Heat Dome-Do You Know the Reason for Excessive Heat in USA & Canada? Geography YouTube Lecture Handouts

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Heat Dome - Do You Know the Reason for Excessive Heat in USA & Canada? Geography | Earth Sciences
  • High-pressure circulation in the atmosphere acts like a dome or cap, trapping heat at the surface and favoring the formation of a heat wave.
  • Summertime means hot weather — sometimes dangerously hot — and extreme heat waves have become more frequent in recent decades. Sometimes, the scorching heat is ensnared in what is called a heat dome. This happens when strong, high-pressure atmospheric conditions combine with influences from La Nina, creating vast areas of sweltering heat that gets trapped under the high-pressure “dome.”
  • The Pacific Ocean waters are cooler in the eastern Basin during La Nina and warmer in the western Pacific Basin.
  • When this circulation happens, the temperature difference creates winds that blow the tropical air mass from west to east and the weather pattern gets this air trapped in the jet stream which ends up across the western portions of North America. This summer, neutral El Niño/La Niña Southern Oscillation (ENSO) is in effect

Reasons for Heat Dome

  • Strong change (or gradient) in ocean temperatures from west to east in the tropical Pacific Ocean during the preceding winter.
  • Imagine a swimming pool when the heater is turned on — temperatures rise quickly in the areas surrounding the heater jets, while the rest of the pool takes longer to warm up. If one thinks of the Pacific as a very large pool, the western Pacific՚s temperatures have risen over the past few decades as compared to the eastern Pacific, creating a strong temperature gradient, or pressure differences that drive wind, across the entire ocean in winter. In a process known as convection, the gradient causes more warm air, heated by the ocean surface, to rise over the western Pacific, and decreases convection over the central and eastern Pacific.
  • As prevailing winds move the hot air east, the northern shifts of the jet stream trap the air and move it toward land, where it sinks, resulting in heat waves.
Reasons for Heat Dome