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T250 sprd & sonde station by Mirai
[ c]
90N
1.1
1.05
1
0.95
0.9
0.85
0.8
0.75
0.7
0.65
0.6
0.55
87N
84N
81N
78N
75N
72N
69N
66N
00Z
06Z
12Z
18Z
00Z
06Z
12Z
18Z
00Z
27SEP
28SEP
29SEP
2010
40
Fig. 21.7 A time-latitude cross-section of the analysis ensemble spread of temperature ( shading )
and winds ( vectors ) during 0 UTC 27 and 0 UTC 29 September 2010. The white line and squares
indicate the track of Mirai and the observation locations, respectively
Mactan. The balloon observations contribute to the reduction in the analysis error at
D 0:7
by 25 % over the Philippines. An error reduction of 5-25 % extends from
the Indochina peninsula to the southern coast of Japan. Details will be reported
elsewhere.
21.4
Concluding Remarks
We have constructed an ensemble data assimilation system of global atmospheric
observations, called ALEDAS2, on the Earth Simulator 2. An ensemble reanalysis
data set called ALERA2 is being produced with ALEDAS2. ALERA2 provides
a smooth analysis ensemble mean and spread by replacing patches of covariance
localization with weights based on the distances from observations. The output
of ALERA2 includes various variables such as precipitation, radiative and surface
fluxes and land surface variables. ALERA2 reproduces the intensity and location
of intense precipitation associated with mid-latitude and tropical disturbances.
ALERA2, however, produces excessive weak precipitation in comparison with the
satellite-based estimation. In addition to the uncertainties in the model and satellite
retrieval algorithm, the ensemble mean operation contributes to the generation of
weak precipitation. Using ALERA2 as a reference, we have conducted observing-
system experiments (OSEs) to evaluate the atmospheric observations collected at
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