Agriculture Reference
In-Depth Information
Box 1.3 (
cont.
)
patterns of wind speed, direction, relative humidity and temperature and these
are not always tightly coupled. For example, Santa Ana wind flow pushes dry
hot air masses offshore for several days, but when the offshore flow ceases, the
onshore flow carries dry hot air back on land and thus high temperatures and
low humidity may persist for many days after the Santa Ana winds have
subsided ( Fig. B1.3.3 ).
360
80
270
60
Direction
180
40
20
90
Speed
0
0
80
35
60
30
RH
25
40
20
20
Temperature
15
0
15
17
19
21
23
25
27
29
31
October date
Fig. B1.3.3 Mid-day (11 am-12 pm) wind direction, wind speed, relative humidity (RH)
and temperature before, during and after the Santa Ana wind event that initiated the 2007
Witch Fire in San Diego, California, at 33 13 0 34 00 N/116 59 0 32 00 W, elevation 418 m .
(From Keeley et al. 2009b .)
In California the MTC extends along the Pacific Ocean from about 30 to 43 N.
At the southern end of its distribution in Baja California, Mexico, the common
evergreen shrublands and forests of California are restricted to upper elevations
in mountain ranges and at the northern end to drier interior parts of southern
Oregon (Rundel 2004 ). In California the MTC distribution is synonymous with
the California Floristic Province (Raven & Axelrod 1978 ), which includes plant
assemblages from the coast to the crest of the interior ranges of the Sierra Nevada.
Along this elevational and moisture gradient are plant communities that exhibit
many similarities to the Mediterranean Basin, and include some of the same
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