This document describes various instruments used to measure different weather elements. It discusses rain gauges to measure rainfall, wet and dry bulb thermometers and hair hygrometers to measure relative humidity, sunshine recorders to measure sunlight duration, luxmeters to measure light intensity, Stevenson's screens and maximum/minimum thermometers to measure air temperature, barometers to measure air pressure, anemometers and wind vanes to measure wind speed and direction, evaporimeters to measure evapotranspiration, radar to detect precipitation, and radiosondes carried by weather balloons to measure temperature, humidity and pressure at different altitudes.

1. Instruments used for
measuring weather
elements

2. Rain Guage

3. Rain gauge
@ used to measure rain
@ 50 cm tall, rain water caught in a funnel on top
runs down into a measuring cylinder
@ in mm
@intensity and duration can be obtained
@High intensity rainfall- 60 mm in 30 min
@Low intensity rainfall – 60mm in 300 min

4. Relative Humidity
@ measured by
Wet and Dry bulb Thermometer
Hair Hygrometer

5. Hygrometer

6. Wet and Dry bulb
Thermometer
One has a wet cotton or linen wick absoring its bulb.
Evaporating water from the wick absorbs heat from
the thermometer bulb , causing the thermometer
reading to drop.
Two identical thermometer
Difference between dry and wet bulb thermometer
ids compared to psychrometric charts.

7. Hair Hygrometer

8. Hair Hygrometer
Humidity stretches the hair of hygrometer while
dryness shortens it .
Stretching a hair between a fixed and a movable point
to measure humidity over time.

9. Sun Shine Recorder

10. Sunshine recorder
Light duration refers to the number of hours between
sun rise and sun set.
The recorder consists of a sphere arranged to focus
the suns image on to bent strop of card on which the
hours are marked.
 the length of burnt track on the paper enables the
sunshine duration to calculated.
Interruptions in track indicate passing clouds.

11. Luxmeter

12. Lux meter
Light intensity is measured by luxmeter
Many plants produce maximum dry matter under
high light intensity.

13. Stevenson’s screen

14. Stevenson’s screen
A wooden box fitten to steel frame to protent
weather instuments like thermimeterm barometer etc
from sun’s rays .
Dooe open to the north in tge northern hemisphere
in order to prevent direct sunlight, painted white to
recflect radiatin , set at a ht of 1.25m above ground
Houses 4 types of thermometer
@maximum, minimum, dry & wet bulb thermometer

15. Maximum and Minimum
Thermometer

16. Minimum (alcohol)
thermometer
Recording daily minimum temperatures
Alcohol in glass thermometer with light movable
index in its capillary tube . The index is pulled back
by surface tension when the temperature falls , when
the temperature rises alcohol expands leaving the
index in the same place.
Kept in horozontal position.

17. Maximum (mercury )
thermometer
It can record the highest temperature in a time
period.
There is constriction just above the bulb of the
thermometer that causes the mercury to rise but
when it cools, gravity doesn’t allow all of the mercury
to fall.
It kept in horizontal position

18. Fortin’s Barometer

19. Mercury barometer

20. Barometer
Instruments used to measure the current aier
pressure at a particular location.
Aneroid and mercury barometer
Aneroid - much smaller and can also record a week’s
data

21. Anemometer

22. Cup anemometer
To measure the wind speed .
From the rotation of wind mill which consist of 3-4
hemispherical on conical cups
Each fixe d to the ends of horizontal arms attached
to a vertical axis.
Rotation of cups is transmitted to a technical counter
which records the wind speed

23. Wind vane

24. Wind vane
Indicates the direction of wind.
Fixed at a good ht
On the top of a vertical post
In spots where there are no obstruction to the
movement of wind like trees , buildings

25. US open pan evaporimeter

26. Us open pan evaporometer
To measure evapo transpiration

27. RADAR

28. RADAR
RAdio Detection And Ranging
Is an object detection system that uses
electromagnetic waves specifically radio waves to
identify the range altitude, direction or speed of
objects
Meteorologists use radar to monitor precipitation . It
has become he primary tool for short term weather
forecasting and to watch for severe weather such as
thunderstorms ,tornadoes ,winter storms,
precipitation types

29. Weather balloon

30. Radiosonde

31. Radiosonde
Small box like instrument that is carried into the
upper atmosphere by balloon as it travels upward it
transmits meteorological measurements o t ground
station
It measure temp, humidity and air pressure
A helium filled neoprene balloons that are designed
to burst when they reach a specified altitude
So not have to be returned to earth to retrieve data
Twice a day a round the world at midnight and at
noon - bursts it falls back to earth by parachute

32. Cirrus cloud