Rain or atmospheric precipitation is responsible for making the water contained in the atmosphere return to the ground completing the water cycle , as well as providing the largest source of fresh water on which human activity and a large part of our landscapes depend. vegetables. However, both its quantity and its frequency can vary greatly throughout different places and different seasons of the year; This is why it is so important for climatology to study what are the factors that influence precipitation, the varieties or types of existing precipitation , etc.
What is precipitation and how is it classified?
Precipitation consists of the fall to the Earth’s surface of water from clouds , either in liquid or solid form . Clouds are therefore the main source of precipitation, although, as we all know, most of them do not always cause precipitation. So what has to happen for the water to reach the ground? For rain to occur, the small water droplets that make up the clouds (as well as the ice crystals that make up the clouds at higher altitudes) have to collide together to form larger droplets. Only in this way will air resistance be overcome and gravity will cause them to fall.
Precipitation can be classified according to several criteria. We can have several types of precipitation depending on its intensity, also depending on the form or configuration with which it manifests and, finally, according to its origin. Do not stop reading to discover them all!
The intensity of precipitation is defined as the amount of water that falls on the surface during a given time interval. It is usually measured in liters per square meter in an hour or, what is the same, in millimeters per hour (mm / h) and it is used to express it with the terms weak, moderate, strong, very strong and torrential. The types of precipitations according to their intensity are:
- Weak when the intensity is less than 2 mm / h.
- Moderate when it is 2 to 15 mm / h.
- Strong from 15 to 30 mm / h.
- Very strong from 30 to 60 mm / h.
- Torrential when they exceed 60 mm / h.
As we will see later, one of the types of precipitation that is essentially characterized by its intensity are showers. Showers present rapid variations in the intensity of precipitation, that is, they begin and end abruptly and accumulate large amounts of water in a very short time.
As a curiosity, it is worth mentioning that showers and torrential rains are quite frequent in the Mediterranean coast area in autumn, where the phenomenon of the cold drop or DANA occurs . Here we tell you more about What is the cold drop .
Types of precipitation according to the form of manifestation
The most striking thing about the manifestation of precipitation is that it can occur in a liquid or solid state. The liquid precipitation are drizzle, rain and rain water.
- Drizzle: also known as calabobos. It is made up of numerous fine drops of water with a diameter of less than half a millimeter. The rate of fall is so slow that they seem to float in the air. They typically come from stratus-like clouds.
- Rain: it is the most common form of precipitation, to the extent that the two terms are used synonymously on a good number of occasions. The drops have a diameter of more than half a millimeter and fall with moderate speed. It almost always comes from the nimbostratus and altostratus.
- Showers of water: also called downpours or showers. The drops are usually larger than those of the rain and, as we have already said, they start and end abruptly. The only clouds that produce them are cumulonimbus clouds.
We take advantage of the mention of liquid precipitation to remember the so-called “acid rain”, although in reality it is contaminated water with a very high level of acidity that returns to the earth’s surface and, therefore, falls in any of the forms of precipitation. Here you can learn more about What is acid rain, its causes and solutions , as well as What are the possible solutions for acid rain .
The solid precipitation is snow, snow showers, hail and snow pellets.
- Snow: it is formed by conglomerates of ice crystals that are mostly branched (sometimes in the shape of hexagonal stars) that are welded to form flakes. When the snow melts slightly, it is also spoken of sleet. Here we tell you what a snowstorm is and how it is formed .
- Snow showers: with the same characteristics as water showers, it is a more copious precipitation than ordinary snowfall.
- Hail: they are rounded and translucent grains of ice. The diameter varies between 5 and 50 millimeters and they fall, like showers, in a short period of time. They are only produced by cumulonimbus.
- Granulated snow: they are opaque white grains of about 2.5 millimeters in diameter. They are brittle and easily crushable, as if it were soft hail.
The origin of the rains or precipitations is linked to the mechanism by which the clouds were formed from which they come. These are the types of precipitation according to its origin :
- We will have orographic precipitations when the associated clouds have formed with the rise and cooling of the air that has had to exceed a mountainous area. Orographic rainfall occurs mainly on the windward slope, being a good indicator the greater growth of vegetation.
- Convective precipitation also occurs where clouds have been formed by a process called convection. This consists of the heating of air pockets, due to the heat that radiates from the ground on sunny days, which subsequently rise (hot air is lighter than cold) and cool, forming cumuliform clouds. The convective precipitations give rise to the mentioned showers.
- We will have frontal precipitation when it comes from clouds associated with fronts, that is, to separation fringes between air masses with different temperature or humidity conditions, which can be of two types: warm fronts and cold fronts.