Pressure system the troposphere. In general, subsidence will dry out an air mass by adiabatic or compressional heating. Thus, high pressure typically brings clear skies. During the day, since no clouds are present to reflect sunlight, there is more incoming shortwave solar radiation and temperatures rise. At night, the absence of clouds means that outgoing longwave radiation (i.e. heat energy from the surface) is not absorbed, giving cooler diurnal low temperatures in all seasons. When surface winds become light, the subsidence produced directly under a high-pressure system can lead to a buildup of particulates in urban areas under the ridge, leading to
Filtered Air Positive Pressure Filtered Air Positive Pressure A filtered air positive pressure environment in laboratory animal science is a space that is under positive pressure with respect to the outside world. In this way, no germs that could affect the lab animals or that are a threat to the SPF status can enter the facility. To bring in new air, high efficiency particulate air filters (HEPA) are used. In some facilities, the opposite is done: negative pressure inside prevents escape of germs to the outside world. This is done when the facility does research on dangerous germs like anthrax. Next to these obvious