High-pressure area are alternatively referred to as anticyclones. On English-language weather maps, high-pressure centers are identified by the letter H in English, within the isobar with the highest pressure value. On constant pressure upper level charts, it is located within the highest height line contour. Highs are frequently associated with light winds at the surface and subsidence through the lower portion of 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
Contour line isotherms in Paris, in 1817. An isogeotherm is a line of equal mean annual temperature. An isocheim is a line of equal mean winter temperature, and an isothere is a line of equal mean summer temperature. An isohel (from or "helios", meaning 'Sun') is a line of equal or constant solar radiation. An isohyet or isohyetal line (from or "huetos", meaning 'rain') is a line joining points of equal rainfall on a map in a given period . A map with isohyets is called an isohyetal map. An isohume is a line of constant relative humidity, while a isodrosotherm (from