Shallow Gully Flow

An array of 2-D sonic anemometers, thermistors and thermocouples and a 5 m tower with eddy correlation measurements were deployed in a gully in South Central Kansas during the CASES99. The data shows a weak gully flow of a few tens of cm/s and a depth of a few meters developing in the early evening on many of the nights. The gully flow is generally eliminated after a few hours in conjunction with formation of a low level jet and downward mixing of warmer air and higher momentum. The gully flow may reform later in the night.

Even though the gully flow is thin and weak, it decouples the surface from standard observational levels. Under such conditions, standard eddy correlation flux measurements cannot be used to estimate surface fluxes. The gentle gully system in this field program is typical of much of the Earth's land surface.