Misplaced Pages

#496503

64-508: The North Atlantic oscillation (NAO) is a close relative of the Arctic oscillation. There is debate over whether one or the other is more fundamentally representative of the atmosphere's dynamics. The NAO may be identified in a more physically meaningful way, which may carry more impact on measurable effects of changes in the atmosphere. The Arctic oscillation appears as a ringlike (or "annular") pattern of sea-level pressure anomalies centered at

128-594: A few of West Virginia's eastern panhandle counties are considered part of the Washington metropolitan area , the major portion of the state is rural and there are no major or even large cities. Shipping and trade have been important to the Mid-Atlantic economy since the beginning of the colonial era. The explorer Giovanni da Verrazzano was the first European to see the region in 1524. Henry Hudson later extensively explored that region in 1611 and claimed it for

192-410: A mechanism in which a shrinking summertime sea ice cover changes the air pressure zones in the Arctic atmosphere and effects on European winter weather. If there is a particularly large-scale melt of Arctic sea ice in summer, as observed in recent years, two important effects are intensified. Firstly, the retreat of the light ice surface reveals the darker ocean, causing it to warm up more in summer from

256-634: A negative phase of the NAO. This is thought to be the first study showing a link between NAO and terrestrial insects in North America. The NAO's ecological effects extend as far as the Tibetan Plateau , where increases in aridity resulting in significant forest mortality and intensification of dust storms have been linked to NAO- events. The winter of 2009–10 in Europe was unusually cold. It

320-688: A sub-region of the Northeast and only includes New Jersey, New York, and Pennsylvania. The Bureau of Labor Statistics excludes New York; the Environmental Protection Agency excludes New York and New Jersey; and the U.S. Department of Transportation - United States Maritime Administration includes North Carolina . In 2004, the United States Geological Survey within the context of Ground-Water Vulnerability to Nitrate Contamination, defined

384-521: A time, New Sweden along the Delaware River in Delaware , divided the two great bulwarks of English settlement from each other. The original English settlements in the region notably provided refuge to religious minorities, Maryland to Roman Catholics and Pennsylvania to Quakers and Anabaptist Pennsylvania Dutch . In time, all these settlements fell under English colonial control, but

448-602: Is a region of the United States located in the overlap between the Northeastern and Southeastern states of the United States . Its exact definition differs upon source, but the region typically includes New Jersey , Maryland , Virginia , Delaware , West Virginia , District of Columbia , and Pennsylvania . Some sources include New York , while others exclude Pennsylvania . However, according

512-550: Is also home to the nation's capital, Washington, D.C. The Mid-Atlantic is home to 33 professional sports franchises in the five major leagues and the two most prominent women's professional leagues: Notable golf tournaments in the Mid-Atlantic include the Barclays , Quicken Loans National and Atlantic City LPGA Classic . Two high-level professional tennis tournaments are held in the region. The US Open , held in New York,

576-528: Is based on the principal empirical orthogonal function (EOF) of surface pressure. This definition has a high degree of correlation with the station-based definition. This then leads onto a debate as to whether the NAO is distinct from the AO/NAM, and if not, which of the two is to be considered the most physically based expression of atmospheric structure (as opposed to the one that most clearly falls out of mathematical expression). Westerly winds blowing across

640-509: Is considered to be highly anomalous, and as extreme as the negative Arctic oscillation value itself. These negative values of the AO during 2010 and following into the next winter allowed colder air to penetrate much further south than usual into sub-tropical South Florida which brought record breaking low temperatures and months registered in many locations and the coolest average monthly minimum temperatures for February, March and December that year in

704-631: Is hypothesized that this may be due to a combination of low solar activity, a warm phase of the El Niño–Southern Oscillation and a strong easterly phase of the Quasi-Biennial Oscillation all occurring simultaneously. The Met Office reported that the UK, for example, had experienced its coldest winter for 30 years. This coincided with an exceptionally negative phase of the NAO. Analysis published in mid-2010 confirmed that

SECTION 10

#1732765945497

768-693: Is one of the four Grand Slam tennis tournaments, whereas the Washington Open is part of the ATP Tour 500 series and WTA 250 series. Notable motorsports tracks include Watkins Glen International , Dover Motor Speedway and Pocono Raceway , which have hosted Formula One , IndyCar , NASCAR , World Sportscar Championship and IMSA races. Also, the Englishtown and Reading drag strips such have hosted NHRA national events. Pimlico Race Course at Baltimore and Belmont Park at New York host

832-471: Is very representative of this increasing tendency: A further, quite graphic illustration of the effects of the negative phase of the oscillation occurred in February 2010. In that month, the Arctic oscillation reached its most negative monthly mean value at about −4.266, in the entire post-1950 era (the period of accurate record-keeping). That month was characterized by three separate historic snowstorms in

896-899: The Continental Congress , the convention of delegates who organized the American Revolution . Philadelphia also was the birthplace of the Declaration of Independence in 1776 and the United States Constitution in 1787, while the United States Bill of Rights was drafted and ratified and the first Supreme Court of the United States sat for the first time, in the first capital under the Constitution of New York . While early settlers were mostly farmers, traders, and fishermen,

960-467: The Gulf of Maine are affected by this reduced cod catch. The strength of the NAO is also a determinant in the population fluctuations of the intensively studied Soay sheep . Strangely enough, Jonas and Joern (2007) found a strong signal between NAO and grasshopper species composition in the tall grass prairies of the midwestern United States. They found that, even though NAO does not significantly affect

1024-674: The Preakness Stakes and Belmont Stakes horse races, which are part of the Triple Crown of Thoroughbred Racing . With a GDP nominal of over $ 5.2 trillion, the Mid-Atlantic economy would be third-largest in the world if calculated separately, only behind the remaining United States and China and nearly $ 1 trillion larger than next place Japan. This economic prosperity is buoyed by a significant financial services and banking sector, healthcare and chemicals industry, and telecommunications and entertainment conglomerates. According to

1088-611: The U.S. Bureau of Labor Statistics (BLS), the states listed above are commonly accepted as the Mid-Atlantic region. The region has its origin in the Middle Colonies of the 18th century when its states were among the Thirteen Colonies of pre- revolutionary British America . As of the 2020 census , the region had a population of 60,783,913, representing slightly over 18% of the nation's population. The Mid-Atlantic region played an instrumental and historic role in

1152-741: The University of Pennsylvania in Philadelphia ; Carnegie Mellon University in Pittsburgh ; Johns Hopkins University in Baltimore , Georgetown University in Washington, D.C. ; and the University of Virginia in Charlottesville, Virginia according to U.S. News & World Report Best Colleges Ranking . Definitions of the geographic components of the Mid-Atlantic region differ slightly among sources. Generally speaking,

1216-575: The mid-Atlantic region of the United States. The first storm precipitated 25 inches (640 mm) on Baltimore, Maryland on February 5–6, and a second storm precipitated 19.5 inches (500 mm) on February 9–10. In New York City, a separate storm deposited 20.9 inches (530 mm) on February 25–26. Another snowstorm swept Catalonia as well as neighbouring French departments ( Languedoc-Roussillon , Midi-Pyrenées ) on March 8, depositing 60 cm of snow in Girona . This kind of snowstorm activity

1280-405: The upper Midwest and New England , but the impact to the south of these areas is debatable. Conversely, when the NAO index is low (NAO-), the upper central and northeastern portions of the United States can incur winter cold outbreaks more than the norm with associated heavy snowstorms. In summer, a strong NAO- is thought to contribute to a weakened jet stream that normally pulls zonal systems into

1344-500: The 7-day mean Global Forecast System ensemble AO forecasts is approximately 0.9. This zonally symmetric seesaw between sea level pressures in polar and temperate latitudes was first identified by Edward Lorenz and named in 1998 by David W.J. Thompson and John Michael Wallace . The National Snow and Ice Data Center describes the effects of the Arctic oscillation in some detail. In the positive phase, higher pressure at midlatitudes drives ocean storms farther north, and changes in

SECTION 20

#1732765945497

1408-423: The Arctic oscillation loading pattern, which is defined as the first empirical orthogonal function (EOF) of monthly mean 1000 hPa geopotential height during the 1979-2000 period. The time series is then normalized with the monthly mean index's standard deviation . Over most of the past century, the Arctic oscillation alternated between positive and negative phases. Data using a 60-day running mean has implied

1472-399: The Arctic, as follows (note, however, that Hansen's explanation is erroneous: pressure in the Arctic is low in the positive AO phase, which configuration also enhances the jet stream): The degree to which Arctic air penetrates into middle latitudes is related to the AO index, which is defined by surface atmospheric pressure patterns. When the AO index is positive, surface pressure is high in

1536-472: The Atlantic Basin contributing significantly to excessively long-lasting heat waves over Europe, however, recent studies do not show the evidence of these associations. More recent studies have shown that the components (pressure centers strength, and locations) of the NAO are more powerful to investigate the relationships to seasonal and sub-seasonal climate variability over Europe, North America and

1600-665: The Atlantic bring moist air into Europe. In years when westerlies are strong, summers are cool, winters are mild and rain is frequent. If westerlies are suppressed, the temperature is more extreme in summer and winter leading to heat waves , deep freezes and reduced rainfall. A permanent low-pressure system over Iceland (the Icelandic Low ) and a permanent high-pressure system over the Azores (the Azores High ) control

1664-775: The Dutch, who then created a fur-trading post in Albany in 1614. Jamestown, Virginia was the first permanent English colony in North America, it was established seven years earlier in 1607. From early colonial times, the Mid-Atlantic region was settled by a wider range of European people than in New England or the South. The Dutch New Netherland settlement along the Hudson River in New York City and New Jersey , and for

1728-472: The Gulf coast during 3000–1400 BC and again during the most recent millennium. These quiescent intervals were separated by a hyperactive period during 1400 BC – 1000 AD, when the Gulf coast was struck frequently by catastrophic hurricanes and their landfall probabilities increased by 3–5 times. Until recently, the NAO had been in an overall more positive regime since the late 1970s, bringing colder conditions to

1792-470: The Mediterranean region. Under a positive NAO index (NAO+), regional reduction in atmospheric pressure results in a regional rise in sea level due to the 'inverse barometer effect'. This effect is important to both the interpretation of historic sea level records and predictions of future sea level trends, as mean pressure fluctuations of the order of millibars can lead to sea level fluctuations of

1856-617: The Mid-Atlantic states provided the young United States with heavy industry and served as the " melting pot " of new immigrants from Europe. Cities grew along major ports, shipping routes, and waterways, including New York City and Newark on opposite sides of the Hudson River , Philadelphia on the Delaware River, Allentown on the Lehigh River , and Baltimore on the Chesapeake Bay . Note: The Mid-Atlantic region

1920-643: The Mid-Atlantic, and 33 of the nation's top 100 counties based on per capita income are in the region. Most of the Mid-Atlantic states rank among the 15 highest-income states in the nation by both median household income and per capita income. The region is home to eight of the top 25 ranked universities in the nation: Cornell University in Ithaca, New York ; Columbia University and NYU in New York City; Princeton University in Princeton, New Jersey ;

1984-598: The NAO+ peak in the early 1990s may have contributed to the collapse of the Newfoundland cod fishery . In southwestern Europe, NAO- events are associated with increased aeolian activity. On the East Coast of the United States an NAO+ causes warmer temperatures and increased rainfall, and thus warmer, less saline surface water. This prevents nutrient-rich upwelling which has reduced productivity. Georges Bank and

Arctic oscillation - Misplaced Pages Continue

2048-631: The North Atlantic and surrounding humid climates. The North Atlantic Oscillation is closely related to the Arctic oscillation (AO) (or Northern Annular Mode (NAM)), but should not be confused with the Atlantic multidecadal oscillation (AMO). The NAO has multiple possible definitions. The easiest to understand are those based on measuring the seasonal average air pressure difference between stations, such as: These definitions all have in common

2112-602: The North-West Atlantic, which has been linked with the thriving populations of Labrador Sea snow crabs , which have a low temperature optimum. The NAO+ warming of the North Sea reduces survival of cod larvae which are at the upper limits of their temperature tolerance, as does the cooling in the Labrador Sea, where the cod larvae are at their lower temperature limits. Though not the critical factor,

2176-581: The Pacific Ocean, a largely positive North Atlantic Oscillation prevailed over Europe during the winter of 2015–2016. For example, Cumbria in England registered one of the wettest months on record. The Maltese Islands in the Mediterranean registered one of the driest years ever recorded up to beginning of March, with a national average of only 235 mm and some areas registering less than 200 mm. Mid-Atlantic states The Mid-Atlantic

2240-518: The United States . The nation's capital was constructed in Washington, D.C. in the late 18th century, and relocated there from Philadelphia in 1800. In the early part of the 19th century, New York and Pennsylvania overtook Virginia as the nation's two most populous states, and the Mid-Atlantic region overtook New England as the most important trading and industrial center in the nation. During this period, large numbers of German , Irish , Italian , Jewish , Polish , and other immigrants arrived in

2304-479: The air near to the ground leads to rising movements and the atmosphere becomes less stable. One of these patterns is the air pressure difference between the Arctic and mid-latitudes: the Arctic oscillation with the Azores highs and Iceland lows known from the weather reports. If this difference is high, a strong westerly wind will result which in winter carries warm and humid Atlantic air masses right down to Europe. In

2368-622: The circulation pattern bring wetter weather to Alaska , Scotland and Scandinavia , as well as drier conditions to the western United States and the Mediterranean . In the positive phase, frigid winter air does not extend as far into the middle of North America as it would during the negative phase of the oscillation. This keeps much of the United States east of the Rocky Mountains warmer than normal, but leaves Greenland and Newfoundland colder than usual. Weather patterns in

2432-504: The concurrent ' El Niño ' event and the rare occurrence of an extremely negative NAO were involved. However, during the winter of 2010–11 in Northern and Western Europe , the Icelandic Low , typically positioned west of Iceland and east of Greenland, appeared regularly to the east of Iceland and so allowed exceptionally cold air into Europe from the Arctic. A strong area of high pressure was initially situated over Greenland , reversing

2496-473: The direction and strength of westerly winds into Europe. The relative strengths and positions of these systems vary from year to year and this variation is known as the NAO. A large difference in the pressure at the two stations (a high index year, denoted NAO+) leads to increased westerlies and, consequently, cool summers and mild and wet winters in Central Europe and its Atlantic facade. In contrast, if

2560-560: The index is low (NAO-), westerlies are suppressed, northern European areas suffer cold dry winters and storms track southwards toward the Mediterranean Sea . This brings increased storm activity and rainfall to southern Europe and North Africa. Especially during the months of November to April, the NAO is responsible for much of the variability of weather in the North Atlantic region, affecting wind speed and wind direction changes, changes in temperature and moisture distribution and

2624-420: The intensity, number and track of storms. Research now suggests that the NAO may be more predictable than previously assumed and skillful winter forecasts may be possible for the NAO. There is some debate as to how much the NAO impacts short term weather over North America. While most agree that the impact of the NAO is much less over the United States than for Western Europe, the NAO is also believed to affect

Arctic oscillation - Misplaced Pages Continue

2688-636: The nation's founding and the development of the nation. Each of the seven states were members of the Thirteen Colonies that sent delegates to the Second Continental Congress , which assembled in Philadelphia and unanimously adopted the Declaration of Independence , and formalized the Continental Army under George Washington 's command during the American Revolutionary War . Following independence,

2752-558: The negative phase are in general "opposite" to those of the positive phase. Climatologists are now routinely invoking the Arctic oscillation in their official public explanations for extremes of weather. The following statement from the National Oceanic and Atmospheric Administration 's National Climatic Data Center : State of the Climate December 2010 which uses the phrase "negative Arctic Oscillation" four times,

2816-428: The negative phase when pressure differences are low, cold Arctic air can then easily penetrate southward through Europe without being interrupted by the usual westerlies. Model calculations show that the air pressure difference with decreased sea ice cover in the Arctic summer is weakened in the following winter, enabling Arctic cold to push down to mid-latitudes. Despite one of the strongest El Niño events recorded in

2880-403: The normal wind pattern in the northwestern Atlantic, creating a blocking pattern driving warm air into northeastern Canada and cold air into Western Europe, as was the case during the previous winter. This occurred during a La Niña season, and is connected to the rare Arctic dipole anomaly . In the north western part of the Atlantic, both of these winters were mild, especially 2009–2010, which

2944-592: The order of centimeters. By controlling the position of the Azores High, the NAO also influences the direction of general storm paths for major North Atlantic tropical cyclones : a position of the Azores High farther to the south tends to force storms into the Gulf of Mexico , whereas a northern position allows them to track up the North American Atlantic Coast. As paleotempestological research has shown, few major hurricanes struck

3008-611: The original Thirteen Colonies and were particularly prevalent in Province of Pennsylvania and the geographic region that ultimately broke from Pennsylvania to form the Delaware Colony . Among the 13 colonies, the Province of Maryland was the only colony with a substantial Catholic population. Following the American Revolutionary War, the Mid-Atlantic region hosted each of the historic capitals of

3072-433: The oscillation has been trending to more of a positive phase since the 1970s, though it has trended to a more neutral state in the last decade. The oscillation still fluctuates stochastically between negative and positive values on daily, monthly, seasonal and annual time scales, although meteorologists have attained high levels of predictive accuracy for shorter term forecasts. The correlation between actual observations and

3136-520: The polar region. This helps the middle latitude jet stream to blow strongly and consistently from west to east, thus keeping cold Arctic air locked in the polar region. When the AO index is negative, there tends to be low pressure in the polar region, weaker zonal winds, and greater movement of frigid polar air into middle latitudes." The Arctic oscillation index is defined using the daily or monthly 1000 hPa geopotential height anomalies from latitudes 20° N to 90° N. The anomalies are projected onto

3200-514: The poles. The presence of continents and large landmasses disrupts the ringlike structure at the Arctic pole, while anomalies surrounding the Antarctic pole are nearly circular. The Arctic oscillation is believed by climatologists to be causally related to (and thus partially predictive of) global weather patterns . NASA climatologist James E. Hansen explained the mechanism by which the Arctic oscillation affects weather at points so distant from

3264-639: The region as including Delaware, Maryland, Pennsylvania, Virginia, and Washington, D.C., and parts of New Jersey, New York, and North Carolina. West Virginia and Virginia are atypical of this region in a few ways. These states both primarily lie within the Southern American dialect region , and the major religious tradition is largely Evangelical Christian , with 30% in Virginia and 39% in West Virginia identifying as evangelicals. Although

SECTION 50

#1732765945497

3328-455: The region continued to be a magnet for people of diverse nationalities. The area that came to be known as the Middle Colonies served as a strategic bridge between the North and South. The New York and New Jersey campaign during the American Revolutionary War saw more battles than any other theater of the conflict. Philadelphia , midway between the northern and southern colonies, was home to

3392-579: The region is inclusive of the states of Delaware, Maryland, New Jersey, New York, Pennsylvania, Virginia, and West Virginia, and the federal district of the District of Columbia, with some additional sources including or excluding other areas in parts of the Northeast region and the South Atlantic states , for practical reasons. The United States Census Bureau defines the Mid-Atlantic as

3456-451: The region link an almost contiguous urban region, which includes large and small cities and their respective suburbs and forms the Northeast megalopolis , one of the world's most important concentrations of finance, media, communications, education , medicine, and technology. The Mid-Atlantic is a relatively affluent region of the nation; nearly half of the nation's 100 highest-income counties based on median household income are located in

3520-588: The region's coastal cities, including Baltimore , Newark , New York City , Philadelphia, and interior cities such as Pittsburgh , and Rochester , Albany , and Buffalo , with their skyscrapers and subways, which emerged as icons of modernity and American economic and cultural power in the 20th century. In the late 19th century, the region played a vital and historic role in the development of American culture , commerce, trade, and industry sectors . Historian Frederick Jackson Turner labeled it "typically American." The Northeast Corridor and Interstate 95 in

3584-505: The same northern point (because this is the only station in the region with a long record) in Iceland ; and various southern points. All are attempting to capture the same pattern of variation, by choosing stations in the "eye" of the two stable pressure areas, the Azores High and the Icelandic Low (shown in the graphic). A more complex definition, only possible with more complete modern records generated by numerical weather prediction ,

3648-403: The solar radiation ( ice–albedo feedback mechanism). Secondly, the diminished ice cover can no longer prevent the heat stored in the ocean being released into the atmosphere ( lid effect ). As a result of the decreased sea ice cover the air is warmed more greatly than it used to be particularly in autumn and winter because during this period the ocean is warmer than the atmosphere. The warming of

3712-712: The states again gathered in Philadelphia at the Constitutional Convention , in 1788, where they ratified the United States Constitution , which remains the oldest and longest-standing written and codified national constitution in force in the world. The Mid-Atlantic region was settled during the colonial era between the early 17th century and the conclusion of the American Revolutionary War in 1783 by European Americans of primarily Dutch , German , Swedish , English , and other Western European ethnicities. Religious pluralism and freedoms existed in

3776-453: The strength of the Icelandic Low and the Azores High, it controls the strength and direction of westerly winds and location of storm tracks across the North Atlantic. The NAO was discovered through several studies in the late 19th and early 20th centuries. Unlike the El Niño–Southern Oscillation phenomenon in the Pacific Ocean, the NAO is a largely atmospheric mode. It is one of the most important manifestations of climate fluctuations in

3840-433: The time between 1950 and 2010, nine of the ten coldest Januarys in New York City since 1950 have coincided with negative Arctic oscillations. North Atlantic oscillation The North Atlantic Oscillation ( NAO ) is a weather phenomenon over the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High . Through fluctuations in

3904-424: The tropical beach getaway of Cancún , up to over 4C below the climate period averages. The greatest negative value for the Arctic oscillation since 1950 in January was −3.767 in 1977, which coincided with the coldest mean January temperature in New York City, Washington, D.C., Baltimore, and many other mid-Atlantic locations in that span of time, although the January Arctic oscillation has been negative only 60.6% of

SECTION 60

#1732765945497

3968-491: The weather in the midwest, there was a significant increase in abundance of common grasshopper species (i.e. Hypochlora alba, Hesperotettix spp., Phoetaliotes nebrascensis, M. scudderi, M. keeleri, and Pseudopomala brachyptera ) following winters during the positive phase of NAO and a significant increase in the abundance of less common species (i.e. Campylacantha olivacea, Melanoplus sanguinipes, Mermiria picta, Melanoplus packardii, and Boopedon gracile ) following winters during

4032-429: The weather over much of upper central and eastern areas of North America. During the winter, when the index is high (NAO+), the Azores High draws a stronger south-westerly circulation over the eastern half of the North American continent which prevents Arctic air from plunging southward (into the United States south of 40 latitude). In combination with the El Niño , this effect can produce significantly warmer winters over

4096-411: Was the warmest recorded in Canada. The winter of 2010-2011 was particularly above normal in the northern Arctic regions of that country. The probability of cold winters with much snow in Central Europe rises when the Arctic is covered by less sea ice in summer. Scientists of the Potsdam Research Unit of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association have decrypted

#496503