| Severe convective weather is characterized by its small scope,short life span,intense intensity,and great destructiveness.In particular,its intensity has the characteristics of rapid increase and rapid decline.Therefore,the effective time for observation and recognition is short,which has been making it difficult to monitor and predict.Currently,weather radarsare the primary and effective means for local monitoring and forecasting of medium-and small-scale strong convective weather,with their high-precision time and space resolution,refined remote sensing capabilities,and the overall display of local three-dimensional situations.The basic products include reflectivity,radial velocity,and velocity spectrum width,and this article will focus on the numerical information extraction of radial velocity.For the severe convective weather in the spring and summer seasons,the radial radar field-based data of the weather radar are used to extract the quantitative information contained in the numerical characteristics.Based on these quantitative information,several strong convection indicators are constructed and applied to different regions and types of Doppler radars,and results are good.The main information provided by the radial wind field is convergence or divergence of radial velocity and radial wind direction,cyclonic or anti-cyclonic shear of radial wind.Because conventional characteristics of vorticity and divergence describe the features of large-scale circulation wind fields better than those of small-scale local wind fields,because small disturbances in the local wind field interfere the radar detection and affect the expression of radial wind characteristics,which leads to fragmentation of vorticity and divergence.Therefore,stream function and velocity potential are introduced to describe the basic rotational features and convergent or divergent state of the radial wind field on the body scan surface.The expression of the stream function and potential function is obviously better than the direct distribution of vorticity and divergence.Using the stream function and potential function with good expression of regional flow field characteristics,and adopting appropriate boundary conditions and calculation processing schemes,the Poisson equation is used to iteratively determine the special solution that satisfies the regional nondivergentcondition.Moreover,the radial wind field is reconstructed by inverse operations and its effect is tested through statistics,which shows that the regional stream function and velocity potential solved by the used boundary treatment scheme are convergent and the basic characteristics of the radial wind field are well expressed.Secondly,using the quantitative information of radial velocity's stream function and velocity potential and their close relationship with local strong convection,the spatial-temporal early-warning index equation of regional strong convection is builtand based on the indicator,fine-precision early alert locations and time evolution features of radial wind field are provided.In addition,given that radial wind convergence line is often the feature of local rainstorm,a method of objective automatic recognition of radial wind convergence line is developed using matrix conversion technology.It can provide quantitative information such as geographical location,scale,trend,distribution,coverage,and dynamic tracking of radial wind convergence lines.Further,the radial wind convergence line is superimposed with the radial wind quantitative information background field to achieve multi-indicator comprehensive alert,which can more finely reflect the spatial-temporal characteristics of the localized strong convection medium and small-scale systems.In order to enhance the full application of radial wind information,new ideas and a variety of effective early warning methods are provided.This article provides new ideas and kinds of effective alerting methods on enhancing the full application of radial wind information. |
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