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Types of Precipitation

Types of Precipitation

Convectional Precipitation
Orographic Precipitation
Cyclonic Precipitation

  • Convectional Precipitation

Convection is the process of heat transfer from one place to another by the actual movement of hot fluids like gases and liquids. The main causative element is the thermal convection of moisture laden air. Solar radiation is a source of heat for this to occur. The air that comes in contact with the heat surface of the earth is also heated as a result of which the lapse rate at the surface of the earth increase rapidly As a result the air becomes unstable and vertical currents are then set up which carry heat and moisture to higher levels from the earth surface. Due to convection, the moist Air in the lower levels of atmosphere rise up to condensation level where small clouds develop and with further convection the clouds increase in size resulting in a thunderstorm. Lightning, thunder, gusty surface winds, showers and sometimes hails accompany a thunderstorm. As the warm moist air from the ground is lifted up, more and more water will condense and the water drop and ice crystals will increase in size  When these drops are no longer supported by the up drafts, there drafts will begin to fall in the form of thunderstorm. Such a thunderstorm is called an “Air Mass Thunderstorm.

  • Orographic Precipitation

In this type of precipitation, expansion and condensation occur because moisture-laden air is lifted due to the presence of orographic barriers This type of precipitation is more pronounced on the windward side of the mountain, but the leeward side also receives some precipitation. Heaviest precipitation due to the south easterlies occur along the southern slopes of Himalayas and its other ranges. The monsoon rainfall decreases gradually as the distance from the line of heaviest rainfall increases. Orographic precipitation also occur in the in land areas where mountain ranges rise ablove the surrounding areas in the path of moisture-laden air masses But on these areas orographic precipitation is intermingled with other types of precipitation. Prevailing in the area so it becomes quite difficult to quantify the exact amount of precipitation that has occurred due to orographic effects only. Normally the duration of this type precipitation is long. The intensity is normally medium to high. The size of orographic precipitation might not cover a very large area. Its dimensional length can be long but the width of such precipitation is fairly low.

  • Cyclonic Precipitation

Precipitation plain areas is generally cyclonic in nature, Cyclones are generally of two types depending upon

whether they occur within or beyond the tropics, Generally all the cyclones in Indo Pak subcontinent are of tropical variety. Tropical cyclones are violent storms, which are generally formed in the air mass of low latitude where the . temperature is high. Normally formed in the Indian Ocean in the Indo Pak area, In the center of a cyclonic storm there is as small low pressure air, Isobars around such low pressure are very nearly circular in shape, Tropical cyclones have nearly a diameter of 300-400 miles, The wind speed may be high as 60-90 miles/hour. Winds around the tropical storm are parallel to the isobars, As the center of the storm approaches, the high winds dry down as calm prevails in the center, The diameter of the eye of storm is 50 miles. The winds around the center of the storm normally blow in circular path and at the same time the air is rising as well, The vertical motion compels the air to be cooled adiabatically, As the air is already humid, condensation takes place rapidly resulting in rainfall and widespread thunderstorm but over the center of the , the weather is usually fair. In the Indo Pak subcontinent, these storm are formed in the Bay of Bengal in different months, These storms normally do not reach Pakistan but when they do reach, these are fed with moisture-laden air from the Arabian Sea resulting in heavy rainfall. These storms are very destructive and cause loss of life and property over the coastal districts.

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My name is Mustafa Awais, I am basically from Pakistan & Currently living in Saudia Arabia, I am Civil Engineer as well as Web Master.

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