Types and Distribution of Rainfall

  • The process by which, water from the atmosphere falls down on earth is known as precipitation. No change in state of water is involved in this process.
  • The main types of precipitation are rain, drizzle, snow, sleet, and hail.
  • Precipitation, which reaches ground in the form of liquid, is called rain.
  • Drizzle is the lightest form of precipitation.
  • Snowfall is the precipitation composed of ice crystals.
  • Sleet is a mixture of rain and snow.
  • Hailstones are frozen lumps of ice produced by thunderstorms.
  • The amount of rainfall depends on the moisture content of air.
  • Factors determining the rainfall are land and sea contrast, direction of prevailing winds, and presence of mountains.
  • The three main types of rainfall are convectional rainfall, orographic rainfall, and cyclonic rainfall.
  • Convectional rainfall occurs in summers or during hotter part of the day. It is very common in the equatorial regions and interior parts of the continents.
  • The chief characteristic of orographic rainfall or relief rain is that the windward slopes receive greater rainfall. Leeward slopes remain rainless and dry.
  • Cyclonic or frontal rainfall occurs in the area where cyclones occur.
  • The distribution of rainfall on earth depends on location and season. About 98% of earth’s surface receives rain in summer.
  • Regions of heavy rainfall are equatorial regions, eastern margins of continents in sub-tropical latitudes and western margins of continents between 40º and 60º latitudes.
  • Regions of scanty rainfall are Polar Regions, Western margins of continents in the trade wind belt and Eastern margins of continents in the westerlies wind belt.
  • Temperature and rainfall are the two most important elements of climate.
  • Factors affecting climate are latitude, land and sea contrast, altitude, wind direction, ocean currents, vegetation and, direction of mountain ranges.
  • The instrument used to measure the amount of precipitation is called rain gauge.

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  • Q1

    When water vapour is added to the atmosphere, relative humidity -

    Marks:1
    Answer:

    Increases

    Explanation:

    Relative humidity is given as a percentage.  This percentage tells you how close the air is to being saturated.  If the relative humidity is 100%, the air is saturated.  If the relative humidity is 50%, the air contains half the water vapor required for it to be saturated.  If the amount of water vapor in the air increases, the relative humidity increases.

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  • Q2

    The ratio between the quantity of water vapour present in the atmosphere at a given temperature to the maximum quantity of water vapour that the atmosphere can hold at that temperature is called-

    Marks:1
    Answer:

    Relative humidity

    Explanation:

    The ratio of the actual amount of water vapor in a given volume of air to the amount which could be present if the air were saturated at the same temperature. It's commonly expressed as a percentage.

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  • Q3

    The air which can hold more water vapour is a –

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    Answer:

    Hot air

    Explanation:

    As temperature increases the air can hold more water because it is able to sustain more water molecules in a gaseous state by increasing the rate of vaporization.

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  • Q4

    The water vapour-holding capacity of the air depends upon its -

    Marks:1
    Answer:

    Temperature

    Explanation:

    The water holding capacity of air depends sharply on the air's temperature (i.e. the warmer the air is, the more water it can hold).There is no direct relationship between temperature and humidity. However humidity can change a person’s comfort at the same temperature as humans are sensitive to the water vapor content in the atmosphere.

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  • Q5

    The amount of water vapour present in the atmosphere is referred to as -

    Marks:1
    Answer:

    Humidity

    Explanation:

    Humidity is the amount of water vapor present in the air. Water vapor is the gaseous state of water and is invisible to the human eye. Humidity indicates the likelihood of precipitation, dew, or fog.

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