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<br />In the northern Colorado River Basin, there is a <br />substantial daily peak in both frequency and amount <br />of precipitation between midnight and 6 a. m. <br /> <br />Daily temperature fluctuations at the higher <br />mountain areas is frequently as. great as 100 F even <br />on days of heavy snowfall. <br /> <br />2. Upper Air Climatology <br /> <br />a. Upper air climatology as related to daily <br />snowfall events <br />An upper air climatology of natural <br />, daily snowfall has been prepared for Climax, <br />Colorado, utilizing the non-seeded days of the ran- <br />domized experiment between 1960-65 and for the San <br />Juan Mountains using the unseeded winter seasons <br />of 1965-66 and 1967-68. This study considers the <br />frequency of occurrence and contributions to the <br />total snowfall within various classes throu~h the <br />range of the meteorological variables. The param- <br />eters chosen for this investigation are related to <br />orographic influences, available moisture supply, <br />air mass stability, and cloud system temperatures. <br />The variation of the mean daily snowfall is also <br />determined as a function of the meteorological <br />parameters. <br /> <br />!!! <br />~-6 <br />..~~ <br />~~ <br />II Z-4 <br />,~lr <br />.~~ <br />'<i~2 <br />.~~ <br />~~o <br />!!! <br />~ <br />~~6 <br />.~~ <br />~~4 <br />'O~ <br />'U..J <br />.'<i~ 2 <br />.~~ <br />~~O <br /> <br />'(1) Daily snowfall related to cloud top <br />temperatures <br />Figure 37 shows the natural mean <br />daily snowfall as a function of cloud top <br />temperatures (500 mb) for Climax, Colorado. <br />The lower diagram (b) is constructed by <br />utilizing a running mean containing a two.. <br />degree interval of temperature while the top <br />diagram (a) consists of a mean computed over <br />a four-degree class interval. <br /> <br />~6 <br />..J <br />..J <br />iiI: <br />~ 4 <br />VI <br />~ <br /><i' ,2 <br />o <br />z <br />ex <br />llJ <br />::;: 0 <br /> <br />(0 ) <br /> <br />--___C:T~:TIAL CONDENSATE <br /> <br /> <br />..., ,6 <br />Z <br /> <br />..J <br />~ <br />~ 4 <br /> <br />-.......--...... <br />----__ _R1TENTIAI C-ONDENSATE <br />-----f..._____ - <br /> <br />( b) <br /> <br />~ <br />8 2 <br />~ <br />llJ <br />::;: O' _~ <br /> <br /> <br />--' ' <br />-38 <br /> <br />-14 -18 -22 -26 -?n <br />500 MB TEMPERATURE ('C) <br /> <br />-34 <br /> <br />Figure 37. --Solid Lines: Mean Daily Snowfall at <br />Climax, Colorado, as a function of the cloud top <br />temperature (500 rob). Dashed Line: Adiabatic <br />condensate realized from lifting a parcel upward <br />through a saturated 700-500 mb layer. <br /> <br />A peak in the mean daily snowfall <br />appears in the - 21 0 C to - 240 C class interval <br />while the running mean indicates a peak around <br />-200 C to _210 C. Daily snowfall decreases at <br />both colder and warmer cloud top temperatures. <br />The decrease of mean daily snowfall at the <br />colder cloud temperatures follows very nearly <br />the trend of the potential condensate in the 700 - <br />500 mb layer. At the warmer cloud tempera- <br />tures, however, the decrease in snowfall above <br />_200 C is quite marked and occurs in spite of <br />the increase in potential condensate <br /> <br />A small secondary peak is noted in <br />the mean daily snowfall arcund _140 C to _150 C <br />(Figure 37, diagram a). <br /> <br />The histograms of Figure 38 show how <br />the total snowfall and the total occurrences are <br />distributed with respect to the 500 mb tempera- <br />tures. The histograms are generated utilizing <br />4 -degree class intervals. It is seen that about <br />42% of the total snowfall and 35% of the total <br />occurrences are contained in the class interval <br />from -20.50 C to -24.50 C. <br /> <br />Figure 39 shows the natural mean <br />daily snowfall as a function of cloud top tempera- <br />ture (500 mb) for the pooled Wolf Creek Summit <br />and Wolf Creek West recording gages. The <br />lower diagram (b) again is constructed utilizing <br />a running mean containing a two-degree interval <br />of temperature while the top diagram (a) <br />consists of a mean computed over a four-degree <br />class interval. <br /> <br />A peak in the mean daily snowfall is <br />ev-ident at around - 23 0 C. As cloud temperatures <br />become colder the average snowfall decreases <br /> <br />!!! <br />~ <br />~~ <br />llJ"'" <br />!:i~ <br /> <br /> <br />~~l g j' <br />z~ ~ <br />8..J ~_ <br />II> ' fa <br /><i::;: 2 ~ :r ,2 <br />;::Q <i'~ <br />z/rl 0:::; <br />~t:!8 z <br />... ex <br />llJ <br />::;: <br /> <br />-...._- <br /> <br />(a) <br />----___....---P0TENTIAL alNDENSATE <br /> <br />---------------- -- <br /> <br />---.... <br /> <br /> <br />( bl <br /> <br />10 <br /> <br />r----- 1 <br />: :'PERCENTAGE OF TOTAL <br />I 1 SNOWFALL <br /> <br />llJ <br />C> <br />i'! <br />z <br />~ <br />It' <br />~ 5 <br />!;i <br />..J <br />~ <br /> <br />-----, <br /> <br /> <br />FREQUENCY OF <br />CX:CURRE NCE <br /> <br />o -10 -14 -18 -22 -26 -30 -34 -38 <br />500 MB TEMPERATURE (OCl <br />Figure 38. --(a) Mean Daily Snowfall at Climax as a <br />function of cloud top temperature (500 mb). <br />, (b) Distributions of total snowfall and total occur- <br />rences as a function of cloud top temperature (500 mb). <br /> <br />53 <br />