The Science of Cloud Seeding - PowerPoint PPT Presentation

1 / 35
About This Presentation
Title:

The Science of Cloud Seeding

Description:

The Science of Cloud Seeding Students Seminar Series 13th October 2003.by, Vinoj V PhD Student CAOS, IISc Background By the year 2025 two thirds of the world ... – PowerPoint PPT presentation

Number of Views:3258
Avg rating:3.0/5.0
Slides: 36
Provided by: caosIisc
Category:

less

Transcript and Presenter's Notes

Title: The Science of Cloud Seeding


1
The Science of Cloud Seeding
Students Seminar Series 13th October
2003 .by, Vinoj V PhD Student CAOS, IISc
2
Background
  • By the year 2025 two thirds of the world
    population will live under severe water stress
    conditions as determined by studies of the World
    Meteorological Organization (WMO)
  • The rapid growth of Agricultural and Industrial
    sector along with the population explosion makes
    India particularly vulnerable.
  • Though India get high amount of rainfall compared
    to many other countries, the large
    infrastructure and water intensive agricultural
    practice makes India vulnerable to even to the
    minor swings (lt 5) in rainfall
  • Water related problems within the states
  • India is at its absolute water limits (Bryson.,
    1989)

3
Mitigation
  • Intelligent Utilization of the available Water
    Resources
  • Rainwater Harvesting
  • New source of water?
  • Artificial Rain Making! - Cloud Seeding?
  • Remember Atmospheric Vapor is only 0.001 of the
    total water in the hydrosphere

4
American Indians
  • The rain dance was a big part of American Indian
    culture and helped them carry on with their day
    to day activities.
  • They believe by pleasing the rain god he would
    provide rain for their crops.

5
American Indians
  • Each tribe had a different god or ceremony for
    their rain needs.
  • The tribes were similar in the fact that each one
    of them relied on rhythmic dancing in their
    events. (http//users.rowan.edu/)

6
  • According to Rig Veda - The earliest accepted
    Gods were
  • DYAUSH PITA (the sky father)
  • PRITHVI MATHA (the earth mother)
  • VAYU (the wind God)
  • PARJANYA (the rain God)
  • SURYA (the sun God)
  • VARUNA (the God of oceans)
  • AGNI (the fire God)
  • INDRA (the war God)

7
(No Transcript)
8
The Cloud Formation
  • Homogeneous nucleation of Water droplets require
    high Degree of super saturation (350-400)
  • Heterogeneous nucleation in the presence of Cloud
    Condensation Nuclei (CCN)
  • Two important processes on how rain is produced
  • Collision-Coalescence Process
  • Ice-crystal (or Bergeron) process

9
Droplet Growth
Typical Cold Clouds
Warm Clouds - Collision and
Coalescence Cold Clouds - Ice Crystal
Process
Typical warm Clouds
10
Seeding Definition
  • The deliberate treatment of certain clouds or
    cloud systems with the intent of affecting the
    precipitation process(es) within those clouds.
  • Borrowed from Physical Chemists,
  • A method used to precipitate solute from the
    solvent - Pieces of solid material placed in a
    supersaturated solution to promote precipitation
    of the dissolved solute

11
The Beginning
  • Cloud seeding began by dropping dust particles in
    to the cloud to help the water condense.
  • The dust was ejected from crop dusting planes
    which were already outfitted for the job.
  • There are now more scientific ways to cloud seed.

12
The Beginning
13
Cloud Seeding
  • Cloud seeding is actually a very complex process.
    In the simplest terms, it introduces other
    particles (CCNs) into a cloud to serve as cloud
    condensation nuclei and aid in the formation of
    precipitation.
  • There are three types of cloud seeding static
    mode, dynamic mode, and hygroscopic seeding.
  • Static mode cloud seeding seeks to increase
    rainfall by adding ice crystals (usually in the
    form of silver iodide or dry ice) to cold clouds.
  • Dynamic mode cloud seeding increases rainfall by
    enhancing "vertical air currents in clouds and
    thereby vertically process more water through the
    clouds." Basically, in this method of seeding, a
    much larger number of ice crystals are added to
    the cloud than in the static mode.
  • In hygroscopic seeding, salt crystals are
    released into a cloud. These particles grow until
    they are large enough to cause precipitation to
    form. Clouds can be seeded from above with the
    help of airplanes that drop pyrotechnics, or from
    the ground by using artillery or ground-to-air
    rockets

14
The Seeding Concepts
Static Seeding Alter the microphysical
Properties of clouds
Dynamic Seeding Attempt to modify the Air
motion within the clouds
Hygroscopic Seeding Use of hygroscopic material
to Obtain the intended result (eg salt) Static
or Dynamic
15
(No Transcript)
16
  • Warm Cloud Seeding
  • Formation of Rain through Hygroscopic Seeding
  • Hygroscopic Particles
  • Extremely moisture absorbent
  • Grow in low humidity air below cloud base
  • Examples of Hygroscopic Material
  • Common Table Salt
  • Ammonium Nitrate Urea Fertilizer
  • Objective of Hygroscopic Seeding
  • Introduce large drops into cloud
  • Large drops collide with small cloud droplets
    and grow into rain drops (Coalescence)
  • Rain drops heavy and large enough to fall out of
    cloud and reach ground.

17
(No Transcript)
18
Mixed Clouds
19
Seeding Materials
  • The materials used in cloud seeding include two
    primary categories, tied to the type of
    precipitation process involved
  • Glaciogenic (ice-forming) Silver iodide, dry ice
    and compressed liquid propane
  • The second major category is focused on cloud
    systems where the warm (coalescence) process
    predominates.
  • Hygroscopic (water attracting) materials such as
    salt, urea and ammonium nitrate can be utilized.
    Of the hygroscopic materials, the most commonly
    used are salts.

20
Silver Iodide
  • Why Silver Iodide ?
  • It has a crystalline structure similar to ice
    crystal, and it acts as an effective ice nucleus
    at temp. of -4C and lower
  • Silver iodide, when burned, creates extra ice
    crystals in winter clouds to increase snow fall.
    (The first AgI generator could discharge 1016
    particles per gram)
  • (www.wmi.cban.com/)
  • It can be distributed from the ground...

21
Silver Iodide
  • or from the air.

22
Automated High-Output Ground Seeding System
Aircraft-mounted flares
Cloud Seeding Aircraft
23
How Cloud Seeding Works
24
How Cloud Seeding works?
  • In cold cloud seeding.,
  • the introduction of an ice-forming nucleating
    agent, (e.g., silver iodide) causes supercooled
    liquid water droplets to freeze. Once these
    droplets freeze, the initial ice embryos grow at
    the expense of the water droplets around them.
  • The first freezing process is often referred to
    as a static seeding effect, increasing the
    efficiency of the precipitation process within
    the seeded cloud volume.
  • The second freezing process, resulting from
    release of additional heat into the cloud, is
    often called the dynamic effect, whereby the
    treated clouds are invigorated, thus processing
    more moisture.

25
Warm Cloud Seeding at 2 to 3 km heights
26
(No Transcript)
27
Cold Cloud Seeding
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
Indian Experiment
  • IITM, Pune was involved in cloud seeding
    experiment for a period of 11 years in the
    seventies
  • Reported Increase in rainfall due to seeding

  • 24
  • Different states have their own operational
    programs whose success is still being debated

33
Interesting Applications
  • Hail suppression
  • Hurricane Modification
  • Eg Operation STORMFURY
  • Fog Dispersion
  • Defence Applications

34
Suppression of Hail
  • Cloud seeding can be used to cause rain instead
    of hail.
  • However suppressing hail in one area often causes
    more in another. (twri.tamu.edu)

35
Thank You
Write a Comment
User Comments (0)
About PowerShow.com