Chapters :
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Temperature

In general the temperature of air at any place is influenced by
  1. The Latitude Of The Place
  2.  The Altitude Of The Place
  3.  Distance From The Sea, The Airmass Circulation
  4. The Presence Of Warm And Cold Ocean Currents
  5. Local Aspects.


INVERSION OF TEMPERATURE

The condition at which the temperature increases with altitude is called as ‘Inversion Of Temperature’. In this condition, warm air lies over cold air.

THE CONDITIONS FOR INVERSION OF TEMPERATURE ARE:

LONG WINTER NIGHTS: The bottom layer of the atmosphere in contact with the ground is cooled and the upper layer remains relatively warm. CLOUDLESS SKY: The higher amount of terrestrial radiation reaches the higher altitude which leads to lower temperature at low level due to clear sky. DRY AIR NEAR THE SURFACE: The dry air absorbs less terrestrial radiation and allows them to escape into space.  SNOW COVERED GROUND: During night, due to terrestrial radiation and higher albedo, most of the heat is lost to the atmosphere and the surface is cooled.  FORMATION OF FRONTS: The movement of warm air over the cold air during the formation of the various fronts leads to inversion condition. 

MOUNTAIN WIND:

The subsidence of cold mountain wind at the early morning leads to the displacement of warm air from the valley to higher altitude. This type of inversion is called as ‘valley inversion’

EFFECTS

Inversions play an important role in Determining Cloud Forms, Precipitation, And Visibility.. In regions where a pronounced low-level inversion is present, convective clouds cannot grow high enough to produce showers. Visibility may be greatly reduced below the inversion due to the accumulation of dust and smoke particles. Because air near the base of an inversion tends to be cool, fog is frequently present there. Inversions also affect diurnal variations in temperature. Diurnal variations tend to be very small.

TYPES OF TEMPERATURE INVERSION VALLEY BREEZE

Due to the intense insolation during the daytime, the slopes of the mountain heat up rapidly but the free atmosphere above the lowlands is not heated to some extent. As the valleys receive comparatively lesser insolation so relatively high pressure sets up in the valleys while along the mountain slopes due to more heating the warm air is uplifted, and low pressure sets up.  Thus, the air moves from the Valleys towards the slopes (High pressure to the low pressure) and this upslope movement of Air Is Known As Valley Breeze. Valley breezes are also known as ANABATIC WIND. Weather associated with the Valley Breeze because heavy Orographic rainfall causes occasional and afternoon thundershowers on warm and humid days.

MOUNTAIN BREEZE

On mountain-sides under the Clear Night Sky, the Higher Land (Upslope Land) Radiates Heat and is cooled and in turn cools the air in contact with it. The cool denser air flows down the mountain slope due to the pressure difference since the valley is warmer and at relatively lower pressure. This flow of the air is termed as Mountain Breeze and they are also known as KATABATIC WIND.

WEATHER ASSOCIATED WITH THE MOUNTAIN BREEZE

By the morning the mountain breeze produces temperature inversions and valley bottom becomes colder than the Mountain Slopes. Thus, the valley floors are characterised by frost during the night while upper part/ hill-side are free from frost in cold areas.

FREQUENCY

Mountain Breeze is more common in cold season while valley breeze has a greater preference for Summer Season, in summer. URBAN HEAT ISLAND (UHI) An Urban Heat island is an Urban Area Or Metropolitan Area that is significantly warmer than its surrounding rural area due to high concentration of high rise concrete buildings, metal roads, sparse vegetation cover and less exposure of soil. These factors cause urban regions to become warmer than their rural surroundings, forming an “island” of higher temperatures .

WAYS TO REDUCE THE IMPACT OF URBAN HEAT ISLAND:

  1. Increase Shade Around Your Home: Planting Trees And Other Vegetation, Provides Shade And Cooling Effect Through Evapotranspiration And It Lowers The Surface And Air Temperature.
  2. Install Green And Cool Roofs.
  3. Use Energy-Efficient Appliances And Equipments.
  4. Shift All Industries Away From The Urban Area.
  5. Reduce Emission From Automobiles.
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