The climate of the Sahara has undergone enormous variation between wet and dry over the last few hundred thousand years. During the last ice age, the Sahara was bigger than it is today, extending south beyond its current boundaries.The end of the ice age brought better times to the Sahara, from about 8000 BC to 6000 BC, perhaps due to low pressure areas over the collapsing ice sheets to the north. Once the ice sheets were gone, the northern part of the Sahara dried out. However, not long after the end of the ice sheets, the monsoon which currently brings rain to the Sahara came further north and counteracted the drying trend in the southern Sahara. The monsoon in Africa (and elsewhere) is due to heating during the summer. Air over land becomes warmer and rises, pulling in cool wet air from the ocean, which causes rain. Paradoxically, the Sahara was wetter when it received more solar insolation in the summer. In turn, changes all in solar insolation are caused by changes in the Earth's orbital parameters.
By around 3400 BC, the monsoon retreated south to approximately where it is today,leading to the desertification of the Sahara. The Sahara is currently as dry as it was about 13,000 years ago. These conditions are responsible for what has been called the Sahara Pump Theory.
The Sahara is known to have one of the harshest climates in the world. The prevailing north-easterly wind can often cause the sand to form tornadoes. Precipitation, while rare is not unknown. Half of the Sahara receives less than 2 cm of rain a year, with the rest receiving up to 10 cm a year.The rainfall happens very rarely, but when it does it is usually torrential when it occurs after long dry periods, which can last for years.
翻釋中→Eng
2008-12-06 5:27 am
回答 (4)
2008-12-06 5:34 am
✔ 最佳答案
撒哈拉的氣候已經在最後很少10萬年在潮濕和乾燥之間經歷巨大的變化。 在上次冰河時代期間， 撒哈拉比是今天更大， 在它的冰川期的當今的。 末端以外延長南方把好時機帶到撒哈拉， 從大約8000 西元前在6000 西元前，或許由於低壓地區透過倒塌的冰床給北方。 一旦冰床消失，撒哈拉的北方的部分變干。 但是， 冰床的末端不久以後， 目前把雨帶到撒哈拉的季風變成更遠的北方並且在南撒哈拉抵消干的趨勢。 在非洲的季風(並且在別處) 由於在夏天加熱。 在土地上方的空氣變得更溫暖並且上升，從海洋節省涼爽的潮濕的空氣，這引起雨。 自相矛盾，當它在夏天收到更多的太陽能曝曬時，撒哈拉是濕潤劑。 依次，兌換全部在太陽曝曬內透過用地球的軌道的參數的變化被引起。 以大約西元前3400年，那些季風撤退南方隨著大約今天正導致那些沙漠化的那些撒哈拉。 撒哈拉目前象大約13，000 年以前一樣乾燥。 這些條件對負責所被叫為撒哈拉的抽理論。
撒哈拉在世界上有最惡劣的氣候之一，眾所周知。 流行的北東風經常能引起沙形成龍捲風。 降雨，當時稀有不未知。 撒哈拉的一半一年收到少於2厘米雨， 由於其餘收到多達10厘米降雨極少發生， 但是當它在長的乾燥的時期之後發生，這能持續多年時，做這通常是奔流的。
2008-12-06 5:52 am
撒哈拉大沙漠的氣候进行了在乾濕之間的極大的變異最後幾十萬年。 在最后冰河时期期間，撒哈拉大沙漠大于它今天，延伸南部在它的當前界限之外。冰河时期的结尾給撒哈拉大沙漠BC帶來了更好的时期，從大约8000到6000 BC，或許由于在崩溃的冰床的低压區域對北部。 一旦冰床去，撒哈拉大沙漠的北部變乾了。 然而，在冰床之後的末端，當前帶來的季風雨向撒哈拉大沙漠來了进一步北部并且抵制了乾燥趨向在南撒哈拉大沙漠。 季風在非洲(和在別處)归结于加熱在夏天期間。 在土地的空氣成為取暖器和上升，拉扯在從海洋的涼快的濕空氣，導致雨。 似是而非地，當它在夏天，接受了更加太陽的日光浴撒哈拉大沙漠是更濕的。 反过来，在太陽日光浴上的变化全部由在Earth'上的变化造成; s軌道參量。 由大约3400 BC，季風撤退了南部對大約它今天的地方，导致撒哈拉大沙漠的沙漠化。 撒哈拉大沙漠當前是一样乾燥的，象大约13,000年前。 這些情况对什麼负责称撒哈拉大沙漠泵浦理論。 撒哈拉大沙漠在世界上知道有其中一最苛刻的氣候。 戰勝的东北风可能經常造成沙子形成龍捲風。 降雨雪，当罕見时不是未知的。 撒哈拉大沙漠的一半接受少于2 cm雨每年，当休息接受10 cm一年。降雨量很少發生，但是，当它做时它通常是滔滔的，当它在長的乾燥期間以后时發生，可能多年来持續。
2008-12-06 5:33 am
The climate of the Sahara has undergone enormous variation between wet and dry over the last few hundred thousand years. During the last ice age, the Sahara was bigger than it is today, extending south beyond its current boundaries.The end of the ice age brought better times to the Sahara, from about 8000 BC to 6000 BC, perhaps due to low pressure areas over the collapsing ice sheets to the north. Once the ice sheets were gone, the northern part of the Sahara dried out. However, not long after the end of the ice sheets, the monsoon which currently brings rain to the Sahara came further north and counteracted the drying trend in the southern Sahara. The monsoon in Africa (and elsewhere) is due to heating during the summer. Air over land becomes warmer and rises, pulling in cool wet air from the ocean, which causes rain. Paradoxically, the Sahara was wetter when it received more solar insolation in the summer. In turn, changes all in solar insolation are caused by changes in the Earth's orbital parameters.
By around 3400 BC, the monsoon retreated south to approximately where it is today,leading to the desertification of the Sahara. The Sahara is currently as dry as it was about 13,000 years ago. These conditions are responsible for what has been called the Sahara Pump Theory.
The Sahara is known to have one of the harshest climates in the world. The prevailing north-easterly wind can often cause the sand to form tornadoes. Precipitation, while rare is not unknown. Half of the Sahara receives less than 2 cm of rain a year, with the rest receiving up to 10 cm a year.The rainfall happens very rarely, but when it does it is usually torrential when it occurs after long dry periods, which can last for years.
By around 3400 BC, the monsoon retreated south to approximately where it is today,leading to the desertification of the Sahara. The Sahara is currently as dry as it was about 13,000 years ago. These conditions are responsible for what has been called the Sahara Pump Theory.
The Sahara is known to have one of the harshest climates in the world. The prevailing north-easterly wind can often cause the sand to form tornadoes. Precipitation, while rare is not unknown. Half of the Sahara receives less than 2 cm of rain a year, with the rest receiving up to 10 cm a year.The rainfall happens very rarely, but when it does it is usually torrential when it occurs after long dry periods, which can last for years.
2008-12-06 5:32 am
撒哈拉大沙漠的氣候进行了在乾濕之間的極大的變異最後幾十萬年。 在最后冰河时期期間，撒哈拉大沙漠大于它今天，延伸南部在它的當前界限之外。冰河时期的结尾給撒哈拉大沙漠BC帶來了更好的时期，從大约8000到6000 BC，或許由于在崩溃的冰床的低压區域對北部。一旦冰床去，撒哈拉大沙漠的北部變乾了。 然而，在冰床之後的末端，當前帶來的季風雨向撒哈拉大沙漠來了进一步北部并且抵制了乾燥趨向在南撒哈拉大沙漠。 季風在非洲(和在別處)归结于加熱在夏天期間。 在土地的空氣成為取暖器和上升，拉扯在從海洋的涼快的濕空氣，導致雨。 似是而非地，當它在夏天，接受了更加太陽的日光浴撒哈拉大沙漠是更濕的。 反过来，在太陽日光浴上的变化全部由由大约3400 BC，季風撤退了南部對大約它今天的地方，导致撒哈拉大沙漠的沙漠化。 撒哈拉大沙漠當前是一样乾燥的，象大约13,000年前。 這些情况对什麼负责称撒哈拉大沙漠泵浦理論。 撒哈拉大沙漠在世界上知道有其中一最苛刻的氣候。 戰勝的东北风可能經常造成沙子形成龍捲風。 降雨雪，当罕見时不是未知的。 撒哈拉大沙漠的一半接受少于2 cm雨每年，当休息接受10 cm一年。降雨量很少發生，但是，当它做时它通常是滔滔的，当它在長的乾燥期間以后时發生，可能多年来持續。 似是而非地，當它在夏天，接受了更加太陽的日光浴撒哈拉大沙漠是更濕的。 反过来，在太陽日光浴上的变化全部由在地球的軌道參量上的变化造成。在地球的軌道參量上的变化造成。
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20081205000051KK01635