Computing turbulent fluxes near the surface: Needed improvements

With the recognition that eddy flux measurements are relatively accurate for a variety of common situations, a number of issues leading to inaccurate flux estimates and/or ambiguous interpretation of flux values are surveyed. These issues include inadvertent conversion of random errors to systematic errors, ambiguous differentiation between turbulence and other motions, and omission of transport by stationary eddies. Correcting for sonic misalignment and flow distortion in the presence of real systematic vertical motions is also problematic. Special emphasis is placed on the need for spatial information, partly to include vertical transport by stationary circulations induced by small-scale surface features. While no categorical solutions to the above problems are offered, promising approaches worthy of more investigation are discussed.