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The importance of renewable and environmentally acceptable materials in the construction industry is increasing. Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades, mainly due to the development of modern composites, firstly glue lam, OSB (Oriented Strand Board), LVL (Laminated Veneer Lumber) and a considerable breakthrough was later achieved with the development of cross-laminated timber. In order to enable even more extensive and reliable use of wood in outdoor applications, factors affecting a wood’s service life need to be understood. It is well known that fungal degradation of wood is predominantly affected by temperature and wood moisture content. In order to elucidate the influence of these two factors, long-term monitoring of temperature, relative humidity and moisture content at the newly-built Annex of the Department of Wood Science and Technology was carried out. The Annex is designed from CLT composites and glue-lam beams and was finished in December 2015. The results clearly show that microclimatic conditions in the monitored building in the first years of use are far below the limit required for fungal decay or mould growth.

Relative humidity (RH), an important climatic element influencing tree growth, is also crucial in assessing the General Circulation Models (GCMs) on global warming. However, in the absence of a relatively long record of RH in the Himalayan region, precise modelling of the climate change related processes and their impacts on this region are not well established. Here we present a new RH reconstruction for the pre-monsoon months (February–May) starting from 1800 C.E. using the tree-ring width data of subtropical Pinus roxburghii (chir-pine) from Pithoragarh, Western Himalaya, India. We found significant positive correlation between tree growth and pre-monsoon RH (n = 67, r = +0.569, p

Cross-boundary transport of air pollution is a difficult issue in pollution control for the North China Plain. In this study, an industrial district (Shahe City) with a large glass manufacturing sector was investigated to clarify the relative contribution of fine particulate matter (PM2.5) to the city's high levels of pollution. The Nest Air Quality Prediction Model System (NAQPMS), paired with Weather Research and Forecasting (WRF), was adopted and applied with a spatial resolution of 5 km. During the study period, the mean mass concentrations of PM2.5, SO2, and NO2 were observed to be 132.0, 76.1, and 55.5 μg/m3, respectively. The model reproduced the variations in pollutant concentrations in Shahe at an acceptable level. The simulation of online source-tagging revealed that pollutants emitted within a 50-km radius of downtown Shahe contributed 63.4% of the city's total PM2.5 concentration. This contribution increased to 73.9±21.2% when unfavorable meteorological conditions (high relative humidity, weak wind, and low planetary boundary layer height) were present; such conditions are more frequently associated with severe pollution (PM2.5 ≥ 250 μg/m3). The contribution from Shahe was 52.3±21.6%. The source apportionment results showed that industry (47%), transportation (10%), power (17%), and residential (26%) sectors were the most important sources of PM2.5 in Shahe. The glass factories (where chimney stack heights were normally

Laboratory measurements at the AIDA cloud chamber and airborne in-situ observations suggest that the homogeneous freezing thresholds at low temperatures are possibly higher than expected from the so-called “Koop-line”. This finding is of importance, because the ice onset relative humidity affects the cirrus cloud coverage and, at the very low temperatures of the tropical tropopause layer, together with the number of ice crystals also the transport of water vapor into the stratosphere. Both, the appearance of cirrus clouds and the amount of stratospheric water feed back to the radiative budget of the atmosphere. In order to explore the enhanced ice onset humidities, we re-examine the entire homogeneous ice nucleation process, ice onset and nucleated crystal numbers, by means of a two-moment microphysics scheme embedded in the trajectory based model (CLaMS-Ice) as follows: the well-understood and described theoretical framework of homogeneous ice nucleation yet includes certain formulations of the water activity of the freezing aerosol particles and the saturation vapor pressure of water with respect to liquid water. However, different formulations are available for both parameters. Here, we present extensive sensitivity simulations testing the influence of three different formulations for the water activity and four for the water saturation on homogeneous ice nucleation. We found that the number of nucleated ice crystals is almost independent of these formulations but is instead sensitive to the size distribution of the freezing aerosol particles. The ice onset humidities, also depending on the particle size, are however significantly affected by the choices of the water activity and water saturation, in particular at cold temperatures  205 K. From the CLaMS-Ice sensitivity simulations, we here provide combinations of water saturation and water activity formulations suitable to reproduce the new, enhanced freezing line.

This paper describes the synthesis of La-doped SnO2 nanoparticles for resistive-type relative humidity sensors. The structural characterization of synthesized SnO2 nanoparticles was analyzed using X-ray Diffraction (XRD), that exhibited the formation of the tetragonal rutile structure of pristine and La-doped SnO2 nanoparticles with a decrease in crystallite size in presence of different doping levels. Further increase in doping concentration (at 5 M%) revealed the formation of the La2O3 phase due to the excess amount of lanthanum. The UV–Vis spectroscopy indicates the doping of lanthanum (La) improves the optical property of pristine SnO2. The morphological characterization demonstrates the spherical-shaped nanoparticles. The synthesized nanoparticles were tested for relative humidity (RH) sensing application over the range of 10–100% RH at room temperature. The doping of 3 M% La-doped SnO2 shows good sensitivity (95%) than pristine SnO2 nanoparticles. The fabricated 3 M% La-doped SnO2 sensor not only showed better sensitivity and linear range over 10–100%RH, but also exhibited rapid response (8sec) and recovery (13sec) time than the pristine and the others La-doped levels of SnO2 nanoparticles. This better humidity sensing response of 3 M% La-doped nanoparticles was achieved due to high carrier density and small crystallite size. This indicates 3 M% La-doped nanoparticles is a promising material for room temperature humidity sensing.

Bentonite is low resistance water retaining conductive clayey material often used as grounding enhancement material, particularly in a troubled environment. Due to its unique property, bentonite retains water and dissipate unwanted electrical current to ground. However, bentonite's water retention capacity would inevitably induce corrosion to the grounding electrode and may jeopardize the grounding system's performance in the long run. This study presents bentonite properties on copper electrodes' corrosion behavior. In this study, copper corrosion behavior buried in Andrassy bentonite specimens was investigated under varying relative humidity conditions using the vapor equilibrium technique. The corrosion rate was calculated at equilibrium, and FESEM later characterized the corroded surfaces. The copper corrosion rate in Andrassy bentonite was found to be between 2.2 and 2.8 × 10-3 mm/year. Test results showed that more water might not necessarily induce and expedite copper corrosion. However, it was noted that copper corrosion was somewhat limited under extremely dry conditions and very wet conditions. On the other hand, RH = 75% was the optimum copper corrosion condition to occur. It is believed that the corrosion of copper specimen may be influenced by other complex mechanism presence of such as chemicals species and microbes contained within the bentonite and surrounding environment.

The present work reports on an experimental study carried out on a solar dryer with an external reflector to remove the moisture content available in the grapes. The thermal behavior of the solar dryer with external reflector and open solar drying technique were compared. Using an external reflector on the solar dryer increased the energy input. Results showed that using a solar dryer with external reflectors reduced the drying time while compared to that of open solar drying. The temperature of the dryer tray using an external reflector is increased to about 20% than open basket solar drying. Similarly, the relative humidity of open solar drying is higher as compared to that of the drying chamber with an external reflector. The time required for removing the moisture using a modified solar dryer is found as 5 days, whereas, using open basket solar drying, the time required to remove moisture is 8 days.

New particle formation (NPF) events are an increasingly interesting topic in air quality and climate science. In this study, the particle number size distributions, and the frequency of NPF events over Hefei were investigated from November 2018 to February 2019. The proportions of the nucleation mode, Aitken mode, and accumulation mode were 24.59%, 53.10%, and 22.30%, respectively, which indicates the presence of abundant ultrafine particles in Hefei. Forty-six NPF events occurred during the observation days, accounting for 41.82% of the entire observation period. Moreover, the favorable meteorological conditions, potential precursor gases, and PM2.5 range of the NPF events were analyzed. Compared to non-NPF days, the NPF events preferentially occurred on days with lower relative humidity, higher wind speeds, and higher temperatures. When the PM2.5 was 15–20, 70–80, and 105–115 μg/m3, the frequency of the NPF events was higher. Nucleation mode particles were positively related to atmospheric oxidation indicated by ozone when PM2.5 ranged from 15 to 20 μg/m3, and related to gaseous precursors like SO2 and NO2 when PM2.5 was located at 70-80 and 105–115 μg/m3. On pollution days, NPF events did not directly contribute to the increase in the PM2.5 in the daytime, however, NPF events would occur during the night and the growth of particulate matter contributes to the nighttime PM2.5 contents. This could lead to pollution that lasted into the next day. These findings are significant to the improvement of our understanding of the effects of aerosols on air quality.

Increased grain yield (GY) and grain protein concentration (GPC) are the two main targets of efforts to improve wheat (Triticum aestivum L.) production in the North China Plain (NCP). We conducted a three-year field experiment in the 2014–2017 winter wheat growing seasons to compare the effects of conventional irrigation practice (CI) and micro-sprinkling irrigation combined with nitrogen (N) fertilizer (MSI) on GY, GPC, and protein yield (PY). Across the three years, GY, GPC, and PY increased by 10.5%–16.7%, 5.4%–8.0%, and 18.8%–24.6%, respectively, under MSI relative to CI. The higher GY under MSI was due primarily to increased thousand-kernel weight (TKW). The chlorophyll content of leaves was higher under MSI during the mid–late grain filling period, increasing the contribution of post-anthesis dry matter accumulation to GY, with consequent increases in total dry matter accumulation and harvest index compared to CI. During the mid–late grain filling period, the canopy temperature was markedly lower and the relative humidity was higher under MSI than under CI. The duration and rate of filling during the mid–late grain filling period were also higher under MSI than CI, resulting in higher TKW. MSI increased the contribution of post-anthesis N accumulation to grain N but reduced the pre-anthesis remobilization of N in leaves, the primary site of photosynthetic activity, possibly helping maintain photosynthate production in leaves during grain filling. Total N at maturity was higher under MSI than CI, although there was little difference in N harvest index. The higher GPC under MSI than under CI was due to a larger increase in grain N accumulation than in GY. Overall, MSI simultaneously increased both GY and GPC in winter wheat grown in the NCP.

In this investigation on the mechanical behaviour of paint films, we use a new ferrule-top nanoindentation protocol developed for cultural heritage studies to examine the impact of repeated relative humidity variations on the viscoelastic behaviour of paint films and their mechanical properties in different paint stratigraphies through the changes in their storage and loss moduli. We show that the moisture weathering impact on the micromechanics varies for each of these pigment-oil systems. Data from the nanoindentation protocol provide new insights into the evolution of the viscoelastic properties dsue to the impact of moisture weathering on paint films.

Air pollution in urban areas is a huge concern that demands an efficient air quality control to ensure health quality standards. The hotspots can be located by increasing spatial distribution of ambient air quality monitoring for which the low-cost sensors can be used. However, it is well-known that many factors influence their results. For low-cost Particulate Matter (PM) sensors, high relative humidity can have a significant impact on data quality. In order to eliminate or reduce the impact of high relative humidity on the results obtained from low-cost PM sensors, a low-cost dryer was developed and its effectiveness was investigated. For this purpose, a test chamber was designed, and low-cost PM sensors as well as professional reference devices were installed. A vaporizer regulated the humid conditions in the test chamber. The low-cost dryer heated the sample air with a manually adjustable intensity depending on the voltage. Different voltages were tested to find the optimum one with least energy consumption and maximum drying efficiency. The low-cost PM sensors with and without the low-cost dryer were compared. The experimental results verified that using the low-cost dryer reduced the influence of relative humidity on the low-cost PM sensor results., Bundesministerium für Bildung und Forschung

A unique data set derived from remote sensing, airborne, and ground-based in situ measurements is presented. This measurement report highlights the known complexity of comparing multiple aerosol optical parameters examined with different approaches considering different states of humidification and atmospheric aerosol concentrations. Mie-theory-based modeled aerosol optical properties are compared with the respective results of airborne and ground-based in situ measurements and remote sensing (lidar and photometer) performed at the rural central European observatory at Melpitz, Germany. Calculated extinction-to-backscatter ratios (lidar ratios) were in the range of previously reported values. However, the lidar ratio is a function of the aerosol type and the relative humidity. The particle lidar ratio (LR) dependence on relative humidity was quantified and followed the trend found in previous studies. We present a fit function for the lidar wavelengths of 355, 532, and 1064 nm with an underlying equation of fLR(RH, γ(λ))=fLR(RH=0,λ)×(1-RH)-γ(λ), with the derived estimates of γ(355 nm) = 0.29 (±0.01), γ(532 nm) = 0.48 (±0.01), and γ(1064 nm) = 0.31 (±0.01) for central European aerosol. This parameterization might be used in the data analysis of elastic-backscatter lidar observations or lidar-ratio-based aerosol typing efforts. Our study shows that the used aerosol model could reproduce the in situ measurements of the aerosol particle light extinction coefficients (measured at dry conditions) within 13 %. Although the model reproduced the in situ measured aerosol particle light absorption coefficients within a reasonable range, we identified many sources for significant uncertainties in the simulations, such as the unknown aerosol mixing state, brown carbon (organic material) fraction, and the unknown aerosol mixing state wavelength-dependent refractive index. The modeled ambient-state aerosol particle light extinction and backscatter coefficients were smaller than the measured ones. However, depending on the prevailing aerosol conditions, an overlap of the uncertainty ranges of both approaches was achieved.

Extreme temperatures have warmed substantially over recent decades and are projected to continue warming in response to future climate change. Warming of extreme temperatures is amplified over land, with severe implications for human health, wildfire risk and food production. Using simulations from 18 climate models, I show that hot days over tropical land warm substantially more than the average day. For example, warming of the hottest 5% of land days is a factor of 1.21 ± 0.07 larger than the time-mean warming averaged across models. The climate change response of extreme temperatures over tropical land is interpreted using a theory based on atmospheric dynamics. According to the theory, warming is amplified for hot land days because those days are dry, which is termed the ‘drier get hotter’ mechanism. Changes in near-surface relative humidity further increase tropical land warming, with decreases in land relative humidity being particularly important. The theory advances physical understanding of the tropical climate and highlights land surface dryness as a key factor determining how extreme temperatures respond to climate change. Climate change warms extreme hot days over tropical land more strongly than the mean temperature as hot days are dry, according to a new theory and analysis of global climate models.

Differential absorption radar (DAR) near the 183 GHz water vapor absorption line is an emerging measurement technique for humidity profiling inside of clouds and precipitation with high vertical resolution, as well as for measuring integrated water vapor (IWV) in clear air regions. For radar transmit frequencies on the water line flank away from the highly attenuating line center, the DAR system becomes most sensitive to water vapor in the planetary boundary layer (PBL), which is a region of the atmosphere that is poorly resolved in the vertical by existing spaceborne humidity and temperature profiling instruments. In this work, we present a high-fidelity, end-to-end simulation framework for notional spaceborne DAR instruments that feature realistically achievable radar performance metrics, and apply this simulator to assess DAR's PBL humidity observation capabilities. Both the assumed instrument parameters and radar retrieval algorithm leverage recent technology and algorithm development for an existing airborne DAR instrument. To showcase the capabilities of DAR for humidity observations in a variety of relevant PBL settings, we implement the instrument simulator in the context of large eddy simulations (LES) of 5 different cloud regimes throughout the trade-wind subtropical-to-tropical cloud transition. Three distinct DAR humidity observations are investigated: IWV between the top of the atmosphere and the first detected cloud bin or Earth's surface; in-cloud water vapor profiles with 200 meter vertical resolution; and IWV between the last detected cloud bin and the Earth's surface, which can provide a precise measurement of the sub-cloud humidity. We provide a thorough assessment of the systematic and random errors for all 3 measurement products for each LES case, and analyze the humidity precision scaling with along-track measurement integration. While retrieval performance depends greatly on the specific cloud regime, we find generally that for a radar with cross-track scanning capability, in-cloud profiles with 200 m vertical resolution and 10–20 % uncertainty can be retrieved for horizontal integration distances of 100–200 km. Furthermore, column IWV can be retrieved with 10 % uncertainty for 10–20 km of horizontal integration. Finally, we provide some example science applications of the simulated DAR observations, including estimating near-surface relative humidity using the cloud-to-surface column IWV, and inferring in-cloud temperature profiles from the DAR water vapor profiles by assuming a fully saturated environment.

Heat stress decreases human physical work capacity (PWC), but the extent to which solar radiation (SOLAR) compounds this response is not well understood. This study empirically quantified how SOLAR impacts PWC in the heat, considering wide, but controlled, variations in air temperature, humidity, and clothing coverage. We also provide correction equations so PWC can be quantified outdoors using heat stress indices that do not ordinarily account for SOLAR (including the Heat Stress Index, Humidex, and Wet-Bulb Temperature). Fourteen young adult males (7 donning a work coverall, 7 with shorts and trainers) walked for 1 h at a fixed heart rate of 130 beats∙min−1, in seven combinations of air temperature (25 to 45°C) and relative humidity (20 or 80%), with and without SOLAR (800 W/m2 from solar lamps). Cumulative energy expenditure in the heat, relative to the work achieved in a cool reference condition, was used to determine PWC%. Skin temperature was the primary determinant of PWC in the heat. In dry climates with exposed skin (0.3 Clo), SOLAR caused PWC to decrease exponentially with rising air temperature, whereas work coveralls (0.9 Clo) negated this effect. In humid conditions, the SOLAR-induced reduction in PWC was consistent and linear across all levels of air temperature and clothing conditions. Wet-Bulb Globe Temperature and the Universal Thermal Climate Index represented SOLAR correctly and did not require a correction factor. For the Heat Stress Index, Humidex, and Wet-Bulb Temperature, correction factors are provided enabling forecasting of heat effects on work productivity. Supplementary Information The online version contains supplementary material available at 10.1007/s00484-021-02205-x.

This paper reports on a nanocomposite synthesized by sol–gel procedure comprising graphene sheets with hollow spheres of titanium dioxide (G/HS-TiO2) with varying weight percentages of graphene for the purpose of humidity sensors. The surface morphology of the nanocomposite was characterized using transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). The structural properties were examined using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The response to 12–80% RH at room temperature exhibited sensitivity (S = 135). However, the relative humidity range of 12–90% at room temperature exhibited higher sensitivity (S = 557). Sensors fabricated using the proposed nanocomposite exhibited high sensitivity to humidity, high stability, rapid response times, and rapid recovery times with hysteresis error of less than 1.79%. These results demonstrate the outstanding potential of his material for the monitoring of atmospheric humidity. This study also sought to elucidate the mechanisms underlying humidity sensing performance.

In order for the colloidal crystal films to be better applied, the influence of relative humidity on the preparation of silica colloidal crystal (SCC) films was systematically studied to solve the problem of different thicknesses of SCC films prepared by different batches under the conditions with the same temperature, concentration of suspension and diameter of the particles. SCC films with 190 nm particles were prepared by static vertical deposition method under different humidity regulated by saturated salt solutions, and the thickness of the films was obtained by an interferometric method. The results showed that the increase in humidity would reduce the thickness of the prepared films, which was believed to be caused by the decrease in evaporation rate after the wetting film absorbs water vapor. A new formula for calculating film thickness was proposed and verified from a series of experiments. With the control of humidity, high-quality SCC films with controlled thickness can be repeatedly prepared.

Direct-ink-writing type additive manufacturing with water-based inks such as hydrogels or polymer solutions is broadly utilized for bioprinting applications. However, the resolution of this implementation is limited due to the rapid ink drying experienced at small size scales leading to nozzle clogging and low fidelity prints. To address this issue, a humidity-controlled direct-ink-writing (HCDIW) approach is presented, where the microenvironment around the printing nozzle is controlled through introduction of aerosolized water. Using this approach, the nozzle microenvironment can be varied between undersaturated yet high relative humidity (ambient to 100% RH) to oversaturated conditions where condensing droplets are deposited on the already printed ink filaments. The influence of the aerosolized water and the resultant micro-environment on the printing process was studied using water dissolved sodium carboxymethyl cellulose (NaCMC) ink, specifically focusing on nozzle clogging, printed filament geometry, surface quality and layer by layer stacking. These studies showed that the ink drying induced nozzle clogging issues can be mitigated through increased relative humidity at the nozzle exit and is virtually eliminated for ~100 μm nozzles in oversaturated conditions. The decelerated ink drying under the effect of aerosolized water leads to reduced solute advection and skin formation. This in turn improves surface roughness while reducing adverse effects such as coffee-ring and void formation during additive manufacturing of micro-scale structures. Furthermore, layer-to-layer fusion and associated side-surface quality were improved specifically in undersaturated conditions. Reduction of deposited ink filament concentration in oversaturated conditions leads to excessive spreading of the deposited inks leading to geometric distortions. These results indicate that the humidity control approach can significantly improve the resolution of the direct-ink-writing approaches, enabling processing of water-based inks at micro-scales.

Transportation over longer distances could accelerate the chemical changes of fresh produce. Moreover, fresh produce quality is also influenced by temperature conditions during storage. The present study aims to explore the postharvest quality chemical and nutritional changes in tomatoes as affected by transportation distance and storage conditions. Tomato fruit was transported from a local farm to three distances (100, 154, and 205 km) and delivered to the laboratory to undergo chemical and nutritional quality analysis. Tomatoes were stored at two storage temperature conditions at10°C (95 ± 1% relative humidity) and 22 °C (65 ± 5% relative humidity) for 12 days. To record all vibration data signals, a 3-Axis USB vibration/acceleration data logger was used during transportation. The changes in chemical properties of tomato including total soluble solids (TSS), titratable acidity (TA), sugar:acid ratio (TSS:TA), and pH were measured. Furthermore, nutritional changes (i.e., total lycopene and carotenoids) were determined. Vibration data results recorded 41% of acceleration occurrence in the range interval of 0.0099 -0.0116 m/s2 in the longest distance of road travel. Chemical quality indicators like total soluble solids and sugar/acid ratio were mostly affected (p 0.05) by transportation distance. However, TA was significantly affected by all investigated factors and was lower (0.25%) in tomatoes transported from the farthest distance compared to medium and shortest distances (0.26%) stored at 22 °C. Lycopene and carotenoids were highly affected by all studied factors. The highest amount of lycopene and carotenoids was observed in tomato transported from a long distance and stored at 22 °C on day12 with 1.21 and 1.55 mg.100 g−1 FW, respectively. The temperature during storage and long-distance transportation is critical in reducing postharvest chemical and nutritional quality losses of tomatoes.

Dry food commodities like grains and pulses can be stored safely for several years under controlled storage conditions. The equilibrium moisture content of the packaged grain is one of the most important parameters required to be monitored and controlled for extended safe storage. This paper presents a single element dual-polarized sensing tag based on an annular slot antenna operating at two closely spaced resonant frequencies for radar cross-section-based monitoring of relative humidity in hermetically packaged food commodities. One of the resonant frequencies is functionalized for sensing while the other acts as a built-in reference, mitigating the effects of environmental loading. A polyvinyl alcohol coated interdigitated capacitor, integrated onto the antenna is used as a capacitive transducer for the sensing element. Laboratory scale measurements were carried out using the saturated salt solution method. Results show that the proposed sensor can be used for monitoring a wide range of humidity conditions.

Until now, there has been a lack of knowledge regarding the vertical profiles of nitrate formation in the urban boundary layer (BL) based on triple oxygen isotopes. Here, we conducted vertical measurements of the oxygen anomaly of nitrate (Δ17O-NO3-) on a 325 m meteorological tower in urban Beijing during the winter and summer. The simultaneous vertical measurements suggested different formation mechanisms of nitrate aerosols at ground level and 120 and 260 m in the winter due to the less efficient vertical mixing under stable atmospheric conditions. Particularly, different chemical processes of nitrate aerosols at the three heights were found between clean days and polluted days in the winter. On clean days, nocturnal chemistry (NO3 + HC and N2O5 uptake) contributed to nitrate production equally with OH/H2O + NO2 at ground level, while it dominated aloft (contributing 80% of nitrate production at 260 m), due to the higher aerosol liquid water content and O3 concentration there. On polluted days, nocturnal reactions dominated the formation of nitrate at the three heights. Particularly, the contribution of the OH/H2O + NO2 pathway to nitrate production increased from the ground level to 120 m might be attributed to the hydrolysis of NO2 to HONO and then further photolysis to OH radicals in the day. In contrast, the proportion of N2O5 + H2O decreased at 260 m, likely due to the low relative humidity aloft that inhibited the N2O5 hydrolysis reactions in the residual layer. Our results highlighted that the differences between meteorology and gaseous precursors could largely affect particulate nitrate formation at different heights within the polluted urban BL.

The influence of relative humidity (RH) on the condensational growth of organic aerosol particles remains incompletely understood. Herein, the RH dependence was investigated via a series of experiments for α-pinene ozonolysis in a continuously mixed flow chamber in which recurring cycles of particle growth occurred every 7 to 8 h at a given RH. In 5 h, the mean increase in the particle mode diameter was 15 nm at 0% RH and 110 nm at 75% RH. The corresponding particle growth coefficients, representing a combination of the thermodynamic driving force and the kinetic resistance to mass transfer, increased from 0.35 to 2.3 nm2 s-1. The chemical composition, characterized by O:C and H:C atomic ratios of 0.52 and 1.48, respectively, and determined by mass spectrometry, did not depend on RH. The Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) was applied to reproduce the observed size- and RH-dependent particle growth by optimizing the diffusivities Db within the particles of the condensing molecules. The Db values increased from 5 α-1 × 10-16 at 0% RH to 2 α-1 × 10-12 cm-2 s-1 at 75% RH for mass accommodation coefficients α of 0.1 to 1.0, highlighting the importance of particle-phase properties in modeling the growth of atmospheric aerosol particles.

In this work, a combined respiration and transpiration model is proposed for fresh cape gooseberry fruits, also considering changes in water activity (aw) and moisture content. Initially, a correlation of parameters was obtained from experimental data to determine the kinetics of O2 consumption and CO2 production for cape gooseberry fruits at different temperatures. From the data on the change in gas concentration, a parameter adjustment was made evaluating three kinetic models to represent respiration: 1) Power-Law Chemical kinetics (PL), 2) Simple Michaelis–Menten kinetics (MM), and 3) Michaelis–Menten with uncompetitive inhibition by CO2 (MMU). The temperature-dependence was considered in the three models by integrating an Arrhenius equation in the kinetic parameters. Afterward, a combined model was obtained to describe the fruit transpiration, coupling the moisture sorption isotherm (logistic model), and including the temperature-dependence and the most suitable respiration kinetics. It was determined that with the MMU kinetics it was possible to obtain a high goodness of fit with the experimental behaviour for the changes in the O2 and CO2 concentrations (R2adj. = 0.964 and 0.981). The MM kinetics had an acceptable fit (R2adj. = 0.940 and 0.941), while the PLK model could not explain the observed behaviour (R2adj. = 0.247 and 0.647). It was found that a logistic model appropriately described the relationship between the fruit moisture content and aw (R2adj. = 0.998). A close relationship was determined between the fruit's transpiration and its respiration rate, the change in the water activity, and the surrounding temperature and relative humidity (R2adj. = 0.998). As the temperature decreased, and as the relative humidity increased, the change in water activity and the transpiration rate decreased. Through the parameters established for each model, it is possible to predict the behaviour of processes such as respiration, transpiration, and changes in aw to configure a storage and packaging system by proposing the gas balance equations (O2, CO2, and water vapour) that allow obtaining favourable gas levels for the preservation of the fresh fruits.

Arctic low clouds and the water they contain influence the evolution of the Arctic system through their effects on radiative fluxes, boundary layer mixing, stability, turbulence, humidity, and precipitation. Atmospheric models struggle to accurately simulate the occurrence and properties of Arctic low clouds, stemming from errors in both the simulated atmospheric state and the dependence of cloud properties on the atmospheric state. Knowledge of the contributions from these two factors to the model errors allows for the isolation of the process contributions to the model–observation differences. We analyze the differences between the Arctic System Reanalysis version 2 (ASR) and data taken during the September 2014 Arctic Radiation–IceBridge Sea and Ice Experiment (ARISE) airborne campaign conducted over the Beaufort Sea. The results show that ASR produces less total and liquid cloud water than observed along the flight track and is unable to simulate observed large in-cloud water content. Contributing to this bias, ASR is warmer by nearly 1.5 K and drier by 0.06 g kg−1 (relative humidity 4.3 % lower) than observed. Moreover, ASR produces cloud water over a much narrower range of thermodynamic conditions than shown in ARISE observations. Analyzing the ARISE–ASR differences by thermodynamic conditions, our results indicate that the differences are primarily attributed to disagreements in the cloud–thermodynamic relationships and secondarily (but importantly) to differences in the occurrence frequency of thermodynamic regimes. The ratio of the factors is about 2/3 to 1/3. Substantial sampling uncertainties are found within low-likelihood atmospheric regimes; sampling noise cannot be ruled out as a cause of observation–model differences, despite large differences. Thus, an important lesson from this analysis is that when comparing in situ airborne data and model output, one should not restrict the comparison to flight-track-only model output.

Low-power consumption and high sensitivity are highly desirable for a vast range of NH3 sensing applications. As a new type of two-dimension (2D) material, Ti3C2Tx is extensively studied for room temperature NH3 sensors recently. However, the Ti3C2Tx MXene based gas sensors suffer mainly from low sensitivity. Herein, we report a sensitive Ti3C2Tx/WO3 composite resistive sensor for NH3 detection. The Ti3C2Tx/WO3 composite consisting of WO3 nanoparticles anchored on Ti3C2Tx nanoflakes were synthesized successfully with a facile ultra-sonication technique. The composite sensor with optimized components exhibits a high sensitivity of 22.3% for 1 ppm NH3 at room temperature, which is 15.4 times higher than the pure Ti3C2Tx sensor. Furthermore, the composite sensor has excellent reproducibility, good long-term stability, and high selectivity to NH3. The relative humidity influence on NH3 gas sensing properties of the sensors was systematically studied. This research provides an efficient route for the preparation of novel MXene-based sensitive materials for high-performance NH3 sensors.

This paper examines two needle-punched geosynthetic clay liners' water retention behaviour at high suction ranges using the vapour equilibrium technique where super-saturated salt solutions controlled the relative humidity. This study shows that the bentonite form and its mineralogy affect the absorption/desorption of GCLs and their corresponding water retention curves. In particular, a granular bentonite-based GCL was found to absorb more and release less water than a powdered bentonite-based GCL due to its higher montmorillonite content and larger pores. The water retention curves of both GCLs exhibited very little hysteretic behaviour at high suction. Repeated wetting-drying cycles shifted the WRCs of both GCLs slightly downward with minimal impact on their degree of hysteresis.

Lighting is a critical component in a museum environment because, together with temperature, relative humidity and pollutants, it is one of the damaging factors able to produce long‐term, cumulative and irreversible photodegradation processes. To correctly preserve artworks, limiting illuminance and exposure is recommended, allowing on one side the preservation of the object, but on the other limiting the display of the object, especially for sensitive materials. The aim of this research was to develop, evaluate and compare a new lighting method for paintings and other cultural materials to improve the experience of the objects whilst reducing the risks from exposure. The idea is based on the use of selective chromatic light where the component of the spectrum absorbed by the materials is removed. This absorption is the principal cause of photodegradation. The proposed lighting system can be obtained by combining different types of projection systems together with filtering using an appropriate light source. Six methods of light projection have been compared for two mock-ups simulating real artworks with high and medium light sensitivity. The efficiency of illumination increased from 30% to 111% compared to standard lighting systems. Light stability tests were additionally performed, finding reduced colour changes compared to traditional lighting systems.

The architecture of rice plant represents important and complex agronomic traits, such as panicles morphology, which directly influence the microclimate of rice population and consequently grain yield. To enhance yield, modification of plant architecture to create new hybrid cultivars is considered a sustainable approach. The current study includes an investigation of yield and microclimate response index under low to high plant density of two indica hybrid rice R498 (curved panicles) and R499 (erect panicles), from 2017 to 2018. The split-plot design included planting densities of 11.9–36.2 plant/m2. The results showed that compared with R498, R499 produced a higher grain yield of 8.02–8.83 t/ha at a higher planting density of 26.5–36.2 plant/m2. The response index of light intensity and relative humidity to the planting density of R499 was higher than that of R498 at the lower position of the rice population. However, the response index of temperature to the planting density of R499 was higher at the upper position (0.2–1.4%) than at the lower position. Compared with R498, R499 at a high planting density developed lower relative humidity (78–88%) and higher light intensity (9900–15,916 lx) at the lower position of the rice population. Our finding suggests that erect panicles are highly related to grain yield microclimatic contributors under a highly dense rice population, such as light intensity utilization, humidity, and temperature. The application of erect panicle rice type provides a potential strategy for yield improvement by increasing microclimatic conditions in rice.

International audience; Rising air pollution by surface ozone (O 3) in China has induced extensive efforts to control ozone generation in major urban and industrial areas, yet mechanisms ruling the ozone production and loss are not well understood. In particular, ozone levels are strongly influenced by meteorological factors such as relative humidity, but this has been explored only in local situations, and the effect of relative humidity on ozone levels in warm seasons on a large scale in China is still unknown. Here we studied surface ozone, relative humidity, temperature, and other meteorological variables in 74 major cities in China during 2017-2018, focusing on the warm seasons in seven regions. Results show that ozone levels decrease with increasing relative humidity in all cities, with an average correlation coefficient of − 0.58, ranging from − 0.17 in Zhangjiakou to − 0.84 in Hengshui. At high relative humidity levels, above 75%, average ozone levels ranged from 44.6 to 122.5 μg m −3 , which is lower than Chinese quality threshold of hourly average ozone level of 200 μg m −3. The decreases of ozone with relative humidity were more pronounced at high temperature, above 30 °C, than below 25 °C. The increases of ozone with temperature were more pronounced at low relative humidity, below 40%. Overall, our findings reveal that mechanisms ruling surface ozone levels are similar on a large scale. This is promising to design common methods of climate engineering to protect human health.

Accurate characterization of the water activity and hygroscopicity of aqueous aerosol material allows us to predict the chemical and physical state of aerosol particles exposed to humid conditions in the environment. The hygroscopicity of aerosol determines the size, phase morphology, viscosity, chemical reactivity, and optical properties of constituent particles and directly impacts their ability to form clouds in the atmosphere. In this work, we describe measurements of hygroscopicity using a linear quadrupole electrodynamic balance (LQ-EDB). We levitate two droplets, one droplet that acts as a relative humidity (RH) probe and one sample droplet, and expose them to controlled environmental conditions. We describe the development of an RH measurement using probe droplets of aqueous NaCl or LiCl, allowing for precise in situ measurements of RH in the LQ-EDB chamber. We demonstrate that the RH may be determined with an accuracy of 0.5 % at 50 % RH and better than 0.1 % at 90 % RH using NaCl, and we show that LiCl is effective at characterizing the RH from ∼ 10 % RH up to ∼ 90 %. We simultaneously measure the response of sample droplets containing aqueous material (including ammonium sulfate, citric acid, 1,2,6-hexanetriol, and tetra-ethylene glycol) and report hygroscopic growth via their radial growth factors. We use established thermodynamic models to validate the accuracy of the RH probe and to compare with the measured hygroscopicity of the samples. This approach shows significant advantages over other methods for accurately characterizing the hygroscopicity of samples with a range of characteristics, such as high viscosity and vapor pressure.

Liquid water in aerosol particles has a significant effect on their optical properties, especially on light scattering, whose dependence on chemical composition is investigated here using measurements made in southern Beijing in 2019. The effect is measured by the particle light scattering enhancement f(RH), where RH denotes the relative humidity, which is found to be positively and negatively impacted by the proportions of inorganic and organic matter, respectively. Black carbon is also negatively correlated. The positive impact is more robust when the inorganic matter mass fraction was smaller than 40 % (R=0.93, R: the Pearson's correlation coefficient), becoming weaker as the inorganic matter mass fraction gets larger (R=0.48). A similar pattern was also found for the negative impact of the organic matter mass fraction. Nitrate played a more significant role in aerosol hygroscopicity than sulfate in Beijing. However, the deliquescence point of ambient aerosols was at about RH = 80 % when the ratio of the sulfate mass concentration to the nitrate mass concentration of the aerosol was high (mostly higher than ∼ 4). Two schemes to parameterize f(RH) were developed to account for the deliquescent and non-deliquescent effects. Using only one f(RH) parameterization scheme to fit all f(RH) processes incurs large errors. A piecewise parameterization scheme is proposed, which can better describe deliquescence and reduces uncertainties in simulating aerosol hygroscopicity.

In this paper, a unique Armalcolite-PDMS-based flexible capacitive humidity sensor is designed by using spin coating technique, which uses interdigitated gold (Au) electrode and ultrathin ( $\sim 80~\mu \text{m}$ ) flexible polyimide substrate. The structural and morphological properties of the Armalcolite nanocomposite are characterized by X-ray diffraction (XRD) and SEM. The electrical characterization of the Armalcolite-PDMS-based flexible capacitive humidity sensor is performed at 25 °C, followed by relative humidity ranging from 33% to 95% and frequency varying 102 Hz to 106 Hz. The experimental investigation reveals a fast response time (8.53 s) and recovery time (11.25 s). The developed sensor exhibits a reversible response with ultra-low hysteresis of 0.92%. The sensor response is recorded for 30 days to confirm its long-term stability. The sensing mechanism is studied using impedance plots obtained at different humidity environments. The excellent sensing performance of the developed sensor could be beneficial for the researchers working in the area of flexible humidity sensors.

Water uptake abilities of organic aerosol under sub-saturated conditions play critical roles in direct aerosol radiative effects and atmospheric chemistry; however, field characterizations of the organic aerosol hygroscopicity parameter κOA under sub-saturated conditions remain limited. In this study, a field campaign was conducted to characterize κOA at a relative humidity of 80 % with hourly time resolution for the first time in the Pearl River Delta region of China. Observation results show that, during this campaign, secondary organic aerosol (SOA) dominated total organic aerosol mass (mass fraction > 70 % on average), which provides a unique opportunity to investigate influences of SOA formation on κOA. Results demonstrate that the commonly used organic aerosol oxidation level parameter O/C was weakly correlated with κOA and failed to describe the variations in κOA. However, the variations in κOA were well reproduced by mass fractions of organic aerosol factor resolved based on aerosol mass spectrometer measurements. The more oxygenated organic aerosol (MOOA) factor, exhibiting the highest average O/C (∼ 1) among all organic aerosol factors, was the most important factor driving the increase in κOA and was commonly associated with regional air masses. The less oxygenated organic aerosol (LOOA; average O/C of 0.72) factor revealed strong daytime production, exerting negative effects on κOA. Surprisingly, the aged biomass burning organic aerosol (aBBOA) factor also formed quickly during daytime and shared a similar diurnal pattern with LOOA but had much lower O/C (0.39) and had positive effects on κOA. The correlation coefficient between κOA and mass fractions of aBBOA and MOOA in total organic aerosol mass reached above 0.8. The contrasting effects of LOOA and aBBOA formation on κOA demonstrate that volatile organic compound (VOC) precursors from diverse sources and different SOA formation processes may result in SOA with different chemical composition, functional properties and microphysical structure, consequently exerting distinct influences on κOA and rendering single oxidation level parameters (such as O/C) unable to capture those differences. Aside from that, distinct effects of aBBOA on κOA were observed during different episodes, suggesting that the hygroscopicity of SOA associated with similar sources might also differ much under different emission and atmospheric conditions. Overall, these results highlight that it is imperative to conduct more research on κOA characterization under different meteorological and source conditions and examine its relationship with VOC precursor profiles and formation pathways to formulate a better characterization and develop more appropriate parameterization approaches in chemical and climate models.

Due to the expansion of human production activities, toxic ammonia (NH3) is excessively released into the atmosphere, being a huge threat to human health and the natural environment. Therefore, it is of great significance to design an easy-synthesized gas-sensing material with both good room temperature sensitivity and selectivity for trace-level NH3 detection. Herein, we fabricate a chemiresistive NH3 gas sensor with enhanced performance based on Ni(OH)2/Ti3C2Tx hybrid materials. The Ni(OH)2/Ti3C2Tx hybrid materials are synthesized by an in-situ electrostatic self-assembly method. Attributed to the formation of interfacial heterojunctions and the modulation of carrier density, the Ni(OH)2/Ti3C2Tx hybrid sensor exhibits high response, outstanding repeatability, good selectivity and stability in low concentrations of NH3. Moreover, the Ni(OH)2/Ti3C2Tx hybrid sensor has a higher response to 10 ppm NH3 at the relative humidity of 40% and 60%, which makes it promising for applications in real complex environments with high humidity. Benefitting from the low power consumption and easy fabrication process, the Ni(OH)2/Ti3C2Tx hybrid sensor possesses a broad application prospect in the internet of things (IoT) environmental monitoring.

Li-ion-conducting chloride solid electrolytes receive considerable attention due to their physicochemical characteristics such as high ionic conductivity, deformability and oxidative stability. However, the raw materials are expensive, and large-scale use of this class of inorganic superionic conductors seems unlikely. Here, a cost-effective chloride solid electrolyte, Li2ZrCl6, is reported. Its raw materials are several orders of magnitude cheaper than those for the state-of-the-art chloride solid electrolytes, but high ionic conductivity (0.81 mS cm–1 at room temperature), deformability, and compatibility with 4V-class cathodes are still simultaneously achieved in Li2ZrCl6. Moreover, Li2ZrCl6 demonstrates a humidity tolerance with no sign of moisture uptake or conductivity degradation after exposure to an atmosphere with 5% relative humidity. By combining Li2ZrCl6 with the Li-In anode and the single-crystal LiNi0.8Mn0.1Co0.1O2 cathode, we report a room-temperature all-solid-state cell with a stable specific capacity of about 150 mAh g–1 for 200 cycles at 200 mA g–1., Stable inorganic solid electrolytes are instrumental in developing high-voltage Li metal batteries. Here, the authors present the synthesis and electrochemical energy storage properties of a cost-effective and humidity-tolerant chloride solid electrolyte.

Restricted by experimental conditions, it is difficult to analyze reactants distribution and uniformity through experiment. A simulation model is established by experiment fuel cell. Hydrogen humidification has a great impact on hydrogen distribution and concentrates in inlet and serpentine sections. At anode side membrane water content increases significantly when hydrogen relative humidity is over 50%. Air humidification has little effect on air distribution and water content. The oxygen mass fraction only decreases with relative humidity increase. Hydrogen humidification has greater influence on the distribution of reactants and membrane water content than air humidification, but hydrogen humidification needs to control the relative humidity of hydrogen within a suitable range. According to the simulation results in this article, the relative humidity of hydrogen should be controlled at 25%–50%. This paper proposes mass fraction difference coefficient, as uniformity evaluation index. When hydrogen relative humidity is 50%, uniformity of reactants distribution is the best.

Background Patients with ankylosing spondylitis (AS) have reported that their pain becomes worse when the local weather changes. However, there is limited evidence verifying the short-term associations between meteorological factors and outpatient visits for patients with AS. Therefore, this study evaluates this possible association. Methods Meteorological data and data on daily AS outpatient visits to a general hospital in Hefei, China, from 2014 to 2019 were collected and analysed. Distributed lag nonlinear models and Poisson regression models were employed to determine the association between weather conditions and outpatient visits; the results were also stratified by gender and age. Results High relative humidity is significantly associated with all patient visits in lag 1 (RR = 1.113, 95% CI 1.021 to 1.213) and lag 7 days (RR = 1.115, 95% CI 1.014 to 1.227). A low relative risk to the nadir is observed in lag 4 days (RR = 0.920, 95% CI 0.862 to 0.983). Male and young patients ( Conclusions Our findings suggest a potential relationship between exposure to weather conditions and increased risk of AS outpatient visits. These results can aid hospitals in preparing for and managing hospital visits by AS patients when the local weather conditions change.

AimCardiopulmonary resuscitation (CPR) is an emergency procedure where interpersonal distance cannot be maintained. There are and will always be outbreaks of infection from airborne diseases. Our objective was to assess the potential risk of airborne virus transmission during CPR in open-air conditions.MethodsWe performed advanced high-fidelity three-dimensional modelling and simulations to predict airborne transmission during out-of-hospital hands-only CPR. The computational model considers complex fluid dynamics and heat transfer phenomena such as aerosol evaporation, breakup, coalescence, turbulence, and local interactions between the aerosol and the surrounding fluid. Furthermore, we incorporated the effects of the wind speed/direction, the air temperature and relative humidity on the transport of contaminated saliva particles emitted from a victim during a resuscitation process based on an Airborne Infection Risk (AIR) Index.ResultsThe results reveal low-risk conditions that include wind direction and high relative humidity and temperature. High-risk situations include wind directed to the rescuer, low humidity and temperature. Combinations of other conditions have an intermediate AIR Index and risk for the rescue team.ConclusionsThe fluid dynamics, simulation-based AIR Index provides a classification of the risk of contagion by victim’s aerosol in the case of hands-only CPR considering environmental factors such as wind speed and direction, relative humidity and temperature. Therefore, we recommend that rescuers perform a quick assessment of their airborne infectious risk before starting CPR in the open air and positioning themselves to avoid wind directed to their faces.

Titanium carbide (Ti3C2Tx) with a distinctive structure, abundant surface chemical groups, and good electrical conductivity has shown great potential in fabricating superior gas sensors, but several challenges, such as low response kinetics, poor reversibility, and serious baseline drift, still remain. In this work, γ-poly(l-glutamic acid) (γ-PGA) with a blocking effect is exploited to modify Ti3C2Tx, thereby stimulating the positive response behavior of Ti3C2Tx and improving its gas sensing performance. On account of the unique synergetic interaction between Ti3C2Tx and γ-PGA, the response of the flexible Ti3C2Tx/γ-PGA gas sensor to 50 ppm NO2has been improved to a large extent (average 1127.3%), which is 85 times that of Ti3C2Tx (only 13.2%). Moreover, the as-fabricated Ti3C2Tx/γ-PGA sensor not only exhibits a shorter response/recovery time (average 43.4/3 s) compared with the Ti3C2Tx-based sensor (∼18.5/18.3 min) but also shows good reversibility and repeatability (relative standard deviation (RSD)

Improving seed yield and oil quality of oilseed crops can aid in provision of a nutritious diet for humans. A worldwide collection of linseed was evaluated for seed yield (YLD), seed oil (OIL) and protein content (PRO), oil fatty acid composition, omega-3 to omega-6 ratio (ω3/ω6), total tocopherol content (TTC), and total phenolic content (TPC). At 2 years, higher temperature (~7%) and lower relative humidity (~16.6%) during the seed filling and maturity period (dryer condition) were correlated with significant decreases in YLD (~18%) and OIL (~4.5%), lower contents of linolenic acid (~13%) and TTC (9.8%), and lower ω3/ω6 ratio (~31%); oleic (~9%) and linoleic acid contents (~23%) and TPC (14.4%) increased. Correlation results demonstrated some significant associations among quantitative traits such as YLD, OIL, and thousand seed weight (TSW); however, the association of these traits with qualitative indices was mostly negative. Genotypes were classified irrespective of their geographical origin and independent of seed or flower colour. In this classification, a yellow-seeded Canadian group had the lowest ω3/ω6 ratio (~0.05), the highest seed yield and high TTC, whereas groups with the highest ω3/ω6 ratio (>3.0) had the lowest oil TTC and low to average seed yield. Results suggested that some brown-seeded Asian genotypes with high grain yield and oil potential, higher ω3/ω6 ratio, and other more stable oil quality indices are suitable to develop broadly adaptive varieties under the possible fluctuation of climatic factors. Other genetic groups could also be used for breeding programs with specific objectives.

Atmospheric aerosols consisting of organic and inorganic components may undergo liquid–liquid phase separation (LLPS) and liquid–solid phase transitions during ambient relative humidity (RH) fluctuation. However, the knowledge of dynamic phase evolution processes for mixed organic–inorganic particles is scarce. Here we present a universal and visualized observation of LLPS, efflorescence and deliquescence transitions as well as hygroscopic growth of laboratory-generated mixed 1, 2, 6-hexanetriol / ammonium sulfate (AS) particles with different organic–inorganic mole ratios (OIR = 1:4, 1:2, 1:1, 2:1 and 4:1) with high time resolution (0.5 s) using an optical microscope operated with a video camera. The optical images suggest that an inner AS solution phase is surrounded by an outer organic-rich phase after LLPS for all mixed particles. The LLPS mechanism for particles with different OIRs is found to be distinct; meanwhile, multiple mechanisms may dominate successively in individual particles with a certain OIR, somewhat inconsistently with previously reported observations. More importantly, another phase separation in the inner AS solution phase, defined as secondary LLPS here, is observed for OIR = 1:1, 1:2 and 1:4 particles. The secondary LLPS may be attributed to the formation of more concentrated AS inclusions in the inner phase and becomes more obvious with decreasing RH and increasing AS mole fraction. Furthermore, the changes in size and number of AS inclusions during LLPS are quantitatively characterized, which further illustrate the equilibrium partitioning process of organic and inorganic components. These experimental results have significant implications for the revelation of complex phase transitions of internally mixed atmospheric particles and evaluation of liquid–liquid and liquid–solid equilibria in thermodynamic models.

The aim of the present study was to determine the applicability of air enthalpy for heat stress assessment of outdoor environments in different climates of Iran. The relationships between the enthalpy index and other heat stress indices such as temperature-humidity index (THI), Humidex, and Wet Bulb Globe Temperature (WBGT) were examined. Summertime atmospheric parameters including temperature (°C), relative humidity (%), and atmospheric pressure (hPa) were obtained from the Iranian Meteorological Organization for the months of June, July, and August during a 30-year period from 1987 to 2017. In this study, the De Martonne climate classification system was used, which has identified six different climate classes. Statistical analyzes were performed using the SPSS software v.23 and the Pearson correlation coefficient and linear regression tests. The highest mean air enthalpy and heat stress indices (THI, Humidex, and WBGT) were found in the arid climate during August. The air enthalpy had a direct and strong relationship with air temperature in all climates, and the strongest correlation between was observed in the semi-humid climate (R = 0.899). A direct correlation was found between the air enthalpy index and relative humidity in all climates except the semi-humid climate, and the highest association was observed in the arid climate (R = 0.747). In addition, direct and strong relationships were found between the air enthalpy and the heat stress indices, the highest correlation belonging to the semi-humid climate. With respect to the direct and strong relationships between air enthalpy and the heat stress indices, the simplicity of air enthalpy calculation, and also the possibility of estimating it using meteorological parameters, the enthalpy index can be used as a suitable alternative screening index for heat stress assessment in outdoors, especially in warm and dry regions.

Air free-cooled data centers (DCs) have not existed in the tropical zone due to the unique challenges of year-round high ambient temperature and relative humidity (RH). The increasing availability of servers that can tolerate higher temperatures and RH due to the regulatory bodies’ prompts to raise DC temperature setpoints sheds light upon the feasibility of air free-cooled DCs in the tropics. However, due to the complex psychrometric dynamics, operating the air free-cooled DC in the tropics generally requires adaptive control of supply air condition to maintain the computing performance and reliability of the servers. This article studies the problem of controlling the supply air temperature and RH in a free-cooled tropical DC below certain thresholds. To achieve the goal, we formulate the control problem as Markov decision processes and apply deep reinforcement learning (DRL) to learn the control policy that minimizes the cooling energy while satisfying the requirements on the supply air temperature and RH. We also develop a constrained DRL solution for performance improvements. Extensive evaluation based on real data traces collected from an air free-cooled testbed and comparisons among the unconstrained and constrained DRL approaches as well as two other baseline approaches show the superior performance of our proposed solutions.

Despite the robust mechanical properties of bamboo, interaction with water can result in the instability of these properties. Hygroscopicity is closely related to the chemical content of bamboo. Here, we explored the influence of the chemical composition of bamboo on moisture content from both the equilibrium state and dynamic aspects. We used a simple manufacturing separation process to obtain bamboo fibers (C). A chemical treatment was then used to remove the lignin and hemicellulose, thus altering the chemical content and exposing a greater number of functional groups. We obtained the RL (partial lignin removal) sample via the removal of lignin and the RLH (partial lignin and hemicellulose removal) sample via the removal of lignin and hemicellulose, respectively. The characteristics of the samples were tested using scanning electron microscope, infrared spectrometer and X-ray. And then the hygroscopicity was tested. At 90% relative humidity, the removal of the lignin reduced the weight by 13.30 wt% and increased RL moisture content by 2.99%, while the removal of lignin and hemicellulose reduced the RLH moisture content by 1.94%. At low humidity, RL and RLH have similar hygroscopicity. The RLH sample exhibited the lowest hysteresis out of all the samples. The lignin exhibited an obvious inhibitory effect on the hygroscopicity, while the presence of hemicellulose increased the moisture content of the materials, which is not conducive to their dimensional stability. Moreover, the hygroscopicity of cellulose and hemicellulose is similar. In particular, the chemical-treated samples responded more sensitively and quickly to water through dynamic changes in the weight of the water.

Photooxidation of volatile organic compounds (VOCs) produces secondary organic aerosol (SOA) and light-absorbing brown carbon (BrC) via multiple reaction steps/pathways, reflecting significant chemical complexity relevant to gaseous oxidation and subsequent gas-to-particle conversion. Toluene is an important VOC under urban conditions, but the fundamental chemical mechanism leading to SOA formation remains uncertain. Here, we elucidate multigeneration SOA production from toluene by simultaneously tracking the evolutions of gas-phase oxidation and aerosol formation in a reaction chamber. Large size increase and browning of monodisperse sub-micrometer seed particles occur shortly after initiating oxidation by hydroxyl radical (OH) at 10–90% relative humidity (RH). The evolution in gaseous products and aerosol properties (size/density/optical properties) and chemical speciation of aerosol-phase products indicate that the aerosol growth and browning result from earlier generation products consisting dominantly of dicarbonyl and carboxylic functional groups. While volatile dicarbonyls engage in aqueous reactions to yield nonvolatile oligomers and light-absorbing nitrogen heterocycles/heterochains (in the presence of NH₃) at high RH, organic acids contribute to aerosol carboxylates via ionic dissociation or acid–base reaction in a wide RH range. We conclude that toluene contributes importantly to SOA/BrC formation from dicarbonyls and organic acids because of their prompt and high yields from photooxidation and unique functionalities for participation in aerosol-phase reactions.

Bioaerosols have gained importance in atmospheric sciences in the past few decades. Their exposure upsurges the health problems in sensitive population and is also known to participate in atmospheric chemistry. The present study assesses the monthly distribution of bioaerosol load at four different microenvironments inside an academic institute in Kanpur situated in Indo-Gangetic Plain (IGP). The study duration was from November 2017 to April 2018. The measured total bioaerosol concentrations were highest during April (418–610 CFU/m3) at all sites followed by the post-monsoon month of November (369–577 CFU/m3). The winter period showed low concentrations with lowest concentration obtained in January (251–419 CFU/m3). The indoor–outdoor (I/O) bioaerosol ratio was mostly less than one for bacteria depending on microenvironment, but for fungi it was always less than one. The Gram-positive bacteria (GPB) comprised 70–80% of total bacterial concentration, while Gram-negative bacteria (GNB) contributed 20–30% to bacterial concentration in ambient air. The bacterial genera were mostly dominated by Bacillus, Staphylococcus, Micrococcus, Streptococcus, and Enterococcus, while the fungal genera of Aspergillus, Penicillium, Rhizopus, Cladosporium, Basidiobolus, and Epidermophyton were seen in the campus. The statistical analysis showed a weak positive correlation of bioaerosol concentration with meteorological parameters: temperature and relative humidity (RH).

This study describes the impact of assimilation of INSAT-3D radiances data from both imager and sounder for Indian summer monsoon simulation and rainfall forecast over a hilly terrain using Weather Research Forecast model and its three-dimensional variational data assimilation (3DVAR) technique. The assimilation experiments conducted for the whole month of July 2016 reveal the superior impact of radiance data assimilation (DA) on analysis and forecast of the vertical profile of wind and temperature than the conventional DA experiment. Compared to the rest of the experiments, the imager DA experiment significantly improves the wind forecasts throughout the troposphere and ameliorates the temperature forecasts from 950 to 450 hPa. The sounder DA shows more improvement in the upper-level temperature forecast compared to the imager DA experiment. In addition, the spatial representation of low-level jet, temperature and moisture fields shows more relative improvement in the experiments with radiance DA than conventional DA experiments. While the impact of imager DA is superior for low-level jet forecast, the sounder DA reveals a more accurate tropospheric temperature and relative humidity forecast compared to the rest of the experiment. The rainfall forecast has also improved significantly with radiance DA over the Indian continent, mainly in India's northern, eastern and northeastern regions. Further, India’s northeastern region’s high-resolution rainfall forecast illustrates improvement using INSAT-3D radiance DA from both imager and sounder together compared to only conventional DA.

Acetaldehyde is one of the important VOC species of O3 precursors in the atmospheric environment. The influences of relative humidity (RH) and initial VOC/NOx ratio (RCN) on the formation of O3 are studied in smog chamber experiments, and the MCM v3.3.1 mechanism of acetaldehyde is modified based on the experimental results. In low-RH conditions (RH = 11.6%±1.1%), the O3 concentration at 6 h increases first and then decreases with the increase of RCN, and the RCN at the inflection point of O3 concentrations is 3.2. In high-RH experiments (RH = 78.8%±1.0%), variation of the O3 concentration at 6 h with RCN is similar to that in low-RH experiments, but the RCN at the inflection point is 2.8. RH has no significant effect on the O3 concentrations under low RCN ( 3). Compared with the experimental results, original MCM v3.3.1 greatly underestimates the O3 concentrations. Addition of both the photolysis process of peroxyacetyl nitrate and the photolysis process of HNO3 on the reactor surface into the original MCM can reduce the difference between the simulated O3 concentrations and the experimental results at 6 h from 24%−35% and 17%−49% to 6%−26% and 10%−42% under low- and high-RH conditions, respectively. The maximum incremental reactivity (MIR) of acetaldehyde simulated with the modified MCM is 4.0 ppb ppb−1 without considering the effect of other VOCs.

Black carbon (BC) reduces the photolysis coefficient by absorbing solar radiation, thereby affecting the concentration of ozone (O3) near the ground. The influence of BC on O3 has thus received much attention. In this study, Mie scattering and the tropospheric Ultraviolet and Visible radiation model are used to analyze the effect of BC optical properties on radiation. Combined with data of O3 precursors in Nanjing in 2014, an EKMA curve is drawn, and the variations in O3 concentration are further investigated using a zero-dimensional box mechanism model (NCAR MM). When O3 precursors are unchanged, radiation and O3 show a highly similar tendency in response to changing BC optical properties (R=0.997). With the increase of modal radius, the attenuation of fresh BC to radiation and O3 first trends upward before decreasing. In the mixing process, the attenuation of BC to radiation and O3 presents an upward tendency with the increase of relative humidity but decreases rapidly before increasing slowly with increasing thickness of coating. In addition, mass concentration is another major factor. When the BC to PM2.5 ratio increases to 5% in Nanjing, the radiation decreases by approximately 0.13%–3.71% while O3 decreases by approximately 8.13%–13.11%. The radiative effect of BC not only reduces O3 concentration but also changes the EKMA curve. Compared with the NOx control area, radiation has a significant influence on the VOCs control area. When aerosol optical depth (AOD) increases by 17.15%, the NOx to VOCs ratio decreases by 8.27%, and part of the original NOx control area is transferred to the VOCs control area.

The rapid response to the COVID-19 pandemic led to unprecedented decreases in economic activities, thereby reducing the pollutant emissions. A random forest (RF) model was applied to determine the respective contributions of meteorology and anthropogenic emissions to the changes in air quality. The result suggested that the strict lockdown measures significantly decreased primary components such as Cr (−67 %) and Fe (−61 %) in PM2.5 (p), whereas the higher relative humidity (RH) and NH3 level and the lower air temperature (T) remarkably enhanced the production of secondary aerosol, including SO42- (29 %), NO3- (29 %), and NH4+ (21 %) (p). The positive matrix factorization (PMF) result suggested that the contribution ratios of secondary formation (SF), industrial process (IP), biomass burning (BB), coal combustion (CC), and road dust (RD) changed from 36 %, 27 %, 21 %, 12 %, and 4 % before the COVID-19 outbreak to 44 %, 20 %, 20 %, 9 %, and 7 %, respectively. The rapid increase in the contribution ratio derived from SF to PM2.5 implied that the intermittent haze events during the COVID-19 period were characterized by secondary aerosol pollution, which was mainly contributed by the unfavorable meteorological conditions and high NH3 level.