High-pressure area 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 widespread haze. If the low level relative humidity rises towards 100 percent overnight, fog can form. Strong, vertically shallow high-pressure systems moving from higher latitudes to lower latitudes in the northern hemisphere are associated with continental arctic air masses. Once
Coronary perfusion pressure Coronary perfusion pressure Coronary perfusion pressure (CPP), also known as simply perfusion pressure, refers to the pressure gradient that drives coronary blood pressure, meaning the difference between the diastolic aortic pressure and the right atrium end diastolic pressure. It is a term used mainly in research concerning cardiac arrest. In this context, it is assumed that the minimum CPP needed for a successful outcome is 15mm Hg. CPP is a part of normal blood pressure that is specifically responsible for coronary blood flow. CPP is also, generally, a surrogate term for coronary blood flow. During cardiac arrest, CPP is one