Shortwave Energy Research Articles

COMPUTATIONAL HYDRAULICS: AN ALTERNATIVE VIEW

In almost all classical hydraulics, problems are posed in terms of determining what happens at given places and times. It is possible, however, to pose these problems "the other way around", so to speak, by asking at which place a given event occurs at a given time. In quantitative terms, the problem is posed of determining those values of the independent variables at which given values of the dependent variables occur at given times. This alternative view has certain advantages over that traditionally used, and also disadvantages. The traditional approach can be used most efficiently when, roughly speaking, the same order of variation occurs in the dependent variables over most of the domain during most of the time. In a large number of real-life situations, however, nothing much happens in most of the domain during most of the time but the areas of interest are concentrated in small regions that may move across the domain in time. Examples are the spillage, transport and dispersion of pollutants in watercourses, the propagation of Tsunamis waves, halocline and thermocline decay, bio-chemical process at air-water and bed-water interfaces and haloclines and also the transport of short wave energy. The alternative methods provide a generally superior resolution in these situations, as compared with the traditional ones, but this advantage is bought at the cost of an increased complexity of the numerical scheme or code. Applications are shown to the transport processes, dispersion process and conservation (propagation) processes of hydraulics, so covering most common applications. The transport applications are shown to be related to an existing method, which is then generalised, the dispersion applications appear to be new in hydraulics while the conservation applications generalise on the one side to a method so far only outlined in gas dynamics and on the other side to the method of characteristics. The study concludes with an outline of the problem of best descriptions.

Vegetational Responses to Latitudinal Variations in Slope Angle and Aspect

The radiant energy income of a slope influences its ambient temperatures and water movements, both of which are important controls on the growth behaviour, species composition and structure of its vegetation cover. Therefore, information about the radiation environments of topographically diverse areas should provide a basis for predicting the likelihood of local variations in vegetation composition and structure. From a simple model of the annual shortwave energy load of slopes of different angle and compass orientation we predict that aspect effects should be greatest at 450 N/S and least in equatorial and polar regions. Other predictions concern likely physiological responses of plants to varying slope angle over the range of latitlude. A literature review shows good agreement between these physically based predictions and observations of vegetation patterns in a geographically wide range of countries.

Remote sensing of algal blooms by aircraft and satellite in Lake Erie and Utah Lake

During late summer, when the surface waters of Lake Erie reach their maximum temperature, an algal bloom is likely to develop. Such phenomena, which characterize eutrophic conditions, have been noticed on other shallow lakes using the Earth Resources Technology Satellite (ERTS-1). The concentration of the algae into long streamers provides additional information on surface circulations. To augment the ERTS Multispectral Scanner Subsystem (MSS) data of Lake Erie an aircraft was used to obtain correlative thermal-IR and additional multiband photographs. The algal bloom is highly absorptive in the visible wavelengths but reverses contrast with the surrounding water in the near-IR bands. The absorption of shortwave energy heats the dark brown algal mass, providing a hot surface target for the thermal-IR scanner. A large bloom of Aphanizomenon flos-aquae observed in Utah Lake together with recent bloom history in Lake Erie is used to verify the Great Lakes bloom.

Changes in Arctic Eriophorum Tussock Communities Following Fire

The arctic cottongrass (Eriophorum vaginatum ssp. spissum) tussock community is susceptible to fire even though it has a relatively small aboveground standing crop and the peaty substrate is wet even in years of low precipitation. While burns can be severe enough to kill all aboveground plant parts, differential protection is provided new shoots by tussocks bases, moss mats, and peat. Plant succession following fire was unique in that no new species invaded the area. Growth came principally from root stocks protected by the organic surface. Cottongrass and Carex spp. were the first to show regrowth following a June fire at one site. The role of cottongrass seedlings in colonizing these tussock communities was minor, because few seedlings older than 1 year were found on any of the sites. Epilobium angustifolium ssp.angustifolium and some Calamagrostis canadensis ssp. canadensis originated from seed although most plants of the latter species had long vigorous rootstocks. These plants occurred as minor components in the undisturbed community and increased when fire destroyed the competing species. The charred organic surface, being very dark, absorbed more short wave energy and the active layer depth increased by 35 to 50% in June and as much as 25% by late autumn. The same thermal regime was found in burns several years old. This warmer soil mass, over a longer period of time, was conducive to better growing conditions. Annual plant production had almost recovered after two growing seasons, and nutrient content of the plants was higher in the burned area. This may be due to the greater soil mass available for root exploration, to nutrient release by fire, and to greater microbial activity in the warmer soils. If other tundra communities respond to fire in a similar manner as cottongrass tussock communities, fires may act as a rejuvenating factor, as they do in other biomes

SOLAR RADIATION AND URBAN HEAT ISLANDS

ABSTRACT A model which attempts to simulate urban absorption of solar radiation is concerned with direct solar radiation, diffuse sky radiation, diffuse radiation reflected by buildings and streets, and the shortwave energy absorbed by typical urban structures. The ratio between solar radiation absorbed by three-dimensional building-street systems and two-dimensional horizontal surfaces under cloudless conditions indicates that cities undergo great variations with latitude and season. High structure systems absorb more than six times the radiation of nonurban plains. Shading effects can create absorptance less than that of a level surface. Observations at street level may lead to erroneous conclusions concerning the energy input for the total urban interface. The examination of a circular synthetic city with varying latitudinal radiation responses indicates that daytime urban heat islands are migratory phenomena and probably influence convective air circulation in the city, that downtown areas often absor...

USE OF FACTOR ANALYSIS TO INVESTIGATE RELATIONS BETWEEIS ENVIRONMENTAL VARIABLES AND FORAGE YIELD

Yields obtained over a 17-yr period from three grasses, one legume, and three grass–legume mixtures, together with six environmental variables, were subjected to factor analysis. Three of the variables (degree-days, hours of bright sunshine, and solar short-wave energy at the top of the earth’s atmosphere) showed a very close interrelation and were interpreted as measures of environmental energy. Age of crop was classed as a soil fertility factor; the available soil nutrients decreased as the age of the forage stand increased. In the factor patterns developed, differences between crops were small in comparison with the overall similarities. Production from the first harvest of the season was equally dependent on energy, soil moisture, and soil fertility. Regrowth was controlled principally by rainfall during and prior to the regrowth period. The ability of factor analysis to extract relatively simple relations from interrelated variables is clearly demonstrated.

Measurements of absorbed shortwave energy in a tropical atmosphere

Measurements of the upward and downward solar irradiance between sea level and 20,000 feet over the tropical Atlantic have shown values of atmospheric absorption exceeding computational estimates for a cloudless sky. The disagreement between observations and calculations is greater than either the observation error or the calculation uncertainty for a gaseous atmosphere. It is a logical conclusion that the disagreement comes about from the neglect of some atmospheric constituent in the calculations. Possible explanations for the high values of absorbed solar energy include increased path length due to the scattering by aerosols or absorption by the aerosols themselves.

Use of Atmometers in Estimating Evapotranspiration

Studies conducted by the California Department of Water Resources during the past 10 yr show that Livingston black and white spherical atmometers provide a practical means of estimating monthly and seasonal evapotranspiration. The difference of evaporation between the black and white atmometers is affected primarily by shortwave energy, whereas evaporation from either the black or white atmometer provides an index of the total amount of energy available for evapotranspiration. Various studies have been made, the results of which indicate that the type of background such as bare ground, dry range, or irrigated pasture has little effect upon the difference in evaporation between the black and white atmometers. Furthermore, the height above the surface of the ground or crop likewise has little or no effect upon the difference of evaporation. Monthly crop coefficients have been developed for some of the principal crops in the Central Valley of California, which provide evapotranspiration estimates consistently as good or better as can be obtained using coefficients developed from United States Weather Bureau Class A evaporation pan data.

Glacier Studies of the McCall Glacier, Alaska

Describes in detail this glacier in the Romanzof Mts., Brooks Range, northern Alaska, studied during the McCall Glacier Project, 1957-58. The crescent-shaped body of ice, approx. 8 km long, 640 m wide and 1,450 m high, has three cirques and a well defined drainage basin. From the confluence of the cirques, the ice drops in eight broad steps to the terminus. The hummocky ice surface is mantled with dust, rock and boulders which melt into the ice, causing cavities. Surface runoff from the cirques appears to flow into two main outlets: a marginal stream down the right side of the glacier, and circular fissure, located at the head of the glacier trunk. There are two principal areas of crevassing other than the ice faces above the cirques and the bergschrunds. The largest crevasse explored was 5 m wide, 60 m long and (estimated) 25 m deep. Blue bands and dirt-filled shear planes are common. Data collected include continuous records of long- and short-wave energy gain and loss, air temperatures, and wind speed. Investigations are noted of stratigraphy of snow, firn behavior, temperature gradients down to 100 m, and ice motion.

Newer Studies on the Clinical Application of Very Short Electrical Waves

TREATMENT with short wave diathermy in a condensor field, using frequencies from 2 × 107 to 108 Hz (or wave lengths from 15 to 3 meters) is definitely superior to long wave diathermy (3 × 105 to 106 Hz or 1,000 to 300 meters wave length) as regards deep doses and the possibility of controlling the energy. From a physical point of view this superiority is due to greater thermal penetration of poorly conducting macroscopic and microscopic layers of tissue because of an increase in the capacitative conductivity and of the ohmic conductivity of the tissues. But even at wave lengths of 6 meters, there is such a strong thermal stress on the fatty tissues that the dose of short wave energy which can be applied is limited because of the increase in the temperature of the subcutaneous fatty tissue. I call attention to the difficulties encountered when trying to produce high temperatures within the pelvis when treating local gynecological conditions. Some of the principal difficulties encountered in deep therapy ar...