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*:/ : 11-1 h WA <br />Air Quality and Greenhouse Gas Background and <br />Modelina Data <br />AIR QUALITY <br />Climate/Meteorology <br />SOUTH COAST AIR BASIN <br />The project site lies in the South Coast Air Basin (SoCAB), which includes all of Orange County and the <br />non -desert portions of Los Angeles, Riverside, and San Bernardino Counties. The SoCAB is in a coastal plain <br />with connecting broad valleys and low hills and is bounded by the Pacific Ocean in the southwest quadrant, <br />with high mountains forming the remainder of the perimeter. The general region lies in the semi -permanent <br />high-pressure zone of the eastern Pacific. As a result, the climate is mild, tempered by cool sea breezes. This <br />usually mild weather pattern is interrupted infrequently by periods of extremely hot weather, winter storms, <br />and Santa Ana winds (SCAQNID 2005). <br />Temperature and Precipitation <br />The annual average temperature varies little throughout the SoCAB, ranging fiom the low to middle 60s, <br />measured in degrees Fahrenheit ff). With a more pronounced oceanic influence, coastal areas show less <br />variability in annual minimum and maximum temperatures than inland areas. The climatological station <br />nearest to the project site with temperature data is the Santa Ana Fire Station (ID No. 047888). The lowest <br />average temperature low is reported at 43.VF in January while the highest average temperature high is 84.7°F <br />in August (WRCC 2018). <br />In contrast to a very steady pattern of temperature, rainfall is seasonally and annually highly variable. Almost <br />all rain falls from October through April. Summer rainfall is normally restricted to widely scattered <br />thundershowers near the coast, with slightly heavier shower activity in the east and over the mountains. <br />Rainfall averages 13.69 inches per year in the project area according to the data from the Santa Ana Fire <br />station (WRCC 2018). <br />Humidity <br />Although the SoCAB has a semiarid climate, the air near the earth's surface is typically moist because of the <br />presence of a shallow marine layer. Except for infrequent periods when dry, continental air is brought into <br />the SoCAB by offshore winds, the "ocean effect" is dominant Periods of heavy fog, especially along the <br />coast, are frequent. Low clouds, often referred to as high fog, are a characteristic climatic feature. Annual <br />average humidity is 70 percent at the coast and 57 percent in the eastern portions of the SoCAB (SCAQNID <br />2005). <br />75C-138 <br />