An Aircraft Investigation of a Convective Boundary Layer Over Lake Michigan
Abstract
Meteorological data from research flights have been used to study the structure of a Type I Cloud-Topped Boundary Layer (CTBL) that formed as a result of air mass modification by a Cold Air Outbreak (CAO) over Lake Michigan on 10 January 1984. Surface and upper air data were used as a source of information to describe the synoptic scale conditions that accompanied the CAO event. Vertical cross-sections of the CTBL were constructed using the aircraft data and assuming a steady-state in the north-south direction (parallel to the cloud streets) during the 1 hour and 50 minute time period covered by the flights. The cross- sections show a complex CTBL structure with off-shore flow from both Wisconsin and Michigan imposing lateral boundary conditions on the convection. Spectral representations of the convective well-mixed boundary layer contained length scales of approximately 3, 10, and 30 km. These length scales correspond to the basic convective mode (BCM), a higher convective mode (HCM) which relates to organization within the 2-D cloud streets, and the length scale associated with Mesoscale Cellular Convection (MCC). The temperature, specific humidity, and vertical velocity spectra also indicated the presence of strong turbulence in the lower CTBL. This turbulence is a result of strong thermal forcing caused by a large temperature difference between lake and atmosphere. The temperature spectra also showed evidence of turbulence at the top of the CTBL, where turbulent mixing between the boundary layer and inversion takes place. Theses.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1989
- Accession Number
- ADA218175
Entities
People
- Mary L. Hart
Organizations
- Air Force Institute of Technology