Dynamics of evaporation from saline water bodies

The sensitivity of evaporation from saline solutions resulting from a variation in their salinity/activity coefficients (beta) is investigated The calculations are based on a theoretically derived parameter (gamma = partial derivativeT/partial derivative beta), which accounts for the temperature change following a departure in the salinity/activity coefficient. Results reveal that gamma is a function of saline temperature. the level of the activity coefficient, and the transfer coefficients for water vapor and sensible heat. For a transfer coefficient of 15 W m (-2) kPa(-1). gamma ranges from approximate to -6 K for a saline temperature of 5 degreesC and activity coefficient of 0.95 to approximate to -27 K for a saline temperature of 40 degreesC and activity coefficient of 0.4, The present formulation provides a robust method that can be used to identify lower and upper theoretical limits for the variations of saline temperatures, and also to derive the departures of the activity coefficient and evaporation rates for saline solutions from routine meteorological observations only. Calculations with the Penman equation reveal that the aerodynamic term is the most sensitive parameter influencing evaporation from saline solutions following a departure in their salinity/activity coefficients. with a contribution ranging from approximate to 50%-65% of total annual evaporation departure. Alterations to net radiation following a variation in beta accounts for a contribution of about 25% of total annual change in evaporation.