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28 February 2017, Volume 33 Issue 1 Previous Issue    Next Issue

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Evolution and forecast of a radiation fog event in Shanghai ZHU Jia-rong, QI Liang-bo 2017, 33 (1):  1-11.  doi: 10.3969/j.issn.1673-503X.2017.01.001 Abstract ( 267 )   PDF (3097KB) ( 781 )   Save Based on the conventional observational data at the surface and upper levels,satellite cloud images and numerical modelling products,the evolution characteristics and causes of a radiation heavy fog event from November 29 to December 1,2015 in Shanghai and the coastal region are investigated.The heavy fog process was predicted using the WRF (Weather Research and Forecasting) model and ECMWF (European Center for Medium-range Weather Forecasting) models.The results show that the heavy fog event is mainly caused by the radiation cooling effect and is characterized by strong intensity and long duration of near-sea fog.The heavy fog event can be divided into three periods:the formation of radiation fog on land and coastal region at the nighttime on November 29,the disappearance of fog on land at day on November 30,and the advection and enhancement of fog from near sea to coastal region in the evening on November 30 till the end of this fog event in the morning on December 1.This heavy fog event forms earlier than normal radiation fog events,mainly because of the continuous descending of low cloud ceiling and radiation cooling.Poor radiation heating and increasing humidity maintain the fog over the near sea surface for a long time period.When the fog over the near sea area moves towards the coastal land at night,the fog advection and radiation cooling effects result in the heavy fog again.Both the WRF model and the high-resolution EC model were not very successful to predict this heavy fog event,probably due to the poor simulation of humidity at lower levels.Thus,synthesis analysis using cloud images and AWS (Automatic Weather Station) data at the coastal region is still an important mean for the short-time forecast of coastal fog,before the numerical weather prediction models are accurate enough to meet the operational requirements. References | Related Articles | Metrics

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The enhancement mechanism analysis of low vortex in a snowstorm over Liaoning province TIAN Li, YAN Qi, LU Jing-long, CHEN Ni-na 2017, 33 (1):  12-18.  doi: 10.3969/j.issn.1673-503X.2017.01.002 Abstract ( 247 )   PDF (2407KB) ( 649 )   Save Based on conventional meteorological observational data and NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data,the enhancement mechanism of the low vortex in a snowstorm from February 15 to 17,2015 over the northeast of Liaoning province is analyzed.The results show the enhancement of low vortex at 850 hPa is the most obvious during the snowstorm event.The absolute vorticity advection term is the major forcing source for the positive vorticity tendency in the upper levels,and the divergence term is the main forcing source for the positive vorticity variability in the lower levels.The enhancement of cold advection at 500 hPa forces the development of positive vorticity variability in the upper levels,resulting in the heterogeneous vertical distribution of vorticity,the increasing differential vorticity advection,the enhancement of vertical ascending motion,and the strong convergence in lower levels.The development of low vortex system in the lower levels results in the convergence of dry and cold northwesterly and northeasterly flows and warm and wet southeasterly flows from the north Yellow Sea over the central region of Liaoning province,which strengthens the snowfall. References | Related Articles | Metrics

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Analysis on two snowstorm events caused by reflow and inverted rough in Inner Mongolian Autonomous Region MA Su-yan, ZHANG Chao, SHI Jin-li 2017, 33 (1):  19-25.  doi: 10.3969/j.issn.1673-503X.2017.01.003 Abstract ( 305 )   PDF (2966KB) ( 512 )   Save Using the conventional meteorological data,NCEP (National Centers for Environmental Prediction) reanalysis data with resolution of 1°×1°,FY-2C satellite cloud images,and Doppler radar data in Hohhot,the circulation situations,physical quantity fields,characteristics of infrared cloud images and radar echoes during the two snowstorm events caused by reflow and inverted rough on November 5-6 and on November 21-22,2015 in Inner Mongolian Autonomous Region were analyzed.The results show that the westerly trough at 500 hPa,the jet and shear line at 700 hPa and the surface inverted rough are the main influencing systems and mesoscale clouds are the direct cause for the two snowstorm events.Warm and wet airflows transported by jets at 700 hPa and strong convergence of water vapor provide plenty of water vapor for snowstorms.The stronger and longer duration of jets at 700 hPa result in the longer duration and lager amount of snowfall.Systematic ascending motions provide the dynamic conditions for snowstorms,and the coupling of jets at the upper and lower levels favors the enhancement of ascending motion.Cold air forms a cold pad at the lower levels,temperature difference and vertical shears induce dynamical frontogenesis,and strong ascending motion is caused by the frontogenesis secondary circulation.Warm and wet airflows climb up along the cold pad,which provides the thermal conditions for snowstorms.The most severe snowfall occurs when the frontal zone is strongest and begins to weaken,and the snowstorm area occurred at the low-value center of equivalent blackbody brightness temperature (TBB≤220 K),the convergence center of water vapor at 850 hPa,and the ascending motion center.The composite reflectivity factor reaches 30-35 dBz,which means local strong snowfall.The zero velocity line in radial velocity field shows an “S” pattern,and the “bovine eye” exists for a long time,which makes snowfall continue or strengthen. References | Related Articles | Metrics

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Analysis on the structure and mechanism of a return-flow snowfall event in Tianjin HE Qun-ying, SUN Yi-xin 2017, 33 (1):  26-33.  doi: 10.3969/j.issn.1673-503X.2017.01.004 Abstract ( 408 )   PDF (3156KB) ( 505 )   Save Based on the conventional meteorological data,the NCEP (National Centers for Environmental Prediction) reanalysis data,and data from a meteorological tower,a wind profiler radar,and a microwave radiometer in Tianjin,the structure characteristics and formation mechanism of a return-flow snowfall event on February 6-7,2014 at Tianjin Binhai International airport located on the west coast of Bohai Sea was analyzed.The effects of easterly flow in the boundary layer and the formation mechanisms of ascending motion during two snowfall periods in the return-flow snow event were discussed.The results show that the return-flow snowfall process can be divided into two periods,i.e.,the first period from 15:06 to 19:00 on February 6 and the second one from 00:25 to 15:46 on February 7.The first weak snowfall period on February 6 occurred at the early time of return-flow condition.The weak easterly wind at the lower levels transported abundant water vapor from the sea to the Tianjin area,and the shallow convergence and ascending motions exist below the 2 km height in combination with the mesoscale disturbance in the easterly airflow.The second snowfall period on February 7 results from a westerly trough at the middle levels and cold air in the lower levels.The dry and cold flows move southwards along the eastern path,and the humidity in the air near the sea surface (about below 600 m) obviously increases after the flows pass the Bohai Bay.Therefore,there is a significant cold pad within the boundary layer due to the wet and cold easterly wind influencing the Tianjin area.As a trough at 500 hPa moves towards Tianjin,the warm and wet airflows climb up along the cold pad,which results in the development of ascending motions.Meanwhile,the southwesterly flows play a role in transporting water vapor. References | Related Articles | Metrics

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Comparison study of spatial interpolation methods based on hourly precipitation data from automatic weather stations XU Luan, DONG Mei-ying, CHEN Feng 2017, 33 (1):  34-43.  doi: 10.3969/j.issn.1673-503X.2017.01.005 Abstract ( 252 )   PDF (28625KB) ( 344 )   Save The gridding of precipitation data from automatic weather stations is of the urgent need to be dealt with in current meteorological service and research,and spatial interpolation is the most direct and efficient method to fulfill it.In this study,three cases were chosen to be the typical representations of wide range intense rainfall,wide range weak rainfall and local convective weather,respectively.Based on the three sets of experiments,eight common methods for interpolation are adopted to compare the interpolation results of various methods and the influence due to station densities.The first set of experiments which is based on high-density stations (the average distance between two stations is approximately 9 km) shows that the interpolation result of CR is the best,followed by IW,NN,LP,KR,TL,MQ,SP in that order.The differences among various interpolation methods are less significant than those among samples,suggesting that it is station distributions,instead of interpolation methods,that play a dominant role in the interpolation results.The second set of experiments which is based on low-density stations (the average distance between two stations is nearly 30 km) shows that the values of RMSE (root mean square error) increase significantly,so do the differences among eight methods.The values of RMSE have a slight increase after interpolation,and the results among various methods are similar in the case of local strong convection.Sensitivity experiments are carried out using the three interpolation methods such as CR,IW,and NN,indicating that RMSE will diminish with the increase of station densities,but the trend will slow down in case that the average station distance reduces to no more than 13 km. References | Related Articles | Metrics

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A precipitation probability forecast method based on the relative humidity of NWP CHU Hai, QI Liang-bo 2017, 33 (1):  44-50.  doi: 10.3969/j.issn.1673-503X.2017.01.006 Abstract ( 276 )   PDF (1750KB) ( 924 )   Save By means of combining NWP outputs and historical observation data,a precipitation probability forecast method based on relative humidity is established.Fine-grid forecasting results of relative humidity from EC model during the year 2012 and 2013 in eastern China are classified into different vertical layers and different moisture grads.The historical precipitation probability corresponding to these layers and grads are analyzed to find out a relationship between the forecast humility and precipitation probability.The relative humidity predicted by the current forecast model is then used to estimate the future precipitation probability.Different methods such as ETS score,Brier score,reliability map and case study are used to verify the forecasting effects of precipitation from July 2013 to May 2014.The results show that the method can produce fairly good distribution of future precipitation.The effects of synoptic-scale rain band appear to be better than those of convective precipitation.The false forecasting rate is effectively reduced compared with EC model results.The precipitation production can be used to specify the location and probability of the precipitation and provides a better reference value. References | Related Articles | Metrics

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Verification of CUACE model in Hefei,Anhui province YANG Guan-ying, DENG Xue-liang, WU Bi-wen, HUO Yan-feng, ZHAI Jing, YU Cai-xia, TIAN Lei 2017, 33 (1):  51-57.  doi: 10.3969/j.issn.1673-503X.2017.01.007 Abstract ( 296 )   PDF (1235KB) ( 554 )   Save In order to evaluate the prediction performance of guide products of the CUACE model in Hefei,the observed data were used to verify the guide products from March 2014 to February 2015.The results show that the forecasting AQI and PM2.5 concentrations by CUACE model are close to the observed values over Hefei,however,the forecasting concentrations of PM10 are slightly lower than the observed values while those of O3 are significantly higher than the observed values.However,the correlation coefficient between forecasting and observed concentrations of O3 is relatively high and those of AQI,PM2.5 and PM10 are just between 0.3 and 0.4.When observed air quality level is "moderate",the TS score of forecasting air quality level reaches the peak.When he primary pollutant is PM2.5,the rates of false alarm and missing report both become minimum.The prediction performance of CUACE doesn't decrease with the extension of the forecasting period.Due to its reasonably good prediction performance,the CUACE model can be used to provide some reference and help for the air quality forecast in Hefei city. References | Related Articles | Metrics

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Variation characteristics of particulate matter and its correlations with meteorological elements over Benxi LI Yang, ZHAO Hu-jia, MA Yan-jun, ZHU Yi-ming, LI Xiao-xiao 2017, 33 (1):  58-65.  doi: 10.3969/j.issn.1673-503X.2017.01.008 Abstract ( 249 )   PDF (628KB) ( 485 )   Save Data of the particulate matter mass concentrations and surface meteorological elements (i.e.wind speed,air temperature,relative humidity and atmospheric pressure) throughout 2014 in Benxi were used to evaluate the monthly and seasonally variations of particulate matters and their correlations with meteorological elements.The results show that the particulate matter concentrations are relatively high in July and October,while relatively low in May and September.Moreover,the concentration ratios of particulate matters in June and November are high.The concentrations of PM10 are lower with the average value of 115.1 μg·m-3,whereas those of PM2.5 and PM1.0 are higher,with the average values of 99.5 μg·m-3 and 86.1 μg·m-3,respectively.The correlations between particulate matter mass concentrations and wind speeds appear the most significant in spring and winter,and those between particulate matter mass concentrations and relative humidity appear the most significant in summer and winter.The mass concentrations of PM2.5 and average temperatures show significantly positive correlations in case that they are below 200 μg·m-3 with the coefficient of 0.5288,and that of the mass concentrations of PM2.5 and relative humidities are as high as 0.6981.Higher temperature and humidity,as well as lower wind speed,are the active meteorological conditions leading to pollution events with high particulate matter concentrations over Benxi. References | Related Articles | Metrics

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Analysis of the characteristics of ozone pollution and its relationship with meteorological conditions in Shenzhen LIANG Bi-ling, ZHANG Li, LAI Xin, WEI Xiao-lin 2017, 33 (1):  66-71.  doi: 10.3969/j.issn.1673-503X.2017.01.009 Abstract ( 362 )   PDF (1040KB) ( 817 )   Save Statistical analysis based on meteorological data from Shenzhen National Basic Meteorological Station and ozone data from 11 national environmental monitoring stations during 2013-2015 were carried out to investigate the pollution characteristics and meteorological conditions influencing ozone.The results show that the concentrations of ozone exceed standard in different degrees at all the environmental monitoring stations with the rate between 0.7% and 11.9%,and the average rate of 4.1% in Shenzhen.Spatial distribution of ozone pollution appears to be higher concentration in inland region and lower in the coastal region.Ozone pollution seems to be heavier in autumn and winter,whereas lighter in summer.Synthetic meteorological conditions are important factors for the pollution development of ozone,among which the relatively high temperature,sufficient sunshine,dry weather,and weak wind are most important influencing factors. References | Related Articles | Metrics

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Climate characteristics of summer high temperature and circulation analysis of an abnormal hot weather in 2014 over Zhuhai city LIU Jin-li, LI Jiao 2017, 33 (1):  72-79.  doi: 10.3969/j.issn.1673-503X.2017.01.010 Abstract ( 242 )   PDF (1665KB) ( 572 )   Save Using the conventional and automatic observation data from the national and regional meteorological stations and the NECP (National Centers for Environmental Prediction) reanalysis data from 1976 to 2014,the characteristics of summer high temperature and circulation pattern in an extreme hot weather in 2014 over Zhuhai city were analyzed.The results show that the number of summer high-temperature days has increased since the late of the 1980s in Zhuhai city,and is higher in the eastern area than that in the western area.However,this situation has changed since 21st century.More high-temperature days appear in the western area.The extreme maximum temperature increases significantly.The increasing rate of extreme maximum temperature in the western area is higher than that in the eastern area.The characteristics of summer high temperature in Zhuhai city are related to the distribution of land and sea and the stage of urbanization.The high-temperature feature is unobvious in the eastern area where it is located near the coastal and in developed urbanization and is obvious in the western area where it is located in the inland and in developing urbanization.The circulation patterns over Zhuhai city can be divided into three types,i.e.the western Pacific subtropical high/ridge control,tropical cyclone control,and the common control by the subtropical high/ridge and a tropical cyclone.Under the last type of circulation pattern,the frequency of high-temperature days is the highest.In summer of 2014,the subtropical high ridge controlling over the Zhuhai city extends westwards,its strength is stronger,and its ridge line is located southwards.This circulation pattern finally results in the abnormally high temperature in Zhuhai city. References | Related Articles | Metrics

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Characteristics and causes of an extremely high-temperature event in the summer of 2013 in Zhejiang Province ZHANG Xiao-quan, WANG Wen, FU Shuai 2017, 33 (1):  80-86.  doi: 10.3969/j.issn.1673-503X.2017.01.011 Abstract ( 403 )   PDF (2140KB) ( 667 )   Save The characteristics and causes of an extreme high-temperature event in the summer of 2013 in Zhejiang Province were analyzed using the conventional automatic weather station observations and the European Center for Medium-Range Weather Forecasts (ECMWF) Re-Analyses (ERA) Interim reanalysis data (resolution with 0.75°×0.75°).The results show that the highest temperature appears in the summer of 2013 since 1951 over Zhejiang Province.Its mean value of temperature in July and August,the number of the high-temperature days and extreme value of the maximum temperature all break the highest records since 1951.The short-time period of Meiyu and less impact of the typhoon are the backgrounds for this high-temperature weather.Among its six high-temperature stages,the fourth is the one that lasts the longest and has the strongest intensity.The main reasons for the high temperature are as follows.First,the stronger westward subtropical high and stronger eastward South Asia high in the summer together control the high and low levels over Zhejiang region.It leads to the convective activity is inhibited by the sinking airflow.Second,the center of polar vortex tends to the north of the North America.So the cold air coming from the polar vortex is weak at Zhejiang region.Meanwhile,the troughs in the middle and high latitudes are relatively shallow.It is not favorable for the cold air to move southwards.Furthermore,the subtropical high occupies over the middle and lower reaches of the Yangtze River from mid-July and then forms a banding high-pressure dam in early August.Under this situation,the convergence zone of cold and warm airs is located northwards,and the precipitation areas are also northward.Third,the westerly jet lies northward.It impedes the subtropical high moving westwards.Under the influence of the sinking airflow,it leads to the temperature increasing at this region. References | Related Articles | Metrics

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Relationship between sea surface temperature anomaly over the Indian Ocean and precipitation anomaly in Hainan Island during the pre-flood season in South China CHENG Shou-chang, HU De-qiang, YANG Yang, KE Yuan-hui, TAO Li 2017, 33 (1):  87-92.  doi: 10.3969/j.issn.1673-503X.2017.01.012 Abstract ( 260 )   PDF (1281KB) ( 483 )   Save Based on monthly precipitation data obtained from seven meteorological stations on Hainan Island in the pre-flood season (April-June) from 1969 to 2013,the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data and the HadISST (Hadley Centre sea-Ice and Sea Surface Temperature) dataset,the relationship between sea surface temperature (SST) anomaly over the Indian Ocean and precipitation in Hainan Island was investigated,and a sensitivity experiment was conducted by using the ECHAM5 model.The results show that precipitation in the pre-flood season in Hainan Island mainly occurs in May and June,and the maximum rainfall occurs in the eastern and northern regions of Hainan Island.There is a significantly negative correlation between SST over the Indian Ocean and precipitation in Hainan Island during the pre-flood season.The SST over the Indian Ocean increases anomalously,corresponding to the weak Indian monsoon and strong anomalous easterlies in the equatorial region over the Pacific Ocean.It causes anomalous anticyclones over the northwest Pacific Ocean and the northern South China Sea,which suppresses the convective development over the Hainan Island.Moreover,the anomalous easterlies in the southern edge of anticyclone hinder the transport of water vapor in the Bay of Bengal,resulting in the decreasing precipitation over Hainan Island,and vice versa.The results from numerical experiments indicate that the warmer SST over the Indian Ocean favors the maintenance and development of anticyclones at lower levels over the northwest Pacific Ocean and leads to less precipitation in Hainan Island during the pre-flood season of South China. References | Related Articles | Metrics

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Research on energy balance of the typical winter wheat farmland ecosystem in the Huanghuaihai plain:A case study in Fengqiu region LI Guo-dong, SHI Gui-fen, WU Dong-xing, ZHANG Xi 2017, 33 (1):  93-100.  doi: 10.3969/j.issn.1673-503X.2017.01.013 Abstract ( 189 )   PDF (779KB) ( 447 )   Save A winter wheat farmland ecological system located at the Feng-Qiu agricultural ecological experimental station of the Chinese academy of sciences in the Huanghuaihai (Huanghe,Huaihe,and Haihe rivers) plain was selected as the test object in this paper.Using the data observed by the eddy covariance system and the automatic meteorological stations from October 2013 to June 2014,the energy balance at each growth stage of the typical winter wheat in the Huanghuaihai plain was analyzed based on eddy correlation and correlation analysis methods.The main purpose of this study is to find the relationships between each flux and the environment meteorological factors in the farmland.The results show that the energy partitioning feature at each growth stage is different for the winter wheat.The percentage of latent heat to the net radiation at the seedling period is only 40%,while for the periods of jointing and heading,it is more than 80%,and for the other periods,it is also more than 55%.The percentage of sensible heat to the net radiation decreases with growth,reaching 50% at the sowing and seedling periods,and below 35% at tillering and the following periods,until jointing and heading periods with only 10%.During the whole growth period,the percentage of soil heat flux to the net radiation is stable,with 15% overwintering period and less than 10% at the other periods.The energy closed degree is high,with 83% at the seedling period,90% at the tillering period,and more than 90% after returning green period.There is a positive correlation between air temperature and each flux,and a negative correlation between relative humidity and each flux.The correlation coefficient between soil temperature and soil heat flux is about 0.5.There are no significant correlations between soil temperature and net radiation,latent and sensible heat fluxes.The correlation coefficients of soil water content with each flux at sowing and returning green periods are 0.5,and for the other growth stages,this kind of significant correlation is not found. References | Related Articles | Metrics

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Characteristics of meteorological disaster losses in China from 2004 to 2013 ZHAO Shan-shan, GAO Ge, HUANG Da-peng, HE Wen-ping 2017, 33 (1):  101-107.  doi: 10.3969/j.issn.1673-503X.2017.01.014 Abstract ( 267 )   PDF (1346KB) ( 1183 )   Save Using the meteorological disaster loss data from 2004 to 2013,the distribution characteristics of the comprehensive losses for various meteorological disasters in China were analyzed.A comprehensive loss index for the meteorological disasters was built based on the non-dimensional and normalized methods.The results show that except the direct economic losses,the numbers of deaths and population affected by meteorological disasters,the area of crop failures and the percentage of direct economic losses to the gross domestic product (GDP) all decrease from 2004 to 2013.Rainstorm flood and drought are the main meteorological disasters that affect China.The number of deaths and direct economic losses caused by rainstorm and flood are the highest.The area of crop and number of population affected by drought are the uppermost.The influence of rainstorm and flood is more serious in the Yangtze River Basin.For drought,it is more severe in the South-west China,Inner Mongolia Autonomous Region and Heilongjiang province.The frequency of typhoon is the highest in the southeast coastal areas of China.The local strong convective disaster mostly affects North China and Huanghe and Huaihe river areas.The Yangtze River Basin often suffers the low temperature and freezing disasters.Generally,the comprehensive losses caused by various meteorological disasters are serious in the middle-east areas,especially in Sichuan,Hunan and Hubei provinces. References | Related Articles | Metrics

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Effects of drought on the growth and yield of maize at different stages over the North China plain XU Ying, LI Man-hua, LI Hui, JIANG Peng 2017, 33 (1):  108-112.  doi: 10.3969/j.issn.1673-503X.2017.01.015 Abstract ( 222 )   PDF (503KB) ( 558 )   Save The summer maize cultivar-Zhengdan 958 was selected as a test object to study the effects of different drought levels on its growth and yield at different growth stages.The experimental control of soil water content was carried out at the stages from emergence to jointing and from emergence to tasselling.The results show that all of the soil water shortage experiments have a negative effect on the growth of maize,characterizing as shorter height,lower leaf area,and less dry matter weight.Compared with the control treatment-T5,the plant height,leaf area index,ear length,grain number per ear and 100-grain weight under T1 treatment decrease 33.5%,60.7%,18.3%,54.7% and 22.5% respectively,and these indices under T3 treatment decrease 35.8%,58.8%,24.1%,58.9% and 24.4%,respectively.So,drought is a key factor to influence the yield of maize in North China.The more severe the drought is and the longer it lasts,the more negative effects it brings on the dry matter accumulation and yield of maize. References | Related Articles | Metrics