CHANGING WEATHER

ark Twain once said "The weather is always doing something... always getlng up new designs and trying them on the people to see how they will go."

Weather is blue skies, and puffy white clouds; torrential rains with gale force winds; twisters; flashes of lightning; or snow gently falling to the ground. The weather is the state of the atmosphere at any given time, it is experienced everywhere on Earth, it varies considerably from place to place, day to day, and season to season.

The long-term look at the weather in a place or region, the averaging of rainfall, the maximum and minimum temperatures is called climate. Climate in addition to the "averages" in the weather also includes the occurrences and frequencies of "extremes" in the weather. One such occurrence affecting the climate globally is El Nino.

El Nino, means "little one" in Spanish and refers to the Christ child – it is the phrase coined by Peruvian fisherman for the abnormally warm ocean current that appears off the northwestern coast of Peru around Christmas. El Nino, when pronounced and persistent, results in rainfall and temperature anomalies over certain areas of the globe. An El Nino event is caused when the Pacific trade winds that normally blow east to west begin to diminish and sometimes even reverse. Without these trade winds, warm tropical water from the South Pacific creeps toward South America, raising ocean temperatures near Peru by as much as 7 degrees. As these normally chilly waters heat up, masses of warm air soar into the atmosphere and alter weather patterns globally.

Scientists who are tracking this event say that the El Nino this season will be the "climactic event of the century." This El Nino is affecting portions of Chile, normally one of the driest areas in the world, with torrential rains. Snowstorms and heavy rains have blanketed the Peruvian Andes, causing flooding and mudslides. Drought conditions now exist in Indonesia and eastern Australia and are expected in northeast Brazil, southeastern Africa and the west Pacific. The west coast of North America will have more rain and snow, and the number of hurricanes will be reduced in the Atlantic.

Aside from the weather, El Nino will also affect the global economy: droughts will decrease crop yields, causing prices to rise and starvation. Fish migrations will be disrupted, and damage to coral reefs will reduce marine life and hinder those dependent on its ecosystems for their livelihood.

The last big El Nino (sometimes referred to as the worst in the 20^th century) occurred during 1982-83 and caused extensive damage throughout North and South America. A typical El Nino occurs every four to seven years and can last from three to four years.

Volcanic eruptions can also have an effect on world climate. Erupting volcanoes, although not a frequent occurrence, can emit huge quantities of gases and fine debris into the atmosphere causing short-term effects on the weather. For instance, the eruption in June 1991 of Mount Pinatubo in the Philippines caused average temperatures worldwide to fall by 1°F (0.6°C) over a 12-month period. Another effect is in the orange and red colours of a sunrise or sunset. The colours are intensified by the smoke and ash of an erupting volcano.

THUNDERSTORM

oisture, instability and lift are the three main ingredients needed: rain, strong winds, accompanied by bright flashes of lightning and the crack or thunder – a thunderstorm is born. There are more than 40,000 thunderstorms happening around the world everyday. The most severe thunderstorm can produce hail and spawn tornadoes.

The life cycle of a thunderstorm occurs in three stages: developing, mature, and dissipating. In the developing stage, a cumulus cloud (low-level and puffy) begins to grow and vigorous updrafts develop which prevent any precipitation from falling. The mature stage sees downdrafts developing and occurrences of lightning, thunder and violent down-drafts called "microbursts;" rain showers or hail may fall also. In the final stage, the cooler downdraft increases cutting off the supply of warm moist air to the thunderstorm. Rains begin to cease and altocumulus (mid-level) and cirrus (high-level, wispy) clouds may appear over the shrinking cumulus clouds. Thunderstorms may last from 15 minutes to several hours.

STORMS

ropical storms, known as typhoons in the Pacific and hurricanes in the Atlantic, claim more lives each year than any other storm. Hurricanes are formed from thunderstorms developing over the ocean or sea. Several thunderstorms come together to form a swirl of clouds. As the winds begin to grow, a distinct center will form in the cloud swirl and thisbecomes the "eye" of the storm. The storm continues to move, gaining energy from the warm air it sucks in. As the storm approaches land, winds are able to reach an excess of 150 mph and span path of damage from 200 to 500 miles across. Massive amounts of rainfall, and even tornadoes are formed as the storm makes landfall. The greatest threat to human life is the "storm surge" that follows the hurricane. After making landfall hurricanes turn into low-pressure systems or “rain depressions” which often bring heavy rains to inland areas and cause widespread flooding. Hurricanes are rated on the Saffir-Simpson scale in categories from 1 to 5.

<== попередня сторінка	\|	наступна сторінка ==>
FLOWER THIEVES	\|	PRECIPITATION

Не знайшли потрібну інформацію? Скористайтесь пошуком google:

Генерація сторінки за: 0.003 сек.