Question

By comparing Figures 3.21 and 3.22, estimate roughly what the average rainfall intensity was in the data from which Figure 3.21 was derived; in other words, for what value(s) of P are these two figures in agreement? Assume that the various gages, whose measurements were used in these two figures, have similar hydrodynamic characteristics affecting the gage deficiencies.

PRECIPITATION 108 0.2 0.4 0.6 0.8 4 10 Wind speed (m s-1) Fig.3.21 Curves of gage catch deficiency against wind speed for liquid precipitation (curve 1); for solid precipitation with a single shield around the gage (curve 2); and for solid precipitation with an unshielded gage (curve 3). The curves represent a summary of data from different sites in the United States, Russia and England, collected by Larson and Peck (1974). For rain the catches of shielded and unshielded gages were nearly the same. 10 Wind 3-4 m s-1 4 2-3 m s-1 1-2 m s-1 0-1ms-1 0.08 mm mi-1 4.8 mm h1 0.02 0.04 0.06 3.6 Fig. 3.22 Class averaged percentage difference (%) between precipitation 1.5 m) Hellmann gages, and a ground-level gage, observed by Sevruk (1993a) as a function of mean precipitation intensity P for different wind speeds. Based on data obtained at Les Avants, Switzerland, Apri September, 1938-1947 by elevated (at 1 and

Wilfried Hydrology Book question 3.7

Answer 1

Assume that the deficiency in Fig. 3.21 is the same as the percent difference in Fig. 3.22 divided by 100. Inspection of the two figures indicates that typical rainfall intensities of curve 1 in Fig. 3.21 must have been in the range of roughly 1 to 1.5 mm/h.