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Tuesday, June 19, 2012

LOD (AAM) and Land Surface Temperatures in California


The following discussion is based upon a WUWT post
that highlighted a paper called:

Persistence in California Weather Patterns
by Jim Goodridge - State Climatologist (Retired)
which can obtained from:

In this paper, Goodridge notes that the accumulated departure 
from average of 47 Californian de-trended temperature records
(figure 1) shows a remarkable similarity with the accumulated 
departure from the average Pacific Decadal Oscillation (PDO)
(figure 2).

Figure 1:


Figure 2:


Goodridge notes that link between the PDO and Californian
land surface temperatures is provided by the prevailing coastal
wind directions on the Californian coast that are associated 
with the rising and declining phases in the accumulated departure 
from the average PDO. 

"The accumulated departure from average plot of the PDO 
index has a peak in about 1944 as well as during the current 
period of heating starting in 1975. The rising limb of this 
PDO index represents a warming period of SST on the 
West Coast coast, where as a declining trend represents 
a time of cooling. In general, cooling on the US Pacific 
Coast occurs when coastal North winds induce offshore 
coriolis force that result in off shore winds that lower tides 
that induce cold-water upwelling. This reflects the delicate 
hydrostatic balance of the oceans. Warming SST is associated 
with South winds that induce an onshore coriolis force with 
higher tides, which suppress cold-water upwelling."

In addition, Goodridge notes that the variations in the Earth's 
Length-of-Day (LOD), a quantity that is inversely related
to the Earth rotation rate, appears to closely match the 
observed changes in the accumulated departure from the 
average PDO (compare figure3 with figures 1 & 2):

Figure 3:

The remarkable thing is that the changes in the LOD appear to
preceed those observed in the accumulated departure from the 
average PDO [and the accumulated departure from average of 
47 Californian de-trended temperature records] by about seven
to 10 years! This means that the latter are causally linked to the
former.

Goodridge provides a possible explanation for this causal link: 

"The PDO index is a measure of the East West sea surface 
temperature difference in the North Pacific Ocean. The 
AAM index [closley linked to the LOD] is a measure of the 
ratio of East West vs. North-South winds on the planet 
that affect the earth rotation rate.


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