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WonderWeather system fact

Atmospheric rivers are long, narrow bands of moist air that carry huge amounts of water vapour, often from the tropics. When mountains force them upward over land, the vapour cools and falls as heavy rain or snow.

Atmospheric river

ClimateScienceNature

The story behind the card

Researchers Reginald Newell and Yong Zhu of the Massachusetts Institute of Technology named them in the early 1990s, after finding that much of the water vapour moving through the atmosphere travels in a few narrow plumes, typically thousands of kilometres long but only a few hundred wide. A single strong one can carry more water, as vapour, than the Amazon carries as liquid. Those that reach the west coast of North America from the tropical Pacific near Hawaii are nicknamed the Pineapple Express. They bring much of California's rain and snow, and also many of its worst floods. Since 2019, scientists at the Scripps Institution of Oceanography have ranked them on a five-level scale, from weak and mainly beneficial to exceptional and mainly hazardous, based on how much vapour they carry and how long they last.

Türkçe oku
Atmosferik nehirler, çoğu zaman tropiklerden büyük miktarda su buharı taşıyan uzun ve dar nem kuşaklarıdır. Karada dağlara çarpıp yükseldiklerinde buhar soğur ve şiddetli yağmur ya da kar olarak yere iner.

Adı 1990'ların başında, Massachusetts Teknoloji Enstitüsü'nden (MIT) araştırmacılar Reginald Newell ve Yong Zhu tarafından konuldu. İkili, atmosferdeki su buharının büyük kısmının birkaç dar şerit hâlinde taşındığını fark etmişti; bu şeritler genellikle binlerce kilometre uzunluğunda, ama yalnızca birkaç yüz kilometre genişliğindedir. Güçlü bir atmosferik nehir, buhar olarak, Amazon Nehri'nin taşıdığından daha fazla su taşıyabilir. Hawaii yakınlarındaki tropik Pasifik'ten Kuzey Amerika'nın batı kıyısına ulaşanlara “Ananas Ekspresi” denir. Kaliforniya'nın yağmurunun ve karının büyük kısmını bunlar getirir, en ağır sellerinin çoğunu da. Scripps Oşinografi Enstitüsü'ndeki bilim insanları 2019'dan beri bu nehirleri beş basamaklı bir ölçekle sınıflandırıyor: taşıdıkları buhara ve ne kadar sürdüklerine göre zayıf ve çoğunlukla yararlıdan, olağanüstü ve çoğunlukla tehlikeliye kadar.

Sources and further reading

Background reading: Atmospheric river
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