Wet Bulb Research Articles

Comparing Approximated Heat Stress Measures Across the United States.

Climate change is escalating the threat of heat stress to global public health, with the majority of humans today facing increasingly severe and prolonged heat waves. Accurate weather data reflecting the complexity of measuring heat stress is crucial for reducing the impact of extreme heat on health worldwide. Previous studies have employed Heat Index (HI) and Wet Bulb Globe Temperature (WBGT) metrics to understand extreme heat exposure, forming the basis for heat stress guidelines. However, systematic comparisons of meteorological and climate data sets used for these metrics and the related parameters, like air temperature, humidity, wind speed, and solar radiation crucial for human thermoregulation, are lacking. We compared three heat measures (HImax, WBGTBernard, and WBGTLiljegren) approximated from gridded weather data sets (ERA5-Land, PRISM, Daymet) with ground-based data, revealing strong agreement from HI and WBGTBernard (R 2 0.76-0.95, RMSE 1.69-6.64°C). Discrepancies varied by Köppen-Geiger climates (e.g., Adjusted R 2 HImax 0.88-0.95, WBGTBernard 0.79-0.97, and WBGTLiljegren 0.80-0.96), and metrological input variables (Adjusted R 2 T max 0.86-0.94, T min 0.91-0.94, Wind 0.33, Solarmax 0.38, Solaravg 0.38, relative humidity 0.51-0.74). Gridded data sets can offer reliable heat exposure assessment, but further research and local networks are vital to reduce measurement errors to fully enhance our understanding of how heat stress measures link to health outcomes.

Changes in Intergranular Air Properties and Chemical Parameters of Short-term Stored Bulk Shelled Corn with Slightly High Moisture Content

Objective: This study is to determine the main parameters influencing the storage of shelled corn with slightly high moisture content (MC) so that its quality can be maintained. Methods: The intergranular air properties and chemical changes was determined in 4,169 tonnes of shelled corn bulk with an average MC of 15.3% and a height of 5m, which was stored for 90 days in a large warehouse in Shandong Province, China, from winter to early spring. The intergranular air property parameters were calculated with self-compiled software. Results: Fans were used to achieve temperature-equalizing aeration at a low rate (5.87m3/h/t) after warehousing, which decreased the bulk temperature from 6.8 to 4.7℃. Afterwards, with the increase in ambient temperature, the surface-layer grain temperature increased drastically, while that of the bottom layer increased slowly and those of the middle layers increased even more slowly. The minimum and mean cumulative dry-bulb, wet-bulb and dew-point temperatures (DPT) increased in the order of middle layer˂ bottom layer˂ surface layer. Free fatty acid content, kernel breakage percentage, water adsorption rate, gelatinization enthalpy, peak enthalpy, and fatty acid profiles (C16:0, C18:0, C18:3n3, C20:0 and C20:1) were significantly related to the cumulative intergranular air properties of grain bulk. Conclusion: The above physio-chemical parameters were significantly influenced by the minimum and mean cumulative values of relative humidity, Humidity ratio and DPT in the bulk, and can be used to evaluate the quality of shelled corn with slightly high MC during short-term storage.

Effects of Climatic Conditions and Supplementation with Palm Cake on the Thermoregulation of Crossbred Buffaloes Raised in a Rotational Grazing System and with Natural Shade in Humid Tropical Regions.

In ruminants, diet composition has a positive correlation with heat production, which can influence thermoregulation, energy expenditure and, consequently, animal performance. The objective of this work was to evaluate the effects of climatic conditions and supplementation based on palm kernel cake, on the thermoregulation of crossbred buffaloes in the eastern Amazon. The research was carried out at Embrapa Amazônia Oriental (01°26' S and 48°24' W), Belém, Pará, and lasted 12 months (representing the entire year). Twenty-four buffaloes, females, with initial age and an average weight of 54 ± 7 months and 503.1 ± 23 kg, respectively, non-pregnant, non-lactating and clinically healthy were used, divided into four treatments based on the supplementation content of the palm cake (%DM) in relation to their body weight (%): 0, 0.25, 0.50 and 1.0. The animals were kept in paddocks with Brachiaria brizantha (cv. Marandu), in a rotating system, with water to drink and mineral salt ad libitum. Equipment was installed to record environmental data (temperature and relative humidity, dew point temperature, wet bulb and black globe) and physiological data: rectal temperature (RT); respiratory rate (RR); and body surface temperature (BST), recorded twice a day, always in the morning (6:00 a.m. to 7:00 a.m.) and afternoon (12:00 p.m. to 1:00 p.m.) shifts, and were used to calculate the Globe Temperature and Humidity Index (GTHI). Supplementation did not influence the physiological variables of thermoregulation (p > 0.05). However, there were differences in the GTHI between the shifts, with higher means in the afternoon shift, especially in the less rainy period of the year, where the GTHI reached 92.06 ± 2.74 (p < 0.05). In all periods of the year, the mean values of RT, RR and BST were higher in the afternoon shift (p > 0.05). The respiratory rate (RR) is associated with the annual seasonality of the thermal waters, with higher averages in the afternoons of the rainy season. The positive correlation for rectal temperature, respiratory rate and body surface temperature indicated that buffaloes respond to thermal elevations in the atmosphere (afternoon period) and, consequently, reflect on the GTHI. Supplementation does not influence thermoregulation; the changes observed occurred in response to the region's thermal and rainfall conditions (mainly in the afternoon shift), with higher GTHI values.

Thermal-Economic Analysis of an Organic Rankine Cycle System with Direct Evaporative Condenser

The organic Rankine cycle (ORC) system for power generation has proven to be an effective technology for low-temperature waste heat utilization. Accurate prediction and comprehensive comparison of system performance under different conditions are necessary for the development and application of suitable ORC configurations. This paper proposed an organic Rankine cycle (ORC) system using a direct evaporative condenser to realize performance enhancement and analyzed its dynamic performance based on the actual climatic condition, which is beneficial for the performance optimization of this system. This study begins with an introduction to the thermal economics model of the proposed system and evaluates the performance of the system based on the 3E (energy, exergy, economy) analysis method. Secondly, four candidate working fluids were compared and analyzed, leading to the selection of R142b as the best working fluid for the proposed system. Finally, the dynamic performance of the proposed system using the working fluid of R142b was analyzed based on the hourly environment temperature. The result showed that the net thermos-electric conversion efficiency of the system was negatively correlated with the ambient wet-bulb temperature. The annual average exergy efficiency of the system is about 65.79%, and the average exergy loss of the heat absorption unit, evaporative condenser, pump, and expander account for 61.07%, 6.92%, 2.99%, and 29.01% of the exergy loss of the system respectively. In the case 8760 h of operation per year, the payback period of the proposed ORC system using direct evaporative condenser is about 2.14 years.

Estimating rectal temperature in exercising horses in a competition environment using infrared thermal imaging

Abstract Short-term intense and or prolonged medium intensity exercise in conditions of moderate-high environmental temperature or temperature and humidity can result in moderate to marked hyperthermia. This in turn may result in decreased exercise capacity, earlier onset of fatigue and increased risk of falls or injury. Early identification of moderate-severe hyperthermia is important to allow appropriate intervention, either before, during or after exercise. Infra-red thermal imaging (IRT) allows measurement of horse surface temperature non-invasively, however it is generally considered to be unreliable in outdoor environments. Collection of pilot data suggested that this modality warranted further investigation. IRT Images were obtained from horses during training and competition at the 2019 Ready Steady Tokyo Olympic equestrian test event (Wet Bulb Globe Temperature [WBGT] &gt; 28 °C), during and after the cross-country at the 2019 Burghley Horse Trials CCI 5* (WBGT 12-15 °C), the 2019 Adelaide International Horse Trials CCI 4* (WBGT ∼ 20 °C) and during the 2020 Tokyo Olympic Games (held in 2021; WBGT &gt; 28 °C). A total of 87 paired hindquarter IRT images and rectal temperature measurements were obtained. When all data from all 4 events were pooled the bias and limits of agreement were −0.3 ± 1.1 °C (n = 87), i.e. IRT underestimated rectal temperature. When the data from Ready Steady Tokyo 2019 and Tokyo 2020 were combined as both events took place in similar thermal environmental conditions) the bias and limits of agreement were −0.1 ± 0.8 °C (n = 45). For 29 paired hindquarter thermal images, where a second image was obtained within 15 s, there was no significant difference between the mean of the first and second images (Image 1: 38.9 ± 0.9 °C versus Image 2: 38.7 ± 0.8 °C; ; n = 29). In conclusion, IRT imaging in environmental conditions of high temperature or high temperature and humidity may be useful in identifying horses with moderate to severe hyperthermia.

Quantifying Exercise Heat Acclimatisation in Athletes and Military Personnel: A Systematic Review and Meta-analysis.

Athletes and military personnel are often expected to compete and work in hot and/or humid environments, where decrements in performance and an increased risk of exertional heat illness are prevalent. A physiological strategy for reducing the adverse effects of heat stress is to acclimatise to the heat. The aim of this systematic review was to quantify the effects of relocating to a hotter climate to undergo heat acclimatisation in athletes and military personnel. Studies investigating the effects of heat acclimatisation in non-acclimatised athletes and military personnel via relocation to a hot climate for < 6weeks were included. MEDLINE, SPORTDiscus, CINAHL Plus with Full Text and Scopus were searched from inception to June 2022. A modified version of the McMaster critical review form was utilised independently by two authors to assess the risk of bias. A Bayesian multi-level meta-analysis was conducted on five outcome measures, including resting core temperature and heart rate, the change in core temperature and heart rate during a heat response test and sweat rate. Wet-bulb globe temperature (WBGT), daily training duration and protocol length were used as predictor variables. Along with posterior means and 90% credible intervals (CrI), the probability of direction (Pd) was calculated. Eighteen articles from twelve independent studies were included. Fourteen articles (nine studies) provided data for the meta-analyses. Whilst accounting for WBGT, daily training duration and protocol length, population estimates indicated a reduction in resting core temperature and heart rate of - 0.19°C [90% CrI: - 0.41 to 0.05, Pd = 91%] and - 6beats·min-1 [90% CrI: - 16 to 5, Pd = 83%], respectively. Furthermore, the rise in core temperature and heart rate during a heat response test were attenuated by - 0.24°C [90% CrI: - 0.67 to 0.20, Pd = 85%] and - 7beats·min-1 [90% CrI: - 18 to 4, Pd = 87%]. Changes in sweat rate were conflicting (0.01L·h-1 [90% CrI: - 0.38 to 0.40, Pd = 53%]), primarily due to two studies demonstrating a reduction in sweat rate following heat acclimatisation. Data from athletes and military personnel relocating to a hotter climate were consistent with a reduction in resting core temperature and heart rate, in addition to an attenuated rise in core temperature and heart rate during an exercise-based heat response test. An increase in sweat rate is also attainable, with the extent of these adaptations dependent on WBGT, daily training duration and protocol length. CRD42022337761.

Physiological Responses in Broiler Chickens Administered Lycopene During the Hot-Dry Season

Abstract This study evaluates the effects of lycopene administration on body weight, mortality, cloacal temperature, and haematological responses, in broiler chickens exposed to heat stress. 40 day-old broiler chicks were divided into control and lycopene groups, 20 chickens each. Each bird in the control group received olive oil (1 ml.kg−1), and lycopene at 10 mg.kg−1 mixed with olive oil was given to each bird in the lycopene group by oral gavage once daily for 28 days. The dry- and wet-bulb temperature of the broiler chickens’ pen was recorded three times daily from days 8 to 28. The body weights were measured weekly. The incidence of mortality was recorded. The cloacal temperatures were measured on days 14, 21 and 28. The blood samples were collected for haematological analyses, on day 28. The results indicated a high overall temperature-humidity index (31.24 ± 0.43 oC) of the thermal micro-environment of the broiler chickens. There was no significant difference (P &gt; 0.05) in body weight. The percentage mortality in the control group was relatively higher compared to the lycopene group. Lycopene reduced the cloacal temperature responses and the daily fluctuations in broiler chickens. The decreased (P &lt; 0.05) heterophil:lymphocyte ratio and percentage erythrocytes haemolysis were recorded in the lycopene group. In conclusion, lycopene administration reduced mortality and improved cloacal temperature and haematological responses without exerting any significant beneficial or negative effects on the body weight in broiler chickens exposed to heat stress.

A physiological approach for assessing human survivability and liveability to heat in a changing climate

Most studies projecting human survivability limits to extreme heat with climate change use a 35 °C wet-bulb temperature (Tw) threshold without integrating variations in human physiology. This study applies physiological and biophysical principles for young and older adults, in sun or shade, to improve current estimates of survivability and introduce liveability (maximum safe, sustained activity) under current and future climates. Our physiology-based survival limits show a vast underestimation of risks by the 35 °C Tw model in hot-dry conditions. Updated survivability limits correspond to Tw~25.8–34.1 °C (young) and ~21.9–33.7 °C (old)—0.9–13.1 °C lower than Tw = 35 °C. For older female adults, estimates are ~7.2–13.1 °C lower than 35 °C in dry conditions. Liveability declines with sun exposure and humidity, yet most dramatically with age (2.5–3.0 METs lower for older adults). Reductions in safe activity for younger and older adults between the present and future indicate a stronger impact from aging than warming.

Forecasting large hail and lightning using additive logistic regression models and the ECMWF reforecasts

Abstract. Additive logistic regression models for lightning (ARlig) and large hail (ARhail) were developed using convective parameters from the ERA5 reanalysis, hail reports from the European Severe Weather Database (ESWD), and lightning observations from the Met Office Arrival Time Difference network (ATDnet). The models yield the probability of lightning and large hail in a given timeframe over a particular grid point. To explore the value of this approach to medium-range forecasting, the models were applied to the European Centre for Medium Range Weather Forecasts (ECMWF) reforecasts to reconstruct probabilistic lightning and large hail forecasts for 11 ensemble members, from 2008 to 2019 and for lead times up to 228 h. The lightning and large hail models were based on different predictor parameters: most unstable convective available potential energy (CAPE), 925–500 hPa bulk shear, mixed layer mixing ratio, wet bulb zero height (for large hail), most unstable lifted index, mean relative humidity between 850 and 500 hPa, 1 hourly accumulated convective precipitation and specific humidity at 925 hPa (for lightning). First, we compared the lightning and hail ensemble forecasts for different lead times with observed lightning and hail focusing on a recent hail outbreak. Second, we evaluated the predictive skill of the model as a function of forecast lead time using the area under the ROC curve (AUC) as a validation score. This analysis showed that ARhail has a very high predictive skill (AUC &gt; 0.95) for a lead time up to 60 h. ARhail retains a high predictive skill even for extended forecasts (AUC = 0.86 at 180 h lead time). Although ARlig exhibits a lower predictive skill than ARhail, lightning forecasts are also skilful both in the short term (AUC = 0.92 at 60 h) and in the medium range (AUC = 0.82 at 180 h). Finally, we compared the performance of the 4-dimensional hail model with that of composite parameters such as the significant hail parameter (SHP) or the product of CAPE and the 925–500 hPa bulk shear (CAPESHEAR). Results show that ARhail outperforms CAPESHEAR at all lead times and SHP at short-to-medium lead times. These findings suggests that the combination of additive logistic regression models and ECMWF ensemble forecasts can create highly skilful medium-range hail and lightning forecasts for Europe.

Classification of precipitation types in Poland using machine learning and threshold temperature methods

The phase in which precipitation falls—rainfall, snowfall, or sleet—has a considerable impact on hydrology and surface runoff. However, many weather stations only provide information on the total amount of precipitation, at other stations series are short or incomplete. To address this issue, data from 40 meteorological stations in Poland spanning the years 1966–2020 were utilized in this study to classify precipitation. Three methods were used to differentiate between rainfall and snowfall: machine learning (i.e., Random Forest), daily mean threshold air temperature, and daily wet bulb threshold temperature. The key findings of this study are: (i) the Random Forest (RF) method demonstrated the highest accuracy in rainfall/snowfall classification among the used approaches, which spanned from 0.90 to 1.00 across all stations and months; (ii) the classification accuracy provided by the mean wet bulb temperature and daily mean threshold air temperature approaches were quite similar, which spanned from 0.86 to 1.00 across all stations and months; (iii) Values of optimized mean threshold temperature and optimized wet bulb threshold temperature were determined for each of the 40 meteorological stations; (iv) the inclusion of water vapor pressure has a noteworthy impact on the RF classification model, and the removal of mean wet bulb temperature from the input data set leads to an improvement in the classification accuracy of the RF model. Future research should be conducted to explore the variations in the effectiveness of precipitation classification for each station.

Ice accretion compositions in ice crystal icing

Ice crystal icing is a major hazard in aviation from the perspectives of aerodynamic deterioration, flight safety and operability. To counter this challenge, existing ice prediction tools require more accurate modeling of sticking efficiency of glaciated ice crystals on heated substrates. As part of the present study, icing wind tunnel experiments have been performed to quantify the volumetric liquid water fraction in the ice layers, the sticking efficiency of impacting ice crystals and the maximum thickness of ice layers accreted on a dedicated test article for a wide range of experimental conditions. To achieve this objective, two measurement techniques, calorimetry and capacitive measurements, have been employed to quantify the average liquid water content and the distribution of liquid in the ice layers. The experiments show that when switching from negative to positive wet bulb temperatures, the sticking efficiency and maximum thickness of ice layers increase significantly. A similar trend is observed for increasing substrate heat flux, which results in an increasing liquid fraction in the ice layer measured by calorimetry, as well as increasing sticking efficiency and maximum thickness of the ice layers. Increasing the ice water content does not have a significant influence on the liquid content, but leads to more pronounced erosion effects. The conducted experiments provide an unprecedented insight into the liquid distribution in ice accretions and its effect on the sticking efficiency. These results provide a sound basis for more accurate modeling of sticking efficiency and enhances the understanding of ice accretion processes.

Observed Warming Trends at U.S. Army Basic Combat Training Installations andImplications forFuture Recruit Training.

Army recruits conducting BCT are among the most susceptible population of military personnel to experience exertional heat illness, a concern expected to become increasingly urgent due to steadily rising temperatures. In this study, we provide an empirical analysis of wet bulb globe temperature (WBGT) index trends at U.S. Army BCT installations and quantify the magnitude of these trends. Assuming these warming trends continue, the anticipated effects of increasing temperature trends are discussed in relation to potential impacts on recruit heat illness incidence and training disruption. We obtained weather data beginning in the early 1960s, including WBGT index measurements derived by the U.S. Air Force 14th Weather Squadron. We apply these datasets to two classifications for high WBGT index days, including one classification accounting for heat illness susceptibility based on prior day heat exposure, to determine when recruits are most at risk of heat illness. The daily likelihood of extreme WBGT index values is described at each installation using a 30-year climatological average. Trends in the WBGT index are evaluated quantitatively during the warm season (May 1-September 30) and full year and compared between decades and by individual BCT classes. Trends in the WBGT index have increased at all four BCT installations. Between January 1960 and October 2022, the mean WBGT index value increased most quickly at Ft Jackson, SC (0.272°C decade-1, CI: 0.255-0.289) and least at Ft Moore, GA (0.190°C decade-1, CI: 0.170-0.210). Ft Moore experiences the greatest heat burden, with the daily likelihood of experiencing a "black flag" event (≥90°F WBGT index) peaking at nearly 50% in late July, while Ft Leonard Wood, MO, experiences the least heat burden. This heat burden is spread unevenly across installations and dependent on BCT class start date. Recruits beginning in mid-June will experience approximately 200 hours of hazardous heat during BCT at Ft Moore, GA; 100 hours at Ft Jackson, SC; 80 hours at Ft Sill, OK; and 61 hours at Ft Leonard Wood, MO. Temperatures measured on the WBGT index have steadily increased at US Army basic training installations since at least 1960. In the future, adaptation to the BCT program will be required to maintain rigorous standards without incurring unacceptable risk of recruit heat illness. The analysis provided by this study can help inform medical, training, and policy implementations needed to ensure continued BCT in a warming world.

Regimes of Soil Moisture–Wet-Bulb Temperature Coupling with Relevance to Moist Heat Stress

Abstract Human heat stress depends jointly on atmospheric temperature and humidity. Wetter soils reduce temperature but also raise humidity, making the collective impact on heat stress unclear. To better understand these interactions, we use ERA5 to examine the coupling between daily average soil moisture and wet-bulb temperature (Tw) and its seasonal and diurnal cycle at global scale. We identify a global soil moisture–Tw coupling pattern with both widespread negative and positive correlations in contrast to the well-established cooling effect of wet soil on dry-bulb temperature. Regions showing positive correlations closely resemble previously identified land–atmosphere coupling hotspots where soil moisture effectively controls surface energy partition. Soil moisture–Tw coupling varies seasonally closely tied to monsoon development, and the positive coupling is slightly stronger and more widespread during nighttime. Local-scale analysis demonstrates a nonlinear structure of soil moisture–Tw coupling with stronger coupling under relatively dry soils. Hot days with high Tw values show wetter-than-normal soil, anomalous high latent and low sensible heat flux from a cooler surface, and a shallower boundary layer. This supports the hypothesis that wetter soil increases Tw by concentrating surface moist enthalpy flux within a shallower boundary layer and reducing free-troposphere-air entrainment. We identify areas of particular interest for future studies on the physical mechanisms of soil moisture–heat stress coupling. Our findings suggest that increasing soil moisture might amplify heat stress over large portions of the world including several densely populated areas. These results also raise questions about the effectiveness of evaporative cooling strategies in ameliorating urban heat stress. Significance Statement The purpose of this study is to provide a global picture of the relationship between soil moisture anomalies and a heat stress metric that includes the joint effects of temperature and humidity. This is important because a better understanding of this relationship will help improve the prediction of extreme heat stress events and inform strategies for ameliorating heat stress. We find a widespread positive correlation between soil moisture and heat stress, in contrast to studies relying on temperature alone. This raises the possibility that, over much of the world, and in the most populous regions, strategies like irrigation or “greening” that can reduce temperature might be ineffective or even harmful in reducing heat stress with humidity incorporated.

Assessment of Climate Change Impacts and Water Restrictions on Solar Tower Plants

Climate projections under the high-emission representative concentration pathway “RCP-8.5” scenario are used to show the effects of global warming on the energy production of two similar concentrated solar tower power plants in Spain and Chile from 2025 to 2060. Results show a reduction of the annual energy production of almost 1.8% for Chile and an increase of almost 6% in the Spanish plant, but an increase of 10% water consumption due to both the increase in dry- and wet-bulb temperatures and changes in the direct normal irradiation caused by climate change. When the effect of water restrictions is included in the model caused by the foreseen reduction in water availability in Spain, the increase of the annual energy production is only 2%. Finally, the levelized cost of energy (LCOE) calculated during the whole power plant lifetime (35 years) with respect to the LCOE obtained at the beginning of the project is increased by 1.1% in the Chilean plant, whereas in the Spanish plant, it can be reduced more than 2.5% if there are no water restrictions, while a reduction of 0.4% is expected in a scenario with water restrictions. Results show that careful consideration of climate projections should be considered to properly estimate the economic viability of solar tower plants.

A pilot heat-health warning system co-designed for a subtropical city.

Significant heat-related casualties underlie the urgency of establishing a heat-health warning system (HHWS). This paper presents an evidence-based pilot HHWS developed for Taipei City, Taiwan, through a co-design process engaging stakeholders. In the co-design process, policy concerns related to biometeorology, epidemiology and public health, and risk communication aspects were identified, with knowledge gaps being filled by subsequent findings. The biometeorological results revealed that Taipei residents were exposed to wet-bulb globe temperature (WBGT) levels of health concern for at least 100 days in 2016. The hot spots and periods identified using WBGT would be missed out if using temperature, underlining the importance of adopting an appropriate heat indicator. Significant increases in heat-related emergency were found in Taipei at WBGT exceeding 36°C with reference-adjusted risk ratio (RaRR) of 2.42, taking 30°C as the reference; and residents aged 0-14 had the highest risk enhancement (RaRR = 7.70). As for risk communication, occurring frequency was evaluated to avoid too frequent warnings, which would numb the public and exhaust resources. After integrating knowledge and reconciling the different preferences and perspectives, the pilot HHWS was co-implemented in 2018 by the science team and Taipei City officials; accompanying responsive measures were formulated for execution by ten city government departments/offices. The results of this pilot served as a useful reference for establishing a nationwide heat-alert app in 2021/2022. The lessons learnt during the interactive co-design processes provide valuable insights for establishing HHWSs worldwide.

Multi-Index Analysis of Spatiotemporal Variations of Dry Heat Waves and Humid Heat Waves in China

Heat waves, particularly humid heat waves that occur together with high temperatures and humidity, pose a severe hazard to human health in the context of global warming. In this work, daily observations from more 1500 sites are used to define dry and humid heat waves in a warm season (May to September) and assess their spatiotemporal characteristics during 1960–2015. Dry heat waves are identified with daily maximum temperatures, while humid heat waves are identified based on the wet bulb temperature, derived from both temperature and humidity. We compare dry and humid heat waves from various aspects based on multiple heat wave indices, including their frequency, duration, and intensity. Results suggest that the occurrence of both dry and humid heat wave days in China is higher in the southern than in the northern part of China, due to the higher air temperature and humidity therein. Compared to dry heat waves, humid heat waves are of higher amplitude but shorter duration. The long-term trend analysis shows that the occurrence of both dry and humid heat waves has increased overall over the last 50 years, with an especially rapid increase in the last 20 years, which may be related to China’s rapid warming since the late 1980s. The future projections with multiple global climate models indicate that China will experience more frequent, stronger, and longer-duration dry and humid heat waves in the future, under both intermediate and high-emission pathways.

Increased extreme humid heat hazard faced by agricultural workers

Increases in population exposure to humid heat extremes in agriculturally-dependent areas of the world highlights the importance of understanding how the location and timing of humid heat extremes intersects with labor-intensive agricultural activities. Agricultural workers are acutely vulnerable to heat-related health and productivity impacts as a result of the outdoor and physical nature of their work and by compounding socio-economic factors. Here, we identify the regions, crops, and seasons when agricultural workers experience the highest hazard from extreme humid heat. Using daily maximum wet-bulb temperature data, and region-specific agricultural calendars and cropland area for 12 crops, we quantify the number of extreme humid heat days during the planting and harvesting seasons for each crop between 1979–2019. We find that rice, an extremely labor-intensive crop, and maize croplands experienced the greatest exposure to dangerous humid heat (integrating cropland area exposed to >27 °C wet-bulb temperatures), with 2001–2019 mean rice and maize cropland exposure increasing 1.8 and 1.9 times the 1979–2000 mean exposure, respectively. Crops in socio-economically vulnerable regions, including Southeast Asia, equatorial South America, the Indo-Gangetic Basin, coastal Mexico, and the northern coast of the Gulf of Guinea, experience the most frequent exposure to these extremes, in certain areas exceeding 60 extreme humid heat days per year when crops are being cultivated. They also experience higher trends relative to other world regions, with certain areas exceeding a 15 day per decade increase in extreme humid heat days. Our crop and location-specific analysis of extreme humid heat hazards during labor-intensive agricultural seasons can inform the design of policies and efforts to reduce the adverse health and productivity impacts on this vulnerable population that is crucial to the global food system.

Urban Versus Lake Impacts on Heat Stress and Its Disparities in a Shoreline City.

Shoreline cities are influenced by both urban-scale processes and land-water interactions, with consequences on heat exposure and its disparities. Heat exposure studies over these cities have focused on air and skin temperature, even though moisture advection from water bodies can also modulate heat stress. Here, using an ensemble of model simulations covering Chicago, we find that Lake Michigan strongly reduces heat exposure (2.75°C reduction in maximum average air temperature in Chicago) and heat stress (maximum average wet bulb globe temperature reduced by 0.86°C) during the day, while urbanization enhances them at night (2.75 and 1.57°C increases in minimum average air and wet bulb globe temperature, respectively). We also demonstrate that urban and lake impacts on temperature (particularly skin temperature), including their extremes, and lake-to-land gradients, are stronger than the corresponding impacts on heat stress, partly due to humidity-related feedback. Likewise, environmental disparities across community areas in Chicago seen for skin temperature are much higher (1.29°C increase for maximum average values per $10,000 higher median income per capita) than disparities in air temperature (0.50°C increase) and wet bulb globe temperature (0.23°C increase). The results call for consistent use of physiologically relevant heat exposure metrics to accurately capture the public health implications of urbanization.

Investigation of Heat Stress among Greenhouse Workers in Chhattisgarh, India

Greenhouse cultivation is spreading as it offers the grower a higher net yield per hectare from high quality crops as it reduces the likelihood of yield decline. The greenhouse is kept at 30-40˚ C with a relative humidity of up to 70%, which could be ideal for plant growth, but is not suitable for workers. Heat exposure in the workplace causes discomfort to the human while working. So, the main goal of conducting this research is to address the extent of heat stress and associated health issues for the greenhouse workers. The study was planned for 2022 in the Raipur district of Chhattisgarh. Prior to the assessment, a questionnaire survey was conducted among 50 greenhouse workers to learn perceptions of heat exposure, heat-related health issues and awareness of heat management. To get the heat exposure air temperature, wet bulb temperature, relative humidity, black globe temperature were measured on hourly basis. The wet bulb globe temperature (WBGT) was measured along with greenhouse workers' physiological parameters to quantify heat exposure. With the help of clock diagram showing Humidex Index (HI). The time period at which farmers most likely to suffer from heat stress was estimated. It was reported that in April, May, June, July, August and September WBGT index reaches varied between 30 and 34°C. According to ISO 7243 the recommended WBGT for comfortable workplace should be less than 31°C. Further study was conducted to get physiological responses of the 21 farm workers in three different type of greenhouses and at three time slots. It resulted that heart rate was maximum i.e. 156 bpm in walk in tunnel at 11 am to 1 pm. The average working heart rate was 20 % more than the open field condition. Hence, the study will help to make the strategies to reduce the exposure of heat stress conditions to the greenhouse workers.

Heat exposure and heat stress in outdoor workers: a review of measures in published studies

Abstract Background Increased ambient air temperatures resulting from climate change led to higher heat levels for outdoor workers. Heat exposure refers to ambient environmental heat exposures; while heat stress also considers the clothing type and the metabolic rate resulting from physical activity. We reviewed the types of heat exposure/stress measures used in published studies. Methods A literature review was conducted to identify and examine measures of heat exposure and heat stress in outdoor workers. Results The most common indices measuring heat exposure/stress in occupational health include the Wet Bulb Globe Temperature (WBGT), Environmental Stress Index (ESI), Heat Index (HI), Humidex (HD), and Discomfort Index (DI). HI, HD and DI account for ambient air temperature and relative humidity surrounding workers. WBGT accounts for air temperature, radiant temperature, humidity, speed of air movement, and adjusts for clothing and metabolic rate. ESI considers factors like WBGT except for speed of air and does not account for clothing and metabolic rate. Both ESI and WBGT fail to consider the risk of dehydration resulting from excessive sweating in hot work environments. HI, HD and DI measure heat exposure but not heat stress as they do not account for the metabolic rate; also, they do not consider radiation and may underestimate the potential danger of working in excessive heat. These indices are considered simpler to use than WBGT. However, WBGT is more precise and covers environmental factors influencing heat exposure/stress. Questionnaires are also used to assess workers’ perceptions of heat exposure and self-reported health impacts. Their findings, in general, have not been comparable due to the heterogeneity of questions used. Conclusions Although WBGT is recommended for accurate measures of heat exposure/stress, its high cost has been a deterrent for workplaces in low-income countries. Projects with low financial resources opt for simpler and cheaper measures of heat. Key messages • The use of reliable devices is necessary to measure and monitor heat exposure in outdoor work. • It is desirable to generate homogenous results for the comparability of study findings in occupational health research.