Types of Weather Instruments and Their Usage/2020 agriadda247

Type of Weather Instruments and Their Usage-

Introducion-

Different instruments are used for measuring weather parameters in observatories and laboratories. Different instruments are available for measuring a weather element.
Depending on the level of accuracy required and the cost.

Thermometer-

A thermometer is a device that measures temperature or a temperature gradient.
1- Maximum thermometer
 2-Minimum thermometer

1- Maximum thermometer-

Maximum thermometer is used to measure the highest temperature attained during the day. 

2- Minimum thermometer-

Minimum thermometer is used to measure the lowest temperature reached on a day. It
consists of a graduated glass tube with alcohol in the bulb.

Thermometer

Stevenson screen-

Atmosphere air temperature is measured by means of thermometers housed in
a special wooden box called Stevenson screen  fixed at about 1.22 m above
ground level. It is a wooden rectangular box of length 56 cm, width 30 cm and height
40 cm with a double roof having lower side.
Meteorological thermometer are
Maximum thermometer
Minimum thermometer
Dry bulb thermometer
Wet bulb thermometer.

Stevenson screen

2-Meseaurement of Atmospherc Pressure

The pressure exerted by the atmosphere on earth surface is called atmospheric pressure. Pressure is defined as the force per unit area.
Most accurate Instrument used for measuring atmospheric pressure is
mercurial barometer. Different types of barometers used are

• Fortin barometer
• Kew pattern barometer
• Aneroid barometer
• Altitude barometer (altimeter)
• Barograph

ANEROID BAROMETER

It consists of a partially evacuated box
(sylphon cell sensitive to change in pressure)
with corrugated sheet of metal lid, held in position by a spring to avoid collapse of the top and bottom. It does not contain any liquid,

The cell is compressed when the pressure increase and expands when the pressure decreases.

Android barometr

The unit used in meteorology are milli bar(mb) .

Windvane-

The direction of wind can be obtained with windvane.

Direction N and S are the primary direction ,E and W are of second order and the remaining are of thired order.

                       Wind came

 Anemometer--

Anemometers are used for measuring

The wind velocity.

Robinson cup anemometer with four or three light aluminium cup fixed to arms of a steel cross mounted on vertical axis is commonly used in observatories.

The hight of anemometer 10 feet(3.05m) above ground level.

The cup rotates in anti-clock direction

The range of cyclometer is from 0 to 999 km/hr

Anemometer

Sunshine Recorder-

Duration of bright sunshine hrs is measured with sun shine recorder.

The instrument consist of a glass sphere of 10 cm diameter.

Sunshine recorder hight of pillar 5 feet (1.52m).

Sunshine recorder

 Rain Gauge -

The refined receptacles for measuring rainfall called rain gauges. Non recording rain gauges (ordinary rain gauge and self recording rain gauges (automatic recording rain gauges) are the two commonly use instruments for measuring rainfall.
     

Rainfall exceeding 2.5 cm in a day is called a rainy day.

Non-recording rain gauge

Evaporimeter -

The physical process by which any liquid escape from the surface in
atmosphere in gaseous state is called evaporation. The rate of evaporation is expressed in depth of water lost in unit time (mm day),

2.11.1 MEASURING DEVICES

There are several methods for measuring evaporation from water surfaces such
as rivers, ponds, reservoirs etc as indicated below:

• Evaporation pans
• Empirical formula

• Water balance method
• Energy budget method

The United States Weather Bureau Class A open pan evaporimeter or simply USWB Class A pan  is most commonly used in observatories of India.

USWB Class A pan

Choose the correct answer (s).

1. Agrometeorological observatory should be

(A) Away from all trees and structures
(B) Away from irrigation channels
(C) Free from waterlogging
(D) All the above

2. Ideal dimensions for agrometeorological observatory are:

(A) 50 x 30 m
(C) 60 x 40 m

(B) 60 x 30 m
(D) 55 x 36 m

3. Meteorological observatories of agricultural universities are under the
technical control of:

(A) ICAR, New Delhi
(C) CRIDA, Hyderabad

4. Agrometeorological observatories are maintained for:

(B) IMD, Pune
(D) CAZRI. Jodhpur

(A) Agricultural research
(C) Study of climate

5. Agrometeorological observatories of SAUs and colleges belongs to:

(B) Study of weather
(D) None of the above

(B) D-type
(D) B-type

(A) A-type
(C) C-type

6. Class-A observatories are expected to record observations:

(A) Once in a day
(C) Thrice in a day

(B) Twice in a day
(D) Once in three hrs

7. Which of the following instrument (8) measure wind direction?

(A) Radiometer

(C) Wind vane

(B) Pyranometer
(D) All the above


10. If the area of rainfall collector is 200 cm and rainwater collected is 100 cc then
the rainfall Is

(A) 20 mm
(C) 50 mm

(B) 2.0 cm
(D) 5.0 cm

Il Diameter of the measuring cylinder for measuring evaporation from pan
evaporimeter is exactly:

A) 1/10th of that of the pan
( 1/50th of that of the pan

(B) 1/100th of that of
12. If added water from measuring cylinder to pan evaporimeter is 20 cm. then the
evaporation will be
the pan
(D) 1/5th of that of the pan
LA) 20 cm
(C) 20 mm

(B) 200 cm
(D) 0.2 mm

13. The temperature range of maximum thermometer is:

LA) + 35" to -55°C
(C) - 55° to + 35°C

(B) + 55° to - 35°C
(D) - 35 to +55°C

14. The temperature range of minimum thermometer is:

(B) - 50 C to + 40

(A) + 40° to 50° C
(C) - 40 to +50° C

(D) + 40° 10 - 50°C

15. Most accurate instrument for measuring atmospheric pressure:

(A) Aneroid barometer
B-  Barograph
(C) Kew pattern barometer
D-। Mercurial Barograph

16 One bar is equal to

(A) 3 kPa
(B) 760 mm Hg
(C) 10132 mb
D) All the above

17. If a kg of air at constant pressure could hold 12 g of water vapour at a certain
Temperature, but contains only 9 g at that temperature, it has a relative
humidity of
(A) 75 per cent
© 25 per cent

(B) 50 per cent
(D) 100 per cent

18. In meteorology, commonly used unit of radiation is

(B) Calories cm 2 min

(A) Watt cm 2
(C) 25 per cent

(D) 100 per cent

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