NCERT Book Class 11 Geography Weather Instruments Maps and Charts

Weather Instruments, Maps and Charts

WEATHER OBSERVATIONS Globally, meteorological observations are recorded at three levels, viz. surface observatories, upper air observatories and space-based observation platforms. The World Meteorological Organization (WMO), a specialised agency of the United Nations, coordinates these observations.

SURFACE OBSERVATORIES

A typical surface observatory has instruments for measuring and recording weather elements like temperature (maximum and minimum), air pressure, humidity, clouds, wind and rainfall. Specialised observatories also record elements like radiation, ozone atmospheric trace gases, pollution and atmospheric electricity. These observations are taken all over the globe at fixed times of the day as decided by the WMO and the use of instruments are made conforming to international standards, thus making observations globally compatible. In India, meteorological observations are normally classified into five categories depending upon their instruments and the number of daily  observations taken. The highest category is Class-I. Typical instrumental facility available in a Class-I observatory consists of the following:

1 Maximum and minimum thermometers

2 Anemometer and wind vane

3 Dry and Wet bulb thermometer

4 Rain gauge

5 Barometer

EXERCISES

1. Choose the right answer from the four alternatives given below. Which department prepares the weather map of India for each day?

(a) The World Meteorological Organisation

(b) The Indian Meteorological Department

(c) The Survey of India

(d) None of these

2.Which two liquids are used in maximum and minimum thermometers?

(a) Mercury and water

(b) Water and alcohol

(c) Mercury and alcohol

(d) None of these

3.Lines connecting the places of equal pressure are called

(a) Isobars

(b) Isohyets

(c) Isotherms

(d) Isohels

4.The primary tool for weather forecasting is

(a) Thermometer

(b) Barometer

(c) Maps

(d) Weather charts

5.If there is more humidity in the air, the difference between the readings of a dry bulb and a wet bulb will be

(a) Less

(b) More

(c) Equal

(d) None of these

2. Answer the following questions in about 30 words.

(i)What are the basic elements of weather?

(ii)What is a weather chart?

(iii)Which instruments are normally available in Class-I observatory to measure the weather phenomena?

(iv)What are Isotherms?

(v) Which meteorological symbols are used to mark the following on a weather map?

a) Rain

b) Mist

c) Sunshine

d) Lightning

e) Overcast Sky

3. Answer the following question in not more than 125 words.

(i)Discuss how weather maps and charts are prepared and how they are useful to us.

MAP READING

Study the Figures 8.12 and 8.13 and answer the following questions.

(a) Which seasons are shown in these maps?

(b) What is the value of the highest isobar in Figure 8.12 and through which part of the country does it pass?

(c) What are the values of the highest and the lowest isobars in Figure 8.13 and where are they located?

(d) What are the patterns of temperature distribution in both the maps?

(e) In which parts do you see the highest and the lowest mean temperature in Figure 8.12?

(f) What relationship do you see between the distribution of temperature and pressure in both the maps?

Please refer to attached file for NCERT Class 11 Geography Weather Instruments, Maps and Charts