Diabatic wind speed profiles in coastal regions: Comparison of an internal boundary layer (IBL) model with observations

Abstract

A model is presented to transform wind speed observations at a single height over sea or near the coast to any possible location and height in a topographic flat coastal region (up to distances of about 5 km from the coast and up to heights of IO0 m). Only moderate and strong winds from the sea are considered, which are particularly important for wind energy applications. The model, called 'diabatic coast model', which is based on the well known internal boundary layer (IBL) concept and Monin-Obukhov similarity theory, describes the effects of the roughness transition from sea to land as well as the effect of stability on the shape of the profiles and the IBL growth. The predicted IBL heights are compared with published data.In the second part of this paper, the model is compared with measurements taken at the Maasvlakte location near the Dutch coast. It is shown that a neutral formulation of the IBL height is sufficient to model the overall mean wind speed with height, but that stability corrections are needed to describe the diurnal variations in wind speed properly. Finally, an application is given, where a single routine wind speed observation at the coast, combined with air-water temperature differences is used to predict the wind speed at 500m from the coast at heights of 10 and 53 m. The results are in good agreement with the measurements.

Small‐scale orographic gravity wave drag in stable boundary layers and its impact on synoptic systems and near‐surface meteorology

“…The latter is responsible for the cyclonic filling due to vertical wind and ventilation on the ABL top (Beare, ). Beljaars and Viterbo () showed that, in order to have good score for cyclonic filling, an enhanced mixing function was necessary. Contrary to their results, we show that the new GWDSBL parametrization is able to accurately reproduce the CCP of cyclones due to enhanced momentum drag from gravity wave dissipation within the SBL.…”

“…The near‐surface temperature in the SBL depends on the amount of diffusion that we represent in each scheme. Beljaars and Viterbo () showed that the enhanced mixing functions, similar to the mixing function of our LT set‐up, have higher near‐surface temperatures than traditional ST mixing functions due to enhanced mixing. This results in a smaller negative bias in the 2 m temperature for LT mixing functions.…”

“…The main problem originates from the parametrization of subgrid‐scale processes that are not well understood and difficult to represent (Walsh et al , ; Kleczek et al , ). The interdependencies between these processes and their complexity inhibit the development of a robust and widely accepted parametrization of the SBL (Beljaars and Holtslag, ; Beljaars and Viterbo, ).…”

“…However, models applying this ST formulation usually lack sufficient cyclonic filling and do not accurately represent the development of cyclones over land (Louis, ; Holtslag, ). Beljaars and Viterbo () showed that under very stable conditions ST schemes also have a significant temperature bias that occurs due to runaway cooling at the surface. The runaway cooling is a result of the unrealistic decoupling of the SBL from the surface layer due to insufficient mixing (Sandu et al , ).…”

Interaction between heterogeneous thermal stratification and wakes of wind turbine arrays

“…This is often caused by heterogeneity in surface roughness, the effect of which is discussed in terms of the morphology of the land use condition 4–7 . In addition, thermal heterogeneity often arises owing to differing surface albedo and heat capacities at the land–sea interface 8–15 . This has occasionally been a focal WT issue under stably stratified conditions in the northwestern European region 13,14 .…”