Chapter 3 - Natural Resources - Marine Corps Base Camp Pendleton

CHAPTER 3
NATURAL RESOURCES
3.1. PHYSICAL ENVIRONMENT
3.1.1. Climate
The Base has several climatic zones that roughly coincide with the three geomorphic
regions present: coastal plain, coastal valley, and mountain. In general, the Base has a
semiarid Mediterranean climate with warm, dry summers and mild, wet winters. Daytime
temperatures rarely exceed 95 ◦ F in the summer, and nighttime temperatures usually remain
above freezing in the winter.
Seasonal rainfall along the Base’s coast averages between 10 and 14 inches per year.
Average annual precipitation in the mountains on Base varies between 20 and 40 inches,
depending upon slope and elevation. Approximately 75% of the Base’s precipitation falls
between November and March, with the greatest annual average precipitation in January.
Winds generally originate from the west or southwest, carrying in cool, moist offshore air.
Night and early morning overcast is common on Base throughout the spring and summer.
Low clouds frequently extend inland over the coastal foothills and valleys but usually
dissipate during the morning. Afternoons are generally clear. Coastal fog averages 29 days
per year, being heaviest during the fall and winter months.
An important characteristic of local weather is its year-to-year variability. The native
vegetation is adapted to periodic drought, flooding, and fire. “Fire season” occurs from
May through November, with extreme fire conditions occurring when very dry, warm
“Santa Ana winds” blow and there is a heavy fuel load of dry vegetation. Camp
Pendleton’s geography creates up-canyon winds because its northeast-southwest trending
canyons are able to pull in marine air each day as land surfaces heat-up. At night, the
breezes are pulled back down-canyon and seaward as land surfaces cool (MCBCP 1992).
Local weather data is collected from six stations on Base: Case Springs, San Mateo Canyon
at Tate Grade, Cristianitos, Las Flores, Lake O’Neill, and Range 408. The Cleveland
National Forest (El Carrizo Station) and the National Weather Service (Oceanside and San
Clemente) also maintain records.
The current global warming trend is anticipated to produce longer-drier summers, and
shorter-wetter and more intense winters in the Southwestern U.S., with extreme weather
events potentially rapidly degrading existing habitats. The distribution of species within
ecosystems is predicted to shift along with increasing temperatures to new suitable habitats,
especially in bird species which inhabit scrub-chaparral habitats, resulting in new
combinations of species within habitats that usually do not interact, which will
Chapter 3 – Natural Resources 3-1