Table of Content

30 December 2019, Volume 35 Issue 6 Previous Issue    Next Issue

ARTICLES

Select

Multi-scale comparative analysis of two hail events in Dandong in September 2018 XU Lu-lu, LI Qian, LI Hui-lin, HAN Mei, LUO Jian-yu, MENG Xin 2019, 35 (6):  1-7.  doi: 10.3969/j.issn.1673-503X.2019.06.001 Abstract ( 260 )   PDF (3137KB) ( 128 )   Save Based on conventional meteorological observations in the upper air and at the ground,observational data from a Doppler Radar,and National Centers for Environmental Prediction (NCEP) reanalysis data,we comparatively analyzed the characteristics of formation,maintenance,and development of two hail events that occurred successively in September 2018 in Dandong.The results indicated that low-level wind shear lines,strong vertical wind shears,and convergence lifting are favorable for the occurrence of hail events.The intensity of hail events is greatly influenced by the intruding way and strength,the establishment of low-level jets,and vertical wind shears.The two hail events are caused by a Northeast Cold Vortex (NCV) and an upper-level cold trough,respectively.On September 6,the turn of transverse trough leads to the fast movement of cold air masses that are supplemented from the rear of the cold vortex,and the southwest jets at 850 hPa transport plenty of water vapor,which enhanced the hail event compared with that on September 3.The radar echoes show distinct features during the two hail events.On September 3,a convective storm from multiple monomer lines gradually turns into an arched echo when it moves towards the east,with a clear headwind area on the radial velocity map.While on September 6,several super monomers are triggered along the ground convergence line and show the train effect movement.The radial velocity map appears to be blurred and shows a higher Vertical Integrated Liguid water content (VIL). References | Related Articles | Metrics

Select

Diagnostic analysis of a non-typical rainstorm event due to Meiyu fronts in 2018 MAO Cheng-yan, LI Hao-wen, GONG Li-qing, SUN Hang-yuan, WANG Jian-jiang, CHEN Hui-ling 2019, 35 (6):  8-13.  doi: 10.3969/j.issn.1673-503X.2019.06.002 Abstract ( 246 )   PDF (4571KB) ( 117 )   Save Based on conventional meteorological data and the 6-h FNL 1°×1° reanalysis data from National Centers for Environment Prediction (NCEP)/National Centers of Atmospheric Research (NCAR),we conducted the dynamic diagnosis analysis on a rainstorm event in Zhejiang province on June 20,2018,which includes the major circulation systems,isentropic potential vorticity,and vertical helicity.The results indicated that the major influencing systems for this rainstorm event are the low-level vortex shear at 850 hPa,weak cold air intruded in the middle troposphere,the South Asian Anticyclone and the Subtropical High at 200 hPa.Positive vertical helicity center at 700 hPa is a good indicator of the occurrence of rainstorm events.The evolution and form of isentropic potential vorticity are indicative of cold air activity.The convergence of airflow on both sides of the isentropic vorticity center is favorable for the development of surface low pressure.High-level isentropic potential vorticity corresponds well to the cold air activity,and precipitation areas are influenced greatly by the movement of areas with large isentropic potential vorticity values towards the south. References | Related Articles | Metrics

Select

Impact of terrain on an extreme snowstorm event in southeastern He'nan province GU Xiu-jie, SU Ai-fang, ZHANG Ning, LI Han, WANG You-he 2019, 35 (6):  14-20.  doi: 10.3969/j.issn.1673-503X.2019.06.003 Abstract ( 188 )   PDF (2577KB) ( 116 )   Save In order to fully understand the development mechanism of extreme snowstorm events in southeastern He'nan province,we analyzed the circulation background,the configuration of high-and low-level jets,and water vapor transport during an extreme snowstorm event in southeastern He'nan province from January 3 to 4,2018,using conventional sounding and ground observation data and National Centers for Environment Prediction (NCEP) 1°×1° reanalysis data.The results showed that the most fundamental synoptic-scale conditions for this event include low trough athigh levels,jets at low and middle levels,shear lines,as well as the southward motion of strong cold air.The southeastern part of He'nan province is located in a strong uplifting area due to the coupling effect of the high- and low-level jets.The southwesterly jets not only continuously provides plenty of water vapor to the snowstorm area,but also contributes to the dynamic lifting and unstable energy release,which favors the development and maintenance of the snowstorm event.The southeastern part of He'nan province is located on the northeastern side of the Dabie Mountains and Tongbai Mountains;the surrounding terrain topography is quite complicated.In order to explore the influence of topography on this extreme snowstorm event,we attempt to simulate the impact of southeastern terrain on precipitation using the Weather Research and Forecast (WRF) model. The comparison between control experiment and sensitivity experiment shows that the precipitation increases by 4-6 mm at the windward side and decreases approximate 6 mm at the leeward slope side.After terrain reduction,the U wind speed at low altitudes decreases by 2-4 m·s-1,and it's center position moves towards the southeast by 1-2 latitudes,leading to the southeastward movements of strong precipitation center.The vertical velocity along the longitude and latitude profiles show that the vertical ascending motion at the mountain windward side increases by 0.1×10-2 m·s-1;topography significantly enhances the water vapor convergence,especially at 850-700 hPa above the mountains. References | Related Articles | Metrics

Select

Prediction of summer precipitation in Heilongjiang province based on the NCEP_CFSv2 model BAN Jin, WANG Bo, LI Yong-sheng, ZHAO Jia-ying 2019, 35 (6):  21-27.  doi: 10.3969/j.issn.1673-503X.2019.06.004 Abstract ( 234 )   PDF (1385KB) ( 71 )   Save The downscaling prediction of summer precipitation in Heilongjiang province was conducted using the model outputs of the National Centers for Environment Prediction Climate Forecast System version 2 (NCEP_CFSv2) from 1982 to 2017.We first analyzed the relationship between summer precipitation and circulation factors in Heilongjiang province and the prediction of circulation factors in key zones,and then selected the circulation factors that have a good correlation between simulation and reanalysis data and between precipitation observations and reanalysis data as prediction factors.We further examined those factors using an optimal subset regression method,established a downscaling prediction model,and finally conducted the prediction performance validation and independent sample prediction using a cross-check method.The results showed that 69% of model downscaling prediction is consistent with the actual anomaly sign.The 6-year independent sample prediction is correct for 5 years,which is better than current operation forecasting results.The model downscaling technique can well predict the trend of summer precipitation in Heilongjiang province once circulation factors could be predicted accurately.In addition,the model downscaling prediction performs better in La Nina years. References | Related Articles | Metrics

Select

Characteristics of atmospheric water vapor and liquid water in Liupan Mountain area in summer and autumn TIAN Lei, SANG Jian-ren, YAO Zhan-yu, CHANG Zhuo-lin, DAN Xin-lan, CAO Ning, SUN Yan-qiao 2019, 35 (6):  28-37.  doi: 10.3969/j.issn.1673-503X.2019.06.005 Abstract ( 226 )   PDF (1556KB) ( 79 )   Save The Liupan Mountain area is a typical ecotone and ecologically fragile zone in China.It is also an important water conservation area,ecological reserve and national poverty alleviation development zone in the Loess Plateau.Characteristics of atmospheric water vapor and liquid water in the area of Liupan Mountain in summer and autumn were studied using the observations from a multi-channel microwave radiometer at the Longde weather station,the sounding data in Pingliang and surface precipitation data in Longde.The results showed that atmospheric water vapor content and liquid water content on rainy days over the Liupan Mountain in summer and autumn are about 1.4 and 7.0 times higher than those on clear days,respectively.On rainy days,water vapor increases obviously below 5 km and the decreasing rate of water vapor density with the increase of height is significantly smaller than that on clear days.Liquid water content at different altitudes also increases compared with that on clear days,and the major peak of liquid water content occurs below the altitudes where temperature is about 0℃.Atmospheric water vapor content has higher values in the period from the afternoon to the evening from June to September and has lower values near the sunrise.While for the liquid water content,the peaks occur near the sunrise,in the afternoon and evening,with the most possible one in the afternoon.A convective precipitation event is examined in this study.During this event,the atmospheric water vapor content and liquid water content increased twice within 40 minutes before precipitation,the upward transport of water vapor continuously enhances,and the relative humidity between altitudes of 2500-7500 m increases significantly. References | Related Articles | Metrics

Select

Characteristics of atmospheric water vapor and liquid water over Tianjin identified by remote sensing data from ground-based microwave radiometer CHEN Shu-cheng, SHI Jing, WANG Yan, LI Xiao-bo, CUI Ming 2019, 35 (6):  38-45.  doi: 10.3969/j.issn.1673-503X.2019.06.006 Abstract ( 183 )   PDF (1914KB) ( 119 )   Save The characteristics of atmospheric water vapor and liquid water in Tianjin were analyzed using the observation data from 35 channel microwave radiometers at Xiqing district from March 2013 to February 2017.The results show that daily variation trends of water vapor and liquid water over the Tianjin region are basically the same during the four seasons.The diurnal variation characteristics are unimodal,with the largest in summer,the second in autumn,and the smallest in winter.The probability that the maximum value of the integrated water vapor during each season appears at 23:00-00:00 (Beijing time,the same below) is significantly greater than that at other times.The probability that the maximum value of the integrated liquid water in summer and winter appears at 14:00 is the highest,and the probability that appears at 10:00 in spring and at 13:00 in autumn is the highest.The water vapor density over Tianjin decreases gradually from the ground to 3.5 km.The decreasing gradient increases successively from summer to autumn,spring and winter.The diurnal variation is not significant from 1.5 km to 3.5 km in each season.The diurnal variation curve of the average water vapor density shows a bimodal pattern below the height of 1 km in spring,summer and autumn,and its main peak value appears at around 08:00,11:00 and 12:00,respectively.In winter,there is a single peak type change.The peak area appears between 12:00 and 16:00.The density of liquid water varies with the height of stratification.In summer,the high-density region of liquid water (0.08-0.14 g·m-3) is between 5-6 km,and its maximum value occurs between 18:00 and 20:00.The high-value areas of liquid water density in autumn,spring and winter are between 1.5-3.5 km,and the value decreases successively.The maximum value of liquid water density in spring and winter is around 05:00,while that in autumn is around 02:00.In addition,the variation trend of water vapor and liquid water in Tianjin is basically the same as those of temperature and precipitation.The water vapor is positively correlated with temperature except for the time from 06:00 to 18:00 in summer and part of the time in winter.Liquid water has a poor correlation with temperature,but a positive correlation with precipitation.Throughout the whole year,liquid water has a greater correlation with precipitation at night than during the day. References | Related Articles | Metrics

Select

Study on the meteorological conditions and synoptic classifications of O3 pollution in Shanghai in 2017 YU Zhong-qi, MA Jing-hui, MAO Zhuo-cheng, CAO Yu, QU Yuan-hao, XU Jian-ming 2019, 35 (6):  46-54.  doi: 10.3969/j.issn.1673-503X.2019.06.007 Abstract ( 390 )   PDF (1202KB) ( 445 )   Save Air quality data and relevant meteorological data were used in this paper to analyze the variations of ozone and the meteorology influencing factors in Shanghai in 2017.Studies on subjective synoptic weather classifications on ozone were also conducted.The results showed that there were 275 non-pollution days accounting for 75.3% of the whole year of 2017.There were 55 O3-8h pollution days.The average O3-8h concentration was 115 μg·m-3 in 2017.The year-on-year growth was more than 10%.It has reached the highest concentration since 2013.The increase in ozone concentration in 2017 was mainly due to the increase in ozone concentration in the summer half-year.Compared with the summer half-year of 2016,the conditions of wind,temperature,water vapor,illumination,and radiation were all helpful to increase the ozone concentration in the summer half-year of 2017,which was under the background of the abnormally western and strengthened western Pacific subtropical high.The synoptic systems affecting O3 pollution are classified into four patterns,including subtropical high (SH),surface high (G),equalized pressure (J) and low pressure (D).The subtropical high pattern is the most predominant and typical ozone pollution pattern,accounting for 29.1% of the total.It shows high level pollution.The low-pressure pattern appears with the least frequency,and the surface high pattern shows the lowest level of pollution. References | Related Articles | Metrics

Select

Feature analysis of atmospheric self-purification capability and atmospheric particulate concentration in Tianjin during 2013-2017 TANG Ying-xiao, HAN Su-qin, CAI Zi-ying, YANG Xu, FENG Jin 2019, 35 (6):  55-66.  doi: 10.3969/j.issn.1673-503X.2019.06.008 Abstract ( 190 )   PDF (3567KB) ( 291 )   Save Based on the empirical formula,the spatial and temporal characteristics of atmospheric self-purification capability (APC) and concentrations of PM2.5 and PM10 were analyzed in this paper.Meanwhile,the relationship between APC and particulate concentrations were also analyzed to well understand the impact of the atmospheric environment on the pollutant concentrations.Results reveal that the highest value of the APC appears from 13:00 to 14:00 and the lowest one appears at night during a day.During the year,the APC is relatively lower during the building heating seasons from October to March than that during the non-heating seasons.Conversely,the particulate concentrations are higher during the building heating season than those during the non-heating seasons.Compared with 2013,the annual APC increased 5%,and the concentrations of PM2.5 and PM10 decreased 34% and 47%,respectively,in 2017.The APC value in the coastal area is higher than that in the inland area,and that in the urban area is lower than that in the surrounding areas.The high value of the particulate concentrations concentrates on the south-central area,especially in urban region.The spatial distributions of APC have a good relationship with that of particulate concentrations.There is a negative correlation between the daily averaged values of the APC and PM2.5 concentration.The correlation coefficient is about -0.34,and it increases during the heating season.The heavy pollution incidents mostly happen during the low APC periods. References | Related Articles | Metrics

Select

Study on the prediction method of meteorological conditions for ozone pollution in Chengde LU Qian, WANG Guo-hui, FU Jiao, ZHOU Shi-ru 2019, 35 (6):  67-76.  doi: 10.3969/j.issn.1673-503X.2019.06.009 Abstract ( 228 )   PDF (2205KB) ( 148 )   Save Based on the data from the environmental monitoring stations and weather stations in Chengde from 2014-2016,the influence of meteorological conditions on the concentration of O3-8h was analyzed.The forecasting method of meteorological conditions for O3 pollution was discussed.The results show that the concentration of O3-8h from April to July is higher than that in the other months in Chengde.The diurnal variation of O3 concentration is characterized by the high concentration in the afternoon and the low one at night.When the O3 pollution happens,it is affected together by the high-pressure ridge and the west airflow at 500 hPa,the strong warm advection and high temperatures above 20℃ at 850 hPa,and the southerly airflow between the low-pressure front and the high-pressure rear at sea level pressure field.The meteorological factors that are favorable to increase the O3 concentration are as follows:the daily mean temperature is higher than 23℃;the daily maximum temperature is higher than 28℃;daily mean sea level pressure is 995-1007 hPa;the daily average water vapor pressure is 18-28 hPa;and southerly wind is greater than 1 m·s-1.Based on the comprehensive score of meteorological factors,the O3 pollution index is established.The correlation coefficient between O3 pollution index and O3 concentration is 0.7553,which indicates that the O3 pollution index can be used to predict the ozone pollution weather. References | Related Articles | Metrics

Select

Characteristics of temperature decline between two adjacent days and its interdecadal change during winter in Northeast China LI Shang-feng, GAO Zong-ting, YANG Xu, YIN Lu-ting 2019, 35 (6):  77-84.  doi: 10.3969/j.issn.1673-503X.2019.06.010 Abstract ( 215 )   PDF (3660KB) ( 119 )   Save Using the daily mean,maximum,and minimum surface air temperatures (abbreviated as Tmean,Tmax,and Tmin) data from CN05.2 for the period from 1961 to 2012,the temperature decline events (TDEs) were determined in the present study.These TDEs were classified into three categories according to the range of temperature dropping,i.e.,the weak decrease in temperature (WDT),normal decrease in temperature (NDT),and a strong decrease in temperature (SDT).The temporal and spatial distribution characteristics of the occurrence frequency of TDEs were examined in this paper.Results show that,for Tmean and Tmin,the highest frequency of the occurrence of WDT and NDT appears in the Daxing'anling Mountain,Xiaoxing'anling Mountain and Changbai Mountain,but the highest frequency of the occurrence of SDT appears only in Changbai Mountain.In addition,the three TDE category events happen frequently in 1960s and 1970s,but less in 2000s.For Tmax,the highest frequency of occurrence of the WDT and NDT appears in a belt area among 42°-45°N,but less in north and south of this belt,showing a frequency distribution pattern of low-high-low.The highest frequency of the SDT events appears only in Changbai Mountain.The events of the WDT,NDT and SDT mostly happen in 1960s and 1970s,but very less in 2000s. References | Related Articles | Metrics

Select

Climate characteristics of high-temperature and diagnosis of a continuous high-temperature process in Huangshan area DU Qi-cheng, HUANG Jun-kai, SHEN Xu-yang, NIU Jun-yi 2019, 35 (6):  85-92.  doi: 10.3969/j.issn.1673-503X.2019.06.011 Abstract ( 215 )   PDF (1619KB) ( 119 )   Save Based on the observation data of Huangshan area and EC reanalysis data from 1981 to 2017,and using mathematical-statistical methods,the characteristics of the summer high temperature (SHT) in Huangshan area were analyzed and the reason of a high-temperature weather process with the extreme high temperature,long duration,large intensity and wide range in July 2017 was diagnosed.The results show that the subtropical high is the main influence system of SHT.The SHT has clear spatio-temporal distribution characteristics.More specifically,the most and the second most high-temperature days are in July and August,accounting for 48% and 37%,respectively.The high temperature mainly occurs in the period from mid-July to early August.The spatial distribution of the SHT features more occurrence in basins and hilly areas and less in high-altitude mountainous areas. Meanwhile,strong subtropical high,the ridgeline stabilizing in Huangshan area,the coordination of the warming sinking air near the sub-high ridge line and low-level warm center are the main causes of the continuous high temperature in Huangshan area during July 12-29 in 2017.In addition,the inactive tropical low-value system during midsummer and few landing typhoons during high temperatures provide favorable conditions for the occurrence of persistent high temperatures.Topography,such as altitude,leads to the uneven distribution of high temperature.Besides,the position of sub-high ridgeline,subtropical high intensity,relative humidity profile,rainfall,typhoons,topography,and other factors are of great indicative significance for the forecast and early warning of high temperature. References | Related Articles | Metrics

Select

Characteristics of strong typhoon wind and typical cases of extreme wind on the west coast of the Taiwan Strait,China LIN Xiao-hong, WU Xing-yu, CHEN Miao, LI Ya-fen, LIU Jin-xiu, CHEN Bin 2019, 35 (6):  93-100.  doi: 10.3969/j.issn.1673-503X.2019.06.012 Abstract ( 219 )   PDF (2640KB) ( 111 )   Save Based on the strong wind data of the coastal stations in Fujian province from 1987 to 2016,the NCEP reanalysis data and FY2C satellite TBB data,the typhoon gale and extreme gale on the west coast of the Taiwan Strait in China were defined and analyzed by using statistical and meteorological diagnostic methods.The results show that the typhoon gale on the west coast of the Taiwan Strait in China is mainly 7-9 grade and the extreme gale is 10-14 grade. The central region of the west coast is a windy disaster area.The typhoon samples in the studied period are classified into four types according to their paths.As a result,it is found that the most typhoons that produce strong wind land at the central region of Fujian to the central region of Zhejiang and the south of Fujian to the east of Guangdong,and the strong wind regions are generally located on the right of the paths.Meanwhile,two typical cases of typhoons named 0608 Sangmei and 1614 Meranti which produce extreme wind are compared and investigated.The results show that the terrain which are high in the north and low in the south and the strong pressure gradient is in favor of early producing the gale.In addition,the stimulated growth of the mesoscale convection in the lower layer with cold advection invading in the middle layer over typhoons is the cause enhancing the ground gale. References | Related Articles | Metrics

Select

Temporal and spatial variation characteristics of frozen soil in Shenyang area from 1959 to 2018 DING Kang-kang, ZHANG Hao-yu, YANG Hong-bin, WAN Zhi-qiang, LI Li-guang, SUI Ming 2019, 35 (6):  101-108.  doi: 10.3969/j.issn.1673-503X.2019.06.013 Abstract ( 644 )   PDF (1418KB) ( 185 )   Save Based on daily frozen soil observation data,daily average air and surface temperature,daily average ground temperature at the depth of 5 cm,10 cm,15 cm,20 cm and 40 cm from the seven meteorological stations in Shenyang area,the temporal and spatial variation characteristics of maximum frozen soil depth (MFSD) are analyzed and discussed.The results show that the frozen soil in Shenyang area generally appears in October and melts in April next year.The frozen soil depth is the largest in February-March and the smallest in October;and the MFSD decreases significantly at a rate of -4.8 cm/10 a.In addition,the interdecadal variation of the MFSD also shows a decreasing trend.Meanwhile,the daily MFSD has a significant negative correlation with the daily average temperature and the daily average ground temperature at the depth of 20-40 cm and their correlation coefficients are 0.60 and 0.72,respectively.Mann-Kendall test shows that the MFSD in the seven weather stations shows climatic abrupt change in 1980s.Moreover,the starting and ending dates of maximum frozen soil depth in recent 60 years are delayed and advanced with trend rates of 1 d/10 a and 3.2 d/10 a respectively,and the average duration of frozen soil is 164 d in Shenyang area and shows a shortening trend with a rate of 4.4 d/10 a. References | Related Articles | Metrics

Select

Assessment of local debris flow disaster in Tianjin based on AHP method DUAN Li-yao, XIONG Ming-ming, LI Da-ming, LIU Xun-ping, WANG Jing, LI Pei-yan 2019, 35 (6):  109-116.  doi: 10.3969/j.issn.1673-503X.2019.06.014 Abstract ( 176 )   PDF (1996KB) ( 67 )   Save By utilizing data of precipitation,topography and geomorphology,population,geological disasters and digital elevation mode (DEM),Jizhou district,located in the north of Tianjin,was taken as the research area in this paper to conduct study on assessment of the hazardous degree of debris flow disasters in Tianjin.More specifically,the research area was divided into the grids using the approach of non-structural irregular design,and then the weights of the debris flow risk factors including the direct and indirect amount of rainfall,flow velocity,topography and geomorphology,population density,frequency of occurrence of debris flow were determined,and the debris flow risk degree model (DFRDM) of Tianjin was established based on the analytic hierarchy process method(AHP).This model was used to evaluate the hazardous degree of the debris flow disasters for the eleven strong rainstorm processes over Jizhou district during 2011-2018.The results show that the rainfall process on July 20,2016 with the largest rainfall amount and concentration has the highest risk of debris flow,and the risk for stable rainfall process on August 12-14,2018 is the lowest.Furthermore,the debris flow occurring over "Shuang'an" Village on July 22,2012 and the small landslides on July 24,2018 over Jizhou district,are both captured by the DFRDM model,indicating that this model has a good assessment ability for debris flow and can be applied to real-time operation and service.Moreover,the generalized extreme value distribution function was used to calculate the 1-hour and 12-hour amount of precipitation in different reoccurrence periods of Jizhou district,and the DFRDM was then used to estimate the debris flow risks for different levels of precipitation,which can provide useful reference for the relevant decision-making departments. References | Related Articles | Metrics

SCIENTIFIC NOTES

Select

Classification of satellite imagery features in regional hail weather in Guangxi ZHAI Li-ping, HUANG Ming-ce, LAI Zhen-quan, ZHOU Yun-xia, LI Jia-ying 2019, 35 (6):  117-125.  doi: 10.3969/j.issn.1673-503X.2019.06.015 Abstract ( 166 )   PDF (3465KB) ( 147 )   Save On the basis of FY satellite data during 2007-2017 and conventional radiosonde and surface observations,in the light of the 23 regional hail weather processes in Guangxi,three kinds of conceptual models for regional hail against satellite imagery including the low trough type of north China,the low trough type in eastern plateau and the south branch trough type were established based on the main influence weather system and characteristics of cloud pattern inversed with satellite data.The results show that satellite imagery models play a key role in indicating the position and type of upper trough cloud,and the hail cloud cluster mostly originates from the bottom of upper trough.In addition,the subtropical jet cloud system along the South China coast also plays an important role in the occurrence and development of hail clouds which usually occur in the clear sky area on the north side of the subtropical jets.The regional hail cloud cluster in Guangxi shows up as a long oval shape with a smooth "V" shape boundary in the upper wind direction and a long anvil sticking out along the downwind. References | Related Articles | Metrics

Select

Sensitivity analysis on the parameters of model AERSCREEN YANG Hong-bin, ZHANG Yun-hai, LI Ke-fei, CHEN Gang, ZOU Xu-dong, WANG Hong-yu, LIU Yu-che 2019, 35 (6):  126-131.  doi: 10.3969/j.issn.1673-503X.2019.06.016 Abstract ( 160 )   PDF (482KB) ( 51 )   Save The AERSCREEN estimation model recommended in the "Guidelines for Environmental Impact Assessment of Atmospheric Environment" (HJ2.2-2018) had improved concerning the processing of meteorological and topographic data,as well as the downwash of buildings.The sensitivity test of maximum landing concentration under different emission parameters and meteorological conditions was carried out using the estimation model AERSCREEN,especially for the point sources at a height of 30 m.The results show that the maximum surface concentration decreases gradually with the increasing velocity of the flue gas outlet.The maximum surface concentration does not change obviously with the variation of the Bowen ratio.With the increased roughness of ground and temperature of flue gas outlet,the maximum ground concentration decreases gradually.When the temperature of flue gas is about 75℃ and the roughness is 1.3 m,the surface concentration reaches the minimum.With increased albedo and chimney height,the maximum ground concentration decreases gradually.Under different chimney heights,the maximum ground concentration increases with the maximum ambient temperature.Under different ambient temperatures,the maximum ground concentration decreases with the increasing chimney height,which indicates that the increase of the maximum ambient temperature will reduce the maximum ground concentration.In this model,the maximum ground concentration does not change with the increase of the lowest ambient temperature.With the increased minimum wind speed,the maximum surface concentration obtained from the simulation will gradually decrease. References | Related Articles | Metrics

BULLETINS

Select

Distribution characteristics and comparative analysis of lightning parameters between lakes and lands WANG Xue-liang, YU Tian-ye, HE Shan 2019, 35 (6):  132-138.  doi: 10.3969/j.issn.1673-503X.2019.06.017 Abstract ( 170 )   PDF (910KB) ( 68 )   Save The distribution characteristics of cloud-to-ground (CG) lightning frequency,polarity,lightning density,lightning current amplitude,and gradient of wavefront of lakes and lands were compared using mathematical statistics method based on the data monitored by Lightning Location System (LLS) in Hubei province from January 1,2007 to December 31,2016.The results show that the temporal variation trends of lightning parameters for lakes and lands are similar.Lightning frequency decreased insignificantly in the last 10 years,and the percentage of positive CG lightning showed an increasing tendency.There are more lightning frequencies on lands than that over the lakes,and lightning frequency of lakes and lands are significantly different in spring and summer,in which lightning frequency of lands in summer is 21.1% higher than that of lakes.The diurnal variation of lightning frequency for lakes and lands appears to be unimodal,and lightning frequency of lands is 39.7%,which is higher than that of lakes from 13 p.m.to 18 p.m.The average CG lightning density of lakes is smaller than that of lands,and the average CG lightning densities of lakes and lands are 2.96/(km2·a) and 3.47/(km2·a),respectively.The average lightning current amplitude of lakes is larger than that of lands.The average wavefront steepnesses of lightning current for lakes and lands have little differences,and the difference between them is generally less than 1 kA/μs. References | Related Articles | Metrics

Select

Risk assessment of maize drought in Heilongjiang province based on natural disaster risk theory WU Shuang, JIANG Li-xia, LI Yu-guang, GONG Li-juan, TIAN Bao-xing, WU Ying 2019, 35 (6):  139-144.  doi: 10.3969/j.issn.1673-503X.2019.06.018 Abstract ( 136 )   PDF (1050KB) ( 66 )   Save In order to investigate the drought risk of maize for different areas of Heilongjiang province in China and provide a scientific foundation for maize disaster prevention and disaster management,drought risk index of maize was studied based on the meteorological data and maize growth data during 1971 to 2017 from 44 agricultural meteorological stations.The growth period of maize was divided into two parts based on the growth situation,named early stage (emergence to tasseling) and late-stage (tasseling to maturity),respectively.The natural disaster risk assessment method was applied to analyze the data and crop water deficit index was selected to evaluate the severity of drought.The indices of drought risk assessment model included dangerous,vulnerability,exposure,and emergency response and recovery.The weight coefficients of the 4 indices were induced to define the degree of influence of different indices.The drought risk zone of maize was analyzed based on the drought risk index in Heilongjiang province.The results show that the high values of risk index are distributed in the western of Heilongjiang province and the relatively high values of risk index are distributed in Shuangcheng District of Harbin and Zhaodong County.The southwest of Heilongjiang,including Zhaozhou,Zhaoyuan,Anda is middle risk areas.The low values of risk index are distributed in the Sanjiang plain of eastern Heilongjiang and Heihe,Yichun,Mudanjiang.This study could provide a scientific foundation for maize disaster prevention and disaster management. References | Related Articles | Metrics