Abstract
Virtual temperature of the second kind Tυυ is difined by Tυυ=T g/g-2ωcosφu where, g, ω, φ, u are gravity acceleration, angular velocity of rotation of the earth, latitude and zonal velocity components taken positively to the east respectively. In Linke's Meteorologische Taschenbuch, the differences between Tυυ and T is tabulated but the formal definition is not given. The above definition is given by the auther taking accounts of various points of view. This may be probably identical with that given by Linke. Tυυ-Tυ, is very small quantity and negligible in many cases, but in the neighbourhood of the horizontal front, the gradient of Tυυ-T becomes important. If we introduce virtual polytropic potential temperature of the second kind of class k defined by the criterion of vertical stability obtained by the author becomes
