Not long ago, typhoons Dusurui and Kanu hit successively, causing heavy casualties and property losses. Facing a disaster like a typhoon, imagine the following two situations: You can track the typhoon’s location and predicted path through mobile phones, TVs, and other devices. Gather necessary materials in advance for disaster preparedness. B: I only know there will be a typhoon this season, so judge based on experience. Everyone will choose A, right? That’s right, as important as emergency rescue and disaster relief is continuous monitoring and tracking of the weather, making accurate judgments, and issuing early warnings promptly. So, where does our weather data come from? A large part of the weather data comes from weather satellites in the sky. Let’s learn about weather satellites and their basic working principles!
Physical Basis: Remote Sensing
Weather satellites work through remote sensing, which means they can observe objects without touching them. Remote sensing uses non-contact methods to detect different attributes of objects. Although it sounds high-tech, remote sensing is a basic function of each of us. For example, when we were walking on the road, we suddenly heard footsteps behind us, and when we looked back, it was Xiao Li! This is where the ears and eyes activate remote sensing skills. Make the problem a little harder, though, and our innate remote-sensing skills need to be more. For example, is the white shirt Xiao Li is wearing today pure cotton, silk, or chemical fiber? You have to twist your hands to know this, but stretching out your hand becomes contact detection, not remote sensing.
Spectral Analysis for Remote Sensing
What to do? We can ask the instrument to help us observe the reflection spectrum of Xiao Li’s clothes. What does this word mean? When light shines on an object, some wavelengths (colors) of light will be absorbed, and some will be reflected. We use different wavelengths to illuminate it and will see different brightness. Draw the curve of brightness versus wavelength, which is the reflection spectrum. For example, leaves absorb red and blue light and reflect green light. The green we see is the approximate reflection spectrum of leaves. With the help of instruments, this spectrum can be further refined down to the wavelength. Different materials have distinct infrared spectra. Therefore, we can determine its components without manual twisting by examining Xiao Li’s white shirt in the infrared band.
Using Spectral Analysis for Weather Data
Objects emit electromagnetic waves. Cold objects have longer wavelengths, while hot objects have shorter wavelengths. The composition of matter determines the specific spectral distribution shown by these objects. Therefore, by observing the radiation spectrum of an object, its composition and temperature can be judged. In a mobile phone, each “white” pixel is made up of only three colors: red, green, and blue. However, sunlight can range from red to purple.
Weather Satellites’ Functionality
After understanding the basic principles of remote sensing, let’s look at how weather satellites do it. What weather satellites see Let’s design a weather satellite: What will we make it look like? What do you think? Since it is a weather satellite, at least it must be able to take common visible light satellite cloud images. The weather performance is very intuitive. We can see the distribution and thickness of clouds, and if we continue to observe, we can also see the flow of clouds. These are data that the general public can understand and even do some analysis on, so it is a function that must be implemented and is relatively easy to implement.
Enhancing Satellite Vision with Infrared and Night Vision
However, visible light alone is not enough. At night, one side of the earth is plunged into darkness, and the clouds cannot be seen clearly with the naked eye. Therefore, to continuously monitor the weather 24 hours a day, we must also increase the night vision function. As we said before, all objects emit radiation. If you observe in the infrared or microwave band, you can see the clouds at night clearly.
Spectral Analysis in Weather Satellite Observations
From this point of view, it seems very simple! Then let’s go deeper: Can we believe what the satellite sees? Why can’t the clouds it sees be snow on the ground? How to distinguish it from the volcanic ash emitted by the volcano? Why can’t the bright clouds seen at night be city lights? So, the remote sensing principle mentioned above is used here. Scientific instruments use spectral analysis to reveal objects’ color, temperature, and composition.
Complex Data Interpretation and Forecasting
Of course, in reality, whether visible or infrared, what satellites observe are complex superimposed signals. Daytime clouds are formed when sunlight reflects off the clouds, as well as from the radiation emitted by the clouds and the background radiation from the earth and the atmosphere. Professionals must design special algorithms to separate these three signals individually to obtain accurate information. Satellites can provide detailed information about clouds and the atmosphere, including temperature, humidity, altitude distribution, composition, and lightning and thunderstorms. After the various data observed by the weather satellites are sent back to the ground, supercomputers take over and use numerical models to make forecasts. Typhoon Kanu’s weird dance steps result from being rubbed between three high-pressure anticyclones. In the end, the path of Kanu was consistent with the forecast, which is the result of the cooperation between the precise observation of the meteorological satellite and the super-computing numerical model.
Expanding Satellite Applications
Are weather satellites only used to forecast the weather? The basic principle of weather satellites determines that we can also widen our horizons and use weather satellites to study many interesting things. For example, we can monitor agriculture through weather satellites. Soil temperature and water content can affect the spectrum. The reflection spectrum of vegetation can reflect chlorophyll, cell structure, and water content at different wavelengths. Different crops have their own reflection spectra. Through satellite remote sensing, it is possible to judge soil conditions, crop types, crop growth, and whether there are diseases and insect pests. Our “Fengyun” meteorological satellites have the function of agricultural monitoring. In addition to looking at the clouds to understand the weather, they are also the guardian stars of agriculture.
Studying Atmospheric Carbon with Satellites
We can also use weather satellites to monitor atmospheric carbon levels. As ground radiation travels through the atmosphere to the satellite, some wavelengths are absorbed by carbon dioxide. Analyzing the absorption spectrum helps us understand the atmospheric carbon content globally. This provides a scientific basis for energy conservation, emission reduction, and setting carbon emission targets. The carbon satellite “Jumang” launched by China in 2022 is for this business.
Beyond Earth: Cosmic Satellite Applications
Spectral analysis is not limited to meteorological satellites. It can also be used to study the universe, observe other planets, and study their weather. A spacecraft with this function can be regarded as a “cosmic satellite” to some extent. Weather satellite.” For example, the Webb Space Telescope took this picture of Neptune. Triton on the upper left appears to completely overwhelm Neptune’s brightness and would almost be mistaken for a star. The Webb telescope uses infrared light to observe. Triton’s surface has much water ice, reflecting sunlight (including infrared rays) well. However, the methane in Neptune’s atmosphere absorbs infrared rays, so overall, it appears dark. Bright streaks and spots on Neptune’s surface are highly reflective regions of methane and water ice, and their distribution outlines Neptune’s stormy winds.
Utilizing Weather Satellites for Data Gathering
Meteorological satellites use remote sensing technology to gather different kinds of weather data. These satellites can not only predict the weather but also offer additional assistance. When you see weather warnings, preparing for disaster prevention and mitigation is important.