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The problem with long-term weather forecasting …

German researchers say more observational data from Arctic is needed

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Understanding the dynamic processes of the Arctic could help generate more accurate long-term forecasts for the mid-latitudes.

By Summit Voice

FRISCO — While some observable atmospheric and ocean patterns can help forecasters predict general weather patterns on a seasonal basis, meteorologists and climatologists are still from from being able to predict the intensity of winter weather or drought a year or two in advance.

Long-term forecasts would be invaluable to energy and agriculture sectors, for example, but German climate researchers recently concluded that here is still a long way to go before reliable regional predictions can be made on seasonal to decadal time scales.

After evaluating 23 climate models, the researchers said none of them is able to forecast the weather-determining patterns of high and low pressure areas to the degree  that the probability of a cold winter or a dry summer can be reliably predicted.

“Short-term weather forecasts are now very reliable. The problems for seasonal and decadal … predictions refer to the enormous variability and the broad range of feedback effects to which atmospheric circulation is subjected,” said Dörthe Handorf, a meteorologist with the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association.

The Earth’s weather is significantly determined by large-scale circulation patterns of the atmosphere. including the North Atlantic oscillation, which influences the strength and location of the westerly winds over the North Atlantic and therefore determines the tracks of the low pressure systems over north and central Europe.

Circulation patterns of this nature, also referred to as “teleconnection”, are distributed over the entire globe and determine the spatial and temporal distribution of areas of high and low pressure over large distances. Scientists describe meteorological centers of action, which determine the weather of an entire region. In the case of the North Atlantic oscillation, the known weather centers are the Icelandic Low and the Azores High.

To test the forecast quality of the 23 most important climate models, the AWI scientists investigated how well they were able to reproduce atmospheric teleconnection patterns over the past 50 years. A total of 9 known circulation patterns were investigated retrospectively, four in-depth.

The study concluded that the spatial distribution of atmospheric teleconnection patterns is already described very well by some models. However, none of the models were able to reliably reproduce how strong or weak the Icelandic Low, Azores High and other meteorological centers of action were at a particular time over the last 50 years, i.e. the temporal distribution patterns.

The Arctic plays a key role in optimizing climate models. It is one of the most important drivers of our climate and weather and is at the same time one of the regions in which the climate is currently changing the most.

The high latitudes are also so inhospitable that data on the Arctic is sparse. Future research work of the Potsdam scientists will go in two directions. First, they are developing a climate model which can resolve  the  small-scale, weather-determining processes in the Arctic particularly well.

The TORUS project is funded by the Federal Ministry for Education and Research (BMBF) as part of the “MiKlip – A Research Project on Decadal Climate Prediction” research program and coordinated by Handorf.

However, since model improvements are only possible if comprehensive  data records in high quality are available, a large international field campaign is planned in the Arctic for the period 2018-2019. It will demand  a lot from the participating scientists because part of the field campaign is to be an international Arctic drift station in which a team of researchers will drift through the Arctic Ocean with the sea ice in the Arctic winter for several months.

“Climate researchers throughout the world are currently working on increasing the resolution of their models and the performance of their climate computers,”said  Handorf, who has worked on questions of climate variability since 1997.

“But it will not be enough to increase the pure computer power. We must continue to work on understanding the basic processes and interactions in this complicated system called ‘atmosphere.’ Even a high power computer reaches its limits if the mathematical equations of a climate model do not describe the real processes accurately enough.”

 

 

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