Atmospheric pressure, also referred to as barometric pressure, is the force exerted against the surface of the earth by the weight of the air above it. Pressure is affected by a variety of factors including Air Temperature, Altitude, and Humidity. It plays an integral role in several other meteorologic processes available to be modeled in HEC-HMS including Evapotranspiration, Relative Humidity, Longwave Radiation, and Snowmelt.
In HEC-HMS, the Pressure Method is a required component of the Meteorologic Model when certain types of Evapotranspiration Methods or Longwave Radiation Methods are selected. The types of Pressure Methods currently available include Gridded Pressure, Specified Barograph, Interpolated Pressure, and Barometric Pressure.