Low Pressure Atmospheric Systems

Low pressure atmospheric systems are also known as depressions or cyclones and they form in mid- and high-latitudes. They are formed by the mixing of cold and warm air, the warm air is lighter, so it rises above the denser, cold air and forms a centre of low pressure. High pressure atmospheric systems are also known as anticyclones and have very different characteristics to depressions. Anticyclones are large masses of subsiding air, which produces high pressure at the surface.There are a variety of difference between anticyclones and depressions, including the weather conditions, the length of time they last and the impact they have upon diverse countries and areas. Low pressure atmospheric systems can cause hazards because of severe weather such as blizzards and heavy snowfall, as well as high winds and heavy rainfall. This can have harsh impacts among individuals, being a lead cause of hypothermia, and frostbite, especially those vulnerable, such as the elderly. Also, these depres sions can cause crops to be destroyed, and a high mortality rate throughout the spring lambing season.Extreme cold spells can have a massive negative effect on a global scale, but also in a specific country or region. High pressure atmospheric systems affect the globe, especially the southern hemisphere, as it is nearly always continuous, although in places such as Australia and South Africa, this is broken throughout their summer. With anticyclones, there are few winds, so maps usually have circular spaced out isobars. Also, these atmospheric systems block depressions, which mean that their impacts are usually long-term, because they are constant. Weather associated with anticyclones differentiates depending on the time of year.In summer, anticyclones produce long periods of dry, hot, sunny weather, which can then cause heat waves and drought. However, in winter the cloudless nights mean that temperatures drop, and does not recover the next day because of weak sunshine and lingerin g fog. The impacts of anticyclones and depressions vary, as does the period they remain and the effect they have. The North American blizzard of 2003 lasted for five days throughout February and occurred on the East Coast of the USA and Canada. It was a record-breaking blizzard, which caused 27 deaths and over $14 million worth of damage.The cities in America were bought to a standstill, as there was a range of 38-76cm of snow covering the ground. The cause for such an unusually extreme blizzard was the fact that the conditions were favourable, with moisture from the Atlantic Ocean enhancing precipitation and a high pressure system over Canada, allowing cold air to be brought down coastal areas. This meant that the precipitation was mainly snow, hence the record-breaking statistics. The effects this storm had were mainly short-term, but the roof of the historic Railroad Museum collapsed and 27 people lost their lives.Additionally, transport infrastructure was brought to a halt, and three major airports were also closed. So, the impacts of depressions are mainly short-term, although the destruction can be horrendous, whereas, anticyclones usually cause long-term impacts on a country such as the Drought in Britain and Europe in 2003. This drought effected many locations, but the main focus was on the UK, France and Portugal. Not all impacts are negative, as the heat wave did boost the tourist industry in most countries and sales for summer items such as barbeques and sun cream increased, but this positive outlook is short-lived.In the UK, an estimated 200 people lost their lives due to poor air quality, and this figure was 10% higher than the average. Furthermore, transport was disrupted because of roads melting at such high temperatures, and the London Underground was 37Â °, which is over the legal limit to transport animals. Finally, in the UK the cost of people taking days off work to enjoy the hot weather was between ?7. 5million and ?10million per day. In France, the death toll was as high as 30,000 and harvests were down by 30 to 50% on 2002.Additionally, the nuclear power plants could not produce the soaring demands for energy, which was used for refrigerators and air conditioning, because there was less water available for cooling. Portugal declared a State of Emergency after the worst forest fires in 30 years. Approximately 35,000 hectares of forest, farmland and scrub was burned, and 1300 people died. 80 families were forced to abandon their homes, and arsonists begun deliberately causing fires, to gain compensation. The impacts of anticyclones on all of these countries had a massive effect, and it lasted over a month, with the hottest temperatures for up to 500 years.This demonstrates the long and short term impacts that anticyclones have on regions, countries and on a global scale. Location does have a result on the impact of low and high atmospheric pressure systems because they can be underdeveloped or have a lot of technolo gy that can be damaged or ruined. MEDC’s usually lose fewer lives than LEDC’s, no matter if it is a depression or a cyclone. Also, the evidence seems to suggest that depressions have a shorter impact on an area than anticyclones, but this is not necessarily true.Long-term secondary hazards can be a large issue after a depression, as the damage from flooding or heavy snow can be excessive and highly damaging. I conclude, low pressure atmospheric systems do usually have shorter-term impacts on a location, rather than high pressure atmospheric systems, but the secondary hazards can be a long-term issue for both of these hazards. Furthermore, the impact they have, may be different, depending on location, because a LEDC will be severely affected by both of these hazards, and will most likely have long-term consequences.