Weather and climate

NCERT
CLASS 7
CHAPTER 6
YOUTUBE LINK: https://youtu.be/drd_cCdiMQ8

1. WEATHER AND CLIMATE Class 7 NCERT Chapter-6

2. INTRODUCTION Weather- state of atmospheric conditions at a given place and time Climate- average over all atmospheric conditions over a large region for a long period of time(about 35-40 years)

3. ATMOSPHERIC TEMPERATURE Temperature measures the intensity of heat or it is the degree of hotness Sun radiates heat and light energy as solar radiation Insolation- amount of solar radiation received by earth’s surface Terrestrial radiation- heat radiated back from the surface T emperature is measured by thermometer Fahrenheit and Celsius are two main scales to measure temperature

4. DISTRIBUTION OF TEMPERATURE

5. ATMOSPHERIC PRESSURE Weight of atmosphere is exerted as atmospheric pressure Measured by barometer and millibar(mb) is the unit Normal atmospheric pressure at sea level is about 76 cm of mercury column in barometer Variations in atmospheric pressure is due to- temperature of air; density of air; moisture present; height above sea level Air moves from region of high pressure to the region of low pressure

6. DISTRIBUTION OF ATMOSPHERIC PRESSURE Tendency of atmospheric pressure- decreases with increase in temperature; decrease with increase in altitude; moist air exerts less pressure than dry air; earth’s rotation modifies its distribution Highest at sea level and lowest at mountains T here are 7 major Pressure belts-

7. WINDS Horizontally moving air is wind while the air moving vertically is air currents Wind vane helps to find the direction of winds Anemometer measures the speed of wind

8. MOISTURE Water content in the air; exists in solid, liquid and gaseous state Equatorial air has more moisture Air has more moisture during summers than winters Amount of moisture decreases with increase in height It is almost zero in the cold air of polar regions during winters Forms of moisture- Evaporation; Humidity; Condensation; Precipitation

9. EVAPORATION Added in the atmosphere through evaporation of water Increases with rise in temperature and vice versa Loss of water through tiny pores in the leaves is known as transpiration

10. HUMIDITY Actual amount of water vapour present in air is known as humidity or absolute humidity Ratio between actual amount of water vapour and maximum capacity of air to hold water vapour at a particular temperature is called relative humidity

11. CONDENSATION Condensation is the change of water from its gaseous form (water vapor) into liquid water. Condensation generally occurs in the atmosphere when warm air rises, cools and looses its capacity to hold water vapor Clouds- When small droplets of water condenses along dust or smoke particles There are 3 types of clouds- Cirrus, Cumulus, and Stratus Rain bearing clouds are given prefix or suffix nimbus

12. PRECIPITATION When small water droplets join together, grow till they are no longer to hold the weight and finally fall down as raindrops or flakes of snow, the process is called precipitation

13. TYPES OF RAINFALL