Daily variation in the temperature of the cytherean atmosphere is discussed, based upon the radiation equilibrium condition. A coupling of two systems of day side and night side is the main interest.
According to the rotation of the planet, energy influx from the sun varies sinusoidally with time. However, variations in the radiation equilibrium temperature are not always sinusoidal, and a discontinuous jump at 350°K and 250°K is expected.
Wind of hot gas from the day side to the night side occurs continuously, and a temperature rise of 30°K is realized at the night side.
