Tools used in weather forecasting

1. Tools Used In Weather
Forecasting
Harithalekshmi V.
2018-11-067

2. Basic Inputs For Weather Forecasting
• Area coverage under the network of meteorological
station
• Collection of meteorological data on cloud cover,
sunshine, radiation, rainfall, temperature, wind and
pressure
• Upper air data on wind, humidity and temperature
from various heights

3. Pilot Balloons
• Small balloon filled with Hydrogen or Helium.
• Measure wind direction and speed at different heights in the
atmosphere by using a theodolite
• Measures temperature, humidity and pressure at different heights
using meteorographs
• Balloons meant to stay at a constant altitude for long periods of time
are known as transosondes

4. • One of the first people to use weather balloons was L. T. de Bort, a
French meteorologist.
• Starting in 1896 he launched hundreds of weather balloons from his
observatory in Trappes, France.
• These experiments led to his discovery of the tropopause and
stratosphere

5. Launch time, location
• The ascent rate can be controlled by the amount of gas with which
the balloon is filled.
• About 800 locations around the globe do routine releases, twice daily,
usually at 0000 UTC and 1200 UTC.

6. Operation
 Balloon filled with either helium or hydrogen lifts the device up
through the atmosphere.
 The maximum altitude to which the balloon ascends is determined
by the diameter and thickness of the balloon.
 As the balloon ascends through the atmosphere, the pressure
decreases, causing the balloon to expand.
 Eventually, the balloon will expand to the extent that its skin will
break, terminating the ascent.
 After bursting, a small parachute on the instruments carries them to
Earth.

7. Theodolite
• Optical telescope – measures wind direction and speed at different
heights in the atmosphere
• Measures horizontal and vertical angles of ascending balloons at
known intervals of time.
• In an obscured sky balloon is lost and can not trace.
• This can be overcome by radio – theodolite, where radio signals are
used to track the balloons

8. Modern electronic theodolites
• Readout of the horizontal and vertical circles is usually done with a
rotary encoder
• This produce signals indicating the altitude and azimuth of the
telescope which are fed to a microprocessor

9. Meteorographs
• Combinations of barographs, thermographs and hygrograph.
• Once the balloon burst at greater heights, the meteorograph fall in
unknown locations
• Utility is very much limited

10. Radiosonde
• Transmit weather observations to the ground receiver by radio signals
• It is carried by means of a balloon
• Measeres
Temperature - +40°C to - 90°C
Relative humidity - 15 – 100%
Baraometric pressure – 1040 – 40 hPa
Data is immediately available and useful in weather forecasting
IMD has 39 radiosonde and 62 pilot balloon observatories spread all over the
country
Radiosondes measuring ozone concentration are known as ozonesondes

12. Radio Detection And Ranging (RADAR)
• The active technique of remote sensing is used
• Transmit electromagnetic pulses of given characteristics and also
receives them back
• Modification of transmitted pulses can be interpreted in terms of the
characteristics of the reflected surface

13. Doppler weather radar
• It is capable of measuring the approach (or departing) speed of
raindrops.
• Works based on Doppler effect
• Detects rain in the atmosphere by emitting pulses of microwave and
measuring the reflected signals from the raindrops.

14.  The faster the raindrops move
towards the radar, the higher will
be the frequency of the
microwave reflected from
raindrops
 The more intense the reflected
signals, the higher will be the rain
intensity.
 The distance of the rain is
determined from the time it takes
for the microwave to travel to and
from the rain.

15. Weather Radar Network Of India Meteorological Department
• Radar used in IMD for detecting
Thunder storms
Hail storm
Tracking of Cyclone
Rainfall Estimation
• IMD has replaced conventional radar systems with Doppler Weather
Radar(DWR)
• First DWR was installed at Sriharikota in 2004
• Existing DWRs are networked to provide data for numerical weather
prediction model for nowcasting

16. Sonic Detection And Ranging (SODAR)
• Used as wind profiler - Measure wind speed at various heights above
the ground.
• Calculate the wind speed by measuring the scattering of sound waves
by atmospheric turbulence

17. Satellite
• For viewing large weather systems on a
world wide scale
• Geostationary Satellites are being used
for weather forecasting
• They are orbiting at a height of 3600 KM
• Orbital period is synchronous to that of
earth.
• Geostationary satellites appear to be
fixed over one spot

18. • The first weather satellite, Vanguard 2
• launched on February 17, 1959.
• Designed to measure cloud cover
• First weather satellite considered to
be successful is TIROS I
• Launched by NASA on April 1, 1960

19. Indian National Satellite System
• Series of multipurpose geo-stationary satellites launched by ISRO to
satisfy the telecommunications, broadcasting, meteorology, and
search and rescue operations
• Gives information on cloud spread and temperature
• Used in Short and medium range weather forecasting
• INSAT 1B – 1983 –First in the series
VHRR (Very High resolution Radiometer) – Measures Radiation in 2
narrow spectral windows.

20. • Insat 2E – Resolution of VHRR was increased – Added water vapour
channel
• 1996 – Satellite Image was opened for public through IMD website.
• INSAT-3A - Data Relay Transponder (DRT) to receive data from
automatic weather stations of different institutions from all over the
India
• INSAT-3D - Launched in July 2013
• INSAT-3DR - Weather satellite meant to provide meteorological
services to India.
Launched on 9 September 2016

21. KALPANA-1
• Exclusive meteorological satellite launched in 12th September 2002
• It was located at 74 degree East longitude
• Originally known as MetSat-1
• On February 5, 2003 it was renamed to Kalpana-1
• Its mission is to collect data in layer of clouds, water vapor, and
temperature of the atmosphere
• Kalpana-1 went out of service in mid 2018

22. Working Principle
• There are two types of sensors
• Visible light sensor – Imager – Works like a camera – Gather information
Used only during daylight hours
Images are created based on the reflected light
Infrared sensor – Sounder- Measures temperature
The higher the temperature of the object the more energy it emits
Sensors measures the amount of energy radiates from earth
It can be used in night
In addition to providing visual images, satellites can also provide data that allow
calculation of atmospheric temperature,moisture profiles etc.

23. • At present only 2 meteorological satellites are under operation
• They are INSAT 3D and INSAT 3DR
• For Every 15 minutes a new set of images are available for forecasters
• Temperature and humidity profile are available in every 3 hour
• The earth stations in Hassan and Bhopal receive data from INSAT
• The satellite data is processed and out puts are generated.
• The out puts like OLR(Out going long wave Radiation ), Wind speed
over sea can be used in the prediction of onset of monsoon.

24. Detect genesis, growth, intensity and location of tropical
cyclone
Cyclone Phailin the
strongest tropical cyclone
ever recorded in
india,2013

27. Thank You.