Using ARM data to explore post-cold-frontal clouds and their representation in models

Poster PDF

Description

Post-cold-frontal regions are dominated by strong subsidence and mostly populated by low-level clouds, mainly stratocumulus and cumulus clouds. Previous work suggests that the relationship between cloud cover and inversion strength is not dissimilar to subtropical regions in these dynamically more active regions. However, little is known on cloud properties, and it is unclear whether local or large-scale conditions impact not only cloud cover, but also liquid water path, thermodynamic phase, and microphysical properties. Using ASR observations from the Azores ARM site, we planned to explore the relationship between cloud properties in post-cold-frontal situations and the local and large-scale conditions. Preliminary data analysis will be presented, in the form of seasonal histograms, as well as climatological time series of cloud properties as a function of environmental parameters (e.g., temperature, humidity, winds). Additionally, it has been reported that climate and numerical weather prediction models have trouble representing the correct amount of clouds in post-cold-frontal conditions, and we intend to use the WRF model to test which parameterizations (boundary layer, cloud scheme, convection) are responsible for these problems and how they might be improved. Therefore, we will present the experimental set-up and preliminary results of these model runs for a specific frontal passage over the ARM site.