Official 48 Passage 3

纠错
置顶

Climate and Urban Development

纠错

The word "pronounced" in the passage is closest in meaning to

Click on an oval to select your answer. To choose a different answer,

click one different oval.

  • A
    examined
  • B
    relative
  • C
    strongest
  • D
    darkest
显示答案
正确答案: C

我的笔记 编辑笔记

  • 原文
  • 译文
  • For more than a hundred years, it has been known that cities are generally warmer than surrounding rural areas. This region of city warmth, known as the urban heat island, can influence the concentration of air pollution. However, before we look at its influence, let's see how the heat island actually forms.



    The urban heat island is due to industrial and urban development. In rural areas, a large part of the incoming solar energy is used in evaporating water from vegetation and soil. In cities, where less vegetation and exposed soil exist, the majority of the Sun's energy is absorbed by urban structures and asphalt. Hence, during warm daylight hours, less evaporative cooling in cities allows surface temperatures to rise higher than in rural areas. The cause of the urban heat island is quite involved. Depending on the location, time of year, and time of day, any or all of the following differences between cities and their surroundings can be important: albedo (reflectivity of the surface), surface roughness, emissions of heat, emissions of moisture, and emissions of particles that affect net radiation and the growth of cloud droplets.



    At night, the solar energy (stored as vast quantities of heat in city buildings and roads) is slowly released into the city air. Additional city heat is given off at night (and during the day) by vehicles and factories, as well as by industrial and domestic heating and cooling units. The release of heat energy is retarded by the tall vertical city walls that do not allow infrared radiation to escape as readily as does the relatively level surface of the surrounding countryside. The slow release of heat tends to keep nighttime city temperatures higher than those of the faster-cooling rural areas. Overall, the heat island is strongest at night when compensating sunlight is absent; during the winter, when nights are longer and there is more heat generated in the city; and when the region is dominated by a high-pressure area with light winds, clear skies, and less humid air. Over time, increasing urban heat islands affect climatological temperature records, producing artificial warming in climatic records taken in cities. This warming, therefore, must be accounted for in interpreting climate change over the past century.



    The constant outpouring of pollutants into the environment may influence the climate of the city. Certain particles reflect solar radiation, thereby reducing the sunlight that reaches the surface. Some particles serve as nuclei upon which water and ice form. Water vapor condenses onto these particles when the relative humidity is as low as 70 percent, forming haze that greatly reduces visibility. Moreover, the added nuclei increase the frequency of city fog.



    Studies suggest that precipitation may be greater in cities than in the surrounding countryside; this phenomenon may be due in part to the increased roughness of city terrain, brought on by large structures that cause surface air to slow and gradually converge. This piling up of air over the city then slowly rises, much like toothpaste does when its tube is squeezed. At the same time, city heat warms the surface air, making it more unstable, which enhances risings air motions, which, in turn, aids in forming clouds and thunderstorms. This process helps explain why both tend to be more frequent over cities.



    On clear still nights when the heat island is pronounced, a small thermal low-pressure area forms over the city. Sometimes a light breeze-called a country breeze-blows from the countryside into the city. If there are major industrial areas along the outskirts, pollutants are carried into the heart of town, where they tend to concentrate. Such an event is especially probable if vertical mixing and dispersion of pollutants are inhibited. Pollutants from urban areas may even affect the weather downwind from them.


  • 一百多年来,大家都知道城市一般比周围的农村温度更高。被称为城市热岛的区域性温暖可以影响空气污染的聚集。然而,在着眼于它的影响之前,让我们看看热岛事实上是如何形成的。

    城市热岛是由于工业开发和城市开发产生的。在农村地区,很大一部分的入射太阳能被消耗于植被和土壤中水分的蒸发。城市的植被和裸土较少,大部分的太阳能量被城市建筑和沥青吸收。因此,在温暖的白天,城市更少的蒸发冷却使地面温度上升得比农村地区更高。城市热岛的原因很复杂。根据不同的位置、季节、一天中的不同时间,城市和周围环境之间的以下任何差异都可能是重要因素:反照率(表面反射率)、表面粗糙度、热量排放、水分排放、影响净辐射和云微滴增长的颗粒排放。

    在夜间,太阳能(储存在城市建筑和道路的巨大热量)缓慢释放到城市空气中。额外的城市热量也在夜间(当然白天也有)排放,来源包括车辆和工厂,以及工业和家庭的供热和制冷装置。热能量的释放是被高大垂直的城市墙所减缓,这些墙面使得红外线辐射不能像在附近乡村相对水平的表面那样逃离。热能的缓慢释放使得城市在夜间保持高于快速冷却农村地区的温度。总体而言,热岛在以下几个情况是最强的:(1)在夜间,当补偿性的阳光缺失的时候;(2)在冬季,当夜晚更长,有更多的热量在城市产生的时候;(3)当该地区被一个伴随轻风、晴朗天空和干燥空气的高压区控制的时候。随着时间的流逝,加剧的城市热岛影响气象温度记录,在城市中制造了人工气候变暖。因此,解释过去一个世纪的气候变化必须考虑这一变暖(现象)。

    环境中污染物的不断涌入可能影响城市气候。某些颗粒反射太阳辐射,从而减少到达表面的阳光。有些颗粒成为形成水和冰的聚集核心。当相对湿度最低70%时,水蒸气凝就能结在这些粒子上,形成大大降低能见度的灰霾。此外,增加的颗粒聚核提高了城市起雾的频率。

    研究表明,城市的降水量可能比周围的乡村更大;这一现象的部分原因可能是城市地形的更大的粗糙度,城市的大型建筑使得地表空气流动减缓并逐渐聚集。城市上空的空气堆积起来,然后慢慢地上升,像被挤的牙膏一样。同时,城市热量加热了表面空气,使其更加不稳定,提高了上升气流的运动,而这反过来,有助于云和雷暴的形成。这个过程有助于解释为什么这两个现象在城市中更加频繁。

    在晴朗平静的夜晚,当热岛效应最显著的时候,一个小的热低压区域在城市形成。有时一阵轻风——被称为乡村风——从乡村吹到城市。如果郊区有主要的工业区,污染物会被带到城市的核心,往往在这里聚集起来。如果污染物的垂直混合和扩散被抑制,这样的聚集事件就特別容易发生。来自于城市地区的污染物甚至影响它们下风区的天气。
  • 官方解析
  • 网友贡献解析
  • 标签
    4 感谢 不懂
    解析

    题型分类:词汇题

    原文定位:词汇所在句On clear still nights when the heat island is pronounced a small thermal low-pressure area forms over the city.”即“在晴朗平静的夜晚,热岛效应明显,城市会形成一个小的热低压区。”pronounced:显著的;强烈的。

    选项分析:examined:检查过的;relative:相对的;strongest:最强烈的;darkest:最黑暗的。因此,选项C符合题干词意。

题目讨论

如果对题目有疑问,欢迎来提出你的问题,热心的小伙伴会帮你解答。

最新提问