Question 5 of 11beginner💡 UnderstandShort Answer3 marks

What is the unit used in measuring pressure? Why is the pressure measured at station level reduced to the sea level in preparation of weather maps?

Correct Answer

The atmospheric pressure is expressed in units of milibar. At sea level, the average atmospheric pressure is 1,013.2 milibar.

The pressure measured at station level is reduced to the sea level in preparation of weather maps to eliminate the effect of altitude on pressure. Since pressure decreases with height, stations at different elevations would record different pressures due to their altitude rather than weather systems. Reducing the pressure to sea level allows for a uniform standard for comparison between different places. This helps in studying the horizontal distribution of pressure and drawing isobars accurately on weather maps.

Exercise: EXERCISES | Q: 2(i) | (Page Page 9)
For More Understanding

Explanation

The answer is derived directly from the section 'Atmospheric Pressure' which states 'The atmospheric pressure is expressed in units of milibar.' The reasoning for reducing pressure to sea level is found under 'Horizontal Distribution of Pressure', where the text explains it is done 'In order to eliminate the effect of altitude on pressure... for purposes of comparison.'

Solution Steps

  1. Step 1: Identify the unit of pressure from the text, which is stated as 'milibar'.

  2. Step 2: Locate the explanation for reducing pressure to sea level in the 'Horizontal Distribution of Pressure' section.

  3. Step 3: Extract the key reasons: 'eliminate the effect of altitude' and 'purposes of comparison' to construct the final answer.

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