60 BULLETIN 1333, U. S. DEPARTMENT OF AGRICULTURE. 



If an examination is made first of the Colorado Springs station, 

 which may perhaps give a better conception of the wind movements 

 of the region than even the control station, because of the free 

 exposure of the former, it is seen that, for the whole year, the wind 

 movement is much greater than that at the control station, and 

 greater than that of any of the mountain stations, except that at 

 timber line on Pikes Peak. The growing-season total bears almost 

 the same relation to the control station as the total for the whole 

 year. The Plains station has a low ratio to the control station dur- 

 ing the early winter months, November to January, which may mean 

 that the location of the control station gives winds at that time a 

 magnified local effect. The Plains station has relatively the highest 

 winds during the spring, probably because it is more susceptible to 

 the winds which blow from all directions toward storm centers during 

 the spring period. Actually, the most severe season on the Plains must 

 be just before the end of winter and before thawing has become general. 



The Monument yellow-pine station is only 20 miles from Colorado 

 Springs, but being in the edge of the hills is fairly well protected from 

 north-south currents. This station shows distinctly mountain 

 characteristics, but scarcely more than half the total movement 

 recorded on the Plains. Part of this difference is no doubt due to 

 the elevation of the anemometer, which is barely above the top of 

 the surrounding oak-brush clumps. The relatively high values at 

 this station throughout the entire winter period define the degree of 

 exposure on the west. It is not doubted that, with a similar local 

 exposure of the anemometer, this station would show winter values 

 just about the same as the control station. The evaporation attend- 

 ing such winds would be augmented by the higher temperatures in 

 the pine belt, but their effect on vegetation would be decreased by 

 the shortness of the soil-freezing period. 



The local yellow-pine station (F-2) shows no great variation from 

 the control station, such difference as exists being explicable, prob- 

 ably, by the wind-breaking power of the surrounding trees, which 

 run up 30 to 40 feet higher than the anemometer. No doubt the 

 high January ratio at this station was due to the wind blowing from 

 certain directions so that the currents reached the anemometer un- 

 broken. On the whole, it would be best to assume that the ex- 

 posure, if the trees were not present, would correspond closely to 

 that of the control station. 



The record at the yellow-pine ridge station (F-12) is difficult to 

 explain, inasmuch as both the soil of the ridge and the character of 

 the growth thereon are suggestive of the most extreme wind exposure. 

 Indeed, a few isolated days may be found when the velocities of west 

 winds recorded here exceed those at the control station. On the 

 whole, however, the movement is considerably less. The anemom- 

 eter was placed high enough to be practically free from the influence 

 of the surrounding trees, which are short and widely scattered. The 

 deficit can he accounted for only by the position of the station on a 

 bench of considerable area, which does not directly contribute to and in 

 fact isonl of the paths of the local convert ional currents, which naturally 

 hug the slopes and valley bottoms. The station can not he considered 

 to represent so severe a wind exposure as the control station: hut. if 

 its Longer period of s'>il freezing is considered, it represents, as will he 

 seen later, a closer approach to the limiting conditions for yellow pine. 



