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<br />-27- <br /> <br /> <br />I'l:'\~.,... <br />UU_1.""~;) <br /> <br />diminished temporarily. Such events may be presumed if there are erratic <br />differences among the catches of adjacent gages. In general, reported <br />catches of snow could be mistrusted whenever they exceed 50 percent of <br />gage capacities. <br /> <br />Snow density.--On occasion, an observer may record the depth of new- <br />fallen show instead of melting a sample and recording the water content. <br />In such cases, the published precipitation amount is sometimes estimated <br />by assuming a density of 0.10 for the new-fallen snow (one inch of snow <br />equals 0,10 inch of precipitation). Such estimates now are identified in <br />"Climatological Data" by a footnote, "D". Some of the earlier publications <br />did not identify these estimates, which could be disclosed only by exam- <br />ining the original records. The l-to-lO rule can be considerably in <br />error for some storm,periods. <br /> <br />Minimal amounts of precipitation.--At substations, hours may elapse <br />before the precipitation catch in a light storm is measured on-the once- <br />daily schedule. During that interval an appreciable portion of the catch <br />may be lost due to evaporation. First-order and recording stations have <br />shown a greater frequency of days with precipitation :>0.01 inch than <br />stations that measure only once a day. <br /> <br />Unnoted change in location of station.--As will be treated at greater <br />length, a change in location of a station may divide a precipitation <br />record into parts that are not consistent one with another, If the <br />changed location is overlooked or is not of record, a substantial error <br />may result. <br /> <br />Recordint gages at remote stations.--At high altitude, remote sites <br />where precipi ation may fall as either rain or snow, and where several <br />months may elapse between servicing, presently available recording gages <br />commonly fail to operate continuously. Consequently there are serious <br />gaps in knowledge of short-term precipitation rates at such sites, with <br />resultant possible errors in interpretation. <br /> <br />Hour of observations <br /> <br />Care must be used in comparing or correlating precipitation data <br />from station to station, or in computing the precipitation over a given <br />basin during a particular time interval. Amounts of daily precipitation <br />as published in "Climatological Bulletins" under a given date may not be <br />for the same interval of time; the hour of observation is listed in the <br />bulletin. Thus, at first-order Weather Bureau stations that are equipped <br />with recording gages, amounts of daily precipitation are determined on <br />the midnight-to-midnight basis. At substations, however, the daily <br />amounts are generally from once-daily readings of the gage--commonly near <br />sunset or early in the morning but neither strictly at 24-hour intervals <br />nor at a common hour among all the substations. Thus, for storms of <br />short duration or of highly variable intensity, amounts of precipitation <br />recorded under a particular date might differ substantially among a group <br />of stations whereas the actual amounts were essentially equal and <br />