Page 354 - Fundamentals of Air Pollution 3E

IV. Dispersion Instrumentation 309

Fig. 19-9. U, V, W wind system. Source: Photo courtesy of R. M. Young Co.

Additional near-surface measurements may also be required to support
calculated quantities such as the bulk Richardson number (a stability pa-
rameter):

which requires a temperature gradient, a temperature, and wind speed at
the height of the boundary layer h. For this purpose, in addition to the wind
speed at 10 m from the instrumentation, a vertical temperature difference
measurement is needed. This can be obtained for the interval of 2-10 m
aboveground using two relatively slow response sensors wired to give the
temperature difference directly. Again, hourly averages are of greatest