Turbulent Exchange Coefficients for Sensible Heat and Water Vapor under Advective Conditions

Abstract

Results are presented of niicronicteorological measurements made over alfalfa and soybeans under conditions of sensible heat advection at Mead, Ned. The exchange coefficient for sensible heat (Kh) is found to be generally greater than the exchange coefficient for water vapor (Kw). This result contradicts the usual assumption of equality of Kh and Kw under nonadvection (Iapse or unstable) conditions when the net transfer of both sensible heat and water vapor are away from the earth's surface. Under advective conditons, however, heat and water vapour are transferred in opposite directions. Our results are supported by Warhaft's (1976) recently published theoretical analysis in which he concludes that the greatest departure of Kh/Kw from unity will occur when temperature and humidity gradients are of opposite sign.