A land surface effective temperature calculation method to improve microwave emissivity retrieval over barren areas

During a simulated haemorrhagic challenge, syncopal symptoms develop sooner when individuals are hyperthermic relative to normothermic. This is due, in part, to a large displacement of blood to the cutaneous circulation during hyperthermia, coupled with inadequate cutaneous vasoconstriction during the hypotensive challenge. The influence of local skin temperature on these cutaneous vasoconstrictor responses is unclear. This project tested the hypothesis that local skin temperature modulates cutaneous vasoconstriction during simulated haemorrhage in hyperthermic humans. Eight healthy participants (four men and four women; 32 ± 7 years old; 75.2 ± 10.8 kg) underwent lower-body negative pressure to presyncope while heat stressed via a water-perfused suit sufficiently to increase core temperature by 1.2 ± 0.2 °C. At forearm skin sites distal to the water-perfused suit, local skin temperature was either 35.2 ± 0.6 (mild heating) or 38.2 ± 0.2 °C (moderate heating) throughout heat stress and lower-body negative pressure, and remained at these temperatures until presyncope. The reduction in cutaneous vascular conductance during the final 90 s of lower-body negative pressure, relative to heat-stress baseline, was greatest at the mildly heated site (-10 ± 15% reduction) relative to the moderately heated site (-2 ± 12%; P = 0.05 for the magnitude of the reduction in cutaneous vascular conductance between sites), because vasoconstriction at the moderately heated site was either absent or negligible. In hyperthermic individuals, the extent of cutaneous vasoconstriction during a simulated haemorrhage can be modulated by local skin temperature. In situations where skin temperature is at least 38 °C, as is the case in soldiers operating in warm climatic conditions, a haemorrhagic insult is unlikely to be accompanied by cutaneous vasoconstriction.

This paper reports on two types of comparisons that were conducted. First, 10-yr modeled skin temperatures were compared with observations to evaluate model simulations of this quantity. The simulations were conducted with the NCAR CCM2 coupled with the Biosphere‐Atmosphere Transfer Scheme (BATS). The observations were obtained from TIROS-N/HIRS-2 and the First ISLSCP Field Experiment in situ measurements. Second, modeled skin temperatures were compared with surface-air temperatures to illustrate the differences between them at various spatial and temporal resolutions. This is the first such study of skin temperature in a GCM. When compared with the observations, it is evident that the CCM2‐BATS can successfully reproduce many features of skin temperature, including its global-scale pattern, seasonal and diurnal variations, and the effects of the land surface type. However, modeled skin temperature seems to be underestimated in high latitudes in January and overestimated in low- and midlatitudes, especially over arid and semiarid regions in July. Statistical analyses suggest that the differences between skin and surface-air temperatures are scale dependent. They differ the most at smaller scales and are most similar at larger scales (i.e., they differ the most for regional scales and diurnally, and agree more closely on monthly scales and hemispheric spatial scales). The similarity between skin and air temperatures averaged over monthly and large spatial scales implies that the well-established surface-air temperature measurements may be used to validate satellite-obtained skin temperatures. The differences between skin temperature and air temperature are greatest in the winter hemisphere. The monthly maximum skin temperature is greater than maximum air temperature by about 3.58‐5.58C, and minimum skin temperature is less than minimum air temperature by 3.08‐4.58C. For monthly time averaging and continental or hemispheric spatial scales, skin temperature is consistently lower than air temperature by about 0.5 8‐1.08C. This work also studies the effects of different land types, vegetative cover, soil wetness, and cloud cover on skin temperature. These effects are partially responsible for the differences between skin and surface-air temperatures. These results are similar to those from earlier studies done at specific sites.

The contribution of mean skin temperature to the thresholds for sweating and active precapillary vasodilation has been evaluated in numerous human studies. In contrast, the contribution of skin temperature to the control of cold responses such as arteriovenous shunt vasoconstriction and shivering is less well established. Accordingly, the authors tested the hypothesis that mean skin and core temperatures are linearly related at the vasoconstriction and shivering thresholds in men. Because the relation between skin and core temperatures might vary by gender, the cutaneous contribution to thermoregulatory control also was determined in women. In the first portion of the study, six men participated on 5 randomly ordered days, during which mean skin temperatures were maintained near 31, 34, 35, 36, and 37 degrees C. Core hypothermia was induced by central venous infusion of cold lactated Ringer's solution sufficient to induce peripheral vasoconstriction and shivering. The core-temperature thresholds were then plotted against skin temperature and a linear regression fit to the values. The relative skin and core contributions to the control of each response were calculated from the slopes of the regression equations. In the second portion of the study, six women participated on three randomly ordered days, during which mean skin temperatures were maintained near 31, 35, and 37 degrees C. At each designated skin temperature, core hypothermia sufficient to induce peripheral vasoconstriction and/or shivering was again induced by central venous infusion of cold lactated Ringer's solution. The cutaneous contributions to control of each response were then calculated from the skin- and core-temperature pairs at the vasoconstriction and shivering thresholds. There was a linear relation between mean skin and core temperatures at the response thresholds in the men: r = 0.90 +/- 0.06 for vasoconstriction and r = 0.94 +/- 0.07 for shivering. Skin temperature contributed 20 +/- 6% to vasoconstriction and 19 +/- 8% to shivering. Skin temperature in the women contributed to 18 +/- 4% to vasoconstriction and 18 +/- 7% to shivering, values not differing significantly from those in men. There was no apparent correlation between the cutaneous contributions to vasoconstriction and shivering in individual volunteers. These data indicate that skin and core temperatures contribute linearly to the control of vasoconstriction and shivering in men and that the cutaneous contributions average approximately 20% in both men and women. The same coefficients thus can be used to compensate for experimental skin temperature manipulations in men and women. However, the cutaneous contributions to each response vary among volunteers; furthermore, the contributions to the two responses vary within volunteers.

Working towards a community-wide understanding of satellite skin temperature observations

ABSTRACTPlanners and policy makers require information about the regions for which they are responsible. However, it seems that many developing countries, including Nigeria, are not adequately prepared either for their current climates or for the impact of climate change because they lack sufficient information. We have therefore examined the variations in the thermal condition in terms of the temperature, relative humidity, effective temperature (ET), temperature–humidity index (THI) and relative strain index (RSI). We studied the spatial and temporal (1951–2009, 1951–1980, 1981–2009, decadal, seasonal and monthly averages) variations in the thermal climate of Nigeria, and we divided Nigeria into thermal climate regions for effective climate change management. Mean annual minimum, mean and maximum temperatures (with their standard deviations) were 21.4 (3.5), 27.1 (2.7) and 32.8 (3.4) °C, respectively, while the overall mean relative humidity was 62 (24.8)%. Mean ET, THI and RSI were 24.3 (0.85), 24.8 (1.83) and 0.2 (0.18) °C, respectively. The ET, THI and RSI provided contrasting expressions of thermal comfort for Nigeria, because of its varied climate. We also found that elevation; the movement of the Inter Tropical Discontinuity and urbanization affect thermal comfort in Nigeria. We conclude that thermal stress has increased in Nigeria from 2000 at most stations, especially in the south and north‐western regions, and that Nigerian thermal comfort climate is heterogeneous and requires analysis of multiple thermal indices.

We performed a new and accurate fit of light and radial velocity curves of the Large Magellanic Cloud (LMC) Cepheid --OGLE-LMC-CEP-0227-- belonging to a detached double-lined eclipsing binary system. We computed several sets of nonlinear, convective models covering a broad range in stellar mass, effective temperature and in chemical composition. The comparison between theory and observations indicates that current theoretical framework accounts for luminosity --V and I band-- and radial velocity variations over the entire pulsation cycle. Predicted pulsation mass --M=4.14+-0.06 Mo-- and mean effective temperature --Te=6100+-50 K-- do agree with observed estimates with an accuracy better than 1 sigma. The same outcome applies, on average, to the luminosity amplitudes and to the mean radius. We find that the best fit solution requires a chemical composition that is more metal--poor than typical LMC Cepheids (Z=0.004 vs 0.008) and slightly helium enhanced (Y=0.27 vs 0.25), but the sensitivity to He abundance is quite limited. Finally, the best fit model reddening --E(V-I)=0.171+-0.015 mag-- and the true distance modulus corrected for the barycenter of the LMC --mu_{0,LMC}=18.50+-0.02+-0.10 (syst) mag--, agree quite well with similar estimates in the recent literature.

Passive body heating in controlled settings could shorten sleep onset latency (SOL). The hypothesized mechanism is vasodilation-induced heat loss before bedtime. However, this evidence is based on small sample-sized studies in specific populations. Thus, we analyzed the association of hot-water bathing and its before-bedtime timing with SOL and heat loss in a large study population of older adults. We conducted a longitudinal analysis using repeated measurements of hot-water bathing and sleep among 1,094 older adults (mean age, 72.0 years). SOL was recorded using actigraphy and self-reported sleep estimates and was categorized into conditions (intervals of 1-60, 61-120, 121-180, and > 181 minutes between hot bath and bedtime) and compared with the control condition of no bathing. The heat-loss indicator, distal-proximal skin temperature gradient, was examined in the same categorization. Mixed-effects linear regression models suggested that the bathing conditions of 61-120 minutes and 121-180 minutes showed significantly shorter log-transformed actigraphic SOL by 0.23 log-minutes (95% confidence interval (CI), 0.03-0.42) and 0.32 log-minutes (95% CI, 0.09-0.56), shorter self-reported SOL by 0.16 log-minutes (95% CI, 0.02-0.30) and 0.18 log-minutes (95% CI, 0.01-0.35), and higher distal-proximal skin temperature gradient for 30 minutes before bedtime by 0.49°C (95% CI, 0.22-0.75) and 0.51°C (95% CI, 0.20-0.83), respectively, independent of potential confounders. Hot-water bathing before bedtime is significantly associated with shorter SOL and higher distal-proximal skin temperature gradient among the large-scale older population. This finding could enhance the generalizability of hot-water bathing habits for ameliorating sleep initiation difficulty.

Flow connectivity in active volcanic areas: Use of index of connectivity in the assessment of lateral flow contribution to main streams

PurposeMotivation plays a key role in the decision to initiate a change in behavior. Animal models employing operant techniques indicate that the motivation to behaviorally thermoregulate is dependent on the magnitude of changes in body temperature. Similarly, behavioral thermoregulation in humans is driven by the extent of changes in skin and/or core body temperatures. However, motivation to behaviorally thermoregulate has not been quantified in humans. Therefore, we tested the hypothesis that the motivation to behaviorally thermoregulate in humans is dependent on the magnitude of changes in body temperature.MethodsFollowing 10 min of seated rest in a 23.6 ± 1.7°C environment, seven healthy subjects (22 ± 2 y, 3 females) underwent 60 min of seated rest in 32.2 ± 0.6°C (T32) or 42.3 ± 0.7°C (T42) environment (20% relative humidity). Trials were completed in in a counterbalanced order separated by one week. The motivation to behaviorally thermoregulate was measured using operant responding on a fixed ratio schedule, in which subjects received thermal reinforcement after clicking a button 100 times. The reinforcer was 30 s of cooling on the dorsal aspect of the neck, an area highly sensitive to cooling during heat exposure. Cooling was enabled via a custom‐made device in which tubing was perfused with −20°C fluid. The motivation to behave was defined as the cumulative number of button clicks over time and behavioral thermoregulation was defined as the change in neck skin temperature. Neck skin temperature, mean skin (10 site), and intestinal temperatures were measured continually. Data are presented as mean ± SD.ResultsThere were no differences in mean skin temperature (T32: 31.6 ± 1.0°C, T42:31.4 ± 0.8°C, P=0.47), intestinal temperature (T32: 37.3 ± 0.2°C, T42: 37.3 ± 0.3°C, P>0.99) or neck skin temperature (T32: 34.3 ± 0.6°C, T42: 34.0 ± 0.4°C, P=0.95) before heat exposure. The increase in mean skin temperature was greater in T42 (at 60 min: +4.9 ± 0.8°C) vs. T32 (at 60 min: +2.9 ± 0.8°C, P<0.01). Intestinal temperature during heat exposure decreased from pre‐heat exposure (P≤0.04), but did not differ between conditions (at 60 min ‐ T32: 37.1 ± 0.2°C, T42: 37.2 ± 0.2°C, P=0.16). Neck skin temperature was lower throughout heat exposure in T42 (at 60 min: 33.5 ± 1.9°C) compared to T32 (at 60 min: 34.8 ± 0.2°C, P<0.01). Cumulative responding for the thermal reinforcer increased at 20 min in T42 (P≤0.04), but did not change over time in T32 (P≥0.07). Thus, cumulative responding was greater in T42 (229 ± 160 clicks) compared to T32 (0 ± 0 clicks, P=0.01) at 20 min, which persisted throughout heat exposure (at 60 min ‐ T42: 986 ± 481 clicks, T32: 214 ± 168 clicks, P<0.01).ConclusionsThese data indicate that the motivation to receive thermal reinforcement during heat exposure is dependent on the magnitude of changes in mean skin temperature. Thus, in support of previous animal data, the motivation to behaviorally thermoregulate in humans is dependent on the magnitude of changes in body temperature.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The frequency of heat events is likely to increase due to global climate change, posing an increasing risk to wheat production. To optimize crop management strategies for coping with future climates, it is crucial to quantify the high-temperature occurrence during cropping seasons. Here, sixty-six years (1955~2020) of meteorological data during wheat reproductive growth were collected from six meteorological stations in the Huaibei Plain of Anhui Province. These data were analyzed to quantify the pattern and characteristics of post-anthesis heat stress for wheat crops. Five levels of annual mean daily maximum temperature (Tmax) were defined, from normal to extreme temperatures. Six crop developmental phases of winter wheat, i.e., phase i to phase vi, were divided from flowering to maturity. The data suggest an annual mean temperature of 17~24 °C from flowering to maturity, with an annual effective cumulative temperature ranging from 725 °C d to 956 °C d. The mean temperature and effective cumulative temperature increased as crop growth progressed, along with more frequent heat events during phase ii (8~14 days after anthesis) and phase iii (15~21 days after anthesis). We also found that the frequency of extremely high temperatures (≥33 °C) from 1990 to 2020 was significantly greater than that from 1957 to 1990. Interestingly, it was found that the intensity of post-anthesis night temperatures also increased with crop growth, i.e., from phase i to phase vi. Wheat grain yield increased with increasing effective accumulative temperature and Tmax, but it started to decline when thresholds of effective accumulative temperature and Tmax were reached. Overall, these findings could provide guidelines for winter wheat cropping in the Huaibei Plain, China, or similar climate and cropping regions.

Six women were exposed to nine environmental conditions, ranging from 26.0 to 35.8°C effective temperature (ET), in a climatic chamber. They were involved in manipulative work in a seated position for a duration of 3 hr. The O2 uptake, heart rate, deep body (Tc) and skin temperature (Tsk), sweat loss, and perception of thermal comfort were noted. The O2 uptake increased with the time of exposure at different heat levels. The work energy demand, which was 19% of Vo 2max at 26° C ET, increased to 35% ofVo 2max at 35.8°C ET. However, the work output declined with the increase in ET. Thus, the elevated metabolic demands were the results of the thermal stimuli. The Tsk was greatly influenced by the environmental heat; the Tc changes were gradual. The highest mean Tsk attained was 37.3°C at 33.8°C ET when the gradient of Tc–Tsk was only 0.5°C. The rate of change in mean Tsk for 31.6 to 33.8°C ET was much faster compared to the range between 26.0 and 31.6°C ET. From 32.1°C ET onward the Tc and heart rates rose rapidly, while the sweating rate tended to fall, indicating some hindrance for evaporative cooling. Also, thermal sensations were noted as extremely hot for the conditions 32.1 to 35.8°C ET with the increase in exposure duration.

Six women were exposed to nine environmental conditions, ranging from 26.0 to 35.8 degrees C effective temperature (ET), in a climatic chamber. They were involved in manipulative work in a seated position for a duration of 3 hr. The O2 uptake, heart rate, deep body (Tc) and skin temperature (Tsk), sweat loss, and perception of thermal comfort were noted. The O2 uptake increased with the time of exposure at different heat levels. The work energy demand, which was 19% of VO2max at 26 degree C ET, increased to 35% of VO2max at 35.8 degrees C ET. However, the work output declined with the increase in ET. Thus, the elevated metabolic demands were the results of the thermal stimuli. The Tsk was greatly influenced by the environmental heat; the Tc changes were gradual. The highest mean Tsk attained was 37.3 degrees C at 33.8 degrees C ET when the gradient of Tc-Tsk was only 0.5 degrees C. The rate of change in mean Tsk for 31.6 to 33.8 degrees C ET was much faster compared to the range between 26.0 and 31.6 degrees C ET. From 32.1 degrees C ET onward the Tc and heart rates rose rapidly, while the sweating rate tended to fall, indicating some hindrance for evaporative cooling. Also, thermal sensations were noted as extremely hot for the conditions 32.1 to 35.8 degrees C ET with the increase in exposure duration.

Thermoregulatory control is based on both skin and core temperatures. Skin temperature contributes approximately 20% to control of vasoconstriction and shivering in unanesthetized humans. However, this value has been used to arithmetically compensate for the cutaneous contribution to thermoregulatory control during anesthesia--although there was little basis for assuming that the relation was unchanged by anesthesia. It even remains unknown whether the relation between skin and core temperatures remains linear during anesthesia. We therefore tested the hypothesis that mean skin temperature contributes approximately 20% to control of vasoconstriction and shivering, and that the contribution is linear during general anesthesia. Eight healthy male volunteers each participated on 3 separate days. On each day, they were anesthetized with 0.6 minimum alveolar concentrations of isoflurane. They then were assigned in random order to a mean skin temperature of 29, 31.5, or 34 degrees C. Their cores were subsequently cooled by central-venous administration of fluid at approximately 3 degrees C until vasoconstriction and shivering were detected. The relation between skin and core temperatures at the threshold for each response in each volunteer was determined by linear regression. The proportionality constant was then determined from the slope of this regression. These values were compared with those reported previously in similar but unanesthetized subjects. There was a linear relation between mean skin and core temperatures at the vasoconstriction and shivering thresholds in each volunteer: r2 = 0.98+/-0.02 for vasoconstriction, and 0.96+/-0.04 for shivering. The cutaneous contribution to thermoregulatory control, however, differed among the volunteers and was not necessarily the same for vasoconstriction and shivering in individual subjects. Overall, skin temperature contributed 21+/-8% to vasoconstriction, and 18+/-10% to shivering. These values did not differ significantly from those identified previously in unanesthetized volunteers: 20+/-6% and 19+/-8%, respectively. The results in anesthetized volunteers were virtually identical to those reported previously in unanesthetized subjects. In both cases, the cutaneous contribution to control of vasoconstriction and shivering was linear and near 20%. These data indicate that a proportionality constant of approximately 20% can be used to compensate for experimentally induced skin-temperature manipulations in anesthetized as well as unanesthetized subjects.

Global warming combined with increased production (i.e. more piglets, more milk and consequently more heat) means that sows are more often challenged by heat stress. The objective was to develop an effective temperature (ET) equation to predict how air temperature, velocity and humidity affect the respiration rate (RR), rectal temperature (RT) and skin temperature (ST) as an expression of heat stress in gestating sows in order to elucidate the relationship between the thermal parameters and the sows' perception of the environment. The experimental room was equipped with a negative pressure ventilation system with diffuse air inlet through the ceiling, electrical heaters, steam generators and dehumidifiers. An air distribution unit was constructed to generate vertical air velocity. A total of 16 gestating sows were exposed to three temperatures (25°C, 29°C and 33°C), two levels of relative humidity (30% and 70%) and three levels of air velocity (0.2ms-1, 1ms-1 and 2.5ms-1). The RR, RT and ST were recorded every 30min throughout the three 2-h test periods. The estimated effects of humidity and velocity in relation to effect of temperature was nearly independent of whether it was determined from RR or RT, whereas the effect of humidity was much smaller when determined from ST. High coefficients of determination (>0.97) were found for the second order relationship between the estimated ET and RR, RT and ST. An increase in relative humidity from 50 to 70% corresponded to an increase in ET of 0.9°C, while an increase in air velocity from 0.2 to 1.0ms-1 corresponded to a decrease in ET of 1.2°C. The applied ET equation was useful for expressing the combined effect of temperature, humidity and velocity on animals exposed to heat stress. However, multiplying the effect of velocity by the temperature gradient between the animal and the surrounding air did not improve the estimation.

Body temperature homeostasis is accurately regulated by complex feedback-driven neuronal mechanisms, which involve a multitude of thermoregulatory pathways. Thus, core temperature is constantly maintained within a narrow range. As one of the most effective regulatory systems skin temperature is dependent on skin blood flow. Skin blood flow in turn is highly dependent on sympathetic activity. Regional anaesthesia leads to blockade not only of somatosensory and motor nerve fibres but also of sympathetic fibres. As a consequence, vasoconstrictor tonic activity is abrogated and a vasodilation leads to an increase in skin blood flow and temperature. The aim of this review was to summarize the general physiology of thermoregulation and skin temperature as well as the alterations during regional anaesthesia. The main focus was the usefulness of measuring skin temperature as an indicator of regional anaesthesia success. According to the available literature, assessment of skin temperature can indeed serve to predict success of regional anaesthesia. Hence, it is important to realize that relevant and reliable temperature increase is only seen in the most distal body parts, ie fingers and toes. More proximally, temperature changes are frequently small and inconsistent, which means that assessment of block levels is not possible by temperature measurement. Furthermore, relevant skin temperature increases will only be observed in patients, which are initially vasoconstricted. In conclusion, measurement of skin temperature represents a reliable and feasible diagnostic tool to assess and predict the success or failure of regional anaesthesia procedures, especially in patients in which sensory testing is impossible.