Thermal Remote Sens Ing of Atmospheric Boundary Layer Structures over Homogeneous Surfaces

A series of parallel striations observed on thermal satellite images over flat terrain in arid West Africa is identified as helical roll vortices in the Atmospheric Boundary Layer (ABL). This is because their length and spacing conforms to the dimensions expected for such roll structures according to climatic conditions at the time of the image. Knowledge of helical roll vortices is usually derived from vertical temperature and wind profiles and radar reflectivity fields over time, whereas the image data presented here permit visualisation of the horizontal component, and thus examination of their interaction with surface phenomena. Distinct and coherent localised patterns are also observed on a LANDSAT TM thermal image over open water in the Straits of Singapore, and while their origin cannot be identified, such features call for image-based atmospheric correction algorithms since radiosonde data do not account for such localised effects.