What does the weather forecast symbol in Apple's mobile phone mean?

I believe many people will check the temperature of the day, and most fruit powders like to check the weather in their own weather applications. Many people will question what common and unconscious weather icons symbolize, as shown below:

Weather forecast (measurement) or meteorological forecast (measurement) is to use modern science and technology to predict the state of the earth's atmosphere in a certain place in the future. Since prehistoric times, human beings have begun to predict the weather and arrange their work and life accordingly (such as agricultural production and military operations). Today's weather forecast mainly uses the collection of a large number of data (temperature, humidity, wind direction and speed, air pressure, etc. ), and then use the current understanding of atmospheric processes (meteorology) to determine future air changes. Because of the chaos of the atmospheric process and the fact that science has not fully understood the atmospheric process today, there will always be some errors in the weather forecast.

gather data

The most traditional data are data such as air pressure, temperature, wind speed, wind direction and humidity collected by professionals, enthusiasts, automatic weather stations or buoys on the ground or at sea. The World Meteorological Organization coordinates the timing of these data collections and sets standards. These measurements are made every hour (METAR) or every six hours (SYNOP).

Using a probe balloon, you can climb all the way to the tropopause and collect data on temperature, humidity and wind speed.

Data from meteorological satellites are becoming more and more important. Meteorological satellites can collect data from all over the world. Their visible photos can help meteorologists study the development of clouds. Their infrared data can be used to collect the temperature of the ground and cloud top. By monitoring the development of clouds, we can collect the wind speed and direction at the edge of clouds. However, because the accuracy and resolution of meteorological satellites are not good enough, ground data is still very important.

Weather radar can provide information about precipitation area and intensity. Doppler radar can also measure wind speed and direction.

Data assimilation

North American pressure map in 2008, Nordic satellite cloud image

In the process of data assimilation, the collected data are combined with the numerical model used for prediction to produce meteorological analysis. The result is the best estimate of the current atmospheric state, which is a three-dimensional representation of temperature, humidity, air pressure, wind speed and direction.

numerical weather forecast

Numerical weather forecasting uses computers to simulate the atmosphere. Based on the results of data assimilation, it calculates the changes of the atmosphere with time according to the results of physics and fluid mechanics. Because the equations of fluid mechanics are very complicated, only supercomputers can be used for numerical weather prediction. The output calculated by this model is the basis of weather forecast.

Output processing

The original output of model calculation generally needs to be processed to become a weather forecast. These treatments include using statistical principles to eliminate the deviation in known models or making adjustments with reference to the calculation results of other models.

In the past, meteorologists had to do their own processing work, but today's weather forecast over 24 hours mainly uses a variety of different models to synthesize the results. Meteorologists must also analyze the predicted model data so that end users can understand it. In addition, the resolution of weather forecast models is generally not particularly high. Local meteorologists must also consider the influence of the region through local experience to make the local weather forecast more accurate. However, with the continuous refinement of the weather forecast model, this workload is getting smaller and smaller.

show

For end users, the display of weather forecast is the most important in the whole process. Only by knowing what information the end user needs and how to convey it to the end user easily can this task be completed.