Boundary layer structure during ASCOS – Multi-sensor retrievals and diagnostics

The atmospheric boundary layer play a direct role in controlling the spatial and temporal distribution of low level clouds, their macrophysical structure and microphysical properties. Over the central Arctic numerical models have difficulty representing both the atmospheric boundary layer structure and clouds within it. The Arctic Summer Cloud Ocean Study (ASCOS) project was designed to study the many interacting processes that govern the properties of Arctic clouds, including boundary layer mean and turbulent structure. Here we present details of the vertical structure of the boundary layer during the ASCOS field campaign. For much of the campaign a persistent deck of stratiform clouds was present with cloud top below approximately 1500 m. A well mixed layer was usually maintained from cloud top to some distance below cloud base. This was frequently decoupled from a well mixed surface-based layer by a shallow stable layer at an altitude of the order of 100-200m. At other times mixing extended throughout the boundary layer from the surface through cloud. A combination of remote sensing measurements including SODAR, a radar wind profiler, cloud radar, and scanning microwave radiometer, are used to derive boundary layer diagnostics and estimate the vertical extent of mixing over time.