where

NN=0.7NwithNgiven by eq. (58).Nanduare evaluated initially at stack height. Onceplume rise has been computed, subsequent plume rise estimates are made (iteratively until

convergence) by averaging the

uandNvalues at stack top with those ath h. Equation (95)s s+ Δ 2is used for downwind distances that are less than the distance to final rise (

xf). Beyondxf, )hsremains constant. The distance at which the stable plume reaches its maximum rise is given

by

Upon substituting eq. (96) for

xin eq. (95) the maximum final rise of the stable plume)

hs{xf} reduces to:As with eq. (95), the velocity,

up, andNin eqs. (97) are evaluated initially at stack height andthen iteratively.

When the atmosphere is close to neutral, the Brunt Vaisala frequency,

N, is close to zero, andeq.(95) can predict an unrealistically large plume rise. Under, these circumstances, plume rise is

limited by atmospheric turbulence. This happens when the rate of plume rise under neutral

conditions is comparable to F

w. Under these conditions, stable plume rise (eq. (97)) is limited bythe neutral rise calculated from Weil (1985) as

where the neutral length scale

L F(u u) .n b p= *2

As the wind speed approaches zero, eq. (95) again predicts unrealistic values. In these nearcalm

conditions the stable plume rise (eq. (97)) is limited by the calm rise expression that is based

on the work of Morton et al. (1956) and Briggs (1969) such that,

Finally, the stable plume rise is limited by a calculation of the unstable rise (see Section

5.6.1).

66

σ σ σ

y yl yo2 = 2 + 2 (100)

5.7

Source CharacterizationAERMOD gives the user the ability to characterize a source as either a point, an area, or a

volume. AERMOD additionally has the capability of characterizing irregularly shaped area

sources

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

castellano: DISPER CUSTIC DESCAR RADIA italiano:

castellano: DIS CUS DES RAD english: DIS CUS DES RAD

português: DIS CUS DES RAD italiano: DIS CUS DES RAD