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  1. THE ARCTIC THREAD This is a brand new thread for everything to do with the Arctic as well as Antarctica. I hope that many forum members will contribute on here. I have been a keen weather enthusiast for well over 50 years and have developed widespread interests in many meteorological topics. I have always been particularly fascinated by the Arctic and how it interacts with global climate patterns. We have seen a worrying decline in Arctic sea ice extent during the last 30 years and the Arctic has become the centre of the global warming and climate change debate. Whilst this is undoubtedly highly influenced by human activities, there are also some longer term natural changes in play too. I always like to examine the facts and not be overly influenced by exaggerated reports at either end of the debate which has become highly political. This thread will cover a wide range of topics including: Arctic sea ice extent - current and historic levels, rates of change, ice melt and refreezing, ice loss, ice age (new and older ice), comparisons and analysis with regular updates. Antarctica sea ice extent - as above plus features on the ice shelves and the differences between the two polar regions, facts and figures. Arctic and Antarticaa Sea surface temperatures - current, historic, trends, anomalies, reasons for changes. Arctic and Antarctica air temperatures, monitoring at certain sites, records, changes, data sets. Northern Hemisphere snow cover - seasonal changes, yearly and longer term variations, influences on regional climate and weather patterns. The Greenland ice cap - long term and current research, measurements, trends, rates of change. Glaciers - facts and figures, which ones are declining, which ones are growing, rates of change, global net ice loss. The Polar Vortex - how does this influence the Arctic climate? How does Arctic warming and ice loss influence the polar vortex? North America climate focus - how and when changes in the Arctic impact on the higher and middle latitudes (I often produce European and UK focused reports on a UK weather forum). Historic climates, research into Ice Ages and inter-glacial warmer periods. Climate change and its influence on the Arctic and Antarctica, how much, how fast, why? Global Warming Debate - assessing the extent of human impacts, separating the facts from the fiction, taking a "balanced" approach. Sudden Stratospheric Warming - impacts on the Arctic, what happens, how fast, why? The Arctic oscillation and the Antarctic oscillation - current, forecast, anomalies and historic values, links to weather patterns. Arctic and Antarctica news and events - special features and reports with comments and analysis (eg: the recent clouds of smoke covering the Arctic from vast Siberian forest fires) I will add to this list as this thread evolves. In general I would like this thread to appeal to as wide an audience as possible. I'm a great believer in keeping things simple and explaining topics in plain English. I regularly post on the "Teleconnections" thread and some of the more complex subjects such as how does the Arctic ice loss teleconnecton interact with other teleconnections may be more suitable for that thread (or perhaps both threads). There are already some excellent papers and video presentations relating to the Arctic in the "Teleconnections Research Portal" and we will be adding a lot more as winter approaches. Some of these papers may be reviewed on this thread especially when they relate to a particular post. List of Useful Links to Arctic and Antarctica Sites, Data, Facts, Charts etc: This list will gradually evolve in line with the thread (so work in progress). If you have a link that you feel is relevant, please draw this to my attentions by "replying to topic" or with a "personal message". Here's a direct link to the Teleconnections Research Portal - we have placed many Arctic related papers and presentations in there with many more being added during the coming months. National Snow and Ice Data Center (NSIDC): - daily ice cover updates and monthly reports. Arctic Sea Ice graphs: - this huge site with many sub links provides any extraordinary amount current and historic ice data, charts and maps. NOAA National Weather Centre Environmental Modelling Centre Global Sea Surface Temperatures and Anomaly Maps: (click on the map for any region). NOAA Snow Cover Maps: - current, historic and animated snow cover maps for Northern Hemisphere, North America and Eurasia. NCEP 2m Surface Temperature Anomalies by region: - includes forecast, current and past charts with extensive Arctic and Antarctica coverage. NASA WorldView Satellite Imagery: - with many options and tools to create your own world or regional images. Polar Science Center: - packed with Arctic news, research, data and links to conferences and papers (some of these are already in the Research Portal and more to add). Zachary (Zach) Labe: - a Ph.D. student, Dept of Earth System Science, University of California; fascinating Arctic research, reports, data, charts and links to papers. Climate Reanalyzer: - for current weather data and analysis (northern hemisphere). many more to follow during the next few weeks Arctic Ocean Regional Map Showing All the Seas: I show an Arctic map (below) to identify the locations of all the seas that make up the Arctic Ocean so that we can comment more meaningfully on the local variations in our posts on this thread. Antarctica Map: I will kick things off with a series of short posts to give a flavour of what might follow. I'll do one on the current Arctic sea ice extent later today and two more tomorrow on Arctic sea surface temperatures and Northern Hemisphere snow cover. If I have time, I will do another one on Arctic air temperatures and also show that report on the Arctic ash cloud spreading from those Siberian forest fires. When I return from a business trip, I'll add several more posts later next week. I would really like to see other forum members getting involved on here with posts and comments and I hope that we can get some debates going too. David
  2. Snow-atmosphere coupling and its impact on temperature variability and extremes over North America Authors: G. T. Diro, L. Sushama, O. Huziy Published: July 2017 Abstract: The impact of snow-atmosphere coupling on climate variability and extremes over North America is investigated using modeling experiments with the fifth generation Canadian Regional Climate Model (CRCM5). To this end, two CRCM5 simulations driven by ERA-Interim reanalysis for the 1981–2010 period are performed, where snow cover and depth are prescribed (uncoupled) in one simulation while they evolve interactively (coupled) during model integration in the second one. Results indicate systematic influence of snow cover and snow depth variability on the inter-annual variability of soil and air temperatures during winter and spring seasons. Inter-annual variability of air temperature is larger in the coupled simulation, with snow cover and depth variability accounting for 40–60% of winter temperature variability over the Mid-west, Northern Great Plains and over the Canadian Prairies. The contribution of snow variability reaches even more than 70% during spring and the regions of high snow-temperature coupling extend north of the boreal forests. The dominant process contributing to the snow-atmosphere coupling is the albedo effect in winter, while the hydrological effect controls the coupling in spring. Snow cover/depth variability at different locations is also found to affect extremes. For instance, variability of cold-spell characteristics is sensitive to snow cover/depth variation over the Mid-west and Northern Great Plains, whereas, warm-spell variability is sensitive to snow variation primarily in regions with climatologically extensive snow cover such as northeast Canada and the Rockies. Furthermore, snow-atmosphere interactions appear to have contributed to enhancing the number of cold spell days during the 2002 spring, which is the coldest recorded during the study period, by over 50%, over western North America. Additional results also provide useful information on the importance of the interactions of snow with large-scale mode of variability in modulating temperature extreme characteristics. Link to full paper:
  3. Snow–Atmosphere Coupling Strength. Part I: Effect of Model Biases Authors: Li Xu, Paul Dirmeyer Published: April 2013 Abstract: Snow–atmosphere coupling strength, the degree to which the atmosphere (temperature and precipitation) responds to underlying snow anomalies, is investigated using the Community Climate System Model (CCSM) with realistic snow information obtained from satellite and data assimilation. The coupling strength is quantified using seasonal simulations initialized in late boreal winter with realistic initial snow states or forced with realistic large-scale snow anomalies, including both snow cover fraction observed by remote sensing and snow water equivalent from land data assimilation. Errors due to deficiencies in the land model snow scheme and precipitation biases in the atmospheric model are mitigated by prescribing realistic snow states. The spatial and temporal distributions of strong snow–atmosphere coupling in this model are revealed to track the continental snow cover edge poleward during the ablation period in spring, with secondary maxima after snowmelt. Compared with prescribed “perfect” snow simulations, the free-running CCSM captures major regions of strong snow–atmosphere coupling strength, with only minor departures in magnitude, but showing uneven biases over the Northern Hemisphere. Signals of strong coupling to air temperature are found to propagate vertically into the troposphere, at least up to 500 hPa over the coupling “cold spots.” The main mechanism for this vertical propagation is found to be longwave radiation and condensation heating. Link to full paper:
  4. Snow–atmosphere coupling in the Northern Hemisphere Authors: Gina R. Henderson, Yannick Peings, Jason C. Furtado & Paul J. Kushner Published: Oct 2018 Abstract: Local and remote impacts of seasonal snow cover on atmospheric circulation have been explored extensively, with observational and modelling efforts focusing on how Eurasian autumn snow-cover variability potentially drives Northern Hemisphere atmospheric circulation via the generation of deep, planetary-scale atmospheric waves. Despite climate modelling advances, models remain challenged to reproduce the proposed sequence of processes by which snow cover can influence the atmosphere, calling into question the robustness of this coupling. Here, we summarize the current level of understanding of snow–atmosphere coupling, and the implications of this interaction under future climate change. Projected patterns of snow-cover variability and altered stratospheric conditions suggest a need for new model experiments to isolate the effect of projected changes in snow on the atmosphere. Link to paper: (This paper is currently behind a paywall. Please use 'reply' below if you know of a free-to-view copy). Alternatively a full copy is available for temporary download from here: 10.1038@s41558-018-0295-6.pdf
  5. Snow–(N)AO Teleconnection and Its Modulation by the Quasi-Biennial Oscillation Authors: Y. Peings Published: 29th November, 2017 Abstract: This study explores the wintertime extratropical atmospheric response to Siberian snow anomalies in fall, using observations and two distinct atmospheric general circulation models. The role of the quasi-biennial oscillation (QBO) in modulating this response is discussed by differentiating easterly and westerly QBO years. The remote influence of Siberian snow anomalies is found to be weak in the models, especially in the stratosphere where the “Holton–Tan” effect of the QBO dominates the simulated snow influence on the polar vortex. At the surface, discrepancies between composite analyses from observations and model results question the causal relationship between snow and the atmospheric circulation, suggesting that the atmosphere might have driven snow anomalies rather than the other way around. When both forcings are combined, the simulations suggest destructive interference between the response to positive snow anomalies and easterly QBO (and vice versa), at odds with the hypothesis that the snow–North Atlantic Oscillation/Arctic Oscillation [(N)AO] teleconnection in recent decades has been promoted by the QBO. Although model limitations in capturing the relationship exist, altogether these results suggest that the snow–(N)AO teleconnection may be a stochastic artifact rather than a genuine atmospheric response to snow-cover variability. This study adds to a growing body of evidence suggesting that climate models do not capture a robust and stationary snow–(N)AO relationship. It also highlights the need for extending observations and/or improving models to progress on this matter. Link to full paper:
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