Knowing the Weather out of Clouds

Clouds are water droplets， cold water droplets， ice crystals， or a mixture of visible polymers in the atmosphere. Clouds not only vary in shape， but also in color， making the dull sky colorful. But you know what， they are more than a simple decoration， but also weather forecasters. Now， lets have a look at some common clouds with indicative significance！

Altocumulus Cloud

Characteristics

Height is high， appearing in 2500 ～ 4500 meters of altitude. Cloud block is small and the outline is clear， differing in thickness， and shape. Thin cloud block is white， clear to see contours of the sun and the moon； thick cloud block is dark gray， sun and moon contours unclear.

Cumulonimbus Cloud

Characteristics

Thick and bloated as a towering mountain and the cloud bottom height is low， generally in the 400 ～ 1000 meters， contour with fuzzy fibrous structure， the bottom being very dark， often with rain streamers and broken rain clouds. In Supplement to the History of Tang Dynasty written by LI Zhao of Tang Dynasty， there is a saying， "Before the storm， there are clouds like gun carriages"， which refers to this kind of cloud， whose bottom is flat， while uplift at the top， peaks contend， gradually extending to the top， similar to a gun carriage.

Indication—— sunny days

Its body is not thick and is relatively stable with very few changes， indicating sunny days. Agricultural proverb "Carp spots in the sky， no need to twist the seeds being dried" means that the emergence of such a cloud indicates sunny days in the future. However， if the clouds continue to thicken， and gradually integrate into layers， then the weather might change and even rainy days.

Indication——heavy rains

The formation of cumulonimbus requires three conditions： a large number of unstable energy， adequate water vapor and strong convection. Because of these conditions， then when there are cumulonimbus， a storm is unavoidable.

Extended Reading：Any shortcomings of “Cloud-forecast”？

1. Difficult to master.

2. The forecast timeliness is not strong.

3. Forecasts can not be quantified.

Knowledge Link： Why clouds reveal the “secret of the sky”？

Only in the specific conditions of water vapor and atmospheric movement conditions， the cloud can produce， evolute， transform and dissipate. We can neither see the water vapor or the atmospheric movement， but from the apprearance and disappearance of the clouds， we can glimpse the mysteries of water vapor and atmospheric movement， which play important roles in weather phenomena including rain， snow， ice， hail， etc. Over the centuries， the working people in our country have summed up the experience of "knowing the weather out of the cloud" according to the change of the cloud in the production practice. Therefore， the "cloud-forecast” is a forecast based on empirical summary.

Cirrus Uncinus Cloud

Characteristics

A kind of cirruses， often in the 7000 to 8000 meters of altitude， is a silk-like high clouds. Clouds thin and transparent， white， the top with a small hook or a small cluster of white cloud silk wires， which are often arranged in parallel with a long tail， much like a comma.

Nimbostratus Cloud

Characteristics

Commonly below the height of 2000 meters， belonging to low clouds， thick and uniform， dark gray， covering the day， completely obscuring the sun and the moon. Clouds at the end is a mess with no fixed shape. Mostly in the warm front cloud system， the lower part of the water droplets is composed by the small droplets， the middle by small water droplets and ice crystals while the upper part is the ice crystal area.

Cirrocumulus Clouds

Characteristics

Formed by ice particles， appear in 5500 ～ 8000 meters high， looking like a white transparent cloud curtain. Sometimes the organization of the cloud is too thin to be visible， only the sky was milky white； sometimes silk structure is faintly discernible， as if messing silk. Through the clouds， the outlines of the sun and moon are clear， often with halo （a beautiful colorful aperture， the inner layer is red， the outer layer is purple）. It is the only cloud that produces halos around the sun and the moon.

Indication—— bad weathers

The appearance of cirrus uncinus clouds indicates that a warm front or low pressure is coming， and the new weather system will effect the local. When the old and new weather systems changes， wind and rain are common weather phenomena. Therefore， it indicates that the weather is turning bad. Folk proverb "The sky with cirrus uncinus cloud， rain on the ground"， has a certain scientific basis.

Indication—— continuous raining

Compared with the cumulonimbus， nimbostratus cloud is more moderate， will not bring hail or tornado or other disasters. They often appear in the warm front cloud system， formed by the cooling process of entire layer of moist air system from sliding rising. It often causes a long period of continuous rainfall. Farming proverb， "gray cloth in the sky， silk rain comes"， refers to the precipitation situation caused by this type of clouds.

Indication--- heavy storm and rain

Cirrocumulus cloud is caused by rising movement of a large area of high altitude and humid air， whose formation condition is closely related with precipitation. In summer， it represents the arrival of storms and tropical cyclones. The emergence of halo around the sun or the moon is a sign of heavy storm and rain， so people have the saying， "Halo around the sun， rain in the midnight； halo around the moon， wind in the noon".