Synoptic- and meso-ƒ¿-scale processes around the Meiyu front in China at the sharp boundary of very wet and dry regions
Kuranoshin Kato (1), Shoichiro Ikeda (2)
(1) Faculty of Education, Okayama University
(2) Graduate School of Education, Okayama University
Rainfall activity in the Meiyu/Changma/Baiu frontal zone is basically
sustained by the huge northward transport of moisture from the
subtropical high area. However, the properties of the air mass or
atmospheric systems also influences greatly not only on rainfall
characteristics but also rainfall activities there.
As for the Meiyu front over the continental part of China, the air
mass to the north od the front is warm and very dry due to intense
heating from the ground over the arid region in China. The frontal- and
meso-ƒ¿-scale studies associated with the GAME/HUBEX by the authors'
group reveal that the quasi-stationary heat low around the Tibetan
Plateau, the northern part of which corresponding to the arid region in
China, sometimes contributes to the activation of the frontal-scale
rainfall activity to initiate the meso-ƒ¿-lows on the front. The
present lecture will firstly introduce such results as the GAME/HUBEX
studies.
On the other hand, moisture intrusion processes into the region to the
north of the Meiyu frontal zone seems to be also interesting. As the
preliminary study for such purpose (as a large-scale study of the LAPS
(The Lower Atmosphere and Precipitation Study)), the seasonal evolution
of the atmospheric conditions arounf the Huaihe River Basin was
examined. The specific humidity in the lower layer is very small in the
pre-Maiyu season there, although air temperature in the lower layer had
already risen at that time. In 1998, the Meiyu front passed northward
in July, but it shifted southward again to the Changjiang River Basin in
the third decade of July (the second episode of the heavy rainfall
there). It is interesting that the specific humidity was rather large
around the Huaihe to the Huanghe River Basin (31.5-40N/110-120E),
although that area was located tothe north of the Meiyu front at that
time. The stability for moist convection decreased then.
The GAME re-analysis data shows that the latent heat flux even to the
north of the Meiyu front became large after the middle of July.
Although the further studies are needed in the future, the present
results suggest the importance of memory of the Meiyu frontal rainfall
events might play an interesting role in the water cycle just to the
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