The hydrometeorological risks refer to the probability of occurrence of a disaster caused by an atmospheric phenomenon related to water. These atmospheric phenomena can be tropical cyclones, floods, tornadoes, electrical storms, droughts, torrential rains, snowfalls and hailstorms..
The occurrence of one of these events does not necessarily imply a disaster, there must also be a condition of vulnerability. For this, the atmospheric phenomenon and the existence of human communities or infrastructures that can be seriously affected must coincide in space and time..
Therefore, risk is the product of the combination of these two factors, the cause and the lack of protection against it. For example, if a river overflows, but there is no town nearby, there is no disaster. Neither is there if the town has a retaining wall that protects it from flooding or the risk is minimal..
The same happens with a heavy snowfall, which does not represent a meteorological risk for a city that is used to such events. But it is a meteorological risk for a city where it usually does not snow or does it slightly.
Hydrometeorological risks are very relevant, since hydrometeorological phenomena are those that produce the greatest human and economic losses in the world. On the other hand, although much progress has been made in the ability to predict these phenomena, in general the ability to predict them is low.
As an example, only in Mexico, between 2001 and 2013, hydrometeorological phenomena affected about 2.5 million people. On the other hand, the economic costs reached 338 billion pesos.
The causes of meteorological risks are related both to the behavior of the atmosphere-hydrosphere system, and to the lack of prevention against the phenomena it triggers. For there to be a risk, two causative conditions must be present, an extreme hydrometeorological phenomenon and a vulnerable social condition.
The Earth system, formed by the interaction of the atmosphere, hydrosphere, and lithosphere, follows regular cycles, but occasionally generates extreme variations. Atmospheric pressure and temperature variations produce alterations in climatic regularities.
Due to this, events such as cyclones, particularly heavy rains or heavy snowfalls occur. On the other hand, exceptional rains in an area can be the cause of rivers overflowing, causing floods..
To this is added the fact that human intervention produces serious environmental imbalances and produces global phenomena such as the so-called global warming or increase in the average temperature of the earth. It produces other extreme phenomena, such as large floods in some places and severe droughts in others..
Therefore, the human being himself is one of the main causes of the hydrometeorological risks that he faces. In fact, the frequency and intensity of extreme hydrometeorological phenomena is increasing and this influences the deforestation of forests and jungles, as well as atmospheric pollution..
Lack of foresight is the other cause that can lead to hydrometeorological risks, since there is no risk if you are not exposed to the phenomenon. In such a way that if the provisions are made in the face of the possible risk, it is minimized or ceases to exist..
For example, if a river overflowed and washed away a town built right on its bank, it was an obvious risk. But if you take the precautions and build sufficiently strong and high retaining walls, there is no such risk..
Cyclones are strong winds rotating towards a center of low atmospheric pressure that are accompanied by strong storms with heavy rains. There are different types, including tropical cyclones or hurricanes, that occur over warm oceans.
In this case, the risk of a cyclone or hurricane is associated with both marine navigation and the cyclone's contact with populated coasts. There are also storms, which are cyclones that occur in temperate zones.
Rain floods as a result of hydrometeorological phenomena are caused by exceptionally heavy or continuous rains, which cause rivers to overflow. This represents a risk for people and infrastructures in its vicinity.
In some cases the risk is increased due to deforestation of the river headwaters. This increases the amount of water that reaches the river and also the amount of sediment that fills its channel..
A tornado is a column of air in strong rotation of winds, which occurs on land or over the sea and moves at high speed. The risk of tornadoes occurs when a front of dry and humid air that rises and another of dry and cold air that falls collide. This phenomenon represents a high risk due to the great energy it generates.
The risk is given by the lack of water, which is a growing risk worldwide. Due mainly to global warming, some areas of the planet are having less rainfall and desert areas are expanding. Among other things, deforestation is a factor that increases the risk of droughts.
Torrential rains represent a hydrometeorological risk in several ways. As already pointed out, they can be the cause of rivers overflowing, but they can also cause mud runoff in mountainous areas. As well as the loss of crops by saturating the soil and drowning the roots or simply knocking down the crop plants.
In the specific case of mud runoffs, deforestation of mountain slopes plays an important role in their risk character. This is due to the loss of protection of the soil against rain, decreasing the infiltration of water and increasing the water that runs off the surface..
Precipitation in the form of snow occurs seasonally naturally in temperate or cold climates, as well as in high mountain areas. However, occasionally snowfall can be extreme in duration and amount of snow..
In this case, they represent a significant hydrometeorological risk, especially when they occur in regions not used to heavy snowfall. This happens due to extreme drops in temperature in the upper layers of the troposphere, plus the presence of large concentrations of humidity..
Hail is a lump of ice that forms at high altitude inside clouds, amid cycles of ascending and descending winds. In this way they accumulate layers of ice until they fall under their own weight causing hailstorms..
These irregular balls of ice are between 5 and 50 millimeters in size, sometimes larger. Therefore, they represent a high risk when impacting on people, animals, plants, vehicles or structures..
The risk faced in this case is the flooding of coastal areas by particularly high and strong waves. These are caused by strong high-altitude winds that blow from the sea, generally associated with storms, such as cyclones..
These are storms accompanied by lightning, that is, discharges of atmospheric electricity. These rays are characterized by producing a discharge of light that we call lightning and a noise that we call thunder..
They represent a risk both for air navigation and for people and objects on the ground, since their impact involves electric discharges of up to 100 million volts. For these electrical storms to occur, there must be hot air conditions with high humidity rising in an unstable atmosphere..
It is an alteration of the air temperature gradient, which normally goes from a warm air close to the ground to a colder one at a higher altitude. Therefore, when a thermal inversion occurs, the air near the ground is colder than that found in the upper layer. This occurs when there is a strong cooling of the soil, cooling the air in contact with it..
The risk associated with thermal inversions is that they do not allow air to rise. Therefore, in industrial or urban areas, pollutants accumulate near the ground, it is the so-called smog that seriously affects health.
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