Understanding Weather Parameters and Instruments

This question asks us to match different weather parameters with the specific instruments used to measure them. Accurate measurement of weather parameters is crucial for meteorology, climate studies, and various practical applications like agriculture and aviation.

Matching Weather Parameters to Measuring Instruments

Let's examine each weather parameter listed and identify the standard instrument used for its measurement:

• Duration of Sun Shine: This parameter refers to the total time in a day that the sun's rays are strong enough to cast a shadow. The instrument commonly used for this is the Campbell-Stokes recorder.
• Atmospheric Pressure: This is the pressure exerted by the weight of the air column above a given point. Atmospheric pressure is measured by a barometer.
• Relative Humidity: This is the amount of water vapor present in the air relative to the maximum amount the air can hold at a given temperature. Relative humidity is measured using a hygrometer or a hygrograph (which records changes over time).
• Evaporation: This is the process by which water changes from a liquid to a gas or vapor. The rate of evaporation is often measured using instruments like a Pan Evaporimeter, which measures the amount of water evaporated from a standard pan over a specific period.

Based on these standard meteorological instruments, we can create the correct matching pairs:

• Duration of sun shine (A) matches with Campbell-stokes recorder (III).
• Atmospheric pressure (B) matches with Barometer (IV).
• Relative Humidity (C) matches with Hygrograph (I).
• Evaporation (D) matches with Pan Evaporimeter (II).

Summary of Correct Matches

This gives us the combination: A - III, B - IV, C - I, D - II.

Revision Table: Key Weather Measurement Instruments

Additional Information on Weather Measurement Instruments

Understanding how these weather parameters are measured provides deeper insight into meteorological data collection.

Barometer (for Atmospheric Pressure)

There are different types of barometers:

• Mercury Barometer: Uses a column of mercury in a glass tube. The height of the mercury column balances the atmospheric pressure.
• Aneroid Barometer: Uses a small, flexible metal box called an aneroid cell, which is sealed and evacuated. Changes in atmospheric pressure cause the box to expand or contract, and this movement is amplified to move a needle on a dial.

Hygrometer / Hygrograph (for Relative Humidity)

Hygrometers measure humidity. A hygrograph is a recording hygrometer, meaning it continuously tracks and records humidity levels over time, often producing a graph (hygrogram). Common types include:

• Hair Hygrometer: Uses the principle that human hair changes length slightly with changes in humidity.
• Psychrometer: Uses two thermometers, one dry-bulb and one wet-bulb. The difference in temperature is used to calculate relative humidity.

Campbell-Stokes Recorder (for Duration of Sunshine)

This instrument uses a glass sphere to focus sunlight onto a specially designed card. As the sun moves across the sky, it burns a trace on the card. The length of the burned trace indicates the duration of bright sunshine. The card is changed daily.

Pan Evaporimeter (for Evaporation)

The most common type is the Class A Evaporation Pan. It is a standard circular pan filled with water, usually placed on a wooden platform. The water level in the pan is measured daily. The decrease in water level over 24 hours, after accounting for any precipitation, represents the evaporation amount.