GKMS : Modipuram - Agromet Observatory

GKMS : Modipuram

AGROMET UNIT

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 120⁰and the rest of the stem is straight

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.

rom -35⁰C to +55⁰

DRY 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

WET BULB THERMOMETERS

MAXIMUM 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 THERMOMETERS

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

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.

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.

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.

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.

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.

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