There are three types of distribution of convectional rainfall intensity.
(a) a peak type.
(b) several peaks type, and
(c) mountain-range type.
These typ_??_s are typically shown in Fig. 1.
T (=mean period of each intensity curves in min), Tm (=the period of the maximum intensity), I (=mean intensity in millimeter per 10min.), Im (=the maximum intensity in millimeter per 10min.), Tm/T, Im/I etc. are shown in Table 1.It is clear from this table that the amount of rainfall of a peak type rain is the greatest.
The relations between T and Tm, and between I and Im of each type are shown in Fig. 2 and 3. The period of the maximum intensity increases linearly proportionally with the mean period of each rainfall intensity, but the maximum intensity rapidly increases.
The variation of rainfall intensity with the mean period is shown in Fig. 4. The most observed points are enclosed in the closed curve. That is the range, in which the intensity and period are frequently observed, are limited in
24min. <T<47min., and
0.6mm/10min. <I<5.1mm/10min. Similarly
17min. <Tm<70min., and
1.4mm/10min. <Im<10.3mm/10min.
The value of the maximum intensity and its period for convectional rain increase proportionally amount of rainfall. Next, the variation of rainfall intensity, air temperature (t) and rain temperature (T) for some rainfall are shown in Fig. 8 and it seems that the maximum number of rain droped per unit area (mark M) occurs a few minutes before the maximum intensity.
In Fig. 9 the model of rainfall is shown.
