Abstract:
The Thermal Internal Boundary Layer (TIBL) is a mesoscale feature of the coastal atmosphere that forms over the land during conditions of onshore flow. This study employs both airborne and surface measurements to obtain a comprehensive spatial and temporal data set, in order to elucidate aspects of the characteristic structure and behaviour of the TIBL. TIBL growth has been found to follow a diurnal pattern. The TIBL is associated with a layer of uniform wind speed and direction flowing perpendicular to the coastline, within which warmer temperatures and changes in relative humidity and moisture content have been observed. The temperature structure of the onshore flow strongly influences the intensity of turbulence encountered in the TIBL. Patterns of turbulent properties display significant increases in the TIBL. Measurements of sensible heat flux reveal strong undulations in TIBL structure due to transitory eddies and thermal upcurrents. Certain theoretically based predictive equations display the best overall performance out of eight selected models, and some promise has been shown by an empirical formulation. TIBL development is generally complex and irregular within the first few kilometres of the shore, while further inland more regular TIBL formation enables the relatively accurate observation and prediction of TIBL height.
