新托福阅读复习材料美国科学文摘精选.docx

1、新托福阅读复习材料美国科学文摘精选新托福阅读复习材料：美国科学文摘精选The Planet Earth The 2000 Antarctic Ozone Hole Was Largest Ever The 2000 Antarctic Ozone Hole was the largest ever observed. Earths wetter upper atmosphere may delay global ozone recovery. NASA researchers have found that an increase in water vapor in the stratosph

2、ere, stemming partially from greenhouse gases, may delay ozone recovery and increase the rate of climate change. To check on the long-term stratospheric cooling and ozone depletion, NASA put data from satellites and other remote sensors into its GISS global climate model. It was the first study to l

3、ink greenhouse gases to increased ozone depletion over populated areas. Water and ozone. Climate models show cooler stratospheric temperatures happen when there is more water vapor present. Water vapor also leads to the breakdown of ozone molecules. The stratosphere is the dry layer of the atmospher

4、e above the troposphere, where temperatures increase with height. According to satellite data, upper atmospheric temperatures around the world - at altitudes of 20 to 35 miles high - have cooled between 5.4 and 10.8 degrees Fahrenheit over recent decades. Driving forces. NASA found two driving force

5、s behind the change in stratospheric moisture: Increased emissions of the greenhouse gas methane are transformed into water in the stratosphere, accounting for about a third of the observed increase in moisture there. More water is transported from the lower atmosphere. Warmer air holds more water v

6、apor than colder air, so the amount of water vapor in the lower atmosphere increases as it is warmed by the greenhouse effect. Greenhouse gases, such as carbon dioxide and methane, may enhance the transport of water into the stratosphere. The increased transport of water vapor to the stratosphere se

7、ems likely to have been induced by human activities. Ozone destruction. Rising greenhouse gas emissions account for all or part of the water vapor increase, which causes stratospheric ozone destruction. When more water vapor works its way into the stratosphere, the water molecules can be broken down

8、, releasing reactive molecules that can destroy ozone. If the trend of increasing stratospheric water vapor continues, it could increase future global warming and impede ozone stratospheric recovery. The impact on global warming comes about because both water vapor and ozone are greenhouse gases, wh

9、ich trap heat leaving the Earth. When they change, the Earths energy balance changes too, altering the surface climate. Warmer ground. Increased water vapor in the stratosphere makes it warmer on the ground by trapping heat, while the ozone loss makes it colder on the ground. Water vapor has a much

10、larger effect, so that overall the changes increase global warming. Although ozone depletion cools the Earths surface, repairing stratospheric ozone is important to block harmful ultraviolet radiation. Other greenhouse gas emissions also need to be reduced. UARS satellite. NASA combined seven years

11、of data from the Upper Atmosphere Research Satellite (UARS) Halogen Occultation Experiment (HALOE) with data collected on the ground to paint a complete picture of the upper atmosphere. NASAs HALOE was aboard the UARS spacecraft when it was launched September 12, 1991 as part of the Earth Science En

12、terprise Program. The spacecrafts mission at launch was to improve understanding of stratospheric ozone depletion by analyzing vertical profiles of ozone, hydrogen chloride, hydrogen fluoride, methane, water vapor, nitric oxide, nitrogen dioxide, and aerosols. Fourteen years of lower stratospheric m

13、easurements have revealed large increases in water vapor. Though some older studies conflict with lower stratospheric observations of water vapor trends, new studies agree with the increases, showing they have been taking place for more than four decades. What Is An Ozone Hole? Ozone molecules are m

14、ade up of three atoms of oxygen. They comprise a thin layer of the atmosphere that absorbs harmful ultraviolet radiation from the Sun. Most atmospheric ozone is found between approximately six miles and 18 miles above the Earths surface. An ozone hole is what scientists call an ozone depletion area

15、of in that region of Earths atmosphere. Really big hole. The largest-ever ozone hole was detected on September 6, 2000, by the Total Ozone Mapping Spectrometer (TOMS) aboard a NASA satellite known as Earth Probe (TOMS-EP). The Antarctic ozone hole is three times larger than the entire land mass of the United States, making it the largest such area ever observed. The hole had expanded to a record size of 11 million square miles. The