摘要：This study investigates the effect of the droplet activation process on microphysical characteristics
of warm clouds represented by correlation statistics between cloud droplet effective radius
re and cloud optical
thickness τc. The conceptual adiabatic model is first employed to interpret satellite-observed
re–τc correlation statistics over two different regions and to reveal distinctively different
increasing patterns of droplet number concentration between these regions. This
difference is attributed to a different behavior of the droplet activation process
induced by differing microphysical conditions of aerosols. Numerical experiments of
changing aerosol size spectrum are then performed with a spectral bin microphysics
cloud model. The results show that the slope of the size spectrum controls the
re–τc relationship through its effect on increasing pattern of droplet number concentration due to
the activation process. The simulated results are also found to reproduce the
re–τc correlation statistics closely resembling those observed when the slope parameter
and the aerosol amount are appropriately chosen. These results suggest that the
re–τc correlation statistics observed by remote sensing studies contains a signature of how the
droplet activation process takes place in the real clouds.
