| Severe convective weather is characterized by small spatial scale and short duration,which often causes severe weather phenomena such as short-term heavy precipitation,hail,thunder and wind.CINRAD(China New Generation Weather Radar System)is one of the effective equipment to detect severe convective weather.And radar climatology research can help us to understand the spatial and temporal distribution and evolution characteristics of convective storms more comprehensively and provide background information and scientific basis for the nowcasting and warning of convective storms and heavy precipitation.Yan'an,located on the Loess Plateau,is a frequent area of meteorological disasters,which always causes huge losses during warm season.It is important to understand the characteristics of warm season convection for weather forecasting.In this paper,based on the data of operational Yan'an Doppler radar in the warm season(June-August)from 2013 to 2017,the convection samples within the observation range of the radar are identified and lattice dotted,and the climatic characteristics of the convection in Yan'an area during warm season are revealed from the perspective of the spatial distribution,temporal change and vertical structure of convection.In addition,combined with the ERA-Interim reanalysis data of the European Center,the characteristics of the background field of convection occurrence and its influence on the warm season convection were analyzed.According to the different convection extension height,convection in Yan'an during warm season is divided into three types: ordinary convection,deep convection and shallow convection.Distribution features of convective storms vary with different upward extensions of the storms.And the characteristics of deep convection and ground flash are compared and analyzed based on the ground flash data of Shaanxi lightning monitoring network.The results show that:(1)The convection-prone region are generally clustered or distributed in a NE-SW band shape,with two high-frequency centers located in southern and eastern Yan'an and western Shanxi.(2)The diurnal distribution is bimodal,with the maximum occurring in the early morning,and the secondary peak occurring in the afternoon.Combined with the analysis of the meteorological background field,it can be seen that the convection system triggered in the afternoon mainly due to solar heating,and the early morning convection is related to the non-thermal effects such as the night jet at the boundary layer.However,the convection in the early morning was mostly ordinary convection and shallow convection,and the convection in the afternoon was mostly general convection and deep convection.(3)Convective storms are most active in July,followed by August and less frequently in June.The main reason is that the solar heating in July is strongest.(4)Convection in Yan'an during the warm season mainly is ordinary convection,while deep convection occurs slightly less than shallow convection.In July and August,deep convection occurs frequently in mountainous areas,and the general convection and shallow convection are mostly along the Yellow River.It can be seen that deep convection activities and lightning are closely related to the terrain and mountains.(5)The development of deep convection is closely related to the emergence of ground flash.The hourly distribution of deep convection also showed a bimodal change with a weak peak in the early morning.Deep convection increased rapidly in the afternoon,convection activities were more frequent in a larger area.Comparing the characteristics of deep convective and ground flash density,it can be found that the deep convection high-frequency area and the ground flash dense area in the mountain area correspond well.Areas along of the Yellow River,deep convection activities are most frequent in July,and ground flashes are most intense in August. |
PDF Full Text Request