High Pressure
Overview
High pressure (高氣壓, high pressure) refers to a region of the atmosphere in which the atmospheric pressure is higher than that of the surrounding areas. On surface weather charts it is usually shown as a closed curve with a central pressure higher than 1013 hPa (standard sea-level pressure), and at the center, descending air currents cause air to sink downward, so clouds rarely form and clear weather often appears. High pressure is not only a factor in everyday weather changes but also a key element determining the climate of the Korean Peninsula, including monsoons, heat waves, and cold waves.
Main Content
Definition of Atmospheric Pressure and the Criterion for High Pressure
Atmospheric pressure is the weight of the atmosphere acting on a unit area, expressed in hPa (hectopascals). Standard sea-level pressure is 1013.25 hPa; above this is classified as high pressure, and below it as low pressure. In actual weather analysis, however, the relative pressure difference from the surroundings and the shape of the isobars are considered more important than the absolute value. At the center of a high-pressure system, the isobars form concentric circles, and the pressure rises toward the center.
Causes of Formation and Atmospheric Circulation
High pressure is created in two main ways. The first is formation through cooling of the air. When air in contact with a cold surface is cooled and its density increases, the heavier air sinks downward, raising the pressure near the surface. The Siberian High is a representative example. The second is formation through convergence in the upper atmosphere. When air gathers in the upper troposphere, air is pushed down beneath it, raising the surface pressure. In addition, there are topographical effects, differences in the specific heat of oceans and continents, and the subtropical high-pressure belt formed as a result of the general atmospheric circulation.
Types of High Pressure
- Migratory high pressure: Moves from west to east along the westerlies; after it passes, temperatures drop and clear weather continues. It frequently appears in spring and autumn.
- Continental high pressure: Develops strongly inside the Eurasian continent in winter. The Siberian High is a representative example, bringing the northwesterly monsoon and cold waves to the Korean Peninsula.
- Maritime high pressure: Accompanies warm, humid air, as in the North Pacific High. In summer it supplies hot, humid air to the Korean Peninsula, causing heat waves and tropical nights.
- Subtropical high pressure: Formed permanently around latitude 30 degrees due to descending air currents, it is the cause of dry climate zones such as the Sahara Desert.
Characteristics of Weather and Wind
At the center of a high-pressure system, air descends and is adiabatically compressed, so the temperature rises and the relative humidity falls. As a result, clouds dissipate and clear, dry weather tends to appear. At the edges of a high-pressure system, on the other hand, winds blow strongly due to the pressure difference with surrounding low-pressure systems. In the Northern Hemisphere, because of the geostrophic wind and the Coriolis effect, winds blow outward clockwise around the center of the high; this is called the pressure wind or geostrophic wind. Also, when a high-pressure system stagnates, the atmosphere becomes stable, causing problems in which pollutants such as fine particulate matter cannot disperse and instead accumulate.
Representation on Weather Charts
On weather charts, the symbol 'H' is marked at the center of a high-pressure system, and the wider the spacing between isobars, the gentler the pressure gradient and the weaker the wind. When the isobars are closely packed, strong winds blow. The tracks and changes in strength of high-pressure systems are key prediction targets of numerical forecast models, and seasonal weather outlooks for the Korean Peninsula depend heavily on the contest of strength between the Siberian High and the North Pacific High.
Recent Trends
In 2024–2025, the strengthening and stagnation of high pressure due to climate change emerged as a major issue. In the summer of 2024, as the North Pacific High and the Tibetan High expanded simultaneously over the Korean Peninsula, heat waves and tropical nights continued for a long period, and the so-called "heat dome" phenomenon was repeatedly observed. A heat dome is a phenomenon in which an upper-level high-pressure system stagnates over a particular region and traps hot air; combined with the urban heat island effect, it greatly raises nighttime minimum temperatures.
Researchers are also presenting analyses showing that, due to warming, the strength of continental cold high-pressure systems is weakening, while instead the maritime subtropical high is advancing farther north toward the Korean Peninsula. This is cited as a factor that simultaneously increases changes in the pattern of winter cold waves and the variability of summer precipitation patterns. The Korea Meteorological Administration is introducing artificial-intelligence-based numerical forecast models to precisely predict the location and intensity of high-pressure systems, and it is strengthening a real-time analysis system that combines satellite, radar, and ocean observation data. Over the long term, research is actively under way to quantify the effects of changes in high-pressure tracks on heat waves, droughts, and fine particulate matter concentrations caused by atmospheric stagnation.
Related Topics
- [[Atmospheric Pressure]]
- [[Low Pressure]]
- [[Siberian High]]
- [[North Pacific High]]
- [[Weather Chart]]
- [[Heat Wave]]
- [[Fine Particulate Matter]]
- [[Climate Change]]
- [[Coriolis Effect]]