Geoscience Reference
In-Depth Information
Table 21.2
A comparison of the configurations of ALEDAS and ALEDAS2
ALEDAS
ALEDAS2
AFES version
2.2
3.6
Resolution
T159L48
T119L48
63
C
1
Ensemble size
40
Covariance localization
21
21
13
400 km/0.4ln
p
Spread inflation
0.1
Observations compiled by
JMA
NCEP
The ensemble size is increased from 40 to 63. Control runs are conducted from the
analysis ensemble mean. The localization length is 400 km in the horizontal and
0:4
in the vertical. The spread inflation of 0.1 has not been changed.
For ALERA, the observations used for the global NWP at JMA were provided
under the collaboration. For ALERA2, a less restricted PREPBUFR compiled by
the National Centers for Environmental Prediction (NCEP) and archived at the
University Corporation for Atmospheric Research (UCAR) is used. The number
of the observations is reduced as follows. For weather balloons (ADPUPA), the
data used are at 1,000, 925, 850, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50 and
10 hPa. Reports from aircraft and satellite retrievals are trimmed to one in every four
values and wind profilers to one in every three levels (
St-James and Laroch 2005
).
NOAA (National Oceanic and Atmospheric Administration) daily
ln
p
1=4
ı
OISST
(optimal interpolation sea-surface temperature) version 2 (
Reynolds et al. 2007
)is
used to provide ocean boundary conditions with a higher resolution in both time
and space. The initial conditions are prepared from the AMIP (Atmospheric Model
Intercomparison Project)-type integration for 20 years. The integration is performed
with AFES at the same resolution (T119L48). Ensemble members are arbitrarily
chosen to be the atmospheric states of a particular date and nearby dates from
different years.
The second generation of the Earth Simulator (ES2) updated in March 2009 is
used to conduct ALERA2 and OSEs. Each ensemble forecast is performed on a
single vector processor. Each node hosts 8 processes (members), and a total of 64
processes are used on eight nodes of ES2.
21.3
Data Assimilation Experiments
Currently, three streams have been conducted as ALERA2:
•
Stream 2003: from 1 June 2003,
•
Stream 2008: from 0 UTC 1 January 2008,
•
Stream 2010: from 1 August 2010.
Stream 2003 aims to produce a data set that is as long as possible temporally.
Stream 2003 began at the earliest continuously available time in the PREPBUFR
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