Abstruct
Yamagata prefecture is a prefecture of Japan located in the Tohoku region on Honshu island.There are 6 mountain ranges in Yamagata prefecture, their names are Hinotodake, Kamuro, Asahi, Ohu, Iide, and Azuma(Fig.1). Especially, Asahi mountain ranges plays an important role to make the characteristics of the local weather in Yamagata prefecture.
Fig.1 Mountain ranges in Yamagata Pref.
In this article, the computational simulation was performed for the precipitation in Yamagata prefecture in winter. The relationship between winter seasonal wind and the precipitation was reproduced in the simulation.When winter seasonal wind was weak, the precipitation area stayed in front of the Asahi mountain range.However, when winter seasonal wind was strong, the precipitation area went to the west through the north side and the south side of the Asahi mountain range.
Introduction
Yamagata prefecture is a prefecture of Japan located in the Tohoku region on Honshu island.There are 6 mountain ranges in Yamagata prefecture, their names are Hinotodake , Kamuro, Asahi, Ohu, Iide, and Azuma(Fig.1). Yamagata prefecture also consists of four areas, Shonai, Mogami, Murayama, and Okitama(Fig.2).
Fig.2 Areas in Yamagata Pref.
For your information, author was born and brought up in Yonezawa city in Okitama area.Yonezawa is located in the southeast corner of Yamagata prefecture. They have a heavy snow every winter, there.
Governing Equation and Numerical model
The governing equations are following simultaneous nonlinear partial differential equations, incompressed Navier-Stokes equation, heat equation, and transport equation of specific humidty.The numerical model shown in Fig.3 was constructed, and the simulation was performed([1], [2], [3]).
where，ui，ui : velocity components，xi，xj : displacements，p : pressure，t : time，θ : potential temperature，q : specific humidty，g : gravitational acceleration，Re : Reynolds number，Fr : Froude number，Pr : Prandtl number，Prt : turbulence Prandtl number，δi3 : Kronecker delta，Q : Generation term，Cs : Smagorinsky constant，Δ : spatial filtering range (ΔxΔyΔz)1/3，ν : Kinematic viscosity of air，νG : coefficient of eddy viscosity ，αt : Eddy diffusion coefficient of thermal，Ｓij : Strain energy，U0 : characteristic flow velocity，H0 : characteristic length，θ0 : characteristic potential temperature，Δθ : difference of potential temperature，─ : spatial filtering.
The relationship between winter seasonal wind and the precipitation
Fig.4 shows an example of the results of numerical experiments.
According to Fig.4, when winter monsoon wind, which direction around Yamagata prefecture is the west-north-west, was weak, the precipitation area stayed in front of the Asahi mountain range.However, when winter monsoon was strong, the precipitation area went to the west through the north side and the south side of the Asahi mountain range.Generally, the wind direction of the winter monsoon around Yamagata prefecture is the west-north-west.The relationship between winter seasonal wind and the precipitation was reproduced in the simulation.Asahi mountain ranges plays an important role to make the characteristics of the local weather in Yamagata prefecture.
Yamagata prefecture is a prefecture of Japan located in the Tohoku region on Honshu island.There are 6 mountain ranges in Yamagata prefecture, their names are Hinotodake, Kamuro, Asahi, Ohu, Iide, and Azuma(Fig.1). Especially, Asahi mountain ranges plays an important role to make the characteristics of the local weather in Yamagata prefecture.
Fig.1 Mountain ranges in Yamagata Pref.
In this article, the computational simulation was performed for the precipitation in Yamagata prefecture in winter. The relationship between winter seasonal wind and the precipitation was reproduced in the simulation.When winter seasonal wind was weak, the precipitation area stayed in front of the Asahi mountain range.However, when winter seasonal wind was strong, the precipitation area went to the west through the north side and the south side of the Asahi mountain range.
Introduction
Yamagata prefecture is a prefecture of Japan located in the Tohoku region on Honshu island.There are 6 mountain ranges in Yamagata prefecture, their names are Hinotodake , Kamuro, Asahi, Ohu, Iide, and Azuma(Fig.1). Yamagata prefecture also consists of four areas, Shonai, Mogami, Murayama, and Okitama(Fig.2).
Fig.2 Areas in Yamagata Pref.
For your information, author was born and brought up in Yonezawa city in Okitama area.Yonezawa is located in the southeast corner of Yamagata prefecture. They have a heavy snow every winter, there.
Governing Equation and Numerical model
The governing equations are following simultaneous nonlinear partial differential equations, incompressed Navier-Stokes equation, heat equation, and transport equation of specific humidty.The numerical model shown in Fig.3 was constructed, and the simulation was performed([1], [2], [3]).
where，ui，ui : velocity components，xi，xj : displacements，p : pressure，t : time，θ : potential temperature，q : specific humidty，g : gravitational acceleration，Re : Reynolds number，Fr : Froude number，Pr : Prandtl number，Prt : turbulence Prandtl number，δi3 : Kronecker delta，Q : Generation term，Cs : Smagorinsky constant，Δ : spatial filtering range (ΔxΔyΔz)1/3，ν : Kinematic viscosity of air，νG : coefficient of eddy viscosity ，αt : Eddy diffusion coefficient of thermal，Ｓij : Strain energy，U0 : characteristic flow velocity，H0 : characteristic length，θ0 : characteristic potential temperature，Δθ : difference of potential temperature，─ : spatial filtering.
The relationship between winter seasonal wind and the precipitation
Fig.4 shows an example of the results of numerical experiments.
According to Fig.4, when winter monsoon wind, which direction around Yamagata prefecture is the west-north-west, was weak, the precipitation area stayed in front of the Asahi mountain range.However, when winter monsoon was strong, the precipitation area went to the west through the north side and the south side of the Asahi mountain range.Generally, the wind direction of the winter monsoon around Yamagata prefecture is the west-north-west.The relationship between winter seasonal wind and the precipitation was reproduced in the simulation.Asahi mountain ranges plays an important role to make the characteristics of the local weather in Yamagata prefecture.
