Evolution And Structure Of Deep Convective Clouds In Central And Western Huanghuai Region

Satellite multi-channel products and deep convection indentification technology are used to investigate the evolution and synoptic significance of deep convection clouds, as well as the spatial and temporal distribution, life history and the scale features of the Meso-scale Convective System (MCS) in central and western part of Huanghuai region. Based on statis-tical analysis, a variety of conventional and unconventional data, along with the products from radar 4DVar inversion and WRF model are comprehensively utilized. Mesoscale analysis, synthesis analysis, diagnostic analysis and numerical simulation techniques are used to carry out classified studies on MCS, including the development and movement of different types of MCS, synoptic features of deep convection, as well as the structural features and formation mechanism of typical MCS, as so as concept models of MaCS. Some meaningful findings have been achieved.The spatial distribution of deep convective clouds in central and western part of Huanghuai region is obviously affected by climate and terrain, with different synoptic significance of deep convection activities in different region. Monthly variation of deep convection has the features of fluctuating, north proceeding and south retreating. Diurnal variation of unimodal deep convection in northern Henan has a thermal convection feature, showing to spread southeastward. Diurnal variation of bimodal deep convection along and south of the Huaihe River is obviously controlled by the synoptic system. MCS has its own geographical features, and can be divided into round MaCS, MPCS, and ribbon MaCS, MβCS. Occurrence and disappearance, monthly variation, and development of different types of MCSs show different characteristics. Altitude diverge areas are major wind field environment for MCS development. Except ribbon MPCS, all the other three types of MCSs could result in strong precipitation of 80 mm/h or more, and precipitation intensity has little relationship with the scale of the system. Strong convective weather as thunder storm winds and hail is more likely to appear in ribbon convective systems.At the initial stage, MCSs show as y or P-scale convective cells or multi-cell storms on the radar. At the mature stage, convections merge frequently and the patterns are complex. Linear convective systems often appear at mature stage. The mergence of convections is closely related to the mergence of low-level dynamic fields. The convective weather is most obvious during the occuring and strongly developing periods of the system. Low-level southwest jet provides necessary moisture and energy for the formation and development of MaCS. Dry cold air invasion and mid-low-level warm and humid air forcing provide convection with triggering conditions.Southwest jet for the formation of low-level development MaCS provide the necessary moisture, energy, and strong low-level warm air in forced convection trigger conditions provided. The width and direction of jet convergence area, and the distribution or morphological characteristics of low-level shear line (trough), vortex and humid area (relative humidity above 80%) determine the form of the MCS. There is usually no low-level jet during the development of MβCS. Convergence line or dry cold air invasion is the trigger condition for its formation and development.For all the typical cases, all the MCSs form under the condition of high CAPE (above 1 OOOJ/kg). Differences in the structure of the wet zone and vertical wind shear cause the difference in strength and types of strong convective weather. For the environment of low-level trough(shear)-types MaCS, the K-parameter, precipitable water (PW), vertical wind shear and SWEAT index are higher. But for the The subtropical high edge-type sound MaCS, the CAPE,θse85, SI index are higher. The apparent backward development of ribbon MaCS results from the propulsion from cold air. Different types of MCS in different developing stages, as well as different parts of the MCS have different dynamic and thermal structures, along with different convection triggering mechanisms. Higher CAPE in middle PECS, low-level wind shear between 0-2 km, and stronger weather threat index are in favor of heavy rainfall. Higher 0-6km vertical wind shear in the tail, higher θse85, and lower LI (-6.1) is beneficial for thunderstorm wind generation. The MβCS environment has roughly similar development and morphology characteristics, but there are differences which could leading to different convective structure and convective weather. When convergence layer and PW are larger, and the 0℃ layer is higher, heavy rain often appears. When the convergence layer is lower and thinner, or when the dry and wet layers distribute alternately, strong wind and hail convection often appears. Initial convection usually develops in the high energy tongue, or on the northwest side, at the forefront of energy front. The invasion of low-level dry cold air make the system intensify. For the strongly developed MaCS, there are often mid-low level convergence and thick positive vorticity area. And the upper-level divergence is strong, with vertical upward movement extending to the tropopause from the boundary layer. Ground meso-cyclone disturbance and convergence line not only could trigger the convection, but also could organize the convection. The center of meso-cyclone disturbance corresponds with the bright temperature center of the system.Numerical simulations of low-level vortex shear-type MCC show that, during the developing stage, when the latter developed cells get closer to the former developed cells, they will merge and convection will develop in the middle level first. At the same time, the vertical upward movement would become stronger. The latter developed cells would develop stongly, and the former developed cells would decay. The sensitive experiments suggest that terrain had a significant impact on the development, precipitation intensity and zone.