The Influence of Cloud-Base Temperature and Pressure on Droplet Concentration

Abstract

Cloud-base temperature is an important, but often neglected, parameter in the activation of cloud drops. Other factors being equal, clouds with colder bases will activate more condensation nuclei than clouds having warmer bases. In a typical case, a decrease in cloud base temperature from +10°C to ?10°C will result in approximately a one-third increase in the drop concentration. Variations in cloud base pressure, on the other hand, are relatively unimportant. The primary tool used in this evaluation is a detailed model of droplet activation and condensational growth which is significantly more efficient than previously reported models of this type. In addition, Squires? analytical expression for drop concentration is recast to permit direct evaluation of the influence of temperature and pressure.