Types of rainfall

Hi everyone! I'll be sharing with everyone about the different types of rainfall today. Some might wonder, rain is simply water droplets falling back onto earth, how different could it possibly get?! But yes, there're in fact 3 different types of rainfall, and I'll be explaining them to you in detail.


1. Convectional rainfall


This is the type of rainfall we get in Singapore :) As the name suggests, it is a result of convection of the wind patterns on earth. Warm air rises and cold air sinks in the convectional current due to density. The hot air and the rays from the Sun intensely heat the ground, and the warm ground warms the air immediately above it. This produces a bubble of warm air that begins to rise. This air cools as it rises in the atmosphere and eventually reaches a dew point temperature causing clouds to form. As these clouds accumulate, the water vapour that has condensed to form water droplets inside will be too heavy, and fall back to earth as rain. This rain is usually heavy and lasts for only a short period of time.


Here's a simple illustration to aid everyone:





2. Orographic rainfall


You can find this type of rainfall at some of the earth's great deserts :) The word "orographic" means that it is related to mountains. When moist, warm air from the sea evaporates, the air is forced up against mountain slopes at places with mountains. At the tip of the mountain top, air formed is cooled at dew point, before condensing to form water droplets, which ultimately fall back down as rainfall. At mountainous regions, air drops down over the high ground, gaining temperature and increasing the amount of water it can hold. That is why the flat regions below mountains hardly experience rain, and this area is known as rain shadow. This is a diagram to illustrate orographic rainfall:



3. Frontal rainfall

Frontal rainfall is caused when frontal systems form when warm and often tropical air meets cooler air. Stratiform precipitation falls out of nimbostratus clouds. Nimbostratus clouds are a formless cloud layer that is almost uniformly dark grey. Usually, nimbostratus is a sign of steady moderate to heavy precipitation. It looks something like this:

Scary, isn't it?! ):

Back to the point on warm and cool air. As hot air is lighter and less dense than cold air, it rises over it. As warm air is forced to rise further, condensation occurs at dew point, and over time rain droplets will accumulate, resulting in the scary looking cloud as seen above (because the water droplets block out sunlight from the Sun).


On the other hand, when heavier and denser cold air pushes beneath and lifts the warm air, a cold front occurs. This causes lowered pressure along the cold front and can cause the formation of showers and thunderstorms when enough moisture is present.

Alright, I hope that everyone has learnt a new thing or two through this new entry. Tata for now :)

Done by: Clarissa (7)