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Found 7 results

  1. High‐latitude influence of the quasi‐biennial oscillation Authors: James A. Anstey and Theodore G. Shepherd Published: 28th March, 2013 Abstract: The interannual variability of the stratospheric winter polar vortex is correlated with the phase of the quasi‐biennial oscillation (QBO) of tropical stratospheric winds. This dynamical coupling between high and low latitudes, often referred to as the Holton–Tan effect, has been the subject of numerous observational and modelling studies, yet important questions regarding its mechanism remain unanswered. In particular it remains unclear which vertical levels of the QBO exert the strongest influence on the winter polar vortex, and how QBO–vortex coupling interacts with the effects of other sources of atmospheric interannual variability such as the 11‐year solar cycle or the El Niño Southern Oscillation. As stratosphere‐resolving general circulation models begin to resolve the QBO and represent its teleconnections with other parts of the climate system, it seems timely to summarize what is currently known about the QBO's high‐latitude influence. In this review article, we offer a synthesis of the modelling and observational analyses of QBO–vortex coupling that have appeared in the literature, and update the observational record. Link to full paper:
  2. Solar forcing of winter climate variability in the Northern Hemisphere Authors: Sarah Ineson, Adam A. Scaife, Jeff R. Knight, James C. Manners, Nick J. Dunstone, Lesley J. Gray and Joanna D. Haigh First Published: 9th October, 2011 Abstract: An influence of solar irradiance variations on Earth’s surface climate has been repeatedly suggested, based on correlations between solar variability and meteorological variables. Specifically, weaker westerly winds have been observed in winters with a less active sun, for example at the minimum phase of the 11-year sunspot cycle. With some possible exceptions, it has proved difficult for climate models to consistently reproduce this signal. Spectral Irradiance Monitor satellite measurements indicate that variations in solar ultraviolet irradiance may be larger than previously thought. Here we drive an ocean–atmosphere climate model with ultraviolet irradiance variations based on these observations. We find that the model responds to the solar minimum with patterns in surface pressure and temperature that resemble the negative phase of the North Atlantic or Arctic Oscillation, of similar magnitude to observations. In our model, the anomalies descend through the depth of the extratropical winter atmosphere. If the updated measurements of solar ultraviolet irradiance are correct, low solar activity, as observed during recent years, drives cold winters in northern Europe and the United States, and mild winters over southern Europe and Canada, with little direct change in globally averaged temperature. Given the quasiregularity of the 11-year solar cycle, our findings may help improve decadal climate predictions for highly populated extratropical regions. Link to full paper: The "Nature GeoScience Link" access is still behind a paywall ( ) but it is now available via this ResearchGate link (and there is also a downloadable personal pdf version link there):
  3. Transfer of the solar signal from the stratosphere to the troposphere: Northern Winter Authors: Katja Matthes, Yuhji Kuroda, Kunihiko Kodera, Ulrike Langematz Published: March 2006 Abstract: The atmospheric response to the solar cycle has been previously investigated with the Freie Universität Berlin Climate Middle Atmosphere Model (FUB‐CMAM) using prescribed spectral solar UV and ozone changes as well as prescribed equatorial, QBO‐like winds. The solar signal is transferred from the upper to the lower stratosphere through a modulation of the polar night jet and the Brewer‐Dobson circulation. These model experiments are further investigated here to show the transfer of the solar signal from the lower stratosphere to the troposphere and down to the surface during Northern Hemisphere winter. Analysis focuses on the transition from significant stratospheric effects in October and November to significant tropospheric effects in December and January. The results highlight the importance of stratospheric circulation changes for the troposphere. Together with the poleward‐downward movement of zonal wind anomalies and enhanced equatorward planetary wave propagation, an AO‐like pattern develops in the troposphere in December and January during solar maximum. In the middle of November, one third of eddy‐forced tropospheric mean meridional circulation and surface pressure tendency changes can be attributed to the stratosphere, whereas most of the polar surface pressure tendency changes from the end of November through the middle of December are related to tropospheric mechanical forcing changes. The weakening of the Brewer‐Dobson circulation during solar maximum leads to dynamical heating in the tropical lower stratosphere, inducing circulation changes in the tropical troposphere and down to the surface that are strongest in January. The simulated tropospheric effects are identified as indirect effects from the stratosphere because the sea surface temperatures are identical in the solar maximum and minimum experiment. These results confirm those from other simplified model studies as well as results from observations. Link to full paper:
  4. Solar and QBO Influences on the Timing of Stratospheric Sudden Warmings Author: Lesley J. Gray Published: Dec 2004 Abstract: The interaction of the 11-yr solar cycle (SC) and the quasi-biennial oscillation (QBO) and their influence on the Northern Hemisphere (NH) polar vortex are studied using idealized model experiments and ECMWF Re-Analysis (ERA-40). In the model experiments, the sensitivity of the NH polar vortex to imposed easterlies at equatorial/subtropical latitudes over various height ranges is tested to explore the possible influence from zonal wind anomalies associated with the QBO and the 11-yr SC in those regions. The experiments show that the timing of the modeled stratospheric sudden warmings (SSWs) is sensitive to the imposed easterlies at the equator/subtropics. When easterlies are imposed in the equatorial or subtropical upper stratosphere, the onset of the SSWs is earlier. A mechanism is proposed in which zonal wind anomalies in the equatorial/subtropical upper stratosphere associated with the QBO and 11-yr SC either reinforce each other or cancel each other out. When they reinforce, as in Smin–QBO-east (Smin/E) and Smax–QBO-west (Smax/W), it is suggested that the resulting anomaly is large enough to influence the development of the Aleutian high and hence the time of onset of the SSWs. Although highly speculative, this mechanism may help to understand the puzzling observations that major warmings often occur in Smax/W years even though there is no strong waveguide provided by the QBO winds in the lower equatorial stratosphere. The ERA-40 data are used to investigate the QBO and solar signals and to determine whether the observations support the proposed mechanism. Composites of ERA-40 zonally averaged zonal winds based on the QBO (E/W), the SC (min/max), and both (Smin/E, Smin/W, Smax/E, Smax/W) are examined, with emphasis on the Northern Hemisphere winter vortex evolution. The major findings are that QBO/E years are more disturbed than QBO/W years, primarily during early winter. Sudden warmings in Smax years tend to occur later than in Smin years. Midwinter warmings are more likely during Smin/E and Smax/W years, although the latter result is only barely statistically significant at the 75% level. The data show some support for the proposed mechanism, but many more years are required before it can be fully tested. Link to full paper:
  5. Sunspots, the QBO and the stratosphere in the North Polar Region – 20 years later Authors: Labitzke, Karin; Kunze, Markus; Brönnimann, Stefan Published: June 2006 Abstract: We have shown in earlier studies the size of the changes in the lower stratosphere which can be attributed to the 11-year sunspot cycle (SSC). We showed further that in order to detect the solar signal it is necessary to group the data according to the phase of the Quasi-Biennial Oscillation (QBO). Although this is valid throughout the year it was always obvious that the effect of the SSC and the QBO on the stratosphere was largest during the northern winters (January/February). Here we extend our first study (LABITZKE, 1987) by using additional data. Instead of 30 years of data, we now have 65 years. Results for the entire data set fully confirm the early findings and suggest a significant effect of the SSC on the strength of the stratospheric polar vortex and the mean meridional circulation. Link to full paper: (Paywall version) Free-to-view copy:
  6. Sunspots and the Solar Max - What Exactly is a Sunspot? Author: Kuhn, Karl F. Simple Guide Produced By: Earth Observatory (NASA) First Published: 1994 Summary: There is no abstract as this is a simple educational guide. It outlines the history of observing sunspots and describes exactly what is a sunspot and the sun's powerful magnetic field. It briefly looks at the solar cycle and solar minimum and maximum phases. it explains that sunspots are not random and shows where they are located on the sun and how they have been observed using the "Butterfly Diagram" since 1874. It describes the "Solar Wind" and "Solar Flares" and explains how they can interrupt the earth's radio transmissions.. Overall, this is a short but excellent guide for those wishing to learn about these phenomena. Link to Full Guide:
  7. Do trend extraction approaches affect causality detection in climate change studies? Authors: Xu Huanga, Hossein Hassanib, Mansi Ghodsib, Zinnia Mukherjeec and Rangan Guptad Published: November 2016 (updated: November 2017) Abstract: Various scientific studies have investigated the causal link between solar activity (SS) and the earth’s temperature (GT). Results from literature indicate that both the detected structural breaks and existing trend have significant effects on the causality detection outcomes. In this paper, we make a contribution to this literature by evaluating and comparing seven trend extraction methods covering various aspects of trend extraction studies to date. In addition, we extend previous work by using Convergent Cross Mapping (CCM) - an advanced non-parametric causality detection technique to provide evidence on the effect of existing trend in global temperature on the causality detection outcome. This paper illustrates the use of a method to find the most reliable trend extraction approach for data preprocessing, as well as provides detailed analyses of the causality detection of each component by this approach to achieve a better understanding of the causal link between SS and GT. Furthermore, the corresponding CCM results indicate increasing significance of causal effect from SS to GT since 1880 to recent years, which provide solid evidences that may contribute on explaining the escalating global tendency of warming up recent decades. Link to full paper: file:///C:/Users/David/Downloads/PhysicaA_trendextractioncausality_acceptedmanuscript.pdf (please note that this link does not seem to work automatically and you may need to copy it into your browser)
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