Late Morning Hours Research Articles

Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus).

Herbivores of temperate and arctic zones are confronted during winter with harsh climatic conditions and nutritional shortness. It is still not fully understood how large ungulates cope with this twofold challenge. We found that red deer, similar to many other northern ungulates, show large seasonal fluctuations of metabolic rate, as indicated by heart rate, with a 60% reduction at the winter nadir compared with the summer peak. A previously unknown mechanism of energy conservation, i.e., nocturnal hypometabolism associated with peripheral cooling, contributed significantly to lower energy expenditure during winter. Predominantly during late winter night and early morning hours, subcutaneous temperature could decrease substantially. Importantly, during these episodes of peripheral cooling, heart rate was not maintained at a constant level, as to be expected from classical models of thermoregulation in the thermoneutral zone, but continuously decreased with subcutaneous temperature, both during locomotor activity and at rest. This indicates that the circadian minimum of basal metabolic rate and of the set-point of body temperature regulation varied and dropped to particularly low levels during late winter. Our results suggest, together with accumulating evidence from other species, that reducing endogenous heat production is not restricted to hibernators and daily heterotherms but is a common and well-regulated physiological response of endothermic organisms to energetically challenging situations. Whether the temperature of all tissues is affected, or the body shell only, may simply be a result of the duration and degree of hypometabolism and its interaction with body size-dependent heat loss.

Movement Patterns of Adult Laughing GullsLarus atricillaDuring the Nesting Season

The foraging behavior of birds is often influenced by the development and dietary needs of their young. Laughing Gulls in New Jersey, USA, nest in highly productive salt marshes but adults commonly forage at inland sites when they have young in the nest. I monitored movements of individual Laughing Gulls using color-marking, banding and radio-telemetry combined with land-based and aerial surveys. I found that breeding adults were highly mobile and commonly flew inland to forage. Color-marked individuals were observed a mean of 16.6 km and a median of 11.0 km from the colony. Radio-tagged birds were located as far as 40 km inland. Laughing Gulls showed foraging site tenacity both within a given year and from year to year. Radio-tagged adults made as many as 11 foraging trips from the colony per day during both diurnal and nocturnal periods. Activity at the colony peaked during late evening and morning hours. Furthermore, Laughing Gull movement patterns changed with progression of the nesting season. Gulls spent more time at the colony while incubating than during either the chick rearing or fledging periods.

Gyrfalcon Feeding Behaviour during the Nestling Period in Central West Greenland

We studied gyrfalcon (Falco rusticolus) food delivery and feeding behavior during the nestling period in central West Greenland during the 2000 and 2001 field seasons. We used time-lapse video cameras installed at three nests to record 2677.25 hours of nestling video. Ptarmigan delivered to nests were usually plucked prior to delivery and included the breast and superior thoracic vertebrae. Arctic hare leverets were rarely plucked and often delivered in parts. The most commonly delivered leveret part was the hind legs attached to the lower back. Passerines were rarely plucked and usually delivered whole. After feeding the young, adults removed 20.9% of prey items from the nest, which included items both with and without obvious muscle still attached. Prey delivery rates were similar among nests and increased as nestlings aged. Prey delivery frequency peaked in the morning and evening, with a distinct lull in the late evening and early morning hours. Male and female adults delivered a similar number of prey, though males typically delivered smaller prey than females. Gyrfalcons cached and re-delivered at least 9.1% of all items delivered, and one item was cached and retrieved three times.

Peroxyacetyl nitrate and peroxypropionyl nitrate in Porto Alegre, Brazil

For 41 days between 25 May 1996 and 27 March 1997, peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) have been measured by electron capture gas chromatography at Santa Rita near Porto Alegre, RS, Brazil, where light-duty vehicles used either ethanol or a gasoline–MTBE blend. Daily maximum concentrations ranged from 0.19 to 6.67 ppb for PAN and 0.06 to 0.72 ppb for PPN. Linear regression of maximum PPN vs. maximum PAN yielded a slope of 0.105±0.004 ( R 2=0.974). Diurnal variations of ambient PAN often followed those of ozone with respect to time of day but not with respect to amplitude. This was reflected in the large relative standard deviations associated with the study-averaged PAN/ozone concentration ratio, 0.037±0.105 (ppb/ppb, n=789) and the maximum PAN/maximum ozone concentration ratio, 0.028±0.015 (ppb/ppb, range 0.005–0.078, n=41). On several days PAN accounted for large fractions of the total ambient NO x in the late morning and afternoon hours, e.g., PAN/NO x ⩽0.58 and PAN/(NO x –NO) ⩽0.76 on 27 March 1997. The amount of PAN lost by thermal decomposition (TPAN) was comparable in magnitude to that present in ambient air. The ratios TPAN/(PAN+TPAN) were up to 0.53, 0.67 and 0.64 during the warm afternoons of 25, 26 and 27 March 1997, respectively. The highest calculated value of TPAN was 5.6 ppb on 27 March 1997. On that day the 24 h-averaged value of TPAN (1.01 ppb) was nearly the same as that of PAN (1.09 ppb). Using computer kinetic modeling (SAPRC 97 chemical mechanism) and sensitivity analysis of VOC incremental reactivity, we ranked VOC present in Porto Alegre ambient air for their importance as precursors to PAN and to PPN. Using as input data the averages of VOC concentrations measured in downtown Porto Alegre during the ca. 1 yr period March 1996–April 1997, we calculated that the most important precursors to PAN and PPN were the SAPRC 97 model species ARO2 (which includes the aromatics xylenes, trimethylbenzenes, ethyltoluenes, etc.), which accounted for ca. 17% of the total PAN and total PPN formation potentials. Overall, the results indicate a major role for aromatics and alkenes and a minor role for acetaldehyde and ethanol as precursors to peroxyacyl nitrates in the Porto Alegre urban area.

Intentional childhood injuries in Greece 1996-97 - Data from a population-based Emergency Department Injury Surveillance System (EDISS)

It has been gradually recognized that intentional injuries among children represent a largely hidden problem in modern societies. With the exception of mortality, population-based data from Greece have not been previously reported. To assess the magnitude and the characteristics of intentional injuries among children aged 0-14 years old, data from the population-based Emergency Department Injury Surveillance System (EDISS) database during the period 1996-97 were used. EDISS relies on personal interviews with children and their escorts who contact the emergency departments of three hospitals. Two of these hospitals are district hospitals of the county of Magnesia and the island of Corfu, whereas the other is a university children's hospital that covers the Greater Athens area on alternative days. Among 46.807 children recorded in EDISS, 108 injuries (0.23%) were attributed to acts of violence. Among the 108 intentional injuries, only 11 were caused by firearms or other weapons and only 4 concerned infants. In comparison to unintentional home and leisure injuries, intentional childhood injuries increase significantly with age and they are more common among migrant children. They occur more frequently during late night and early morning hours, they are more serious, and they are more often multiple and concentrated on the head. In Greece. a problem of violence directed against children does exist. The actual magnitude of this problem is difficult to estimate, but its size appears to be smaller in comparison with that reported in other populations.

Switching the light off: A break in photosynthesis and sap flow of forest trees under total solar eclipse

In mature trees of Picea abies, Fagus sylvatica and Quercus robur, photosynthesis and transpiration were assessed in response to the total solar eclipse that occurred in Central Europe during the late morning hours of August 11, 1999, a day with changing cloudiness. Measurements were conducted at three forest sites located in the totality zone and the 99% area of the eclipse within a radius of about 100 km around the city of Munich (southern Germany). The eclipse lasting 164 minutes lowered the photosynthetic photon flux density (PPFD) to about 1 μmol m -2 s -1 during the 2-minute totality period, when the sky was clear. During totality, photosynthesis was reduced to an extent that allowed CO 2 release to dominate the gas exchange of leaves. Effects on transpiration were less pronounced as the totality was apparently too short to induce distinct stomatal closure in response to low PPFD. Transpiration was strongly reduced, however, by increased air humidity and wet leaf surfaces during sporadic rain showers which preceded or succeeded the eclipse during the same day, whereas low PPFD through intermittent cloudiness during rain only moderately reduced photosynthesis. Although transpiration was lowered to a minor extent only by the eclipse, the latter affected the water transport through the whole tree, as reflected in a decline in the sap flow rate through the basal stem part with a time delay depending on the species. Nevertheless, trees responded in a synchronous way, regardless of the site, species or the percent degree of the eclipse.

24h VARIATION IN THE EXPRESSION OF THE mt1 MELATONIN RECEPTOR SUBTYPE IN CORONARY ARTERIES DERIVED FROM PATIENTS WITH CORONARY HEART DISEASE

Previous studies presented evidence for impaired nocturnal secretion and synthesis of melatonin in patients with coronary heart disease (CHD). This study aimed to investigate whether the melatonin receptor subtype mt1 is differentially expressed in coronary arteries derived from patients with CHD (n = 9) compared to patients with dilative cardiomyopathy (CMP; n = 10) who served as controls. Expression of the mt1 receptor was studied in sections of isolated coronary arteries by a reverse transcriptase–polymerase chain reaction (RT-PCR) and a Western immunoblot technique. In addition, the data from the Western blotting of 15 patients were interpolated against the exact time of aortic clamp to study the 24h expression of the mt1 receptor. The analyses of the results from both methods indicated the presence of the mt1 receptor in all of the individuals. No statistically significant difference was observed in the receptor expression between patients with CHD and those with CMP (in arbitrary units: 3.39 ± 3.08 versus 3.91 ± 2.78). Expression of the melatonin receptor in the coronary arteries of the whole patient group presented a 24h variation, with the lowest values detectable after 02:00 up to the late morning hours and a progressive increase beginning after 13:00 until 00:00 (mesor = 3.66, amplitude = 3.23, acrophase = 20.45, P =. 0003). When studying the 24h variation in patients with CHD and CMP separately, a nearly similar circadian course was observed. In conclusion, we demonstrated for the first time a 24h variation of a melatonin receptor subtype in human vessels. Furthermore, in relation to our results, we suggest that the expression of the mt1 melatonin receptor in the coronary arteries is probably not impaired in patients with CHD. (Chronobiology International, 18(6), 973–985, 2001)

Effect of headlocks on milk production and feed intake of dairy cattle (2001)

Cows previously trained with headlocks did not increase milk production or feed intake when headlocks were removed. Twoyear-old and older cows did not differ in response to headlocks and neckrails. Prudent use of headlocks increases labor efficiency of a commercial dairy. Managing a dairy without headlocks is a challenge because cows must be sorted and worked off the milking parlor flow. In the case of large milking parlors, it may be necessary to process 50-200 cows per hour. Depending upon the treatment facilities, this number of cows may create a bottleneck in the dairy. For many routine procedures, headlocks offer the simplest and most cost-effective alternative. It is important to note that headlocks can be mismanaged. This is especially true during summer months. Locking up cows for extended periods without access to water or shade may have adverse effects during summer heat stress. It is important to minimize lock-up time. Consideration should also be given to t raining heifers to headlocks prior to calving. It is very likely that untrained heifers may be reluctant to be placed in headlocks. If this occurs, intake could be limited during their first exposure to headlocks. If heifers are not trained to headlocks prior to calving, one should determine if they should be locked-up each day during the first week of lactat ion. Headlocks can be successfully used on a dairy. The critical question is how will they be managed. Successful managers of headlocks minimize restraint time, push-up or feed pens often (68 times per day), and avoid use of headlocks during late morning and afternoon hours during the summer months.

Diurnal Variations of Convective Activity and Rainfall in Tropical Asia.

The diurnal variations of convective activity and rainfall in tropical Asia are investigated using hourly equivalent black body temperature (TBB) data from the Japanese Geostationary Meteorological Satellite (GMS-5), and hourly (or 3-hourly) rainfall data from Bangladesh, Thailand, Vietnam and Malaysia. As an index of convective activity, we use the frequency of occurrence of the difference in TBB between the infrared-1 and the water vapor channel ΔTBB (= TBB(IR1) − TBB(WV)) of less than 3K. By using this index, the diurnal variations of convective activity and rainfall have approximately the same phase. The time when convective activity reaches its maximum and minimum is examined in the domain of 80-120°E and 0-30°N. As a result, it is found that the largest number of grids exhibits the maximum at 17LT (local time) and 14LT, and the minimum at 11LT and 21LT over land and sea, respectively. Moreover, without using the harmonic analysis, which is a conventional method of analyzing the diurnal variation, areas with the maximum during the late night-early morning hours are clearly separated from those with the afternoon-early evening maximum. This late night-early morning maximum is mostly found in the windward areas of mountains, in basins and valleys, and in coastal areas. Therefore, this kind of maximum is most likely associated with terrain or its induced local circulations such as mountain and land breezes. From the analysis of rainfall data, it is also shown that the late night-early morning maximum is found at stations with high rainfall. The number of stations with the late night-early morning maximum is less than that with the afternoon-early evening maximum. But, the mean daily rainfall at the former stations is on average a few times greater than that at the latter stations. Thus, the diurnal variation averaged for all stations in the four countries has two nearly equal maxima at 05LT and 16LT. This result suggests a strong possibility that the late night-early morning maxima of convective activity and rainfall have a great efffect on energy and water cycles in tropical Asia.

Longitudinal changes of circadian leptin, insulin and cortisol plasma levels and their correlation during refeeding in patients with anorexia nervosa.

To study the longitudinal changes in plasma levels of leptin, insulin and cortisol during the transition from the state of starvation to the state of refeeding focussing on diurnal secretion characteristics and their temporal relationships. Leptin, insulin and cortisol were measured every 2h for 24h during acute starvation (T1). Sampling was repeated after reaching half the target-body mass index (BMI) (T2) and again at target-BMI (17. 5kg/m(2); T3). The temporal relationships between the diurnal secretion patterns were assessed by cross-correlation analysis. Although BMIs at T1 were uniformly low, leptin levels varied widely within a range clearly below normal levels (0.03-1. 7microg/l). With increasing body fat during the course of refeeding, mean leptin levels increased from 0.64microg/l (range: 0.27-1. 73microg/l) (T1) to 1.61microg/l (range: 0.36-4.2microg/l) (T2) and to 3.67microg/l (range: 0.7-9.8microg/l) (T3). Circadian leptin secretion patterns showed maximal values uniformly around 0200h and minimal values around 0800h at all stages of the study. At all three weight levels, plasma leptin levels were highest between midnight and the early morning hours and lowest around the late morning hours. Refeeding neither profoundly changed secretion patterns of leptin nor did it change the positive, time-delayed relationship between leptin and insulin with increments in insulin secretion preceding those of leptin by 6h. A temporal relationship between leptin and cortisol could not be demonstrated in the state of semistarvation but emerged after a substantial weight gain; at that time, leptin increases preceded cortisol increases by 8h. Absolute leptin, insulin and cortisol levels are profoundly changed during starvation in anorectic patients, while refeeding, paralleled by a BMI gain, reverses these changes. During refeeding the relationship between leptin and cortisol changed profoundly, showing no significant correlation in the state of starvation, whereas at T3 after refeeding a strong inverse relationship could be observed. Leptin and insulin did not correlate significantly at any of the three stages studied.

The pattern and predictors of intentionally inflicted injuries on Greek adults; data from an Emergency Injury Surveillance System (EDISS)

Background Intentional injuries due to violence are both a social and a public health problem in most societies. This study assesses the patterns and some of the sociodemographic determinants of violence-related injuries among Greek adults. Methods Data recorded by the Emergency Department Injury Surveillance System (EDISS) during the two-year period 1996-1997 were used. This database relies on all age injury data collected in the emergency departments of three sentinel hospitals, covering both urban and rural population areas. Results Among 52026 recorded injuries, 1322 (3%) were violence related, excluding self-inflicted injuries, while the majority of injuries (28269) were attributed to home and leisure accidents. Weapons of any type were used only in 5% of violence-related injuries. In comparison to home and leisure injuries, the intentionally inflicted injuries occurred more frequently among men, among those 25-54 years old, and were particularly common among migrants and during late night and early morning hours. Violence-related injuries frequently occur in pubs, restaurants, cafeterias and other places of entertainment. However, 52% of violence-related injuries among women occurred at home. Intentional injuries were generally more severe than unintentional ones. Conclusions We conclude that violence is not a negligible public health problem in the Greek population, but is considerably less serious than in most other developed countries. In particular, firearms-related injuries represent a very small fraction of the generally low incidence of violence-related injuries in this Mediterranean country.

Effect of quinapril or metoprolol on circadian sympathetic and parasympathetic modulation after acute myocardial infarction

Abnormal autonomic nervous system impairment in patients with acute myocardial infarction (AMI) has a circadian pattern with the greatest manifestation in the morning hours; it probably plays an important role in the pathogenesis of cardiac arrhythmias and acute ischemic syndromes. Angiotensin-converting enzyme inhibitors improve autonomic function in patients with AMI, but the circadian pattern of this effect has not been studied. Heart rate variability–normalized frequency domain indexes were assessed 5 days (baseline) after the onset of uncomplicated AMI and 30 days after therapy with quinapril (n = 30), metoprolol (n = 30), or placebo (n = 30) with a solid-state digital Holter monitor. Normal subjects (n = 30) were used as controls. Quinapril increased parasympathetic and decreased sympathetic modulation, and improved sympathovagal interactions manifested by an increase in normalized high-frequency power (HFP), and a decrease in normalized low-frequency power (LFP), and their ratio (LFP/HFP) during the entire 24-hour period (p <0.001), with maximal effect on the ratio (p <0.0001) between 02.00 to 04.00 a.m., 08.00 to 11.00 a.m., and 19.00 to 22.00 p.m. (Δ% ratio −30%, −32%, and −26%, respectively). Metoprolol increased HFP and decreased LFP and the LFP/HFP ratio mainly between 08.00 a.m. to 12.00 noon, and 19.00 to 22.00 p.m. (Δ% ratio −21%, and −12% respectively, p <0.001). Heart rate variability indexes in the placebo group and controls remained unchanged 30 days after the baseline study. In conclusion, quinapril increased parasympathetic, and decreased sympathetic and partially restored sympathovagal interaction in patients with uncomplicated AMI during the entire 24-hour period, with peak effect in the early and late morning and evening hours. Metoprolol had a similar effect during the late morning and evening hours, but at a lower level. These effects may prove beneficial in reducing cardiac arrhythmias and acute ischemic syndromes in post-AMI patients.

Circadian Variation in Ischemic Stroke Subtypes

While previous studies suggest that the peak time period for the occurrence of ischemic stroke is in the mid- to late-morning hours, detailed information pertaining to circadian variations among the various stroke subtypes has been limited. The purpose of our study was to define the circadian patterns of symptom onset in an acute stroke trial with an established system for stroke subtype classification. An analysis was conducted on 1272 patients enrolled in the Trial of Org 10172 in Acute Stroke Treatment (TOAST) study. All patients had a documented time of stroke symptom onset, and all stroke subtype determinations were made by a single rater. The Greatest portion of atherothrombotic strokes (25.7%), cardioembolic strokes (30.5%), and strokes of other/unknown mechanism (27.1%) occurred between 6:01 AM and 12:00 noon. The greatest portion of lacunar strokes (31.6%) were present on awakening. More than one half of the infarcts in this series were either present on awakening or occurred in the mid- to late-morning hours. The correlation between stroke subtype and time of symptom onset did not reach statistical significance (P=0.07, Pearson's chi(2) method). Although there is a trend for clustering of ischemic stroke in the morning hours, there is insufficient specificity to predict with any reasonable likelihood the stroke subtype according to the circadian pattern of symptom onset.

MIs More Frequent in Winter.

It is well known that acute MI follows a circadian periodicity, with a peak incidence in the early to late morning hours. The effects of seasons and temperature on the occurrence of MI have been less clear. This study examined cases of MI …

Nonorganic insomnia in generalized anxiety disorder. 1. Controlled studies on sleep, awakening and daytime vigilance utilizing polysomnography and EEG mapping.

Objective and subjective sleep and awakening quality as well as daytime vigilance of insomniac patients with generalized anxiety disorder (GAD) were investigated, as compared with normal controls. Forty-four outpatients (25 females, 19 males), aged 24-65 (mean 43) years, diagnosed with non-organic insomnia (ICD-10: F 51.0), related to mild GAD (F 41.1), with a Hamilton anxiety (HAMA) score of 22 +/- 6 and a Zung self-rating anxiety (SAS) score of 37 +/- 6 were included. After 1 adaptation night, sleep induction, maintainance and architecture were measured objectively by polysomnography, subjective sleep and awakening quality were assessed by self-rating scales and visual analog scales, objective awakening quality was measured by a psychometric test battery, and diurnal tiredness was measured by a 3-min vigilance-controlled EEG (V-EEG) and a 4-min resting EEG mapping. In polysomnography patients demonstrated-as compared with normals-significantly increased wake time during the total sleep period and more early-morning awakening, decreased total sleep and sleep efficiency. Subjective sleep quality was deteriorated as well, as were well-being, drive, mood, and wakefulness in the morning. In noopsychic performance, GAD patients did rather well in attention, concentration, attention variability, and numerical memory, while fine-motor activity and reaction time were deteriorated. In psychophysiology, critical flicker frequency was decreased in the morning, while muscle strength, blood pressure and pulse rate showed no differences. EEG mapping during the late morning hours (10.00-12.00 h) demonstrated hypervigilance in the V-EEG, while in the resting recording an increased sleep pressure was detected. The latter was correlated significantly to the SAS score, but less so to the observer-rated Hamilton anxiety score. Our findings suggest that CNS hypervigilance and hyperarousal, as actual symptoms of GAD, lead to nocturnal insomnia, which in turn may cause-as a consequence of sleep pressure not slept off-diurnal tiredness.

SUMMER FEEDING HABITS OF DALL'S PORPOISE, PHOCOENOIDES DALLI, IN THE SOUTHERN SEA OF OKHOTSK

Stomach contents were analyzed from 85 Dall's porpoises, Phocoenoides dalli, taken in the southern Sea of Okhotsk during the summer of 1988. Thirteen species of fish and five species of cephalopods were identified. Fishes comprising 9 families were predominant and made up 79.9% of the total number of prey, with an overall occurrence in the stomachs of 100%. Three families of cephalopods made up 20.1% of the total number of prey ingested, with an overall occurrence of 74%. The Japanese pilchard, Sardinops sagax melanostictus, was the primary prey and represented 72.0% of the total prey in 97.3% of the stomachs examined. The gonatid squid, Berryteuthis magister, ranked second and made up 16.9% of the total prey in 61.6% of the stomachs. Walleye pollock, Theragra chalcogramma, was the third most abundant prey item consumed and represented 6.0% of the total, with an occurrence of 53.4%. Composition of the sample by the calculated total mass and caloric intake supports the numeric findings on the relative importance of the three major prey species to the DaIl's porpoise diet. The Japanese pilchard was clearly dominant using these indices and constituted 65.4% of the total mass and 80.7% of the caloric intake. Berryteuthis magister made up 26.8% of the mass and 15.5% of the caloric intake. Walleye pollock contributed the least to the diet with 7.9% of the total mass and 3.8% of the caloric intake. Volumetric data indicate that porpoises are feeding heavily on Japanese pilchard throughout the daylight hours. Berryteuthis magister was probably fed upon in the late night or early morning hours. Occurrence of both Dall's porpoise and Japanese pilchard in the coastal waters of the southern Sea of Okhotsk is seasonal. The summer movements of Dall's porpoise into this region may be related to the seasonal migration and abundance of the Japanese pilchard.

The supercell thunderstorm on 8 June 1990: Mesoscale analysis and radar observations

A case study of supercell thunderstorm development over Po Valley in northern Italy is discussed. The data were collected during MATREP, a field project operated in the month of June 1990. During the late morning hours of 8 June, before the passage of a cold front, a supercell and a single cell developed at the same time in eastern part of Po Valley, about 60 km apart from each other. Surface mesoscale analysis helps to explain these different storm evolutions due to interaction among local circulations, Adriatic Sea and orography. While dry wind (foehn) dumps the thermodynamic instability in single-cell environment, a moisture circulation affects the origin area of supercell. Computation of corresponding instability indices again supports the peculiar evolution of the two storms which is also analyzed by means of radar data.

Ground‐based studies of ionospheric convection associated with substorm expansion

The instantaneous patterns of electric fields and currents in the high‐latitude ionosphere are deduced by combining satellite and radar measurements of the ionospheric drift velocity, along with ground‐based magnetometer observations for October 25, 1981. For this purpose, an updated version of the assimilative mapping of ionospheric electrodynamics technique has been used. These global patterns are unobtainable from any single data set. The period under study was characterized by a relatively stable southward interplanetary magnetic field (IMF), so that the obtained electric field patterns do reflect, in general, the state of sustained and enhanced plasma convection in the magnetosphere. During one of the satellite passes, however, an intense westward electrojet caused by a substorm intruded into the satellite (DE 2) and radar (Chatanika, Alaska) field of view in the premidnight sector, providing a unique opportunity to differentiate the enhanced convection and substorm expansion fields. The distributions of the calculated electric potential for the expansion and maximum phases of the substorm show the first clear evidence of the coexistence of two physically different systems in the global convection pattern. The changes in the convection pattern during the substorm indicate that the large‐scale potential distributions are indeed of general two‐cell patterns representing the southward IMF status, but the night‐morning cell has two positive peaks, one in the midnight sector and the other in the late morning hours, corresponding to the substorm expansion and the convection enhancement, respectively.

Variability of emissivity and surface temperature over a sparsely vegetated surface

Radiometric surface temperatures obtained from remote sensing measurements are a function of both the physical surface temperature and the effective emissivity of the surface within the band pass of the radiometric measurement. For sparsely vegetated areas, however, a sensor views significant fractions of both bare soil and various vegetation types. In this case the radiometric response of a sensor is a function of the emissivities and kinetic temperatures of various surface elements, the proportion of those surface elements within the field of view of the sensor, and the interaction of radiation emitted from the various surface components. In order to effectively utilize thermal remote sensing data to quantify energy balance components for a sparsely vegetated area, it is important to examine the typical magnitude and degree of variability of emissivity and surface temperature for such surfaces. Surface emissivity measurements and ground and low‐altitude‐aircraft‐based surface temperature measurements (8–13 μm band pass) made in conjunction with the Monsoon '90 field experiment were used to evaluate the typical variability of those quantities during the summer rainy season in a semiarid watershed. The average value for thermal band emissivity of the exposed bare soil portions of the surface was found to be approximately 0.96; the average value measured for most of the varieties of desert shrubs present was approximately 0.99. Surface composite emissivity was estimated to be approximately 0.98 for both the grass‐dominated and shrub‐dominated portions of the watershed. The spatial variability of surface temperature was found to be highly dependent on the spatial scale of integration for the instantaneous field of view (IFOV) of the instrument, the spatial scale of the total area under evaluation, and the time of day. For the conditions which existed during most of the Monsoon '90 experiment, the differences in kinetic (physical) temperature between the vegetation and soil background were typically between 10° and 25°C at midday. These differences gave rise to large variations in radiometric composite surface temperatures observed with a ground‐based instrument configuration which allowed a ground IFOV of approximately 0.5 m. An evaluation of the frequency distribution for these observations indicated that the variance in surface temperature observed over an intensively sampled target area (approximately 500 m×120 m) increased significantly in the early to late morning hours of a typical diurnal heating cycle. For aircraft‐based composite radiometric temperature measurements at the watershed scale (with ground IFOV of approximately 40 m for each observation), much of the variability in surface temperature due to differences in soil and vegetation temperature was integrated into a single measurement; consequently, the variance between observations over the watershed was not significantly larger than those observed at length scales of 100 m.

Sensitivity studies on the air flow characteristics In Kharagpur using a meso-scale model

&#x0D; A three-dimensional hydrostatic model has been employed for the study of sea breeze circulations over south West Bengal with special reference to an inland station Kharagpur (22°.21' N, 87° 19'E). A series of sensitivity experiments have been performed to stress the Importance of differential heating on circulation over south West Bengal during pre-monsoon period. It is found that due to differential heating rate between land and sea surfaces, sea breezes can penetrate to the inland station Kharagpur and beyond even in case of moderate gradient wind. Surface observations at Kharagpur and pilot balloon observation at nearby station Kalaikunda are used to compare the model results. The onset of sea breezes, variation of the air temperature and humidity are In fairly good agreement whereas It over estimates the depth of the circulation and cannot predict the variation of the late morning hours surface wind.