28 
The Colorado Experiment Station 
TABLE XII.—PERCENTAGE POSSIBLE SUNSHINE AT DIFFERENT POINTS IN 
THE UNITED STATES. 
Station Percentage Possible Sunshine 
Albany, N. Y.\. 48 
Amarillo. Texas . 78 
Atlanta, Georgia . 58 
Baltimore, Md. 59 
Boston, Mass. '.. 58 
Chicago, Ill. 58 
DENVER, COLORADO . 65 
Dubuque, la. 57 
DURANGO, COLORADO . 75 
GRAND JUNCTION, COLORADO. 67 
Indianapolis, Indiana . 55 
LaCross, Wis. 56 
Memphis, Tenn. 62 
New Orleans. La. 58 
Omaha, Neb. 59 
PUEBLO, COLORADO . . . 76 
Richmond, Va. 60 
St. Louis, Mo. 58 
San Diego, Cal. 68 
Santa Fe, New Mexico . 75 
Tacoma, Washington . 88 
Yuma, Arizona . 88 / 
\ 
/ 
The average percentage of possible sunshine for the.four Col¬ 
orado stations in the table above is 70.7. This percentage is lower 
at most high elevations, except the large highland parks, such as 
San Luis, Middle and North. 
EFFECT OF INCREASE IN ALTITUDE UPON CLIMATIC FACTORS 
Mention has been made of the great range of altitude in Colo¬ 
rado. All are familiar with the fact that an increase in altitude 
brings about changes in the factors which make up our climate, 
and which operate upon plants. However, altitude must not be 
considered as a single environmental factor, like precipitation, or 
light, or humidity. An increase in altitude generally brings with 
it a number of changes in environmental factors. The principal 
changes resulting from an increase in altitude are as follows: 
1. Decrease of Air Pressure.—The amount of this decrease 
may be judged from the following table. Atmospheric pressure is 
affected slightly by temperature; in the table a temperature of 
68° is taken. (Table modified from Hann’s Handbook of Clima- 
tology.) 
