Forecasters look higher for clues to winter weather

October 12, 2015, Institute of Physics
Credit: Larisa Koshkina/public domain

Long-range winter weather forecasts could be twice as accurate by taking account of unusual winds miles up in the stratosphere, scientists have found.

Meteorologists at the University of Reading, European Centre for Medium-Range Weather Forecasts (ECMWF) and Environment Canada found that by taking account of changing winds in the , forecasters could be twice as certain of their predictions for between a fortnight and a month in advance.

The findings mean that forecasters can be more certain about predicting extreme winter weather up to four weeks before it happens, giving governments, businesses, and individuals more certainty when planning for extreme events, such as floods or snow storms.

The new research is published today in the journal Environmental Research Letters.

Dr Om Tripathi, from the Department of Meteorology, University of Reading, who led the research, said: "Forecasting the weather a full month ahead is a tough ask, but that's what businesses and emergency services really need to prepare for extreme winter weather.

"Accurate advance notice of prolonged cold spells, such as the 'polar vortex' that hit North America over the past two winters, can save lives and help keep power and transport networks running.

"Our latest findings should give forecasters more confidence when issuing some winter up to a month in advance."

High up in the stratosphere is the polar night jet stream, at around 40km (25 miles) above the surface of the Earth - around the height reached by record-breaking parachutist Felix Baumgartner.

Winds in the polar night jet stream usually blow from the west and have speeds of around 70mph. The research team found that during conditions in which the polar night jet stream wind speeds exceed 90mph, or reverse their direction to flow from the east, forecasts in both the stratosphere and troposphere (the layer of atmosphere closest to the ground), are more skillful.

While it was previously known that a sudden weakening of these winds, and subsequent warming of the stratosphere, was a source of predictability, the researchers found that the opposite was also true when the jet stream strengthened and the polar stratosphere was unusually cold. Such stratospheric conditions occur up to 3-4 times a winter, meaning that around one in five winter 'sub-seasonal' forecasts (those looking 2-4 weeks ahead) might benefit from this effect.

The strength of stratospheric winds can influence the position of the jet stream in the troposphere, having a major influence on weather across the North Atlantic, and allow freezing polar air to travel further south than would normally be expected.

The researchers examined 30 years' worth of past forecast data to see how the state of the stratosphere affected the accuracy of the forecast.

Dr Andrew Charlton-Perez, University of Reading, who co-authored the study, said: "We are only just beginning to learn how conditions in the stratosphere influence our weather several weeks later.

"The more we learn about these links, along with other processes in the tropical atmosphere and links between the land surface and the atmosphere, the more we can improve weather forecasts on this important sub-seasonal timescale."

Improving sub-seasonal forecasts is the focus of several current major international initiatives including the S2S project, sponsored by the World Meteorological Organisation. This research was part of the SNAP project, which contributes to this effort by working with researchers in seven countries on stratospheric predictability and its influence on the troposphere.

Explore further: Forecasters look higher to make better cold weather predictions

More information: Tripathi et al 2015 Environ. Res. Lett. 10 104007 DOI: 10.1088/1748-9326/10/10/104007

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ForFreeMinds
1 / 5 (2) Oct 12, 2015
Great! Some research that will actually improve our predictions of the weather and the climate. Now, what is it that affects the winds in the stratosphere, can we measure that, and add it to the predictions? This is actually useful, unlike most of the AGW research.
Returners
1 / 5 (3) Oct 13, 2015
I'm not necessarily sure how this will help in practical terms. Sure you can move things like heating oil in advance (and unfortunately energy companies will use this information to scalp consumers ahead of time,) but one of the biggest problems with the perpetual snow storms in the Midwest and New England states is that governments simply ran out of places to keep moving and piling the snow. Near one city, there was a snow mound left over from where they were dumping it, and it survived well into summer before melting.

I know of a way to help keep streets clear of snow fall; You build a network of pipes under the major roads and pump waste heat from power plants through the pipes. Now you have to do this gradually so you warm the street ahead of time enough to not heat-shock the asphault or concrete, but you could raise it's temperature to above freezing by doing this, without spreading corrosive salts and such.

Currently, waste heat is uselessly dumped into rivers.
Returners
1 / 5 (3) Oct 13, 2015
Now considering how much fuel it takes to operate snow plows and trucks to haul snow away, and in some cases barges when they run out of places on land to pile it up, etc....

It would make a lot of sense to divert waste heat water from energy companies and production facilities to pre-heat the roads to above freezing and keep them a few degrees above freezing all season long. I would imagine that this should be doable, at least on the most important roads.

Of course, melting-water ice is one of the most energy-consuming things imaginable, but wtf...you got the waste heat from combustion and other processes you are already doing anyway, yu may as well direct it to doing something useful.

Well, Canadians and Europeans already do cogeneration methods, so I'm not sure this is very useful to them since they probably already do this.

Here in America if something can theoretically be done backwards and inefficiently it probably is in fact being done backwards and inefficiently.
Returners
1 / 5 (3) Oct 13, 2015
You could also place solar-thermal collectors, tilted at appropriate angle for seasonal incidence of light, along the northern side of east-west stretches of road and collect this excess heat, using water or glycol to channel it into the foundation of the road. Since the correct incidence angle for northern lattitudes is very heavily tilted from the normal, snow will not accumulate on the collecting surface.

There are videos of people making home-made solar forced air heaters which work this way and saved half their heating bill.

The collectors would be designed so that during Summer a simple toggle mechanism could be used to flip the collecting surface over and no longer collect as much heat, or you could re-direct the heat somewhere else and use it for pre-heating in industrial processes, which would save energy usage in total.

there are a lot of things that governments and engineers could be doing which are simply not even considered apparently.
Returners
1 / 5 (3) Oct 13, 2015
Now any such collectors need to be build well above ground level so as to avoid accumulation of snow drifts.

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