696 



BULLETIN OF THE BUREAU OF FISHERIES 



Mean winter temperatures °F, with departures from normal (J. W. Smith, 1913-1921) — Continued 



1915-16 



The diagrams of air and surface temperature at Gloucester and at Boothbay for 

 the winter of 1919-20 (figs. 29 and 30) show the temperature of the water closely- 

 following that of the air in its 10-day fluctuations, and reflecting a loss of heat by 

 radiation more or less rapid as the difference between the temperature of air and 

 water is greater or less." 



The loss of heat from the surface of the gulf increases proportionately from 

 November on, as the average difference between air and water increases, a general 

 rule illustrated by the temperature cycle of Massachusetts Bay for the winter of 

 1924-25 (p. 651) . The water continues to suffer a net loss of heat in this way until the 

 average temperature of the air once more rises above that of the water, an event to 

 be expected about the tenth of March (p. 668). 



CHILLING EFFECT OF MELTING SNOW 



Another cooling agent becomes effective from December untU spring — namely, 

 the melting of the snow that faUs on the surface of the gulf. The amount of heat 

 taken from the water by melting snow is, of course, that required to melt an equiv- 

 alent amount of ice; a fall of 1 foot of snow (a moderate snowstorm for northern 

 New England and the Maritime Provinces) would represent approximately 1-1 J^ 

 inches of ice, more or less according to the quality of the snow. 



The normal snowfall, by months, for the lands bounding the gulf is tabulated 

 below from data supplied by the United States Weather Bureau; also the actual 

 snowfall for representative winters since the oceanographic investigation of the gulf 

 was undertaken. 



Normal snowfall and its equivalent in water, both given in inches 



" The air temperature of the coldest days was many degrees below the 10-day averages shown on the diagrams, often 10° 

 colder than the surface of the water. ' 



