Weather is the condition of the Earth’s atmosphere at a certain place and time. The elements of weather: Temperature Humidity Precipitation Air Pressure Wind Visibility

1. Presentation
Submitted to: Mam Faiza
Submitted by: Hina Ayub
Roll No: 0058-BSE-ZOO-2017
UON

2. Weather
Modification

3. What is weather?
 Weather is the condition of the Earth’s atmosphere at a certain place and time.
 The elements of weather:
 Temperature
 Humidity
 Precipitation
 Air
 Pressure
 Wind
 Visibility

4. Weather Modification
Weather modification is the intentional effort of man to manipulate or alter the
naturally occurring weather with certain aspects of the environment to produce
desirable changes in weather for the benefit of someone.

5. Known Methods
 The best-known kind of weather modification is cloud seeding, with the
goal of producing rain or snow, suppressing hails (which can ruin crops),
or weakening cyclones and hurricanes.
 Weather control can have the goal of preventing damaging weather, such
as hurricanes or tornadoes, from occurring of causing beneficial weather,
such as rainfall in an area experiencing drought or of provoking
damaging weather against an enemy or rival, as a tactic of military or
economic warfare.
 Weather modification in warfare has been banned by the United Nations.

6. Weather Hazards and crop production
 Food production, which is the predominant feature of Indian agriculture, is not
adequate not only to meet the existing level of consumption, but large quantities of
foodstuff need to be exported.
 The success of agriculture in India depends mainly on the timely onset, proper
amount, and suitable distribution of monsoon rains in the season. Unless these
factors are favorable the crop yield are fatally affected.
 The fluctuations of weather occur abruptly and with a violence which is highly
detrimental to crops.
 Therefore, success or failure of farming is very intimately linked up with prevailing
weather conditions.

7. FROST
• Frost is the solid deposition of water vapor from saturated air in
the form of small white ice crystals on the ground or other
surfaces when the temperature of these solid surfaces falls below
freezing point of water or below the dew point of the adjacent air.
• Frost crystals’ size differ depending on time and water vapour
available.
• Frost is also usually translucent in appearance.

8. Frost

9. Types of Frost
1-Advection Frost:
Results when the temperature at the
surface in an air mass is below the
freezing level.
2-Radiation Frost:
Occurs on clear nights due to radiative
cooling with a temperature inversion
and usually results in formation of ice
crystals on cold objects.

10. Frost Modification
a) Preventing the loss of heat
 Since cause of frost is the radiation loss from ground, crops etc. the fall of temperature
can be minimized by intercepting heat radiated and returning it to ground.
 This can be achieved by covering the crop to be protected. The crop may be covered
by plastic houses or glass houses and the ground covered by the mulches of different
types cutting off the heat loss.
 From this we may keep the temperature 1-2°C above that of freely exposed objects.
 It has long since been known that serious radiation frost does not occur on cloudy
nights.

11.  Therefore, it is possible to prevent the frosts by forming an “artificial
clouds” by burning some form of smoky fuel or by one of the various
available chemical smokes.
 A really dense cloud can maintain a temperature 2-3°C above that in
neighboring areas not covered by the clouds. Since water vapor absorbs
radiation and reradiates it, it may be possible to cut down the loss of heat
by radiation by adding water vapor to the air.

12. b) Stirring the Air:
In radiation frosts there is an inversion of temperature.
The air is coldest near the ground and becomes warmer at higher
levels. If this warm air could be brought down to the ground level
the result would be an appreciable rise of temperature.
This method of frost prevention is applicable on a level plain or
gentle slope but not where the layer of freezing air is much deeper.

13. c) Heating the Air:
 The most effective means of protecting crop against frost is warming the
air.
 Any form of heating can be used, the most practicable forms being
burning oil, coal and paraffin compounds.
 The choice depends partly on the relative cost of the fuel and partly on
the labour available.
 Efficient heaters can maintain a temperature 3-5°C above that of
unprotected areas.

14. Hail
 A hailstorm is a particularly violet thunderstom.
 Though short in duration, but precipitation forms and associated squalls are violent.
 It is one form of precipitation.
 It destroys the agricultural vegetation,the damage being predominantly mechanical.
 Hail storm causes a lot of damage to standing crops. Protection against violent hailstorms is
difficult.
 But farmers who are forewarned, can harvest their crops if they are already ripe, or take other
protective measures.
 The largest hailstorms are about 5 inches in diameter and 1.5 lbs.

15. Hail Suppression
 In many areas of the world hail does enormous destruction to agriculture, particularly fruit
orchards and grain fields.
 There have been cloud-seeding projects aimed at reducing hail damage.
 Some operations have attempted to put so many nuclei into the supercooled parts of
cumulonimbus that they would be almost totally converted to ice crystals.
 Such a procedure, called overseeding, is not considered practical because of the large quantities
of material needed to seed the clouds over an area great enough to have an appreciable effect.
 Most hail-suppression attempts have been based on the concept that damage will be reduced if
the hailstone sizes are reduced.
 This does not require overseeding.

16. Fog
 Fog is a low-lying cloud that forms at or near the surface of the Earth.
 It is made up of tiny water droplets or ice crystals suspended in the air and usually
gets its moisture from a nearby body of water or the wet ground.
 Fog is distinguished from mist or haze only by its density.
 In meteorological forecasts, the term “fog” is used when visibility is less than one
kilometres (one nautical mile in case of marine forecasts).
 If visibility is greater than that, but is still reduced, it is considered mist or haze.

17. Fog

18. Fog Dissipation
 It is of prior importance in Aviation.
 In order for aircraft to take off and land, it is necessary that the ceiling (the height of the
cloud base above the ground) and visibility be above certain minimum values.
 It has been estimated that, in the United States alone, airport shutdowns by fog were costing
the airlines many millions of dollars annually.
 The vital effect of low ceilings and visibilities on military aircraft operation was forcefully
emphasized during World War II when Allied aircraft flew out of foggy England.
 During the late 1930s attempts were made to dissipate fogs by seeding them with salt
particles, in particular calcium chloride. Some success was experienced, but this technique
did not appear to be practical.

19. Storm
 A storm is any disturbed state of an environment or astronomical body’s
atmosphere especially affecting its surface, and strongly implying severe
weather.
 It may be marked by significant disruptions to normal conditions such as strong
wind, hail, thunder and lightning (a thunderstorm), heavy precipitation
(snowstorm, rainstorm), heavy freezing rain (ice storm), strong winds (tropical
cyclone, windstorm), or wind transporting some substance through the
atmosphere as in a dust storm, blizzard, sandstorm, etc.
 Storms have the potential to harm lives and property via storm surge, heavy rain
or snow causing flooding or road impassibility, lightning, wildfires, and vertical
wind shear.

20. Storm

21. Storm Modification
 Storms such as tropical cyclones and “hurricanes” need the warm water of the
tropics, which feed the storms with energy.
 In a mature hurricane, the wind picks up warmth and moisture from the ocean,
circling inward ever faster from outer cloud bands to the inner eye wall, where the
winds are the strongest and where it finally rises rapidly and is pushed out the top.
 In the beginning, a disturbance forms in the atmosphere, developing into an area
of low atmospheric pressure.
 Winds begin to move into the center of the storm seedling from surrounding areas
of higher air pressure.