is correlated with the stellar mass and the received XUV flux. However, when translated in terms of mass-loss rates, these trends seem to disappear. Thus, further studies are essential to shed light on this aspect and to better understand the photoevaporation process.

Water replenishment to maize under heat stress improves canopy temperature and grain filling traits during the reproductive stage

The occurrence of heat often exacerbates drought stress by increasing atmospheric vapor pressure deficit and decreasing transpiration efficiency. Water replenishment to increase soil water content (SWC) could be an effective measure for improving crop resilience in heat. However, field observational evidence and the underlying mechanism for the mitigation were still limited. For this, two widely adopted maize hybrids (ZD958 and XY335) were planted in 2019 and 2020 in North China Plain with three growth environments during the reproductive stage: Normal field conditions (NC), High-temperature episodes (HT) and High-temperature together with elevating SWC (HT-W). Averagely, high temperature reduced grain yield by 21.6-65.1% in HT treatment compared with NC treatment. In HT-W treatment, grain yield was improved by 11.8-13.5% while SWC was elevated by 27.6–51.5% in 0–80 cm soil profile compared with HT treatment. In HT-W treatment, water replenishment to maize under heat stress improved canopy temperature and grain filling traits. The daily maximum canopy temperature was reduced by 1.0–3.1 °C. The effective grain-filling period (Pf) was extended by 1.0–1.6 days and the mean grain-filling rate (Gmean) was increased by 8.2%-10.5%. The improvement of Gmean and Pf for ZD958 was greater than XY335. Furthermore, the significant correlations between SWC in 0–20 cm soil profile and Gmean, and between SWC in 40–80 cm soil profile and Pf for both hybrids were observed. As a result, the fresh weight, volume, and water content of the grain were significantly improved in HT-W treatment compared with HT treatment. Overall, per unit increase in SWC (0–80 cm) decreased the daily maximum canopy temperature by 0.3 °C, increased dry matter accumulation by 1.5%, and grain yield by 2.1%. The information obtained from this study will be helpful to develop efficient management to protect against heat stress in the field.

Extension of droplet/aerosol heat transfer model coupling Lagrangian approach in containment atmosphere under severe accident

Spray droplet dynamics are expected to significantly affect steam condensation, droplet evaporation, and global gas mixing in the containment atmosphere. During severe accidents, droplets may evaporate under high gas temperatures (>200 °C) such as hydrogen fire radiation, and water-soluble aerosols such as CsI and CsHO may dissolve in droplets. An extension of the droplet heat transfer model was conducted to account for these conditions and coupled with a Lagrangian approach for droplet tracking. The approach was comprehensively validated through single droplet experiments, demonstrating the feasibility of this new approach. Analyses of the effects of high atmosphere temperature, droplet curvature, and aerosol solute indicate that, 1) High gas temperature significantly reduces heat transfer, with the effect increasing at higher gas temperatures; 2) Droplet curvature enhances droplet evaporation, but this effect is limited to tiny droplets (<100 nm) compared to other effects; 3) The solute effect significantly impacts small droplet evaporation and dry aerosol growth, dominating the final equilibrium droplet diameter. The extended droplet/aerosol heat transfer model fills a gap in the knowledge of containment spray under severe accidents. A feasible way to approximate the minimum spray droplet size in the heat transfer model is to truncate or initialize the small droplet by the equilibrium diameter.

Thermal and humidification effects of a swimming pool in Hong Kong's humid-subtropical summer

The microclimatic effect of small urban water bodies such as swimming pools has received little attention. This study aimed at (1) comparing the microclimate adjacent to a swimming pool against two control sites and (2) quantifying the pool's cooling and humidification effects. We employed high-precision sensors to measure air temperature, atmospheric vapour pressure, black-globe temperature, and incoming and outgoing radiation at a swimming pool, nearby tennis court and turf sites in Hong Kong's humid-subtropical summer. On sunny days, we found a maximum poolside air temperature of 36.6 °C at 0.15 m height. The highest vapour pressure of 3.14–4.13 kPa occurred on cloudy days. Cooler rainy days lowered vapour pressure. Net short-wave radiation gain peaked at 840 W/m2 on sunny days. The findings suggested that energy stored by the pool in the morning retarded surface cooling later in the day. The morning poolside surface temperature was cooler than the turf by 3.8 °C but warmer by 5.7 °C in the afternoon, with lingering nighttime warming. Unexpectedly, the pool had lower vapour pressure than the control sites. The water body does not ameliorate heat stress on the deck in sunny conditions. The findings hinted that larger recreational blue spaces might generate more thermal and humidification effects.

Study on the fundamental factors of the property evolution of a 300 mm polycrystalline trap-rich layer

The geometry and resistivity of the trap-rich layer are key parameters for 300 mm trap-rich silicon-on-insulator (TR-SOI) wafers. In this paper, the evolution of the warpage and resistivity of poly-Si layers grown by atmospheric chemical vapor deposition with deposition temperature has been studied. The ability to quantify the surface grain size of undoped poly-Si was evaluated using scanning electron microscopy, electron backscattering diffraction, and transmission Kikuchi diffraction (TKD). With a resolution scale of several nanometers, the fine grains on the surface of poly-Si are accurately identified by TKD. It is confirmed that the decrease in compressive stress with deposition temperature is caused by the lower ratio of (110) grain orientation and the reduction of fine grains on the surface. However, when stress is released, the random grain boundaries (GBs) of poly-Si change into coincidence site lattice low-Σ GBs with low recombination activity, which greatly lowers the film bulk resistivity and reduces its capacity to trap charges. Thus, a process window for the manufacturing of 300 mm TR-SOI wafers is created by balancing the degradation of resistivity in the process of using deposition temperature to seek improvements in poly-Si warpage.

Impact of an Aluminization Process on the Microstructure and Texture of Samples of Haynes 282 Nickel Alloy Produced Using the Direct Metal Laser Sintering (DMLS) Technique.

In this study, we examined the effects of an aluminization process on the microstructure and texture of Haynes 282 nickel samples fabricated using the direct metal laser sintering technique. The aluminization process involved the use of chemical vapor deposition with AlCl3 vapors in a hydrogen atmosphere at a temperature of 1040 °C for 8 h. Following the 3D printing and aluminization steps, we analyzed the microstructure of the Haynes 282 nickel alloy samples using light microscopy and scanning electron microscopy. Additionally, we investigated the texture using X-ray diffractometry. A texture analysis revealed that after the process of direct laser sintering of metals, the texture of the Haynes 282 nickel alloy samples developed a texture typical of cast materials. Then, in the aluminization process, the texture was transformed-from foundry-type components to a texture characteristic of recrystallization.

Influence of Solvents and Adsorption of Organic Molecules on the Properties of CVD Synthesized 2D MoS2.

We present a simple method for modification of 2D materials by drop-casting of the organic molecule in solution on the 2D material under ambient conditions. Specifically, we investigated the adsorption of 6-(4,5-Dihydro-1H-imidazol-3-ium-2-yl)-2-(naphthalene-2-yl)benzothiazole methanesulfonate (L63MS) organic molecule on 2D MoS2. To better understand the effect of the organic molecule on the 2D material, we also investigated the impact of solvents alone on the materials' properties. The MoS2 samples were synthesized using ambient pressure chemical vapor deposition. Atomic force microscopy, Raman spectroscopy, photoluminescence spectroscopy and optical microscopy were used to characterize the samples. The measurements were performed after synthesis, after the drop-casting of solvents and after the drop-casting of organic molecule solutions. Our results indicate that the used organic molecule effectively adsorbs on and prompts discernible changes in the (opto)electronic properties of the 2D material. These changes encompass variations in the Raman spectra shape, alterations in the photoluminescence (PL) signal characteristics and modifications in excitonic properties. Such alterations can be linked to various phenomena including doping, bandgap modifications, introduction or healing of defects and that the solvent plays a crucial role in the process. Our study provides insights into the modification of 2D materials under ambient conditions and highlights the importance of solvent selection in the process.

Fast transport diffusion of bound water in cellulose fiber network

AbstractA remarkable property of cellulose-based materials is that they can absorb huge amounts of water (25% of the dry mass) from ambient vapor, in the form of bound water confined at a nanoscale in the amorphous regions of the cellulose structure. The control of the dynamics of sorption and desorption of bound water is a major stake for the reduction of energy consumption and material or structure damages, but in the absence of direct observations this process is still poorly known. Here we present measurements of bound water transport thanks to Nuclear Magnetic Resonance relaxometry and Magnetic Resonance Imaging measurements. We show that the bound water is transported along the fibers and throughout the network of fibers in contact. For each material a single transport diffusion coefficient value allows to represent the processes over the whole range of saturation. The dependence of the transport diffusion coefficient on the fiber density and orientation is then analyzed to deduce the (elementary) transport diffusion coefficient of bound water along a cellulose fiber axis. This constitutes fundamental physical data which may be compared with molecular simulations, and opens the way to the prediction and control of sorption dynamics of all cellulosic materials or other hygroscopic materials.

High Efficiency of Formaldehyde Removal and Anti-bacterial Capability Realized by a Multi-Scale Micro-Nano Channel Structure in Hybrid Hydrogel Coating Cross-Linked on Microfiber-Based Polyurethane.

Inspired by the transpiration in the tree stem having a vertical and porous channel structure, high efficiency of formaldehyde removal is realized by the multi-scale micro-nano channel structure in a hybrid P(AAm/DA)-Ag/MgO hydrogel coating cross-linked on microfiber-based polyurethane. The present multi-scale channel structure is formed by a joint effect of directional freezing and redox polymerization as well as nanoparticles-induced porosity. Due to the large number of vertically aligned channels of micrometer size and an embedded porous structure of nanometer size, the specific surface area is significantly increased. Therefore, formaldehyde from solution can be rapidly adsorbed by the amine group in the hydrogels and efficiently degraded by the Ag/MgO nanoparticles. By only immersing in formaldehyde solution (0.2 mg mL-1) for 12 h, 83.8% formaldehyde is removed by the hybrid hydrogels with a multi-scale channel structure, which is 60.8% faster than that observed in hydrogels without any channel structure. After cross-linking the hybrid hydrogels with a multi-scale channel structure to microfiber-based polyurethane and exposing to the formaldehyde vapor atmosphere, 79.2% formaldehyde is removed in 12 h, which is again 11.2% higher than that observed in hydrogels without any channel structure. Unlike the traditional approaches to remove formaldehyde by the light catalyst, no external conditions are required in our present hybrid hydrogel coating, which is very suitable for indoor use. In addition, due to the formation of free radicals by the Ag/MgO nanoparticles, the cross-linked hybrid hydrogel coating on polyurethane synthetic leather also shows good anti-bacterial capability. 99.99% of Staphylococcus aureus can be killed on the surface. Based on the good ability to remove formaldehyde and to kill bacteria, the obtained microfiber-based polyurethane cross-linked with a hybrid hydrogel coating containing a multi-scale channel structure can be used in a broad field of applications, such as furniture and car interior parts, to simultaneously solve the indoor air pollution and hygiene problems.

Sources of major elements and nutrients in the water cycle of an undisturbed river basin – Samothraki Island, Greece

We studied the origin of elements of an undisturbed stream basin during the dry season as derived by atmospheric inputs and lithological processes. Α mass balance model was applied taking into account atmospheric (rain and vapor) inputs and their origin from marine aerosol and dust, as well as the contribution of rock mineral weathering and dissolution of soluble salts. The model results were enhanced using element enrichment factors, element ratios and water stable isotopes. Weathering and dissolution of bedrock and soil minerals contributed the main element portions, besides sodium and sulfate that chiefly derived from wet deposition. Vapor was shown to contribute water to inland waters of the basin. However, rain was the main source of elements compared to vapor, with marine aerosol being the only atmospheric chloride source, contributing also over 60 % of atmospheric sodium and magnesium. Silicate derived from mineral weathering (mainly plagioclase and amorphous silica), while soluble salt dissolution contributed the main portions of the rest of major elements. In headwater springs and streams, element concentrations were more affected by atmospheric inputs and silicate mineral weathering was more intense, contrary to lowland waters that were more affected by soluble salt dissolution. Effective self-purification processes were mirrored in low nutrient levels, despite the significant inputs from wet deposition, with rain being more important contributor than vapor for the majority of nutrient species. Relatively high nitrate concentrations in headwaters were attributed to increased mineralization and nitrification, while the downstream nitrate diminishing was due to prevailing denitrification processes. The ultimate goal of this study is to contribute in establishing stream elements' reference conditions using mass balance modeling approaches.

Abundance of Dendroctonus frontalis and D. mexicanus (Coleoptera: Scolytinae) along altitudinal transects in Mexico: Implications of climatic change for forest conservation.

Bark beetle infestations have historically been primary drivers of stand thinning in Mexican pine forests. However, bark beetle impacts have become increasingly extensive and intense, apparently associated with climate change. Our objective was to describe the possible association between abundance of bark beetle flying populations and the occurrence of given value intervals of temperature, precipitation and their balance, in order to have a better comprehension of the climatic space that might trigger larger insect abundances, an issue relevant in the context of the ongoing climatic change. Here, we monitored the abundance of two of the most important bark beetle species in Mexico, Dendroctonus frontalis and D. mexicanus. We sampled 147 sites using pheromone-baited funnel traps along 24 altitudinal transects in 11 Mexican states, from northwestern Chihuahua to southeastern Chiapas, from 2015 to 2017. Through mixed model analysis, we found that the optimum Mean Annual Temperatures were 17°C-20°C for D. frontalis in low-elevation pine-oak forest, while D. mexicanus had two optimal intervals: 11-13°C and 15-18°C. Higher atmospheric Vapor Pressure Deficit (≥ 1.0) was correlated with higher D. frontalis abundances, indicating that warming-amplified drought stress intensifies trees' vulnerability to beetle attack. As temperatures and drought stress increase further with projected future climatic changes, it is likely that these Dendroctonus species will increase tree damage at higher elevations. Pine forests in Mexico are an important source of livelihood for communities inhabiting those areas, so providing tools to tackle obstacles to forest growth and health posed by changing climate is imperative.