Polarimetric radar and 2D video disdrometer observations provide new insights into the precipitation microphysical processes and characteristics in the inner rainband of tropical cyclone(TC)Kajiki(2019)in the South Ch...Polarimetric radar and 2D video disdrometer observations provide new insights into the precipitation microphysical processes and characteristics in the inner rainband of tropical cyclone(TC)Kajiki(2019)in the South China Sea for the first time.The precipitation of Kajiki is dominated by high concentrations and small(<3 mm)raindrops,which contribute more than 98%to the total precipitation.The average mass-weighted mean diameter and logarithmic normalized intercept are 1.49 mm and 4.47,respectively,indicating a larger mean diameter and a lower concentration compared to the TCs making landfall in eastern China.The ice processes of the inner rainband are dramatically different among different stages.The riming process is dominant during the mature stage,while during the decay stage the aggregation process is dominant.The vertical profiles of the polarimetric radar variables together with ice and liquid water contents in the convective region indicate that the formation of precipitation is dominated by warm-rain processes.Large raindrops collect cloud droplets and other raindrops,causing reflectivity,differential reflectivity,and specific differential phase to increase with decreasing height.That is,accretion and coalescence play a critical role in the formation of heavy rainfall.The melting of different particles generated by the ice process has a great influence on the initial raindrop size distribution(DSD)to further affect the warm-rain processes.The DSD above heavy rain with the effect of graupel has a wider spectral width than the region without the effect of graupel.展开更多
In this paper, the evolution of the microphysical characteristics in different regions(eyewall, inner core, and outer rainbands) and different quadrants [downshear left(DL), downshear right(DR), upshear left(UL), and ...In this paper, the evolution of the microphysical characteristics in different regions(eyewall, inner core, and outer rainbands) and different quadrants [downshear left(DL), downshear right(DR), upshear left(UL), and upshear right(UR)]during the final landfall of Typhoon Ewiniar(2018) is analyzed using two-dimensional video disdrometer and S-band polarimetric radar data collected in Guangdong, China. Due to the different types of underlying surfaces, the periods before landfall(mainly dominated by underlying sea surface) and after landfall(mainly dominated by underlying land surface) are also analyzed. Both before landfall and after landfall, the downshear quadrants had the dominate typhoon precipitation. The outer rainbands had more graupel than the inner core, resulting in a larger radar reflectivity, differential reflectivity, specific differential phase shift, and mass-weighted mean diameter below the melting layer. Compared with other regions, the eyewall region had the smallest mean logarithmic normalized intercept parameter before landfall and the smallest mean mass-weighted mean diameter and the largest mean logarithmic normalized intercept parameter after landfall. The hydrometeor size sorting was obvious in the eyewall and inner core(especially in the eyewall) after landfall. A high concentration of large raindrops fell in the DL quadrant, and more small raindrops fell in the UR quadrant. Although the icephase process and warm rain process were both important in the formation of tropical cyclone precipitation, the warm rain process(ice-phase process) contributed more liquid water before landfall(after landfall). This investigation provides a reference for improving the microphysical parameterization scheme in numerical models.展开更多
Knowledge of the raindrop size distribution(DSD)is crucial for disaster prevention and mitigation.The recordbreaking rainfall in the summer of 2020 caused some of the worst flooding ever experienced in China.This stud...Knowledge of the raindrop size distribution(DSD)is crucial for disaster prevention and mitigation.The recordbreaking rainfall in the summer of 2020 caused some of the worst flooding ever experienced in China.This study uses 96 Parsivel disdrometers and eight-year Global Precipitation Measurement(GPM)satellite observations to reveal the microphysical aspects of the disastrous rainfall during its northward migration over East China.The results show that the nearly twice as heavy rainfall in Jiangsu Province compared to Fujian Province can be attributed to the earlier-than-average northward jump of the summer monsoon rainband to the Yangtze-Huaihe River valley.The persistent heavy monsoon rainfall showed similar near-maritime DSD characteristics,with a higher concentration of small raindrops than the surrounding climatic regimes.During the northward movement of the rainband,the DSD variables and composite spectra between the pre-summer rainfall in Fujian and mei-yu rainfall in Jiangsu exhibited inherent similarities with slight regional variations.These are associated with similar statistical vertical precipitation structures for both convective and stratiform rain in these regions/periods.The vertical profiles of radar reflectivity and DSD parameters are typical of monsoonal rainfall features,implying the competition between coalescence,breakup,and accretion of vital warm rain processes.This study attributes the anomalously long duration of the mei-yu season for the record-breaking rainfall and reveals inherent homogeneous rainfall microphysics during the northward movement of the summer monsoon rainband.The conclusion is statistically robust and would be helpful for accurate precipitation estimation and model parameterization of summer monsoon rainfall over East China.展开更多
Characteristics of raindrop size distribution during summer are studied by using the data from six Parsivel disdrometers located in the northeastern Tibetan Plateau.The analysis focuses on convective and stratiform pr...Characteristics of raindrop size distribution during summer are studied by using the data from six Parsivel disdrometers located in the northeastern Tibetan Plateau.The analysis focuses on convective and stratiform precipitation at high altitudes from 2434 m to 4202 m.The results show that the contribution of stratiform and convective precipitation with rain rate between 1≤R<5 mm h^(-1)to the total precipitation increases with altitude,and the raindrop scale and number concentration of convective precipitation is larger than that for stratiform precipitation.The droplet size spectra of both stratiform and convective precipitation shows a single peak with a peak particle size between 0.31–0.50 mm,and they have essentially the same peak particle size and number concentration at the same altitude.The maximum spectral widths of stratiform clouds are between 4 mm and 5 mm,while those of convective clouds range from 4 mm to 8 mm.The Gamma distribution is more suitable than the Marshall-Palmer distribution in terms of the actual raindrop spectrum distribution.The stratiform precipitation particles are smaller with higher number concentration,while the opposite is true for the convective precipitation particles.The convective precipitation particles drop faster than stratiform precipitation particles when the particle size exceeds 2 mm,and the falling velocity of raindrops after standard curve fitting is underestimated during the observation period.Moreover,conventional radar estimation methods would underestimate the precipitation in the Northeastern Tibetan Plateau.展开更多
Knowledge of raindrop size distribution(RSD)is essential for understanding microphysical processes occurring within cloud and precipitation systems,as well as for enhancing the capabilities of numerical models and rad...Knowledge of raindrop size distribution(RSD)is essential for understanding microphysical processes occurring within cloud and precipitation systems,as well as for enhancing the capabilities of numerical models and radar-based quantitative precipitation estimation(QPE).However,observation and study of RSD,especially its temporal and spatial variability,remain quite limited in specific regions.One such region is Southeast China.In this paper,four years of disdrometer data from a south coastal plain site(CPS)and a north hilly inland site(HIS)in the Fujian Province of Southeast China are analyzed and compared to elucidate the characteristics and discrepancies of RSD between these two distinct climatological sites.On this basis,empirical relations between the parameters of Gamma distribution and between radar reflectivity factor(Z)and rain rate(R)are proposed.The results are summarized as follows.(1)In the cases of light to moderate rains,HIS exhibits a higher(lower)concentration of small-size(midsize and large)raindrops with diameters of D<1 mm(1≤3 and D≥3 mm),compared to CPS.Conversely,as the rain intensity increases,the raindrop concentrations across all size categories at CPS gradually exceed those at HIS.(2)RSDs at both sites broaden and exhibit elevated concentrations across most diameter categories as the rain rate increases.(3)For rainfalls with rain rates below 5 mm h^(-1),collision and coalescence dominate,resulting in unimodal rain spectra at both sites;whereas for stronger rainfalls,breakup intensifies,leading to the development of bimodal rain spectra.(4)HIS experiences more stratiform rains but fewer,weaker convective rains than CPS.Stratiform RSD at HIS possesses more small and large raindrops but fewer midsize raindrops compared to CPS,whereas convective RSD at CPS possesses higher concentrations across all diameter categories.(5)Accordingly,specific Z–R relations at these two sites are proposed and validated for two real cases,demonstrating that the accuracy of radar QPE is effectively improved based on the proposed Z–R relations.展开更多
基金This work was primarily supported by the National Key Research and Development Program of China(Grant No.2018YFC1507304)the National Natural Science Foundation of China(Grant Nos.42075080,41975066 and 41865009).
文摘Polarimetric radar and 2D video disdrometer observations provide new insights into the precipitation microphysical processes and characteristics in the inner rainband of tropical cyclone(TC)Kajiki(2019)in the South China Sea for the first time.The precipitation of Kajiki is dominated by high concentrations and small(<3 mm)raindrops,which contribute more than 98%to the total precipitation.The average mass-weighted mean diameter and logarithmic normalized intercept are 1.49 mm and 4.47,respectively,indicating a larger mean diameter and a lower concentration compared to the TCs making landfall in eastern China.The ice processes of the inner rainband are dramatically different among different stages.The riming process is dominant during the mature stage,while during the decay stage the aggregation process is dominant.The vertical profiles of the polarimetric radar variables together with ice and liquid water contents in the convective region indicate that the formation of precipitation is dominated by warm-rain processes.Large raindrops collect cloud droplets and other raindrops,causing reflectivity,differential reflectivity,and specific differential phase to increase with decreasing height.That is,accretion and coalescence play a critical role in the formation of heavy rainfall.The melting of different particles generated by the ice process has a great influence on the initial raindrop size distribution(DSD)to further affect the warm-rain processes.The DSD above heavy rain with the effect of graupel has a wider spectral width than the region without the effect of graupel.
基金jointly supported by Guangdong Basic and Applied Basic Research Foundation (2021A1515011415)the National Natural Science Foundation of China (Grant Nos. 42075086, 41975138, and 42005062)the Natural Science Foundation of Guangdong Province, China (2019A1515010814)。
文摘In this paper, the evolution of the microphysical characteristics in different regions(eyewall, inner core, and outer rainbands) and different quadrants [downshear left(DL), downshear right(DR), upshear left(UL), and upshear right(UR)]during the final landfall of Typhoon Ewiniar(2018) is analyzed using two-dimensional video disdrometer and S-band polarimetric radar data collected in Guangdong, China. Due to the different types of underlying surfaces, the periods before landfall(mainly dominated by underlying sea surface) and after landfall(mainly dominated by underlying land surface) are also analyzed. Both before landfall and after landfall, the downshear quadrants had the dominate typhoon precipitation. The outer rainbands had more graupel than the inner core, resulting in a larger radar reflectivity, differential reflectivity, specific differential phase shift, and mass-weighted mean diameter below the melting layer. Compared with other regions, the eyewall region had the smallest mean logarithmic normalized intercept parameter before landfall and the smallest mean mass-weighted mean diameter and the largest mean logarithmic normalized intercept parameter after landfall. The hydrometeor size sorting was obvious in the eyewall and inner core(especially in the eyewall) after landfall. A high concentration of large raindrops fell in the DL quadrant, and more small raindrops fell in the UR quadrant. Although the icephase process and warm rain process were both important in the formation of tropical cyclone precipitation, the warm rain process(ice-phase process) contributed more liquid water before landfall(after landfall). This investigation provides a reference for improving the microphysical parameterization scheme in numerical models.
基金supported by the National Natural Science Foundation of China(Grant Nos.41905021,42005009).
文摘Knowledge of the raindrop size distribution(DSD)is crucial for disaster prevention and mitigation.The recordbreaking rainfall in the summer of 2020 caused some of the worst flooding ever experienced in China.This study uses 96 Parsivel disdrometers and eight-year Global Precipitation Measurement(GPM)satellite observations to reveal the microphysical aspects of the disastrous rainfall during its northward migration over East China.The results show that the nearly twice as heavy rainfall in Jiangsu Province compared to Fujian Province can be attributed to the earlier-than-average northward jump of the summer monsoon rainband to the Yangtze-Huaihe River valley.The persistent heavy monsoon rainfall showed similar near-maritime DSD characteristics,with a higher concentration of small raindrops than the surrounding climatic regimes.During the northward movement of the rainband,the DSD variables and composite spectra between the pre-summer rainfall in Fujian and mei-yu rainfall in Jiangsu exhibited inherent similarities with slight regional variations.These are associated with similar statistical vertical precipitation structures for both convective and stratiform rain in these regions/periods.The vertical profiles of radar reflectivity and DSD parameters are typical of monsoonal rainfall features,implying the competition between coalescence,breakup,and accretion of vital warm rain processes.This study attributes the anomalously long duration of the mei-yu season for the record-breaking rainfall and reveals inherent homogeneous rainfall microphysics during the northward movement of the summer monsoon rainband.The conclusion is statistically robust and would be helpful for accurate precipitation estimation and model parameterization of summer monsoon rainfall over East China.
基金jointly sponsored by the Second Tibetan Plateau Atmospheric Sciences Experiment(STEP)(Grant No.2019QZKK010406)the National Natural Science Foundation of China(Grant No.42165008)Natural Science Foundation of Technology Department of Qinghai Province(Grant No.2021-ZJ-745)。
文摘Characteristics of raindrop size distribution during summer are studied by using the data from six Parsivel disdrometers located in the northeastern Tibetan Plateau.The analysis focuses on convective and stratiform precipitation at high altitudes from 2434 m to 4202 m.The results show that the contribution of stratiform and convective precipitation with rain rate between 1≤R<5 mm h^(-1)to the total precipitation increases with altitude,and the raindrop scale and number concentration of convective precipitation is larger than that for stratiform precipitation.The droplet size spectra of both stratiform and convective precipitation shows a single peak with a peak particle size between 0.31–0.50 mm,and they have essentially the same peak particle size and number concentration at the same altitude.The maximum spectral widths of stratiform clouds are between 4 mm and 5 mm,while those of convective clouds range from 4 mm to 8 mm.The Gamma distribution is more suitable than the Marshall-Palmer distribution in terms of the actual raindrop spectrum distribution.The stratiform precipitation particles are smaller with higher number concentration,while the opposite is true for the convective precipitation particles.The convective precipitation particles drop faster than stratiform precipitation particles when the particle size exceeds 2 mm,and the falling velocity of raindrops after standard curve fitting is underestimated during the observation period.Moreover,conventional radar estimation methods would underestimate the precipitation in the Northeastern Tibetan Plateau.
基金Supported by the National Key Research and Development Program of China(2023YFC3007501)Natural Science Foundation of Fujian Province of China(2023J011337)Innovation Ability Promotion Plan Project of Chengdu University of Information Technology(KYQN202307)。
文摘Knowledge of raindrop size distribution(RSD)is essential for understanding microphysical processes occurring within cloud and precipitation systems,as well as for enhancing the capabilities of numerical models and radar-based quantitative precipitation estimation(QPE).However,observation and study of RSD,especially its temporal and spatial variability,remain quite limited in specific regions.One such region is Southeast China.In this paper,four years of disdrometer data from a south coastal plain site(CPS)and a north hilly inland site(HIS)in the Fujian Province of Southeast China are analyzed and compared to elucidate the characteristics and discrepancies of RSD between these two distinct climatological sites.On this basis,empirical relations between the parameters of Gamma distribution and between radar reflectivity factor(Z)and rain rate(R)are proposed.The results are summarized as follows.(1)In the cases of light to moderate rains,HIS exhibits a higher(lower)concentration of small-size(midsize and large)raindrops with diameters of D<1 mm(1≤3 and D≥3 mm),compared to CPS.Conversely,as the rain intensity increases,the raindrop concentrations across all size categories at CPS gradually exceed those at HIS.(2)RSDs at both sites broaden and exhibit elevated concentrations across most diameter categories as the rain rate increases.(3)For rainfalls with rain rates below 5 mm h^(-1),collision and coalescence dominate,resulting in unimodal rain spectra at both sites;whereas for stronger rainfalls,breakup intensifies,leading to the development of bimodal rain spectra.(4)HIS experiences more stratiform rains but fewer,weaker convective rains than CPS.Stratiform RSD at HIS possesses more small and large raindrops but fewer midsize raindrops compared to CPS,whereas convective RSD at CPS possesses higher concentrations across all diameter categories.(5)Accordingly,specific Z–R relations at these two sites are proposed and validated for two real cases,demonstrating that the accuracy of radar QPE is effectively improved based on the proposed Z–R relations.
