Diurnal Temperature Fluctuations Research Articles

Determining the In Situ Apparent Thermal Diffusivity of a Sandy Soil

ABSTRACT: The thermal wave amplitude method is used to determine soil thermal diffusivity in situ for a sandy soil in Mexico (Coatzacoalcos, Veracruz). Soil diurnal temperature fluctuations were measured from depths of 0.05 to 0.65 m, in 0.01 m increments, during the months of April and August. Five mean diffusivity values were obtained experimentally, corresponding to the different depths combination. The soil thermal diffusivity ranged between 2.26 × 10−7 and 8.71 × 10−7 m2 s−1. The diffusivity values obtained are [...]

Differences in heat tolerance within a Daphnia magna population: the significance of body PUFA content

In this study, we use the model organism Daphnia magna to determine variation in heat tolerance within a natural population and relate this to variation in body fatty acid content and composition. As a proxy for heat tolerance we measured time to immobilization (Timm) for 25 clonal lineages isolated from a single lake. The clonal lineages were grown on Chlamydomonas reinhardii at 15°C. Upon deposition of the first clutch, Timm and body fatty acids were determined. We report significant differences of Timm and of the content of PUFAs and of eicosapentaenoic acid (EPA) among the D. magna clonal lineages. Timm was negatively related to total PUFA-content, indicating that increased body PUFA-content may be detrimental for membrane properties at high temperatures. Juvenile somatic growth varied significantly among clonal lineages, and was not related to total body PUFA-content, hence body PUFA-content was no proxy for PUFA-limitation. No correlative evidence for an impact of body EPA-content on Timm or juvenile growth was obtained. We hypothesize that the observed intra-population variability of body PUFA-content might be related to potentially different amplitudes in diel vertical migration in response to fish. These different amplitudes would mean differences in the extent of diurnal temperature fluctuations among the clonal lineages.

Effect of soil temperature and moisture on population dynamics of phytonematodes infesting sugarcane

In India, phytonematodes are reported to cause about 10-40 %yield loss in sugarcane. In India, Uttar Pradesh is the major sugarcane growing state, contributing about 48% of the area and 40% of the production. The present study was undertaken to record biodiversity, to correlate the soil major edaphic factors (temperature & moisture). The study was also centered on to reveal the edaphic factors affecting sex ratio fluctuation of the dominant phytonematodes. Soil temperature, which changes constantly, is a major factor influencing nematode development. Temperature is an important environmental factor for organisms. Different organisms have their own optimal temperatures for normal activities and high and low temperature limits they can tolerate. Diurnal fluctuations in temperature vary in extent and depend upon soil type, texture, moisture, atmospheric conditions, latitude, elevation, season and soil cover. Cool climate species often develop slowly in winter and become more active when temperatures rise in spring season and in this season plant parasitic nematodes population decrease. Moisture plays an important role in the movement of the soil organism. The findings indicated that during winter period when moisture and humidity is high in soil environment conditions. Populations of plant parasitic nematodes were highest in this season.

Physical dormancy alleviation and soil seed bank establishment in Cassia roxburghii is determined by soil microsite characteristics

Seeds with an impermeable coat, i.e. physical dormancy (PY) persist in the soil for a long-time until suitable environmental cues break dormancy and germination is synchronized with the growing season. However, the dormancy loss of seeds at different microsites has not been well characterized. In this study, the effect of microsite affecting dormancy loss in Cassia roxburghii was studied by artificially burying the seeds in an open site and under canopy and exhuming the seeds at 6 month intervals for two years. The soil temperatures of the two microsites at seed vicinity were determined using a data-logger. The results showed that fresh intact seeds did not absorb water, but mechanically scarifying the seeds resulted in water absorption and germination at a wide range of temperatures both in light and darkness. Thus, the seeds of C. roxburghii have PY. Throughout the study period, impermeable seeds buried in the open site broke dormancy in significantly higher number compared with seeds buried under canopy cover (P < 0.05), presumably due to the temperature variation between microsites. Open sites recorded temperatures above 60 °C during summer with diurnal temperature fluctuations close to 20 °C, whereas under canopy cover temperature remained close to 40 °C during summer and much lower during other seasons. These results suggest that the ability of C. roxburghii seeds to break dormancy and establish soil seed banks is affected by the microsite variation.

Nesting Behavior of Captive Dalmatian Pelicans (Pelecanus crispus) in China

Dalmatian Pelicans (Pelecanus crispus, n = 3 breeding pairs) at the Shanghai Zoo, China, were used to study breeding behavior and nest conditions using automated telemetry from 21 February to 25 March 2011. Both sexes were found to participate in egg incubation, but females spent 341.7 ± 180.0 min incubating while males spent 378.3 ± 180.8 min incubating during daylight hours. Females turned the eggs at 51.5 ± 22.8-min intervals, whereas males turned the eggs at 70.0 ± 64.3-min intervals. However, the differences between the sexes were not significant. The time budget of the Dalmatian Pelicans indicated that the breeding birds saved energy by reducing locomotion and increasing the time spent resting during the breeding season. The average nest temperature during the study was 35.5 ± 0.8 °C (Range = 33.1–37.1 °C), and diurnal fluctuations in egg temperature were small (F = 0.570, P = 0.942). The average relative nest humidity was 55.7 ± 4.8% (Range = 39.8–66.9%), and changes during the day were not significant (F = 1.347, P = 0.148). Therefore, ambient conditions had little effect on nest conditions in this study, but the sample size was limited.

DECISION MAKING MODEL FOR PETROLEUM PRODUCT DENSITY DETERMINATION UNDER CONDITIONS OF UNCERTAINTY

Background When storing petroleum products in the reservoir tank, the following parameters change: 1. temperature - due to diurnal fluctuations in ambient temperature or oil heating during the cold period; 2. density - due to the light fractions evaporation; 3. level - due to evaporation, changes in temperature and density; 4. pressure - with increasing pressure in the gas space. The oil product density is determined by oil meter (aerometer). To this purpose, a petroleum product sample is taken from the container by a selective bucket, an oil meter is immersed in it and the density is determined on the upper scale and the temperature is determined on the lower scale. The oil product density can also be determined by calculation using the oil product temperature in the tank. The sought-for oil product density at a given temperature is determined through the oil product density at 20 0C and the temperature correction of the change in the oil product density with a temperature change of 1 0 C . This does not take into account the parameters of excessive pressure and the oil product level height. To create modern methods for determining the oil products density, mathematical models describing various processes in tanks must be developed and specified. At the same time, information accumulation process takes place; empirical and expert models should be supplemented and refined with the new experimental data accumulation obtained under model and experimental conditions. In this connection, the development of a model for determining the oil products density based on modern methods of artificial intelligence is an actual scientific and technical task. Aims and Objectives Creation of a base of fuzzy production rules for determining the oil products density in tanks. The choice of the characteristic function for the input linguistic variables fuzzification and the determination of the degree of veracity of all input conditions. Activation and accumulation of output linguistic variables, determination of the membership function for conclusions and the truth degree of the output linguistic variables. Determination, as a defuzzification result, of the oil product density in uncertainty conditions. Results A rules database was created for determining the oil products density. The fuzzification procedure was implemented under all the input linguistic variables conditions. The veracity conditions degree in the fuzzy products rules was determined. The activation procedure was carried out and all the values of the veracity degrees under the conclusions for each rule were found. As a defuzzification result, the quantitative output linguistic variables value was determined.

Circadian Rhythm Does Not Alter the Sweating Response to Exercise in Thermoneutral and Warm Ambient Temperatures

The present study sought to determine whether the diurnal fluctuation in core temperature alters the sweating response to exercise in thermoneutral (23°C) and warm (33°C) environments. Six healthy males exercised on a semi‐recumbent ergometer at a fixed evaporative requirement for heat balance (200W/m2) for 60 min at two different times of day and two ambient temperatures matched for absolute humidity (1.3 kPa); i) 0800h/23°C, ii) 0800h/33°C, iii) 1600h/23°C, and iv) 1600h/33°C. Esophageal temperature (Tes), mean body temperature (Tb), local sweat rate (LSR) measured at the arm and upper back, and whole body sweat loss (WBSL) were measured. Resting absolute Tes was higher at 1600h compared to 0800h at 23°C (0800h: 36.7±0.2°C, 1600h: 36.9±0.2°C; P=0.04) and 33°C (0800h: 36.6±0.2°C, 1600h 36.9±0.2°C; P=0.005). Similarly, end‐exercise (steady‐state) absolute Tes was higher at 1600h relative to 0800h at 23°C (0800h: 37.4±0.2°C, 1600h: 37.6±0.2°C; P=0.04) and 33°C (0800h: 37.0±0.2°C, 1600h 37.2±0.2°C; P=0.01). However the change in Tes was similar irrespective of the time of day at both 23°C (0800h: 0.7±0.1°C, 1600h: 0.7±0.2°C; P=0.37) and 33°C (0800h: 0.4±0.1°C, 1600h: 0.3±0.1°C; P=0.35). Further, mean steady‐state LSR of arm and back after 60 min of exercise was similar irrespective of time at both 23°C (0800h: 0.66±0.06 mg/cm2/min, 1600h: 0.65±0.13 mg/cm2/min; P=0.74) and 33°C (0800h: 0.62±0.11 mg/cm2/min, 1600 h: 0.58±0.11 mg/cm2/min, P=0.50). Likewise, WBSL at steady‐state (46 to 60 min) was similar between morning and afternoon trials at 23°C (0800h: 156±28 g, 1600h: 162±36 g; P=0.38) and 33°C (0800h: 147±29 g, 1600h: 158±34 g, P=0.55). While sweating commenced prior to exercise in 33°C, the onset threshold for sweating occurred at a higher Tb at 1600h compared to 800h at 23°C (0800h: 35.6±0.1°C, 1600h 35.9±0.2°C; P=0.03), however the change in Tb was similar at 23°C regardless of time of day (0800h: 0.14±0.07°C, 1600h 0.17±0.12°C; P=0.47). Lastly, sudomotor thermosensitivity (LSR‐Tb) was similar at both 23°C (0800h: 0.80±0.26 mg/cm2/min/°C, 1600h: 0.82±0.30 mg/cm2/min/°C; P=0.80) and 33°C (0800h: 0.81±0.18 mg/cm2/min, 1600h: 0.90±0.40 mg/cm2/min, P=0.87). Taken together, preliminary data suggests the difference in absolute core temperature (~0.3°C) associated with diurnal fluctuation does not alter the sweating response at a fixed evaporative requirement for heat balance in both thermoneutral and warm conditions.Support or Funding InformationN.R. was supported by an NSERC Postgraduate Scholarship‐Doctoral and a University of Ottawa Excellence Scholarship.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Evaluation of Efficacy and Compatibility of Herbicides with Fungicides in Durum Wheat (Triticum durum Desf.) under Different Environmental Conditions: Effects on Grain Yield and Gluten Content

In the present study, field experiments were conducted to determine the efficacy and compatibility of herbicides and fungicides in durum wheat under Mediterranean semi-arid conditions, in Central Greece. Our results indicate that the herbicide florasulam+2.4-D was safe and did not cause any injury when applied alone or with fungicides, while bromoxynil+2.4-D mixed with azoxystrobin or trifloxystrobin+prothioconazole caused injury symptoms on leaves. The injury symptoms were transient, and observed only at Velestino area, where low temperatures and broad diurnal temperature fluctuations were recorded during the pesticides application period. Regarding septoria leaf blotch control, good results showed strobilurin alone or in mixture with a triazole, regardless the herbicide that was added to the mixture. The results of this study showed that bromoxynil+2.4-D caused injury when mixed with fungicides and applied under cold temperatures, while one fungicide application at stem elongation provided adequate Septoria leaf blotch control.

Пространственное варьирование температуры корнеобитаемого слоя почв северной тайги Западной Сибири

Studies of soil heat regime are commonly confined to one vertical soil profile. Some studies on the basis of short-term temperature data series reported significant horizontal variation of topsoil horizons due to spatial variation in tree stand densities, plant cover and soil cover heterogeneity. Introduction of programmed automated temperature data loggers facilitated studies of horizontal heterogeneity in soil temperature, i.e. so called temperature fields with long temporal data series. However horizontal variation of soil temperature has not practically been studied in most Russian ecosystems, including those in the West Siberian northern taiga zone. The study of soil temperature regime was carried out in the environs of Noyabrsk (Yamalo-Nenetsky Autonomous Region, Russia) in the four key study sites: climax larch (Larix sibirica Ledeb.) and Scots pine (Pinus sylvestris L.) forests, and flat palsa mire (separately palsa and adjacent hollow). On each study site automated temperature data loggers were used in 5 replicated subsites to measure soil temperature with 0.5°С and record it every 4 hours, i.e. at 1, 5, 9, 13, 17 and 21 o’clock, daily. The loggers were placed at 10 cm soil depth in the root zone. The data from the meteorological station in Noyabrsk were also used in the study. The standard deviation of temperature values, recorded in a study site at one time point, was used as a measure of temperature variation. In all study sites the maximal temperature variation was observed at the beginning of the warm season. In both forest sites soil temperature began varying already after snow thawed, which was most likely due to the heterogeneity of vegetation cover and forest litter; in the pine site soil the heterogeneity of direct solar radiation as a result of the crown shadowing also contributed to temperature variation. The biggest soil temperature variation during this period was observed at the pine forest site, with difference between simultaneous replicated measurements reaching at certain time points as much as 9.6oС. In the larch study site the corresponding difference in June did not exceed 7-8oС. The minimal spatial variation of soil temperature in the root zone was observed in hollows of the flat palsa mire site, most likely due to the absence of the microrelief influence and high water saturation. The highest standard deviation values were observed during snow thawing at the beginning of May, when temperature difference between replicated measurements could be as high as 9.5oС. In June soil temperature variation decreased, staying low during the rest of the year. The palsa soil temperature at the flat palsa mire site and its variation in winter time showed strong response to changing air temperature. This winter variability was most likely due to unevenness of the snow cover thickness, resulting from the pronounced surface microrelief. During show thawing period the root zone temperature varied less, apparently because of even penetration and distribution of snowmelt water throughout the studied soil layer. Rapid soil warming resulted in increased temperature variability, which remained high during entire summer and the beginning of autumn, with differences between replicates being as high as 10.1oС. Summer variability of soil temperature at this site could be attributed to the permafrost layer, which in different microrelief positions is located at different depth as related to the root zone, thus exerting different influence on the temperature of the soil layers above. The most pronounced effect of diurnal fluctuations of root-zone temperature on its spatial variability was observed in pine forest during entire summer period, whereas on the palsa mire ecosystem it was observed at the beginning of summer during intensive thawing of the seasonally frozen layer.

Rock-art microbiome: influences on long term preservation of historic and culturally important engravings

The Burrup Peninsula in north-west Western Australia is home to one of the most substantial collections of rock engravings, or petroglyphs, in the world. These petroglyphs are carved through the dark coloured patina, commonly referred to as rock varnish, into the weathering rind of the local parent rock. Rock varnish is essentially a thin layer of manganese (Mn) and iron (Fe) oxides and hydroxides with embedded clay minerals, the formation of which is relatively poorly understood. It is generally considered to be a hostile environment for microorganisms due to extreme environmental conditions including low nutrient availability, lack of water, exposure to extreme ultraviolet radiation and intense seasonal and diurnal temperature fluctuations. However, despite these environmental extremes, microorganisms have been found on and in rock varnish and have been reported as playing a significant role in the formation of rock varnish. Given this, it is likely that any change in local environmental conditions will influence the types and activities of microorganisms found in and on rock varnish and associated rock art. This article focuses on the major influences on the microbiome of culturally important rock art in the Burrup Peninsula and the implications of any environmental change on the rock art itself.

Seed-dormancy depth is partitioned more strongly among habitats than among species in tropical ephemerals

Seed biology in the annual herbaceous flora of ecologically stressful, seasonally wet habitats remains largely unexplored. Temporal and spatial species turnover among these habitats is often high, yet little is known about how fine-scale habitat variation drives intraspecific variability in seed dormancy depth and seed germination requirements. The present study characterised seed dormancy and investigated the germination biology of six closely related herbaceous annual species of Byblis from northern Australia. We assessed variation in the response of seeds of all species to temperature cues, as well as light and the naturally occurring germination stimulants karrikinolide (KAR1) and ethylene. We also examined intraspecific variation in germination response and seed-dormancy depth for three widely distributed species with overlapping distribution occurring in habitats with differing soil thermal and hydrological conditions. Seed germination in all six species was significantly increased by exposure to either KAR1 or ethylene, with this effect being amplified in two species (B. filifolia and B. rorida) following a period of warm, dry after-ripening. Seed-dormancy depth and the germination response of seeds to both KAR1 and ethylene were partitioned more strongly among habitats than among species. Populations on shallow (&lt;20-cm soil depth) sandy soils produced less dormant seeds than did populations of the same species on deeper sandy soils (40+ cm) or on heavy cracking clays. The upper soil profile of shallow soil habitats was exposed to higher average temperatures, greater diurnal temperature fluctuation and greatly reduced moisture persistence compared with deeper soils. Fine-scale differences in the thermal and hydrological conditions of seasonally wet habitats appear to be strong drivers of dormancy depth in seeds of tropical Byblis. Widely distributed species exhibit high levels of plasticity in seed-dormancy depth and germination response among different habitats, with similar responses being observed for sympatric species. So as to fully understand species turnover in tropical ephemerals, future studies should examine phenotypic plasticity and the rate of local adaptation of seed traits in greater detail.

Impact of diurnal temperature fluctuations on larval settlement and growth of the reef coral &amp;lt;i&amp;gt;Pocillopora damicornis&amp;lt;/i&amp;gt;

Abstract. Diurnal fluctuations in seawater temperature are ubiquitous on tropical reef flats. However, the effects of such dynamic temperature variations on the early stages of corals are poorly understood. In this study, we investigated the responses of larvae and new recruits of Pocillopora damicornis to two constant temperature treatments (29 and 31 °C) and two diurnally fluctuating treatments (28–31 and 30–33 °C with daily means of 29 and 31 °C, respectively) simulating the 3 °C diel oscillations at 3 m depth on the Luhuitou fringing reef (Sanya, China). Results showed that the thermal stress on settlement at 31 °C was almost negated by the fluctuating treatment. Further, neither elevated temperature nor temperature fluctuations caused bleaching responses in recruits, while the maximum excitation pressure over photosystem II (PSII) was reduced under fluctuating temperatures. Although early growth and development were highly stimulated at 31 °C, oscillations of 3 °C had little effects on budding and lateral growth at either mean temperature. Nevertheless, daytime encounters with the maximum temperature of 33 °C in fluctuating 31 °C elicited a notable reduction in calcification compared to constant 31 °C. These results underscore the complexity of the effects caused by diel temperature fluctuations on early stages of corals and suggest that ecologically relevant temperature variability could buffer warming stress on larval settlement and dampen the positive effects of increased temperatures on coral growth.

Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko

Context. The camera OSIRIS on board Rosetta obtained high-resolution images of the nucleus of comet 67P/Churyumov-Gerasimenko (67P). Great parts of the nucleus surface are composed of fractured terrain. Aims. Fracture formation, evolution, and their potential relationship to physical processes that drive activity are not yet fully understood. Observed temperatures and gas production rates can be explained or interpreted with the presence of fractures by applying appropriate modelling methods. Methods. We followed a transient thermophysical model approach that includes radiative, conductive, and water-ice sublimation fluxes by considering a variety of heliocentric distances, illumination conditions, and thermophysical properties for a set of characteristic fracture geometries on the nucleus of 67P. We computed diurnal temperatures, heat fluxes, and outgassing behaviour in order to derive and distinguish the influence of the mentioned parameters on fractured terrain. Results. Our analysis confirms that fractures, as already indicated by former studies about concavities, deviate from flat-terrain topographies with equivalent properties, mostly through the effect of self-heating. Compared to flat terrain, illuminated cometary fractures are generally warmer, with smaller diurnal temperature fluctuations. Maximum sublimation rates reach higher peaks, and dust mantle quenching effects on sublimation rates are weaker. Consequently, the rough structure of the fractured terrain leads to significantly higher inferred surface thermal inertia values than for flat areas with identical physical properties, which might explain the range of measured thermal inertia on 67P. Conclusions. At 3.5 AU heliocentric distance, sublimation heat sinks in fractures converge to maximum values >50 W / m2 and trigger dust activity that can be related mainly to H2O. Fractures are likely to grow through the erosive interplay of alternating sublimation and thermal fatigue.

Ecological characterization of intertidal rockpools: Seasonal and diurnal monitoring of physico-chemical parameters

Diurnal and seasonal variations in temperature, salinity, oxygen concentration, carbonate chemistry parameters and nutrient concentration were monitored within mid-tidal rockpools on the north-western coast of Brittany, France. We also examined the importance of rockpool physical characteristics (e.g. shore height, surface, volume and depth) on the physico-chemical variability. Rockpool shore height and depth appeared as the main physical factors driving physico-chemical variations. Shallow upper shore rockpools exhibited the largest diurnal and seasonal fluctuations of temperature, oxygen concentration and pHT. Conversely, deeper and lower shore rockpools experienced weaker variations, excepted for salinity and nutrient concentrations. The physico-chemical environment was likely to be strongly influenced by rockpool community composition, especially in summer when rockpools were colonized by dense canopy-forming algae. During the day-time emersion, photosynthesis increased oxygen concentration and pHTbut decreased nutrient concentrations in upper shore rockpools. The increase in rockpool pHT provided an alkaline environment conducive to coralline algal calcification. Conversely, at night, upper shore rockpools presented a strong decrease in oxygen concentration and pHT due to the high community respiration, increasing the dissolution in coralline algae. Therefore, rockpools are characterized by complex interactions between physical and chemical parameters and biological processes. Rockpools appear as suitable environments to examine the physiological processes set up by species to face natural variability, especially in a context of climate change.

Warm northern river temperatures increase post‐exercise fatigue in an Arctic migratory salmonid but not in a temperate relative

Abstract The Arctic is warming at twice the global average rate; how native and non‐native anadromous fishes will respond remains largely unknown. Some native Arctic salmonids are already experiencing warm (&gt;21°C), physically challenging migratory river conditions and large diurnal temperature fluctuations (&gt;10°C). We conducted field and laboratory experiments to determine how these extreme conditions may affect the capacity for migration in Arctic and temperate salmonids. In adult migratory Arctic char, reflex impairment following a handling challenge increased with temperature, indicating more extensive fatigue. In Arctic char smolts, temperature did not affect initial critical swimming performance (Umax1), however, there was a threshold for repeat swimming performance (Umax2) near 20°C, above which recovery was impaired. Following a simulated diurnal warming scenario (11–21°C), Umax1 increased in rainbow trout and remained constant in Arctic char as in the field while Umax2 remained constant in rainbow trout it was drastically reduced in Arctic char. Furthermore, at warm temperatures, Arctic char were unable to recover to routine levels of oxygen uptake after exercise, while rainbow trout were. Warming also had more pronounced effects on blood composition and plasma glucose and lactate concentration in Arctic char than in rainbow trout. In general, rainbow trout, a temperate salmonid, had superior swimming performance, aerobic capacity, and warm tolerance than Arctic char, an Arctic salmonid. The present flow and temperature regimes in some Arctic rivers may restrict migration of native salmonids by limiting their ability to recover from fatiguing exercise. Non‐native, temperate salmonids are likely better suited to overcome these particular physical and thermal challenges. A plain language summary is available for this article.

Fungal proliferation and calcium accumulation in the orange slime of Cornus controversa

ABSTRACTA giant dogwood (Cornus controversa) was bleeding transparent sap that turned into gummy orange slime with a pungent odor on the bark in early April. The tree exudation originated from a branch wound that occurred during the most recent spring pruning. Scanning electron microscopy revealed the intact bark surface was irregularly undulating and covered with at least three types of epicuticular waxes: polygonal rodlets; polygonal tubules; and threads, whereas the dried orange plaques were covered with fungi, possibly the co-occurrence of yeast and filamentous forms. The yeast forms were ovoid, lemon- or club-shaped, and approximately 10 μm in length. Obviously constricted septa and clamp connections were rarely detected on the filamentous forms. No bacterial proliferation was detected on the orange slime. X-ray microanalysis revealed a steep increase in calcium concentration in the orange plaques compared with that in the intact bark. These results suggest that bark-dwelling dimorphic red yeasts may constitute one of the dominant microbial consortia of the orange slime of giant dogwood. Given the high amount of sugars and calcium in the sap, and tolerance to diurnal temperature fluctuations in early spring, the red yeasts may be specialist species that thrive under a limited range of environmental conditions.

Effects of the Relaxation of Upwelling‐Favorable Winds on the Diurnal and Semidiurnal Water Temperature Fluctuations in the Santa Barbara Channel, California

AbstractIn the Santa Barbara Channel, California, and around the Northern Channel Islands, water temperature fluctuations in the diurnal and semidiurnal frequency bands are intermittent, with amplitudes that vary on time scales of days to weeks. The cause of this intermittency is not well understood. We studied the effects of the barotropic tide, vertical stratification, propagation of coastal‐trapped waves, regional wind relaxations, and diurnal‐band winds on the intermittency of the temperature fluctuations during 1992–2015. We used temperature data from 43 moorings in 10–200 m water depth and wind data from two buoys and one land station. Subtidal‐frequency changes in vertical stratification explain 20–40% of the intermittency in diurnal and semidiurnal temperature fluctuations at time scales of days to weeks. Along the mainland north of Point Conception and at the Northern Channel Islands, the relaxation of upwelling‐favorable winds substantially increases vertical stratification, accounting for up to 55% of the subtidal‐frequency variability in stratification. As a result of the enhanced stratification, wind relaxations enhance the diurnal and semidiurnal temperature fluctuations at those sites, even though the diurnal‐band wind forcing decreases during wind relaxation. A linear model where the background stratification is advected vertically explains a substantial fraction of the temperature fluctuations at most sites. The increase of vertical stratification and subsequent increase in diurnal and semidiurnal temperature fluctuations during wind relaxation is a mechanism that can supply nutrients to the euphotic zone and kelp forests in the Channel in summer when upwelling is weak.

Thermal comfort in traditional buildings composed of local and modern construction materials

Abstract In recent years, there is a renewed interest towards the passive cooling features of ancient building architectures, which are cost effective, eco-friendly and best suited for the local climate. On the other hand, the modern construction materials, such as cement and steel, are highly durable. Thermal comfort of eight vernacular buildings that use modern construction materials to improve the structural durability was monitored in July 2014. The buildings are located in Hyderabad, India. They have many passive cooling features that include air cavities in the structures to reduce heat transfer, high thermal mass to reduce temperature fluctuation and induced ventilation to remove heat from the indoor. All the passive cooling features investigated were found to have an appreciable influence on the thermal comfort of the indoor space. The ventilated air gaps in the roof reduced the average temperature of the roof interior surface by 1.2 °C. The diurnal temperature fluctuation of the indoor air reduced by 0.9 °C in a building with a higher thermal mass compared to a building with thin walls and roof. All the eight buildings were found to be comfortable most of the time with a slight discomfort during late night and morning hours. The maximum CO 2 recorded was 550 ppm. This indicates that the buildings were adequately ventilated.

Temperature Variation under Continuous Light Restores Tomato Leaf Photosynthesis and Maintains the Diurnal Pattern in Stomatal Conductance.

The response of tomato plants (Solanum lycopersicum L. cv. Aromata) to continuous light (CL) in relation to photosynthesis, abscisic acid (ABA) and reactive oxygen species (ROS) was investigated to improve the understanding of the development and/or alleviation of CL-induced leaf injury in constant and diurnal temperature fluctuations with similar daily light integral and daily mean temperature. The plants were grown in three photoperiodic treatments for 15 days; One treatment with a 16/8 h light/dark period and a light/dark temperature of 27/17°C (Control), two CL treatments with 24 h photoperiods, one with a constant temperature of 24°C (CLCT) and the other one with variable temperature of 27/17°C for 16/8 ho, respectively (CLVT). A diurnal pattern of stomatal conductance (gs) and [ABA] was observed in the plants grown in the control and CLVT conditions, while the plants in CLCT conditions experienced a significant decrease in stomatal conductance aligned with an increase in ABA. The net photosynthesis (A) was significantly reduced in CLCT, aligned with a significant decrease in the maximum rate of Rubisco carboxylation (Vcmax), the maximum rate of electron transport (Jmax) and mesophyll diffusion conductance to CO2 (gm) in comparison to the control and CLVT. An increased production of H2O2 and O2•- linked with increased activities of antioxidative enzymes was seen in both CL treatments, but despite of this, leaf injuries were only observed in the CLCT treatment. The results suggest that the diurnal temperature fluctuations alleviated the CL injury symptoms, probably because the diurnal cycles of cellular mechanisms were maintained. The ROS were shown not to be directly involved in CL-induced leaf injury, since both ROS production and scavenging was highest in CLVT without leaf chlorotic symptoms.

Meltwater erosion process of frozen soil as affected by thawed depth under concentrated flow in high altitude and cold regions

AbstractChanges in thawed depth of frozen soil caused by diurnal and seasonal temperature fluctuations are commonly found in high altitude and latitude regions of the world. These changes significantly influence hydrologic and erosion processes. Experimental data are necessary to improve the understanding and modeling of the phenomenon. Laboratory experiments were conducted in Beijing to assess the impacts of thawed soil depth, slope gradient, and flow rate on soil erosion by concentrated meltwater flow over an underlying frozen soil layer. Soil samples from watershed were filled in flumes, saturated before being frozen. After the soil was completely frozen, flumes were taken out of storage to thaw the frozen soil from top to the designed depths. Meltwater flow was simulated using a tank filled with water and icecubes at approximately 0°C. The erosion experiments involved four thawed soil depths of 1, 2, 5, and 10 cm; three slope gradients of 5°, 10°, and 15°; and three flow rates of 1, 2, and 4 l/min; and seven rill lengths of 0.5, 1, 2, 3, 4, 5, and 6 m. Sediment‐laden water samples were collected at the lower end of the flume for determination of sediment concentration. The results showed that sediment concentration increased exponentially with rill length to approach a maximum value. The sediment concentrations were closely correlated with thawed soil depth, flow rate, and slope gradient. Shallower thawed depths delivered more sediments than deeper thawed depths. Slope gradient was the primary factor responsible for severe erosion. The effect of flow rate on sediment concentration which decreased with increasing slope gradient, was not as significant as that of slope gradient. Results from these experiments are useful for understanding the effect of thawed soil depth on erosion process in thawed soils subject to freezing and for estimating erosion model parameters. Copyright © 2017 John Wiley &amp; Sons, Ltd.