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30 August 2017, Volume 33 Issue 4 Previous Issue    Next Issue

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Research on the propagation characteristics and early warning of a multi-cell windstorm GUO Hong-ming, LI Jiang-bo, LI Yang, LI Zong-tao 2017, 33 (4):  1-10.  doi: 10.3969/j.issn.1673-503X.2017.04.001 Abstract ( 259 )   PDF (9318KB) ( 312 )   Save Lower-middle-level wind data between 0.5 and 5.0 km retrieved using the Doppler radar data 4DVAR,as well as observation data from ground-level,upper-air and regional automatic weather station (AWS) were used to comprehensively analyze the formation and development of the windstorm during a disaster-causing severe convective process occurring on June 8,2016 over Qinhuangdao.The impending early-warning on multi-cell windstorm was discussed as well.The results show that the stratification conditions with cold and dry air at upper levels and wet and warm air at lower levels favor the formation of severe convective weather.The trigger mechanisms of the process were ground-level convergence lines and dew point fronts,and the sudden changes of wind and temperature data from AWS had a good implication for determining the gust front of the storm cell.When the storm cell strengthens into a supercell and is near to the gust fronts,convergence ascending motions caused by outflow and inflow are mainly located on the edge of the regions where the echo intensities are 15-30 dBz between lower and middle levels in the supercell.Downward airflows always appear in relatively strong echo regions at lower levels,whereas the separations of the ascending and descending motions ensure the long-time development and propagation of the supercell.When the outflow gust fronts are far away from the back of the mature storm,a new convective storm is triggered to form at a distance of about 15.0-20.0 km,leading to the backward propagation of the convective system.Through the estimations on the propagation vector motion directions,one can find out the development regions of the windstorm in advance,with the early-warning time of 30 min.Persistent values of vertically integrated liquid density (VILd)above 4 g·m-3 are important indicators for the forecast of large hails with the sizes of 2-5 cm. References | Related Articles | Metrics

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Causes analysis on a large-range dense fog event in the winter of 2016 over Jiangsu province SHEN Yang, SHEN An-yun, SU Hang, XIONG Shi-wei, YAN Wen-lian 2017, 33 (4):  11-20.  doi: 10.3969/j.issn.1673-503X.2017.04.002 Abstract ( 293 )   PDF (4308KB) ( 376 )   Save Conventional ground-level meteorological observation data,NCEP (National Centers for Environmental Prediction) reanalysis and flux data were used to analyze the variations of visibility,wind,temperature,relative humidity,sounding and sensible heat flux during the whole process of a large-range dense fog during February 11-12,2016 over Jiangsu province.The results show that the precipitation on February 11 over Jiangsu area supplied sufficient vapor for the fog formation,and the temperature inversion layers,suitable surface wind speeds,and vertical wind shears favor the fog formation as well.Increase in humidity before the fog formation had a certain indication for the fog forecast,with a threshold of above 95% in winter.The temperatures at some stations had a slight increase at night in the event,which may be related to latent heat release due to vapor condensation.Ground-air temperature differences and sensible heat flux both appear negative,suggesting the ground cooling effect on the air.Clear sky radiative cooling at night was a direct cause of the event,whereas the temperature and humidity inversion layers caused by advection favored the advanced formation and maintaining of the fog.As far as most areas of Jiangsu province is concerned,this dense fog event was of radiation fog.From a forecast point of view,it is necessary to pay close attention to the establishment and maintaining of temperature inversion layer,and variations of the lower-level cloud cover at night ought to be considered as well if it rains during the daytime. References | Related Articles | Metrics

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Establishment and application of the verification and evaluation system of operational model forecast products in Northeast China YANG Yang, WANG Lian-zhong, ZHOU Xiao-shan 2017, 33 (4):  21-28.  doi: 10.3969/j.issn.1673-503X.2017.04.003 Abstract ( 208 )   PDF (1245KB) ( 272 )   Save Verification and evaluation system of operational model forecast products in Northeast China was established,and then the precipitation forecast abilities of the new 3 km version and the old 9 km version of operational models were verified and evaluated.The system runs every day automatically,and precipitation,surface temperature,weather situation field and typhoon forecast products are verified.The verification results are displayed in real time in a textual and graphic form,respectively,through the mesoscale numerical forecasting web pages of Northeast Regional Meteorological Center Local Area Network.Furthermore,the system can compare and evaluate the forecast abilities of different versions of operational models according to typical precipitation cases.The verification and evaluation results show that the new version of operational model obviously improves the forecast abilities for the grade of heavy rain or above.Although the false-alarm rates are higher,winter snowfall and southerly situation are better forecasted by the new version of the model.With the improvements in horizontal resolution and meso-micro scale topographic features,large scale precipitation forecast abilities are enhanced.However,increasing the vertical resolution of the model will create more false numerical point storm on precipitation forecast,leading to higher false-alarm rates. References | Related Articles | Metrics

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Analysis of air transport channels during pollution process in He'nan province based on trajectory clustering YANG Hao, BAI Yong-qing, LIU Lin, XU Guan-yu, WANG Ling-ling, KONG Hai-jiang 2017, 33 (4):  29-39.  doi: 10.3969/j.issn.1673-503X.2017.04.004 Abstract ( 217 )   PDF (8379KB) ( 562 )   Save Besides local sources of pollution,the outside pollutants transport is one of the most important factors significantly affecting air pollution.Lagrangian mixed with single particle trajectory model (HYSPLIT) was used to investigate the characteristics of air transport channels during severe pollution events in He'nan province.Meteorological background fields were also analyzed using the surface wind field and NCEP reanalysis data.The results indicate that the northwest airflow is prevalent in winter over He'nan province during 1986 and 2015.The air masses mainly come from Eurasia,passing Hebei,Shaanxi and Shanxi provinces,finally reaching He'nan province.Statistics of the 17 severe pollution events in 2015 shows that the air transport channels are mainly from the south (32%),the north (24%) and the east (27%) direction,respectively,which are generally below 900 hPa.After severe pollution event,the northwest wind becomes stronger whereas the south wind disappears,then the pollutants spread promptly.The simulation on severe pollution events occurring during December 5-13,2015 suggests although it doesn't account for the highest proportion,the northern channel brings most pollutants while passing the higher-pollutant areas.The weaker wind against diffusion in this channel contributes to pollution as well.Meteorological observations further confirm that static stability situations control He'nan province while severe pollution occurs.Much vapor is brought by the southeast wind,and high relative humidity doesn't favor diffusion. References | Related Articles | Metrics

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Variations of atmospheric mixed layer thicknesses and their relationships with air pollution in Ningbo CHEN Lei, YU Ke-ai, LIN Hong-wei, SUN Jun-bo, JIANG Fei-yan, SUN Shi-qiang 2017, 33 (4):  40-47.  doi: 10.3969/j.issn.1673-503X.2017.04.005 Abstract ( 241 )   PDF (1155KB) ( 346 )   Save Based on the 6-hourly conventional meteorological observation data and the daily air pollutant concentration data from Ningbo Environment Protection Bureau,the least square method was used to calculate atmospheric mixed layer thicknesses and analyze their temporal variations,along with their relationships with air pollution during 2001 to 2014.The results show that the annual average atmospheric mixed layer thicknesses vary obviously,and the maximum and minimum appear in 2004 and 2007,with the values of 866.1 m and 746.1 m,respectively.Horizontal wind speeds are key factors to atmospheric mixed layer thicknesses over Ningbo.The thicknesses are relatively larger during July and August,whereas smaller during autumn and winter,the minimum appearing in June.As for the diurnal variations,the maximum appears in the noon,whereas the minimum appears at night.The highest frequency of atmospheric mixed layer thicknesses occurs at the levels between 500 m and 1200 m.The pollutants are diluted with increasing the thickness of the mixed layer.In summer,the atmospheric mixed layer thicknesses significantly modulate the concentrations of PM10,SO2,and NO2.But in winter,due to the pollutant transport,the maximum concentrations of PM10 and SO2 are much higher,while the dilution effect of atmospheric mixed layer thicknesses is much weaker than in summer.There is little influence on NO2 concentrations.In addition,when atmospheric mixed layer thicknesses reach to the levels of 500-1200 m,the range of concentration for the same pollutant is relatively larger for the same mixed layer thickness. References | Related Articles | Metrics

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Characteristics and impact factors of acid rain in Changchun LI Qian, YANG Xu, MA Liang-chen, ZHANG Jun-ru, SUN Ke-min, XING Li-yuan 2017, 33 (4):  48-55.  doi: 10.3969/j.issn.1673-503X.2017.04.006 Abstract ( 227 )   PDF (1238KB) ( 427 )   Save Based on acid rain and related contemporaneous meteorological sounding and air pollution data observed in Changchun during 2012-2015,the annual and seasonal characteristics of acid rain and their responses to meteorological conditions and pollutant concentrations were investigated.The results show that Changchun city has experienced a transformation from weak to moderate acid rain area during the studied period.The precipitation pH indicates a fluctuant downward trend and is smaller in autumn and winter than that in spring and summer,while K value shows an opposite trend.More specifically,the acid rain is more likely to occur in precipitation for the small magnitude in Changchun city.In addition,the severe acid rain is closely associated with south or west wind and the pH value in precipitation decreases with the increasing temperature difference and thickness of thermal inversion.Besides,a negative correlation between the pH value of rainfall and the SO2 and NO2 concentrations of the previous day is very significant,which suggests the pollution of acid rain in Changchun city is to a large extent attributed to SO2 and NO2 concentrations. References | Related Articles | Metrics

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Analysis of climatic characteristics of short-time strong precipitation in Liaoning province LI Yan, SAI Han, LIU Jing, LIU Shuo 2017, 33 (4):  56-63.  doi: 10.3969/j.issn.1673-503X.2017.04.007 Abstract ( 334 )   PDF (2801KB) ( 381 )   Save Using hourly precipitation data originated from digital information processing of recording paper data from 53 national weather stations during 1971-2003 and rainfall observation data from automatic weather stations during 2004-2014 in Liaoning province,the spatial-temporal characteristics of April -October short-time strong precipitation (STSP) in Liaoning province were investigated.The results show that the spatial distribution of the STSP frequencies during the period from 1971 to 2014 is consistent with the spatial distribution of the total annual precipitation,both are larger in the east and lower in the west of Liaoning province and have a close corresponding relation with the terrain of Liaoning province and the wind direction of the southwest low-level jet.More specifically,the annual frequencies of STSP which have well correspondence with a waterlogging-drought change in Liaoning province dramatically vary between 1.5 and 3.5 during 1971-2014.The STSP concentrates in July and August in Liaoning province and is dominantly distributed in Dandong.Furthermore,the frequency of ten-day STSP firstly increases and then decreases during June to August and its peak value appears in last July.At the same time,the change trend of STSP frequency varies among different areas.Moreover,the diurnal variation of STSP frequency has the feature of territoriality,under the influence of the terrain and the diurnal change of the low-level jet and is not obvious in the north and the westernmost of Liaoning province.The STSP tends to occur over the period from the middle of the night to the morning in the south of Liaoning province while it occurs more frequently in the afternoon in the rest of Liaoning province. References | Related Articles | Metrics

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Characteristics of climate change in Fuxin during 1961-2015 SUN Bao-li, SUN Feng-hua, SUN Ke, CAO Ming-shu, YANG Xiao-tong, ZHANG Jian-guo 2017, 33 (4):  64-70.  doi: 10.3969/j.issn.1673-503X.2017.04.008 Abstract ( 340 )   PDF (864KB) ( 505 )   Save The long-term trend changes of meteorological factors including mean air temperature,maximum and minimum air temperature,precipitation,sunshine duration and wind speed and their significances in Fuxin during 1961-2015 were analyzed using moving average and trend analysis methods.At the same time,abrupt climate change features of above-mentioned meteorological factors were investigated with Mann-Kendall method.Results show that annual mean air temperature (AMAT),annual mean maximum (AMAXAT) and minimum air temperature (AMINAT) have all increased in recent 55 years in Fuxin.The increasing trend of AMINAT is the most significant while the increasing magnitude of AMXAT is smallest among all climate factors related to air temperature.However,it comes into an obvious warming period when AMAT and AMINAT rise significantly after experiencing abrupt climate change in 1991 and 1975 respectively.Specifically,air temperature ascends most significantly in winter and most slowly in summer.Furthermore,it is the 10 years i.e.from 2001 to 2010 that is the period with the highest air temperature while air temperature in winter is the lowest during 1960s-1970s among the 55 years.As far as precipitation is concerned,it has experienced a decreasing trend in recent 55 years and enters a rainless period after an obvious abrupt change occurring in 1996.At the same time,it significantly decreases in summer and autumn and slightly increases in spring and winter.In addition,sunshine duration shows a declining trend during the past 55 years and enters a period of less sunshine after an abrupt variation of sunshine duration in 1976.Besides,wind speed indicates a descending trend in the studied area during the 55 years and reduces obviously after an abrupt climate change occurring in 1978.In conclusion,this research will provide a reference for applying climate resource scientifically and effectively and adjusting agricultural planting structure reasonably as well as promoting agricultural development and environmental improvement in Fuxin. References | Related Articles | Metrics

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Change characteristics of ground-air temperature difference and their causes in Liaoning province ZHU Ling, GONG Qiang, WANG Xiao-tao, LI Qian, XU Hong, CHAO Hua, GU Zheng-qiang, SHEN Li-du, LIN Na 2017, 33 (4):  71-77.  doi: 10.3969/j.issn.1673-503X.2017.04.009 Abstract ( 312 )   PDF (5116KB) ( 448 )   Save Based on monthly average air temperature and ground temperature data from 54 meteorological stations during 1965-2014,and air temperature and ground temperature data observed manually and automatically from 45 meteorological stations in 2003 in Liaoning province,the variation characteristics of air temperature,ground temperature and the differences between ground and air temperatures (GATD) in Liaoning province over the past 50 years and their causes were analyzed.Results show that the air and ground temperatures are linearly correlated each other and both demonstrate an increasing trend,while GATD varies little during 1965-2003.Since 2004,air temperature has slightly changed and ground temperature has continued to rise as well as GATD has increased relative to the last 10 years.However,the above-mentioned conditions most significantly occur in winter in the northeast area of Liaoning province.Manual observation has been entirely replaced by automatic one in meteorological stations of Liaoning province since 2004.Under snowfall weather,the ground temperature is respectively represented by the snow surface temperature for manual observation and with the temperature below the snow for automatic observation.The difference of the ground temperature caused by different observation ways plays a dominant role for ground temperature continuously increasing during 2004-2014.Therefore,the northeast of Liaoning province with the longest duration of the snow cover becomes the region where GATD increases most significantly.Thus this suggests that the increases in ground temperature and GATD during 2004-2014 attribute mainly to the change of observation ways. References | Related Articles | Metrics

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Changes in the extremely high temperature in Northwest China and its response to the stagnation of global warming QU Shu-lin, TONG Ji-long, TANG Rui, LI Jia-yun 2017, 33 (4):  78-85.  doi: 10.3969/j.issn.1673-503X.2017.04.010 Abstract ( 259 )   PDF (1894KB) ( 411 )   Save Based on the daily maximum temperature data from the National Meteorological Information Center,the characteristics of extremely high temperature in Northwest China were analyzed in order to reveal some new features in extreme temperature in recent 20 (from 1996 to 2015) and 55 years (from 1961 to 2015).The results show that except the southern parts of Xinjiang Uygur Autonomous region and Shaanxi province,the frequency of extremely high-temperature events in Northwest China generally increases from 1961 to 2015.The high number of extreme event is mainly located in the southeastern Xinjiang Uygur Autonomous region,northern Qinghai province,western GanSu province,and central Ningxia province,with a linearly increasing number of extreme event more than 3.00 per decade.Most of them pass 99.5% or more significant tests.This is consistent with the characteristics of global warming.For the last 20 years (from 1996 to 2015),the frequency of extremely high-temperature events increases in the west and south parts,and reduces in the east and north parts.This is consistent with that in the previous 20 years (1961-1980),but opposite to that in nearly 30 years (from 1981 to 2010).In the past 55 years,the average number of extremely high-temperature events in Northwest China is on the rise with 1.73 per decade,and that in the previous 20,nearly 30,and the last 20 years rises 0.06,3.90 and-0.46 per decade,respectively.The decreasing trend in the number of extremely high-temperature events in the last 20 years is consistent with the stagnation status of global warming occurring after 1998.It suggests that this decreasing trend is a kind of responses to the stagnation of global warming.Based on the typical temperature field analysis,it indicates that the abnormal variation in high temperature in Northwest China has a significant response to the change in sea surface temperature in the Indian Ocean and the Pacific Ocean.The distributions of temperature intensity both in extreme maximum temperature and in extremely high-temperature events in Northwest China are mainly related to the elevation above sea level,local topography,and the underlying surface properties. References | Related Articles | Metrics

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Response of Saliz matsudana phenology to the change in temperature in Liaoning province DING Kang-kang, LI Ji, ZHANG Hao-yu, HU Chun-li, LIN Rong, SHAN Wei-wei 2017, 33 (4):  86-92.  doi: 10.3969/j.issn.1673-503X.2017.04.011 Abstract ( 253 )   PDF (1076KB) ( 637 )   Save Using the phenological observation data and the corresponding temperature,precipitation,and accumulated temperature in Liaoning province from 1981 to 2015,the characteristics of growth stages of Salix matsudana and their response to climate change were analyzed based on the linear tendency rate and trend coefficient methods.The results show that during the stages of bud opening,leaf expansion,bud or inflorescence emergence,and defoliation,Salix matsudana are all sensitive to changes in temperature.With the increase of temperature,the leaf expansion stage of Salix matsudana shows an ahead of time trend;the bud or inflorescence emergence and defoliation stages show a lag behind trend with a climatic trend rate of 0.8,2.3 and 3.8 days per decade,respectively;and the whole growing stage extends 7.0 days from 1981 to 2015. References | Related Articles | Metrics

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Experimental research on the snowfall enhancement through orographic clouds at Xiling Snow Mountain QI Hong-yan, SHEN Hui, WEI Wei, LIU Zhi 2017, 33 (4):  93-101.  doi: 10.3969/j.issn.1673-503X.2017.04.012 Abstract ( 197 )   PDF (3143KB) ( 252 )   Save Based on the ground-based Agl generator theory,a snowfall enhancement experiment was remotely controlled and catalyzed at the site scientifically selected at Xiling Snow Mountain in order to exploit the orographic cloud water resource in the air.During the typical precipitation processes,the snow crystal spectrum and meteorological data collected before and after the snowfall enhancement experiment were analyzed using the PARSIVEL Laser raindrop spectrometer and the intensive observations from the automatic weather stations.The results show that the surface wind has a great influence on the cloud-formation efficiency from silver iodide nuclei and on the operational target area when the snowfall enhancement is operated.The maximum amount of snowfall increases by 22%.The operational site is determined by the change status of zero velocity lines and by the center distribution of positive and negative velocities in the Doppler weather radar field.The optimal operating time is judged by the vertical airflow distribution of wind profile radar at the boundary layer.The concentration of snow crystal is significantly larger after the operation,and its changing trend is consistent with that of the amount of snowfall.The concentration increasing extent of snow crystal at different diameters is different,among which that with the diameter less than 1.5 mm is the fastest. References | Related Articles | Metrics

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Climatic characteristics of rainy days with different ranks in Handan region DU Liang-liang, ZHU Wei-hao, TIAN Xiu-xia, WANG Shi-gong 2017, 33 (4):  102-107.  doi: 10.3969/j.issn.1673-503X.2017.04.013 Abstract ( 385 )   PDF (1207KB) ( 332 )   Save The high frequency of extreme precipitation events resulted from global warming strongly influences the crop growth and the development of economy and society.Using the daily precipitation data from 16 stations in Handan region from May to September during 1974-2015,the climatic characteristics of the rainy days with different ranks were analyzed,and the relationships between the number of rainy days with different ranks and the corresponding amount of precipitation were discussed as well.The results show that there is a spatial difference in the rainy days with different ranks.In the western mountainous regions,the number of light to moderate rainy days are higher,and the number of heavy to storm rainy days are less,whereas the situations in the eastern plain are opposite.With the increase of precipitation ranks,the number of rainy days reduces rapidly.In Handan,the numbers of total,light,and storm rainy days show an obvious decreasing trend,while those of moderate and heavy rainy days show an obvious increasing trend,especially in Fengfeng mining area.Since entering into the 21st century,the number of moderate rainy days has increased significantly.The variation characteristics between the number of rainy days with different ranks and the corresponding precipitation time are consistent.The number of total rainy days is mainly due to the contributions of the light,moderate and heavy rainy days,especially due to the light ones.The total amount of precipitation chiefly comes from the storm ones.During the recent 42 years,with the increase of precipitation ranks,the correlations between the total amount of precipitation and the amount of precipitation at different ranks rapidly increase.The correlation of the amount of total precipitation with that of the storm is the highest,and with that of light precipitation is the lowest. References | Related Articles | Metrics

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A downscaling prediction model based on DERF v2.0 products in Northeast China LI Fei, WANG Yong-guang, WANG Xiao-tao, QIN Mei-ou, WU Qiong, YI Xue, LIN Rong 2017, 33 (4):  108-112.  doi: 10.3969/j.issn.1673-503X.2017.04.014 Abstract ( 238 )   PDF (1929KB) ( 285 )   Save Based on the geopotential height field products from 1983 to 2015 provided by the DERF (Dynamic Extended Range Forecast) operational system version 2.0,NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data,and monthly mean temperature data in Northeast China,a scheme for monthly-temperature prediction was established by using the downscaling interpretation and application of the DERF v2.0 products.A temperature prediction model in November in Northeast China was established based on the above methods.The results show that this model has a good forecasting performance,with a high Ps score and can be used in the climate forecasting operation.Meanwhile,the model's stability for forecasting the temperature in November is discussed,and some solutions to improve this model are provided. References | Related Articles | Metrics