Every Friday afternoon, Shen Xueshun, a member of the Chinese Academy of Engineering and the head of the Global Numerical Weather Prediction System Engineering and Technology Team at the China Meteorological Administration, gathers team members to discuss various technical issues encountered in their work.
From ancient times to the present, the exploration of weather forecasting has never ceased. The emergence of numerical prediction has finally made "computing weather" possible.
However, this has been a challenging and lengthy journey. To develop a global numerical weather prediction system with independent intellectual property rights, Shen Xueshun and his team spent a decade sharpening their skills, pooling their wisdom, and overcoming one obstacle after another.
In May 2023, with the official operation of the China Meteorological Administration's Global Assimilation Forecast System, the forecast days available in the Northern Hemisphere exceeded 8 days. For each day the forecast availability in the Northern Hemisphere increases in international advanced business centers, it typically takes an average of 10 years. China, on the other hand, increased the number of days from 6.1 to the current 8.1 in just 14 years.
The leap of "two days" carries the struggles and perseverance of team members over the years. At a recent National Engineering Award ceremony, the innovative team was awarded the title of "National Outstanding Engineering Team."
Upon returning from receiving the award, the team immediately plunged back into the continuous development and optimization of the Earth System Model. "Our most important task now is to comprehensively carry out the development of the Earth System Model based on the next generation model, accelerate the improvement of meteorological scientific and technological innovation levels, and contribute the 'core' strength to the early establishment of a meteorological power," Shen Xueshun said.
Numerical prediction is a forecasting technique based on objective quantitative calculations of future weather evolution using mathematical physics methods. As the core technology of meteorological operations, it is hailed as the "chip" of meteorological endeavors.
Over a decade ago, meteorologists faced a choice between introducing advanced mature numerical prediction models from abroad or independently developing domestic numerical prediction models.
"Every time we faced this choice, we firmly chose the latter," Shen Xueshun said. "Developing numerical prediction models with independent intellectual property rights is to avoid being 'strangled' by others."
Shen Xueshun recalled that in the past, China imported open-source models from Europe and the United States but could not obtain the key core technologies in numerical prediction models, resulting in a long-term lag in numerical prediction capabilities compared to developed countries.
Team member Sun Jian explained that numerical prediction models are complex, with close connections and multiple components within the system. Addressing the key challenges of numerical prediction technology and the computational issues brought about by resolution enhancements, the team broke through bottlenecks time and time again, continuously optimized parameters, "deconstructed" the model to truly enhance the overall performance of the prediction system. "The total code volume of the system exceeds 3 million lines, indicating the magnitude of the development difficulty," Sun Jian said.
The numerical prediction system has two core components: the model and assimilation. For Zhang Lin, a team member responsible for data assimilation, correctly assimilating each observational data into the model is crucial to effectively leverage the benefits of the observation network.
Zhang Lin explained that data assimilation is both a science and an art, as well as engineering. Like craftsmen, they have to identify small problems hidden in the complex system. This is akin to the butterfly effect, where even a tiny problem can lead to significant deviations in the model.
"Modeling is not achieved overnight, especially in four-dimensional variational aspects, where the technical development difficulty is significant. But each member of the team works diligently, not seeking ease but craftsmanship. In this way, we have climbed over one dangerous peak after another," team member Gong Jiandong said.
It is through years of perseverance day by day and year by year that the team has established a seamless numerical weather prediction business system from 0 to 15 days. Currently, China's global model prediction capability has reached the level of international advanced models, with regional model resolution increased from 10 kilometers to 1 kilometer, leading the world in the accuracy of forecasts for severe convective weather such as typhoons and heavy rain.
"These technological achievements have played an indispensable role in major events such as the 70th anniversary of the founding of the People's Republic of China, the 100th anniversary of the founding of the Communist Party of China, and the 2022 Beijing Winter Olympics," Sun Jian said.
Moreover, as the core support of the World Meteorological Center (Beijing), the China Meteorological Administration's Global Assimilation Forecast System can also provide meteorological disaster forecast and warning products for countries participating in the Belt and Road Initiative.
"In the future, we will continue to optimize model performance, making the 'wind and cloud' more predictable, and providing strong support for strengthening the first line of defense in meteorological disaster prevention and reduction," Shen Xueshun said.
