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<br />, <br />;; <br />, <br />, <br />, <br />, <br />,/,//\R,o.88 <br /> <br /> <br /> <br />o u/'~ Only .o.l~mm/h <br /> <br />. ,". BEST FITS <br />, <br />" . all data <br />, <br />, <br />SO' <br />, <br />, <br />o ,,,' · <br />o " <br />, <br />. ' <br />. ....', <br />..II.. <br />. <br /> <br /> <br />sodes were linked to 70-kPa winds from the south or south- <br />west, while only 3 episodes were concomitant with northerly <br />or northwesterly winds. <br /> <br />The vertical motions associated with the upper-air features <br />frequently combined with orographically induced motions to <br />produce substantial SLW episodes. In the absence of the <br />troughs and lows, significantly less or no SLW was observed. <br />Infrequent exceptions to this were some convective cases, <br />which were observed in the absence of significant winds or <br />upper-air features. Momentary peaks of SLW near 1 mm <br />were occasionally recorded; however, hourly averages in such <br />cases were invariably an order of magnitude less. <br /> <br />Often, when parameters were at or near the values required <br />for SLW production, little or no SLW was detected by the <br />radiometer. Precipitation records from a nearby gauge were <br />examined, only to find that many of these "enigmatic" cases <br /> <br />1.1 <br /> <br />1.0 <br /> <br />PRECIPITATION RATE <br />o sOJ5 mm I h 1501 <br />. >0.15 mm I h 18601' <br /> <br />E <br />E 0.9 <br /> <br />cc <br />w 0.8 <br />t- <br />et <br />~ <br />o <br />- <br />::> <br />o <br />..J <br /> <br />0.7 <br /> <br />0.6 <br /> <br />0.5 <br /> <br />o <br />W <br />..J 0.4 <br />o <br />o <br />u 0.3 <br />CC <br />w <br />~ 0.2 <br />CJj-- <br />0.1 <br /> <br />.. <br /> <br />. <br /> <br />0.0 <br />0.0 <br /> <br />were periods of significant, or even heavy, precipitation. On <br />plots of hourly averages of SL W versus cross-barrier wind <br />flow (fig. 2-1), variability was greatly reduced by excluding <br />periods when precipitation rates atop the Mesa exceeded <br />0.15 mm/h. A large number of hours, during which little <br />SLW was observed concomitant with significant cross-barrier <br />wind, were thus eliminated from the plots. However, over <br />50 percent of the high SLW data was also eliminated, which <br />demonstrates that much SLW was often present even during <br />periods of significant natural precipitation. <br /> <br />f-' <br /> <br />Rauber, et al. [8], found that, in the Park Range of the north- <br />ern Colorado Rockies, intense storm periods with heavy pre- <br />cipitation had little liquid water. This appears at times to <br />also be true over the Grand Mesa; however, the large number <br />of exceptions implies that, unlike Park Range, significant <br />SL W may exist during some periods of heavy natural pre- <br />cipitation. <br /> <br />. <br /> <br />o <br /> <br />o <br /> <br /><9 <br /> <br />. <br />. <br /> <br />. <br /> <br />.. <br /> <br />o <br /> <br />. <br />o <br /> <br />, -I <br /> <br />. <br /> <br />10.0 <br /> <br />12.5 <br /> <br />Figure 2-1. - Production of SLW. Production, as a function of wind speed, measured 7(}m a.g.!. on Grand Mesa multiplied by precipitable water <br />In the 65- to 75-kPa layer, as measured by Grand Junction rawlnsondes. Correlation Improved when hours having precipitation greater than <br />0.15 mm were excluded. Note that about half the cases of SLW greater than 0.4 mm were excluded when only light precipitation cases were <br />considered. <br /> <br />6 <br />