In the SBL the vertical turbulence contains only a mechanical portion which is given by eq. (36).

The use of the same F

2

wmexpressions for the SBL and CBL is done to ensure continuity ofturbulence in the limit of neutral stability. Figure 8 illustrates AERMOD’s assumed vertical

turbulence profile for the SBL. This is similar to the profile for the CBL except for a notable

increase in the value of F

wmr. Since values for Fwmrare based on the magnitude of the wind speed33

Figure 8: Profile of vertical turbulence in the SBL

σ σ σ

vT vc vm2 = 2 + 2 . (38)

at

zi, the differences in the two figures stem from settingzo =0.0001ziin the CBL example casewhile for the SBL case

zo =0.001zi.4.1.6 LATERAL TURBULENCE CALCULATED BY THE INTERFACE

In the CBL the total lateral turbulence, F

2

vT, is computed as a combination of a mechanical(F

vm) and convective (Fvc) portions such thatIn the SBL the total lateral turbulence contains only a mechanical portion. AERMOD, uses the

same F

vmexpression in the CBL and SBL. This is done to maintain continuity of Fvmin the limitof neutral stability. A description of mechanical and convective profiles of lateral turbulence

follows.

4.1.6.1

Mechanical Portion of the Lateral TurbulenceThe variation with height of the mechanical portion of the lateral turbulence is bounded by

its value at the surface and an assumed residual value at the top of the mechanical mixed layer.

The variation between these two limits is assumed to be linear. Based on observations from

numerous field studies, Panofsky and Dutton (1984) report that, in purely mechanical turbulence,

the lateral variance near the surface has the form

where the constant,

C, ranges between 3 and 5. Based on an analysis of the Kansas data, Izumi(1971) and Hicks (1985) support the form of eq. (39) with a value of 3.6 for

C.Between the surface and the top of the mechanically mixed layer, F

2

vmis assumed to varylinearly as

n951 - n952 - n953 - n954 - n955 - n956 - n957 - n958 - n959 - n960 - n961 - n962 - n963 - n964 - n965 - n966 - n967 - n968 - n969 - n970 - n971 - n972 - n973 - n974 - n975 - n976 - n977 - n978 - n979 - n980 - n881 - n982 - n983 - n984 - n985 - n986 - n987 - n988 - n989 - n990 - n991 - n992 - n993 - n994 - n995 - n996 - n997 - n998 - n999 - n1000

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