Sentences with phrase «winter nao»

Most recorded events appear to be linked with cooling episodes, mostly in winter, a transition to or from a negative winter NAO mode, a positive AMO mode.

I did find a statistically significant relationship between the winter NAO / AO and NH winter snow cover extent, which was great but still had the chicken and egg problem.

Chelliah and Bell (2004) defined a tropical multi-decadal pattern related to the AMO, the PDO and winter NAO with coherent variations in tropical convection and surface temperatures in the West African monsoon region, the central tropical Pacific, the Amazon Basin and the tropical Indian Ocean.

Not exact matches

«In winter, a positive North Atlantic Oscillation (NAO) is linked with a more northward, vigorous jet and mild, wet, stormy weather over the UK, while a negative NAO tends to be associated with a more southerly - positioned jet and relatively cold and dry but sometimes snowy conditions.

The researchers highlight that the exceptionally wet UK summers of 2007 and 2012 had notably negative readings of the NAO, as did the cold, snowy winters of 2009/2010 and 2010/2011, while the exceptionally mild, wet, stormy winters experienced in 2013/2014 and 2015/2016 showed pronounced positive spikes.

Apparently, winter precipitation was more important than summer temperature for annual glacier balance when only considering subsets of years with high NAO index and negative AMO index.

A negative NAO in winter usually goes hand - in - hand with cold weather in the eastern US and north - western Europe.»

Researchers from the University of California Irvine have shown that a phenomenon known as the Atlantic Multidecadal Oscillation (AMO)-- a natural pattern of variation in North Atlantic sea surface temperatures that switches between a positive and negative phase every 60 - 70 years — can affect an atmospheric circulation pattern, known as the North Atlantic Oscillation (NAO), that influences the temperature and precipitation over the Northern Hemisphere in winter.

When the AMO is in its positive phase and the sea surface temperatures are warmer, the study has shown that the main effect in winter is to promote the negative phase of the NAO which leads to «blocking» episodes over the North Atlantic sector, allowing cold weather systems to exist over the eastern US and Europe.

Moreover, the NAO was mostly positive with a relatively mild winter over Europe.»

Using the sophisticated UK Met Office climate model, Dr Screen conducted computer experiments to study the effects of Arctic sea - ice loss on the NAO and on Northern European winter temperatures.

Dr Screen, a Senior Lecturer in Mathematics at the University of Exeter said: «We know that the NAO is an important factor in controlling winter weather over Northern Europe».

«The negative phase of the NAO is typically associated with colder winters.

Because of this it has been reasonable to think that we would experience more severe winter weather if Arctic sea - ice loss intensifies the negative phase of the NAO».

A pioneering new study has explored how Arctic sea - ice loss influences the North Atlantic Oscillation (NAO) weather phenomenon, which affects winter weather conditions in Northern Europe, in places such as the UK, Scandinavia and the Baltic states.

Using historical records of precipitation, a relationship between winter precipitation and NAO phases was established.

The location of this cave in the foreland of the East Carpathian Mountains means winter precipitation is modulated by the North Atlantic Oscillation (NAO), with wetter conditions influencing the availability of nitrogen within the surrounding forest system.

The westerlies in the Northern Hemisphere, which increased from the 1960s to the 1990s but which have since returned to about normal as part of NAO and NAM changes, alter the flow from oceans to continents and are a major cause of the observed changes in winter storm tracks and related patterns of precipitation and temperature anomalies, especially over Europe.

Furthermore, since the end of the 19th century, we find an increasing variance in multidecadal hydroclimatic winter and spring, and this coincides with an increase in the multidecadal North Atlantic Oscillation (NAO) variability, suggesting a significant influence of large - scale atmospheric circulation patterns.

NAO - has a related impacts on winter climate extend from Florida to Greenland and from northwestern Africa over Europe far into northern Asian region.

A recent study of instrumental time series revealed NAO [North Atlantic Oscillation] as main factor for a strong relation between winter temperature, precipitation and river discharge in central Norway over the past 50 years.

A warm AMO phase leads to an atmospheric warming limited to the lower troposphere in summer, while it leads to a negative phase of the NAO in winter.

Judah has been publishing on the link between Eurasian snow cover in autumn and the NAM / NAO in the following winter for quite some time.

North Atlantic Oscillation (NAO), a measure of the strength of the Icelandic Low and the Azores High, and of the westerly winds between them, mainly in winter.

Does the current winter season detract from your conclusions, given the opposite nature of the AO and NAO in comparison to 09/10 and 10/11 (or any winter in the last 60 years)?

The PNA (left) and NAO (right) teleconnection patterns, shown as one - point correlation maps of 500 hPa geopotential heights for boreal winter (DJF) over 1958 to 2005.

Similar conclusions are reached in a numerical weather prediction context by T. Jung et al. at ECMWF (GRL 2011: http://www.agu.org/pubs/crossref/2011/2011GL046786.shtml) who performed very detailed sensitivity analysis of the origin of the very persistent negative NAO (blocked phase) during the winter of 2009 - 10.

The analysis of the Diekirch data shows that the winter temperatures correlate very well with the NAO index of the December to March months.

The NAO is the dominant mode of winter climate variability in the North Atlantic region ranging from central North America to Europe and much into Northern Asia.

The positive phase of the NAO that we have been in is supposed to yield warm and wet winters in Europe and in cold and dry winters in northern Canada and Greenland.

For instance, during the «snowmageddon» winter of 2009/2010, the NAO was at a near record low value... «Given our modelling result, these cold winters were probably exacerbated by the recent prolonged and anomalously low solar minimum.

The NAO change produces affects on the winter circulation patterns resulting in a dearth or abundance of Northern Hemisphere severe winter storms.

According to their modeling studies, the difference in the amount of incoming solar radiation, in this case, primarily in the ultraviolet (UV) wavelengths, during the minima and maxima of the 11 - yr solar cycle are large enough to produce a characteristic change in the winter circulation pattern of the atmosphere over North America... When the NAO is in its negative phase, more cold air can seep south from the Arctic and impact the lower latitudes of Europe and the eastern U.S., which helps spin up winter storm systems.

It is found that winter sea ice is about 50 cm thinner in high - NAO index years than in low - NAO index years in the Eurasian coastal region mainly due to stronger wind - driven ice export.

The impact of the NAO on winter sea levels provides an additional uncertainty of 0.1 to 0.2 m to these estimates (Hulme et al., 2002; Tsimplis et al., 2004a).

Climate variability associated with the North Atlantic Oscillation (NAO) determines many physical coastal processes in Europe (Hurrell et al., 2003, 2004), including variations in the seasonality of coastal climates, winter wind speeds and patterns of storminess and coastal flooding in north - west Europe (Lozano et al., 2004; Stone and Orford, 2004; Yan et al., 2004).

Thus, winter and spring atmospheric anomalies associated with the positive phase of the NAO may underlie the reduction of summer sea ice extent observed during the 1980s and 1990s.

[1] Influence of winter pre-conditioning of Arctic sea ice due to atmospheric forcing associated with the North Atlantic Oscillation (NAO) on the reduction in summer sea ice extent is studied.

Although the NAO is the dominant pattern of atmospheric circulation variability, accounting for about half of the total winter SLP variance on both interannual and multi-decadal time scales, other large - scale structures of internal circulation variability will also undoubtedly contribute to uncertainty in future climate trends.

This study highlights the expected range of projected winter air temperature and precipitation trends over the next 30 — 50 years due to unpredictable fluctuations of the North Atlantic Oscillation (NAO) superimposed upon forced anthropogenic climate change.

The purpose of this study is to examine the impact of the NAO on projected changes in winter (December - March average) terrestrial surface air temperature (SAT) and precipitation (P) over the next 30 — 50 years.

This study has highlighted the role of internal variability of the NAO, the leading mode of atmospheric circulation variability over the Atlantic / European sector, on winter (December - March) surface air temperature (SAT) and precipitation (P) trends over the next 30 years (and the next 50 years: see Supplemental Materials) using a new 40 - member ensemble of climate change simulations with CESM1.

Open water in the Arctic Ocean during the winter allows heat to flow from the ocean to the atmosphere, creating the high pressure needed for a negative NAO to materialize.

An emerging debate among scientists questions which force will win out over winters in Europe and North America: the cooling influence of more negative NAO conditions, or the warming influence of climate change itself?

When depression activity over the Arctic is high, the indices of both AO and NAO are more easily inclined towards a positive state, with a stronger west circulation around the northern hemisphere and improved temperature isolation for the Arctic region — and that's the real paradox of this story, because positive AO and NAO are actually associated with milder winters in Europe and for instance the US.

Posted in Science Lessons, tagged arctic, asia, climate change, cold, environment, europe, global warming, greenhouse effect, media, NAO, science, sea ice, snow, united states, winter on January 11, 2011 5 Comments»

In future one can probably expect stretches of open ocean even at the start of the Arctic winter, so increasingly unstable atmosphere — and therefore positive AO (and NAO) even during the northern hemisphere cold months.

For example, La Niña winters tend towards a stronger polar vortex and the positive phase of the NAO, but if the polar vortex breaks down (which it's done many times during La Niña winters; Butler & Polvani 2011) it will push the climate towards a negative NAO pattern, and the two effects tend to cancel over the season.

Similarly Yeakel 2016 reported Bermuda reefs experienced a drop in pH in association with a negative NAO that caused westerly winds to move further south and generate a deeper winter mixed layer just to the north of the Bermuda reefs.

Months really surprise people: DJF = Dec., Jan., Feb. = winter JJA = Jun., July, Aug. = summer MAM = spring SON = fall SRES = Special Report on Emissions Scenarios UNFCCC = United Nations Framework Convention on Climate Change ITCZ = Intertropical Convergence Zone NAO = North Atlantic Oscillation ENSO = El Nino Southern Oscillation PPM / PPMV = Parts per million by volume