1958-2006 Precipitation Climatology for Lawrence Livermore National Laboratory Livermore Site and Site 300

摘要

This report contains rainfall climatology and analyses during the period from 1958 to 2006 for the two sites of Lawrence Livermore National Laboratory: the Livermore site and Site 300. The measurement sites are described, a regional climatology overview is provided, and the effect of topography on regional precipitation is discussed. Rainfall statistics are presented including monthly normals (30-year means) and medians; percentages of time that rainfall is less than or equal to specified amounts for given months, years, and seasons; and mean, median, and maximum numbers of days of precipitation for specified amounts by month, year, and season. The rainfall pattern is demonstrated to be typical of Mediterranean climates, with most rain falling during the cold season. Nearly 80% of seasonal rainfall occurs during November through March, with the average annual rainfall equaling 13.62 and 10.64 inches at the Livermore site and Site 300, respectively. Precipitation frequency and extreme value analyses for durations ranging from 15 minutes to 24 hours, month, and rainfall season are shown in order to estimate rainfall amounts for return periods of two to 100 years at both sites. This analysis determined 100-year return periods for largest 24-hour rainfalls of 2.49 and 2.22 inches at the Livermore site and Site 300, respectively. Historical analysis of seasonal rainfall data indicates that the wettest rainfall seasons at both sites typically occurred during strong El Ninos.