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Jet streams are fast flowing, narrow, meandering air currents in the atmospheres of the Earth, Venus, Jupiter, Saturn, Uranus, and Neptune. On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds. Jet streams may start, stop, split into two or more parts, combine into one stream, or flow in various directions including opposite to the direction of the remainder of the jet.
Extreme weather includes unexpected, unusual, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Extreme events are based on a location's recorded weather history. They are defined as lying in the most unusual ten percent. The main types of extreme weather include heat waves, cold waves and heavy precipitation or storm events, such as tropical cyclones. The effects of extreme weather events are economic costs, loss of human lives, droughts, floods, landslides. Severe weather is a particular type of extreme weather which poses risks to life and property.
A heat wave ), sometimes known as extreme heat, is a period of abnormally hot weather. High humidity often accompanies heat waves. This is especially the case in oceanic climate countries. Definitions vary but are similar. We usually measure a heat wave relative to the usual climate in the area and to normal temperatures for the season. Temperatures that people from a hotter climate consider normal can be called a heat wave in a cooler area. This would be the case if the warm temperatures are outside the normal climate pattern for that area. Heat waves have become more frequent, and more intense over land, almost everywhere since the 1950s. This is due to climate change.
A circumpolar vortex, or simply polar vortex, is a large region of cold, rotating air that encircles both of Earth's polar regions. Polar vortices also exist on other rotating, low-obliquity planetary bodies. The term polar vortex can be used to describe two distinct phenomena; the stratospheric polar vortex, and the tropospheric polar vortex. The stratospheric and tropospheric polar vortices both rotate in the direction of the Earth's spin, but they are distinct phenomena that have different sizes, structures, seasonal cycles, and impacts on weather.
Blocks in meteorology are large-scale patterns in the atmospheric pressure field that are nearly stationary, effectively "blocking" or redirecting migratory cyclones. They are also known as blocking highs or blocking anticyclones. These blocks can remain in place for several days or even weeks, causing the areas affected by them to have the same kind of weather for an extended period of time. In the Northern Hemisphere, extended blocking occurs most frequently in the spring over the eastern Pacific and Atlantic Oceans. Whilst these events are linked to the occurrence of extreme weather events such as heat waves, particularly the onset and decay of these events is still not well captured in numerical weather forecasts and remains an open area of research.
Polar amplification is the phenomenon that any change in the net radiation balance tends to produce a larger change in temperature near the poles than in the planetary average. This is commonly referred to as the ratio of polar warming to tropical warming. On a planet with an atmosphere that can restrict emission of longwave radiation to space, surface temperatures will be warmer than a simple planetary equilibrium temperature calculation would predict. Where the atmosphere or an extensive ocean is able to transport heat polewards, the poles will be warmer and equatorial regions cooler than their local net radiation balances would predict. The poles will experience the most cooling when the global-mean temperature is lower relative to a reference climate; alternatively, the poles will experience the greatest warming when the global-mean temperature is higher.
More than 1,030 people were killed in the 2002 heatwave in South India. Most of the dead were poor and elderly and a majority of deaths occurred in the southern state of Andhra Pradesh. In the districts that were impacted most, the heat was so severe that ponds and rivers evaporated and in those same districts birds had fallen from the sky and animals were collapsing from the intense heat.
The 1906 British Isles heatwave occurred across the British Isles in August and September 1906. The heat wave had a comparable intensity to the 1990 heat wave. From 31 August to 3 September, the temperature in the UK exceeded 32 °C (90 °F) consecutively over much of the UK. In September, Central England and Birmingham recorded a maximum temperature of 31.5 °C (88.7 °F), while Oxford recorded a maximum temperature of 33.1 °C (91.6 °F).
The 2010 Northern Hemisphere summer heat waves included severe heat waves that impacted most of the United States, Kazakhstan, Mongolia, China, Hong Kong, North Africa and the European continent as a whole, along with parts of Canada, Russia, Indochina, South Korea and Japan during May, June, July, and August 2010. The first phase of the global heatwaves was caused by a moderate El Niño event, which lasted from June 2009 to May 2010. The first phase lasted only from April 2010 to June 2010, and caused only moderate above average temperatures in the areas affected. But it also set new record high temperatures for most of the area affected, in the Northern Hemisphere. The second phase was caused by a very strong La Niña event, which lasted from June 2010 to June 2011. According to meteorologists, the 2010–11 La Niña event was one of the strongest La Niña events ever observed. That same La Niña event also had devastating effects in the Eastern states of Australia. The second phase lasted from June 2010 to October 2010, caused severe heat waves, and multiple record-breaking temperatures. The heatwaves began in April 2010, when strong anticyclones began to develop, over most of the affected regions, in the Northern Hemisphere. The heatwaves ended in October 2010, when the powerful anticyclones over most of the affected areas dissipated.
The 2013 extreme weather events included several all-time temperature records in Northern and Southern Hemisphere. The February extent of snow cover in Eurasia and North America was above average, while the extent of Arctic ice in the same month was 4.5% below the 1981–2010 average. The Northern Hemisphere weather extremes have been linked to the melting of Arctic sea ice, which alters atmospheric circulation in a way that leads to more snow and ice.
The 2018 Britain and Ireland heatwave was a period of unusually hot weather that took place in June, July and August. It caused widespread drought, hosepipe bans, crop failures, and a number of wildfires. These wildfires worst affected northern moorland areas around the Greater Manchester region, the largest was at Saddleworth Moor and another was at Winter Hill, together these burned over 14 square miles (36 km2) of land over a period of nearly a month.
The 2018 European drought and heat wave was a period of unusually hot weather that led to record-breaking temperatures and wildfires in many parts of Europe during the spring and summer of 2018. It is part of a larger heat wave affecting the northern hemisphere, caused in part by the jet stream being weaker than usual, allowing hot high-pressure air to linger in the same place. According to the European Drought Observatory, most of the areas affected by drought are across northern and central Europe. According to the World Meteorological Organization, the severe heat waves across the northern hemisphere in the summer of 2018, are linked to climate change in Europe, as well as events of extreme precipitation.
In late June and late July 2019 there were two temporally distinct European heat waves, which set all-time high temperature records in Belgium, France, Germany, Luxembourg, the Netherlands, and the United Kingdom.
The 2021 Western North America heat wave was an extreme heat wave that affected much of Western North America from late June through mid-July 2021. Extreme event attribution found this was a 1000-year weather event, made 150 times more likely by climate change. A study in Nature Climate Change estimated that its occurrence, while previously thought virtually impossible, has become an event that may occur every 200 years under current climate warming. The heat wave affected Northern California, Idaho, Western Nevada, Oregon, and Washington in the United States, as well as British Columbia, and in its latter phase, Alberta, Manitoba, the Northwest Territories, Saskatchewan, and Yukon, all in Canada. It also affected inland regions of Central and Southern California, Northwestern and Southern Nevada and parts of Montana, though the temperature anomalies were not as extreme as in the regions farther north.
In 2022, several areas of the world experienced heat waves. Heat waves were especially notable in East Asia, the Indian subcontinent, Australia, western Europe, the United States, and southern South America. 2022 heat waves accounted for record-breaking temperatures and, in some regions, heat-related deaths. Heat waves were worsened by the effects of climate change, and they exacerbated droughts and wildfires.
The 2022 United Kingdom heatwaves were part of several heatwaves across Europe and North Africa. The United Kingdom experienced three heatwaves; the first was for three days in June, the second for three days in July, and the third for six days in August. These were periods of unusually hot weather caused by rising high pressure up from the European continent. There were also more grass fires and wildfires than average, and in August a drought was declared in many regions.
From June to August 2022, persistent heatwaves affected parts of Europe, causing evacuations and between 24,501 and 61,672 heat-related deaths, making these heat waves the deadliest meteorological events in 2022. The highest temperature recorded was 47.0 °C (116.6 °F) in Pinhão, Portugal, on 14 July.
From June to 31 August 2022, China had a severe heat wave which affected several provinces and municipalities. To date, it is the country's worst heat wave to have existed. According to weather historian Maximiliano Herrera, it is the most severe heat wave recorded anywhere in the world.
A number of heat waves began across parts of the northern hemisphere in April 2023, many of which are ongoing. Various heat records have been broken, with July being the hottest month ever recorded.
References
- ↑ "Media reaction: The 2018 summer heatwaves and climate change". Carbon Brief. 26 July 2018. Retrieved 8 August 2018.
- ↑ John Schwartz and Nadia Popovich, 'New York Times,' "2018 Continues Warming Trend, As 4th Hottest Year Since 1880," February 7, 2019 p. 1
- ↑ Coghlan, Andy (24 July 2018). "Warming Arctic could be behind heatwave sweeping northern hemisphere". New Scientist. Retrieved 8 August 2018.
This heatwave across much of the northern hemisphere could continue for weeks, and possibly even months. Accelerated warming in the Arctic compared to the rest of the planet could be a key contributor. The heatwaves have killed dozens in Japan and Korea, have triggered wildfires in California and Sweden, and have led to prolonged dry weather in the UK and across northern Europe, raising temperatures beyond 30°C in Scandinavian sectors of the Arctic Circle. In Greece, the deadliest wildfires in more than a decade have claimed at least 74 lives. "It could persist for weeks, potentially for months," a spokesperson for the UK Meteorological Office told New Scientist.
- ↑ "Crazy weather traced to Arctic's impact on jet stream". New Scientist. Retrieved 8 August 2018.
The rapid retreat of Arctic sea ice caused by climate change may be to blame for more frequent prolonged spells of extreme weather in Europe, Asia and North America, such as heat waves, freezing temperatures or storms. ... They are related to "stuck" weather patterns, Jennifer Francis of Rutgers University in New Brunswick, New Jersey, told a conference on Arctic sea ice reduction in London on 23 September. "Is it global warming? I think it's safe to answer yes," she told the meeting.
- ↑ "July sees extreme weather with high impacts". World Meteorological Organization (WMO). Retrieved 14 August 2018.
- ↑ Somini Sengupta, Somini (14 August 2018). "2018 will be fourth-hottest year on record, climate scientists predict" . The Independent. Archived from the original on 1 May 2022. Retrieved 14 August 2018.