Weather

Instruments used for measuring weather

elements

Rain Guage

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

Relative Humidity@ measured byWet and Dry bulb ThermometerHair Hygrometer

Hygrometer

Wet and Dry bulb ThermometerOne 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 thermometerDifference between dry and wet bulb

thermometer ids compared to psychrometric charts.

Hair Hygrometer

Hair HygrometerHumidity stretches the hair of hygrometer

while dryness shortens it .Stretching a hair between a fixed and a

movable point to measure humidity over time.

Sun Shine Recorder

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.

Luxmeter

Lux meterLight intensity is measured by luxmeter

Many plants produce maximum dry matter under high light intensity.

Stevenson’s screen

Stevenson’s screenA 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

Maximum and Minimum Thermometer

Minimum (alcohol) thermometerRecording daily minimum temperaturesAlcohol 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.

Maximum (mercury ) thermometerIt 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

Fortin’s Barometer

Mercury barometer

BarometerInstruments 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

Anemometer

Cup anemometerTo measure the wind speed .From the rotation of wind mill which consist

of 3-4 hemispherical on conical cupsEach 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

Wind vane

Wind vaneIndicates the direction of wind.Fixed at a good htOn the top of a vertical post In spots where there are no obstruction to

the movement of wind like trees , buildings

US open pan evaporimeter

Us open pan evaporometer

To measure evapo transpiration

RADAR

RADARRAdio Detection And RangingIs 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

Weather balloon

Radiosonde

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

Cirrus cloud