Study On Wind Field Retrieval And Gale Warning Near The Surface Based On Doppler Weather Radar

The gale which includes the tornado and typhoon is the strong wind with force 8(average speed 17.2m/s)or more near the surface.It can cause the great disasters and secondary disasters to the people's production and life.The Doppler weather radar depending on the Doppler Effect to detect atmospheric velocity is one of the effective tools to monitor and track the weather phenomenon from meso-micro scale atmospheric structure filed.In order to analyze the wind structure and launch gale warning,the wind field should be established by using the velocity data of the Doppler weather radar.And the warning platform can be established effectively by using The Geographic Information System(GIS)to locate the gale accurately.This warning platform can help us to understand the wind spatial and temporal characteristics in the gale warning mode.And the gale warning information can be gave out accurately and timely.The study indicates that the fixed azimuth on wind field retrieval has limited the grid resolution of wind field.At different distance from the radar,the problem of result aliasing or inability to retrieve the wind field will occur.When the radar wind field has been applied and analyzed in combination with geographic information,there will be obvious location deviation at the far-range echo of the radar due to the influence of earth curvature,radar detection factors and atmospheric refraction.In the data merging from radar data(wind field information)to geographic information,merging processing and data calculating are difficult due to the large capacity of the radar echo data.Focusing on the above three problems,firstly,the study on the wind field retrieval algorithm of the grid is carried out based on the existing relevant studies.This algorithm can build an accurate wind field structure and improve resolution of wind field.Secondly,the projection method of radar data is proposed to establish the accurate location between wind field information and geographic information.The method of multiple-source data fusion is studied to establish the comprehensive data framework of the gale short term forecast and early warning platform.These studies can ensure the accuracy and timeliness of the short-impending wind forecasting.The research contents and results are as follows:(1)Based on Doppler radar,the Multi-resolution and Velocity Vector Average Processing(MVVAP)algorithm is proposed to retrieve the wind filed and establish the gale field structure.The characteristics of the algorithm is that tangent distance corresponded by radial angle on the maximum non fuzzy distance is used as the minimum resolution of the grid.It can ensure the data integrity in the distal grid and avoid the wind field aliasing.The different resolutions are used to enhance the proximal multiple radial vector average velocity processing.Then,based on the idea of velocity-azimuth processing(VAP),the wind field is retrieved successfully.This method can keep the real condition of the low-altitude atmospheric flow field and improve the spatial resolution of wind field retrieval effectively.(2)Based on the idea of location and matching by longitude and latitude,the Concentric Projection(CP)method is proposed to solve the accurate locating radar data with the geographic information.It can improve the location accuracy and support the data fusion calculation.This method improves the reliability and accuracy of short-term wind forecasting based on geographic information.(3)The volume echo data of radar is too large to be integrated into GIS.The data reverse-fusion data is proposed to use the radar data and geographic more effectively.Because the radar data format is simple and the structure can be modified easily,a new data structure can be established to integrate the geographic data with the radar data based on the radar data structure.The coordinate and attributive geographic data are extracted through JAVA program.The relational database is used for data transmission.The radar data,geographic information and gale warning information are all stored in binary files.The integrated data has portability.The arithmetic speed is enhanced on the third-party platform programming.(4)According to the national early warning standard,two warning mode are proposed.The basic four level warning mode is used for high wind speed warning such as tornadoes and typhoons.By adding the geographic disaster warning data and adopting the integrated warning mode from 0 to 17 degree,it can adapt to the application requirement on different geo-spatial environments and improve the flexibility of gale warning.(5)The wind field retrieval is extended to study on use of the radar reflectivity.The results of the Vertically Integrated Liquid(VIL)method verify the result of early warning.Based on the velocity and azimuth displaying method and the storm tracking algorithm,the position and range of the echo are calculated at the adjacent time.The movement direction of echo position can represent the direction of wind.The off-field wind push model is established to predict the occurrence and development of the gale.The innovative points are as follows:(1)In the wind field inversion with grid,a method is proposed to obtain the retrieved velocity data with different azimuth and angle resolutions in different grids.The wind field structure is standardized and the requirement of mesoscale retrieval is guaranteed.(2)A method is proposed to merge geographic information data with radar data.The computation of data fusion is reduced and the speed of fusion and data reproduction has increased.Wind field retrieval,data location and fusion,and early warning mode are important components of short-time ground wind prediction and gale warning.Further in-depth analysis should be needed on the adaptability of different bands radar.In multiple source data fusion,the means and methods of extracting geographic data still need to be optimized.In the future,the application of multiple Doppler weather radar in threedimensional wind field retrieval to improve the spatial and temporal effect of short-time gale prediction has broad study space and extensive significance.