High pressure weather systems are cold and dry moving masses of air molecules in the atmosphere. A high pressure system forms when dense air comes into contact with an area of low pressure (less dense molecules of air). A pressure system is a mass of air that rises (low pressure) or sinks (high pressure). The differences in air pressure from one area to another produces winds. Wind flows from areas of high air pressure to areas of low air pressure. A high pressure system is usually associated with good, clear weather.
The Earth’s weather changes globally due to differences in the atmosphere’s temperature. The distribution of heat energy around the world creates high and low pressure systems. Wind travels from high air pressure to areas of low air pressure. High pressure weather systems are associated with light surface winds and sinking air at the lower portion of the troposphere. The sinking air dries out and compresses a mass of air below, clearing the skies and bringing good weather. Low pressure weather systems are masses of warm air that tend to rise and as they rise, they cool and condense into clouds, creating cloudy days and precipitation.
Formation of high pressure weather systems
Polar air masses usually create vertically high pressure systems that move from higher to lower latitudes in the northern hemisphere. High pressure weather systems that travel southward usually bring clear weather due being cooled at the base, which prevents the formation of clouds. A high pressure system may form by subsidence, which means that a sinking parcel of air will compress and warm by 10 °C (50 °F) for every 1000 meters (3,289 ft.) that it descends towards the earth’s surface. The compressing and warming of a descending parcel of air causes evaporation of liquid water droplets, consequently, producing no clouds.
During clear days, the absence of clouds allows the incoming of solar radiation, leading to higher temperatures during the day. At night, the absence of clouds permit the free travel of heat energy in the form of infrared radiation out into the sky, leading to colder nighttime temperatures. Humidity is typically lower at or near a high pressure weather system. Low humidity contributes to good weather. Desert region around the world are closely related to high pressure weather systems. The drier air stimulates the creation of the desert environment.
Low and high pressure systems
A high pressure system is a mass of air that is dry and cold. Winds inside a high pressure system flow outward from the center of the system in a clockwise direction. The air moving out from the center of the high pressure system leaves an empty space that needs to be filled. Thus, the air above sinks and as it sinks, it compresses and warms, evaporating water droplets and bringing about clear skies. A low pressure weather system is characterized by a lower atmospheric pressure than that of the surrounding area. Low pressure systems form at areas of wind divergence in the upper layer of the troposphere. Wind divergence produce air lifts below, lowering surface air pressures as the upward motion counteracts the force of gravity.
High and low pressure weather systems originate due to the interaction of temperature variations in the environment, such as those found in the atmosphere, between the atmosphere and bodies of water, including lakes, rivers and oceans and the radiation energy received from the sun in a given region. Pressure systems cause the weather experienced regionally around the world. Low pressure systems are related to cloudy days and precipitation, whereas high pressure systems are associated with dry weather and clear skies, and extreme temperature variations during the day and night.