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28 February 2018, Volume 34 Issue 1 Previous Issue    Next Issue

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Environmental and radar echoes characteristic analysis of two thunderstorm gale processes in Hubei province in 2013 LIU Xi-wen, LI De-qin, WEI Hui-hong, XU Shuang-zhu, GOU A-ning 2018, 34 (1):  1-10.  doi: 10.3969/j.issn.1673-503X.2018.01.001 Abstract ( 262 )   PDF (9805KB) ( 457 )   Save Two thunderstorm gale processes happening in Hubei province on May 23 and August 18,2013,called "523" and "818" processes,respectively were analyzed.The thunderstorm gales were investigated through analysis of the weather situation,vertical structure,physical parameters of the atmosphere and Doppler radar echo using conventional weather,NCEP (National Centers for Environmental Prediction) reanalysis and radar data.The results indicate that the "523" process is a typical supercell forming at Shiyan region under the condition of high altitude cold trough shifting eastward.The "818" process is a severe convection result due to the combined interaction between unstable conditions and weak cold air at the surface under the influence of a subtropical high outside northeastern airflow and a landing typhoon.The atmospheric parameters of the two processes have some similarities with a high value in CAPE (Convective Available Potential Energy) (>1 300 J·kg-1),a dry adiabatic decreasing condition in the lower level,and a poor water vapor condition in the entire level.The vertical distribution of θse shows that there is an invading dry air in the mid-low level during the two weather processes.Some convection parameters,such as K index and vertical wind shear,show a significant difference between the two processes.It reveals the complexity and uncertainty to predict atmosphere parameters of a thunderstorm gale weather.The main radar echo characteristics in the "523" process include mesocyclone,hook echo,‘V’ notch and echo pendency.Those in the "818" process include gust front,bow echo,and echo center quickly dropping to the ground.A typical mid-altitude radial convergence and areas of large gale speed value are also observed in the two processes.These radar echo characteristics,such as Mesocyclone,hook echo,gust front,mid-altitude radial convergence,are good indicators for the forecasting of a thunderstorm gale. References | Related Articles | Metrics

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Characteristics analysis of “20160630” local heavy rain and its predictability in Shenyang LI Dian, CHAI Xiao-ling, LI Chong, LU Yang, WU Yu-tong, CUI Jing-lin 2018, 34 (1):  11-21.  doi: 10.3969/j.issn.1673-503X.2018.01.002 Abstract ( 252 )   PDF (12311KB) ( 304 )   Save The conventional observation data,the European Centre for Medium-Range Weather Forecasting(ECMWF)numerical weather prediction products,the Weather Research and Forecasting Model(WRF)data,and radar detection products were used to study a local heavy rain process happening on June 30,2016,in Shenyang.The evolution of the precipitation system,short-term and very short-term predictability,and model production application were analyzed.The results show that this heavy rain has clear characteristics for short-term prediction,but it does not meet the threshold values obtained from the past rainfall forecasts in Liaoning province.The 90% percentile of accumulated precipitation and EFI (Extreme Forecast Index) forecasted by the ECMWF ensemble model indicate the extreme feature of this heavy rain process.The large vertical wind shear happening in the southern Liaoning results in sudden changing and recurring convective cloud clusters.All models analyzed in this study can predict the distribution characteristics of rainfall,but the location of precipitation needs improving.The ECMWF forecasts from different start times have relatively large uncertainties.The forecast result from the last starting time has a good reference value.The WRF model can be used to analyze the evolution characteristics of convective cloud clusters and therefore we should focus on the investigation of evolution processes of convective clouds using the WRF model. References | Related Articles | Metrics

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Research on air temperature product examination of three numerical forecast and a method of error correction WANG Huan-yi, TAN Zheng-hua, YANG Meng, ZHANG Qiao, JIANG Lin-shan 2018, 34 (1):  22-29.  doi: 10.3969/j.issn.1673-503X.2018.01.003 Abstract ( 352 )   PDF (590KB) ( 617 )   Save Using the observed data and three numerical weather prediction products of T7 online (T7),ECMWF and T639,the air temperature accuracy rates and prediction errors were tested and analyzed from January of 2014 to December of 2015 in Benxi city.With the BP neural network algorithm,a air temperature prediction error correcting model was established based on the error analyses of the models.The results show that,for the annual test,the accuracy rate of the minimum air temperature is higher than that of the maximum air temperature for the three models.The forecasting effects of the minimum air temperatures in summer and autumn are better than those in winter and spring.While for the maximum air temperature predictions,the performance of T7 is superior to those of EC and T639.The predication accuracy rate of these models decreases under a large air temperature disturbance.The forecasting errors of average minimum air temperatures for these models are less than 2.00℃.There is a big difference in the maximum air temperature forecasting among these models.T7 has the smallest error in the maximum air temperature forecasting.The systematic deviation of T639 is higher,with -1.34℃ and -2.87℃ for the minimum and maximum air temperatures,respectively.After correcting,the average absolute error decreases from 2.40℃ to 1.40℃,the systematic deviation and root-mean-square error are significantly reduced,and the forecasting accuracy rate obviously is improved from 50% to 80%.It indicates that this approach is valuable to be used in operation. References | Related Articles | Metrics

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Analysis of identification criterion of precipitation phase in Anqing city ZHANG Li, XU Peng-fei, WU Sheng-ping, DONG Fang-you 2018, 34 (1):  30-37.  doi: 10.3969/j.issn.1673-503X.2018.01.004 Abstract ( 243 )   PDF (819KB) ( 408 )   Save Using the ground meteorological observations and meteorological sounding data during November to March from 1999 to 2014 in Anqing station,this paper analyzed the temporal-spatial distribution characteristics of different precipitation phases and the performance and transform of weather systems affecting conversion process between rain and snow.The relationships of different precipitation phases with temperature and thickness stratification were investigated under three weather phenomena,i.e.,conversion between rain and snow,snow,and ice rain or ice particles.The results reveal that solid precipitation in Anqing city mostly appears from November to March.The phase transform is better identified when considering the temperature at 850 hPa and between 850 hPa and ground.The precipitation is liquid when the temperatures at 850 hPa,925 hPa,1000 hPa,and surface are larger than or equal to -4℃,-4℃,-1℃,and 1℃ respectively.The further decrease in temperature below 850 hPa level results in the transforming from rain to snow.Except for the above temperature conditions for transforming from rain to snow,direct snow will happen when the temperature at 850 hPa decreases to -6℃.For the transforming between rain and snow,the critical values of thicknesses for 850-700 hPa and 1000-850 hPa are 154 dagpm and 129 dagpm,respectively.When they are less than critical values,it is snow;when they are larger than critical values,it is rain.The atmospheric level at 0℃ (L0) can be regarded as one of an index for the phase conversion of precipitation.The transforming from rain to snow will happen when L0 is approximately equal to 1000 hPa.The inversion temperature phenomenon generally appears during the precipitation period.When a warm layer above 0℃ exists between 850-700 hPa,it is ice rain or ice particle.While the temperature at inversion temperature layer is less than 0℃,it is snow. References | Related Articles | Metrics

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Characteristics of warm-sector rainstorm with southerly flow during early-flood season in Liuzhou area before or after summer monsoon in the South China Sea LIU Lei, ZHANG Ling-yun, CHEN Mao-qin, SU Xiao-ling, YUAN Ma-qiang 2018, 34 (1):  38-44.  doi: 10.3969/j.issn.1673-503X.2018.01.005 Abstract ( 230 )   PDF (3971KB) ( 385 )   Save The characteristics and circulation patterns of warm-sector rainstorms with the southerly flow in Liuzhou area occurring before or after the summer monsoon over the South China Sea from 2010 to 2015 were analyzed,using observational data at conventional meteorological stations and regional automatic weather stations,as well as reanalysis data of National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) with the resolution of 1°×1°.The results indicated that 72.7% of the warm-sector rainstorms with southerly flow occur after the break of summer monsoon over the South China Sea.The warm-sector rainstorms occurring before or after the summer monsoon over the South China Sea are characterized by a transport of positive vorticity at 500 hPa and a convergence zone near or below 925 hPa.The jets at super-low altitudes and the strong convergence of southerly flow within the boundary layer are the important triggering mechanism of the warm-sector rainstorms.The topography in the northern part of Liuzhou also favors the occurrence of a warm-sector rainstorm,leading to a higher occurrence frequency of warm-sector rainstorm in this region.Before the occurrence of summer monsoon in the South China Sea,the wet layer above the rainstorm area is very shallow,the invasion of dry and cold air at the middle levels favors the instability of atmospheric at upper levels of the rainstorm area,and the subtropics westerly jet is the major mechanism of divergence at upper levels.While after the occurrence of the summer monsoon in the South China Sea,the high pressure at South Asia is the mechanism of divergence at upper levels and the divergence is stronger at upper levels than lower levels.The strong "suction" action sustains the ascending motion at the upper levels of the rainstorm area.The deep wet layer in the rainstorm area is beneficial to enhance the precipitation efficiency and the formation of quasi-stationary mesoscale convective systems. References | Related Articles | Metrics

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Risk zoning of freezing disaster at motorway in Beijing-Tianjin-Hebei region WANG Chun-ling, GUO Wen-li, LI Xun, JIANG Jiang, LI Hong-yu, CHEN Chuan-lei 2018, 34 (1):  45-51.  doi: 10.3969/j.issn.1673-503X.2018.01.006 Abstract ( 224 )   PDF (2216KB) ( 345 )   Save Freezing disaster is one of the main meteorological disasters at motorway during winter in Beijing-Tianjin-Hebei region,and it is very important to make risk zoning of freezing disaster in this region.Based on the daily surface meteorological observational data at 173 weather stations from 1981 to 2015 in Beijing-Tianjin-Hebei region,the risk zoning of freezing disaster at motorway was proposed using the methods of Geographic Information System (ArcGIS) and Analytical Hierarchy Process (AHP).The results indicated that the sensitivity of freezing disaster in Beijing-Tianjin-Hebei region is high in the northwest and low in the southeast.The region of the highest freezing-disaster risk is located in Zhangbei grassland of Zhangjiakou,Hebei province,and the area of high sensitivity of freezing disaster accounts for 29.2%.The regions with a medium and high sensitivity of freezing disaster are mainly located in Beijing and the mountainous area of the northwestern part of Chengde,with an area ratio of 61.3% and 64.0%,respectively.In combination with the motorway network data,the Zhangjiakou-Shijiazhuang motorway and the northern part of Zhangjiakou-Chengde motorway in Zhangjiakou have a high risk of freezing disaster.This work can provide a reference to the prevention and mitigation of freezing disaster for the relevant management departments. References | Related Articles | Metrics

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Air quality analysis in Shanghai during the Spring Festival of 2016 ZHANG Xin, WANG Ti-jian, CHEN Pu-long 2018, 34 (1):  52-60.  doi: 10.3969/j.issn.1673-503X.2018.01.007 Abstract ( 260 )   PDF (2570KB) ( 435 )   Save The characteristics and their causes of air quality in Shanghai during the Spring Festival in 2016 were analyzed and compared with the air quality during the same period in 2014 and 2015.The results show that the air quality in most days during the Spring Festival in 2016 is good,but light pollution with the three level of air pollution occur on the New Year Eve due to the burning of fireworks and the unfavorable synoptic condition.Based on the meteorological condition,back trajectory analysis,and pollution distribution in China,it is concluded that the unfavorable atmospheric dispersion conditions on the New Year Eve in 2016 helps the accumulation of pollutants in the local area.In addition,the transport of pollutants from upstream area is also the major cause of air pollution in Shanghai.The variation of hourly PM2.5 concentration within and outside the ban region of fireworks and their absolute difference values demonstrate that the fireworks forbidden control the pollutant emissions at a certain degree.In a comparison of PM2.5 concentration during Chinese New Year period from 2014 to 2016,PM2.5 pollution in 2016 is significantly less than that in 2014 and has lower PM2.5 peak concentration and shorter pollution duration than 2015.The reduction of emission sources due to the close of works and decrease of motor vehicles on road during the Spring Festival period has a positive impact on air quality. References | Related Articles | Metrics

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Study on relationship of cloud-ground lightning density and thunderstorm days in Anhui province ZHU Hao, SUN Hao, WANG Kai, JIANG Meng-tian, DUAN Chun-feng, CHENG Xiang-yang 2018, 34 (1):  61-68.  doi: 10.3969/j.issn.1673-503X.2018.01.008 Abstract ( 284 )   PDF (952KB) ( 300 )   Save Based on thunderstorm days data from 1961 to 2015 and Active Divectory Topology Diagrammer (ADTD) lightning location data from 2010 to 2015,the relationship between annual mean cloud-ground lightning density Ng and thunderstorm days Td was analyzed using a linear model and a power law model throughout different counties in Anhui province.The results were compared with those calculated from formula according to "Code for Design Protection of Structures against Lightning" (GB 50057).The results show that there is no significant difference between thunderstorm days observed from 2010 to 2015 and that observed from 1961 to 2015.The power law model is more suitable for describing the relationship between annual cloud-ground lightning density and thunderstorm days than the linear model.The annual mean cloud-ground lightning density in different counties in Anhui province calculated from the two equations according to the standard (GB 50057) has a large difference from the real observations.The average relative error of the power-law equation Ng=0.024Td1.3 is 31.65% and that of linear model Ng=0.100Td is 44.03%,respectively.The cloud-ground lightning density calculated from the fitting equation Ng=0.0281Td1.369 is close to the real observations,and it is more suitable for Anhui province than the other two equations Ng=0.024Td1.3 and Ng=0.100Td. References | Related Articles | Metrics

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Correlations between rainy season of Hu'nan province and different rainy stages of South China LIAO Yu-fang, ZHANG Jian-ming 2018, 34 (1):  69-81.  doi: 10.3969/j.issn.1673-503X.2018.01.009 Abstract ( 354 )   PDF (6272KB) ( 346 )   Save Based on the daily precipitation data from 784 meteorological stations in China during 1961 to 2013,the pentad variation of precipitation over central-eastern China,the spatial classifications of rainfall in the different rain stages in south China and their correlations with precipitation during rainy season in Hu'nan were investigated.Results show that a rain band enhanced in spring and weakened in autumn at 25°-30°N area is maintained throughout the year,which induces different processes including the spring persistent rains (SPR),the first rainy season in South China(FRSSC),the Meiyu over the mid-lower reaches of the Yangtze River (MYYR) and the autumn rainfall in West China(ARWC).Most of Hu'nan apart from west and northwest Hu'nan indicate a high correlation between the SPR and the contemporaneous rainfall in Hu'nan (CRHN).Central and southern Hu'nan is the area where the rainfall during the FRSSC is highly related to CRHN.Central and northern Hu'nan is the area where the precipitation during the MYYR closely connects with CRHN.However,northwest and north of Hu'nan are the areas where the rainfall during the ARWC intensively relates with CRHN.The rainfall amounts in the different rain stages have very good consistencies with those over high correlation areas in Hu'nan during the corresponding periods,more specifically,the best correlation for the SPR,followed in turn by the FRSSC and the ARWC.The first four spatial modes which are able to well represent the main spatial distribution characteristics of precipitation in the different rain stages are respectively the regional consistent variation tendency,the anti-phase variation tendencies between the north and the south region,the south region of the Yangtze River and other regions,as well as the east and the west region. References | Related Articles | Metrics

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A cloud classification method based on information fusion of visible and infrared images ZHANG Chi, LIU Jun, LI Xu-guang, ZHANG Qi-hai, YANG Bi-xuan, YANG Jun 2018, 34 (1):  82-90.  doi: 10.3969/j.issn.1673-503X.2018.01.010 Abstract ( 252 )   PDF (1296KB) ( 421 )   Save Correct observation for cloud has an indicative significance for rainfall forecasting and cloud classification technology is one of the problems in the field of automatic meteorological observation.In this paper,the cloud images collected with the whole sky imager instrument and the infrared imaging system were integrated for classification and measurement of cloud.Results show that on the basis of a great deal of cloud images collected from Beijing,Hangzhou and Lijiang weather stations,considering the features of cloud images and their indications for precipitation,the cloud shapes are divided into five categories including Clear,CH,CL,CB and CM.In addition,based on the 14 eigenvalues on colors and textures selected as the parameters for calculating cloud form and 552 cloud images used as the training samples,integrating a minimum distance algorithm with eigenvalue weighted method,the observed 500 samples are distinguished and divided into the above-mentioned 5 categories according to cloud form.Taking the standard cloud form classification as reference,the average accurate rate reaches 82%.This method combining the characteristics of visible light image with rich color and the advantage of infrared image in reducing the fog and haze interference shows a higher accuracy relative to the cloud measurement method with the single visible light sensor.This research makes a meaningful attempt in the field of information fusion of visible and infrared cloud image sensors. References | Related Articles | Metrics

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Variation characteristics of thermal resources over the three northeastern provinces in China from 1961 to 2014 FENG Xi-yuan, WANG Ning, LIU Shi 2018, 34 (1):  91-98.  doi: 10.3969/j.issn.1673-503X.2018.01.011 Abstract ( 220 )   PDF (1443KB) ( 358 )   Save Based on the daily average air temperature of 83 meteorological stations over the three northeastern provinces in China during 1961 to 2014,the variation characteristics of annual mean air temperature,accumulated temperatures steadily above 0℃and 10℃ and their beginning and ending dates as well as lasting days were investigated using the statistical analysis methods such as climate tendency,cumulative anomaly curve and 9-year moving average.The results show that the thermal resources in the three provinces in recent 54 years are increasing with tendency rates of 0.29℃/10 a,60.10 (℃·d)/10 a,60.00 (℃·d)/10 a for annual mean air temperature,accumulated temperatures steadily above 0℃and 10℃,respectively.The tendency rates for the lasting days,beginning and ending dates of temperatures steadily above 0℃and 10℃ are 2.3 d/10 a and 1.9 d/10 a,-1.3 d/10 a and -0.8 d/10 a,1.0 d/10 a and 1.1 d/10 a,respectively.In addition,the increasing trends for heat resources in the three provinces are more significant in the north than in the south of the studied area.However,around 2005,the annual mean air temperature,the cumulative temperatures steadily above 0℃ and 10℃ and their lasting days are all decreasing gradually,while the beginning dates of temperatures steadily above 0℃ and 10℃ are delayed and their ending dates are ahead of time relatively.Besides,the increasing tendencies of thermal resources in the three provinces are slowing down from the south to north. References | Related Articles | Metrics

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Study on forecasting flowering phase of peach tree based on accumulated temperature model in Dandong DONG Hai-tao, TAN Li-jing, LIU Hong-lin, ZUO Xiao-qiang, YU Wen-ge, MENG Xin 2018, 34 (1):  99-105.  doi: 10.3969/j.issn.1673-503X.2018.01.012 Abstract ( 229 )   PDF (728KB) ( 421 )   Save The relationship between flowering phase and temperature was analyzed and the flowering phase of the peach tree was forecasted using the observed flowering phase in Hekou village of Dandong and daily mean temperature of the Kuandian national reference climatological station from 2005 to 2015.Three models,including active accumulated temperature model (AAT),effective accumulated temperature model (EAT) and sliding accumulated temperature model (SAT),were proposed to simulate the flowering phase based on the international accepted Spring Warming (SW) phenological model principle.The total accumulated temperature threshold before blossom and the most representative lower limit temperature of each model were determined using methods of 0.1℃ temperature interval census and mathematical deviation.Besides,the applicability of each model was tested and evaluated.The results show that SAT is the most suitable model for forecasting the peach tree flowering phase in Hekou village of Dandong with an accuracy rate of 90.91%.The accuracy of AAT and EAT are 81.82% and 63.64%,respectively.In this study,the average of maximum and minimum temperature during the period when sliding accumulated temperature passed its lower limit temperature from 2005 to 2015 was taken as an index for forecasting the peach tree flowering phase,which make the accuracy of SAT better than before.Therefore,we conclude the SAT method is a good method to forecast the flowering phase of peach tree in Dandong. References | Related Articles | Metrics

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Study on weather classification and forecasting index of marine meteorological disasters in the Bohai sea YU Zhi-ming, WANG Si-yao, MA Dong-liang 2018, 34 (1):  106-111.  doi: 10.3969/j.issn.1673-503X.2018.01.013 Abstract ( 296 )   PDF (1016KB) ( 497 )   Save In order to understand the characteristics of marine meteorological disasters in the Bohai sea,improving the ability of marine meteorological disaster monitoring and forecasting,MICAPS,satellite images,sounding data,national basic meteorological observation station data and buoy station data were used to analyze the weather cases of 78 shipwreck accidents caused by gale,fog,severe convection during 2001 to 2015 in the Bohai sea.The results show that the main gale in the Bohai sea is the north gale in winter and spring and the south gale is rare.The cold air is delivered from northern,northwestern and western paths.The surface air pressure field of southern wind can be grouped into two patterns,that is,the northeastern low pressure and the North China topographic trough.Heavy fog in the Bohai sea usually occurs in autumn and winter.The advection fog affecting the Bohai sea and its coastal regions comes from the eastern,southeastern and southwestern paths.Strong convective weather in the Bohai sea usually occurs during May to September,which is influenced mainly by Mongolia vortex (trough) and Northeast vortex (trough). References | Related Articles | Metrics