(1) Vertical velocity
Since the beginning of June 15th, from low level to high level
had a rising area moved from west to East from Southeast Lake Baikal.
From the vertical velocity field distribution map of 850hPa at 20 o'clock
in June 15th , We could see that the largest area of the
rising movement was in the upper reaches of the Nenjiang River Basin,
which corresponded to the rainfall center. The upward movement in the upper
reaches of Nenjiang began to weaken from 20 June 16th and the Nenjiang basin
was again controlled by the rising movement, causing further rainfall
in the region in June 20th.
Compared with the actual situation, it could be seen that before the rainfall
occurred and the future rainfall area had been controlled by the ascending
motion area. Meanwhile, there was a strong upward movement near the rainfall area
in the period of heavy rainfall. Because the time of strong rising movement
was not very long in this processand it was mainly concentrated
in the Nenjiang River Basin. So the time of heavy rainfall was not very long
and the range of heavy rainfall was not very large.
(2) Water vapor flux
Generally speaking, owing to the source and strength of water vapor
through the low water vapor flux. Therefore, the high water vapor flux
of 850hPa was chosen. Near Bohai Gulf the water vapor flux began to
extend northward to the strong center at 20 o'clock on June 14th.
The northern part of Northeast China had been located at the center of
the water vapor flux, of which the Nenjiang basin was on the edge.
At this time, the southern Bohai Bay still had a large value area of
water vapor extending northward, which indicated that there was water vapor
supplementation in the south. At 20 June 17th, the west of the Nenjiang basin
had a strong water vapor flux and moved eastward and the southern part still
had water vapor supplement. In June 22nd, the water vapor flux in the
Nenjiang River Basin was reduced and the larger rainfall stage
in the rainfall process ended.