Dark cloud weather in Shenzhen

In physical essence, clouds are small water droplets and small ice crystal clusters floating in the air. The cloud shape seen by the naked eye is the outline of small water droplets or small ice crystal clusters (Zhang Jihuai's Formation of Clouds). ? As we all know, water and ice are colorless, and the water droplets and ice crystals that make up clouds are actually colorless and transparent. However, these water droplets and ice crystals also reflect, refract and absorb sunlight. Sunlight acts on the cloud, and then enters our field of vision through reflection, refraction, transmission and other different ways, which makes us feel the shape and color of the cloud.

In meteorology, clouds are divided into 29 categories according to their shape characteristics, structural characteristics and cloud base height (Tan Haitao et al., ground meteorological observation). When describing the color characteristics of these 29 kinds of clouds, words such as transparency, white, grayish white, gray, dark gray, dark color and so on will be used, and these colors are often closely related to the thickness of clouds. Here are some quotes for reference: "Cirrus clouds: clouds are usually white without shadows ... but when the clouds are particularly thick, there may be shadows in the middle ..."; "Cumulus clouds: ... thin clouds are white and thick clouds are dark gray ..."; "nimbostratus: The thick and uniform precipitation cloud that can completely cover the sun and the moon is dark gray" and so on. It seems that the landlord must accept the view that "white clouds are thin and dark clouds are thick".

However, "thick clouds and thin white clouds" cannot fully explain the relationship between "black" and "thick" and "white" and "thin", because the landlord, like most people, sees "thick white clouds and faint dark clouds" in the sky. Let's explain it with a picture. The big cloud in the middle of the picture is a newly developed cumulus cloud. A is white and bright, and B is dark gray. This is because A directly reflects sunlight into our eyes, and thick clouds cover our eyes, showing us that B is dark gray. No one will stand up and not tell me that the water drops at point B are bigger than those at point A, right? The cloud at C didn't receive direct sunlight, and we also saw dark gray. D is a smaller cumulus, and its backlight is also dark. E and f are cirrus clouds. Because it is thin, it is mainly white, and F is thick, so it looks silver-gray.

Below is a picture taken from the top of the cloud. All sunny places are white, bright and dark.

To sum up, whether a cloud is a white cloud or a dark cloud is not determined by the size or thickness of water droplets in the cloud, but by the lighting conditions of the cloud environment. Some simple explanations, if you have different opinions, welcome to discuss. I like to discuss problems with people who have a certain theoretical basis.