PRECIPITATION IN WINTER STORMS IN CALIFORNIA 
MacCready and others [1958], both the drop-size 
distribution and the potential gradient have 
characteristics indicative of the precipitation ori- 
gin. When the radar and vertical cross section 
indicate that the precipitation must be warm- 
cloud origin, the drop distribution follows the 
Blanchard type and the potential gradient shows 
fair-weather field. When the evidence points to 
ice-precipitation origin, the drop spectrum fits 
the Marshall-Palmer distribution and the po- 
tential gradient goes negative, or fluctuates, and 
405 
may show discharges [MacCready and others, 
1958]. In Figure 6, Drop Samples 1 to 9 are 
given as dots and show good agreement around 
the straight line representing idealized Blanchard 
distribution; while Samples 10 and 11, the broken 
lines, show marked disagreement. Figure 7 
shows samples 10 and 11 agree well with Mar- 
shall-Palmer distribution line. Figure 8 shows 
the potential gradient record for the period. 
Note the change just before 20h 00m. Radar 
indicated that Samples 1 to 9 were warm cloud 
10% == == 
5 ae ee 
5 ne ae ae 
3 
2 
ot-—4 
\ | 
5 
Jian = 
3 ° 
2 
3 
lO iN = 
BS ee ee 
“ly 
Np (M 2MM 
2 4 6 8 
lo 12 14 16 
18 20 2D 
Fic. 6—Rain with warm-cloud origin is expected to have drop size distribution following the 
straight line; dots show agreement of Samples 1-9; broken lines show poor fit for Sample 10 and 11 
