Changes In Relative Humidity Research Articles

Analysis of Dry-Wet Changes and the Driving Factors in Mainland China under Climate Change

Evaluation of changes in dry-wet climate is crucial in the context of global climate change to ensure regional water resources, ecosystem stability, and socio-economic development. Long-term daily meteorological data, including temperature, precipitation, relative humidity, wind speed, sunshine duration, and air pressure data from 1680 stations across mainland China from 1971 to 2019, were collected to investigate the temporal and spatial variations in aridity index (AI), precipitation (P), reference evapotranspiration (ET0), and the underlying driving climatic factors. Results indicated that the Northwest, Northeast, and Huang-Huai regions were undergoing significant wetting processes, while the Southwest and Southeast China were undergoing significant drying processes. The changing AI was mainly decided by the changing trends of ET0. For most regions, ET0 has undergone significant increases. The average increasing rate over mainland China was 3.76 mm/10a. Stations with decreasing trends were mainly located in the Tibet Plateau, Huang-Huai, and northern Northeast China. Trends in ET0 were negatively affected by the increasing changes in relative humidity and positively affected by the decreasing changes in wind speed and sunshine duration and the increasing changes in air temperature. Wind speed and relative humidity were found to be the main dominant factors driving the changes in ET0, and their contribution varied with regions. Huang-Huai and northern Northeast China showed a significant downward trend in ET0, mainly driven by the decrease in wind speed, while the increase in relative humidity was the primary contributor to the significant upward trends in ET0 across all other regions in China.

A drier than expected future, supported by near-surface relative humidity observations.

Despite continuous progress in climate modeling, global projections of the terrestrial water cycle remain highly model dependent. Here, we use quality-controlled gridded observations of temperature and humidity to constrain projected changes in continental near-surface relative humidity across the 21st century. Results show that the projections are poorly constrained when using surface temperature observations only and argue for mitigation policies that are not only rooted in global warming levels. Projections constrained with both near-surface temperature and relative humidity observations show an inevitable continental drying, especially in the northern midlatitudes where anthropogenic aerosols have, however, countered this long-term response until the late 1980s. A "strong drying" storyline is then used to highlight the urgent need for careful adaptation strategies and to suggest a possible contribution of land surface processes to model uncertainties.

A multi-region study of carbonate clumped isotope data from terrestrial snails

The stable oxygen isotope composition (δ18O) of land snail shells has been used for decades to provide insight into past changes in δ18Oprecipitation, relative humidity, moisture source and several other paleoenvironmental parameters across diverse environments and ecosystems. Recently, carbonate clumped isotope values (Δ47) recorded from land snail shells have also been applied as a geothermometer. However, there is limited information available regarding the relationship between modern shell geochemistry and paleoenvironmental conditions for regions with contrasting climates, which is needed for further contextualization and validation of snail shell temperature proxies. Our study utilizes paired Δ47 and δ18Oshell measurements in terrestrial snail shells to reconstruct temperature (T47) and δ18Obody water composition, which are two key variables used for the study of regional and sub-regional paleoclimates and paleoecosystems. We examine shells from three geographical regions with distinct hydroclimates: Central Europe, the Canary Islands, and the Chinese Loess Plateau. To constrain the timing of shell growth, we compare snail shell isotope-derived climate parameters to independent environmental data, including mean annual, warm season, and rainy season temperatures, assuming snail shells mineralize during the optimal activity range of 15–25 °C. Our results indicate that values for samples from the Canary Islands are most consistent with year-round growth; Chinese Loess Plateau samples are most consistent with summer growth; and samples from Central Europe are most consistent with growth between spring and autumn. Calculated values of δ18O body water in snail shells were found to be enriched relative to the value of δ18Oprecipitation for the season of growth, with values ranging from ∼1–5‰. Altogether, our data suggest that Δ47 and δ18O measurements from terrestrial snail shells represent a useful archive of environmental temperature and humidity. However, their application in the paleo-record requires careful consideration of the ecophysiology of the taxa, and the climate of the region.

Novel polyvinyl alcohol film dosimeter containing 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide dye for high dose application

A new dyed polyvinyl alcohol (PVA) film dosimeter based on 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MMT) tetrazolium dye is proposed in this study for measuring high gamma radiation dose. Gamma cell irradiator that contains Co-60 gamma-ray source was used to expose the novel MMT-PVA films to different doses up to 25 kGy. The changed in optical property of irradiated and unirradiated films were characterized by UV–Vis spectrophotometer. The results show that the dose sensitive and the linear range of irradiated films were increased considerably with increase of MMT concentration from 1 to 5 mM. The dose response of dyed PVA film changed substantially with changing relative humidity (12–74%) as well as irradiation temperature (10–40 °C). The absorbance of the un-irradiated films does not change up to 10 days in dark while a significant increase in their absorbance was reported for similar films under fluorescent light. The irradiated dosimeters that kept in dark showed a perfect stability for 54 days. It was found that no obvious impact of dose rate on the irradiated MMT-PVA film dosimeters.

Importance of nasal air conditioning in pre-septoplasty planning: A heat and mass transfer perspective

Nasal air conditioning (heat and mass transfer) is one of the essential functions of the nasal cavity, which can get significantly altered due to deviated nasal septum (DNS). Its importance in pre-septoplasty planning remains poorly investigated, with existing literature focusing primarily on the importance of airflow and pressure drop in determining the efficacy of septoplasty. Nevertheless, this parameter should be considered as ignorance can lead to an erroneous selection of septoplasty patients. In this regard, the current study uses virtual septoplasty and image-based CFD modeling based on the finite volume method (FVM) to investigate the alteration in nasal air conditioning in seventeen DNS patients. Changes in relative humidity (RH) at the nasopharynx region are highlighted. In addition, a new parameter known as the septoplasty score is introduced, which considers the combined effect of pressure drop and RH to quantify the effectiveness of the septoplasty. The insilico results show that DNS leads to asymmetric distribution of water mass fraction and temperature, with higher values on the narrower side of the nasal cavity leading to local drying of the mucosal layer. This asymmetric effect becomes less potent after virtual correction with a maximum decrease in the mass transfer of up to 85 gm per week. Further, the inspired air's RH is significantly altered at the nasopharynx region before and after the virtual septoplasty with a maximum difference of up to 10%. The septoplasty score always increases after correction with a maximum increase of up to 90%; thereby, it can be used by ENT surgeons to quantify septoplasty's benefits.

Decomposition of meteorological and anthropogenic contributions to near-surface ozone trends in Northeast China (2013–2021)

Recent years have seen an increase in regional ozone (O3) pollution in China. This study explored the interannual variability in daily maximum 8-h average O3 concentration (MDA8-O3) in Northeast China (NEC) and its three subregions (Liaoning, Jilin, and Heilongjiang) during 2013–2021, and identified the key meteorological drivers underlying the observed variability. The Kolmogorov–Zurbenko filtering technique was applied to a stepwise multiple linear regression model to decompose the meteorological and anthropogenic contributions to annual MDA8-O3 trends. The results showed that the spatiotemporal variation of MDA8-O3 in NEC is characterized by a high–south and low–north pattern with an MDA8-O3 hotspot in the Bohai Rim area. Over the 9-year study period, a significant increasing trend (∼2.5% a−1, P < 0.05) in the regional mean of the annual 90th percentile of MDA8-O3 was detected across NEC. This trend was strongly relevant to changes in relative humidity and surface solar radiation downward (SSRD). Statistical analyses revealed that SSRD dominated MDA8-O3 variability spatially over almost the entire NEC region. Additionally, the contribution decomposition suggested that the trend of increase in annual average MDA8-O3 in NEC was dominated by anthropogenic emission change, which explained 91.9% of the total variation. Regionally, although the dominant role of emissions has not changed, the meteorology-driven anomalies also explained −4.3%–3.3% of the annual average MDA8-O3 variation. This study provides insight into decoupling the complex relationships between long-term variability in regional O3 pollution and both anthropogenic emissions and meteorology, which could provide valuable information for future efforts to address the O3 pollution in NEC.

Dried bonito flakes-inspired moisture-responsive actuator with a gradient structure for smart devices

Exploring high-performance soft actuators from biomass resources is significant for developing eco-friendly smart devices. Dried bonito (DB) flake is a common food as well as a biomass material, and it can produce irregular motion in changed moisture, just like dancing. Inspired by this intriguing phenomenon, a cost-effective, biocompatible, and biodegradable moisture-responsive DB film actuator with a gradient structure is developed. The DB film actuator exhibits rapid and reversible bending deformation triggered by a humidity gradient with a high bending speed (40° s–1) and a maximum bending angle (180°). Moreover, the DB film actuator shows large bending deformation (–71° to +51°) with a high actuation force (214.7 Pa) in response to changes in relative humidity. Furthermore, the actuation performance can be also tuned by adjusting the thickness of the film. Potential applications of this actuator, including smart grippers, crawling robots, and biomimetic flowers for visible humidity sensing, are demonstrated. More importantly, smart sweat-responsive wearables that automatically deform to promote sweat evaporation and convection during exercise are constructed based on the actuator, making it promising for adaptive personal thermal management. This work offers an easily processable, cost-effective, and environmentally benign strategy to construct moisture-responsive actuators for future eco-friendly smart devices.

Thermal conductivity temperature dependence of heat-treated wood at different moisture content levels

Effects of temperature dependence and relative humidity were studied relative to the thermal conductivity of heat-treated pine and heat-treated beech, which are frequently used for building construction. Pine and beech wood were exposed to heat treatment at 180, 200, and 220 °C in nitrogen gas for 2 h. As a result, the thermal conductivity values of the heat-treated wood decreased as the temperature of the heat treatment process increased and relative humidity increased. However, thermal conductivity of wood became more stable after heat treatment under relative humidity changes. The thermal conductivity values increased with rising mean plate temperatures, while the temperature dependence of the heat-treated wood was not affected by the relative humidity changes. Consequently, heat-treated wood, with variable humidity without excessive heat changes, can be preferred for the construction of buildings.

Influence of relative humidity on the structure, swelling and electrical conductivity of PEDOT:PSS fibers

PEDOT:PSS is a conducting polymer with a wide variety of applications in the field of organic electronics. Over the past few years our group has developed PEDOT:PSS fibers with high electrical conductivity and robust mechanical properties, and we have observed changes in their properties that seemed to stem from seasonal changes in atmospheric relative humidity. In this work, we report the influence of relative humidity on the swelling, electrical conductivity and structure of wet-spun PEDOT:PSS fibers. The diameter of the fibers linearly increased with relative humidity up to the 70–80% range where the increase became exponential. The electrical conductivity reversibly decreased with increasing relative humidity with a similar linear and then exponential behavior. Additionally, an irreversible decrease (aging) in electrical conductivity was also observed. To gain more insight into the structural origin of these changes, wide angle x-ray scattering of the PEDOT:PSS fibers were gathered at different relative humidities in the 10–90% range so that the changes in structure could be observed in situ. On one hand, the lamella stacking distance of PEDOT and PSS chains increased linearly up to the 70–80% relative humidity range where the increase became exponential. On the other hand, the π-π stacking distance between PEDOT chains remained unaltered. We found that the changes in the lamella stacking distance were closely correlated to the changes observed for the diameter and electrical conductivity.

A method to quantify and account for the hygroscopic effect in stem diameter variations

Dendrometers recording stem diameter variations (SDV) at high-resolution are useful to assess trees' water relation since water reserves are stored in the elastic tissue of the bark. These tissues typically shrink during the day as they release water when evaporative demand is high and swell during the night as they are replenished when evaporative demand is low, generating the typical SDV profile known as the diel SDV cycle. However, similar SDV cycles have been observed on dead trees due to the hygroscopic shrinking and swelling of the dead bark tissues. In order to remove this hygroscopic effect of the bark, dendrometers are applied as close as possible to the living bark tissues by removing the outer dead layer, however with questionable success. In this study, we used SDV time series from 40 point dendrometers applied on dead-bark-removed mature trees to assess and quantify the remaining hygroscopic effect on individual trees. To do so, we checked SDV behavior in the cold season and explored the relation between the diel SDV cycle and changes in relative humidity (RH). Our results showed that (a) the hygroscopic effect in SDV can be well-detected based on the amplitude of the diel SDV cycle (diel SDVampl) and the correlation between SDV and RH during both the cold and the warm season; (b) the level of the hygroscopic effect varies strongly among individuals; (c) diel SDVampl is proportional to both changes in RH and transpiration so that the hygroscopic effect on the diel SDV cycle can be quantified using a linear model where (diel SDVampl) is a function of RH changes and transpiration. These results allow the use of the model to correct the amplitude of the diel SDV cycles and suggest that this method can be applied to other ecological relevant water-related SDV variables such as tree water deficit.

Humidity sensor element based on porous silicon – reduced graphene oxide sandwich-like structures

In this study, the field-effect transistor (FET) based on porous silicon (PS) – reduced graphene oxide (rGO) sandwich-like structure is suggested as a sensitive element of the humidity sensor. It is shown that the position of the charge neutrality point (Dirac point) and the ratio between the hole and electron branches of the resistance profile of the PS–rGO-based FET depend significantly on the relative humidity. An increase in air humidity causes a decrease in the electrical resistance and an increase in the capacity of the obtained FET. The sensing ability and dynamic characteristics were analyzed to estimate the sensory properties of the PS–rGO sandwich-like structure. A higher sensitivity of the resistive sensor element than the capacitive has been found. The response time of the obtained sensors to changing relative humidity is about 1 min at room temperature. As a result, the PS–rGO-based FET demonstrates high potential applications in humidity-sensitive devices.

Dynamics of pollen-generating environment producing impact on society based on the relative humidity of the previous year and flowering synchrony

An area with the potential of producing high concentrations of airborne pollen is defined as the ‘potential pollinosis area’. However, the detailed dynamics of pollen dispersion are not fully understood. Further, studies on the detailed dynamics of the pollen-generating environment are limited. This study aimed to determine the relationship between the dynamics of potential pollinosis areas and annual meteorological factors with high spatiotemporal resolution. We visualised and analysed the dynamics of the potential polliosis area based on 11–year high-spatial-density observation data for the atmospheric concentrations of Cryptomeria japonica pollen. The results showed that the potential pollinosis area headed northeast with repeated expansion and contraction, while the centre of the potential pollinosis area leaped to the north in mid-March. The variance in the fluctuation of the coordinates for the potential pollinosis area before the northward leap was strongly related to the variance in the relative humidity of the previous year. These results indicated that the pollen grains of C. japonica across Japan are distributed based on the meteorological conditions of the previous year until mid-March, after which, the pollen grains are distributed through flowering synchrony. Our results suggest that daily nationwide flowering synchrony has a significant annual impact, and changes in relative humidity caused by, for example, global warming would affect the occurrence and predictability of seasonal changes in the pollen dispersion dynamics of C. japonica and other pollen-producing species. Our study showed that pollen production by C. japonica through flowering synchrony is a major cause of nationwide pollinosis and other allergy-related health problems.

Challenges and solutions of environmental scanning electron microscopy characterisation of biomaterials: Application to hygro‐expansion of paper

AbstractMost methodologies to measure the moisture‐induced deformation (hygro‐expansion) of paper microconstituents, including fibres and interfibre bonds, are low resolution or time‐consuming. Hence, here, a novel method is proposed and validated to measure high‐resolution full‐field strain maps of paper microconstituents during hygro‐expansion, based on environmental scanning electron microscopy (ESEM). To this end, a novel climate stage enables accurate control of the relative humidity (RH) near the specimen in the ESEM from 0%–100%. The fibre surface, which is decorateda prioriwith a microparticle pattern, is captured during RH change. Subsequently, correlating the fibre surface using a dedicated global digital image correlation algorithm enables high‐resolution hygro‐expansion strain maps. Method optimisation involved performing contrast enhancement, scan‐correction to reduce ESEM artefacts and a background correction, resulting in a strain resolution of . Method validation revealed that the fibres' crystallinity is affected by the electron beam, even for minimal invasive electron beam settings. Interestingly, however, the fibres consistently exhibit conventional hygro‐expansion behaviour during the drying slopes. Using the optimised procedure, hygro‐expansion characterisation of two interfibre bonds and four interfibre bond cross‐sections revealed the competition between the low longitudinal and large transverse fibre hygro‐expansion in the bonded area.

Experimental drier climates affect hydraulics and induce high mortality of seedlings of three northern conifer species

The future climate of northern temperate forests is projected to be drier and warmer by the end of this century. As a result, more drought-induced forest dieback events are anticipated in northeastern North America, and assessing the vulnerability of dominant tree species to drought is critical for understanding the future composition of these forests. In a greenhouse experiment, we exposed two-year-old seedlings of Picea glauca (Moench) Voss, Picea mariana (Mill.) B.S.P. and Pinus strobus L. to three future climate treatments for southern Quebec, Canada, and evaluated their mortality, growth, and foliage water status responses to soil water availability and atmospheric drought. Using a unique approach, climate treatments emulated droughts of different frequencies, durations, and intensities. Treatments closely simulated one growing season, with changes in air temperature and relative humidity every six hours and daily adjustment in the amount of water delivered to the seedlings. The three species experienced high mortality (75%) in all water-limited treatments compared to a control treatment that provided non-limiting soil moisture (0% mortality). The biomass of the seedlings that survived was 40% lower than that of control seedlings. Our results confirmed that the hydraulic safety margins, defined as the difference between seasonal minimum water potential and xylem water potential leading to 12, 50 and 88% of hydraulic conductivity loss, were good predictors of probability of tree mortality. Therefore, hydraulic safety margins are useful functional traits that can be used to compare the vulnerability of various species to drought and then provide crucial information to practitioners and policymakers to adjust forest management to climate change. We showed that three dominant conifer species of northern temperate forests were highly vulnerable to drought in future climates. Because drought is projected to be a significant threat to forests, understanding potentially adaptive physiological responses to drought, such as hydraulic safety margins of tree seedlings, is important for predicting the response of forest regeneration and composition in warmer and drier climates.

Different uncertainty in tropical oceanic and land precipitation sensitivities under global warming

The change in precipitation (P) under global warming has far-reaching implications for society. However, the high degree of intermodel uncertainty in future projections undermines the reliability of the multi-model mean. The present study investigates the sources of intermodel uncertainty in tropical-mean oceanic and land P sensitivities under global warming, based on an analysis of 28 models from CMIP6. Results show that the uncertainty in tropical-mean P sensitivity is greater over ocean compared to that over land, and both are closely tied to uncertainties in tropical-mean circulation sensitivity. Nevertheless, the underlying drivers of the uncertainty in tropical-mean circulation sensitivity vary between ocean and land. For the tropical-mean oceanic part, the tropical sea surface temperature (SST) warming pattern, particularly the SST warming over the western equatorial Pacific, plays a crucial role by modifying the atmospheric stability over the tropical Pacific. On the other hand, for the tropical-mean land part, the combined impacts of changes in land sea level pressure, relative humidity and SST warming over the equatorial Pacific contribute to the intermodel uncertainty in circulation sensitivity. The results highlight the importance of improving the simulation of these factors to reduce the discrepancies in tropical-mean oceanic and land circulation sensitivities among climate models, ultimately leading to a more accurate depiction of P sensitivities under global warming.

Experimental investigation and dynamic modelling of an upright freezer under periodic door opening conditions

This paper performs a comprehensive experimental and modelling study to examine the dynamic behaviour of an upright freezer with adjustable shelving under periodic door opening conditions with different temperature, pressure and relative humidity values. An uncertainty analysis is carried out for the experimentally measured data. Additionally, the dynamic model is developed with crucial sub-components, such as discretized upright cabinet, frosted evaporator and semi-empirical door opening mechanism using an object-orientated programming language called Modelica. The present model is the validated with experimental data employing the values of the airflow from ambient into the cabinet along with the average cabinet air flowrate and back wall temperatures, transient evaporation and condensation pressures, cabinet average relative humidity change, compressor operation time and power consumption, and finally total energy consumption of refrigerator for both 85%RH and 65% RH conditions at 32 °C ambient. The results show that the model predictions have a similar trendline with the experimental findings within ±3 K error bands regarding average cabinet air and back wall temperature. In contrast, the dynamic cyclic trend before and after door opening is closer to the experiments within ±1 K. The current model predictions for the low and high pressures are found to be within ±3% and ±5% error bands, respectively, whereas the average relative humidity level of the cabinet is captured within ±10% deviation. Furthermore, transient compressor power is well predicted with deviations, but not exceeding 4.5%, and the total energy consumption level is compatible with 6% error bands during the entire experimental period.

EFFECT OF MICROSTRUCTURE AND RELATIVE HUMIDITY ON ATMOSPHERIC PITTING CORROSION OF DUPLEX STAINLESS STEEL BENEATH MGCL2 DROPS

One of the main issues for intermediate-level nuclear waste (ILW) is atmospheric corrosion in stainless steel. The impact of microstructure on the pit shapes on three orientations of the duplex stainless steel DSS 2205 plate and the relative humidity impact on the atmospheric corrosion pits of DSS beneath MgCl2 drops is determined through the use of four characterization tools: X-ray diffraction (XRD), Energy dispersive X-ray (EDX) analyses, Scanning electron microscopy (SEM), and optical microscopy. The pits on the top surface (LT) appears layered like an attack and mostly hemispherical, while the long transverse (LS) and short transverse (ST) planes reveal elongated strings. The map scan of EDX indicates mixed oxide inclusions and MnS inclusion existing in the steel alloy and the XRD analyses present the existence of two-phase both austenite γ and ferrite α peaks. The pit shape and area were influenced by relative humidity (RH) change. At RH 35% the trend of pits in 1-week exposure revealed a larger area of pit mouth than in RH 45%. For the same exposure time and in both RHs, the area seemed to be greater at the droplet’s center than in the edge of the droplet.

Mechanism changing iron solubility and oxidative potential associated with PM2.5 during outdoor-to-indoor transport

Water-soluble transition metals are more bio-accessible than insoluble particulate matter (e.g., PM2.5) components and can contribute to PM2.5 oxidative potential, a metric that has been linked to air pollution health impacts. Fifteen pairs of indoor-outdoor PM2.5 samples were collected outdoors and in unoccupied rooms to examine change of iron solubility and dithiothreitol-based oxidative potential of PM2.5 during outdoor-to-indoor transport. Changes of relative humidity (ΔRH = RHin/RHout - 1) and aerosol acidity (ΔpH = pHin/pHout - 1) together were found to modify iron solubility (ΔS = Sin - Sout) during outdoor-to-indoor transport. Multiple linear regression was performed to examine relationship between ΔRH, ΔpH and ΔS, resulting in a statistically significant correlation (correlation coefficient of 0.68 and P value < 0.05). This correlation coefficient is higher than that for ΔRH or ΔpH alone (0.40 between ΔRH and ΔS and −0.32 between ΔpH and ΔS). This supports that during outdoor-to-indoor transport, increases in RH lead to increases in water content in PM2.5, increasing the amount of iron in the aqueous phase, and decreases in pH would lead to stronger metal mobilization capacity. These two factors together explain the change of iron solubility during the transport process. A correlation coefficient of 0.67 was also found between ΔRH and ΔpH and changes in intrinsic oxidative potential (OPM) of PM2.5, further corroborating the combined role of relative humidity and aerosol acidity in driving change of iron solubility and OPM of PM2.5 during outdoor-to-indoor transport.

Mechanism analysis of the summer dry-wet interdecadal transition in the Tarim Basin, Northwest China

Using the ERA-5 monthly reanalysis data and precipitation observations, this paper analyses the interdacal dry-wet transition and its mechanism in the Tarim Basin(TB) during summer. From the long-term perspective(1961–2021), TB is in a trend of “wet in the west and dry in the east”. By taking a nine-year moving average of the precipitation(PRE), the research period is divided into three subperiods: P1(1961–1987), P2(1988–2009) and P3(2010−2021). From P1 to P3, the regional averaged Standardized Precipitation Evapotranspiration Index(SPEI) demonstrates an interdecadal turning of “wetting to drying”. During P2(1988–2009), the dynamic component of water vapor increases the zonal moisture transport, causing a slight increase in PRE. The potential evapotranspiration(PET) is weakened by the increase in PRE and relative humidity(RH), the decrease in 2-m temperature(T2m) and 10-m wind speed(10UV), resulting in the humidification of the TB. In the P3(2010–2021), the non-linear component of water vapor increases moisture convergence in the western TB, causing a significant increase in PRE. However, the decrease in RH, accompanied by increases in T2m and UV10, results in a rapid increase in PET. The TB gets dry. The South Asian high(SAH) develops southeastward, guiding more water vapor transport from the upstream westerly and the tropical Indian Ocean. The Western Pacific subtropical high(WPSH) extends northwestward, increasing water vapor convergence in the western TB. The main reason for the increased precipitation changes from increased water vapor advection to enhanced water vapor convergence. The differences in PRE formation and T2m amplitude cause the interdecadal change in RH, deriving an interdecadal transition of wet and dry in the TB. Our findings may deepen the understanding of climate change, and provide a scientific support for ecological development, and global climate governance in arid/semi-arid regions.

Recommendation of RILEM TC 271-ASC: New accelerated test procedure for the assessment of resistance of natural stone and fired-clay brick units against salt crystallization

This recommendation is devoted to testing the resistance of natural stone and fired-clay brick units against salt crystallization. The procedure was developed by the RILEM TC 271-ASC to evaluate the durability of porous building materials against salt crystallization through a laboratory method that allows for accelerated testing without compromising the reliability of the results. The new procedure is designed to replicate salt damage caused by crystallization near the surface of materials as a result of capillary transport and evaporation. A new approach is proposed that considers the presence of two stages in the salt crystallization test. In the first, the accumulation stage, salts gradually accumulate on or near the surface of the material due to evaporation. In the second, the propagation stage, damage initiates and develops due to changes in moisture content and relative humidity that trigger salt dissolution and crystallization cycles. To achieve this, two types of salt were tested, namely sodium chloride and sodium sulphate, with each salt tested separately. A methodology for assessing the salt-induced damage is proposed, which includes visual and photographical observations and measurement of material loss. The procedure has been preliminarily validated in round robin tests.