Air stagnation

Air mass remaining over an area for an extended period
Air stagnation is a meteorological condition that occurs when there is a lack of atmospheric movement, leading to the accumulation of pollutants and particles that can decline the air quality in a particular region. This condition typically correlates with air pollution and poor air quality due to the possible health risks it can cause to humans and the environment. Due to light winds and lack of precipitation, pollutants cannot be cleared from the air, either gaseous (such as ozone) or particulate (such as soot or dust).

Typically air stagnation events develop under warm high pressure systems, where conditions are stagnant and there is little vertical and horizontal air movement. When there is a stable atmospheric environment, pollutants are accumulated in areas near the surface. These meteorological conditions show how atmospheric circulation and precipitation patterns are correlated with air stagnation events. With the absence of rain, there is a reduced amount of atmospheric mixing and the build up of particulates continues. When substantial accumulations of smoke, dust, industrial emissions, or air pollution are predicted to occur close to the ground for a prolonged amount of time, the National Weather Service issues this product. In addition, spatial variations during winter and spring tend to be incoherent and there are less air stagnation event advisories. Poor air quality can also cause some symptoms such as difficulty breathing, coughing, and headaches. Typically pollutants irritate the respiratory system and trigger respiratory conditions such as asthma and chronic bronchitis that make it difficult for them to go outside. During air stagnation events, it is recommended for children, elders, and people with pre existing health conditions, to stay inside as much as possible and stay hydrated.