A powerful national device: Earth system numerical simulation device

The "Earth System Numerical Simulation Device" is a major national scientific and technological infrastructure project deployed and constructed by the National Development and Reform Commission during the "12th Five-Year Plan" period. It is also the first large-scale scientific device for simulating the earth system with independent intellectual property rights successfully developed in my country. It is named "Huan". The device mainly uses supercomputers to perform large-scale numerical calculations to reproduce the earth's past, simulate the earth's present, and predict the earth's future, thereby conducting targeted "earth experiments". This major national device will also play an important role in research on carbon neutrality, climate change, etc.

On June 23, 2021, the Earth System Numerical Simulation Facility was put into trial operation, providing meteorological and environmental support for major events such as the 100th anniversary of the founding of the Party, the Beijing Winter Olympics and the Winter Paralympics, and achieved good results. On October 17, 2022, the Earth System Numerical Simulation Facility passed the national acceptance and was officially opened for operation.

| What is the Earth System Numerical Simulator

As the name implies, it is a device used to simulate the earth's ecosystem. Although the Earth System Numerical Simulation Device is called a device, in fact, it is not a large device similar to a supercomputer as we are familiar with, but a device that combines software and hardware and takes software as the core. Researchers need to use these software deployed on the supercomputer and some related numerical values ​​to carry out research.

Simply put, it is to put the simulated "Earth" into the laboratory to see how the natural system on the "Earth" responds to global warming caused by different carbon dioxide emissions, and finally determine an appropriate temperature rise target. Note that the "Earth" mentioned here is not a real Earth, but a digital Earth based on various physical and mathematical equations.

| How does the Earth System Numerical Simulator work?

Understanding the basic laws of the earth's various spheres is the basis for researchers to use the device for simulation. The earth is composed of five major spheres, namely the atmosphere, hydrosphere, cryosphere, lithosphere and biosphere. The simulation process of the device is actually simulating the interaction between the five spheres on the earth. For example, between the atmosphere and the cryosphere, the ice and snow will melt after the temperature of the atmosphere rises. After the ice and snow melt, the albedo of the surface is greatly reduced, and the surface and the atmosphere will absorb more sunlight, causing the temperature to rise further, which will cause the snow to melt further. Among the activities of the spheres, human activities are very important and very complex. Our production and life will have a series of impacts on the various spheres of the earth.

Due to the complexity of the interconnected nature of all things in nature, it is impossible to include all mathematical equations of all spheres in one code set at once. In order to simplify the solution of the problem, people first build a model to describe a single sphere, and then organically combine the independently running models through a "coupler". The coupler is like a switching workshop in a huge factory, where the exchange of materials and energy between the spheres takes place, thereby coupling the models of the atmosphere, ocean, and land surface, and simulating the evolution process of nature to the greatest extent.

After obtaining this digital "Earth", by inputting the observation data at a certain moment and performing large-scale numerical calculations on a supercomputer, we will be able to deduce the changes in the different spheres of the Earth, thereby recreating the Earth's past, simulating the Earth's present, and predicting the Earth's future, and thus conduct targeted "Earth experiments."

| The international status of “Huan”

As a reflection of a country's comprehensive national strength, scientists from various countries are actively developing their own numerical models. In 2022, my country also submitted an Earth system model to participate in the Sixth International Coupled Model Intercomparison Program (CMIP6). This simulation experiment has about 112 climate model versions from 33 institutions around the world registered to participate, the largest number ever. Although there are so many numerical models in the world, most of them are still climate system models. Looking around the world, only developed countries such as the United States, Japan, and Europe have built special simulation devices for the Earth system that combine software and hardware. The National Center for Atmospheric Sciences (NCAR) of the United States has developed an excellent Earth simulation system with its long-term world-leading numerical simulation device. Therefore, these countries dominated the design of the Intergovernmental Panel on Climate Change (IPCC) climate change projection experiment and the writing of the assessment report.

In this comparative experiment, my country's independently developed Earth System Model CAS-ESM2.0 performed well, and its simulations of indicators such as the global vegetation index and total primary productivity ranked among the best in the world. It is worth mentioning that CAS-ESM is the core model software of the Earth Simulation Laboratory "Huan".

In addition to software support, the domestically produced chips used by Huan provide super computing power support for the ultra-complex earth system model. The high-performance computer system "Silicon Cube" developed specifically for Huan for earth science has a computing peak of no less than 15PFlops. Its computing power in one minute is equivalent to 7.2 billion people in the world using calculators to calculate continuously for 4 years at the same time. The entire system has more than 3,000 water-cooled computing nodes, which are connected to each other using HDR InfiniBand high-speed network with a bandwidth of up to 100Gbps. In addition, the "Silicon Cube" database has 80PB of storage space, which can hold the collection data of about 13 national libraries to save observation and simulation data of various spheres.

| Application areas of “Huan”

1. Addressing climate change

Whether it is greenhouse gas accounting, future warming projections, or possible responses of other spheres to warming such as sea level rise and cryosphere changes, they all require the support of simulation research on the Earth system model that includes the complete spheres, especially the simulation of carbon and nitrogen cycles and biogeochemical processes. This is precisely the advantage of "Huan".

Therefore, "Huan" will be committed to relevant research work such as "carbon neutrality" and climate change to provide scientific and technological support for national strategic needs.

2. Predicting ocean climate change

The El Niño and Southern Oscillation (ENSO) phenomenon is the most significant change signal of the climate system on the interannual scale. It reaches its mature phase in the northern hemisphere winter and has an important impact on the climate in eastern my country in the following summer (such as the intensity of the summer monsoon and typhoon activity). It is the main source of signals for cross-season climate forecasts.

Using high-performance climate models to predict the temperature, drought and flood of target areas in a few months to a year has become the mainstream direction of international climate prediction research. "Huan" will focus on short-term climate prediction issues that are closely related to the national economy and people's livelihood, and use more sophisticated and complete earth system models to capture more comprehensive prediction signals, providing scientific and technological support for comprehensively improving my country's short-term climate prediction capabilities.

3. Disaster prevention and mitigation

With the development of social economy, environmental pollution problems have become increasingly prominent. Various problems such as fine particulate matter (PM2.5), ozone, sandstorms, acid rain, etc. coexist, causing great harm to human health and the ecological environment.

Numerical models can trace the source of pollutants, forecast and warn of heavy pollution weather processes, and evaluate the effectiveness of various pollution control measures, thereby assisting in the formulation of air pollution control plans. However, air pollution issues involve dynamic processes from the global to the city scale in space, chemical processes on the millisecond scale, and transport processes on the annual scale in time, which is a major challenge for numerical simulation.

"Huan" includes a high-precision atmospheric pollution model subsystem for my country's region, which has the ability to completely simulate the formation process of atmospheric pollutants at high resolution, and can provide an advanced experimental platform for the accurate forecast of my country's atmospheric pollution and the development of refined prevention and control technologies.

In addition, "Huan" can also support high-resolution simulation experiments of disastrous weather such as heavy rain, typhoons, sandstorms, extreme heat waves and cold waves, provide an advanced scientific platform for the research and development of disastrous weather forecasting methods and tools, and provide scientific and technological support for major national needs such as disaster prevention and mitigation.

In short, the birth of "Huan" will significantly enhance the overall innovation capacity of my country's earth sciences and play an important role in solving major scientific problems in my country, such as disaster prevention and mitigation, environmental governance, sustainable development and ecological security. It will provide strong scientific and technological support for us to achieve major strategic goals such as "carbon neutrality" and "beautiful China".

(Pictures from the Internet)

Author | Gu Junzhe

Master of Computer Science and Technology. After graduation, he engaged in the collection and organization of network information, paid attention to popular science knowledge, and explored cutting-edge technology.