Clouds

Visible aggregate of suspended water droplets and ice crystals above the Earth’s surface is called

CLOUD

Cloud formation occurs as result of water vapor condensation.

Condensation takes place due to air temperature and amount of water vapor

1

Air temperature decrease is a reason for cloud formation

Reasons for temperature variation

Advection Vertical motion Radiation Eddy mixing

Water phase transfer

	Layers
Surface	Boundary	Free atm.
+	+	+
-	+	+
+	+	-
+	+	-
+	+	+

2

Advection	T			T	v	T
			u
				x
		t adv				y

Vertical motion

Type of vertical motion

Small scale, convective type vertical motion

Large scale, dynamic type vertical motion

Topographic vertical motion Frontal vertical motion

Eddy type vertical motion

Order of magnitude m/s

100 101

10 3 10 2

100 10 1

10 1 10 2

Chaotic, not significant

3

Water vapor content variation

		s		1						s
								K
		t eddy		z						z
	s						s		v	s
			u
							x
		t Adv								y

			s
				s DivV
			t Div
	s 0,622			e	sm 0,622
				P

Eddy mixing

Advection

Divergence

These factors act in case there is a source of water to evaporate.

	dE		L	E
	dT		R
				T 2
			w

			7.63 T
	E 6.11 10		241.9 T
E			7.63
P
	e 6.11 10	241.9

4

Classification of clouds

Classification on visual appearance and structure

Cumuliform(cauliflower) clouds

Undulatiform(billow ) clouds

Stratiform clouds

5

Classification based on altitude of the clouds

Upper level clouds

Cirrostratus

Altocumulus

Middle level clouds

Altostratus

Cirrus

6 km

Cumulonimbus

Cumulus congestus

Cumulus humbles

2 km

Low level clouds

Stratus,

Stratocumulus

Chimney clouds

6

Cirrus felosus

7

Cirrus uncinus

Cirrostratus

Nimbostratus

6 km

As

Ns

2 km

Rain

Nimbostratus is the cloud that can be regarded both middle and low level cloud.

Usually, it appears in combination with altostratus.

10