Explore the vast range of titles available.

PurposeWater vapor trapped in the boundary layer between a person and the clothing creates discomfort and other unpleasant sensations. When that water vapor is prevented from leaving the clothing by external vapor barriers or impermeable layers, those psychophysical states are further exacerbated. One situation where that can be problematic is in office workplaces, and the seats that workers use for many hours every day. This study aims to evaluate the impact of different fabrics that are used for seat cover on water vapor retention.Design/methodology/approachThe authors' method determines the behavior of contact surface humidity with a 50 kg sandbag on the seat to mimic the deformation of the seat materials due to the seated person's weight. Thus, the maximum increase in relative humidity (RH) after humidification of the seat surface (ΔRH-max), the time required to reach the maximum value of humidity (t-max) and the time constant (TC) after humidity starts to fall were derived.FindingsOf the three different seat covers tested, the ΔRH-max of the wool were 7.3–8.8%, compared to 27.0–29.0% of the polyvinyl chloride (PVC), indicating more moisture absorption and transmission of the wool. The TC of the acrylic cover was 224–384 min compared to the 483–558 min of the PVC, which indicated a quick drying out feature of the acrylic.Originality/valueThe ΔRH-max, t-max and TC were all significantly correlated with the RH at the back thigh skin surface of the actual human participants.

Using monthly meteorological observation data at 633 sites in China during 1961–2012, the drought severity change has been investigated in terms of the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) with potential evapotranspiration estimated by the Penman–Monteith equation (SPEI_pm). Significant wetting appeared to have occurred in northwestern corner of China (Xinjiang Province), especially in winter. The middle to northeastern Tibetan Plateau also experienced wetting in the last 52 years in general. Significantly, drying occurred in Central China (mostly in the middle Yellow River basin) and southwestern China (Yunnan–Guizhou Plateau) in spring and in autumn. There is no evidence of an increase in drought severity over China taking the whole country into account. On the contrary, the hyper-arid and arid zones got significantly wetter in the last 52 years as indicated by both SPI and SPEI.

Near-surface humidity (Qa) is a key parameter that modulates oceanic evaporation and influences the global water cycle. Remote sensing observations act as feasible sources for long-term and large-scale Qa monitoring. However, existing satellite Qa retrieval models are subject to apparent uncertainties due to model errors and insufficient training data. Based on in situ observations collected over the China Seas over the last two decades, a deep learning approach named Ensemble Mean of Target deep neural networks (EMTnet) is proposed to improve the satellite Qa retrieval over the China Seas for the first time. The EMTnet model outperforms five representative existing models by nearly eliminating the mean bias and significantly reducing the root-mean-square error in satellite Qa retrieval. According to its target deep neural network selection process, the EMTnet model can obtain more objective learning results when the observational data are divergent. The EMTnet model was subsequently applied to produce 30-year monthly gridded Qa data over the China Seas. It indicates that the climbing rate of Qa over the China Seas under the background of global warming is probably underestimated by current products.

Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotope observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ18Ov ranged from −40.2 to −15.9 ‰ and δ2Hv ranged from −278.7 to −113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dv) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in dv, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( >  25 mmol mol−1) indicate that regional evaporation can account for 40 to 60 % of the PBL water vapor. These estimates are in relatively good agreement with that derived from numerical weather model simulations. This relatively large fraction of evaporation-derived water vapor implies that evaporation has an important impact on the precipitation recycling ratio within the region. Based on multiple constraints, we estimate that the summer season recycling fraction is about 30 %, indicating a potentially important link with convective precipitation.

We investigate whether the observed surface specific humidity (q) trends over the Mediterranean region in the period 1974–2003 are consistent with climate model (CMIP3, CMIP5) simulations of q in response to anthropogenic forcing (Greenhouse gas and sulphate aerosols). The natural (internal) variability is estimated using 6,000‐year of pre‐industrial control simulations. With the exception of winter, the increases in annual and seasonal q over this region are very unlikely (with less than 1%chance) due to natural (internal) variability or natural forcing alone. Using several climate models and ensemble means, we demonstrate that the large‐scale component (spatial‐mean trend) of the anthropogenic forcing is detectable (at 1% level) in the annual and seasonal trends of q (except winter). However, the smaller‐scale component (spatial anomalies about the mean trend) of the anthropogenic signal is detectable only in warm seasons (spring and summer). We further show that the spread of projected trends based on the A1B scenario derived from 13 CMIP3 models encompasses the observed area‐averaged trend in q. This may imply that the observed trends of surface humidity, which is an important factor in human thermal comfort, serves as an illustration of plausible future expected change in the region. Key Points Externally forced changes are detectable in the observed humidity trends Anthropogenic forcing has a detectable influence in the observations Observed changes can be used as an illustration of plausible future change

Chemical and antioxidant responses of the water-deficit tolerant Chinese liverwort, Plagiochasma appendiculatum, to water-deficit stress were investigated in this study. The results showed that water-deficit stress could increase the accumulation of the main bisbibenzyl, riccardin D (RD), and the level of the expression of genes related to production of RD. Activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), soluble protein and malondialdehyde (MDA) content could be used as indicators of the degree of damage to plants under different water-deficit stresses. Among these indicators, SOD played a significant role in defense against water stress when humidity is higher than 40 ± 5% RH (relative humidity), while the activities of POD and CAT were inhibited. However, when humidity is lower than 40 ± 5% RH, POD and CAT activities were accelerated, and if water-deficit reached serious levels (≤ 20 ± 5% RH), POD activity was inhibited, while CAT activity was long-lasting and enhanced; soluble protein and MDA content exhibited the opposite trend. Below 70 ± 5% RH, MDA contents were the highest among all treatments, suggesting that over-wetting is a significant stress for this liverwort. Content of MDA is higher after one week rather than two weeks, suggesting that the liverwort has the ability to eliminate MDA produced by membrane lipid peroxidation. The results of this study provide optimized soil humidities to improve the production of riccardin D in a cultivated liverwort.

Combined measurements of δ18O, δ17O, and δD in ice cores, leading to d excess and 17O excess, are expected to provide new constraints on the water cycle and past climates. We explore different processes, both in the source regions and during the poleward transport, that could explain the 17O excess increase by 20 per meg observed from the Last Glacial Maximum (LGM) to Early Holocene (EH) at the Vostok station. Using a single‐column model over tropical and subtropical oceans, we show that the relative humidity at the surface is the main factor controlling 17O excess in source regions. Then, using a Rayleigh‐type model, we show that the 17O excess signal from the source region is preserved in the polar snowfall, contrary to d excess. Evaporative recharge over mid and high latitudes and δ18O seasonality in polar regions can also affect the Vostok 17O excess but cannot account for most of the 20 per meg deglacial increase from LGM to EH. On the other hand, a decrease of the relative humidity at the surface (rhs) by 8 to 22% would explain the observed change in 17O excess. Such a change would not necessarily be incompatible with a nearly unchanged boundary layer relative humidity, if the surface thermodynamic disequilibrium decreased by 4°C. Such a change in rhs would affect source and polar temperatures reconstructions from δ18O and d excess measurements, strengthening the interest of 17O excess measurements to better constrain such changes.

We have developed a new algorithm to estimate the surface air specific humidity over the ocean from AMSR-E data. It should be noted that remarkably reduced random errors of the estimated surface air specific humidity result from using the surface air specific humidity provided by reanalysis data. We validated our new algorithm using independent ship and buoy data. The bias, RMS error, and correlation coefficient of the products obtained using our algorithm for global buoys are 0.38 g/kg, 0.61 g/kg and 0.99, respectively. It should be noted that surface specific humidity having similar accuracy to the reanalysis data near in situ data could be derived from AMSR-E data by the present algorithm.

The accuracy of a complementary relationship (CR) evapotranspiration (ET) model depends on how to parameterize the relationship between apparent potential ET and actual ET as the land surface changes from wet to dry. Yet, the validity of its inherent symmetric assumption of the original CR framework, i.e., the B value equal to one, is controversial. In this study, we conduct a comparative study between a linear, symmetric version (B = 1) and a nonlinear, asymmetric version (B is not necessarily equal to 1) of the advection-aridity (AA) CR model in a large ephemeral lake, which experiences dramatic changes in surface/atmosphere humidity. The results show that B was typically 1.1 ± 1.4 when ET ≤ ETPT ≤ ETPM, where ETPM and ETPT are estimated using the Penman (PM) and Priestley–Taylor (PT) equations, respectively; the AA model performed reasonably well in this case. However, the value of B can be negative and deviate from 1 significantly if the inequality ET ≤ ETPT ≤ ETPM is violated, which is quite common in humid environments. Because the actual ET can be negatively (B > 0) or positively (B < 0) related to the evaporative demand of the air, the nonlinear AA model generally performs better than the AA model if ET ≤ ETPM is satisfied. Although B is not significantly correlated with the atmospheric relative humidity (RH), both models, especially the nonlinear AA model, resulted in negative biases when ET > ETPM, which generally occur at high RH conditions. Both the linear and the nonlinear AA models performed better under higher water level conditions, however, our study highlights the need for higher-order (≥3) polynomial functions when CR models are applied in humid environments.

A review of literature data on the degree of peat decomposition – an important parameter that yields data on environmental conditions during the peat-forming process, i.e., humidity of the mire surface, is presented. A decrease in the rate of peat decomposition indicates a rise of the ground water table. In the case of bogs, which receive exclusively atmospheric (meteoric) water, data on changes in the wetness of past mire surfaces could even be treated as data on past climates. Different factors shaping the process of peat decomposition are also discussed, such as humidity of the substratum and climatic conditions, as well as the chemical composition of peat-forming plants. Methods for the determination of the degree of peat decomposition are also outlined, maintaining the division into field and laboratory analyses. Among the latter are methods based on physical and chemical features of peat and microscopic methods. Comparisons of results obtained by different methods can occasionally be difficult, which may be ascribed to different experience of researchers or the chemically undefined nature of many analyses of humification.