(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.
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