Satellite cloud maps help you understand the sky through clouds. What do various weather phenomena look like on satellite cloud maps?

Clouds are like a "signboard" for the weather. There is an old saying that one can tell the weather by looking at the clouds! But it is already 2024! Meteorological experts have already prepared satellite cloud maps to help you decipher the weather! Let's take a look!

| What is satellite cloud imagery?

Satellites are like cameras hanging high in the sky. "Satellite cloud images" are photos taken by meteorological satellites from top to bottom of the area you are interested in. In the photos, you can see the clouds covering the earth and the surface features. Finally, the photos are sent to the receiving device on the ground, which will interpret and process the photos to get the image we want! Compared with the traditional meaning of "looking at the clouds to know the weather", satellite cloud images will show you more aspects of the weather because they "stand" higher and farther.

| Do all satellite cloud images look the same?

Do all satellite cloud images look the same? Of course not! Satellite cloud images are divided into three categories according to the differences in the receiving bands of satellite sensors. There are three commonly used categories: visible light cloud images, water vapor cloud images, and infrared cloud images . They all have their own appearances!

Visible light cloud images are made by using the principle of sunlight reflected from the cloud tops, so they can only be taken during the day. The resulting cloud images are similar to the color photos we take with our phones and cameras. Therefore, from the images of visible light cloud images, we can easily distinguish that white is clouds, dark blue is the ocean, green and gray-brown are land... The scene we see is very intuitive, so it is the most widely used.

The water vapor cloud map is an image that is generated by satellites receiving radiation emitted by water vapor in the atmosphere and displayed in black and white tones. The more water vapor there is in the atmosphere, the less radiation is emitted, and the whiter the tone on the water vapor map is, and vice versa. It is like a "black and white photo" that reflects the amount of water vapor in the clouds.

Similar to the water vapor cloud map, the infrared cloud map is an image of infrared radiation emitted by the surface and clouds measured by satellites, and is also displayed in black and white. Here, the radiation received by the satellite is only related to the temperature. The lower the temperature, the less radiation, and the whiter the tone in the cloud map. Conversely, the image in the high temperature area is darker. It is also a "black and white photo", but it reflects the temperature characteristics of the surface and cloud tops. Since infrared remote sensing can sense and feedback cloud imagery day and night and to ground stations, it supplements a large amount of information that visible light cloud maps cannot obtain at night.

After seeing so many satellite cloud images, some friends may wonder how to distinguish the many weather phenomena in nature on satellite cloud images? What should we do if we still can't understand satellite cloud images?

Taking typhoons as an example, satellite cloud images are the most common means of monitoring typhoons. According to the real-time satellite monitoring images, the entire process of typhoon formation and development can be clearly monitored, and the current structural state of the typhoon can also be observed. For example, at 10:15 on August 10, 2023, Typhoon No. 6 "Kano" landed in South Korea. By comparing the visible light cloud map and water vapor cloud map above Jilin Province, it was found that: on the visible light cloud map, although the western part of Jilin Province is also covered by clouds (mixed clouds), the color of this area is darker on the water vapor cloud map, the water vapor content is low, and the precipitation trend is weak. The outer cloud belt of the typhoon above the eastern region shows a large white area on the water vapor cloud map, indicating that the water vapor content is very abundant, so large-scale rainfall weather is prone to occur in the eastern part of Jilin Province.

In addition to comparing and analyzing a variety of satellite cloud images, meteorological experts also need to combine real-time information, forecast models and accumulated experience to comprehensively judge weather conditions. In order to make satellite cloud images more intuitive, experts will also perform secondary processing on satellite cloud images and obtain quantitative extraction products through model algorithms, so that even if you can't read satellite cloud images, you can also become an expert in "cloud" recognition!

Editor | Wu Yujie Liu Min Proofreader | Tang Xiaoling Author's Unit | Jilin Meteorological Science Institute