Scaling surface drag in the atmospheric boundary layer using laboratory concepts

The work demonstrates how the drag scaling from laboratory Turbulent Boundary Layers (TBLs) can be extended to scale the drag or surface friction velocity in near-neutral and convective Atmospheric Boundary Layers (ABLs). Here, The estimation of surface drag in ABLs is enabled solely from the Radiosonde measured wind speed profiles. For this, The model presented in Dixit et al. (2020) for laboratory TLBs (i.e., the non-conductive NC model) is modified to compensate for convection effects using the convective velocity scale

and the ABL bulk velocity scale. This modified convective model (i.e., the C model) is able to estimate the drag to within a 20% error band with a probability of 80%, which is remarkable given the inherent uncertainty of ±20% for the measured drag values. The benefit of this new model is that it requires only the Radiosonde profile data for the estimation of surface drag. These results are applicable to convective and near-neutral atmospheric conditions and could be of immense importance for data assimilation where Radiosonde profiles are available, but the surface fluxes are not known due to the unavailability of costly fast-response tower instrumentation.