Weather
Transcript of Weather
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
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 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.
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.
Lux meterLight intensity is measured by luxmeter
Many plants produce maximum dry matter under high light intensity.
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
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
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
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 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
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
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