Goede vraag

Bericht van: sebastiaan (bussum) , 16-08-2015 12:22 

De vraag is absoluut niet provocerend bedoelt, maar is het niet zo dat met een El Nino waarin we nu zitten, de kans op een (zeer) zachte winter zeer groot is?

De 2015/6 El Nino lijkt in de categorie 'super' terecht te komen. De laatste twee super El Nino's 82/3 en 97/98 gingen gepaard met matige winters bij ons. Maar..De steekproef is klein en bovendien is de impact op de atmosfeer afhankelijk van het centrum van opwarming. Daarom is het ook m.i. onverstandig dat het KNMI alle El Nino's op een hoop gooit. Zie daarvoor het onderzoek Central Pacific El Niño, the “subtropical bridge,” and Eurasian climate http://onlinelibrary.wiley.com/doi/10.1029/2011JD016493/abstract
Waarbij zij wijzen op het verschil van een east based El Nino en Central Based.

Over ander onderzoek kan je hieronder lezen.

Northern Hemisphere winter snow anomalies: ENSO, NAO and the winter of 2009/10 – Seager et al. (2010) “Winter 2009/10 had anomalously large snowfall in the central parts of the United States and in northwestern Europe. Connections between seasonal snow anomalies and the large scale atmospheric circulation are explored. An El Niño state is associated with positive snowfall anomalies in the southern and central United States and along the eastern seaboard and negative anomalies to the north. A negative NAO causes positive snow anomalies across eastern North America and in northern Europe. It is argued that increased snowfall in the southern U.S. is contributed to by a southward displaced storm track but further north, in the eastern U.S. and northern Europe, positive snow anomalies arise from the cold temperature anomalies of a negative NAO. These relations are used with observed values of NINO3 and the NAO to conclude that the negative NAO and El Niño event were responsible for the northern hemisphere snow anomalies of winter 2009/10.” Seager, R., Y. Kushnir, J. Nakamura, M. Ting, and N. Naik (2010), Geophys. Res. Lett., 37, L14703, doi:10.1029/2010GL043830.

Impact of the Stratosphere on the Winter Tropospheric Teleconnections between ENSO and the North Atlantic and European Region – Cagnazzo & Manzini (2009) “The possible role of stratospheric variability on the tropospheric teleconnection between El Niño–Southern Oscillation (ENSO) and the North Atlantic and European (NAE) region is addressed by comparing results from two ensembles of simulations performed with an atmosphere general circulation model fully resolving the stratosphere (with the top at 0.01 hPa) and its low-top version (with the top at 10 hPa). Both ensembles of simulations consist of nine members, covering the 1980–99 period and are forced with prescribed observed sea surface temperatures. It is found that both models capture the sensitivity of the averaged polar winter lower stratosphere to ENSO in the Northern Hemisphere, although with a reduced amplitude for the low-top model. In late winter and spring, the ENSO response at the surface is instead different in the two models. A large-scale coherent pattern in sea level pressure, with high pressures over the Arctic and low pressures over western and central Europe and the North Pacific, is found in the February–March mean of the high-top model. In the low-top model, the Arctic high pressure and the western and central Europe low pressure are very much reduced. The high-top minus low-top model difference in the ENSO temperature and precipitation anomalies is that North Europe is colder and the Northern Atlantic storm track is shifted southward in the high-top model. In addition, it has been found that major sudden stratospheric warming events are virtually lacking in the low-top model, while their frequency of occurrence is broadly realistic in the high-top model. Given that this is a major difference in the dynamical behavior of the stratosphere of the two models and that these events are favored by ENSO, it is concluded that the occurrence of sudden stratospheric warming events affects the reported differences in the tropospheric ENSO–NAE teleconnection. Given that the essence of the high-top minus low-top model difference is a more annular (or zonal) pattern of the anomaly in sea level pressure, relatively larger over the Arctic and the NAE regions, this interpretation is consistent with the observational evidence that sudden stratospheric warmings play a role in giving rise to persistent Arctic Oscillation anomalies at the surface.” Cagnazzo, Chiara, Elisa Manzini, 2009, J. Climate, 22, 1223–1238.

The role of the stratosphere in the European climate response to El Niño – Ineson & Scaife (2009) “El Niño/Southern Oscillation (ENSO) is the largest natural interannual climate signal in the tropics; oscillations between warm El Niño and cold La Niña phases occur every few years. The effects are felt not only in the centre of action, the tropical Pacific region, but around the globe. Observational studies show a clear response in European climate to ENSO in late winter. However, the underlying mechanisms of the link are not yet understood. Here we use a general circulation model of the atmosphere, that has been extended into the upper atmospheric layers, to provide end-to-end evidence for a global teleconnection pathway from the Pacific region to Europe via the stratosphere. We present evidence for an active stratospheric role in the transition to cold conditions in northern Europe and mild conditions in southern Europe in late winter during El Niño years. In our experiments, this mechanism is restricted to years when stratospheric sudden warmings occur. The response in European surface climate to the El Niño signal is large enough to be useful for seasonal forecasting.” S. Ineson & A. A. Scaife, Nature Geoscience 2, 32 – 36 (2009), doi:10.1038/ngeo381.

ENSO influence on Europe during the last centuries – Brönnimann et al. (2007) “El Niño/Southern Oscillation (ENSO) affects climate not only in the Pacific region and the tropics, but also in the North Atlantic-European area. Studies based on twentieth-century data have found that El Niño events tend to be accompanied in late winter by a negative North Atlantic Oscillation index, low temperatures in northeastern Europe and a change in precipitation patterns. However, many questions are open, for example, concerning the stationarity of this relation. Here we study the relation between ENSO and European climate during the past 500 years based on statistically reconstructed ENSO indices, early instrumental station series, and reconstructed fields of surface air temperature, sea-level pressure, precipitation, and 500 hPa geopotential height. After removing years following tropical volcanic eruptions (which systematically mask the ENSO signal), we find a consistent and statistically significant ENSO signal in late winter and spring. The responses to El Niño and La Niña are close to symmetric. In agreement with studies using twentieth-century data only, the ENSO signal in precipitation is different in fall than in late winter. Moving correlation analyses confirm a stationary relationship between ENSO and late winter climate in Europe during the past 300 years. However, the ENSO signal is modulated significantly by the North Pacific climate. A multi-field cluster analysis for strong ENSO events during the past 300 years yields a dominant pair of clusters that is symmetric and represents the ‘classical’ ENSO effects on Europe.” S. Brönnimann, E. Xoplaki, C. Casty, A. Pauling and J. Luterbacher, Climate Dynamics, Volume 28, Numbers 2-3, 181-197, DOI: 10.1007/s00382-006-0175-z.  Quote selectie