Air temperature lapse rate

Air temperature decreases with elevation. MIKE SHE assumes that this decrease is linear with the elevation. However, the lapse rate depends on the relative humidity. So, MIKE SHE includes two different lapse rates - one for dry conditions and the other for wet conditions (i.e. when it is raining or snow­ing). The exact formulae are shown in Equations(22.1) and (22.2). Wet condi­tions are defined as any time step were the precipitation rate is greater than zero.

Note Air temperatures are specified as instantaneous values. Thus, for air temperature time series, an average air temperature is used in each time step based on a linear interpolation between two instantaneous values.