You know the weather forecast is not accurate, but do you know why?

Weather forecast is to predict the weather in the next few days. The traditional weather forecast is based on semi-experience and semi-theory, so the error is relatively large. Now, with the help of satellite images, the weather forecast in three days has been quite accurate, and many people have become accustomed to listening to the weather forecast every day in order to decide the arrangement of various activities according to the weather conditions.

Why is the weather predictable?

Weather is closely related to people's lives, and actively understanding the weather has become a part of people's lives. As the saying goes, "something unexpected happens in the sky", and the wind and rain are unpredictable. Then why is the weather predictable?

In fact, the weather changes regularly. Weather forecast is to make use of meteorological data and apply the principles and methods of meteorology to predict the weather in a certain period in the future according to the weather conditions.

Weather forecasts have been around since ancient times. Through long-term observation and experience accumulation, the ancient working people summed up many proverbs about the weather. The typical weather forecast is "stay indoors at sunrise and travel thousands of miles at sunset". But proverbs are all based on experience, so they are still limited, and some of them are even wrong.

The current weather forecast is made by the Meteorological Observatory and released to the public. At present, the main ways to publish weather forecast are TV, Internet, newspapers, SMS, WeChat and so on.

An important tool of weather forecast is weather map. The weather map has the movement law of the weather system, and meteorologists make predictions about the future weather conditions accordingly. In addition, meteorologists should also study satellite cloud images and modify the prediction results in combination with local characteristics and experience.

As for the length of the time limit, weather forecasts are usually divided into three types: short-term weather forecasts within 3 days; 9-day medium-range weather forecast; The long-term weather forecast is 15 days or more. CCTV mainly broadcasts short-term weather forecast every day.

weather forecast

Why is the accuracy of long-term weather forecast not high?

If we pay attention to the timeliness of weather forecast, we will find that we usually hear 12 hour forecast and 24 hour forecast. In addition, you will hear 48-hour forecasts and 72-hour forecasts, but rarely hear longer-term weather forecasts.

In fact, meteorological stations also make medium-and long-term weather forecasts. For the public, short-term weather forecast is enough, but the main reason is that the accuracy of medium and long-term weather forecast is much worse than that of short-term weather forecast. Internationally, the weather forecast within 10 days has certain accuracy, but the forecast over two weeks, that is, the long-term weather forecast, has great uncertainty. This is because chaos is a common phenomenon in weather systems, and it shows an inherent randomness in deterministic systems. Its external performance is very similar to pure random motion, that is, unpredictable. Chaotic systems are very sensitive to small initial value changes or disturbances. No matter how small the disturbance is, it will completely deviate from the original evolution direction after a long time. This feature of weather system was first discovered by Lorenz, a professor of meteorology at MIT. Lorenz has been using computers to simulate the weather process, so as to carry out numerical weather forecasting experiments. One day in 196 1, in order to save trouble, he kept the original initial data with 6 decimal places and only used 3 digits instead of calculation. He was surprised when he came back from a cup of coffee. At first, the calculation results were not much different from those before, but the later the calculation results were different, so that it was 108 thousand miles later. After checking every detail in the calculation, it is found that the small differences in the initial data will accumulate in the calculation and grow at an extremely fast speed, eventually resulting in huge differences.

In 1963, Lorenz expressed this conclusion as the butterfly effect, that is, "a butterfly flapping its wings occasionally in the Amazon rainforest of South America is likely to trigger a tornado in Texas within two weeks." Therefore, it is difficult to make an accurate forecast of the long-term weather process.

Graphical symbols in weather forecast

Man cannot completely control the weather.

Maybe you had a dream that human beings can manipulate the weather, and the weather controller can decide whether a city is sunny or rainy by pressing a button according to the actual situation in various places. When there is drought, it will create a timely rain; If there is too much rain, drive away the dark clouds.

This scene is really imagined by science fiction writers. According to the present technical conditions, human beings can really influence the weather. However, what human beings can do now is not to control the weather system, but to guide the weather process according to the situation. In other words, weather modification must meet certain conditions. For example, we can't make thunderstorm clouds in a clear sky; Even if it is cloudy, if the cloud is thin, we can't let it rain.

In the past, weather modification was mainly used to combat drought, but now it is gradually extended to forest fire fighting and air purification, and Shanghai also uses artificial rainfall to alleviate urban high temperature. Now, there are still scientists trying to artificially eliminate lightning and artificially weaken typhoons. However, their role is limited after all, and the scope of their influence is also partial.

I am afraid that human beings will never be able to manipulate the weather at will, so our best strategy is to conform to nature and be kind to it.

Artificial rainfall operation