PRECIPITATION Mi ' : 



Figure VI-6 — SIMULATED EFFECT OF CLOUD SEEDING 



10 p 1 1 1| 1 1 1 1 1 1 1 1 1 1 1 i i i| n 1 1 1 " 1 1 1 1 1 1 1 1 m i| m 1 1 1 1 1 1 1 m 1 1 1 1 1 1 1 1 1 1 1 1 " 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 



9 



U 



6 - 

 5 



4 r 

 3 - 

 2 

 1 



CLOUD ICE 



/ — s 



ll 1 1 1 ll II I ll 1 1 1 1 1 1 1 1 ll 1 1 1 1 1 



HAIL(GRAUPEL) 



I m ■ I ■ n i I i i i i 1 i i i i I i l i l I l i l l I l l l I t n ir 



12 3 4 



KILOMETERS 



10 11 12 13 



14 



15 16 17 18 19 20 



io um | nu |i nn m i n i mum ii mnn |i ii hh ii|i hh i hhh i hh mm i|i n i|i n i| m i pn i; m it 



9 - 



4 

 3 

 2 

 1 







1 2 



KILOMETERS 



1 1 1 1 1 1 1 i 1 1 1 1 



i i i i 1 1 i i 1 1 i i i i I i i t | [ i i i i 1 1 i 



16 



17 



18 



19 20 



The two diagrams demonstrate a silver iodide seeding experiment done on computer- 

 generated clouds. The numerical model simulates the growth of cumulus-type clouds 

 forming over a mountain ridge in a domain 20 km wide and 10 km high. The general 

 environmental airflow is from left to right. Clouds have formed to the left in the 

 model and grown to form an anvil present at 7 km. The upper diagram shows the 

 non-seeded case; the bottom, the seeded case. Seeding is simulated by changing all 

 cloud liquid to cloud ice and the rain to precipitating ice at -10°C instead of 

 — 25°C in the natural (non-seeded) case. The hail (or graupel) shown is in concen- 

 trations greater than 1 gm of hail per kg of air. Rain is in concentrations greater 

 than 1 gm per kg. These results demonstrate the effects of overseeding — less rain 

 and less hail come from the seeded cloud since the large amounts of cloud ice that 

 form are carried aloft and downwind in the anvil. 



177 



