Methods for measurements of meteorological variables

1. AIR POULLTIONANDQUAILTYCONTROL
Methods for Measurements of Meteorological Variables
and
Influence of Meteorological phenomena on Air Quality –
Wind rose diagrams
Presented by: C G MOHAN
Asst Professor
GPCET

2.  A Meteorological instruments must possess an
acceptable degree of accuracy and sensitivity
 In our country the NEERI (National
Environmental Engineering Research Institute)
has developed some devices for measuring the
meteorological Variables.
 Wind Direction Recorder
 Wind Direction Aloft
 Wind Speed Recorder
 Humidity Measurements
 Temperature Measurements
 Solar Radiation Measurements

3.  The Patented instrument of the NEERI for
measuring wind direction is a simple one
 In which employs the conventional Wind Vane
to sense direction .
 It is automatically and operated mechanically
without any power supply
 The instrument continuously records on a
attached chart the direction of the wind with
time

5. Surface Wind Direction
There are four main types of wind vane for
measuring direction they are :
 Flat Plate Vane
 Splayed Vane
 Aerofoil Vane
 Running average anemograph

6.  Flate Plate Vane Splayed Vane

7. Aerofoil Vane Anemograph

9. The Wind direction aloft is at the height of a plume
from one or more stacks is important in some
investigations
All available following methods discussed involve
consideration time and effort
 Pilot balloons
 Tetroons
 Kite balloons
 Radio and Rader
 Smoke Trails

10.  Pilot balloons(Pibals) Tetroons

11. Kite Balloons Radio and radar

12. Smoke Trails

14.  Instrument for measuring wind speed are
called anemometers
 The most common type is the cup anemometer
 The NEERI has developed and patented a wind
speed recorder
 In the instrument a four cups rotor is employed
to sense the wind
 The motion of the cup is transferred after
reducing its speed by a gear system
 The inst gives a 24hrs record in one setting.
 Wind speed at a particular time and the
average wind speed can be found out from this
record.

15.  One of the simplest and most reliable instrument
is Whirling Psychrometer.
 Two thermometers, one with a wet cloth
surrounding the bulb are whirled in the air
 The temp of both dry and wet bulb thermometers
are noted
 The relative humidity of the air can be found by
referring to psyohrometeric table
 Other two instruments also can be used for
measuring of humidity
 Hair hygrometer
 Infra-red hygrometer

16.  Whirling Psychrometer

17. Hair Hygrometer
A hygrometer is an instrument used to measure the amount of humidity and water
vapour in the atmosphere, in soil, or in confined spaces. Humidity measurement
instruments usually rely on measurements of some other quantity such as
temperature, pressure, mass, a mechanical or electrical change in a substance as
moisture is absorbed

18. Infra – red hygrometer
A recording infrared absorption hygrometer which measures the absolute
humidity in a 1-meter light path is described.Balance is maintained by
automatically varying the temperature of the lamp supplying
the infrared energy, and the temperature of the lamp is a measure of the water
vapour in the sensing path

20.  A common inst for measurement of temp is the
thermometer.
 Mercury thermometer—thermal expansion
 Bimetallic thermometer—differential expansion of two
metals
 Electrical resistance thermometer—Variation in electrical
resistance
 In this temp probe a glass probe-bead type thermistor is
used .A thin walled conical shaped metallic tip is fixed at
one end of the stainless steel tube

22.  A knowledge of sunlight intensity is important
specially in places where photochemical smog
formation take place
 Instruments used to measure the radiant energy
from the sun are pyrheliometer, solarimeter and
chemical actinometer.
Pyrheliometer
 It is an instrument for measurement of direct
beam solar irradiance. Sunlight enters the
instrument through a window and is directed
onto a thermopile which converts heat to an
electrical signal that can be recorded.

23. Pyrheliometer

24.  A solarimeter is a pyranometer, a type of measuring
device used to measure combined direct and diffuse
solar radiation.
 An integrating solarimeter measures energy developed
from solar radiation based on the absorption of heat by
a black body.
 A solarimeter, also called “silicon cell pyranometer
 Pyranometers are instruments used to measure the
global radiation on a surface (direct and diffuse
radiation).
 Their functioning is generally based on the
measurement of the difference between the
temperature of a clear bright surface and a dark one.

27.  Chemical actinometry
involves measuring radiant
flux radiant via the yield
from a chemical reaction.
It requires a chemical with
a known quantum yield
and easily analysed
reaction products.

28.  There is a major impact of meteorological
conditions on air quality, normally in urban
areas where high density of pollutant emission
contains a permanent threat
 The majority of air pollution in many cities is
caused due to unfavourable metrological
conditions
 It is required to understand the process of
meteorology that result in adverse conditions
for dispersal of air pollutants

29.  The meteorological phenomena like sea, land
breezes and thermal internal boundary layers
highly influences the air quality in urban
agglomerations situated in the coastal zones

30.  The information about wind represent graphically
wind information includes direction, duration and
intensity
 The wind rose is the time honored method of
graphically presenting the wind conditions,
direction and speed, over a period of time at a
specific location.
 Accurate estimation of the dispersion of
pollutants in the atmosphere require a knowledge
of the frequency distribution of wind directions as
well as wind speed.

31.  To create a wind rose, average wind direction and
wind speed values are collected at a site, at short
intervals, over a period of time, e.g. 1 week, 1
month, 1 year or longer.
 The collected wind data is then sorted by wind
direction so that the percentage of time that the
wind was blowing from each direction can be
determined.
 Presented in a circular format, the wind rose shows
the frequency of winds blowing from particular
directions over a particular period.
 The length of each "spoke or segment" around the
circle is related to the frequency that the wind blows
from a particular direction per unit time.
 Each concentric circle represents a different
frequency, starting from zero at the centre to
increasing frequencies at the outer circles

33.  A wind rose plot may contain additional
information, in that each spoke/segment is broken
down into color-coded bands that show wind
speed ranges.
 Wind roses typically use 16 cardinal directions,
such as north (N), NNE, NE, etc., although they
may be subdivided into as many as 32 directions.
 In terms of angle measurement in degrees, North
corresponds to 0°/360°, East to 90°, South to 180°
and West to 270
 Special wind roses are sometimes constructed like
 Precipitation wind rose ,Smoke wind rose ,
Sulphur dioxide wind rose and Hydrocarbon wind
rose
 These are known as Pollution roses

36. Uses of wind rose
 Sailors use wind rose.
 Architects do, or should, use wind rose
information for the siting of buildings and
stadiums.
 Wind-power "farms" (wind mills) do extensive
wind rose type studies prior to erecting their
wind turbines.
 Also used for siting of industries in order to
minimize impact of air pollution on
neighboring cities