摘要：Cloud anvils from deep convective clouds are of great importance to the radiative energy
budget and the aerosol impact on them is poorly understood. In this study, we use a
three-dimensional cloud-resolving model with size-resolved cloud microphysics to examine
the effects of both cloud condensation nuclei (CCN) and ice nuclei (IN) on cloud anvil
properties and water vapor content (WVC) in the tropical tropopause layer (TTL). We find
that cloud microphysical changes induced by increases in CCN/IN play a very important
role in determining cloud anvil area and WVC in the TTL, whether convection is
enhanced or suppressed. Also, CCN effects on anvil microphysical properties, anvil
size and lifetime are much more evident relative to IN effects. Our sensitivity
study shows that IN have little effect on convective strength but can increase
ice number and mass concentrations in cloud anvils significantly under humid
conditions. CCN in the planetary boundary layer (PBL) are found to have greater
effects on convective strength and mid-tropospheric CCN have negligible effects on
convection strength and cloud properties. Convective transport may only moisten the
main convective outflow region, and the larger cloud anvil area and more efficient
sublimation induced by increasing CCN concentration significantly increase the WVC
in the whole TTL domain. This study shows an important role of CCN in the
lower troposphere in modifying convection and the upper-level cloud properties. It
also shows that the effects of IN and the PBL CCN on the upper-level clouds
depend on the humidity, resolving some contradictory results in past studies.
