In the future, weather forecasts that provide storm warnings and help us plan our daily lives could arrive up to five days earlier before numerical weather forecasts reach their limits, the researchers say.
"The obvious question that has been raised in our entire field right from the beginning is: what is the ultimate limit on which we can predict the daily weather in the future?" Said Fuqing Zhang, respected professor of meteorology and economics Atmospheric Science and Director of the Center for Advanced Data Assimilation and Predictability Techniques in Penn State. "We believe that we have reached this limit and average about two weeks."
For the daily weather in the middle latitudes, where most of the world's population lives, nine to ten days of reliable forecasts are possible today. According to a study published in the online Journal of the Atmospheric Sciences the new technology could be extended for another four to five days in the coming decades.
Research initially confirms a long hypothetical predictability limit for weather forecasting In the 1
"Edward Lorenz has proven that the weather can not be predicted beyond a certain time horizon," he told Kerry Emanuel, Professor of Atmospheric Science at MIT and co-author of the study. "Our research shows that this horizon of weather predictability is about two weeks and remarkably close to Lorenz's estimate."
Unpredictability of weather evolution means that even with perfect models and understanding of initial conditions, there is a limit to how far ahead accurate predictions are possible, scientists said.
"We used modern models to answer this most basic question," said Zhang, the lead author of the study. "I think we will refine this answer in the future, but our study clearly shows that there is a limit, although we still have plenty of room to improve the forecast before we reach the limit."
To test the limit, Zhang and his team used the world's two most advanced numerical weather prediction modeling systems – the European Center for Medium Distance Weather Forecasting and the next generation global forecasting system.
They provided an almost perfect picture of the initial conditions and tested how the models can create two real weather events, a cold spell in northern Europe and floods in China. The simulations were able to predict the weather patterns with a reasonable accuracy of up to two weeks, the scientists said.
Improvements in daily weather forecasts affect things like storm evacuations, energy supplies, agriculture and forest fires.
"We have made significant advances in weather forecasting over the last few decades and are now able to predict the weather with great confidence five days in advance," Zhang said. "If we can predict further days with high security in the future, this would have enormous economic and social benefits."
The researchers said that better data collection, algorithms for integrating data into models, and improved computational power are needed to conduct experiments to further improve our understanding of the initial conditions.
"To achieve this additional predictability limit, coordinated efforts by the entire community are required to design better numerical weather models, improve observations, and make better use of observations with advanced data assimilation and data processing techniques," Zhang said.
Bridging the gap between radar meteorology / hydrology / engineering and weather forecast
Fuqing Zhang et al., What is the predictability limit of weather in the midlatitude?, Journal of the Atmospheric Sciences (2019). DOI: 10.1175 / JAS-D-18-0269.1
Predictability limit: Scientists encounter weather forecasts (2019, April 15)
retrieved on April 16, 2019
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