A visible aggregation of minute water droplets or ice particles in the air above the ground levels i.e. at the certain elevation is called as the cloud.
There are two major cloud group based on their forms
1. Strati form Cloud group
These are the clouds present in the form of layers
2. Cumuli form Cloud group
It consist of globular clouds in the form of cotton balls
The world meteorological organization gave the international cloud atlas consisting of 10 main cloud families. These families are listed according to their heights into 3 groups.
1. High Clouds
All high clouds are called as ‘cirro’ clouds and they are present at elevation of 5 to 13 kms.
These clouds are composed of ice crystals and produce phenomenon called ‘halo’ and does not give rainfall/precipitations they are of three types
- These are detached clouds in the form of white delicate filaments or narrow binds.
- Sometimes they are in the form of white patches.
b. Cirro Cumulus
- These are the clouds looks like small flakes or globules consisting of white patchy layers of clouds without shading.
- When these patches are uniformly arranged, it forms a ‘mackerel sky’
c. Cirro status
These are the transparent whitish clouds in the form of a fibrous veil with smooth appearance.
2. Middle Clouds
All middle clouds are called as the alto clouds. They are present in the height ranging from 2 to 7 Kms. They of three types
d. Alto Cumulus
- It’s a white or grey patchy layer of cloud having dark shading on their under surfaces.
- Sometimes they are found in wavy or parallel bonds where they are referred as sheep or wool packed clouds.
- Often they are composed of super cooled liquid droplets. They may or may not give rainfall
e. Alto stratus
- They are grayish or bluish cloud layers having fibrous appearance covering most part of the sky.
- The sun is vaguely revealed in the form of spot.
- But the ground shadows are not cast.
- They give out fine drizzle of snow
f. Nimbo stratus
- It is a grey cloud layer often very dark, thick enough to blot the sun.
- The rain or snow falling from this cloud does not reach the ground and called as virga.
3. Low Clouds
These are the clouds present below 2 kms of elevation and there are 4 types of cloud families are present in this
g. Strato cumulus
- It is a low cloud layer which is dull grey in colour consisting of large lumpy masses with brighter intersects
- This is a grey cloud layer.
- The sun is visible and its outline is clearly distinguishable.
- They are also present in the form of raged patches.
- These are dense detached clouds with sharp outline developing vertically in the forms of mount or tower like cauliflower.
- The sunlit part is brighter and the base is dark.
- They represent transition to the cumulo nimbus clouds and are present only during day time
j. Cumulo nimbus
- These are heavy & dense cloud forms having an anvil head.
- These are towering clouds from the ground level to intermediate heights.
- They are associated with heavy rainfall, thunders, lighting.