Maybe you often look at the weather report on TV or on your smartphone. If so, you have certainly come across the terms Azores high or Icelandic low at one point or another.
It is about high and low pressure areas. They influence the weather and are part of the global wind system.
High and low pressure areas – explanation
Do you speak of high and low pressure areasn, the air pressures in a certain area are meant.
Under air pressure is the force that air exerts due to gravity.
The normal value of air pressure in the atmosphere is at 1013.25 hectopascalshPa for short, or 1 bar.
If you want to learn more about air pressure and the atmosphere, you should look at the appropriate explanations.
high pressure
If the air pressure is over 1013.25 hPa, the air pressure is high. It’s also called high pressure.
If high pressures prevail over a certain observed area, one speaks of one anticyclone.
A anticyclone is a zone or region where an air pressure above 1013.25 hPa can be measured.
In weather maps you can recognize high pressure areas by a capital H.
An example is this subtropical high at latitudes around 30°. This high pressure area is related to the trade wind cycle together.
gravure
If the air pressure is below 1013.25 hPa, the pressure is low – too gravure called.
If lower pressures prevail over an area, this is also called depression. A low pressure area is the opposite of a high pressure area.
A depression is a zone where low air pressure below 1013.25 hPa can be measured.
The capital T on weather maps denotes low-pressure areas.
These are the most well-known low-pressure areas Iceland deep or the equatorial low-pressure trough at the equator. The latter is related to the subtropical high and the trade wind cycle.
Formation of high and low pressure areas
In the case of high and low pressure areas, between the thermal and the dynamic Pressure area differentiated.
A thermal pressure area caused by different air temperatures.
In contrast to this are the dynamic pressure areas.
at dynamic pressure areas are pressure areas created by atmospheric circulation.
the atmospheric circulation describes all global wind systems in the atmosphere.
You want to learn more about the atmospheric circulation? Please take a look at the relevant explanation. You will also find your own explanations of the wind systems and the atmosphere.
Formation of high pressure areas
High pressure areas occur when air accumulates at one point. As a result, the air particles are pressed together and the pressure increases.
So you can remember: Many air particles at one point lead to high pressure.
Thermal high pressure areas
Thermal high pressure areas occur when the air and the ground are affected by lower temperatures sun exposure cooling down. This causes the air to contract and the pressure between the individual air particles increases.
Cold air is denser than warm air. Due to the higher density, the air collects on the ground below, where a high pressure area then develops. An area of high pressure on the ground is called floor high.
In addition to the ground high, there is also that altitude high. The formation of a high altitude is accompanied by a high pressure area on the ground. If the air warms up, it rises and the high pressure area shifts upwards.
Mnemonic: When penguins are cold, they huddle together very closely. It is similar with air particles.
Dynamic high pressure areas
Dynamic high pressure areas are caused by the so-called jet streams.
jet streams are strong, tubular air currents that blow to the west.
Although these are very stable, they still meander. This means that they move in waves, much like a snake on the ground.
Would you like to find out more about jet streams? Please take a look at the relevant explanation.
Depending on the direction in which surface winds move, a dynamic high or low pressure area is created.
Move ground winds, i.e. winds that blow on the ground, circular and opposite to the direction of travel of the jet stream, dynamic high pressure areas arise. This movement of the surface winds is called anticyclonic. Therefore, dynamic anticyclones will also anticyclones called.
Jet streams are also called west winds, meaning they blow from west to east. When the surface wind is anticyclonic, it blows circularly towards the west. So clockwise.
Formation of low pressure areas
Low-pressure areas are created by the expansion and rise of air particles. Again, between thermal and dynamic differentiated from low-pressure areas.
So you can remember: A few air particles lead to a low pressure area.
Thermal low pressure areas
When the sun shines on the earth, the air expands and becomes lighter because warm air is less dense than cold air. The light air rises and therefore the air pressure on the ground decreases. This creates thermal low pressure areas on the ground, a so-called ground level.
As with the high pressure area, the low pressure areas also have a surface low and a high low. A high altitude low is also accompanied by a low ground. As the surface cools, the low-pressure area moves up, while the high-pressure area moves down below.
Dynamic low pressure areas
These types of low pressure areas are like too dynamic High pressure areas coupled to the jet streams. dynamic low pressure areas are caused by surface winds that move in a circle in the direction of travel of the jet stream.
This is why they are also called ground winds cyclonic ground winds. Due to the cyclonic movement of the surface winds, dynamic low pressure areas also become cyclones called.
Formation of high and low pressure areas – summarized
Here you will find a brief overview of the formation of high and low pressure areas.
- A distinction is made between thermal and dynamic pressure areas.
- Lots of air particles = high pressure = high pressure area
- Less air particles = lower pressure = low pressure area
- Warm air is less dense, rises and a thermal low pressure area forms on the ground.
- Cold air is dense, sinks and collects on the ground, creating a thermal high pressure area.
- If surface winds blow anticyclonic to the direction of movement of the jet streams, a dynamic high pressure area develops.
- Cyclonic surface winds lead to a dynamic depression.
Pressure areas at altitude and on the ground
High and low pressure areas want to balance each other out. The low-pressure area attracts air particles from the high-pressure area. The air moves from high pressure areas to low pressure areas. This air blowing between the two pressure areas is called wind.
Pressure areas can be at different altitudes. If there is a pressure area on the ground, it is called, depending on the air pressure, floor high or ground level. Conversely, pressure areas at altitude altitude high or high low called.
As the air warms up on the ground, it rises and the air pressure at altitude increases while the air pressure on the ground decreases. This creates ground level and altitude high. However, as the ground cools, air pressure increases at ground level and decreases at altitude because air particles sink downwards. A floor high and a high low develop.
High and low pressure areas – Europe
The weather situation in Europe is mainly due to the Azores higha dynamic anticyclone, and that Iceland deep, a dynamic low-pressure system. Because the location and the difference in air pressure between the two pressure areas determines whether there will be a cloudless sky or storms.
Dynamic pressure areas are shifted by the movement of the jet streams. You can imagine that the jet streams pull the pressure areas with them and thus change their position.
The Icelandic Low brings with it wet and unsettled weather. So when the low pressure area dominates, it rains more often and it is cloudy. Cold air can store less moisture, so it comes to condensation and cloud formation and precipitation occur.
During condensation, gaseous water in the atmosphere is converted into liquid water. You can then perceive this water as rain.
In contrast to the Icelandic low, the Azores high brings clear skies and sunshine. This is because warm air can hold more moisture, making clouds less likely to form.
The naming of high and low pressure areas has been rotated since 1997. This means that in even-numbered years, such as 1998, high pressure areas are given female names and low pressure areas are given male names. Conversely, in odd-numbered years, low-pressure areas are given a female name and high-pressure areas are given a male name.
Prior to 1997, low pressure areas were named female and high pressure areas male. However, with lows bringing bad weather, there have been protests over discrimination against women.
High and low pressure area – the most important
- Of the atmospheric air pressure is 1013.25 hectopascals.
- high pressure areas are areas with high air pressure above 1013.25 hectopascals. In contrast to this low pressure areas with low pressure below 1013.25 hectopascals.
- One distinguishes between thermal and dynamic pressure areas.
- thermal High and low pressure areas are created by one temperature difference in the air. dynamic High and low pressure areas originate in the jet streams.
- Iceland deep and Azores high are the most well-known pressure areas in Europe and are responsible for the weather, among other things.
proof
- dwd.de: high pressure area. (08/21/2022).
- dwd.de: Low pressure area. (08/21/2022).
- klima-der-erde.de: The general circulation of the earth. (08/21/2022).