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
Static pressure to the atmospheric pressure at the altitude at which the aircraft is flying, across the operating range of weight and airspeed. Many authors describe the atmospheric pressure at the altitude at which the aircraft is flying as the "freestream static pressure". At least one author takes a different approach in order to avoid a need for the expression "freestream static pressure". Gracey has written "The static pressure is the atmospheric pressure at the flight level of the aircraft". Gracey then refers to the air pressure at any point close to the aircraft as the "local static pressure". The concept of