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sebastiaan1973

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  1. http://www.nature.com/articles/s41558-019-0551-4.epdf?author_access_token=lev7cCLvJaqZgqEL2fkrCtRgN0jAjWel9jnR3ZoTv0OkPw7OWz-ctumf1Sllaa-sNqBW8kixcwl-ojSoyKUmUfvHbXmZ3llXRmZN-HO_pmKRWEHLwCuZqZkuv4bolog-ehQV4R4jg8i93P7ntZX4_w%3D%3D Observations show that reduced regional sea-ice cover is coincident with cold mid-latitude winters on interannual timescales. However, it remains unclear whether these observed links are causal, and model experiments suggest that they might not be. Here we apply two independent approaches to infer causality from observations and climate models and to reconcile these sources of data. Models capture the observed correlations between reduced sea ice and cold mid-latitude winters, but only when reduced sea ice coincides with anomalous heat transfer from the atmosphere to the ocean, implying that the atmosphere is driving the loss. Causal inference from the physics-based approach is corroborated by a lead–lag analysis, showing that circulation-driven temperature anomalies precede, but do not follow, reduced sea ice. Furthermore, no mid-latitude cooling is found in modelling experiments with imposed future sea-ice loss. Our results show robust support for anomalous atmospheric circulation simultaneously driving cold mid-latitude winters and mild Arctic conditions, and reduced sea ice having a minimal influence on severe mid-latitude winters.
  2. https://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/ens-mean Intrestring update from Glosea5. Neutral ENSO. And high Area in northern Europe.
  3. The key findings are as follows. 1. ENSO produces a hemispheric negative NAM pattern, which is considerably stronger in the Atlantic sector in late winter. The ENSO response in the Atlantic is mediated by planetary wave forcing of the stratosphere/upper troposphere (Huang et al., 1998; Ineson and Scaife, 2009). Our results suggest that there is a lag in the response in the Atlantic sector relative to the direct tropospheric forcing in the North Pacific, which is quite similar in the different QBO phases and in both early/mid- and late winter. QBO modulates the ENSO signal so that it becomes significant in the Atlantic sector already in early/mid-winter. The ENSO effect in the easterly QBO phase resembles a negative NAO pattern. The weaker polar vortex during the easterly QBO (Holton and Tan, 1980; Maliniemi et al., 2016) advances the mediation of a negative NAO signal to the Atlantic sector (Ineson and Scaife, 2009) and is observed earlier than without QBO modulation. In late winter when the Holton-Tan mechanism is no longer significant (Lu et al., 2014; Maliniemi et al., 2016) a negative NAO signal is rather similar in the two QBO phases. This QBO modulation of ENSO teleconnection to the Atlantic sector verifies the modeling study by Calvo et al. (2009), both in early/mid- and late winter. 2. The typical positive NAO pattern related to volcanic activity becomes more clear in the westerly QBO phase, especially in late winter. We suggest that this is due to the weaker Brewer-Dobson circulation in the westerly QBO (Flury et al., 2013), which mixes volcanic aerosols less effectively, leaving them mainly to the lower equatorial stratosphere. This would lead to a stronger infrared absorption by these aerosols in the lower equatorial stratosphere, to larger equator-to-pole temperature gradients and a stronger polar vortex (Robock, 2000; Otterå et al., 2010). 3. The geomagnetic activity (energetic particle precipitation) signature in both early/mid- and late winter is modulated by the QBO phase. Geomagnetic activity produces a significant circulation pattern mainly during the easterly QBO. It represents a dipole pressure pattern similar to the positive NAO pattern, although in late winter it is shifted towards the pole. The geomagnetic activity signal is now verified by a simultaneous consideration of sunspot effects, thus generalizing the earlier studies (Maliniemi et al., 2013, 2016; Roy et al., 2016). A possible explanation to the QBO dependence of the signal to geomagnetic activity is that the Brewer-Dobson circulation is stronger in easterly QBO (Flury et al., 2013). This enhances the transport of ozone to high latitudes (Li and Tung, 2014) and the downwelling of NOx (produced by particle precipitation (Funke et al., 2014)) inside the polar vortex (Baldwin et al., 2001). This would lead to a larger ozone loss for a given level of geomagnetic activity in the QBO easterly phase compared to the westerly QBO, and as so to stronger polar vortex due to the stratospheric cooling (Baumgaertner et al., 2011). 4. The pattern of the signal due to sunspots (or any other solar driver like TSI or EUV/UV co-varying with sunspots) is very different between early/mid- and late winter. The positive NAO pattern due to SSN in late winter, which is mainly obtained in the easterly QBO phase (in agreement with, e.g., Labitzke and van Loon, 1988; Lu et al., 2009), suggests for the top-down mechanism originating in the stratosphere by enhanced solar UV heating (Kodera and Kuroda, 2002). On the other hand, the positive SLP signature in Aleutian in early winter is only marginally modulated by the QBO, which suggests that the stratospheric variability does not have an effect on it. Rather, it supports the bottom-up mechanism, which is directly forced from the troposphere by enhanced heating in the tropical Pacific (e.g., Meehl et al., 2008). These results related to sunspot activity during early/mid- and late winter in different regions and in different QBO phases verify the different earlier findings (Gray et al., 2010, and multiple references therein) under a common global setting. https://www.sciencedirect.com/science/article/pii/S1364682618301421
  4. https://www.tandfonline.com/doi/full/10.1080/16742834.2019.1588064 This study investigates the combined effect of the El Niño–Southern Oscillation (ENSO) and stratospheric quasi-biennial oscillation (QBO) on the Madden Julian Oscillation (MJO). The results show that the western Pacific MJO originating from the Indian Ocean during La Niña/QBO easterly years is stronger than that during El Niño years. This relation, however, disappears during La Niña/QBO westerly years. The reason is that ENSO and the QBO have different effects on each MJO event. For an El Niño year, there is only about one MJO event, and the QBO effect is small. During a La Niña/QBO easterly year, there are 1.7 MJO events, while during a La Niña/QBO westerly year, there are only 0.6 MJO events. El Niño can reinforce the MJO over the western Pacific because of the positive moisture advection of the El Niño mean state by MJO easterly wind anomalies. The QBO mainly affects the MJO over the Maritime Continent region by changing the high-cloud-controlled diurnal cycle; and the Maritime Continent barrier effect is enhanced during the QBO westerly phase because of the strong diurnal cycle. During El Niño years, even the MJO over the Maritime Continent is suppressed by the QBO westerly phase; the MJO can be reinforced over the western Pacific. During La Niña/QBO westerly years, the MJO over the Maritime Continent is suppressed because of the strong Maritime Continent diurnal cycle, and it is further suppressed over the western Pacific because of the lack of a reinforcement process.
  5. https://www.esrl.noaa.gov/psd/data/correlation/qbo.data Juli came in with 10,96. We are in the process of a declining wQBO.
  6. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JD029368 Abstract The Quasi‐Biennial Oscillation (QBO) is the dominant mode of interannual variability in the tropical stratosphere, with easterly and westerly zonal wind regimes alternating over a period of about 28 months. It appears to influence the Northern Hemisphere winter stratospheric polar vortex and atmospheric circulation near the Earth's surface. However, the short observational record makes unequivocal identification of these surface connections challenging. To overcome this, we use a multicentury control simulation of a climate model with a realistic, spontaneously generated QBO to examine teleconnections with extratropical winter surface pressure patterns. Using a 30‐hPa index of the QBO, we demonstrate that the observed teleconnection with the Arctic Oscillation (AO) is likely to be real, and a teleconnection with the North Atlantic Oscillation (NAO) is probable, but not certain. Simulated QBO‐AO teleconnections are robust, but appear weaker than in observations. Despite this, inconsistency with the observational record cannot be formally demonstrated. To assess the robustness of our results, we use an alternative measure of the QBO, which selects QBO phases with westerly or easterly winds extending over a wider range of altitudes than phases selected by the single‐level index. We find increased strength and significance for both the AO and NAO responses, and better reproduction of the observed surface teleconnection patterns. Further, this QBO metric reveals that the simulated AO response is indeed likely to be weaker than observed. We conclude that the QBO can potentially provide another source of skill for Northern Hemisphere winter prediction, if its surface teleconnections can be accurately simulated.
  7. I wonder if we get some impact of the MJO moving through 6-7.
  8. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf According to NOAA there is no influence of MJO in the coming weeks. "MJO activity appears unlikely to influence the extratropical circulation in the coming weeks. For North America, the negative phase of the AO is likely tied to the response of the signal crossing the Pacific over the last two weeks, and appears “locked in” for the near future. This is likely to negate any building ridging across the Great Lakes that would typically be the lagged response to the MJO crossing the Maritime Continent. "
  9. I really doubt if the EC-oper has the right scenario. This morning it's solution had support of 8% of the members.
  10. I was surprised to see your comment Because the control is quite cold 11-15 days ahead.
  11. Just over the North Sea, this run is quite good, with low Tmax.
  12. Being Dutch I heard it was a temporarily high in combination with snow on the 19th of januar. Sneeuwkans= chance of snow. Blue line is the control.
  13. http://www.meteociel.fr/modeles/archives/archives.php?type=era But just 10 hPa temperature charts.
  14. A split on day 10 and a reversal of winds which seems to go on for some time. At 216h we see downwelling.
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