【正文】 on known as the urban heat island. Heat islands develop best under particular conditions associated with light winds, but they can form almost any time. {13}█ {/13}The precise [7]configuration[/7] of a heat island depends on several factors. {13}█ {/13}For example, the wind can make a heat island stretch in the direction it blows. {13}█ {/13}When a heat island is well developed, variations can be extreme。滿分網(wǎng)（ ） Urban Climates(TPO231) The city is an extraordinary processor o mass and energy and has its own metabolism. A daily input of water, food, and energy of various kinds is matched by an output of sewage, solid waste, air pollutants, energy, and materials that have been transformed in some way. The quantities involved are [1]enormous[/1]. Many aspects of this energy use affect the atmosphere of a city, particularly in the production of heat. In winter the heat produced by a city can equal or [2]surpass[/2] the amount of heat available from the Sun. All the heat that warms a building eventually transfers to the surrounding air, a process that is quickest where houses are poorly insulated. But an automobile produces enough heat to warm an average house in winter。 and if a house were perfectly insulated, one adult could also produce more than enough heat to warm it. Therefore, even without any industrial production of heat, an urban area tends to be warmer than the countryside that surrounds it. The burning of fuel, such as by cars, is not the only source of this increased heat. Two other factors contribute to the higher overall temperature in cities. The first is the heat capacity of the materials that constitute the city, which is typically dominated by concrete and asphalt. During the day, heat from the Sun can be conducted into these materials have a significantly lower heat capacity because a vegetative blanket prevents heat from easily flowing into and out of the ground. The second factor is that radiant heat ing into the city from the Sun is trapped in two ways: (1) by a continuing series of reflection among the numerous vertical surfaces that buildings present and (2) by the dust dome, the cloud like layer of polluted air that most cities produce. Shortwave radiation from the Sun passes through the pollution dome more easily than outgoing long wave radiation does。 in winter, busy streets in cities can be ℃ warmer than the side streets. {13}█ {/13}Areas near traffic lights can be similarly warmer than the areas between them because of the effect of cars 滿分網(wǎng)（ ） standing in traffic instead of moving. The maximum differences in temperature between neighboring urban and rural environments is called the heatisland in tensity for that region. In general, the larger the city, the greater its heatisland intensity. The actual level of intensity depends on such factors as the physical layout, population density, and productive activities of a metropolis. The surfaceatmosphere relationships inside metropolitan areas produce a number of climatic peculiarities. For one thing, the presence or absence of moisture is affected by the special qualities of the urban surface. With much of the builtup landscape imperable by water, even gentle rain runs off almost immediately from rooftops, streets, and parking lots. Thus, city surfaces, as well as the air above them, tend to be drier between episodes of rain。 that is about a third of the Dutch population. [2]Importing the grain, which would have been expensive and time consuming for the Dutch to have produced themselves, kept the price of grain low and thus stimulated individual demand for other foodstuffs and consumer goods.[/2] Apart from this, being able to give up laborintensive grain production freed both the land and the workforce far more productive agricultural divisions. The peasants specialized in livestock husbandry and dairy farming as well as in cultivating industrial crops and fodder crops: flax, madder, and rape were grown, as were tobacco, hops, and turning. These products were bought mostly by 滿分網(wǎng)（ ） urban businesses. There was also a demand among urban consumers far dairy products such as butter and cheese, which, in the sixteenth century, had bee more expensive than grain. The high prices encouraged the peasants to improve their animal husbandry techniques。 others grew onions, mustard, and coriander。s rock art is constantly being revised, and earlier datings have been proposed as the result of new discoveries. {27} █{/27}Currently, eliable scientific evidence dates the earliest creation of art on rock surfaces in Australia to somewhere between 30,000 and 50,000 years ago. {27}█ {/27}This in itself is an almost inprehensible span of generations, and one that makes Australia39。s rock art is now established, the sequences and meanings of its images have been widely debated. Since the mid1970s a reasonably stable picture has formed of the anization of Australian rock art. In order to create a sense of structure to this picture, researchers have relied on a distinction that still underlies the forms of much indigenous visual culture a distinction between geometric and figurative elements. Simple geometric repeated patternscircles, concentric circles, and linesconstitute the iconography (characteristic images) of the earliest rockart 滿分網(wǎng)（ ） sites found across Australia. [20]The frequency with which certain, simple motifs appear in these oldest sites has led rockart researchers to adopt descriptive termthe Panaramitee stylea label which takes its name from the extensive rock pavements at Panaramitee North in desert South Australia, which are covered with motifs pecked into the surface[/20]. Certain features of these engravings lead to the conclusion that they are of great agegeological changes had clearly happened af