Radiative Time Constant

z

Harshvardan and Cess (1976, Tellus 28 p.1-10) give a value for Earth CO₂ of / z = -0.0081 per Km and Cess and Khetan (1973, JQSRT 13 p.995-1009) give a value for Jupiter, Saturn, Neptune, and Uranus of / z = -0.0068, -0.0063, -0.0061, and -0.0058 per Km, respectively.

The phase shift, , is the seasonal lag due to the radiative time constant. It arises from the 1st Fourier moment of the thermal response. A value of =90° indicates a full seasonal shift ( e.g., the warm maximum expected at the summer solstice would occur at the autumnal equinox).

where _o is the orbital period. For = 0.3 the values are: