While heavy rainfall frequently takes place in southern China during summer monsoon seasons,quantitative precipitation forecast skills are relatively poor.Therefore,detailed knowledge about the raindrop size distribut...While heavy rainfall frequently takes place in southern China during summer monsoon seasons,quantitative precipitation forecast skills are relatively poor.Therefore,detailed knowledge about the raindrop size distribution(DSD)is useful in improving the quantitative precipitation estimation and forecast.Based on the data during 2018-2022 from 86stations in a ground-based optical disdrometer measurement network,the characteristics of the DSD in Guangdong province are investigated in terms of the particle size distribution(N(D)),mass-weighted mean diameter(Dm) and other integral DSD parameters such as radar reflectivity(Z),rainfall rate(R) and liquid water content(LWC).In addition,the effects of geographical locations,weather systems(tropical cyclones,frontal systems and the summer monsoon) and precipitation types on DSD characteristics are also considered.The results are shown as follows.1) Convective precipitation has a broader N(D) and larger mean particle diameter than the stratiform precipitation,and the DSD observations in Guangdong are consistent with the three-parameter gamma distribution.The relationships between the Z and R for stratiform and convective precipitation are also derived for the province,i.e.,Z=332.34 R1.32and Z=366.26R1.42which is distinctly different from that of the Next-generation Weather Radar(NEXRAD) Z-R relationship in United States.2) In the rainy season(April-September),the Dm, R and LWC are larger than those in the dry season(OctoberMarch).Moreover the above parameters are larger,especially in mid-May,which is the onset of the South China Sea summer monsoon.3) The spatial analysis of DSD shows that the coastal station observations indicate a smaller Dmand a larger normalized intercept parameter(log10Nw),suggestive of maritime-like rainfall.Dmis larger and log10Nwis smaller in the inland area,suggestive of continental-like rainfall.4) Affected by such weather systems as the tropical cyclone,frontal system and summer monsoon,the DSD shows characteristics with distinct differences.Furthermore,frontal system rainfall tends to present a continental-like rainfall,tropical cyclone rainfall tends to have a maritime-like rainfall,and summer monsoon rainfall characteristic are between maritime-and continental-like cluster(raindrop concentration and diameter are higher than continental cluster and maritime cluster,respectively.)展开更多
This study uses rain gauge observations to assess the performance of different radar estimators R(ZH),R(KDP)and R(A)in estimating precipitation based on the observations of an S-band polarimetric radar over southern C...This study uses rain gauge observations to assess the performance of different radar estimators R(ZH),R(KDP)and R(A)in estimating precipitation based on the observations of an S-band polarimetric radar over southern China during a typical convective storm and an extremely severe typhoon,i.e.,Typhoon Manghkut.These radar estimators were derived from observations of a local autonomous particle size and velocity(Parsivel)unit(APU)disdrometer.A key parameter,alpha(α),which is the ratio of specific attenuation A to specific differential phase KDP with three fixed values(α=0.015 dB deg^(-1),α=0.0185 dB deg^(-1)andα=0.03 dB deg^(-1))was examined to test the sensitivity of the R(A)rain retrievals.The results show that:(1)All radar estimators can capture the spatio-temporal patterns of two precipitation events,R(A)withα=0.0185 dB deg^(-1)is well correlated with gauge measurement via higher Pearson’s correlation coefficient(CC)of 0.87,lower relative bias(RB)of 16%,and lower root mean square error(RMSE)of 17.09 mm in the convective storm while it underestimates the typhoon event with RB of 35%;(2)R(A)withα=0.03 dB deg^(-1)shows the best statistical scores with the highest CC(0.92),lowest RB(7%)and RMSE(25.74 mm)corresponding to Typhoon Manghkut;(3)R(A)estimates are more efficient in mitigating the impact of partial beam blockage.The results indicate thatαis remarkably influenced by the variation of drop size distribution.Thus,more work is needed to establish an automated and optimizedαfor the R(A)relation during different rainfall events over different regions.展开更多
基金National Natural Science Foundation of China(42075014,41975138)Natural Science Foundation of Guangdong Province(2022A1515011814,2021A1515011539,2020A1515010602)+3 种基金Open Grants of State Key Laboratory of Severe Weather(2022LASW-B15)Radar Application and Short-term Severe-weather Predictions and Warnings Technology Program(GRMCTD202002)Key Scientific and Technological Research Project of GRMC(GRMC2020Z03)Water Resource Science and Technology Innovation Program of Guangdong Province(2022-02)。
文摘While heavy rainfall frequently takes place in southern China during summer monsoon seasons,quantitative precipitation forecast skills are relatively poor.Therefore,detailed knowledge about the raindrop size distribution(DSD)is useful in improving the quantitative precipitation estimation and forecast.Based on the data during 2018-2022 from 86stations in a ground-based optical disdrometer measurement network,the characteristics of the DSD in Guangdong province are investigated in terms of the particle size distribution(N(D)),mass-weighted mean diameter(Dm) and other integral DSD parameters such as radar reflectivity(Z),rainfall rate(R) and liquid water content(LWC).In addition,the effects of geographical locations,weather systems(tropical cyclones,frontal systems and the summer monsoon) and precipitation types on DSD characteristics are also considered.The results are shown as follows.1) Convective precipitation has a broader N(D) and larger mean particle diameter than the stratiform precipitation,and the DSD observations in Guangdong are consistent with the three-parameter gamma distribution.The relationships between the Z and R for stratiform and convective precipitation are also derived for the province,i.e.,Z=332.34 R1.32and Z=366.26R1.42which is distinctly different from that of the Next-generation Weather Radar(NEXRAD) Z-R relationship in United States.2) In the rainy season(April-September),the Dm, R and LWC are larger than those in the dry season(OctoberMarch).Moreover the above parameters are larger,especially in mid-May,which is the onset of the South China Sea summer monsoon.3) The spatial analysis of DSD shows that the coastal station observations indicate a smaller Dmand a larger normalized intercept parameter(log10Nw),suggestive of maritime-like rainfall.Dmis larger and log10Nwis smaller in the inland area,suggestive of continental-like rainfall.4) Affected by such weather systems as the tropical cyclone,frontal system and summer monsoon,the DSD shows characteristics with distinct differences.Furthermore,frontal system rainfall tends to present a continental-like rainfall,tropical cyclone rainfall tends to have a maritime-like rainfall,and summer monsoon rainfall characteristic are between maritime-and continental-like cluster(raindrop concentration and diameter are higher than continental cluster and maritime cluster,respectively.)
基金National Natural Science Foundation of China(41875182)Guangzhou Science and Technology Plan Projects(201904010162)+1 种基金Sun Yat-sen University“100 Top Talents Program”(74110-18841203)International Program for Ph.D.Candidates at Sun Yat-sen University
文摘This study uses rain gauge observations to assess the performance of different radar estimators R(ZH),R(KDP)and R(A)in estimating precipitation based on the observations of an S-band polarimetric radar over southern China during a typical convective storm and an extremely severe typhoon,i.e.,Typhoon Manghkut.These radar estimators were derived from observations of a local autonomous particle size and velocity(Parsivel)unit(APU)disdrometer.A key parameter,alpha(α),which is the ratio of specific attenuation A to specific differential phase KDP with three fixed values(α=0.015 dB deg^(-1),α=0.0185 dB deg^(-1)andα=0.03 dB deg^(-1))was examined to test the sensitivity of the R(A)rain retrievals.The results show that:(1)All radar estimators can capture the spatio-temporal patterns of two precipitation events,R(A)withα=0.0185 dB deg^(-1)is well correlated with gauge measurement via higher Pearson’s correlation coefficient(CC)of 0.87,lower relative bias(RB)of 16%,and lower root mean square error(RMSE)of 17.09 mm in the convective storm while it underestimates the typhoon event with RB of 35%;(2)R(A)withα=0.03 dB deg^(-1)shows the best statistical scores with the highest CC(0.92),lowest RB(7%)and RMSE(25.74 mm)corresponding to Typhoon Manghkut;(3)R(A)estimates are more efficient in mitigating the impact of partial beam blockage.The results indicate thatαis remarkably influenced by the variation of drop size distribution.Thus,more work is needed to establish an automated and optimizedαfor the R(A)relation during different rainfall events over different regions.
