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Multidecadal variability of sea ice in the East Siberia-Beaufort Sea region and its linkage with the Atlantic Multidecadal Oscillation
LIU Li, ZHANG Wenjun, LIU Chao
 doi: 10.11676/qxxb2023.20220080
[Abstract](80) [FullText HTML](12) [PDF 8900KB](14)
This work investigates the spatial and temporal features of boreal autumn (August—October) East Siberian-Beaufort (EsCB) sea ice on decadal timescales during the period of 1950—2020 based on monthly sea surface temperature (SST), sea ice concentration (SIC) from the Hadley Center and atmospheric reanalysis dataset provided by the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR). The possible modulation effects of Atlantic Multidecadal Oscillation (AMO) on the EsCB sea ice are further elaborated. The EsCB sea displays the strongest decadal component of sea ice in the Arctic, accounting for more than 40% of the local total variance of SIC anomalies. Our further analyses show that the AMO exerts a prominent modulation on the EsCB sea ice. In the positive AMO phase, warm North Atlantic SST anomalies trigger poleward propagating atmospheric Rossby waves, favoring the establishment of an anomalous high over the central Arctic region. The corresponding adiabatic descending motion warms the lower troposphere and causes the EsCB sea ice to melt. The surface warming and EsCB sea ice melting can simultaneously give rise to an increase in local cloud amount and downward longwave radiation, which in turn increases the surface air temperature. This surface air temperature-cloud-longwave positive feedback is beneficial for the long-term maintenance of the decadal sea ice signal. The North Atlantic pacemaker experiments can realistically reproduce the observed physical process as shown above, which further supports our main conclusions.
A study on the model uncertainty of rainstorm forecast in Guangzhou on 7 May 2017
Chen Daiya, Shen Xueshun, Huo Zhenhua
 doi: 10.11676/qxxb2023.20220047
[Abstract](87) [FullText HTML](12) [PDF 5592KB](36)
A warm-sector torrential rain under weak synoptic scale forcing occurred in Guangzhou on 7 May 2017. The precipitation process developed rapidly and locally, and the precipitation intensity is extremely high. Many operational numerical weather prediction models failed to forecast this storm. To study the model uncertainty in the forecast of this precipitation process, the Conditional Nonlinear Optimal Perturbation related to Parameters (CNOP-P) is adopted to select key physical parameters which can best represent the nonlinear error growth characteristics of the meso-micro scale system. A new model perturbation scheme CNOP-P-RP is constructed based on these key parameters. Convective-permitting ensemble prediction experiment is carried out based on the CMA-Meso model. Finally, the physical mechanism behind the influences of key parameters selected by CNOP-P on local convection in different stages is investigated. The result shows that the key parameters selected by CNOP-P are mainly related to vertical diffusion, auto-conversion from cloud to rain and conversion from other hydrometeors to raindrops. Compared with Stochastic Perturbed Parameterization Tendencies (SPPT) scheme which is widely utilized in operational ensemble prediction systems, the ensemble prediction experiment based on the CNOP-P-RP scheme is more skillful and reliable for probability forecast of precipitation and surface elements in this process. Further analysis shows the variation of piedmont temperature gradient and surface cold pool caused by the uncertainty of vertical diffusion plays an important role in convective triggering and rainstorm development. From 00:00 BT to 04:00 BT 7 May, the enhancement of vertical diffusion near the center of heavy precipitation in Huadu strengthened the vertical transport of heat, momentum and water vapor. The melting of snow and graupel particles is the main reason for the increase of precipitation, indicating that although the formation of raindrops is mainly caused by condensation near the top of boundary layer and collision of cloud water, the effect of ice particles cannot be ignored. From 04:00 BT to 08:00 BT 7 May, with the strengthening of water vapor transport and upward movement, a more active warm rain process dominated the increase of precipitation in the heavy precipitation center at Zengcheng. This study preliminarily proves the feasibility of the CNOP-P-RP scheme in describing the uncertainties in convection-permitting ensemble prediction systems, and provides some references for the improvement of warm-sector torrential rain forecast in South China.
Health impact and economic benefit of temperature forecast on cardiovascular mortality in Beijing
 doi: 10.11676/qxxb2023.20220122
[Abstract](5) [PDF 1181KB](5)
Influence of the interdecadal variation of boreal summer intraseasonal oscillation on the abrupt decrease of multiple tropical cyclones in the western North Pacific
ZHANG Ke, FANG Juan, CONG Chunhua
 doi: 10.11676/qxxb2023.20220044
[Abstract](59) [FullText HTML](12) [PDF 1988KB](25)
Using best-track data of typhoon, the bimodal ISO index and global daily outgoing longwave radiation data, we study the possible mechanism of the interdecadal variation of boreal summer intraseasonal oscillation (BSISO) that has caused sudden decrease of multiple tropical cyclones (MTC) in the western North Pacific (WNP) after 1996/1997. The analysis shows that only the "MTC3" events, which contain 3 or more typhoons, abruptly decreased after 1996/1997. They are more likely to occur in the BSISO active phase with a slower propagation speed and longer low-frequency convection. Moreover, the MTC3 events have relatively low requirements for the BSISO amplitude. After 1996/1997, the eastward propagation range of the BSISO convection reduced, the period prolonged, and the days of BSISO active phase decreased, resulting in a significant weakening of low-frequency signals to the east of 140°E. Tropical WNP tended to remain in inactive phase for a long time during this period. When a typhoon pre-exists in the WNP, the southeastward-propagating Rossby dispersion wave train casused by it always dissipates without coupled low-frequency convection to the east of 140°E, which leads to the sudden decrease of MTC3 events after 1996/1997.
Analysis on the development and maintenance mechanism of the extreme heavy rainfall in Henan on July 2021
Chyi Dorina, Wang Xiuming, Yu Xiaoding, Zhang Junhui
 doi: 10.11676/qxxb2023.20220014
[Abstract](155) [FullText HTML](17) [PDF 2770KB](63)
The frontogenesis, atmospheric diabatic heating and net water vapor budget are analyzed to reveal the development and maintenance mechanism of the synoptic scale system of the Henan extreme heavy rainfall from 19 July to 21 July in 2021 using automatic weather station observations and the fifth-generation European Center for Medium-Range Weather Forecasts atmospheric reanalysis data. Results show that Henan is located in the saddle area between the Northwest Pacific subtropical high (NPSH) and the continental high. In this situation, the convergence in low levels is collocated with the divergence at high levels, which is conducive to the development and maintenance of the low-pressure system at 500 hPa during the extreme heavy rainfall. The frontogenesis mainly occurs in the lower troposphere and is consistent with the θse intensive region. The horizontal divergence term and horizontal deformation term play equally important leading roles in the frontogenesis. The horizontal distribution of the apparent heat source 〈Q1〉and moisture sink 〈Q2〉 coincide with the area of heavy rainfall. However, vertical distributions show significant differences between Q1 and Q2. Q1 features an obvious single peak structure with the heating center in the middle and upper troposphere, while the large value area of Q2 is evenly distributed at 850—400 hPa. Q1 is larger than Q2 in the middle and upper troposphere. The potential temperature vertical transport term dominates in Q1 and the specific humidity horizontal transport term dominates in Q2, indicating that the release of regional-scale strong condensational latent heat has a positive feedback effect on the precipitation. With the continuous strengthening of the easterly air flow from the north side of typhoon Fireworks (2106), the strong wind shear and topographic uplift lead to an abnormally strong convergence of water vapor in the boundary layer. The net inflow of water vapor from the east and west dominates the total water vapor budget. The extremely strong water vapor transport in the boundary layer from the east plays a key role in maintaining and strengthening the extreme rainfall process.
Differences in spatiotemporal variation and risk zoning of four types of extreme cold events in Jiangsu province
WANG Ning, XIE Zhiqing, GAO Ping, LI Xin, ZHANG Lingling, MIAO Qian
 doi: 10.11676/qxxb2023.20220058
[Abstract](62) [FullText HTML](8) [PDF 16191KB](18)
Based on observations collected at 70 stations in Jiangsu province from 1961 to 2020, spatial and temporal variations of four types of cold events are investigated first. A total of 14 evaluation indicators related to cold damages are selected to build the dangerousness index. Using the population and GDP data, the dangerous level and risk-zoning of cold events are then assessed. The results are as follows. (1) Cold air outbreaks, frost events and cold-rainy events frequently occur in Jiangsu during 1961—2020, while the frozen events have a small total number of occurrence days. Cold air outbreaks and frost events have the maximum number of occurrence days during 1961—1980, while cold-rainy events and frozen events reach the maximum occurrence in 2001—2020. (2) Cold air outbreaks occur frequently in central and southern Jiangsu Province during 1961—2020. Correspondingly, frost events occur more frequently over the northern areas than over the southern part of Jiangsu province. The number of days with cold-rainy events shows a decreasing tendency from southwest to northeast of Jiangsu province. Frozen events frequently occur in the southwest and northwest of Jiangsu, where frozen events have a spatial distribution similar to that of precipitation. (3) High level of danger for cold air outbreak and frost events is located in the north of Jiangsu province, while the high level of danger for cold-rainy events is found in the southwestern areas of Jiangsu province. The high level of danger for frozen events appears in both south and north of Jiangsu province. The composite dangerousness of the four types of cold events shows that the high level of danger is located in the north and southwest of Jiangsu Province and the low level appears in central and southeastern areas. (4) There exist notable differences in the spatial distribution and area of high risk between the population and GDP, which are mainly resulted from the spatially discontinuous hazard-bearing body under the condition of a similar meteorological environment in Jiangsu province.
The dynamical-statistical extended-range prediction of precipitation and extreme precipitation events over southern China
ZHANG Keyue, LI Juan, HSU Pang-chi, ZHU Zhiwei
 doi: 10.11676/qxxb2023.20220061
[Abstract](127) [FullText HTML](16) [PDF 2392KB](39)
How to improve the extended-range predictive skill is a hotspot and frontier research issue, which is crucial for bridging the gap in seamless prediction system. Based on the observations and reanalysis data during December 2005−August 2014, the Singular Value Decomposition analysis is used to reveal the highly coupled modes between the low-frequency precipitation over southern China and intraseasonal tropical convection/mid-latitude wave trains in boreal winter and summer, respectively. The BCC-CPS-S2Sv2 (hereafter referred to as BCC S2S) model provided by China Meteorological Administration is used to construct a set of dynamical-statistical models for subseasonal prediction of low-frequency precipitation anomalies over southern China using the statistical downscaling method. The BCC S2S model participates the Subseasonal-to-Seasonal Project and exhibits reasonable skills on the forecast of rainfall anomalies over most of southern China at 10—15 d forecast lead times during the independent prediction period of December 2014−August 2019. However, the dynamical-statistical model outperforms the BCC S2S model on precipitation forecast in terms of temporal variability over coastal region of South China (north of the Yangzi River) during winter (summer) and the spatial distribution and extreme events beyond 15—20 d forecast lead. The idea and method proposed by this study can be widely applied to extended-range prediction of other regional meteorological elements and extreme events.
Improved interannual predictability of winter North Atlantic Oscillation with a weakly coupled data assimilation scheme
LI Feifei, XU Caiyan
 doi: 10.11676/qxxb2023.20220062
[Abstract](43) [FullText HTML](7) [PDF 1882KB](6)
The North Atlantic Oscillation (NAO) is one of the major modes of atmospheric circulation over the North Atlantic in winter, and its interannual variabilities play an important role in climate variabilities over many regions of the world. However, the skills for its prediction are not good enough at present. In this paper, a weakly coupled data assimilation system based on global observational atmospheric data is established using the Dimensional-Reduced Projection Four-Dimensional Variation (DRP-4DVar) assimilation method, which can directly assimilate monthly mean reanalysis data. The results of decadal hindcast experiments indicate that this system can significantly improve the hindcast effects of interannual variabilities in wintertime NAO and interannual variabilities of related winter surface temperature over northern Europe, the eastern United States and northern Eurasia, and the correlation coefficients are all above the 0.05 significance level t-test at least. These improvements are mainly attributed to the freely developed air-sea coupling in the coupled model that can store atmospheric observations in its ocean component, and thus improve the spatial and temporal variabilities in the "tripole" pattern of the Sea Surface Temperature (SST) distribution over the North Atlantic and related "tripole" SST temporal variabilities. This study emphasizes the importance of the accuracy of initial states of the coupled model in improving the hindcast abilities of the coupled model on the simulation of wintertime NAO interannual variabilities.
Analysis of a damaging wind case caused by bow echo in the environment of cold vortex over North China Plain
XU Changyi, ZHANG Lina, XIAO Xian, WANG Yan
 doi: 10.11676/qxxb2023.20220024
[Abstract](398) [FullText HTML](20) [PDF 3759KB](69)
In order to improve the study of environmental evolution and mechanism of strong winds induced by bow echo, multi-source observations (Doppler radar, wind profiler, meteorological tower in Tianjin and automatic weather station data at 5 min interval) and reanalysis data of the ECMWF ERA5 (spatial resolution of 0.25° and temporal resolution of 1 h) are comprehensively used to analyze the nocturnal bow echo event in North China Plain on 25 June 2020. Results indicate that this bow echo event developed under favorable weather conditions. The cold dry air behind the 500 hPa cold vortex superimposed on the warm moist southwesterly airflow at 850 hPa, which is conducive to the occurrence of convective storm. Characteristics of the convective storm evolution can be summed up as three stage: Supercell, bow echo and comma echo. The environmental condition at the supercell stage is characterized by moderate Convective Effective Potential Energy (CAPE) and 0—6 km wind shears, while at the bow echo and comma echo stages CAPE is low and 0—6 km wind shears are high. In the supercell stage, the sounding curve shows an "X"-shaped distribution. The negative buoyancy effect is the primary contributor to the surface gale. Meanwhile, the downward transport of momentum and cold pool high-density air are helpful for the formation of surface gale. In the bow echo stage, due to the combined effects of low-level warm advection and surface radiative cooling, a strong temperature inversion layer occurred near the surface, and the vertical temperature lapse rate between 850—500 hPa increased. The effects of negative buoyancy, downward transportation of momentum and cold pool high-density air all strengthened compared with that in the previous stage, resulting in the formation of the 13th grade disastrous gale. In the comma echo stage, the 850—700 hPa dry layer weakened, and the negative buoyancy effect is similar to that in the supercell stage. The effects of downward transport of momentum and cold pool density are similar to that in the bow echo stage, resulting in the formation of surface gale. Finally, the environmental evolution and mechanism of bow echo conceptual model are summarized.
A study on objective forecast algorithm of 100-meter gust based on gust coefficient model
Yang Lu, WANG Xiaoli, SONG Linye, CHEN Mingxuan, QIN Rui, Cao Weihua, WU Jiankun
 doi: 10.11676/qxxb2023.20220052
[Abstract](97) [FullText HTML](10) [PDF 5224KB](38)
The rapid development of economy and culture in Beijing-Tianjin-Hebei region has a higher requirement for instantaneous strong wind forecasts. Correctly estimating and predicting instantaneous strong winds on the ground level in winter, especially accurate high-resolution grid-point forecasting of gusts under complex terrain condition, is of great significance for improving the service for major Winter Olympics events, the safe operation in the capital and surrounding cities, and disaster prevention and mitigation capabilities. This study establishes a relationship between the gust coefficient and wind speed, wind direction and terrain height based on long-term series of observation data in Beijing-Tianjin-Hebei. Combined with objective statistical analysis method, gust observation data fusion technology and grid point deviation correction technology, an objective gust forecast method is developed, which not only retains the model physical parameters and local climate characteristics, but also utilizes the grid point deviation correction technology. The results of batch verification and case analysis during the Winter Olympics show that the average absolute errors in the Zhangjiakou competition area and the Yanqing competition area are below 2.3 m/s and 3.0 m/s, respectively. The forecast score of gust wind speed above level 8 in the Yanqing competition area is above 0.5. It solves the bottleneck problem of large gust prediction errors and meets the on-site service requirements of major Winter Olympic activities.
Winter Olympic comprehensive meteorological observation platform of Haituo Mountain and the research progress
WANG Qianqian, CHEN Yichen, CHENG Zhigang, YU Bo, CHANG Chen, ZHANG Man, LI Siteng, Luo Li, WU Yongxue, PAN Yubing, LI Ju, ZHANG Jingjiang, LIAO Zhiheng, DOU Youjun, QUAN Jiannong
 doi: 10.11676/qxxb2023.20220029
[Abstract](99) [FullText HTML](22) [PDF 53588KB](47)
Meteorological conditions and support are important for the success of the Winter Olympic Games. The competition area is located at the Haituo Mountain, where the terrain is complex with steep slopes and large vertical drop. Such a complex terrain makes it difficult to carry out observations. The lack of meteorological data becomes a key factor that limits the reliability of fine forecasts over the competition area, and poses a serious challenge for the Winter Olympic Games meteorological service. Beijing Meteorological Bureau organized and conducted multi-scale integrated meteorological observations at the Haituo Mountain. These observations cover mesoscale, small scale and microscale with the aim of observing three-dimensional winds, temperature, humidity, cloud, visibility, surface turbulence, radiation, and so on. The comprehensive observations will improve our understanding of characteristics and mechanism of high-impact weather events in complex mountainous areas and provide data for improving the forecasting model. This paper systematically introduces the scientific objectives, observation layout, observation contents and preliminary observation and analysis results of the integrated meteorological observation system at the Haituo Mountain, and expounds the further research plan.
Machine learning-based influencing factors analysis and estimation of winter temperature anomalies in China
WU Weichen, WEI Fengying, WANG Yaqiang, ZHU Enda
 doi: 10.11676/qxxb2023.20220078
[Abstract](91) [FullText HTML](9) [PDF 6047KB](30)
In the study, the mean winter temperature collected at 160 stations in China from 1951 to 2021 and a number of atmospheric circulation and sea temperature indices are used to investigate the relationship between the distribution of winter temperature anomalies and the atmospheric circulation and external forcing factors. A model of fitting is also established by using machine learning methods. In this way, we can understand to what extent the screened combination of influencing factors can explain the distribution of winter temperature anomalies in China. The Least Absolute Shrinkage and Selection Operator (Lasso) algorithm is used to extract the influencing factors related to winter temperature anomalies. In addition, to reflect the nonlinear relationship between these factors, the original features are augmented to polynomial features using Taylor's formula. To further study the nonlinear relationship between the selected factors, the least squares gradient boosting decision tree (LS-GBDT) algorithm is used to estimate and fit winter temperature. Experiments are conducted on the training samples and test samples respectively and have achieved good results. The result verifies that machine learning can be used to screen and analyze the importance of factors affecting winter temperature anomalies more reasonably, and the estimation model established can to a certain extent reflects the nonlinear relationship between the factors influencing the climate system and winter temperature. This work provides a new way to simulate and estimate distribution of the winter tmperature anomalies in China.
The observational characteristics and mechanism analysis of low-level meso-γ-scale vortices during the extreme rainfall event in Shenyang on 16 August 2019
YANG Lei, ZHENG Yongguang, YUAN Zipeng, YUAN Chao, JIANG Chao, CHEN Yu
 doi: 10.11676/qxxb2023.20220023
[Abstract](161) [FullText HTML](31) [PDF 2936KB](56)
The urban area of Shenyang was affected by a rainfall system with low-level meso-γ-scale vortices on 16 August 2019. This system caused record high hourly precipitation (102 mm) since the observations started in 1951. In order to improve the analysis and forecasting ability of heavy rain caused by such vortices, multi-source observations and ERA5 reanalysis data are comprehensively used to analyze the characteristics of the low-level meso-γ-scale vortices in this process, the environment for their generation and their roles in the formation of the torrential rain. The results show that during this process, Shenyang was located in the front of the Northeast Cold Vortex at 500 hPa and in the water vapor conveyor belt on the west side of the residual vortex of typhoon "Likima" in low levels. Moreover, a near-ground near-dry adiabatic lapse rate prevailed in the urban area of Shenyang in the afternoon with lower lifted condensation level and increasing vertical wind shear. At nightfall, the meso-γ-scale convergent wind field in the urban area of Shenyang triggered the local storm, and the cold vortex storm then entered Shenyang. The storm group merged in the area with anticyclonic rotation of the local storm. The merged storm strengthened this extreme precipitation event, and a meso-γ-scale vortex pair with a life history of 30 minutes appeared in lower levels, followed by a rare phenomenon of strengthening of converging anticyclonic vortex. Compared with the statistical characteristics of mesocyclones in China, this low-level shallow vortex demonstrated a short life span with small scale and slow moving speed and strong vertical vorticity. All the automatic weather stations with precipitation exceeding 10 mm in 5 minutes after the vortex are located in the area between the vortex pair, and the record high hourly precipitation occurred since observations started in 1951. The strength and extent of the heavy precipitation can be characterized by the strength of the vortex's rotation, the height of its extension, and the distance between the two vortices. The occurrence of extreme precipitation events requires strong rainfall intensity and long duration time. The merged storm in this process has the characteristics of warm clouds and low centroid echo in radar observations. The early local storm precipitation also reduced the difference between ground temperature and dew point, which ensured high precipitation efficiency. Furthermore, the updraft near the ground generated by low-level vortex promoted the growth and collision of raindrops, thereby enhancing the rain intensity. The strong rotation of the vortex caused an updraft near the ground, which was conducive to the re-development of storms and prolonged the precipitation duration time. The reason for the emergence and strengthening of the low-level anticyclonic vortex is likely attributed to the following factors. The low-level quasi-linear outflow boundary of the cold vortex storm formed a horizontal vortex tube from north to south. Under the downward twisting action of the downdraft in the initial precipitation, meso-γ-scale vortex pair appeared near the ground, and since the environmental wind shear vectors rotated counterclockwise with altitude, the clockwise rotation was more conducive to the strengthening of anticyclonic storms. This is consistent with the theoretical research. In addition, this anticyclone was closer to the strong updraft area in the merged storm, and it could also be reinforced under its stretching. Finally, the formation mechanism of this low-level meso-γ-scale vortices and the rainstorm model are summarized, which provide a reference for future weather analysis and forecast research.
Research on splitting process flow field characteristics of the hail supercell before squall based on Doppler weather radar
 doi: 10.11676/qxxb2023.20220146
[Abstract](27) [PDF 8755KB](10)
PENG Yanyu GAO Qianqian LIU Yu
 doi: 10.11676/qxxb2023.20220185
[Abstract](40) [PDF 4617KB](7)
Research on the refined characteristics of precipitation in the wide-ranging rain belt in the Yangtze-Huaihe River Valley
 doi: 10.11676/qxxb2023.20220107
[Abstract](19) [PDF 2421KB](6)
Long-term evolution characteristics and source analysis of black carbon aerosol at Waliguan Station,Qinghai-Tibet Plateau.
 doi: 10.11676/qxxb2023.20220110
[Abstract](14) [PDF 1753KB](2)
Influence Analysis of Quasi-Biweekly Oscillation Characteristics on Typical Flood Years in the Lower Reaches of the Yangtze River
 doi: 10.11676/qxxb2023.20220148
[Abstract](31) [PDF 2714KB](14)
Introduction of radar quantitative precipitation estimation mosaicking system using S-band and X-band phase-array polarimetric radars in Shenzhen
 doi: 10.11676/qxxb2023.20220156
[Abstract](75) [PDF 3884KB](24)
Temporal and spatial variation characteristics of pan evaporation in China during 1960-2021 based on homogenized dataset
 doi: 10.11676/qxxb2023.20220114
[Abstract](22) [PDF 3551KB](10)
Design of a regional chemistry-weather coupled 3D-Var system and preliminary analysis experiment for aerosol observation
 doi: 10.11676/qxxb2023.20220069
[Abstract](23) [PDF 2256KB](10)
Estimation of Land Surface Heat Fluxes in Beijing-Tianjin-Hebei region using Maximum Entropy Production Model
 doi: 10.11676/qxxb2023.20220116
[Abstract](17) [PDF 1668KB](6)
Atmospheric inversion layer remote sensing based on Fengyun satellite infrared hyperspectral data
 doi: 10.11676/qxxb2023.20220087
[Abstract](326) [PDF 1860KB](10)
Climatic Characteristics of Thunderstorm Gales in Northeast China and Its Relation with Northeast Cold Vortex
 doi: 10.11676/qxxb2023.20220126
[Abstract](83) [PDF 2002KB](35)
Imporvment and evaluation of precipitation nowcasting algorithm based on SWAN
 doi: 10.11676/qxxb2023.20220066
[Abstract](51) [PDF 2367KB](23)
Revisiting the Principle of Analogue-Based Forecasts: Recent Advances in Dynamical-Statistical-Analog Ensemble Forecast Theory and Its Application to the Prediction of Landfalling Typhoon Precipitation
 doi: 10.11676/qxxb2023.20220064
[Abstract](42) [PDF 2753KB](9)
Assessment of intraseasonal characteristics of precipitation over East Asia in GRIST model summer climate backtest
 doi: 10.11676/qxxb2023.20220120
[Abstract](94) [PDF 3035KB](33)
A Typhoon Intensity Correction Method Based on Ensemble Numerical Forecast Products
 doi: 10.11676/qxxb2023.20220026
[Abstract](49) [PDF 845KB](20)
A deep learning based fusion precipitation nowcast method and its application study over East China
 doi: 10.11676/qxxb2023.20220081
[Abstract](113) [PDF 3808KB](56)
Research on frequency correction algorithm for spaceborne precipitation measurement radar and ground-based weather radar
 doi: 10.11676/qxxb2023.20220093
[Abstract](39) [PDF 428KB](11)
Comparative Analysis of Biweekly Oscillation Characteristics of Precipitation during Meiyu Period in the Yangtze Huaihe River basin in 2016 and 2020
 doi: 10.11676/qxxb2023.20220075
[Abstract](36) [PDF 23132KB](14)
The interactions between stratosphere and troposphere during the influence of blocking events in the extratropical northern hemisphere on cold air outbreaks in East Asia
 doi: 10.11676/qxxb2023.20220094
[Abstract](33) [PDF 5058KB](12)
Haze Detction by multi-spectral channels of FY-3/MERSI
 doi: 10.11676/qxxb2023.20220079
[Abstract](37) [PDF 3672KB](6)
Characteristics of dual-polarization structure and raindrop size distribution measured by a ground-based disdrometer of a squall line in Shandong
 doi: 10.11676/qxxb2023.20220070
[Abstract](79) [PDF 975KB](32)
Analysis of extreme convective winds caused by two different types of storms in a severe convective process
 doi: 10.11676/qxxb2023.20220050
[Abstract](99) [PDF 3667KB](56)
Joint effects of sea surface temperature over north Atlantic and tropical Indian Ocean on the interdecadal variation in Songhua River Basin warm season precipitation
 doi: 10.11676/qxxb2023.20220068
[Abstract](44) [PDF 2492KB](15)
2022year No.6
Display Method:
As a kind of short-period severe weather disaster, hails often have severe impacts on agriculture, construction, electricity, transportation and even lives and properties, etc. Therefore, hail suppression is widely concerned worldwide. This paper provides a detailed review of research progress in hail formation mechanism and hail cloud physics from perspectives of mechanism, technology, scientific experiments and effect evaluation of hail suppression for the purpose to gain in-depth knowledge of domestic and international development of hail suppression in both theoretical and practical fields, improve our understanding of scientific problems in hail suppression, and provide references for promoting theoretical research and technological progress of hail suppression in China. Major results as follows: (1) The "theory of zone of accumulation" and the "theory of cyclic growth" are the most common theories of hail formation. Limited by the early radar observation technology and the lack of complete numerical models for hail simulation, the early knowledge of the hail formation mechanism has certain limitations. (2) Hail embryos are generally divided into frozen drop embryos and graupel embryos. Frozen drop embryos are formed by the freezing of supercooled raindrops while graupel embryos are formed by the growth of collision and freezing of ice crystals and snowflakes. What type of hail embryo is dominant in the hail cloud mainly depends on temperature of the cloud base. The development of hail clouds depends on key factors such as water vapor condition, dynamic instability condition, and vertical wind shear, etc. (3) The mechanism of hail suppression mainly follows two technical lines, "hail suppression by seeding" and "hail suppression by explosion". "Competing interests" and "early rainfall" are the two most widely used theories of seeding among the six common hypotheses of hail suppression on which hail suppression operations are designed. (4) Technically, the hail suppression operations mainly include seeding hail clouds with artificial ice nuclei by aircraft, rocket launcher, ground generator, etc., or launching shells with artificial ice nuclei by ground artillery, which can affect the growing process of hail to suppress or weaken the growth of hail. (5) A large number of field experiments of hail suppression have proved that there are regional differences in operation effect of hail suppression. It is necessary to formulate and develop regional hail suppression technology systems adapted to local conditions according to the characteristics of hail clouds and hailstorms in different regions. (6) Evaluating the effect of hail suppression is still a bottleneck problem that limits the development of hail suppression technology. The methods commonly used to assess the effect of hail suppression mainly include statistical, physical, and numerical simulation evaluations, which need further improvement. Due to the rapid changes in hail clouds and short hailstorm processes, there exits great difficulties in the timeliness of implementation of hail suppression operation and the effect evaluation of hail suppression. It will start from carrying out fine detection of hail clouds based on a variety of observation equipment and comprehensive field experiments of hail suppression with scientific design. Statistical, physical and numerical simulation approaches should be combined to evaluate the effect of hail suppression and promote further development of hail suppression technology in future.
Composite methods are applied to analyze atmospheric observations and the NCEP/NCAR Final Operational Global Analysis data as well as the Tibetan Plateau vortex (TPV) and shear line yearbooks from 1998 to 2018 to reveal the ambient field characteristics for the groups of the Tibetan Plateau vortices that move eastward following quasi-straight long-path (QSLTPVs) and multi-turning path (MTTPVs), respectively. The leading factors that lead to the TPVs's turning are also discussed. The results show that the ambient field characteristics common for long-lasting QSLTPVs and MTTPVs activities are that there are obvious weather systems affecting TPVs. And the subtropical high is located to the southeast of the TPVs, while the east and west segments of jet stream exist in the upper levels to the north of the TPV. These systems promote positive vorticity advection into the TPVs and there is positive divergence region above the TPVs. Potential vorticity in the upper levels are transported downward to TPVs. The difference in ambient field conditions between the QSLTPVs and the MTTPVs is obvious, too. The MTTPVs are accompanied by strong tropical low-pressure activities. They are blocked and forced to turn under the influences of the sub-tropical high, the westerly wind belt, the topical low-pressure systems and their interaction. The QSLTPVs move eastward in the ambient background field dominated by westerly synoptic systems. And the QSLTPVs are more affected by cold air, southwesterly flow and upper-level front belt than the MTTPVs. These systems lead to stronger positive vorticity advection, larger potential vorticity, stronger baroclinicity and positive divergence in upper levels. The main factors causing the turning of MTTPVs are that the TPVs are weakened and blocked by the ambient field conditions, and the downward transport of high-level potential vorticity to the TPV results in strong positive vorticity in the west of the TPV. Thereby, the TPV moves to the area where it becomes stronger, which explains why the TPV makes turn.
An EF1 tornado occurred in the northern coast of the Bohai under the background of cold vortex on 16 August 2019. Using the Yingkou S-band dual-polarization Doppler weather radar data, surface automatic weather station (AWS) observations at 5 min interval, the Panjin wind profile radar data and ERA5 reanalysis data, the environmental background, the structure and formation of the tornadic storm and the tornadogenesis are studied. The results show that the tornado occurred under the background of a cold vortex at 500 hPa, and it was located in the water vapor conveyor belt on the west side of the residual vortex of typhoon "Lekima". The environmental condition is characterized by weak vertical wind shear and strong low-level thermal instability. The Yingkou dual-polarization radar is located 15 km away from where the tornado originated. The hook echo, the descending reflectivity core (DRC), the weak echo hole (WEH), and the tornadic debris signature (TDS) in mini supercell are detected by the radar. The outflow of the decaying thunderstorm gust front moved westward, while the sea breeze front near Yingkou slowly moved eastward. The two boundary layer convergence lines merged, leading to the forming of γ-mesoscale vortex under the influence of horizontal shear instability. The intersection of outflow boundaries, the large positive ambient buoyancy and the vertical perturbation pressure gradient associated with the low pressure induced by the middle level mesocyclone jointly produced strong updrafts. The collocation of the updrafts and the γ-mesoscale vortex played a critical role for the genesis of misocyclone by strong stretching. The combination of the maximum rotation velocity and the minimum diameter of the misocyclone corresponded to the tornadogenesis, and the separation of the misocyclone and the mesocyclone in the middle level led to the dissipation of the tornado.
To improve the analysis and forecast of tropical cyclone (TC) wind circle, the asymmetric characteristics and causes of wind circle maximum radii of 55.6 km/h, 92.6 km/h and 118.5 km/h for TCs at their maximum intensity during 30 June 2015 to 31 December 2020 are studied using the TC data released by the National Meteorological Centre (NMC) and data extracted from ERA5 reanalysis. Statistical results show that the 55.6 km/h wind circle radius of TC is the most asymmetric, followed by the 92.6 km/h and 118.5 km/h wind circle radii. The 55.6 km/h, 92.6 km/h and 118.5 km/h wind circle maximum radii of TC with asymmetric distribution are mostly located at the north east (NE), southeast (SE) and northwest (NW) quadrants. The 55.6 km/h and 118.5 km/h wind circle maximum radii of the same TC are roughly located at the same quadrant. Single quadrant distribution TCs and multi-quadrant distribution TCs of 55.6 km/h wind circle are divided into four types according to quadrant distribution. By analyzing the generation season, surface wind and the causes of asymmetric distribution of TC with single quadrant distribution of 55.6 km/h wind circle, it is found that the generation of these four types of TC have obvious seasonal characteristics. The surface wind in different quadrants of TC shows asymmetric characteristic. The asymmetric distribution of wind circle is closely related to the asymmetry of potential height gradient in different quadrants caused by the interactions between TC and other weather systems, including the Western Pacific Subtropical High, the southwesterly air flow and surface cold high pressure, etc.

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