414 
WALLACE E. HOWELL 
TasLe 1—Trials of cloud seeding in the American tropics 
| Operations Results 
Location Year = |Area - 
Category Agent | Duration Increase Probability 
sq.mi pet 
Atlantic off Florida 1947 Uninvolved | Dry ice 1 day | Conversion of stra- 
| tiform super- 
cooled clouds 
observed in hur- 
ricane 
Honduras 1948 Uninvolved | Water 1 day | Extraordinary rain- 
fall in dry season 
Hawaii 1948-49 Uninvolved | Dry ice | 15 days) Some showers 
thought to be trig- 
| gered 
Mexico, Necaxa 1949-592; 800) Practical Agl | 54 mo. +9 0.0001 
Bolivia 1951 50) Practical Agl Uncertainty as to 
smoke trajectory 
Peru, Rio Chicama 1951-59 |3500) Practical Agl 80 mo +25 0.0001¢° 
Rio Mantaro 1951-56 |2500| Commercial | Agl 30 mo +20 0.07 
Cuba, Francisco (1951 300) Commercial | Agl 4 mo +26 ae 
Cespedes |1952 100, Commercial | Agl 3 mo +25 0.04 
Ermita 1952 50) Commercial | Agl 7 mo +46 0.005 
Francisco 1952 300, Commercial | Agl 11 mo +28 
Macareno 1952 150, Commercial | Agl 5 mo +35 0.08 
Najasa 1952 50| Commercial | Agl 6 mo +33 
Hawaii 1952-53 | ...| Uninvolved | Water se ave 
Cuba, Los Canos 1953 100, Commercial | Agl 3 mo +20 
Macareno 1953 150! Commercial | Agl 6 mo +20 
Cuba, Baltony 1953 30, Commercial | AgI 3 mo +15 we 
Preston, Boston 1953 500) Commercial | Agl 3 mo +19 0.002 
Francisco 1953 400) Commercial | AgI 5 mo +15 Pe. 
Puerto Rico, Fajardo 1953 250| Commercial | Agl 2 mo +14 etch 
Nearby waters 1953-54 | ...| Uninvolved | Water 5 mo ie 0.024 
Cuba, Macareno 1954 300/ Commercial | AgI,wa- | 2 mo +61 0.02 
| ter 
Puerto Rico, Fajardo 11954 250,/ Commercial | Agl | 2 mo +13 wate 
Cuba, Baltony 1955 30, Commercial | AgI | 3 mo +12 0.03 
Puerto Rico, Fajardo 1955 250| Commercial | AgI,wa- | 2 mo +27 0.07 
ter | 
Cuba, Francisco /1956 550/ Commercial | Agl 7 mo +25 0.005 
Colombia, Santa Marta 1956-57 | 350) Commercial | AgI 12 mo. | 39 decrease in wind 
damage per 
stormy day 
Cuba, Havana-Mantanzas 1956 4000) Commercial | Agl 3 mo +27 0.03 
Manati 1956 400, Commercial | Agl 3 mo +9 0.40 
Manati 1957 400, Commercial | Agl 8 mo +15 0.21 
Puerto Rico, south coast 1957 400| Commercial | Agl 2 mo +42 0.05 
Cuba, Baltony 1957 30| Commercial | Agl 2 mo +20 0.06 
Hispaniola, Romana 1957 600) Commercial | Agl 4 mo +31 0.10 
Cuba, Esperanza 1957 120; Commercial | Agl 2 mo +27 0.06 
Los Canos 1957 100| Commercial | Agl 2 mo +21 0.02 
Florida, Boca Raton 1957 Uninvolved | Agl No effect of seeding 
observed 
Average of all AgI seedings (24 cases) +22 
Average of all AgI and water seedings (3 cases) +43 
* Excepting 1952. 
b On commercial basis prior to 1955. 
¢ Separate evaluations of runoff showed increase of 35%. 
4 Water seeding with coarse spray in tops of trade Cumulus. Probability figure refers to likelihood 
that seeding caused precipitation in a cloud that would not otherwise have precipitation [Braham and 
others, 1957]. 
