Hurricanes
A hurricane is a fiercely powerful rotating tropical storm that is 200 to 2000 kilometers across. Hurricanes have a calm central region of low pressure between 20 and 100 kilometers across, known as the eye. They occur in tropical regions around the world, and are called typhoons in south-east Asia and the Pacific, and cyclones in the Indian Ocean and Australia. The term hurricane is derived from Huracan, the name of a Mayan storm god. Over its lifetime, one of these massive storms can release as much energy as a million Hiroshima (日本廣島) nuclear bombs.
The brutality of each annual hurricane season shifts according to decadal variation, but there is now evidence to suggest global warming could be making hurricanes more frequent and unpredictable. As populations and economies grow along coastal regions, the damage from these storm is increasing.
Hurricane Katrina: The Aftermath—The Most Destructive US Natural Disaster in Living Memory
In 2005, hurricane Katrina had a devastating impact on the Gulf Coast of the US, leaving a disaster zone of 230,000 square kilometers in its wake and causing damage estimated at $ 75 billion. Katrina whipped up sustained winds of 225 kilometers per hour and a 5-to-9-metre-high "storm surge" of sea water. The maelstrom (大渦旋)tore through New Orleans‘ flood defenses and flooded 80% of the city. Thousands were killed or injured and more than half a million people were displaced in a humanitarian crisis not seen in the US since the Great Depression.
Forming a Storm
The seed for hurricane formation is a cluster of thunderstorms over warm tropical waters. Hurricanes can only form and grow when sea-surface temperatures exceed 27°C and the surrounding atmosphere is calm. These requirements are met between June and November in the northern hemisphere. In Australia and the southern hemisphere, the cyclone season runs from October to May.
Under these conditions, large quantities of water evaporate and condense into clouds and rain-releasing heat in the process. It is this heat energy, combined with the rotation of the Earth, that drives a hurricane.
When the warm column of air from the sea surface first begins to rise, it causes an area of low pressure. This in turn creates wind as air is drawn into the area. This wind drags up more moisture-laden air from the sea surface in a positive feedback process that swells the storm. Cold air falls back to the ocean surface on the outside of the storm.
When wind speeds hit 37 kilometers per hour, these mild, wet and gray weather systems are called as tropical depressions. Hurricane Katrina formed in this way over the south-eastern Bahamas on 23 August 2005 and was labeled Tropical Depression No.12 of that year.
If this process happens far enough from the equator—typically at latitudes of more than 10°—then the Coriolis force associated with the rotation of the Earth sets the massive weather system spinning, with winds spiraling in towards the center.
The weather systems spin anticlockwise in the northern hemisphere and clockwise in the southern. The rotation of the Earth also determines the direction in which these storms travel, so hurricanes in the north Atlantic move west towards Central and North America.
Categorically Speaking
As winds increase to a sustained speed of 63 kilometers per hour, a tropical depression becomes a tropical storm. Such storms are then given a name—such as Charley, Frances, Gilbert, Isabel, Ivan Jeanne or Mitch—which cycle through the alphabet each year.
A tropical storm becomes a category 1 hurricane (or cyclone or typhoon) when winds reach sustained speeds of 120 kph. A hurricane becomes category 2 when sustained winds hit 154 kph, category 3 at 179 kph, category 4 at 210 kph, and finally the most devastating variety, category 5, when wind speeds hit 250 kph.
Category 5 hurricanes rarely make it to land—2005's Katrina briefly achieved category 5 status, but diminished slightly before landfall.
Hurricanes are characterized by high winds, torrential rain and sometimes tornadoes. These conditions cause massive damage to buildings and infrastructure and create flash floods, mudslides and storm surges of sea water. Storm surges are huge tsunami-like waves resulting from the acutely low pressure at the eye of the hurricane. The low pressure draws in water, raising sea levels by up to 4 meters, Hurricanes may even trigger weak earthquakes and set the Earth vibrating.
Hurricanes can also contain very tall clouds called hot towers that stretch up to the ceiling of the troposphere (對(duì)流層).Hurricanes can continue to grow in size and ferocity as long as they are over warm waters but in reality they rarely persist for more than a few weeks. As soon as they travel inland, their power diminishes rapidly, as they can no longer draw up warm, damp air from the sea—they run out of steam, or water vapor at least.
Climate Linked
The storm season of 2005 was the busiest since records began in 1928: 26 tropical storms formed in the north Atlantic, 12 more than 2004.
Fourteen of these—including Beta, Dennis, Emily, Epsilon, Ophelia, Rita and Stan—became hurricanes, setting another record as three developed to category 5. Wilma was the most intense hurricane ever recorded in the north Atlantic.
The hurricane season in 2005 was remarkable in other ways too. An unusual south Pacific hurricane battered the coasts of Guatemala and El Salvador in May—the first ever to strike from the direction of the Pacific. More of a surprise was hurricane Catarina, the first ever known to come from the southern Atlantic—a place the textbooks claim is too cool for hurricanes to form.
Hurricane activity is predicted to be above average in 2006 as well.
This burst of activity has fuelled speculation that climate change may be responsible. There has been a string of studies suggesting that hurricanes have become more intense, powerful and unpredictable in the last 30 years—and that this is not just down to normal decadal variation in storm activity.
One controversial study argues that the number of intense hurricanes worldwide has almost doubled over the past 35 years and it pins the blame on rising sea-surface temperatures. As the world warms, the amount of sea surface that exceeds the 27°C required to spawn a hurricane will increase— but a lot of other factors are also required for hurricanes to form, so experts are not sure what the future holds.
If hurricanes do become more frequent and intense, we might be able to find ways to mitigate their effects or even modify the weather. Possible methods include sending them off course, using water-absorbent powder to mop up clouds, coating the sea surface with fish oil or surfactants to stop warm water evaporating, and even zapping the colder streams of air in hurricanes and tornadoes with microwaves to disrupt their structure.
Questions:
1. According to the passage, both typhoons and cyclones are all hurricanes—they just appear in the different parts of the temperate zone.
2. The damaging power of each annual hurricane season changes about every ten years, but there is now evidence to suggest global warming could be the reason to make hurricanes strike more frequently and cause thousands of scientists' attention.
3. Hurricane Katrina is the most destructive US natural disaster in living memory, causing damage estimated at $ 75 billion, killing or injuring thousands of people, making more than 500,000 people displaced, which has not been seen since the Great Depression.
4. The hurricanes can only form and grow between June and November in the northern hemisphere, from October to May in Australia and the southern hemisphere.
5. It is the rain-releasing heat energy, joined with _________that drives a hurricane.
6. Tropical depressions are mild, wet and gray weather systems risen from the surface of the sea when
wind speeds hit _________ per hour.
7. Hurricanes are characterized by high winds, _________.
8. Hurricanes can also contain hot towers, which are _________ that stretch up to the ceiling of the troposphere.
9.The hurricane Catarina caused a big surprise, for it's the first ever known to come from ________ —a place the textbooks claim is too cool for hurricanes to form.
10. One controversial study argues that the number of intense hurricanes worldwide has almost doubled over the past 35 years and it ascribes the reason to ________
答案及解析
本文主要介紹了災(zāi)難性天氣颶風(fēng)及其形成原因、活動(dòng)范圍、破壞力以及具體預(yù)防方法。
1．N．推斷題。根據(jù)關(guān)鍵詞“typhoons and cyclones"查讀文章前一、二自然段，由文章第一段第三句“They occur in tropical regions around the world，and are called typhoons in south-east Asia and the Pacific，and cyclones in the Indian Ocean and Australia”可知，臺(tái)風(fēng)和氣旋確實(shí)屬于颶風(fēng)的不同種類，但是它們都應(yīng)出現(xiàn)在熱帶“tropical zone”而不是溫帶“temperate zone”。
2．NG．細(xì)節(jié)題。根據(jù)關(guān)鍵詞“every ten years"和“global warming"查讀文章第三自然段第一句“The brutality of each annual hurricane season shifts according to decadal variation，but there is now evidence to suggest global warming could be making hurricanes more frequent and unpredictable”可知，全球變暖是每十年中颶風(fēng)破壞力變化的原因之一，但由此句以及其上下旬的查讀，并沒有發(fā)現(xiàn)有關(guān)“cause scientists’attention"方面的內(nèi)容，所以整句判斷為“NG”。
3．Y．推斷題。根據(jù)關(guān)鍵詞“Hurricane Katrina”，“$75 billion”和“the Great Depression”參看小標(biāo)題“Hurricane Katrina：The Aftermath--The Most Destructive US Natural Disaster in Living Memory”和其后第一段第一句“…causing damage estimated at$75 billion"以及最后一句“Thousands were killed or injured and more than half a million people were displaced in a humanitarian crisis not seen in the US since the Great Depression”，由此可以推斷本命題中對(duì)于 Katrina的描寫均屬正確。 ．
4．Y．細(xì)節(jié)題。根據(jù)關(guān)鍵詞“form and grow”和“June and November”，參看小標(biāo)題“Forming a Storm”中第一段第三句“These requirements are met between June and November in the northern hemisphere．In Australia and the．southern hemisphere，the cyclone season runs from October to May”，可知颶風(fēng)在南北半球的形成時(shí)間與此命題描述相符。
5．the rotation of the Earth．細(xì)節(jié)題。根據(jù)關(guān)鍵詞“drives a hurricane”參看小標(biāo)題“Forming a Storm“中第二段第二旬“It is this heat energy，combined with the rotation of the Earth，that drives a hurricane"。題目中的“joined with”是原文中的“combined with"的同義替換。
6．37 kilometers．細(xì)節(jié)題。根據(jù)關(guān)鍵詞“tropical depressions"，參看小標(biāo)題“Forming a Storm” 中第四段第一句“When wind speeds hit 37 kilometers per hour，these mild，wet and gray weather systems are called as tropical depressions"。
7．torrential rain and sometimes tornadoes．細(xì)節(jié)題。根據(jù)關(guān)鍵詞“characterized by”，參看小標(biāo)題“Categorically Speaking”中第四段第一句“Hurricanes are characterized by high winds，torrential rain and sometimes tornadoes”。
8．very tall clouds．細(xì)節(jié)題。根據(jù)關(guān)鍵詞“hot towers”，參看小標(biāo)題“Categorically Speaking”中第五段第一句“Hurricanes can also contain very tall clouds called hot towers that stretch up to the ceiling of the troposphere”。
9．the southern Atlantic．細(xì)節(jié)題。根據(jù)關(guān)鍵詞“hurricane Catarina”，參看小標(biāo)題“Climate
Linked”中第三段最后一句“More of a surprise was hurricane Catarina，the first ever known to come from the southern Atlantic—a place the textbooks claim is too cool for hurricanes to form"。
10．rising sea．surface temperatures．細(xì)節(jié)題。根據(jù)關(guān)鍵詞“the past 35 years”參看小標(biāo)題“Climate Linked"中第六段第一句“One controversial study argues that the number of intense hurricanes worldwide has almost doubled over the past 35 years and it pins the blame on rising sea-surface temperatures”。題目中的“ascribes the reason to"為原文中的“pins the blame on”的同義替換。