托福阅读真题Official 48 Passage 3（四）

托福阅读真题Official 48 Passage 3（四）

Climate and Urban Development

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(1)at night when compensating sunlight is absent;(2)during the winter,when nights are longer and there is more heat generated in the city;and(3)when the region is dominated by a high-pressure air pressure(atmospheric pressure)is the pressure exerted by the mass of air above a given place 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 rising 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.

Question 7 of 14

All of the following are mentioned in paragraph 3 as contributing to an increase in the amount of heat within a city EXCEPT

A.home air conditioners

B.cars and trucks

C.streetlights

D.factory buildings

正确答案：C

题目详解

题型分类：否定事实信息题

原文定位：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.额外的城市热量通过汽车和工厂，以及工业和家庭取暖和冷却设备，在晚上释放（白天也释放热量）。

选项分析：

C选项该句中未提到，正确。

A选项该句中提到home air conditioner属于domestic heating and cooling units，排除。

B选项该句中题到cars and trucks属于vehicles，排除。

D选项该句中提到factory buildings是factories，排。

Question 8 of 14

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?Incorrect choices change the meaning in important ways or leave out essential information.

A.Until more studies are done,suggestions about the causes of precipitation in cities will focus on the roughness of terrain rather than on surface air and convergence.

B.Certain phenomena of city landscapes,such as large structures,cause surface air to slow and converge,which brings a change in weather patterns to cities and rural areas.

C.One reason why precipitation may be greater in cities than in the countryside is that large buildings that are found in cities cause surface air to slow and converge.

D.Studies that focus on large structures,which are only partly responsible for the increased roughness of city terrain,are incomplete in their explanation of increased precipitation.

正确答案：C

题目详解

题型分类：简化句子题

原文分析：考察识别主干内容和核心逻辑的能力。共两层意思：1.precipitation在城市要比在乡村严重。2.原因是大型建筑物使得地表空气缓慢、逐渐地汇聚在一起，使得城市地形粗糙度增加。逻辑关系是因果关系。

选项分析：

C选项与原文主干相符，in part替换为one reason，structures替换为buildings，正确。

A选项rather than一概念在原文没有提及，主干也无法与原文对应，错误。

B选项landscape可能是造成城市降水多的原因之一，而该选项将此作为唯一原因，错误。

D选项大型结构是不足以解释降水增加的，完全错误。

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