Abstract
AbstractIn order to improve the simulation accuracy, it is effective to use a data assimilation technique which is capable of reproducing more realistic simulated states by incorporating observational data into simulation models. One of the simplest ones among data assimilation techniques is a Newtonian relaxation‐type nudging method which has been widely used in mesoscale meteorological models. In this study, we proposed a data assimilation method using a vibration equation which can incorporate turbulence winds toward target mean winds while maintaining small‐scale turbulent fluctuations as a different approach from the conventional nudging method. First, we conducted test simulations in which nudging is applied in a basic turbulent boundary layer (TBL) flow toward a target one. It is shown that the basic TBL flow can be reasonably nudged toward the target one while maintaining the turbulent fluctuations well when prescribing the natural frequency in the vibration equation smaller than the spectral peak frequency in the TBL flow. Then, we applied the proposed nudging method by incorporating data obtained from meteorological observations located in the actual city of Kyoto. The mean wind velocity profiles were reasonably nudged toward the target observed profile and the turbulence statistics were also favorably maintained. It is concluded that the data assimilation method using the vibration equation successfully nudges toward the target mean winds while maintaining small‐scale turbulent fluctuations well.
Highlights
The Engineering Science Data Unit (ESDU) provides comprehensive turbulence characteristics of a neutrally stratified atmospheric boundary layer (ABL) based on independent experimental measurements ranging from the ground surface to 300 m, including the vertical profiles of turbulence intensities and their relationships depending on surface roughness
It is found that for a case of the natural frequency larger than the spectral peak one of the background turbulence, the turbulent fluctuations are rapidly damped at downstream positions from the nudging area the mean wind profile matches with the target one at the nudging area
For a case of the natural frequency smaller than the spectral peak one of the background turbulence, the mean wind profile is reasonably nudged toward the target one at the nudging area while maintaining the turbulent fluctuations well
Summary
The ground surface is heated by solar radiation, and turbulence is mainly produced by positive buoyancy, which induces boundary layer convective motions. This type of the atmospheric boundary layer (ABL) is called as convective boundary layer (CBL). The ground surface is cooled by outgoing long‐wave radiation, and turbulence is constrained by negative buoyancy, which forces turbulent motions more inactive and leads to stable stratification. This type is called as stable boundary layer (SBL). In the RS above the IS, the vertical variation of the shear stress may be neglected and the wind direction is assumed to be constant with
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
