Probability in the atmospheric circulation dictating the Weather (by Diego Fdez-Sevilla)
In a previous post I have shared the “gaming” side of searching for patterns trying to identify similarities and differences between images representing meteorological variables.
Climatic events can be forecast with more or less accuracy by applying statistical analyses and modelling trying to identify the highest probable scenario to be found in our weather for short, medium and long terms.
The variables contemplated, with their synergies and interrelations, are so many that the effectiveness of weather forecast reach its highest in the short term and the uncertainty increases with the distance in time between the moment of calculation and the day for which the conditions are being forecast.
One of the reasons behind such uncertainty is that the atmosphere is an open environment in which climatic events form and move freely, gaining strength or dissipating its energy as the result of interacting with their surroundings.
In Oct 2014, researchers led by Masato Mori of the Atmosphere and Ocean Research Institute, the University of Tokyo, ran multiple simulations linking the observed decline in sea ice in the Arctic since 2004 with an increased probability of the occurrence of persistent atmospheric circulation patterns, known as blocking patterns. A study published online in Nature Geoscience.
They discovered that atmospheric blocking patterns, leading to cold air transport and severe winter conditions occurred twice as often in the low sea ice scenario model runs. This approach showed that as a result of sea ice reduction in the Arctic, Barents and Kara seas, the probability of severe winters has more than doubled across Eurasia.
This new study agrees with previous work that the decline in sea ice cover in the Barents-Kara Sea area in early winter has led in recent years to unusually cold winters throughout Eurasia, including the UK, according to Colin Summerhayes, Emeritus Associate of the Scott Polar Research Institute in the UK.
Summerhayes explains that the warming of the atmosphere associated with the absence of sea ice weakens the high level winds of the polar vortex. That in turn leads to meandering of the jet stream, with the meanders becoming stuck which is what meteorologists call ‘blocking’. This pull cold air south out of the Arctic, and because the system is stuck in position, the cold air supply can last quite a while.
The rise in blocking patterns correlates closely with the extra heating being delivered to the Arctic by climate change, according to the research which is published in the journal Proceedings of the National Academies of Science (PNAS). Coumou and his colleagues argue there are good physical reasons to think there is a causal link, because the jet streams are driven by the difference in temperature between the poles and the equator. As the Arctic is warming more quickly than lower latitudes, that temperature difference is declining, providing less energy for the jet stream and its meanders, which are called Rossby waves.
Prof Ted Shepherd, a climate scientist at the University of Reading, UK, but not involved in the work, said the link between blocking patterns and extreme weather was very well established. He added that the increasing frequency shown in the new work indicated climate change could bring rapid and dramatic changes to weather, on top of a gradual heating of the planet. “Circulation changes can have much more non-linear effects. They may do nothing for a while, then there might be some kind of regime change.”
I believe that these new studies are starting to identify possible alterations in atmospheric circulation that would affect the probability for climatic events to form and move in the North Hemisphere. The study of the origin behind such behaviour have led me to propose for open discussion the hypothesis of facing an increase in atmospheric energy content due to increases in CO2 and Water vapour. An increase in the energy been contained in the atmosphere would lead to a decrease in the differential energy gradients between atmospheric surroundings and weather systems. Ultimately, weather systems would not dissipate easily their energy into the surrounding atmosphere. You can find a more in depth discussion here and here.
In such scenario, how much would it be affected the probability of seeing same climatic events (Low and High pressures) happening at same locations in the Hemisphere but in different days?
What would it be the probability of seeing “two Low pressure events” happening at the same time, in same locations of the North Hemisphere in “two different days” separated by 8 months? Sure it is not such a big deal, just curious.
And then, what would it be the probability of seeing “two Low pressure events” happening at the same time in same locations of the North Hemisphere in “three different days” separated by 8th months and 3 months?
And the probability of seeing “three Low pressure events” happening at the same time, in same locations of the North Hemisphere in “two different days” separated by 3 months?
Just a thought.
- Climate and Weather Development. Spot the differences between the pictures. (by Diego Fdez-Sevilla) December 15, 2014
- Why there is no need for the Polar Vortex to break in order to have a wobbling Jet Stream and polar weather? (by Diego Fdez-Sevilla) November 14, 2014
- (Updated 22/Dec/14) New theory proposal to assess possible changes in Atmospheric Circulation (by Diego Fdez-Sevilla) October 21, 2014
- What type of Polar vortex configuration can we expect for this winter? (by Diego Fdez-Sevilla) October 7, 2014
- Weather patterns and extreme events (by Diego Fdez-Sevilla) August 14, 2014
- Met Office. The Recent Storms and Floods in the UK (Feb 2014) (by Diego Fdez-Sevilla) February 17, 2014