1.3.3 Atmospheric instability Dry lapse rate =0.98°C/100m Potential temperature 0.286 Inversion(air temperature higher at upper layer),e.g. Radiation inversion -Frontal inversion Advection inversion Why important?....Related to "atmospheric turbulence"-"diffusion
1.3.3 Atmospheric instability • Dry lapse rate • Potential temperature • Inversion ( air temperature higher at upper layer), e.g. : – Radiation inversion – Frontal inversion – Advection inversion θ = = − T P P T P k k 0 1 0 286 1000 ( )/ . γ ∂ ∂ d s T z ≡ − = 0.98°C / 100m Why important? …. Related to “atmospheric turbulence” --- “diffusion
Stable Neutral Unstable d Fanning Coning .ya Looping Stable in lower layer Stable in upper layer ZA Roofing Fumigating Effects on pollutant dispersion by atmospheric instability
z z z γd Fanning γd Coning γd Looping T z z γd Roofing γd Fumigating Effects on pollutant dispersion by atmospheric instability Stable Neutral Unstable Stable in lower layer Stable in upper layer
>r(unstable) <0(unstable) aT 88 三 =Yd (neutral) or 二 0(neutral) 0z 02 <rd (stable) >0(stable) Criteria of atmospheric instability Richardson number Ri Monin-Obukhov length scale L Dimension analysis and Similarity theory for lower atmosphere Meteorological probability density matrix
γ ∂ ∂ γ γ γ ≡ − > = < T z d d d (unstable) (neutral) (stable) ∂ θ ∂ z < = > 0 0 0 (unstable) (neutral) (stable) or Criteria of atmospheric instability Richardson number Ri Monin – Obukhov length scale L Dimension analysis and Similarity theory for lower atmosphere Meteorological probability density matrix
1.4 Motion of the Air and Wind 1.4.1 Governing Equations of Air Motion 0x*0y 8x Oy+L三= us+ux 8x 1迎+F 8t ousuy oy ouxfuy= ouyuy dy uy+ux ox 8t ouy fus +F pay 0= 1 ap p oz -8 f=20sin geostrophic factor
1.4 Motion of the Air and Wind 1.4.1 Governing Equations of Air Motion = 0 ∂ ∂ + ∂ ∂ + ∂ ∂ z u y u x ux y z y x x y x x x F x p fu y u u x u u t u + ∂ ∂ − = − ∂ ∂ + ∂ ∂ + ∂ ∂ ρ 1 x y y y y x y F y p fu y u u x u u t u + ∂ ∂ + = − ∂ ∂ + ∂ ∂ + ∂ ∂ ρ 1 g z p − ∂ ∂ = − ρ 1 0 f = 2Ωsinφ ~ geostrophic factor
1.4.2 Wind in the free atmosphere Air motion has different spatial scales. ● Because of the difference of sun radiation on equatorial and pole areas,there exist several global scale circulations.China is located at mid-latitude region, westerly wind band in the northern hemisphere,with seasonal variations:monsoon region
1.4.2 Wind in the free atmosphere • Air motion has different spatial scales. • Because of the difference of sun radiation on equatorial and pole areas, there exist several global scale circulations. China is located at mid-latitude region, westerly wind band in the northern hemisphere, with seasonal variations: monsoon region