CLASSIFICATION INDEX 
1, First Designator: 
z. Second Designator: 
3. Third Designator: 
CONTINENTALITY CLASS 
T - Tropic 
O — Oceanic 
S - Sub-Continental 
C - Continental 
A - Arctic 
The first two numerals indicate the mean 
air temperature to the nearest 1°F. for 
the coldest month of the year (usually 
January or February in the Northern 
Hemisphere and July or August in the 
Southern Hemisphere). 
The second two numerals indicate the 
mean air temperature tothe nearest 1°F. 
for the warmest month of the year (July 
or August in the Northern Hemisphere, 
January or February in the Southern 
Hemisphere). 
The difference between the first and 
second designators is an indication of 
continentality. The Third Designator is 
taken from the following table. 
ANNUAL RANGE OF 
MEAN MONTHLY AIR TEMPERATURE 
Less than 6°F. 
6° to 14°F. 
15° to 35°F. 
Greater than 35°F. 
Greater than 50°F .* 
Css 
*The annual range of mean monthly temperature in the Artic and 
Antarctic is generally greater than 50°F. Water temperatures, air-sea 
temperature differences, ice location and limits, and typical vertical 
thermal structure of the water should be obtained from H. O. Pub. No. 
705, ‘‘Oceanographic Atlas of the Polar Seas’’ (reference no. 26). 
