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parameterization are used in the NHM-2km experiments.
The results of verification experiments with perfect
boundary conditions produced from objective analysis data
show a quite good agreement with the observational data in
both the quality and quantity on precipitation (not shown).
Tentative comparisons between the results of the NHM-5km
and NHM-2km experiments reveal that the NHM-2km can
re-produce more detailed and realistic horizontal
distributions of rainfall in many cases (Fig. 4).
Jun Jul Aug Sep
decrease
decrease
day/month
mm/month
decrease
decrease
increase
increase
decrease
decrease
decrease
increase
Figure 3. Changes in precipitation frequencies (upper
row) and monthly precipitation amounts (lower row)
from June to September from in the present to future
climates.
Obs.
5. Summary and Future Plan
In the future climate, the frequency of rain day (> 1.0 mm
day -1 ) will decrease overall Japan, while the number of
heavy rain day (> 100.0 mm day -1 ) will increase in
western Japan in August and September and on the Pacific
side of eastern Japan in July and August.
Further experiments without any cumulus
parameterizations are conducted by the NHM-2km. Early
results prove a satisfactory performance of the NHM-2km
in precipitations.
The NHM-2km experiments is going to be conducted from
June to October for 10-25 years for the present (1990-
1999), near-future (2026-2035) and future climates (2086-
2095), respectively. Further analysis, especially on the
precipitation extremes will be planed by using the results
of the experiments.
The NHM-5km adopts the Kain-Fritsch scheme for a
cumulus parameterization. A topography-dependent
tendency in horizontal distribution of the precipitation by
this scheme is pointed out by Narita, M. (2008) and
Kanada, et al. (2008). Therefore, the improved Kain-
Fritsch scheme also has been under development.
Acknowledgements
This study is supported by the Ministry of Education,
Culture, Sports, Science and Technology under the
framework of the “KAKUSHIN” program. Numerical
simulations are performed in the Earth Simulator. The
authors are grateful to “KAKUSHIN-3” modeling group
for carrying out the project.
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