Sbction III., 1908. [ 1S7 ] Trans. R. S. C. 



XIII. — Local Temperature Forecasting by Differences in Temperature 

 between Mount Royal and McGill College Observatory. 



By Professors C. H. McLeod, Ma.E., and H. T. Barnes, D.Sc. 



McGill University, Montreal. 

 (Read May 28, 1908). 



In our third communication* which we had the honour to present 

 before Section III last year, we dealt with a feature of our work 

 which has proved very interesting and instructive. This was the 

 ability to forecast from the differential records what the tempera- 

 ture conditions were likely to be for the succeeding day. The idea is 

 not a new one as we pointed out, but the ease with which the tempera- 

 ture difference between our high and low level stations can be read 

 makes the " advance changes " more noticeable. 



There is another point in connection with our work which must 

 be remembered and that is the extreme delicacy of our instruments 

 when contrasted with the ordinary observatory thermograph. The 

 fact that we can observe " advance changes " from so low a level as 

 our mountain top is solely due to this cause. As we suggested, par- 

 ticularly in reference to Prof. Church's work on Mount Rose, a higher 

 station might give us greater variations and therefore, with our instru- 

 ments, earlier warnings. 



It now seems to be well established, as a result of the numerous 

 balloon ascensions, that the comparatively low regions of the upper 

 atmosphere show advance changes over those at the earth's surface, 

 whereas above the inversion layer there appears to be a lag. It 

 seems to the authors natural to expect a change of temperature con- 

 ditions, which is usually accompanied by a change of wind direction 

 or velocity, to be first manifest in the region just above the earth. 

 We often note a change of wind direction by the movement of the 

 clouds before such a change has produced an effect on the earth's 

 surface. 



Records during the past Year. 



Our series of records was again greatl;^ interfered with during 

 the past year from the giving out of the insulation of a portion of the 

 cable near the tower. Owing to the absence of one of the authors from 



Trans. Roy. Soc. Can., 3 Series, Vol. 1, p. 3 (1908). 

 ' Compare H. H. Clayton, Monthly Weather Review, Vol. 35, p. 457 (1907). 



