In the world of meteorology, the following are very important: maps They represent wind conditions, storms, anticyclones, etc., to predict the weather. Weather maps are nothing more than graphic representations that help us understand the values of certain meteorological variables in a given geographic area. Meteorologists all use these synotic maps, since its use provides a great deal of knowledge and an interesting image of the set of situations we can encounter in the atmosphere.
In this case, we're going to talk about precipitation. Do you want to know how these maps work and how they help predict the weather?
Atmospheric variables
To find out what the weather will be like the next day, meteorologists study some of the most important meteorological variables that provide more information about the atmosphere. One of the variables that provides more information is atmospheric pressure. At the Earth's surface, atmospheric pressure is indicated in an isobar mapIsobars are lines along which atmospheric pressure is uniform. Therefore, on maps where widely separated isobars can be seen, it means good weather and atmospheric stability.
On the other hand, if the isobar map has numerous lines together, it means that a storm or cyclone is approaching. But a question arises in all this: why do lines with equal atmospheric pressure indicate that a storm is approaching? The relationship between atmospheric pressure and the possibility of precipitation is as follows: The closer the isobars are, the stronger the wind will blow, and therefore, the greater the atmospheric instability. This instability can cause rain, as we'll see later.
Isobar lines can also be used to determine whether the approaching wind will be warmer or more humid, whether it's coming from the Pole or from the continent. If we find an area with higher atmospheric pressure on the isobar map, an "A" is placed, indicating an anticyclone. This is an area of great atmospheric stability, since the air movement is downward and avoid the formation of cloudiness. Therefore, in this type of situation it is very difficult for it to rain.
On the contrary, if the pressure begins to decrease, at the point where the value reaches the minimum a "B" will be placed and it is said that there is a zone of low pressures. In this case there will be greater atmospheric instability and there will be more conditions for rain to form. When the low pressure zone is accompanied by rainier weather and stronger winds, it is called storm.
Rain maps and fronts
Storm
In the fronts are also shown that are formed when air masses, both cold and warm, meet and give rise to heavy rain. In the Northern Hemisphere, in an anticyclone, the wind turns following the isobars Clockwise and with a tendency to move away from the center. We have to remember that the wind will always move to the areas where there is less atmospheric pressure.
On the other hand, in a low pressure area, the wind is moving counterclockwise and heads towards the center of low pressures.
When you want to represent fronts in precipitation maps, isobars are used to indicate the direction and if the front is warm or cold. Cold fronts are represented by small triangles and warm ones by semicircles united to a line that covers the entire region that will occupy the front.
A front is nothing more than a large area of atmospheric instability where two air masses that are at different temperatures meet. If the cold air mass reaches an area where the temperature is higher, a cold front forms. When this happens, general temperatures drop and precipitation often occurs in the form of rain or snow. On the contrary, if the air mass reaches an area with a higher temperature, a warm front will form. In this case, cloudiness will also form, but the temperatures will be milder and the rainfall will be scarce.
Other precipitation maps
To understand the weather, meteorologists can not only look at the , but also observe other important meteorological variables. For example, another type of map used is the upper-air weather map. called isohipsas or geopotential maps. Isohipsas are lines that connect points that are located at the same height and that are at a certain level of atmospheric pressure. These lines are closely related to the temperature of the air in the layers of the atmosphere. At about 5.000 meters of altitude, the atmospheric pressure is 500 hPa.
As mentioned on other occasions, the warm air, being less dense it tends to rise. When this happens and in the higher layers of the atmosphere it encounters a very cold air mass, vertical air movements will occur that will cause instability situations in which there could be precipitation.
These situations of atmospheric instability occur when the map of isohipsas shows a trough or lower geopotential values. On the other hand, if the geopotential values are higher and the isohipsas form a ridge, It is a situation in which the air in height is at higher temperatures and, therefore, the meteorological situation is more stable and it would be unlikely that there would be precipitation.
NASA and the global rainfall map
In 2015, NASA released a global precipitation map that is updated every three hours and shows the entire rainfall pattern on a global scale and in real time. This rainfall map allows scientists to more accurately understand how storms and winds progress in all areas of the world. This type of rainfall map is essential to understanding the climate.
Here is a small section of how the NASA rain map works:
As you can see, rain maps are a very important component in weather forecasting in meteorology.
Hello, good morning Germán Protillo, I found your contribution to the Rain Maps very important, my question is: In which variable is it more advisable to read the atmospheric pressure (hectopascals or millibars). Cheers
Hi, the measurement most used by meteorologists and physicists is that of millibars.
Thank you very much for your comment, greetings!