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Fig. 23.2
Ensemble mean forecast initialized at 0600 UTC November 9, 2009 of a decaying mid-
latitude cyclone making landfall on the North American coastline valid at (
a
) 00-h, (
b
) 12-h, (
c
)
18-h, and (
d
) 24-h. Black contours represent sea-level pressure (contour interval is 2 hPa),
blue
contours
represent 925-hPa temperature (contour interval is
2
ı
C), and
wind barbs
represent 10-m
winds
alter the cyclonic wind field flowing around the cyclone. Magnitudes of the variance
reduction field are largest for pressure (reaching just over
hPa
2
/
1:4
, are slightly less
hPa
2
/
for the wind field (reaching about
1:2
, and are smallest for the temperature
hPa
2
/
field (reaching about
.
One interesting and unique feature of the targeting regions based on pressure in
Fig.
23.3
is that they are less localized and show some impact away from the center
of the system. Although values in these more distant regions are not as large as
those in the immediate vicinity of the cyclone, they clearly highlight features in the
flow at analysis time. Both the frontal trough near
0:9
40
ı
N,
130
ı
W and the large
oceanic region of high pressure in the western portion of the domain are shown to
be relatively important. In tune with the discussion of
Ancell and Hakim
(
2007a
),
these features are highlighted as targets because they reveal areas where analysis
increments would project substantially onto regions of large dynamical sensitivity
(a quantity estimated through adjoint sensitivity analysis). This in turn reveals a
defining characteristic of observation sensitivity over that of adjoint sensitivity—
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