In meteorology, any chart or map on which data and analyses are presented that describe the state of the atmosphere over a large area at a given moment in time. The possible variety of such charts is almost limitless, but in meteorological history there has been a more or less standard set of synoptic charts, including surface charts and the constant- pressure charts of the upper air. Other synoptic charts include isentropic charts and constant- height charts, both used for upper-air analysis. There are a number of auxiliary and special- purpose synoptic charts, including thickness charts, tropopause charts, stability charts, change charts, continuity charts, etc. , that have useful applications for preparing forecasts of weather events at various locations. See also mean chart, prognostic chart, cross section, profile.