Variation In Tb Research Articles

A global heterothermic continuum in mammals

AbstractAimThe ability of endotherms to physiologically regulate body temperature (Tb) is presumed to be important in the adaptive radiation of birds and mammals. Recently, attention has shifted towards determining the extent and energetic significance ofTbvariation documented in an ever‐expanding list of species. Thus, we provide the first global synthesis of ecological and evolutionary correlates of variation in mammalianTb.LocationWorld‐wideMethodsWe conducted a phylogenetically informed analysis ofTbvariation using two complementary metrics, namelyThermoregulatoryScope (TS) andHeterothermyIndex (HI), that treatTbvariation as a continuous variable. We included morphological (e.g. body mass), ecological (e.g. food habits) and environmental (e.g. latitude) correlates in the analysis.ResultsAmong 560 mammal species included in theTSanalysis,Tbrelates most strongly to body mass (included in all models), season (relative parameter weight: 0.95), absolute latitude (0.80) and hoarding behavior (0.72), with small‐bodied, high latitude and non‐hoarding species expressing the mostTbvariation. Small‐bodied and high latitude species also express a greater range of thermoregulatory patterns than large‐bodied and low latitude species. Results were generally similar inHIanalysis, but in summer the extent of heterothermy decreases with latitude.Main conclusionsMammalian heterothermy is related to evolutionary history, climate conditions constraining minimumTb, resource conditions mediating energy supply for maintaining highTb, and latitudinal variation in the nature of seasonality. Our analysis further shows that traditional classification of mammals as hibernators, daily heterotherms or homeotherms is clouded or possibly misleading.

Evidence of maternal effects on temperature preference in side‐blotched lizards: implications for evolutionary response to climate change

Natural populations respond to selection pressures like increasing local temperatures in many ways, including plasticity and adaptation. To predict the response of ectotherms like lizards to local temperature increase, it is essential to estimate phenotypic variation in and determine the heritability of temperature-related traits like average field body temperature (Tb) and preferred temperature (Tp). We measured Tp of Uta stansburiana in a laboratory thermal gradient and assessed the contribution of sex, reproductive status and throat color genotype to phenotypic variation in Tb of adult lizards. Females had higher Tp than males. However, they temporarily preferred lower temperature when gravid than when nongravid. Using a nested half-sib design for genetic crosses in the laboratory, we estimated relative contributions of additive genetic variation and maternal effects to Tp of hatchlings. Our results show that maternal effects, but not additive genetic variation, influence Tp of hatchlings in U. stansburiana. Maternal Tp and the presence or absence of blue throat color alleles significantly influenced Tp of hatchlings. We discuss ecological and evolutionary consequences of these maternal effects in the context of rapid climate change and natural selection that we measure on progeny survival to maturity as a function of maternal Tp.

Waking to drink: rates of evaporative water loss determine arousal frequency in hibernating bats

Bats hibernate to cope with low ambient temperatures (T(a)) and low food availability during winter. However, hibernation is frequently interrupted by arousals, when bats increase body temperature (T(b)) and metabolic rate (MR) to normothermic levels. Arousals account for more than 85% of a bat's winter energy expenditure. This has been associated with variation in T(b), T(a) or both, leading to a single testable prediction, i.e. that torpor bout length (TBL) is negatively correlated with T(a) and T(b). T(a) and T(b) were both found to be correlated with TBL, but correlations alone cannot establish a causal link between arousal and T(b) or T(a). Because hydration state has also been implicated in arousals from hibernation, we hypothesized that water loss during hibernation creates the need in bats to arouse to drink. We measured TBL of bats (Pipistrellus kuhlii) at the same T(a) but under different conditions of humidity, and found an inverse relationship between TBL and total evaporative water loss, independent of metabolic rate, which directly supports the hypothesis that hydration state is a cue to arousal in bats.

Limits to sustained energy intake XX: body temperatures and physical activity of female mice during lactation

Lactating animals consume greater amounts of food than non-reproductive animals, but energy intake appears to be limited in late lactation. The heat dissipation limit theory suggests that the food intake of lactating mice is limited by the capacity of the mother to dissipate heat. Lactating mice should therefore have high body temperatures (Tb), and changes in energy intake during lactation should be reflected by variation in Tb. To investigate these predictions, 26 mice (Mus musculus) were monitored daily throughout lactation for food intake, body mass, litter size and litter mass. After weaning, 21 days postpartum, maternal food intake and body mass were monitored for another 10 days. Maternal activity and Tb were recorded every minute for 23 h a day using implanted transmitters (vital view). Energy intake increased to a plateau in late lactation (days 13-17). Daily gain in pup mass declined during this same period, suggesting a limit on maternal energy intake. Litter size and litter mass were positively related to maternal energy intake and body mass. Activity levels were constantly low, and mice with the largest increase in energy intake at peak lactation had the lowest activity. Tb rose sharply after parturition and the circadian rhythm became compressed within a small range. Tb during the light period increased considerably (1.1 ° C higher than in baseline), and lactating mice faced chronic hyperthermia, despite their activity levels in lactation being approximately halved. Average Tb increased in relation to energy intake as lactation progressed, but there was no relationship between litter size or litter mass and the mean Tb at peak lactation. These data are consistent with the heat dissipation limit theory, which suggests performance in late lactation is constrained by the ability to dissipate body heat.

Influences of Seasonality, Thermal Environment and Wind Intensity on the Thermal Ecology of Brazilian Sand Lizards In A Restinga Remnant

ABSTRACT. We evaluated the importance of thermal environment and wind intensity to the body temperature (Tb) and activity rates oiLiolaemus lutzae (a lizard species restricted to restingas in the state of Rio de Janeiro, southeastern Brazil), looking for seasonal changes. Field work was carried out in restinga of Praia Grande, municipality of Arraial do Cabo. In the dry season, lizards' activity started (07:00 h) and ended (18:00 h) latter compared to the rainy season (start: 06:00 h; end: 17:00 h). The body temperature of active L. lutzae individuals varied along day (lower in the start and in the end of their daily activity period), and achieved higher values in the rainy season. The lizards' body temperatures were related to substrate temperature and to air temperature in both seasons. Variations in Tb of L. lutzae reflect variations in microhabitat temperatures, the main environmental factors affecting its thermoregulation. The wind intensity affected the Tb of L. lutzae, promoting heat loss by indivi...

Thermal preferences of hatchling saltwater crocodiles (Crocodylus porosus) in response to time of day, social aggregation and feeding

Three month old hatchling Crocodylus porosus with data loggers in their stomachs were placed in thermal gradients, in isolation (N=16) and in groups of 4 (N=8 groups; 32 individuals). Mean Tb and variation in Tb (SD) was not different whether individual crocodiles in isolation were fasted or fed, or if individuals were housed in isolation (I) or in groups (G). However, individuals in isolation (N=16) maintained slightly lower Tbs than those in groups (N=32) during the early morning (06:00–11:00h). The overall mean Tb recorded for fasted individuals in the isolated and group treatments (N=48) was 30.9±2.3°C SD, with 50% of Tbs (Tset) between 29.4°C and 32.6°C, and a voluntary maximum and minimum of 37.6°C and 23.2°C respectively. During the day (11:00–17:00h), individuals in isolation and in groups selected the warmer parts of the gradient on land, where they moved little. Outside of this quiescent period (QP), activity levels were much higher and they used the water more. There was a strong diurnal cycle for fasted individuals in isolation and in groups, with Tb during the QP (31.9±2.09°C; N=48) significantly higher than during the non-quiescent period (NQP: 30.6±2.31°C). Thermal variation (SD) in Tb was relatively stable throughout the day, with the highest variation at around dusk and early evening (18:00–20:00h), which coincided with a period of highest activity. The diurnal activity cycle appears innate, and may reflect the need to engage in feeding activity at the water's edge in the early evening, despite ambient temperatures being cooler, with reduced activity and basking during the day. If so, preferred Tb may be more accurately defined as the mean Tb during the QP rather than the NQP. Implications for the thermal environment best suited for captive C. porosus hatchlings are discussed.

First evaluation of the simultaneous SMOS and ELBARA-II observations in the Mediterranean region

The SMOS (Soil Moisture and Ocean Salinity) mission was launched on November 2, 2009. Over the land surfaces, simultaneous retrievals of surface soil moisture (SM) and vegetation characteristics made from the multi-angular and dual polarization SMOS observations are now available from Level-2 (L2) products delivered by the European Space Agency (ESA). Therefore, first analyses evaluating the SMOS observations in terms of Brightness Temperatures (TB) and L2 products (SM and vegetation optical depth TAU) can be carried out over several calibration/validation (cal/val) sites selected by ESA over all continents. This study is based on SMOS observations and in situ measurements carried out in 2010 over one of the main SMOS cal/val sites in Europe: the VAS (Valencia Anchor Station) site in the region of Utiel–Requena, close to Valencia, Spain. The main vegetation types in the region are vineyards, orchards and natural Mediterranean vegetation. The SMOS observations were analyzed in conjunction with those carried out by the L-band ELBARA-II radiometer over a vineyard which is considered as representative of the main land use of the VAS site. Time series of TB and retrievals of SM and TAU based on both the SMOS (L2 products) and the ELBARA-II observations were compared and evaluated against in situ measurements. A good agreement was found between the time variations in TB and in the retrieved SM values computed over the site from the SMOS and ELBARA-II observations (the determination coefficient R2 was >0.88 for the TB values and R2>0.64 for the retrieved SM values). However, it was found that the SMOS L2 SM products underestimated the SM values retrieved from ELBARA-II by ~0.2m3/m3. It is likely this offset can be partially explained by differences between the observed scenes: while the ELBARA-II footprint includes a single vineyard, the heterogeneous SMOS footprint includes not only a large number of vineyards but also a natural Mediterranean vegetation with persistent leaves overlaying rocky soils. The time variations in TAU retrieved from the ELBARA-II observations were found to be closely related to those of the NDVI (Normalized Difference Vegetation Index) vegetation index obtained from MODIS (Moderate Resolution Imaging Spectroradiometer) (R2=0.61) and revealed the vegetation cycle over the year. Conversely, the time variations in the SMOS Level-2 TAU product did not reveal any trends in relation to the vegetation development over the site.

Variation in body temperature is related to ambient temperature but not experimental manipulation of insulation in two small endotherms with different thermoregulatory patterns

AbstractMaintaining a high and constant body temperature (T b) is thought to enhance performance in endotherms, but such a thermoregulatory pattern is energetically expensive. Thus, some variation in T b is probably universal among endotherms, and several recent attempts have been made to generalize the factors that should cause this variation. Two factors that may be closely tied to the thermoregulatory pattern expressed are the cost of thermoregulation and food availability. To test these predictions, we measured T b of eastern rock elephant shrews (Elephantulus myurus; a traditionally defined heterotherm) and Namaqua rock mice (Micaelamys namaquensis; a homeotherm) in the field and under semi‐natural conditions after experimentally reducing insulation by shaving a patch of dorsal fur. After accounting for ambient temperature (T a), there was no significant difference in the level of variation in T b between shaven and unshaven elephant shrews. In rock mice, the increase in heat loss paradoxically led to decreased variation in T b in the field, but no effect was evident in captivity. Furthermore, as predicted, both species displayed significantly less variation in T b under semi‐natural conditions when given food ad libitum and predation risk involved with obtaining that food was low. Our results show that small mammals, both homeothermic and heterothermic, are capable of altering their thermoregulatory patterns in response to ecological conditions (e.g. rapid changes in food availability). However, increasing the cost of thermoregulation, at least as it was done in this experiment, does not appear to affect the expression of T b as strongly as does T a.

Body temperature variation of South African antelopes in two climatically contrasting environments

To understand the adaptive capacity of a species in response to rapid habitat destruction and climate change, we investigated variation in body temperature (Tb) of three species of antelope, namely eland, blue wildebeest and impala, using abdominally-implanted temperature data loggers. The study was conducted at two climatically contrasting environments in South Africa, one with a less seasonal and mild winter (Mapungubwe National Park) and the other with a more seasonal, long and cold winter (Asante Sana Game Reserve). Since the habitat with long and cold winters would be suboptimal for these African antelopes, which evolved in less seasonal and hot environments, antelopes in Asante Sana were expected to exhibit a larger amplitude in Tb and a lower minimum body temperature (MinTb) during winter to reduce Tb and the ambient temperature (Tb−Ta) gradient to save energy. In both eland and impala, 24-h body temperature amplitude did not differ between the study sites, regardless of season. Conversely, wildebeest in Mapungubwe showed a higher variability in the 24-h amplitude of body temperature and also a lower MinTb during winter and spring than the wildebeest in Asante Sana. This variation in Tb among Mapungubwe wildebeest was influenced by both the amplitude of ambient temperature (positive) and cumulative rainfall (negative), which was not the case for wildebeest in Asante Sana. We propose that the low MinTb of wildebeest in Mapungubwe was the result of nutritional stress during winter and spring; an evident response even during a year of average rainfall. Therefore, these wildebeest apparently live in a physiologically stressful environment. With the predicted increase in the frequency and intensity of drought periods in southern Africa, wildebeest and other grazers, will likely experience greater nutritional stress in the future.

Temporal patterns of thermal emission directionality of crop canopies

[1] Many field experiments have observed significant temporal variations of thermal infrared (TIR) emission directionality, making it necessary to explain this phenomenon quantitatively to exploit potential applications of the directional remotely sensed TIR observation. The main objective of this paper is to determine when and how the significant directional effect appears. Two models, TRGM and Cupid, are linked to simulate the temporal variations of directional brightness temperature TB(θ) of crop canopies, including winter wheat and summer corn. Two indicators are defined: (1) ΔTB,AVG representing the mean difference between nadir TB(0) and off-nadir TB(55) and (2) ΔTB,STD representing the standard deviation of TB(55) for different view azimuth angles. Simulation results show that the highest ΔTB,AVG of up to 4°C appears mostly at midday (1200–1300 LT), while the lowest ΔTB,AVG appears mostly in the early morning (0700–0800 LT) or late afternoon (1700–1800 LT). The ΔTB,STD is about one third of ΔTB,AVG and should not be neglected given its considerable value at around 1400 LT. This trend has been proven through field measurements at both wheat and corn sites. The major factors affecting the trend are also identified using sensitivity analysis. Among the major factors, soil water content, LAI, and solar radiation are the three most significant factors, whereas the wind speed and air temperature have a larger effect on ΔTB,AVG than air humidity. It is interesting that ΔTB,AVG reaches a maximum value when the LAI is around 0.8. Further analysis shows that ΔTB,AVG is related to soil surface net radiation, which will be useful in net radiation estimation.

A New Comparative Metric for Estimating Heterothermy in Endotherms

A major focus in the study of endothermic thermoregulation has been the description of thermoregulatory patterns used by various species and/or populations. Compared with ectotherms, relatively few attempts have been made to study the thermoregulation of endotherms in an adaptive framework. We believe that one of the main factors limiting this area of research has been the lack of an appropriate metric to directly compare body temperature (T(b)) variation across all endothermic species. Thus, we present a simple comparative metric, the heterothermy index (HI), to quantify the expression of heterothermy by endotherms during a given time frame. Key advantages of HI are that (1) it represents a new analytical technique that has different strengths than the metrics commonly used to describe variation in T(b), (2) it allows for evaluation of nonenergetic costs and benefits that affect the expression of heterothermy, and (3) it has the potential to unify research on homeotherms and heterotherms through quantitative comparative analyses that examine the entire continuum of thermoregulatory patterns. In short, we suggest that our metric provides a means to overcome one of the hurdles presently slowing the advancement of research on endothermic thermoregulation beyond the simple description of thermoregulatory patterns.

Snow scattering signals in ground‐based passive microwave radiometer measurements

This paper investigates the influence of snow microphysical parameters on the enhancement of ground‐based passive microwave brightness temperature (TB) measurements. In addition to multispectral passive microwave observations between 20 and 150 GHz, a 35 GHz cloud radar and a 2‐D video disdrometer for in situ measurements of snowfall were deployed as part of the “towards an optimal estimation‐based snowfall characterization algorithm” campaign in the winter season of 2008–2009 at an Alpine environment located at 2650 m mean sea level. These observations are combined with nearby radiosonde ascents and surface standard meteorological measurements to reconstruct the atmospheric state (i.e., fields of temperature, humidity, snow, and liquid water contents) and are subsequently used as input for a microwave radiative transfer (RT) model. We investigate the sensitivity of the missing information about snow shape and snow particle size distribution (SSD) on the microwave TB measurements using the disdrometer data as a rough constraint. For an extended case study, we found that TBs at 90 and 150 GHz are significantly enhanced because of scattering of surface radiation at snow crystals and that this enhancement is clearly correlated with the radar derived snow water path (SWP < 0.2 kg m−2). RT simulations highlight the strong influence of the vertical distribution of cloud liquid water (liquid water path LWP < 0.1 kg m−2) on the TB, which in extreme cases, can fully obscure the snow scattering signal. TB variations of the same magnitude can also be caused by typical variations in SSD parameters and particle shape similar to results obtained by space‐borne studies. Ground‐based stations with their infrastructural capabilities in combining active and passive microwave observations have the potential to disentangle the influences of different snow shape, SSD, and SWP in snow retrievals, thus supporting current and future satellite missions.

Body Temperature Variation During Nesting Forays in Midland Painted Turtles, Chrysemys picta marginata, in Michigan

During terrestrial nesting forays, north-temperate freshwater turtles may experience a range of environmental temperatures that could cause overheating or constrain movement if temperatures are too high or low. Yet, we have very little understanding of how body temperature (Tb) varies in freshwater turtles during various nesting foray activities. We studied Tb variation in Chrysemys picta marginata from a small marsh in northern Michigan, 2003–2004. Three individuals left the marsh, nested, and returned to the marsh in a single day; whereas, 5 others remained on land for up to 3 days, mostly immobile under leaf litter. While on land, Tb of turtles and air temperature (Ta) showed parallel, diel oscillations. Mean Tb of mobile turtles exceeded prevailing Ta values but was similar to Tb recorded for those same individuals while aquatic 1 week before and after the nesting foray. Therefore, active nesting turtles on forays may have maintained suitable Tb values by use of sun or shade. During the nesting process, Tb decreased from 23.5°C to 20.0°C. Turtles that entered terrestrial refugia after evening nesting had Tb values similar to those while mobile, often at times when the evening sky illuminated the nesting areas. Therefore, low light levels, which could limit navigation, and Tb values, which could impede movements, did not directly cause turtles to seek terrestrial refugia after nesting. Instead, we suggest that impending low environmental temperatures, waning light levels that would eventually impair navigation abilities, and, ultimately, the risk of predation while returning to the marsh caused turtles to seek terrestrial refugia.

Orexin neurons are necessary for the circadian control of REM sleep.

The orexin-producing neurons are hypothesized to be essential for the circadian control of sleep/wake behavior, but it remains unknown whether these rhythms are mediated by the orexin peptides or by other signaling molecules released by these neurons such as glutamate or dynorphin. To determine the roles of these neurotransmitters, we examined the circadian rhythms of sleep/wake behavior in mice lacking the orexin neurons (ataxin-3 [Atx] mice) and mice lacking just the orexin neuropeptides (orexin knockout [KO] mice). We instrumented mice for recordings of sleep-wake behavior, locomotor activity (LMA), and body temperature (Tb) and recorded behavior after 6 days in constant darkness. The amplitude of the rapid eye movement (REM) sleep rhythm was substantially reduced in Atx mice but preserved in orexin KO mice. This blunted rhythm in Atx mice was caused by an increase in the amount of REM sleep during the subjective night (active period) due to more transitions into REM sleep and longer REM sleep episodes. In contrast, the circadian variations of Tb, LMA, Wake, non-REM sleep, and cataplexy were normal, suggesting that the circadian timekeeping system and other output pathways are intact in both Atx and KO mice. These results indicate that the orexin neurons are necessary for the circadian suppression of REM sleep. Blunting of the REM sleep rhythm in Atx mice but not in orexin KO mice suggests that other signaling molecules such as dynorphin or glutamate may act in concert with orexins to suppress REM sleep during the active period.

Timber Rattlesnakes (Crotalus horridus) Exhibit Elevated and Less Variable Body Temperatures during Pregnancy

Body temperatures of ectotherms critically affect their bioenergetics, and thus have consequences for multiple aspects of population ecology, including recruitment, survival, and population viability. We compared body temperatures and movement between gravid and non-gravid female Timber Rattlesnakes (Crotalus horridus) inhabiting northwestern Arkansas using radiotelemetry. Body temperatures (n = 839) were recorded from six gravid and five non-gravid adult female rattlesnakes using temperature-sensitive radiotelemetry. Mean Tbs were calculated for each hour of the day from 15 July–22 August 2002 and used to construct a representative 24-hour body temperature profile. Gravid females had significantly higher mean Tbs in the early morning and again for most hours in the late afternoon and first half of scotophase. Overall snake Tbs were higher during the day and lower at night. Moreover, gravid females exhibited lower variation in Tb during late afternoon than did non-gravid females. Mean area used (± SD) by gravid females (0.4 ± 0.4 ha) was significantly less than that of non-gravid females (2.4 ± 1.8 ha), and daily movement (18.2 ± 6.1 m/day) and overall distance traveled by non-gravid females (827.4 ± 234.4 m) was over twice that of gravid females (8.8 ± 4.6 m/day; 384.0 ± 236.1 m). Understanding the thermal ecology of reproduction in this viviparous capital breeder provides valuable information for habitat management and species conservation.

Luminescence properties of ZnGa2O4 and ZnAl2O4 spinels doped with Eu3+ and Tb3+ ions

AbstractSpinel‐type ZnGa2O4 and ZnAl2O4 powders doped with Eu3+ and Tb3+ ions, including dual doping, have been prepared by solid phase reactions and by deposition from chemical solutions. XRD analysis demonstrates the high quality of spinel grains constituting the powder. The luminescence shows that the rare earth ions are incorporated in the defect regions at the grain boundaries. The emission spectra of the samples with europium are characterized by an intense emission in red region due to the 5D0 → 7F1,2 transitions of Eu3+ ions, whereas in the case of terbium the highest intensity corresponds to the green emission due to the 5D4 → 7F5 transitions of Tb3+ ions. The possibility to change the color of the emission from green to red by the variation of Tb and Eu doping concentration is demonstrated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of Sex and Microhabitat Use on Diel Body Temperature Variation in Midland Painted Turtles (Chrysemys picta marginata)

Sources of body temperature (Tb) variation in freshwater turtles are known for very few species. Using surgically implanted, temperature-sensitive radiotransmitters in Midland Painted Turtles (Chrysemys picta marginata), we assessed Tb variation in relation to sex, microhabitat use, weather conditions, and water temperature (Tw) in a marsh system in northern Michigan. Diel Tb cycling occurred regardless of weather conditions and included monotonic declines during late evening and early morning hours, a late morning warming phase, a mid-day spike, and afternoon oscillations. Males maintained significantly higher mean Tb than females during the 0000–0600 h time period but not at other times during the day. During the nesting season and during all summer and fall months, sex did not explain any variation in mean daily Tb, but males had significantly lower mean daily Tb variability (CV Tb) than females. Mean daily Tb and CV Tb were significantly lower on overcast days than on sunny days, and females maintained significantly greater mean daily Tb than males on cloudy days. Habitat use affected mean daily Tb, where turtles that used the open-water microhabitat had higher and less variable Tb than turtles that used the edge microhabitat for at least part of the day. Overall, mean total daily distance moved (TDDM) was greater in males than in females although the effect was weak. Mean TDDM was significantly greater on sunny days than on cloudy days, and greater in turtles that used open-water microhabitats than in turtles that used only the edge microhabitat. Mean daily Tb began to decline in October, but mean TDDM, and therefore activity, did not occur until November. Daily movements ceased when Tw fell to 2.0–3.9°C in December and January.

Deriving Sea Surface Salinity and Density Variations From Satellite and Aircraft Microwave Radiometer Measurements: Application to Coastal Plumes Using STARRS

Using brightness temperature <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tb</i> measurements from L-band airborne microwave radiometers, with independent sea surface temperature (SST) observations, sea surface salinity (SSS) can be remotely determined with errors of about 1 psu in temperate regions. Nonlinearities in the relationship between <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tb</i> , SSS, and SST produce variations in the sensitivity of salinity <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> to variations in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tb</i> and SST. Despite significant efforts devoted to SSS remote sensing retrieval algorithms, little consideration has been given to deriving density <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> from remotely sensed SSS and SST. Density is related to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> through the equation of state. It affects the ocean's static stability and its dynamical response to forcings. By chaining together two empirical relationships (flat-sea emissivity and equation of state) to form an inversion algorithm for sea surface density (SSD) in terms of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tb</i> and SST, we develop a simple L-band SSD retrieval algorithm. We use this to investigate the sensitivity of SSD retrievals to observed <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tb</i> and SST and infer errors in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> for typical sampling configurations of the airborne Salinity, Temperature, And Roughness Remote Scanner (STARRS) and satellite-borne Soil Moisture and Ocean Salinity (SMOS) and Aquarius radiometers. We then derive <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> from observations of river plumes obtained using STARRS and demonstrate several oceanographic applications: the observations are used to study variations in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> effects on <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> in the Mississippi plume, and the across-shelf density gradient is used to infer surface geostrophic shear and subsurface geostrophic current in the Plata plume. Future basin-scale applications of SSD retrievals from satellite-borne microwave radiometers such as SMOS and Aquarius are anticipated.

Nickel-silica nanocomposite: Variation of the blocking temperature with magnetic field and measuring frequency

The variations of the blocking temperature TB with measuring frequency fm and applied field H are reported for Ni nanoparticles (NPs) embedded in SiO2 matrix with the nominal composition Ni∕SiO2 (15∕85). Transmission electron microscopy of the sol-gel prepared NPs yielded a log-normal distribution with diameter D=3.8(0.2)nm whereas x-ray diffraction data yielded D≃3.3nm. The TB versus fm variation for fm=0.1–1000Hz fits the equation TB=Ta∕ln(f0∕fm) with f0=2.6×109Hz and Ta=270K whereas TB versus H data follows the equation TB(H)=33(1−H∕H0)m with H0=3200Oe and m=2(3∕2) for lower (higher) H. These results are compared with the predictions of the Néel-Brown model of magnetic relaxation in noninteracting NPs.

A Feasibility Study of Cloud Base Height Remote Sensing by Simulating Ground‐Based Thermal Infrared Brightness Temperature Measurements

AbstractThis paper attempts to study the feasibility of cloud base height (cloud base height–CBH) remote sensing by ground‐based sky thermal infrared brightness temperature (thermal infrared brightness temperature‐Tb) observation and the quantitative effects of aerosol layer on it. Using MODTRAN4.0 model simulation, the variations of Tb with zenith angle of observation for different types of aerosol and different visibilities (visibility‐VIS) under clear and cloudy sky conditions were systematically investigated. Based on the simulated results, the statistic equations for clear and cloudy sky Tb calculation were obtained respectively, and then a preliminary method of CBH estimation was developed. The results of simulation and preliminary experiments show that for low and middle clouds, the sky Tb observed on the ground is very sensitive to the change of CBH, therefore it can be used to estimate CBH. The influence of aerosol (VIS and aerosol types) above the ground on the sky Tb cannot be neglected, it must be corrected. Because the regularity of aerosol's influence on Tb at different zenith angles is fairly clear, it can be corrected well.