Dust aerosols: A possible accelerant for an increasingly arid climate in North China

Results integrated from several data sources such as the vertical distribution characteristics of dust aerosols detected by aircraft, optical particle counter and Lidar measurements in the troposphere, dust devils, dry heat convection, and cloud parameter characteristics monitored by satellites, allow the identification of a new upwards dust transport mechanism. During non-dust storm periods, fine dust particles can be firstly carried into the atmosphere about 10–200 m by dust devils. Next, they can be carried to the height of the boundary layer at about 1000–6000 m by strong dry heat convection, so that a well-mixed dust layer dominates, which may even develop an elevated dust layer over the desert in the warm and sunny season. These processes lead to high dust aerosol concentrations in the desert troposphere, which results in an increase of condensation nuclei in clouds, a decrease of the effective radius of cloud droplets, and thus the formation of precipitation is suppressed. This paper develops a mechanism of positive feedback, which follows the following sequence: dust aerosol increases—effective radius of cloud droplet decreases—precipitation decreases—arid climate is strengthened. This new mechanism is a distinct factor in the development of an arid climate, especially desert in North China, and gradually becomes one of the most important factors maintaining an arid climate in North China. The positive feedback can accelerate desertification in this area.