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<br />record rather than the digital database, will encounter the most-likely-erroneous four-inch <br />report. <br /> <br />3) Upper Air Analysis <br /> <br />Vertical soundings of temperature, humidity, wind and pressure in the atmosphere above <br />the ground have been taken on a regular basis at Denver and Grand Junction, Colorado, <br />for several decades. These data were analyzed as a part of this project in order to provide <br />a climatological perspective for evaluating extrc:me precipitation events occuning in or <br />near the Rocky Mountains in Colorado. This may prove very important as we move <br />toward greater utilization of numerical simulations of the atmosphere in understanding the <br />relationships between elevation, topography and magnitudes of extreme precipitation. <br /> <br />Upper air data go back into the 1940s for Colorado, but only the 1958-1992 period was <br />utilized in this study due to consistency in repOlting times and locations. Only data <br />through 1992 were easily available at the onset of this study. Prior to conducting analysis, <br />key features of vertical profiles that could explain variations of extreme precipitation as a <br />function of elevation were identified. Based upon these preliminary determinations, <br />climatological analyses of the following variable were performed: <br /> <br />. Denver and Grand Junction 0000 and 1200 UTC temperature, humidity, and winds at <br />three levels above the surface: 700 millibars (approximately 10,000 feet above sea <br />level), 500 millibars (approximately 18,000 feet above sea level) and 300 milIi.bars <br />(approximately 30,000 feet above sea level). <br /> <br />. Precipitable water in the atmosphere from the ground surface up to 700 mb and 500 <br />mb. <br /> <br />. Freezing level (height above sea level). <br /> <br />. Height above sea level and the temperature of the Lifted Condensation Level (the level <br />in the atmosphere where clouds will form if air at ground level is lifted vertically until <br />it becomes saturated). <br /> <br />For each of these variables, data for each sounding for 35 years were grouped in 10-day <br />increments from March 1 through November 30 (when nearly all extremely heavy <br />precipitation events in Colorado have occurred). Values were sorted, ranked and assigned <br />probabilities ofnon-exceedance. Figures 3-6 show examples of the resulting probability <br />distributions for Denver and Grand Junction, respectively, for each of several variables. <br />These analyses provide a valuable climatological perspective from which extreme <br />precipitation characteristics can be investigated. For example, typically temperatures aloft <br />are wannest from late June into mid August. However, maximum precipitable water is <br />limited to late July into August, but upper level winds at that time of year are normally <br />quite light. Lifted Condensation Levels (LCL) are more complex since they reIat,e to <br /> <br />10 <br />