Application of X-band Polarimetric Phased-array Radars in Quantitative Precipitation Estimation

The performance of different quantitative precipitation estimation(QPE) relationships is examined using the polarimetric variables from the X-band polarimetric phased-array radars in Guangzhou,China.Three QPE approaches,namely,R(ZH),R(ZH,ZDR) and R(KDP),are developed for horizontal reflectivity,differential reflectivity and specific phase shift rate,respectively.The estimation parameters are determined by fitting the relationships to the observed radar variables using the T-matrix method.The QPE relationships were examined using the data of four heavy precipitation events in southern China.The examination shows that the R(ZH) approach performs better for the precipitation rate less than 5 mm h-1, and R(KDP) is better for the rate higher than 5 mm h-1, while R(ZH,ZDR) has the worst performance.An adaptive approach is developed by taking the advantages of both R(ZH) and R(KDP) approaches to improve the QPE accuracy.

Case Analysis on Physical Characteristics of Autumn Cumulus-stratus Mixed Cloud in Shandong Province

[Objective] The aim was to analyze physical structures of mixed cloud in autumn in Shandong.[Method] By dint of Doppler radar data,the raindrop spectrum data observed by laser spectrometer,second sounding data of L-band,satellite retrieval data,and other general information,the physical structures of mixed cloud in autumn on August 29,2009 were discussed.[Result] This was a typical precipitation process of mixed cloud,and the main precipitation process lasted for 10 hours.Rainfall intensity was ups and downs obviously with the time.The maximum rainfall intensity was 6.5 mm/h and the normal of that was less than 3.0 mm/h.The rain concentrations were between 5 and 300,and the raindrop spectrum was mainly of bimodal or multimodal peaks.It showed that the precipitating cloud was mainly cold cloud and the development of warm layers was not well according to the vertical structure of clouds which was analyzed by second sounding data.It showed by the Doppler radar data that the whole precipitation process was divided into four stages:prior period and initial,maturing,declining stages for precipitation,which the echo structure of different stages was quite different.[Conclusion] The study laid theoretical basis for the study on precipitation mechanism and artificial precipitation potential.

Analysis of the Microphysical Properties of a Stratiform Rain Event Using an L-Band Profiler Radar

This paper investigates spatial and temporal distributions of the microphysical properties of precipitating stratiform clouds based on Doppler spectra of rain particles observed by an L-band profiler radar.The retrieval of raindrop size distributions（RSDs） is accomplished through eliminating vertical air motion and isolating the terminal fall velocity of raindrops in the observed Doppler velocity spectrum.The microphysical properties of raindrops in a broad stratiform region with weak convective cells are studied using data collected from a 1320-MHz wind profiler radar in Huayin,Shaanxi Province on 14 May 2009.RSDs and gamma function parameters are retrieved at altitudes between 700 and 3000 m above the surface,below a melting layer.It is found that the altitude of the maximum number of raindrops was closely related to the surface rain rate.The maximum number of large drops was observed at lower altitudes earlier in the precipitation event but at higher altitudes in later periods,suggesting decreases in the numbers of large and medium size raindrops.These decreases may have been caused by the breakup of larger drops and evaporation of smaller drops as they fell.The number of medium size drops decreased with increasing altitude.The relationship between reflectivity and liquid water content during this precipitation event was Z = 1.69×10~4M^（1.5）,and the relationship between reflectivity and rain intensity was Z = 256I^（1.4）.

STUDY ON RADAR-RADIOMETER SYSTEM AND ITS RAINFALL OBSERVATION

In order to improve the accuracy of the rainfall measurement, a radar-radiometer system has been devel- oped. It could be used to measure the distribution of the rainfall intensity aLld the variation of area rainfall. In field experiment, the accuracy of the rainfall measurement was imporved. In this paper, the error of rainfall measurement by radar will be evaluated and the methods to improve the accuracy of the rainfall measurement will be discussed.