Dynamical Response of an Arctic Mixed-Phase Cloud to Ice Precipitation and Downwelling Longwave Radiation From an Upper-Level Cloud

Multilayered, mixed-phase clouds are frequently present in the Arctic atmosphere. The upper-level clouds can impact the lower-level clouds through seeding with ice precipitation and reducing their cloud top radiative cooling rate. The Regional Atmospheric Modeling System is used to study the response of the lower-level clouds to the perturbations introduced by the upper-level clouds through the aforementioned mechanisms. The results show that both ice-seeding and downwelling longwave radiation from the upper-level clouds contribute to the dissipation of the lower-level clouds. With the reduction of liquid in the lower-level cloud, differential heating between the region directly perturbed by the upper-level cloud and the adjacent region drives a circulation in and below the lower-level cloud and dissipates the liquid in the lower-level cloud beyond the directly perturbed region. The broad updraft formed in the perturbed region as the liquid layer in the low-level cloud dissipates can lead to the re-formation of a liquid cloud layer in the center of the gap if the perturbations weaken, the results of which is to reduce the magnitude of the differential heating and limit the significance of this response. However, even with this re-formation, the warm air in the gap lowers the cloud top height and reduces the liquid water path of nearby clouds and potentially changes their radiative effects.