Knowledge Nugget: How is ‘Pineapple Express’ relevant to the UPSC Exam?
Pineapple Express has drenched Northern California in the last few days—but what exactly is it? How common is it? Also, go 'Beyond the Nugget' to learn about the polar vortex and the Santa Ana winds.
Atmospheric rivers vary in size and intensity, but those with the highest water vapour content and strongest winds can bring extreme rainfall and flooding, according to the National Oceanic and Atmospheric Administration (NOAA). (Reuters/File Photo)
Take a look at the essential events, concepts, terms, quotes, or phenomena every day and brush up your knowledge. Here’s your knowledge nugget for today.
Knowledge Nugget: Pineapple Express
Subject: Geography
(Relevance: Geographical phenomena are an important part of the UPSC syllabus. UPSC has previously asked questions on such topics. Therefore, understanding the ‘Pineapple Express’ is essential for your upcoming UPSC CSE Prelims.)
Why in the news?
Following an unusually dry January, a powerful atmospheric river known as the ‘Pineapple Express’ has been sweeping through northern and central California, bringing periods of strong winds, heavy rain, and snowfall in the hills. It is expected that by Wednesday, the storm will weaken, potentially bringing lighter rainfall to southern California, including Los Angeles.
Key Takeaways :
The Pineapple Express is a narrow region of atmospheric moisture that builds up in the tropical Pacific.-National Oceanic and Atmospheric Administration (NOAA)
1. As per a report by BBC, the Pineapple Express is a type of atmospheric river— a narrow, fast-moving “river in the sky” that transports significant moisture over long distances. The warm air and high humidity it carries from the Pacific lead to heavy rainfall when the system reaches land.
2. Pineapple Express gets its name from the warm, moist air drawn into the system, originating near Hawaii, a region known for its pineapple production.
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3. The NOAA explains that atmospheric rivers are long, narrow bands in the atmosphere that transport vast amounts of water vapour from the tropics. Their size and strength can differ significantly, but on average, they carry a volume comparable to the flow of the Mississippi River at its mouth. Exceptionally strong atmospheric rivers can transport up to 15 times that amount.
4. When atmospheric rivers make landfall, they typically release this moisture as rain or snow, often covering a vast region as they move inland.
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5. According to NOAA, these rivers are part of the Earth’s ocean water cycle, and are tied closely to both water supply and flood risks. While atmospheric rivers can bring heavy rainfall that may lead to flooding, they also play a beneficial role in increasing snowpack.
Is the “Pineapple Express” a common weather phenomenon?
1. The atmospheric rivers in the sky occur often on the West Coast but can happen in other locations, including the eastern United States, where they often channel moisture from the Caribbean.
2. When this moisture begins to interact with land, it can fall as rain or snow. Although atmospheric rivers come in different shapes and sizes, for one to be a “true Pineapple Express,” location matters. The tail end, where the moisture is pulled into the atmosphere, must start near Hawaii. Then the river must stretch continuously through the atmosphere to the US West Coast.
3. Scientists warn that climate change may intensify these systems in the future, increasing lower-elevation rainfall, flooding risks, and storm severity.
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BEYOND THE NUGGET: Polar Vortex and Santa Ana Winds
1. The polar vortex is a large area of low pressure and cold air that rotates around both of the Earth’s polar regions. There are two types of polar vortex: the tropospheric polar vortex and the stratospheric polar vortex.
A pedestrian crosses a street with the US Capitol building in distance, as a winter storm that brought snow, ice and freezing temperatures to a broad swath of the US arrived in Washington, US on January 6, 2025. (Photo: Reuters)
2. The tropospheric polar vortex occurs in the lowest layer of the atmosphere, extending from the surface up to about 10 to 15 kilometers high. This is where most weather phenomena take place.
3. The stratospheric polar vortex exists at altitudes of approximately 15 to 50 kilometers. Unlike the tropospheric polar vortex, the stratospheric version disappears during the summer and is strongest during the autumn.
1. Santa Ana winds are a natural part of California’s climate pattern and normally blow from October to January. These winds blow when high pressure builds over the Great Basin (region located between the Rocky Mountains and the Sierra Nevada) while a low-pressure system develops over California’s coast.
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2. The difference in pressure creates strong winds that blow from the inland deserts of the Basin toward the east and north of Southern California, ultimately moving towards the Pacific Ocean.
3. As the wind comes down the mountains, it compresses and heats up, and its humidity falls — sometimes to less than 10%.
(Sources: What is Pineapple Express, an atmospheric ‘river’ set to bring heavy rains to California, Santa Ana Winds, oceanservice.noaa.gov, Winter storm in the US: How is the polar vortex responsible for it?)
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Roshni Yadav is a Deputy Copy Editor with The Indian Express. She is an alumna of the University of Delhi and Jawaharlal Nehru University, where she pursued her graduation and post-graduation in Political Science. She has over five years of work experience in ed-tech and media. At The Indian Express, she writes for the UPSC section. Her interests lie in national and international affairs, governance, economy, and social issues. You can contact her via email: roshni.yadav@indianexpress.com ... Read More
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