How Does Rainfall Vary

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Geography Essay – How and why does rainfall vary? Precipitation occurs when the particles of liquid water or ice formed within a clouds fall towards the ground. And it is a result of vertical heat transfer processes such as conduction, convection, radiation and latent heat transfer through space and time. Seasonal variations and latitudinal positions are macro/global scales influence the rainfall. Monsoons are regional-scale winds that affect the precipitation. And the rest of the factors such as land and see breezes and within a day are smaller scales. So that rainfall variations mainly across space and time by different factors and scales. Rainfall may vary across time within a day (micro scale) and within a year at temperate regions as a form of convectional rain. The convectional rain usually occurs between late morning to early afternoon. And associated with the formation of massive columns of rain-bearing clouds- cumulonimbus clouds. It lasts for a short duration and be highly localized as well as accompanied by lightning and thunder. Since it occurs with high temperatures and moist areas, it is very common in tropical regions. Fig1 From the fig.1 we can see that the solar radiation heats up the ground surface by conduction, convection. Air warms up by contacting with warm ground surface, become less dense and rises as a convection current. After that, the rising air expands, cools, relative humidity rises until condensation of water vapour occur above condensation level. Finally air meets air equally warm, stops rising and descends. The rainfall variation across time is within a year as well. This will lead to relief rain that affected by monsoons. Monsoon is a regional phenomenon, occurring in Asia-pacific region and Africa, which is the seasonal reversal of prevailing wind direction due to the differential heating between the landmasses
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