Precipitation and Measuring Temperature and Rainfall
Precipitation is the process through which water from the atmosphere falls down on earth. In this process, only geographical location changes, that is from the atmosphere to the hydrosphere and lithosphere. It occurs when tiny cloud droplets join together to form large water drops. These water drops being heavier cannot be held in the atmosphere, so they fall down on earth. Precipitation is classified according to the form in which it reaches the ground. The form of precipitation is determined by the temperature of air, both outside and inside the cloud. Precipitation can be in the form of:
The amount of rainfall depends upon moisture in the air, which is determined by three factors:
Land and sea contrast
Direction of prevailing winds, and
Presence of mountains
Moist air rises above to cooler regions of the atmosphere. This forms clouds and brings rain. Thus, when air rises, precipitation takes place. Some of the common causes of rising air are convection, mountain barriers, and cyclones. Based on these causes, three types of rainfalls are identified. These are:
Relief or orographic rainfall, and
Cyclonic or frontal rainfall
Rainfall depends on the location of the place. It also depends on the season. 98% of the earth’s surface receives rain during the summer season.
Rainbows are caused by refraction and total internal reflection of sunlight. Drops of rain act as prisms. They break down sunlight into its seven constituent colours.
Thunderstorms are severe local storms accompanying thunder and lightning. Intense electrical field develops inside the cloud. A positive charge is induced on the ground for several kilometers around the storm.
Thermometers measure different readings in sunlight and in shade. Meteorologists use a shelter called Stevenson Screen to place their instruments.
A rain gauge is used to measure the amount of rain. Snowfall or hail is measured by melting it and including it in the total rainfall of the place.
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