Observatory Equipments

AGRO - AUTOMATIC WEATHER STATION

• A system, with which weather observations may be collected, i.e. observed and disseminated, on real time basis without human interference are known as AWS.

AWS comprise of three units- (i) Field units, (ii) communication link and (iii) Ground receiving, processing and disseminating system.

• Rainfall, humidity, wind velocity, wind direction, sunshine duration, station pressure, soil moisture, soil temperature, leaf wetness, air temperature, maximum air temperature, minimum air temperature.

• For more details, download instrument handout from HERE.

DEW GAUGE

• Dew is an important source of soil moisture during non-rainy season especially in arid and semi-arid region.

• The dew is measured by DUV-Devani Dew Gauge and a dew album.

• There are rectangular wooden blocks of dimension 32 cm X 5 cm X 2.5 cm coated with red oxide which favours retention of dew deposits on it.

• For more details, download instrument handout from HERE.

GRASS MINIMUM THERMOMETER

• Grass minimum thermometer or terrestrial radiation thermometer is used to measure the actual minimum temperature experienced by the plants near the ground surface.

• The grass minimum thermometer is a glass thermometer filled with spirit or alcohol with a small index just like in case of minimum thermometer.

• The thermometer is exposed on short grass about one inch above ground surface on its support over the grass plot on a Y-shaped stand, so that bulb just touches the grasses.

• For more details, download instrument handout from HERE.

SOIL THERMOMETERS

Soil temperature is one of the important environmental factor of plant growth and development.

• For measuring soil temperature at depths of 5, 10 and 20 cm, the mercury-in-glass thermometers are used.

• These thermometers have a bend bulb of 1200 and the rest of the stem is straight.

• For more details, download instrument handout from HERE.

CAMPBELL SUNSHINE RECORDER

• Sunshine duration is a climatological indicator, measuring duration of sunshine in a given period for a given location.

• Crops convert solar energy into chemical energy during the process of photosynthesis and transpiration. These processes required much energy.

• The name of instrument is Campbell Stokes sunshine recorder.

• For more details, download instrument handout from HERE.

SINGLE STEVENSON SCREEN

• Stevenson screen is a wooden box specifically designed for housing four thermometers which record the surface air temperature in 0

• These four thermometers are maximum, minimum, dry and wet bulb thermometers.

• Thomas Stevenson designed this screen in 1866.

• For more details, download instrument handout from HERE.

MAXIMUM AND MINIMUM THERMOMETERS

• The maximum air temperature during 24 hrs duration is measured by using a maximum thermometer.

• Maximum thermometer is a mercury-in-glass thermometer provided with a constriction in the capillary of the glass tube below the lowest graduation of the scale.

• Minimum thermometer is a spirit or alcohol-in-glass thermometer ranging from -400C to +500C, having a light narrow index in the stem.

• For more details, download instrument handout from HERE.

DRY BULB AND WET BULB THERMOMETERS

• Air temperature at the time of observation is measured by means of a mercury-in-glass thermometer called the dry bulb thermometer.

DB thermometer has a capillary stem of which one end is a bulb containing mercury and other end sealed after removing air from the same.

• Dry Bulb thermometer is ordinary mercury-in-glass thermometer ranging from -350C to +550

• For more details, download instrument handout from HERE.

OPEN PAN EVAPORIMETER

• Its purpose is to isolate a small portion of the water surface in the tank so that it is not disturbed by waves produced by wind.

• The standard United States Weather Bureau (USWB) Class-A open pan evaporimeter is most commonly used to measure evaporation from free water surface.

• It consists of a 120.7 cm diameter and 25.4 cm deep pan made of 20 gauge galvanized iron sheet with a stilling well of size 10 cm diameter and 30 cm height placed within the tank.

• For more details, download instrument handout from HERE.

ORDINARY RAIN GAUGE

• Rainfall recorded on 08:30 hrs is the amount of rainfall for last 24 hrs, i.e. the amount of rainfall for that particular day.

• The principle of rainfall measurement is to obtain the depth of the layer of water that has fallen.

• Ordinary rain gauge (ORG) is an instrument used for measuring the amount of rainfall.

• For more details, download instrument handout from HERE.

SELF RECORDING RAIN GAUGE

• Self-recording rain gauge (SRRG) is an automatic device used to record a continuous rainfall for 24 hrs on a daily chart, if rain occurs.

• The characteristics of rainfall events viz. onset and cessation of rainfall, duration of rainfall, intensity of rainfall and the total amount of rainfall in mm can be obtained from the rainfall chart.

• It is a float type rain recorder in which the rain is led into a float chamber containing a light, hollow float.

• For more details, download instrument handout from HERE.

WIND VANE

• Wind influences the crop physically and physiologically. Hence, has to be measured for crop growth studies.

• An instrument generally measures the wind direction is known as Wind Vane.

Wind vane shows the prevailing direction of wind blowing to the observatory.

• For more details, download instrument handout from HERE.

ANEMOMETER

• Wind speed is measured with the help of cup counter anemometer.

• Wind influences the crop physically and physiologically. Hence, has to be measured for crop growth studies.

• Anemometer consists of 3 hemispherical cups fixed to the end of metal arms from a central point.

• For more details, download instrument handout from HERE.

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