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Recent Progress in Dual-Polarization radar research and Applications in China

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Advances in Atmospheric Sciences 2019年第9期36卷 961-974页

作者： Kun ZHAO Hao HUANG Mingjun WANG Wen-Chau LEE Gang CHEN Long WEN Jing WEN Guifu ZHANG Ming XUE Zhengwei YANG Liping LIU Chong WU Zhiqun HU Sheng CHEN Key Laboratory of Mesoscale Severe Weather of Ministry of Education and school of Atmospheric Sciences Nanjing University163 Xianlin RoadNanjing 210023China State Key Laboratory of Severe Weather and Joint center for Atmospheric radar research of China Meteorological Administration and Nanjing University Chinese Academy of Meteorological SciencesBeijing 100081China National center for Atmospheric research BoulderColorado 80301USA school of meteorology and advanced radar research center University of OklahomaNormanOklahoma 73019USA school of Atmospheric Sciences and Guangdong Province Key Laboratory for Climate Change and Natural Disaster StudiesSun Yat-sen UniversityGuangzhou 510006China

Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler *** dual-pol parameters have been successfully utilized to investigate precipitation microphysics and improve radar quantitative precipitation estimation(QPE).The recent progress in dual-pol radar research and applications in China is summarized in four ***,the characteristics of several representative dual-pol radars are *** approaches have been developed for radar data quality control,including calibration,attenuation correction,calculation of specific differential phase shift,and identification and removal of non-meteorological *** dual-pol radar measurements,the microphysical characteristics derived from raindrop size distribution retrieval,hydrometeor classification,and QPE is better understood in *** limited number of studies in China that have sought to use dual-pol radar data to validate the microphysical parameterization and initialization of numerical models and assimilate dual-pol data into numerical models are *** challenges of applying dual-pol data in numerical models and emerging technologies that may make significant impacts on the field of radar meteorology are discussed.

关键词： dual-polarization radar quantitative precipitation estimation precipitation microphysics drop size distribution numerical model

Seasonal Variations of Observed Raindrop Size Distribution in East China

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Advances in Atmospheric Sciences 2019年第4期36卷 346-362页

作者： Long WEN Kun ZHAO Mengyao WANG Guifu ZHANG Key Laboratory of Mesoscale Severe Weather of Ministry of Education and school of Atmospheric Sciences Nanjing University State Key Laboratory of Severe Weather and Joint center for Atmospheric radar research of China Meteorological Administration and Nanjing University Chinese Academy of Meteorological Sciences Xichang Satellite Launch center school of meteorology and center for Analysis and Prediction of Storms University of Oklahoma

Seasonal variations of rainfall microphysics in East China are investigated using data from the observations of a twodimensional video disdrometer and a vertically pointing micro rain radar. The precipitation and rain drop size distribution(DSD) characteristics are revealed for different rain types and seasons. Summer rainfall is dominated by convective rain,while during the other seasons the contribution of stratiform rain to rainfall amount is equal to or even larger than that of convective rain. The mean mass-weighted diameter versus the generalized intercept parameter pairs of convective rain are plotted roughly around the "maritime" cluster, indicating a maritime nature of convective precipitation throughout the year in East China. The localized rainfall estimators, i.e., rainfall kinetic energy–rain rate, shape–slope, and radar reflectivity–rain rate relations are further derived. DSD variability is believed to be a major source of diversity of the aforementioned derived estimators. These newly derived relations would certainly improve the accuracy of rainfall kinetic energy estimation, DSD retrieval, and quantitative precipitation estimation in this specific region.

关键词： raindrop size distribution precipitation microphysics disdrometer seasonal variation East China

Numerical Study of Boundary Layer Structure and Rainfall after Landfall of Typhoon Fitow(2013): Sensitivity to Planetary Boundary Layer Parameterization

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Advances in Atmospheric Sciences 2019年第4期36卷 431-450页

作者： Meiying DONG Chunxiao JI Feng CHEN Yuqing WANG Zhejiang Institute of Meteorological Sciences International Pacific research center and Department of MeteorologySchool of Ocean and Earth Science and TechnologyUniversity of Hawaii at Manoa

The boundary layer structure and related heavy rainfall of Typhoon Fitow(2013), which made landfall in Zhejiang Province, China, are studied using the advanced research version of the Weather research and Forecasting model, with a focus on the sensitivity of the simulation to the planetary boundary layer parameterization. Two groups of experiments—one with the same surface layer scheme and including the Yonsei University(YSU), Mellor–Yamada–Nakanishi–Niino Level 2.5,and Bougeault and Lacarrere schemes; and the other with different surface layer schemes and including the Mellor–Yamada–Janjic′ and Quasi-Normal Scale Elimination schemes—are investigated. For the convenience of comparative analysis, the simulation with the YSU scheme is chosen as the control run because this scheme successfully reproduces the track, intensity and rainfall as a whole. The maximum deviations in the peak tangential and peak radial winds may account for 11% and 33%of those produced in the control run, respectively. Further diagnosis indicates that the vertical diffusivity is much larger in the first group, resulting in weaker vertical shear of the tangential and radial winds in the boundary layer and a deeper inflow layer therein. The precipitation discrepancies are related to the simulated track deflection and the differences in the simulated low-level convergent flow among all tests. Furthermore, the first group more efficiently transfers moisture and energy and produces a stronger ascending motion than the second, contributing to a deeper moist layer, stronger convection and greater precipitation.

关键词： planetary boundary layer parameterization landfalling typhoon boundary layer structure rainfall

A robust tracking method focusing on target fluctuation and maneuver characteristics

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Science China(Information Sciences) 2022年第11期65卷 263-280页

作者： Weiming TIAN Linlin FANG Rui WANG Weidong LI Chao ZHOU Cheng HU radar research Lab School of Information and Electronics Beijing Institute of Technology Key Laboratory of Electronic and Information Technology in Satellite Navigation (Beijing Institute of Technology) Ministry of Education advanced Technology research Institute Beijing Institute of Technology

radar is an important tool for aiding in bird strike mitigation as part of overall safety management systems at civilian and military airfields. However, the diverse movement trajectories and irregular echo power fluctuations cause existing multitarget tracking algorithms to face many challenges such as detection uncertainty and maneuver uncertainty. Therefore, this paper proposes a robust tracking method focusing on target fluctuation and maneuver characteristics. Firstly, a tracking information feedback mechanism based on the fluctuation model of bird targets is established, and the measurement set in the predicted gate is reconstructed to solve the problem of track breakages caused by the echo power fluctuation. Secondly, an adaptive parameter filter model is designed to enhance maneuver adaptability. Finally, simulation and experimental data verification show that the proposed method is more adaptive to bird target characteristics and can effectively improve the tracking performance without significantly increasing computation.

关键词： radar bird targets echo power fluctuation maneuver multitarget tracking

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On the Epochal Variability in the Frequency of Cyclones during the Pre-Onset and Onset Phases of the Monsoon over the North Indian Ocean

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Advances in Atmospheric Sciences 2020年第6期37卷 634-651页

作者： P.P.BABURAJ S.ABHILASH K.MOHANKUMAR A.K.SAHAI Department of Atmospheric Sciences Cochin University of Science and TechnologyCochin 682016India Regional Meteorological center India Meteorological DepartmentChennai 600006India advanced center for Atmospheric radar research Cochin University of Science and TechnologyCochin 682022India Indian Institute of Tropical meteorology Dr.Homi Bhabha RoadPashanPune 411008India

In this paper we examine the epochal changes in the frequency of cyclones over the North Indian Ocean during the pre-onset and onset phases of the *** consider three epochs;namely,the early(1955-74),middle(1975-94)and recent(1995-2014)*** is found that the number of cyclones in the Bay of Bengal(BOB)decreases throughout the three *** the Arabian Sea(ARB),however,there is a decrease in the early epoch,before then reaching a minimum in the middle epoch followed by an increase in the recent epoch,thus exhibiting epochal *** and thermodynamic parameters along with Genesis Potential Index(GPI)are examined to understand the frequency variation in cyclogenesis over the ARB and *** the ARB,thermodynamic factors such as mid-level moisture,surface latent heat flux and sensible heat flux,and dynamic parameters such as lower-level convergence and upper-level divergence,are favorable during the early and recent epochs but unfavorable during the middle epoch,and these results are found to be consistent with the observed epochal variability in the frequency of ***,all these influential parameters are found to have decreased over the BOB during the entire 60-year period.

关键词： epoch Indian moisture

Two-Dimensional Variational Analysis of Near-Surface Moisture from Simulated radar Refractivity-Related Phase Change Observations

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Advances in Atmospheric Sciences 2013年第2期30卷 291-305页

作者： Ken-ichi SHIMOSE Ming XUE Robert D.PALMER Jidong GAO Boon Leng CHEONG David J.BODINE center for Analysis and Prediction of Storms University of OklahomaNorman OKUSA Department of Earth and Planetary Sciences Kyushu UniversityFukuokaJapan school of meteorology University of OklahomaNorman OKUSA Atmospheric radar research center University of OklahomaNorman OKUSA National Severe Storms Laboratory NOAANorman OKUSA

Because they are most sensitive to atmospheric moisture content, radar refractivity observations can provide high-resolution information about the highly variable low-level moisture field. In this study, simulated radar refractivity-related phase-change data were created using a radar simulator from realistic highresolution model simulation data for a dryline case. These data were analyzed using the 2DVAR system developed specifically for the phase-change data. Two sets of experiments with the simulated observations were performed, one assuming a uniform target spacing of 250 m and one assuming nonuniform spacing between 250 m to 4 km. Several sources of observation error were considered, and their impacts were examined. They included errors due to ground target position uncertainty, typical random errors associated with radar measurements, and gross error due to phase wrapping. Without any additional information, the 2DVAR system was incapable of dealing with phase-wrapped data directly. When there was no phase wrapping in the data, the 2DVAR produced ex- cellent analyses, even in the presence of both position uncertainty and random radar measurement errors. When a separate pre-processing step was applied to unwrap the phase-wrapped data, quality moisture anal- yses were again obtained, although the analyses were smoother due to the reduced effective resolution of the observations by interpolation and smoothing involved in the unwrapping procedure. The unwrapping procedure was effective even when significant differences existed between the analyzed state and the state at a reference time. The results affirm the promise of using radar refractivity phase-change measurements for near-surface moisture analysis.

关键词： radar refractivity variational analysis low-level moisture

Variability of microphysical characteristics in the “21·7” Henan extremely heavy rainfall event

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Science China Earth Sciences 2022年第10期65卷 1861-1878页

作者： Gang CHEN Kun ZHAO Yinghui LU Yuanyuan ZHENG Ming XUE Zhe-Min TAN Xin XU Hao HUANG Haonan CHEN Fen XU Ji YANG Shushi ZHANG Xueqi FAN Key Laboratory of Transportation meteorology of China Meteorological Administration Nanjing Joint Institute for Atmospheric SciencesNanjing 210041China Key Laboratory for Mesoscale Severe Weather/MOE and school of Atmospheric Science Nanjing UniversityNanjing 210023China State Key Laboratory of Severe Weather and Joint center for Atmospheric radar research of CMA/NJU Chinese Academy of Meteorological SciencesBeijing 100081China center for Analysis and Prediction of Storms and school of meteorology University of OklahomaNormanOklahoma 73072USA Colorado State University Fort CollinsCO 80523USA

In this study, significant rainfall microphysical variability is revealed for the extremely heavy rainfall event over Henan Province in July 2021(the “21·7” Henan EHR event) using a dense network of disdrometers and two polarimetric *** broad distributions of specific drop size distribution(DSD) parameters are identified in heavy rainfall from the disdrometer observations, indicating obvious microphysical variability on the surface. A K-means clustering algorithm is adopted to objectively classify the disdrometer datasets into separate groups, and distinct DSD characteristics are found among these heavy rainfall groups. Combined with the supporting microphysical structures obtained through radar observations, comprehensive microphysical features of the DSD groups are derived. An extreme rainfall group is dominantly formed in the deep convection over the plain regions, where the high number of concentrations and large mean sizes of surface raindrops are underpinned by both active ice-phase processes and efficient warm-rain collision-coalescence processes in the vertical direction. Convection located near orographic regions is characterized by restricted ice-phase processes and high coalescence efficiency of liquid hydrometeors, causing the dominant DSD group to comprise negligible large raindrops. Multiple DSD groups can coexist within certain precipitation episodes at the disdrometer stations, indicating the potential microphysical variability during the passage of convective system on the plain regions.

关键词： The“21·7”Henan EHR event Microphysical characteristics Variability Disdrometer Polarimetric radar

Variation of Radio Refractivity with Respect to Moisture and Temperature and Influence on radar Ray Path

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Advances in Atmospheric Sciences 2008年第6期25卷 1098-1106页

作者： Jidong GAO Keith BREWSTER Ming XUE center for Analysis and Prediction of Storms school of meteorology University of Oklahoma Norman Oklahoma 73072 USA

In this study, the variation of radio refractivity with respect to temperature and moisture is analyzed. Also, the effects of vertical gradients in temperature and moisture on the propagation paths of electromagnetic waves of weather radar are examined for several sites across the United States using several years of sounding data from the National Weather Service. The ray path is important for identifying storm characteristics and for properly using the radar data in initializing numerical weather prediction models. It is found that during the warm season the radio refractivity gradient is more sensitive to moisture gradients than to temperature gradients. Ray paths from the commonly accepted vertical ray path model are compared to a ray path computed from a stepwise ray tracing algorithm using data from actual soundings. For the sample of about 16 000 soundings examined, we find that only a small fraction of the ray paths diverge significantly from those calculated using a ray path model based on the US Standard Atmosphere. While the problem of ray dueting in the presence of a temperature inversion is fairly well known, we identify the presence of a strong vertical moisture gradient as the culprit in the majority of the cases where significant deviations occurred.

关键词： radio refractivity radar ray path

Dynamics of local extreme rainfall of super Typhoon Soudelor (2015) in East China

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Science China Earth Sciences 2018年第5期61卷 572-594页

作者： Jinsong PAN Daigao TENG Fuqing ZHANG Lingli ZHOU Ling LUO Yonghui WENG Yunji ZHANG Zhejiang Meteorological Observatory Hangzhou 310021 China Department of meteorology and Atmospheric Sciences and Center for Advanced Data Assimilation and Prediction Techniques Pennsylvania State University University Park Pennsylvania 16802 USA

The characteristics and dynamics associated with the distribution, intensity, and triggering factors of local severe precipitation in Zhejiang Province induced by Super Typhoon Soudelor(2015) were investigated using mesoscale surface observations, radar reflectivity, satellite nephograms, and the final(FNL) analyses of the Global Forecasting System(GFS) of the National center for Environmental Prediction(NCEP). The rainfall processes during Soudelor's landfall and translation over East China could be separated into four stages based on rainfall characteristics such as distribution, intensity, and corresponding dynamics. The relatively less precipitation in the first stage resulted from interaction between the easterly wind to the north flank of this tropical cyclone(TC) and the coastal topography along the southeast of Zhejiang Province, China. With landfall of the TC in East China during the second stage, precipitation maxima occurred because of interaction between the TC's principal rainbands and the local topography from northeastern Fujian Province to southwestern Zhejiang Province. The distribution of precipitation presented significant asymmetric features in the third stage with maximal rainfall bands in the northeast quadrant of the TC when Soudelor's track turned from westward to northward as the TC decayed rapidly. Finally, during the northward to northeastward translation of the TC in the fourth stage, the interaction between a mid-latitude weather system and the northern part of the TC resulted in transfer of the maximum rainfall from the north of Zhejiang Province to the north of Jiangsu Province,which represented the end of rainfall in Zhejiang Province. Further quantitative calculations of the rainfall rate induced by the interaction between local topography and TC circulation(defined as "orographic effects") in the context of a one-dimensional simplified model showed that orographic effects were the primary factor determining the intensity of precipit

关键词： TC outer circulation TC principal rainband Orographic effect Expanding of TC's spiral bands