Transport in Stable Conditions with Typical Low Amplitude Terrain

Transport in very stable conditions is complex and analysis of eddy flux data for such conditions requires extra care. A number of analysis issues that can lead to poorly estimated fluxes are discussed. These issues include the choice of averaging time, tilt rotation and treatment of outliers.

The shear generation of turbulence in very stable weak-wind conditions results partly from propagating transient modes and from terrain induced circulations. Even very weak slopes can generate local circulations with weak large-scale flow. This topo-transient mix of motions often transports trace gases over a wide range of wind directions, even within a short interval of time. In contrast to the existing literature based primarily on well defined topographical features, more complex small amplitude terrain is emphasized, typical of most of the Earth's surface. Such an investigation must allow for a more flexible concept of the cold pool and downvalley cold air drainage. Such flexibility includes diffuse tops of the cold pool and intermittent behavior of the cold pool and both horizontal and vertical transport.