Detection Analysis Of Sandstorm And Precipitation Process Based On Wind-profiling Radar

Using the boundary layer wind-profiling radar we did the detection experiment study on the processes of sandstorm, rainfall and snowfall. The emphasis is put on the analysis of the echo signal and velocity power spectrum distribution during the process of sandstorm, and the observed wind data in the process is evaluated as well. The echo intensity value range of sandstorm is calculated and summarized and the high-level particle number concentration and mass concentration of sandstorm is quantitatively inversed and estimated. In addition, from the perspectives of wind detailed analysis, frontal system identification, temperature advection inversion, echo intensity, etc., we investigate the technical method of applying the high resolution wind profiler data to the rainfall (snowfall) weather analysis in arid areas. The main conclusions are as follows:(1) When the CFL-03boundary wind-profiling radar works in dry sandstorm weather, atmospheric refraction index is small, turbulence echo signal is weak, but the sand particle group produces strong backscatter to the electromagnetic wave. The wind-profiling radar mainly identifies the returning signal of sands, ignoring the scattering echo signal of atmospheric turbulence.(2) Effective data acquisition rate of the CFL-03radar is low during the process of sandstorm. The effective data acquisition rate can go over40%under2,000m height, ranges within20%-40%between the2,500-4,000m height and lower than20%above4,000m. One critical factor that impacts the wind-profiling radar to detect wind effectively is the dry atmosphere and low relative humidity. The result that RASS system detects the virtual temperature during sandstorms is not so ideal, and the effective detected height is mostly lower than500m. The important cause for the unsatisfactory temperature observation is that the sandstorm reduces acoustic waves seriously and the returning signal is very weak.(3) The sandstorm weather phenomenon leaves clear signets on the radar echo intensity time-height diagram, by which the height and thickness of sands carried by the storm can be identified and the vertical distribution of sands can be reflected. Equivalent radar echo intensity of flying sand and sandstorm weather varies in the range of-1～13dBZe.(4) Vertical shear of horizontal wind and the sustainment of low-level easterly are the dynamic causes for the occurrence of sandstorm weather in Taklimakan Desert. The moment when low-level wind appears with time is usually the beginning time of flying sand and sandstorm.(5) The active zone of turbulence in summer clear sky can go up to the height3,500-4,000m in Taklimakan Desert. The turbulence develops into high sky at the average ascending speed of0.13-0.16m/s. The time-height variation of atmospheric refractivity structure constant Cn2reflects the evolution characteristics of boundary layer to some extent. The altitude of boundary layer in summer clear sky in desert could reach3,500-4,000m.(6) Effective data acquisition rate of the CFL-03radar is relatively high under the condition of rainfall (snowfall) in arid areas. Although it is a single-site observation equipment, it can record and depict the detailed successive evolution and-motion of atmosphere in different altitudes above the observing station in the process of rainfall (snowfall). By analyzing the wind direction and speed deeply, we can identify the detailed vertical structure and meso-and micro-scale system features of atmosphere during rainfall (snowfall), judge the property of frontal surface and if the frontal surface has passed across the area, and determine the position height of high-level frontal area, the rough trend of front as well as the layers where vertical shear of horizontal winds occurs; we can monitor the developing variation of low-level jet stream, trough and ridge effectively. Besides, the vertical spatial structures of temperature advection and pressure system above the observing station can be further determined on the basis of the vertical variation of wind direction.(7) Rainfall (snowfall) weather phenomena leave clear signets and performance on the wind-profiling radar echo intensity (reflectivity) time-height diagram. The large-value zone of echo intensity has better correlations with the rainfall (snowfall) weather process, the altitude of cloud rain (snow) particle formation and the rainfall intensity. The stronger the echo intensity, the more the precipitation; the weaker the echo intensity, the less the precipitation. Therefore, the wind-profiling radar echo intensity can be taken as a reference for the precipitation quantitative estimates, monitoring and forecasting.(8) Boundary layer wind-profiling radar can detect sandstorm, rainfall, snowfall and clear-sky turbulence. The echo signal of rainfall is the strongest, followed by that of snowfall and sands, and the clear-sky turbulence echo is the weakest. The spectrum of rainfall is the widest, and the next is snowfall. The spectrum widths of sandstorm and clear-sky turbulence are similar. The echo intensity of rainfall and snowfall changes in the range about15-40dBZ, the sandstorm echo intensity is in the range of-1～13dBZe. At present, we can only obtain the intensity information of sandstorm from the observation data of wind-profiling radar, not the Doppler velocity information of sand particles yet.