NO. 17.] THE METEOROLOGICAL PERIODS IN THE ARCTIC SEA. 



605 



(p. 599). The stronger the wind, the more does it tend to equalize the tempera- 

 tures of day and night, or to lower the diurnal range. 



In the following Table, I have put together the mean monthly values of 

 (1) the diurnal range of the radiation of the sun and sky, r, (2) the amount 

 of cloud, c, (3) the velocity of the wind in m. p. s., v, and (4) the diurnal 

 range of the temperature of the air, R, for the months March to September. 



The radiation varies regularly from month to month, and is nearly 

 constant from May to August. 



The amount of cloud varies considerably, and is highest from May to 

 September. 



The velocity of the wind does not vary much. 



The diurnal range of the temperature shows the largest variation during 

 the months from March to September. 



From March to April the range of radiation increases rapidly. The 

 amount of cloud decreases to a minimum, as does also the velocity of the 

 wind; and all three factors are working to raise the diurnal range of the 

 temperature. From April to May the range of radiation rises a little, but 

 the amount of cloud is rapidly increasing, and also the velocity of the wind. 

 The two last-named factors bring the range of the temperature down, notwith- 

 standing the effect of the radiation. 



From May to June the range of radiation increases very little, but the 

 amount of cloud increases one degree, and the temperature-range is lowered 

 by the cloudiness in spite of the increasing radiation and decreasing wind- 

 velocity. 



