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barrier accounts for 60.5% of the total snowfall. The orographic influence on snowfall at Wolf Creek Summit is also strongly reflected by the 700 mb wind speed. This is shown in Figure 44. The distributions were computed using 4 mps class intervals. It is readily apparent from the distributions of snowfall frequency and amounts that much more snow is f1i ~8 ~ ..J .6 ..J ti! ~4 ! ,2~ ~J 20 w ~ ~ 15 W '-' a: ~ 10 W 2 >- j 5 w a: (b) I I :-'-PERCENTAGE OF TOTAL SOOWFALL , I I : FREOUEN::Y OF OCCURRENCE en I r---1 l l 90 'l3o 50 170 210 250 290 70CXVIB WIND DIRECTION (degrees) Figure 43. --(a) Mean Daily Snowfall at Wolf Creek Summit as a function of 700 mb wind direction. (b) Distributions of total snowfall and total occur- rences as a function of the 700 rob wind direction computed over a 20-degree class interval. f1i ~ ~ ..J ,6 ~ ,4 6j ~ 8,2 ~ w 0 ::: 10 w t? ~ Z ~ W CL 5 W )- ti ..J ~ 0 (0 ) ~ (b) FREWENCY OF OCCURRENCE PERCENTAGE OF TOTAL SNOWFALL -----, : ----I I I I , , r--- , , ro ~ m ~ ~ 700MB WIND SPEED (MPS) Figure 44. --(a) Mean Daily Snowfall at Wolf Creek Summit as a function of the 700 mb wind speed. (b) Distribution of total snowfall and total occur- rences as a function of the 700 mb wind speed com- puted over a 4 mps class interval. 56 realized per occurrence at the higher wind speeds. I i The class interval from 7. 5 to 11. 5 mps contains the peak in the f~equency of occur- rence and also in total snowfaiJ.l. However substantial quantities of snow iare realized' from a few occurrences at wind speeds of 16 mps and greater. This is indicated m9st spectacularly by the mean daily snowfall. Ir the 15.5 to 19. 5 mps class interval three storlJIls averaged over 1. 8 inches per day (water equ~valent) while one storm having wind speeds of a,round 29 mps produced 2.6 inches per day. ' The cases having wind speeds of 15.5 mps or g~eater represent only about 3% of the total cases but contribute over 21 % of the total snowfall: , Since the rate of co:ndensation produc- tion is only a linear function Of the vertical motion, a more linear relationship between mean daily snowfall and the speed 01' the wind over the mountain barrier might be expected. This relation appears to hold for w:ind speeds below about 10 mps, but above this value indications are that some favorable combination of factors is increasing the snowfall. This may be due to the superposition of the orogr,aphic influence upon strong synoptic scale upyrard motions at the higher wind speeds. Also', increased low level convergence forced by t~e concavity of the terrain may account for part 9f the non-linearity. (3) Daily snowfall related to ~oisture supply The 700 mb mixing;ratio is a good measure of the moisture supply contained in the air mass that will be lifted ov~er the mountain barrier. Figure 45 ' shows the! distribution of snowfall occurrences and amclunts as a function of this variable computed usi~g O. 4 gm/kgm class intervals. , -r I ! I I I I -I I It is apparent that tp.e center of mass of the frequency distribution is displaced sub- stantially toward lower moisture values from the center of mass of the snowfall distribution. The centers are found at 1. 95 gm/kgm and 2. 17 gm/kgm, respectively. iThus, the larger daily snowfalls occur in association with the higher 700 mb mixing ratios cis would be expected. I Figure 46 shows the distribution of snowfall occurrences and quantity as a function of this variable computed using 0.4 gm/kgm ' class intervals for Wolf Creek Summit. It is immediately apparent that the center of mass of the -total snowfall distribution is displaced substantially toward higher moisture values from the center of mass of the frequency distribution. The centers are found at 2.5 gm/kgfn and 2.1 gm/kgm, respectively. Thus, the , larger daily snowfalls occur in associatlon with the higher 700 mb mixing ratios as would be expected. These center of mass values are higher than those observed at Climax indicating more moisture is present on the average at Wolf Creek Pass.