empirical formulations adopted for the estimation of w during stable conditions
hold good in this study. However, for unstable conditions it was observed that the
w values are underpredicted by a factor of 2 consistently using the scheme of
Irwin (1979). It may be mentioned here that estimation of G(z=zi) according to
the various ranges of z=zi are site specific which can change from place to place,
thus indicating a need for readjustment of constants used in Equations (16) to
(19) for estimating G(z=zi). Hence more recent formulations based on Baerentsen
and Berkowicz (1984) and Brost et al. (1982), referred as BB scheme and from
Panofsky et al. (1977) and Hicks (1985), referred as PH scheme were also utilised
for this purpose. Table VIII shows an intercomparison of the performance of all
three schemes with observed values of w for unstable conditions. As shown in
Table VIII, the Irwin (1979) scheme shows gross underprediction while the BB
scheme shows gross overprediction. However, the PH scheme based on Panofsky
et al. (1977) and Hicks (1985) shows reasonably good estimates of w when compared
with observations and hence was utilised for the estimation of dispersion
coefficients in the present study.
Figures 1–4 showvalues of v and w for stable and unstable conditions respectively.
These scatter plots showa good relationship between observed and predicted
values.