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jethro

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Posted
  • Location: Camborne
  • Location: Camborne

Solar cyclic variability can modulate winter Arctic climate

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This study investigates the role of the eleven-year solar cycle on the Arctic climate during 1979–2016.
It reveals that during those years, when the winter solar sunspot number (SSN) falls below 1.35
standard deviations (or mean value), the Arctic warming extends from the lower troposphere to high
up in the upper stratosphere and vice versa when SSN is above. The warming in the atmospheric
column reflects an easterly zonal wind anomaly consistent with warm air and positive geopotential
height anomalies for years with minimum SSN and vice versa for the maximum. Despite the inherent
limitations of statistical techniques, three different methods – Compositing, Multiple Linear Regression
and Correlation – all point to a similar modulating influence of the sun on winter Arctic climate via the
pathway of Arctic Oscillation. Presenting schematics, it discusses the mechanisms of how solar cycle
variability influences the Arctic climate involving the stratospheric route. Compositing also detects
an opposite solar signature on Eurasian snow-cover, which is a cooling during Minimum years, while
warming in maximum. It is hypothesized that the reduction of ice in the Arctic and a growth in Eurasia,
in recent winters, may in part, be a result of the current weaker solar cycle

https://www.nature.com/articles/s41598-018-22854-0.pdf (open)

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Posted
  • Location: Camborne
  • Location: Camborne

Consistency and discrepancy in the atmospheric response to Arctic sea-ice loss across climate models

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The decline of Arctic sea ice is an integral part of anthropogenic climate change. Sea-ice loss is already having a significant impact on Arctic communities and ecosystems. Its role as a cause of climate changes outside of the Arctic has also attracted much scientific interest. Evidence is mounting that Arctic sea-ice loss can affect weather and climate throughout the Northern Hemisphere. The remote impacts of Arctic sea-ice loss can only be properly represented using models that simulate interactions among the ocean, sea ice, land and atmosphere. A synthesis of six such experiments with different models shows consistent hemispheric-wide atmospheric warming, strongest in the mid-to-high-latitude lower troposphere; an intensification of the wintertime Aleutian Low and, in most cases, the Siberian High; a weakening of the Icelandic Low; and a reduction in strength and southward shift of the mid-latitude westerly winds in winter. The atmospheric circulation response seems to be sensitive to the magnitude and geographic pattern of sea-ice loss and, in some cases, to the background climate state. However, it is unclear whether current-generation climate models respond too weakly to sea-ice change. We advocate for coordinated experiments that use different models and observational constraints to quantify the climate response

https://www.nature.com/articles/s41561-018-0059-y

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Posted
  • Location: Camborne
  • Location: Camborne

Diversity of El Niño Variability Makes Prediction Challenging

The atmospheric response to El Niño, both in the Pacific region and around the world, changes with each event and is uncertain in future under the influence greenhouse gas forcing.

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The El Niño-Southern Oscillation (ENSO) is a regular climatic fluctuation but each El Niño event observed over recent decades has had different characteristics. Since ENSO has enormous impacts on natural and human systems – including agriculture, forestry, public health, the hydrological cycle, the global carbon cycle, marine and terrestrial ecosystems, and fisheries – being able to predict future ENSO events is critical. In an article recently published in Reviews of Geophysics, Yeh et al. [2018] considered the atmospheric impacts of recent El Niños and how these might change in future with a warming climate. The editor asked one of the authors to explain why and how El Niño events vary, and the challenges of predicting future events.

https://eos.org/editors-vox/diversity-of-el-nino-variability-makes-prediction-challenging

Edited by knocker
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Posted
  • Location: Camborne
  • Location: Camborne

Aspirated and non‐aspirated automatic weather station Stevenson screen intercomparison

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In this study six wooden Stevenson screen configurations (five aspirated, one non‐aspirated) were evaluated at the Centre for Atmospheric Research Experiments in Egbert, Ontario, Canada. The field experiment was performed over a 1‐year period to evaluate aspirated and non‐aspirated Stevenson screen configurations used at the Meteorological Service of Canada’s Automated Weather Stations. The results show the non‐aspirated screen is warmer than the aspirated screen duct location by 0.11 °C on average with a significant increase in the maximum daily temperature of 0.22 °C due to radiant heating effects. Temperature differences up to 2.1 °C were observed between the aspirated and non‐aspirated screens with a mean increase of 0.46 °C following 30‐min periods of mean global radiation greater than 200 W/m2 and mean wind speed less than 2 m/s. Temperature differences between the two screens are more variable with standard deviations up to 0.3 °C for wind speeds below 2 m/s. The maximum daily temperature for the historic minimum and maximum thermometer locations and upper regions of the aspirated screen is also found to be significantly warmer during radiant heating conditions. The three locations within the aspiration duct provided very similar results with mean differences of −0.02 and −0.01 °C below the probe uncertainty. The aspirated Stevenson screen with motor off produced low overall bias with lower maximum daily temperatures and higher minimum daily temperatures compared to the aspirated screen. Comparison between the historic wooden frame and new aluminium mounting is not significant with the wooden frame cooler by 0.02 °C overall. Differences between the new aluminium and new plastic ducts showed similar results of 0.02 and 0.01 °C overall. The aspirated Stevenson screen configuration is recommended at new Automatic Weather Station installations where AC power is available.

https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.5453?campaign=wolearlyview

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Posted
  • Location: Camborne
  • Location: Camborne

To improve seasonal storm track forecasts, look to the tropical stratosphere

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People have become familiar with “bomb cyclones” this winter, as several powerful winter storms brought strong winds and heavy precipitation to the U.S. east coast, knocking out power and causing flooding. With strength that can rival that of hurricanes, bomb cyclones get their name from a process called bombogenesis, which describes the rapid intensification they undergo within 24 hours as they move along the coast.

These winter storms tend to form and travel within narrow “atmospheric conveyor belts”, called storm tracks, which can change location over a period of years.

Scientists have extensively studied potential causes behind these year-to-year changes in attempt to better forecast storm tracks and their extreme impacts, but new research from scientists at the Stony Brook University (SBU) School of Marine and Atmospheric Sciences, funded by NOAA Research’s MAPP Program, identifies another crucial controlling force.

After analyzing 38 years of model data, the research team found that an alternating pattern of winds high up in the tropical stratosphere, called the Quasi-Biennial Oscillation (QBO), affects significant year-to-year changes in both the North Pacific and North Atlantic storm tracks.

https://research.noaa.gov/News/NewsArchive/LatestNews/TabId/684/ArtMID/1768/ArticleID/13338/To-improve-seasonal-storm-track-forecasts-look-to-the-tropical-stratosphere.aspx

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Posted
  • Location: Camborne
  • Location: Camborne

GRACE Mission: 15 Years of Watching Water on Earth

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Melting ice sheets: Antarctica is one of the world's toughest places to collect data, and Greenland isn't far behind. Yet we need to know how fast these ice sheets are melting to better understand rates and variations of sea level rise around the world. Scientists studying ice sheets and glaciers were among the first to start working with GRACE data to extract the information they needed. In the mid-2000s, Jianli Chen (University of Texas at Austin); Isabella Velicogna (University of California, Irvine); and the late John Wahr showed that ice losses from Greenland and Antarctica were dramatically larger than previously estimated, using estimates of the changing height of the ice sheets and other types of data. Since GRACE launched, its measurements show Greenland has been losing about 280 gigatons of ice per year on average -- a bit less than twice the weight of Mt. Everest -- and Antarctica has lost slightly under 120 gigatons a year. There are indications that both melt rates are increasing.

https://www.nasa.gov/feature/jpl/grace-mission-15-years-of-watching-water-on-earth

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Posted
  • Location: Camborne
  • Location: Camborne

Stronger evidence for a weaker Atlantic overturning circulation

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Through two new studies in Nature, the weakening of the Gulf Stream System is back in the scientific headlines. But even before that, interesting new papers have been published – high time for an update on this topic.

http://www.realclimate.org/index.php/archives/2018/04/stronger-evidence-for-a-weaker-atlantic-overturning-circulation/

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Posted
  • Location: Camborne
  • Location: Camborne

Reversing Earth’s Spin Moves Deserts, Reshapes Ocean Currents

A climate model with reversed rotation of Earth helps climatologists and oceanographers understand why our planet is the way it is and reveals how different it could have been.

https://eos.org/articles/reversing-earths-spin-moves-deserts-reshapes-ocean-currents

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Posted
  • Location: Camborne
  • Location: Camborne

Flooding Hot Spots: Why Seas Are Rising Faster on the U.S. East Coast

Scientists are unraveling the reasons why some parts of the world are experiencing sea level increases far beyond the global average. A prime example is the U.S. Eastern Seaboard, which has been experiencing “sunny day flooding” that had not been expected for decades.

https://e360.yale.edu/features/flooding-hot-spots-why-seas-are-rising-faster-on-the-u.s.-east-coast

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Posted
  • Location: Camborne
  • Location: Camborne

Mechanisms Governing the Development of the North Atlantic Warming Hole in the CESM-LE Future Climate Simulations

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A warming deficit in North Atlantic sea surface temperatures is a striking feature in global climate model future projections. This North Atlantic warming hole has been related to a slowing of the Atlantic meridional overturning circulation (AMOC); however the detailed mechanisms involved in its generation remain an open question. An analysis of the Community Earth System Model Large Ensemble simulations is conducted to obtain further insight into the development of the warming hole and its relationship to the AMOC. It is shown that increasing freshwater fluxes through the Arctic gates leads to surface freshening and reduced Labrador Sea deep convection, which in turn acts to cool Labrador sea surface temperatures. Furthermore, resulting changes in surface ocean circulation lead to enhanced transport of cooled Labrador Sea surface waters into the interior of the subpolar gyre and a more zonal orientation of the North Atlantic Current. As a result, there is an increase in ocean advective heat flux divergence within the center of the subpolar gyre, causing this warming deficit in North Atlantic sea surface temperatures. These local changes to the ocean circulation affect the Atlantic Meridional Overturning Circulation (AMOC) and lead to its slowdown.

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0635.1

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Posted
  • Location: Camborne
  • Location: Camborne

Hurricane Harvey links to Ocean Heat Content and Climate Change Adaptation

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Abstract

While hurricanes occur naturally, human‐caused climate change is supercharging them and exacerbating the risk of major damage. Here, using ocean and atmosphere observations, we demonstrate links between increased upper ocean heat content due to global warming with the extreme rainfalls from recent hurricanes. Hurricane Harvey provides an excellent case study as it was isolated in space and time. We show that prior to the beginning of northern summer of 2017, ocean heat content was the highest on record both globally and in the Gulf of Mexico, but the latter sharply decreased with hurricane Harvey via ocean evaporative cooling. The lost ocean heat was realized in the atmosphere as moisture, and then as latent heat in record‐breaking heavy rainfalls. Accordingly, record high ocean heat values not only increased the fuel available to sustain and intensify Harvey, but also increased its flooding rains on land. Harvey could not have produced so much rain without human‐induced climate change. Results have implications for the role of hurricanes in climate. Proactive planning for the consequences of human‐caused climate change is not happening in many vulnerable areas, making the disasters much worse.

Plain Language Summary

Human‐induced climate change continues to warm the oceans which provide the memory of past accumulated effects. The resulting environment, including higher ocean heat content and sea surface temperatures, invigorates tropical cyclones to make them more intense, bigger and longer lasting, and greatly increases their flooding rains. The main example here is hurricane Harvey in August 2017, which can be reasonably isolated in terms of influences on and by the environment. Hurricanes keep tropical oceans cooler as a consequence of their strong winds that increase evaporation. Here we show for the first time that the rainfall likely matches the evaporation and the corresponding ocean heat loss. Planning for such supercharged hurricanes (adaptation) by increasing resilience (e.g., better building codes, flood protection, etc.) and preparing for contingencies (such as evacuation routes, power cuts, and so forth) is essential but not adequate in many areas, including Texas, Florida and Puerto Rico where Harvey, Irma and Maria took their toll.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018EF000825

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Posted
  • Location: Camborne
  • Location: Camborne

2016 Arctic heat would have been virtually impossible without global warming

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In the fall of 2016, the Arctic experienced heat that was so extreme that one expert called it a black swan event. That warmth helped set a new annual temperature record that was double the magnitude of the record set the year before. New NOAA-led research confirms that the event could not have happened without human-caused global warming and sea ice loss.

https://www.climate.gov/news-features/featured-images/2016-arctic-heat-would-have-been-virtually-impossible-without-global

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Posted
  • Location: Sheffield
  • Location: Sheffield

published May 7th 2018 - Powerful hurricanes strengthen faster now than 30 years ago

https://www.pnnl.gov/news/release.aspx?id=4504

While many factors are at play, the chief driver is a natural phenomenon that affects the temperature of the waters in the Atlantic where hurricanes are powering up, according to scientists at the U.S. Department of Energy's Pacific Northwest National Laboratory and the National Oceanic and Atmospheric Administration.

They found that a climate cycle known as the Atlantic Multidecadal Oscillation or AMO is central to the increasing intensification of hurricanes, broadly affecting conditions like sea temperature that are known to influence hurricanes

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

The next thing to discover is whether the AMO is the Dog or the tail?

We just saw a fall off in Storms ( 2005-2016) under the AMO forcing that is supposed to see storms intensify as the imbalances between tropical Atlantic/Pacific basins fought to return to some kind of Parity. At the same time we saw Pacific typhoon/cyclones/hurricanes undergo changes both to the speed of their formation and the time they spent as 'Majors'.

he return to parity in the tropical basins seems to have allowed us to return to an active Atlantic Hurricane season ( let's see what this summer brings?) and it has seemed to suggest that the changes that were noted in the Pacific have now transferred into our Basin with last year seeing plenty of storms 'bomb' into Majors when unexpected to be doing so over that time period and also break records for remaining as majors longer than other storms were able?

If the AMO is just a nice way of noting where high, and low, pressure predominates then wider changes to the circulation of the northern hemisphere may see it move away from its old cycle of flips and returns. I think it is already overdue a flip?

We appear stuck in a position where the positioning of the jet in the Pacific can bring changes to our pattern by the peturbations set up as the jet encounters the Rockies. This seems to mean that we see a similar pattern of peaks and troughs from the mid west through into Europe .Changes to the sinuosity of the Jet means that changes in amplitude and/or wavelength can make a lot of difference depending where you are compared to the jet ( north or south of it, going into a curve or exiting a curve?)

If we see the temp/pressure gradient between the pole an equator lessen further then you would imagine the amplitude growing larger as the jet slows down even more? We may even see times where wind speeds drop below that of the jet leaving us with just unconnected 'Jet Streaks' where once a continuous band/river of wind used to flow?

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Posted
  • Location: Camborne
  • Location: Camborne

Quantifying climate feedbacks in polar regions

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The concept of feedback is key in assessing whether a perturbation to a system is amplified or damped by mechanisms internal to the system. In polar regions, climate dynamics are controlled by both radiative and non-radiative interactions between the atmosphere, ocean, sea ice, ice sheets and land surfaces. Precisely quantifying polar feedbacks is required for a process-oriented evaluation of climate models, a clear understanding of the processes responsible for polar climate changes, and a reduction in uncertainty associated with model projections. This quantification can be performed using a simple and consistent approach that is valid for a wide range of feedbacks, offering the opportunity for more systematic feedback analyses and a better understanding of polar climate changes.

https://www.nature.com/articles/s41467-018-04173-0

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Posted
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
  • Weather Preferences: Sunshine and 15-25c
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)

caught the tail end of a discussion on tv here ..where climatologists stated that models have been over estimating warming impact of co2 by 40%..does anyone know which scientific studies  they were referring to?

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Posted
  • Location: Near Newton Abbot or east Dartmoor, Devon
  • Location: Near Newton Abbot or east Dartmoor, Devon
8 hours ago, cheeky_monkey said:

caught the tail end of a discussion on tv here ..where climatologists stated that models have been over estimating warming impact of co2 by 40%..does anyone know which scientific studies  they were referring to?

That's a bit vague. Which climatologist(s)? If it was Tim Ball then LOL!

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