Wind field near complex terrain using numerical weather prediction model
by Kin-Sang Chim
Ph.D. Mechanical Engineering
v, 4, 230, 6 leaves : ill. ; 30 cm
The PennState/NCAR MM5 model was modified to simulate an idealized flow pass through a 3D obstacle in the Micro-Alpha Scale domain. The obstacle used were the idealized Gaussian obstacle and the real topography of Lantau Island of Hong Kong. The Froude number under study is ranged from 0.22 to 1.5. Regime diagrams for both the idealized Gaussian obstacle and Lantau island were constructed....[ Read more ]
The PennState/NCAR MM5 model was modified to simulate an idealized flow pass through a 3D obstacle in the Micro-Alpha Scale domain. The obstacle used were the idealized Gaussian obstacle and the real topography of Lantau Island of Hong Kong. The Froude number under study is ranged from 0.22 to 1.5. Regime diagrams for both the idealized Gaussian obstacle and Lantau island were constructed.
This work is divided into five parts. The first part is the problem definition and the literature review of the related publications. The second part briefly discuss as the PennState/NCAR MM5 model and a case study of long-range transport is included. The third part is devoted to the modification and the verification of the PennState/ NCAR MM5 model on the Micro-Alpha Scale domain. The implementation of the Orlanski(1976) open boundary condition is included with the method of single sounding initialization of the model. Moreover, an upper dissipative layer, Klemp and Lilly(1978), is implemented on the model. The simulated result is verified by the Automatic Weather Station(AWS) data and the Wind Profiler data. Four different types of Planetary Boundary Layer (PBL) parameterization schemes have been investigated in order to find out the most suitable one for Micro-Alpha Scale domain in terms of both accuracy and efficiency. Bulk Aerodynamic type of PBL parameterization scheme is found to be the most suitable PBL parameterization scheme. Investigation of the free-slip lower boundary condition is performed and the simulated result is compared with that with friction.
The fourth part is the use of the modified PennState/NCAR MM5 model for an idealized flow simulation. The idealized uniform flow used is nonhydrostatic and has constant Froude number. Sensitivity test is performed by varying the Froude number and the regime diagram is constructed. Moreover, nondimensional drag is found to be useful for regime identification. The model result is also compared with the analytic results by Miles(1969) and Smith(1980,1985), and the numerical results of Stein(1992), Miranda and James(1992) and Olaffson and Bougeault(1997). It is found that the simulated result in the present study is comparable with others.
The fifth part is the construction of the regime diagram for the Lantau island of Hong Kong. All eight major wind directions are discussed.