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

Abstract

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.

How frequent is natural cloud seeding from ice cloud layers ( < −35 °C) over Switzerland?

“…The simplest explanation for the increased frequency of multi-layer clouds in winter measurements is simply an increased cloud cover in winter. To see whether this is a robust finding, it was tested with the CALIPSO -GCM Oriented Cloud Calipso Product (GOCCP) dataset (Chepfer et al, 2010(Chepfer et al, , 2013. With a comparison of frac_cov from DARDAR vs. CALIPSO cloud cover data (Fig.…”

“…The dynamic viscosity µ can be derived from Sutherland's formula (Chapman and Cowling, 1960, Eq. 12.32.2), which can be rewritten and expanded to (Chepfer et al, 2010(Chepfer et al, , 2013. For the DARDAR data, the cloud cover was calculated as the mean (over all tracks within 2006-2017) of the sum of all fractions of sky covered (sum of frac_cov at all temperatures) at each grid point.…”

Insights on sources and formation mechanisms of liquid-bearing clouds over MOSAiC examined from a Lagrangian framework

“…By the same token, scarcity of such open water effects could explain the relatively small numbers of overlying cloud layers and multilayer cases in general in the high sea-ice cover Cluster 4 (Figure 1b and c). However, the complexity of multilayer cloud dynamical and radiative interactions, especially in the case of the commonly occurring Arctic mixed-phase clouds (e.g., Verlinde et al, 2013;Chen et al, 2020), further complicates the examination of these potential sources, and hence, likely requires case-by-case analyses that are beyond the scope of this study.…”