What is behind the heatwaves affecting the United States?

What is behind the heatwaves affecting the United States?

Subject : Geography

Section :Climatology

Context: Virtually all the contiguous United States experienced above normal temperatures in the past week, with more dangerously hot weather forecast

What is a Heat Wave?

The World Meteorological Organization defines it as five or more consecutive days during which the daily maximum temperature surpasses the average maximum temperature by 5 °C (9 °F) or more.

The India Meteorological Department requires that temperatures increase 5–6 °C (9–10.8 °F) or more above the normal temperature

Factors behind the heatwaves in US:

• The Arctic is warming three to four times faster than the globe as a whole, meaning there is ever less difference between northern temperatures and those closer to the equator
• That is resulting in swings in the North Atlantic jet stream, which in turn leads to extreme weather events like heatwaves and floods
• Warmer oceans contribute to heat domes, which trap heat over large geographical areas. This weekend the heat dome is stretching from the southern plains of the Oklahoma/Arkansas area all the way to the eastern seaboard
• The main cause of heat domes is a strong change in ocean temperatures from west to east in the tropical Pacific Ocean during the preceding winter
• 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 heatwaves
• Another factor is El Nino and La Nina. El Niño brings warm water from the equatorial Pacific Ocean up to the western coast of North America, and La Niña brings colder water.
• At present, La Niña is in effect. Because summer temperatures trend lower during La Niña. during the next El Niño a serious heatwave even hotter summer weather could be expected.
• Climate change caused by the burning of fossil fuels is a global phenomenon that is certainly playing a role
• Heatwaves are probably the most underestimated type of potential disaster because they routinely kill a lot of people

Concept:

What are Jet Streams?

• Jet streams are relatively narrow bands of strong wind in the upper levels of the atmosphere. The winds blow from west to east in jet streams but the flow often shifts to the north and south. Jet streams follow the boundaries between hot and cold air.
• These hot and cold air boundaries are most pronounced in winter, jet streams are thestrongest for both the northern and southern hemisphere winters.
• The earth’s rotation is responsible for the jet stream.
• The actual appearance of jet streams result from the complex interaction between many variables – such as the location of high and low pressure systems, warm and cold air, and seasonal changes.