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Topic: North Atlantic Oscillation

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	North Atlantic Oscillation part of the global picture
		The NAO is best known as a pressure difference between the air over Iceland and the air over the Azores — located in the middle of the Atlantic on a latitude with Lisbon, Portugal.
		The NAO occurs in the tropopause, the areas of the atmosphere between the troposphere and the stratosphere at between 7 to 10 miles above the Earth's surface.
		In the Atlantic, they found that the stream sometimes moves in a breaking wave pattern and is oriented either from the northwest to the southeast or from the southwest to the northeast.
	www.eurekalert.org /pub_releases/2002-12/ps-nao120202.php (724 words)

	Met Office: Statistical prediction of the winter NAO
		When the NAO is in a negative phase westerly winds are weaker or less persistent, northern Europe tends to be colder and drier and southern Europe warmer and wetter than average.
		One of the simplest NAO indices is the winter difference in pressure at sea level between the Azores and Iceland.
		The NAO index used here is slightly different from the simple difference in surface pressures between the Azores and Iceland but the two time-series are quite similar with a correlation of 0.89.
	www.metoffice.gov.uk /research/seasonal/regional/nao/index.html (599 words)

	Solar Eruptions Linked to North Atlantic Oscillation
		The NAO index is defined as the normalized pressure difference between stations on the Azores and Iceland.
		A wider lag in the North Atlantic is acceptable as its location is far north of the equator where El Niño and La Niña develop in a climate with a much higher energy potential.
		The connection of a and d with NAO minima and maxima was interrupted and switched to midpoints a/d and d/a which replaced phases a and d.
	www.john-daly.com /theodor/solarnao.htm (5004 words)

	Statistics of North Atlantic Oscillation Decadal Variability
		The statistical significance of the lag-correlation and spectrum of a timeseries of the wintertime strength of the North Atlantic Oscillation is examined.
		The NAO pattern must interact with a system posessing interannual memory (such as the ocean) to produce this lag-correlation, but there is apparently no need to invoke resonant atmosphere-ocean modes or other coupled feedbacks involving active ocean dynamics to explain peaks in the NAO spectrum.
		The wintertime NAO index shows definite one-year lag-correlation, suggesting the atmosphere of the North Atlantic is in communication with a system posessing interannual memory (most likely the ocean.) However, spectral analysis of the timeseries shows it is consistent with a simple autoregressive AR(1) process.
	www.mit.edu /people/goodmanj/NAOI/index.html (1856 words)

	The North Atlantic Oscillation
		This oscillation, the North Atlantic Oscillation (NAO), is measured by the difference between pressures at two places at much the same longitude but widely separate latitudes (Iceland and the Azores), whilst the SOI refers to pressures at low-latitude places of different longitude.
		More correctly, the NAO Index is the normalized anomaly of the 500 hPa height difference between the Azores at 39° N and Iceland at 64° N, both around 24° W. A low NAO index implies a weak upper-level westerly winds in the North Atlantic, i.e.
		These longer-term NAO index variations are intimately connected with alterations of currents and the thermohaline circulation in the northern Atlantic ocean.
	www-das.uwyo.edu /~geerts/cwx/notes/chap12/nao.html (847 words)

	The North Atlantic Oscillation
		The NAO is the dominant mode of atmospheric variability in the North Atlantic sector throughout the year, but it is most pronounced during the winter season.
		The NAO exerts a dominant influence on wintertime temperature and precipitation across the North Atlantic basin and thus has major impacts on marine and terrestrial ecosystems.
		The changes in the mean circulation patterns over the North Atlantic are accompanied by pronounced shifts in the storm tracks and associated synoptic eddy activity which affect the transport and convergence of atmospheric moisture and can, therefore, be directly tied to changes in regional precipitation.
	www.iabm.org /north_atlantic_oscillation.htm (1719 words)

	ACCP Newsletter
		The NAO is the principal mode of North Atlantic annual to decadal climate variability (McCartney 1996, Rogers 1990).
		The NAO link with tree rings is a consequence of the significant relationships between the NA O and temperature, precipitation and storm track trajectories over the land areas surrounding the North Atlantic (e.g., Rogers and Van Loon 1979, Kushnir 1996, Cullen and DeMenocal submitted).
		The SENA pattern (which i s similar to the NAO) is associated with an opposition in winter temperature anomalies between the regions of Greenland and northern Europe, as indicated in both the index and reconstruction plots in Figure 1.
	www.aoml.noaa.gov /phod/accp/se97/rosanne_sep_97.htm (1449 words)

	Encyclopedia: North Atlantic Oscillation (Site not responding. Last check: )
		The Arctic oscillation (AO) is the dominant pattern of non-seasonal sea-level pressure (SLP) variations north of 20N, and it is characterized by SLP anomalies of one sign in the Arctic and anomalies of opposite sign centered about 37-45N.
		The North Atlantic oscillation (NAO) is a close relative...
		The Mediterranean Sea is a part of the Atlantic Ocean almost completely enclosed by land, on the north by Europe, on the south by Africa, and on the east by Asia.
	www.nationmaster.com /encyclopedia/North-Atlantic-Oscillation (570 words)

	NOAA News Online (Story 2403)
		On the minds of many in the East, "Where is it all coming from?" Scientists at the NOAA Climate Prediction Center have isolated the negative phase of the North Atlantic Oscillation, or NAO, as a major contributing factor to this late-season winter weather.
		A negative phase of the NAO and a southward shift of the North Atlantic jet stream sometimes means more frequent winter storms for the eastern United States, as has been observed in past weeks.
		The negative NAO is a key factor in sustaining cold air in the northeast U.S., which allows precipitation to reach the ground as snow rather than rain, when a major storm is affecting the East Coast," he added.
	www.noaanews.noaa.gov /stories2005/s2403.htm (725 words)

	Tiempo Climate Portal, North Atlantic Oscillation
		The North Atlantic Oscillation is a major disturbance of the atmospheric circulation and climate of the North Atlantic-European region, linked to a waxing and waning of the dominant middle-latitude westerly wind flow during winter.
		The North Atlantic Oscillation Index is based on the pressure difference between various stations to the north (Iceland) and south (Azores) of the middle latitude westerly flow.
		When the North Atlantic Oscillation Index is positive, the westerly flow across the North Atlantic and western Europe is enhanced, along with the Iceland Low and the Azores High.
	www.tiempocyberclimate.org /portal/datanao.htm (721 words)

	Temporal Variability of North Atlantic Oscillation and Tropical Atlantic SST
		The decadal variability in the North Atlantic (NA) has been observed from data analyses (Kushnir, 1994; Deser and Blackmon, 1993; Mehta and Delworth, 1995) and in the coupled model (Grotzner et al., 1997; Delworth et al., 1993; Mehta and Delworth, 1995).
		NAO index, the difference between the SLP anomalies at Azores and Iceland (Hurrell, 1995).
		North Atlantic Tropical (NAT) SST index, the average of SSTs in the region of 5°N-20°N, 40°W-20°W. South Atlantic Tropical (SAT) SST index, the average of SSTs in the region of 5°S-5°S, 15°W-5°E. Tropical Atlantic SST Index (TASI), the difference between NAT and SAT.
	www.aoml.noaa.gov /phod/acvp/raja.htm (1168 words)

	Met Office: Experimental winter NAO forecast
		When the NAO is 'negative', westerly winds are weaker or less persistent, northern Europe is colder and drier and southern Europe warmer and wetter than average.
		One of the simplest definitions of the NAO is that it is the winter difference in pressure at sea-level between the Azores and Iceland.
		The NAO prediction is considered together with forecasts from our dynamical prediction system to produce an outlook for the winter season (please refer to our headline summary).
	www.metoffice.com /research/seasonal/regional/nao (625 words)

	CRU Information Sheet no. 11: North Atlantic Oscillation
		The North Atlantic Oscillation (NAO) is a large-scale mode (i.e., pattern) of natural climate variability that has important impacts on the weather and climate of the North Atlantic region and surrounding continents, especially Europe.
		Although the NAO occurs in all seasons, it is during winter that it is particularly dominant, and therefore the focus of this information sheet is on the December to March period.
		The NAO is a north-south shift (or vice versa) in the track of storms and depressions across the North Atlantic Ocean and into Europe.
	www.cru.uea.ac.uk /cru/info/nao (622 words)

	North Atlantic Oscillation
		Changes in the NAO correlate with all variables around the ocean, from rainfall in Bordeaux to the amount of Saharan dust that ends up in the Bahamas and the richness of the fisheries off Iceland The NAO affects the circulation of seas at the North Atlantic's margins.
		They think the long-term memories that shape the NAO are held beneath the waves, in the cat's cradle of currents inside the North Atlantic.
		In the 1960s, when the NAO was low, the Peak practice: recently the North Atlantic Oscillation has been switching from high to low values on a timescale of decades.
	www.dhushara.com /book/diversit/extra/NaOf/nao.htm (2695 words)

	Climate Prediction Center - North Atlantic Oscillation (NAO)
		Strong positive phases of the NAO tend to be associated with above-averagel temperatures in the eastern United States and across northern Europe and below-average temperatures in Greenland and oftentimes across southern Europe and the Middle East.
		The NAO exhibits considerable interseasonal and interannual variability, and prolonged periods (several months) of both positive and negative phases of the pattern are common.
		An abrupt transition to recurring positive phases of the NAO then occurred during the 1979/80 winter, with the atmosphere remaining locked into this mode through the 1994/95 winter season.
	www.cpc.ncep.noaa.gov /data/teledoc/nao.shtml (431 words)

	Welcome - Klimet People
		During the NAO+ state, the Labrador Sea is covered by sea-ice (sustaining a strong deep convection, the Labrador Current extends far south and southward water and sea-ice transport along the Transpolar Drift Stream east of Greenland is decreasing.
		During the NAO- state, the Labrador Sea is open (with a decreased deep convection) and the sea-ice and water transport through the Fram Strait becomes stronger with an increasing NAO.
		In the NAO+ state, the temperature gradient between Greenland and the cool ocean surface to the south is minor.
	www.giub.unibe.ch /klimet/wanner/nao.html (656 words)

	[No title] (Site not responding. Last check: )
		Strong positive phases of the NAO tend to be associated with above-normal temperatures in the eastern United States and across northern Europe and below-normal temperatures in Greenland and oftentimes across southern Europe and the Middle East.
		The NAO index is obtained by projecting the NAO loading pattern to the daily anomaly 500 millibar height field over 0-90°N. The NAO loading pattern has been chosen as the first mode of a Rotated Empirical Orthogonal Function (EOF) analysis using monthly mean 500 millibar height anomaly data from 1950 to 2000 over 0-90°N latitude.
		The Southern Oscillation Index (SOI) is one measure of the large-scale fluctuations in air pressure occurring between the western and eastern tropical Pacific (i.e., the state of the Southern Oscillation) during El Niño and La Niña episodes.
	lwf.ncdc.noaa.gov /oa/climate/research/teleconnect/discussion.html (1679 words)

	Atlantic Thermohaline Circulation (D3) (Site not responding. Last check: )
		S, or a WOCE section to the north or south to determine the exchange of the equatorial zone with the southern subtropical Atlantic, in particular the variability of southern warm water export into the Northern Hemisphere and the net export of northern deep water.
		High resolution records of the variability of sea surface temperature and salinity in the North Atlantic and the thermohaline circulation during the last millennia have to be derived with a centennial resolution or better to be compared with other proxy records for determining past climate variability at decadal periods.
		Close links exist with focus D1 (NAO variability), because of the relations found in observations and models between North Atlantic surface atmospheric and oceanic properties (where the NAO is the dominant mode of variability) and the intensity of the thermohaline circulation (thermohaline circulation).
	www.clivar.org /publications/other_pubs/iplan/iip/pd3.htm (6808 words)

	Tim Osborn's climate data
		The North Atlantic Oscillation (NAO) is one of the major modes of variability of the Northern Hemisphere atmosphere.
		Jones PD, Jonsson T and Wheeler D (1997) Extension to the North Atlantic Oscillation using early instrumental pressure observations from Gibraltar and South-West Iceland.
		Osborn TJ (2004) Simulating the winter North Atlantic Oscillation: the roles of internal variability and greenhouse gas forcing.
	www.cru.uea.ac.uk /~timo/projpages/nao_update.htm (291 words)

	Climate Prediction Center - Teleconnections: North Atlantic Oscillation
		The daily NAO index correpsponds to the NAO patterns, which vary from one month to the next.
		The daily NAO index for the past 120 days.
		Each daily value has been standardized by the standard deviation of the monthly NAO index from 1950 to 2000 interpolated to the day in question.
	www.cpc.ncep.noaa.gov /products/precip/CWlink/pna/nao.shtml (139 words)

	Metcheck.com - Global Weather Forecasts - [Updated on 09 November 2007 at 20:00] - Weather Feeds - Live Data - Long ...
		It can also be viewed as the Atlantic half of the AO (Arctic Oscillation) teleconnection pattern - strongly influences temperatures over europe and much of North America - especially during the cold seasons - and determines the mean latitude of the prevailing storm tracks across the North Atlantic.
		The phase of the NAO is considered positive when pressures and heights are below normal over Greenland and Iceland (strong icelandic low) and above normal at middle and subtropical latitudes (strong Bermuda-Azores high) - and negative for the reverse anomalies.
		Wetter summers are associated with PNA phases with strong North to South pressure gradients.
	www.metcheck.com /V40/UK/FREE/teleconnections.asp (404 words)

	Some notes on the North Atlantic Oscillation Index (Site not responding. Last check: )
		The so called North Atlantic Oscillation Index, the difference in air pressure between Portugal and Iceland, is high.
		In The figure above the North Atlantic Oscillation Index anomalies for the winters of 1825 - 2004 are shown.
		The very warm winters were caused by a "high North Atlantic Oscillation Index" weather pattern.
	www.euronet.nl /users/e_wesker/nao.html (622 words)

	The Pacific Decadal Oscillation
		The pattern of North Pacific sea surface temperature (SST) variations noted to capture the oceanic part of the PDO is shown in Figure 1, while the pattern of sea level pressures (SLPs) noted to capture the atmospheric part are shown in Figure 2.
		The SST pattern highlights the strong tendency for temperatures in the central North Pacific to be anomalously cool when SSTs along the coast of North America are unusually warm, and vice-versa (Graham 1994, Miller et al 1995, Zhang et al 1997, Mantua et al 1997).
		The North American climate anomalies associated with PDO warm and cool extremes are broadly similar to those connected with El Niño and La Niña (Latif and Barnett 1995, Latif and Barnett 1996, Zhang et al.
	www.atmos.washington.edu /~mantua/REPORTS/PDO/PDO_cs.htm (2137 words)

	CAG: NAO (Site not responding. Last check: )
		The NAO can be characterised by various types of indices which all reveal that it has a broad band spectrum with no significant dominant periodicities (unlike ENSO!).
		Physically based climate models are capable of simulating many of the known features of the NAO and may be able to tell us how it might change in the future due to man-made emissions.
		The NAO has strong impacts on weather and climate in the North Atlantic region and surrounding continents and is a dominant exogenous factor in many biological systems.
	www.met.rdg.ac.uk /cag/NAO/index.html (201 words)

	Arctic Oscillation (AO) (Site not responding. Last check: )
		The AO is the dominant pattern of non-seasonal sea-level pressure (SLP) variations north of 20N, and it is characterized by SLP anomalies of one sign in the Arctic and anomalies of opposite sign centered about 37-45N.
		Arctic Oscillation (AO) and for the North Atlantic Oscillation (NAO), a close relative of the AO.
		Thompson, D. J., and J. Wallace, 1998: The Arctic Oscillation signature in the wintertime geopotential height and temperature fields.
	tao.atmos.washington.edu /ao (258 words)

	CGD Annual Scientific Report 2004
		Cassou, C., C. Deser, L. Terray, J. Hurrell, and M. Drevillon, 2004: Summer sea surface temperature conditions in the North Atlantic and their impact upon the atmospheric circulation in early winter.
		Magnusdottir, R. Saravanan, and A. Phillips, 2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3: Part II: Direct and indirect components of the response.
		Magnusdottir, G. Deser, and R. Saravanan, 2004: The effects of North Atlantic SST and sea ice anomalies on the winter circulation in CCM3.
	www.asr.ucar.edu /2004/CGD/pubs.html (3568 words)

	CPC - Monitoring & Data: MRF Ensemble North Atlantic Oscillation Outlooks
		The values at the upper left and right corners of each figure indicate the mean value of the NAO index and the correlation coefficients between the observations and the forecasts, respectively.
		The ensemble mean forecasts of the NAO index are obtained by averaging the 11 MRF ensemble members (blue lines), and the observed NAO index (fl line) is superimposed on each panel for comparison.
		For the forecasted indices (lower 3 panels), the yellow shading shows the ensemble mean plus and minus one standard deviation among the ensemble members, while the upper and lower red lines show the range of the forecasted indices, respectively.
	www.cpc.ncep.noaa.gov /products/precip/CWlink/pna/new.nao_index_ensm.html (221 words)

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