| Dual-linear polarimetric Doppler radar is capable of improving the accuracy of rainfall estimation and the detection ability of disastrous weather such as hail,which is of great significance to solving meteorological operational problems.However,in the actual detection process,Radar data is quite vulnerable to non-precipitation echos,systematic and environmental noise,attenuation of electromagnetic wave signal and so on.Therefore,it's necessary to control quality of radar data before it is used.This study is to find a set of quality control system which is suitable for C-band Dual-linear Polarimetric Aperture CoherentDoppler Radar?referred to as NUIST-CDP radar?.Main blocks of this syetem and validations of the results are as follows:1.Combining the Fuzzy Logic and Thresh,we propose a hybrid algorithm to separate precipitation and non-precipitation echos.This algorithm takes the horizontal textures of radar parameters as inputs,which effectively inhibits the influence of attenuation of electromagnetic wave signal,errors of system calibrations,velocity ambiguity and so on.In addition,‘regional inspection'and‘thresh inspection'improve the accuracy of recognizing the bright band of zero-temperature layer and clear-air echos.2.On the basis of the recognition result of precipitation and non-precipitation echos,the Linear Programming,the Wavelet Analysis and the Iterative Filtering Technique are employed to remove non-precipitation echoes'fluctuations,differential backscattering phase,random perturbations of electromagnetic wave signals and system errors from the differential phase data.It shows that this method can accurately extract differential propagation phase from differential phase by contrast of profiles of data before and after processing.Then,applying the Variable Distance Method to fit differential propagation phase constraints by data before and after processing.By comparing the radial distance profiles and plan position indicators,it further shows that this method has a good effect of smoothing the differential phase data.3.Using Meteorological Target Method to calibrate NUIST-CDP radar's system errors of differential reflectivity ZDR.Through screening qualified light rain and dry aggregated snow particles,we discover that light rain particles'standard deviation of system errors is far less than dry aggregated snow particles'.Also,the number of light rain particles which meet the screening conditions is far bigger than that of dry aggregated snow particles.Therefore,NUIST-CDP radar is calibrated with light rain particles as meteorological targets.The results show that the ZDRR values of rain particles after calibration is more reasonable than that before calibration.4.An attenuation correction algorithm which is based on the Self-Consistent Method with Constraints is selected for correcting reflectivity ZH data of NUIST-CDP radar.Some comparisons are made between the data of NUITS-CDP radar and a nearby S-band radar observed at the same time.The results show that the corrected values of ZH are closer to S-band's.Also,through analyzing the scatter plots of AH vs.ZH and KDPvs.ZH before and after correcting,it is found that this algorithm is more effective in correcting convective precipitation echoes. |
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