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Lec-11. Dew, Fog

The document discusses dew and fog, explaining that dew forms as water droplets on surfaces when temperatures drop to the dew point, while fog is a cloud of water droplets near the ground that reduces visibility. It outlines the formation processes of both phenomena, including the conditions necessary for their occurrence. Additionally, the document classifies different types of fog and highlights its importance in various environments.

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16 views12 pages

Lec-11. Dew, Fog

The document discusses dew and fog, explaining that dew forms as water droplets on surfaces when temperatures drop to the dew point, while fog is a cloud of water droplets near the ground that reduces visibility. It outlines the formation processes of both phenomena, including the conditions necessary for their occurrence. Additionally, the document classifies different types of fog and highlights its importance in various environments.

Uploaded by

sadianipun2020
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Dew and Fogs

Course: 201
Lecture: 09

Md. Naimur Rahman khan


Roll:491
Dew
• Dew is water in the
form of droplets that
appears on thin,
exposed objects in
the morning or
evening. When
temperatures are low
enough, dew takes the
form of ice; this form
is called frost.
Formation

 Water will condense into droplets depending


on the temperature. The temperature at which
droplets can form is called the Dew Point.
When surface temperature drops, eventually
reaching the dew point, atmospheric water
vapor condenses to form small droplets on the
surface.
Fog
 Fog is a condensed form of water vapor. Fog
is nothing but the cloud of small water
droplets near ground level that is dense
enough to reduce horizontal visibility to less
than about 3000 feet (1000m).
In this view, only downtown San
Francisco and Sutro tower are free
from fog
Characteristics
 Fog looks like smoke
 It is very light things.
 It can flying in the atmosphere
 For fog, the snow can not deposit on the
surface.
Formation
 Fog forms as the relative
humidity increases 200%. As
the relative humidity
reaches to its maximum
level the haze particles
grow into fog particles near
the ground. The fog is
nothing but a cloud near
the earth surface. The Fog over San Francisco
visibility of fog is generally Bay
less than 1km.
We can view the life cycle of fog as below:

Water Little wet air Less temp fog


vapour + +

So at the end, we can say that fog can be form-

❑By cooling air to its dew point

❑By adding moisture to the air near the ground


Classification
 The classification of Fog as below:
Fog

Intra air mass Fog Frontal fog

Radiation Advection Upslope Warm Front Cold front

Ground inversion Tropical air fog

High inversion Sea Fog

Steam Fog
Intra Air mass fog
 Sometimes the temperature of the earth
surface decreases very low which result a
special type of fog known as the Intra air
mass fog. This type of fog usually created
by the one way movement direction of air
mass.
Frontal fog

 Extra water
vapour in the
atmosphere
results the
frontal fog.
Importance of fog
✓ Fog is obstructed for land way, aquatic
way, and sky way.
✓ In high latitude, fog absorbed radiation
heat from the atmosphere.
✓ As a result the glacier does not melt
quickly.

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