Stratus clouds

Stratus clouds

This data is reviewed by the project of data compilation and application of Science Encyclopedia of science popularization in China.

High level cloud belongs to the cloud family. The cloud base is in uniform curtain shape, often with stripe structure and wisp structure, and occasionally in suspended ball shape. It is widely distributed and often covers all the sky, and its color is gray or gray blue. When the cloud layer is thin, the contour of the sun and the moon is blurred. If there is a layer of ground glass, it is a transparent high-level cloud; when the cloud layer is thick, it is a light shielded high-level cloud because the position of the sun and the moon can not be seen at all. The high-level clouds are mostly frontal clouds, which can reduce a small amount of rain and snow.

basic feature

The high-level clouds are evenly layered, and the appearance is either plain, or fibrous, or grayish white or gray. The cloud layer is relatively thick, mostly between 1500 and 3500 meters. The stripe structure often appears at the bottom of the cloud, which generally extends to cover nearly tens of thousands of square kilometers of the sky, and is often composed of small water droplets and ice crystals.

Some parts of high-level clouds are thin, which can reveal the sun or moon. Through it, the sun or moon looks like a layer of frosted glass. When the cloud layer is very thin, high-level clouds can form white or colored "crowns" or "blooms" around the sun or moon. When the cloud layer is thick, the position of day and month can not be observed.

Formation process

High level clouds are mostly composed of water droplets, supercooled water droplets, ice crystals and snow crystals (columnar, hexagonal, flake, etc.) with a diameter of 5-20 microns.

It is generally believed that the high-level cloud is a wide range of Stratiform Cloud curtain formed by the warm and humid air with stable stratification sliding slowly along the front or rising slowly due to the convergence of tropospheric airflow and adiabatic cooling.

High level clouds are usually formed by cirrus cloud thickening or rain cloud thinning, and sometimes by obscured altocumulus. The appearance of high-level clouds indicates that there is rising air in the area. In the colder months, the appearance of high-level clouds indicates the arrival of moving cyclones and the formation of long-term fixed rainfall or snowfall. In summer, high-level clouds are associated with storms or tropical cyclones.

Distribution area

In the middle and high latitudes of China, high-level clouds often cover the whole day and last for a long time. However, in the tropical and subtropical regions, the typical frontal cyclones are rare, and the turbulence motion of the air is relatively strong under the stable stratification, so the generated high-level clouds tend to evolve (or partially evolve) into massive or wavy cumulus clouds soon.

Main categories

There are two types of high-level clouds: transparent high-level clouds and opaque high-level clouds.

Transparent stratus

The cloud layer is thin and uniform, but the top of the cloud layer is uneven. The clouds are gray. Through the clouds can be observed more fuzzy day, month contour, as if separated by a layer of ground glass. No shadow, no halo.

Dark stratus

The cloud layer is thick, and the thickness changes greatly. The thick part can't see the sun and the moon through the clouds; the thin part is brighter and can also see the fiber structure. It is gray and sometimes bluish. Occasional continuous or intermittent precipitation.

Similarities and differences between high level clouds and cirrus clouds

The same point: the cloud is evenly layered.

The differences are as follows: the high-level clouds are gray or gray, the cloud base often has stripe structure, which often covers the whole day; the cirrus clouds are transparent or milky white, through the clouds, the sun and moon outline is clear, the ground objects have shadows, and there is often halo phenomenon.

Similarities and differences between high level clouds and stratospheric clouds

The same point: the cloud body is evenly layered, often covering the whole day.

The differences are as follows: the high-level clouds are gray white or gray, and the cloud bottom often has stripe structure; the rain layer clouds are low, diffuse and amorphous, which can completely cover the sun and the moon, and are dark gray, and the cloud bottom often has broken rain clouds.

Related examples

On December 30, 2014, citizens of Kunming photographed the beautiful morning glow from different angles. Local meteorological experts said that "a large number of high-level clouds appeared in Kunming this morning. From the perspective of meteorological conditions, it means that there is a weak static front near Kunming. At this time, Kunming is in front of the front. The appearance of the morning glow is just the beautiful scenery formed by the clouds coming from the bay of Bengal in the West and the cold air surging in the East."

At about 9:00 on November 1, 2013, "three suns" appeared in the sky of Chifeng City, Inner Mongolia Autonomous Region, lasting for about 1 hour. Han Jingwei, chief forecaster of Inner Mongolia Meteorological Station, said that this is actually a kind of atmospheric optical phenomenon. When sunlight is refracted by water vapor or ice crystals in high-level cloud system, under certain conditions, halos of light can be formed around the sun, and small light spots will be formed in areas with strong refraction of water vapor or ice crystals

Chinese PinYin : Gao Ceng Yun