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Abstract of Paper on the Diurnal Range of Temperature Variability at the 

 Summit and Base of Ben Nevis, Lady Franklin Bay, and Hong Kong. 

 By K. C. Mossman. # 



The average variability of temperature at any place is obtained by taking the difference 

 of temperature at the same hour on successive days, and taking the mean value of this 

 difference irrespective of sign. With a view to ascertaining whether this variability 

 varied with the hour selected for comparison, the hourly temperature records at four 

 places have been examined, and the day to day change of temperature at each hour 

 noted. The places are — the Ben Nevis Observatory, the Fort- William Observatory, 

 the Hong Kong Observatory, and the Arctic Station at Lady Franklin Bay, lat. 81° 44' 

 N., long. 64° 45' W. At each place one year's record was taken, which, though too 

 short a time to give a true mean, yet gives a fair approximation towards it. The mean 

 values for each hour of the twelve months at the four stations are given in the 

 accompanying tables, the highest value in each month being put in heavy type and the 

 lowest in italic. 



The monthly mean values at the right hand of the tables show that there is little 

 difference between Ben Nevis and Fort- William, except in July and August, when the 

 former is markedly in excess. On the mean of the whole year, this day to day 

 variability of temperature is one-tenth of a degree greater at Ben Nevis than at Fort- 

 William, 3°'8 and 3°'7, notwithstanding that the diurnal range of temperature at the 

 former place is little more than half that at the latter. Hong Kong has the lowest 

 annual variability, 2 0, 3, and Lady Franklin Bay the highest, 5°'l. At the latter station, 

 which has a day and night of four and a half months' duration, these day to day 

 differences are greater during the nocturnal period than during the long day. 



The hourly values at Ben Nevis on the mean of the year are highest from 

 midnight to 9h., and lowest from llh. to 18h. At Fort-William the same diurnal 

 change occurs, but the difference between the maximum and minimum values is greater. 

 At Fort- William during the summer months, from April to August, a second maximum 

 appears between 14h. and 19h. On the summit of Ben Nevis, however, this second 

 maximum is very small. During these months there is strong insolation in the 

 afternoon hours ; ascending currents flow up the sides of the hill, which bring an 

 increased amount of cloud to the summit, and no doubt so exert a conserving 

 influence on the temperature there. On the mean of the year the variability is greater 

 at the summit than at the base of Ben Nevis, except during the five hours ending 

 6 a.m., but the diurnal range of the variability is greater at the base. 



* See Journal of Scottish Meteorological Society, vol. x. p. 150. 



