THE NUMBER FLUX OF SNOW CRYSTALS AT THE GROUND

Abstract

Many measurements of the snowfall rate R and the average mass per crystal m? have provided values of R/m?, the number of snow crystals reaching unit area of the surface per unit time. A typical number is 1 per cm.2 per sec. Over a whole season's data, the flux is proportional to the snowfall rate. Specifically, two-thirds of the measurements lie within a factor two of a locus R/m? (cm.?2 sec?1) = 1.5 R1,0 where R is in millimeters of water per hour. Thus the principal contribution to any increase in the snowfall rate is the formation of new crystals, rather than the growth of existing ones.