A Generalized Bulk Parameterization Approach for Land-Atmosphere Heat Fluxes

Standard bulk parameterization approaches for scalar fluxes and stress components employ measurements of a vertical gradient and a transfer coefficient to parameterize the vertical fluxes. Although the traditional approach is a very effective gap filling method and a diagnostic tool, in practice the transfer coefficient values are strongly dependent on atmospheric boundary layer stabilities and local surface characteristics.

Here, we introduce a bulk parameterization approach for sensible heat fluxes measured over the land without a site and stability dependent transfer coefficient. The bulk sensible heat fluxes are parameterized as functions of vertical velocity variance and temperature gradient between the surface and atmosphere. The atmospheric stability dependence is contained in the vertical wind variance. The vertical wind variance is parameterized as a function of the measured bulk richardson number. The functional dependence is shown to be consistent across sites with differing vegetation and surface characteristics. The local surface characteristics information is contained in the measured surface temperature values. Accurate surface skin temperatures were measured with downward pointing infrared thermal sensors, corrected for local and time-evolving emissivities.

Our findings provide credence for implementing such a non-iterative parameterization for surface fluxes and turbulence statistics into land-surface models for representing surface-atmospheric exchanges.