Comparative Study On The Process And Mechanism Of Jianghuai Cyclones Developing On The Sea Between Warm And Cold Season

The jianghuai cyclones which develop on the sea from 2008 to 2012 are statistically analyzed, and according to the different depth of cyclones and their season characteristics, they can be divided into four categories:warm season deep type, warm season shallow type, winter shallow type and early spring bottom type. Respectively, basic statistical characteristics of different types of jianghuai cyclone are analyzed. Then using synthetic analysis and synthetic diagnosis to analyze the relative importance of environmental factors in the development of jianghuai cyclones on the sea. Finally, WRF model for numerical simulation is used to study the SST influence to different types of jianghuai cyclones and its weather characteristics when they develop on the sea. The results showed that:(1) There is a declining trend in the frequency of jianghuai cyclones year by year,and there is not obvious interannual variability of cyclones on the sea. Overall, jianghuai cyclones are a kind of relatively shallow low system, and they are relatively deep in summer and late spring and shallow in winter and autumn. Jianghuai cyclone activity paths to the sea can be divided into two:the east and the northeast roads, and the cyclones of early spring bottom type are all the northeast road and the other paths of various kinds of cyclones have occurred. The position of jianghuai cyclones develop on the sea in winter is north than in early spring, and cyclones increase more than in summer. (2) The jianghuai cyclones’weather is strong winds and precipitation. For different deep cyclones, the underlying surface friction reducing enhances cyclone wind area size and the areas move to southeast part of the cyclones when they develop on the sea, the strong wind area also appears at the back of cyclones of early spring type and correspond with the underlying surface temperature cold tongue. The precipitation intensity of cyclones in summer significantly increased on the sea and more precipitation increment of deep cyclones, precipitation area in the north cyclone. The precipitation increases slightly in winter and early spring and precipitation area in the east ar southeast to cyclone. The main rain area of all kinds of cyclones are in conformity with the vapor flux convergence center at 1000hPa and the upward movement at 850hPa. Condensation latent heat releasing is a important impact factor for summer cyclones and is proportional to the deep degree of cyclones, but it’s not the main physical factors to early spring cyclones when develop on the sea. The vertical stretch of early spring type cyclones’positive vorticity area are more significant than other type, and the influence of the thermal and dynamic effect is more obvious. (3) the surface diabatic heating is conducive to cyclones’enhanced development on the sea, and have significant implications for cyclones’precipitation distribution. The downward transport of high level jet momentum and less underlying surface friction increase various kinds of cyclones on the sea, and the downward transport of high level jet momentum is directly proportional to the depth of cyclones. The warm advection at the front of cyclones in summer and winter enhanced the development of cyclones on the sea, and more enhanced warm advection is the main factor to the development of cyclones in winter. The frontal position and its intensity of the MPV2 of the Moist Potential Vorticity at 1000hPa significantly indicate the intensity and position of rainfall in the cyclones. Low-level SRH has significant effect to the development of cyclones on the sea and early spring cyclones are more sensitive to the dynamic effect of low-level SRH because of its shallow depth. (4) The results of numerical simulation shows that there is no significant difference among the paths of jianghuai cyclones which develop on the sea because of the increase or decrease of SST, but it very obviously impacts cyclones’intensity, reducing SST decrease cyclone intensity and higher SST increase cyclone intensity, and when SST changes same, the degree of warm cyclones intensity change faster than the cyclones in winter. The development mechanism is different between warm and winter cyclones, underlying surface latent heat transfer and the heavy rain is the important physical effects during warm cyclones development on the sea, and the sensible heat transfer is the important mechanism of cyclones in winter. The latent heat and sensible heat and precipitation changes near the cyclone center are not obvious when SST changes in early spring, so the cyclone intensity changes are not significant. SST increase or decrease influenced the precipitation of warm and winter cyclones significantly, but the influence of the early spring type cyclones are not obvious.