Table of Content

30 August 2021, Volume 37 Issue 4 Previous Issue    Next Issue

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Observations and analysis of vertical structure of cloud and precipitation caused by a cold vortex in Northeast China Jin-guang ZHANG, Shu-hui ZHAO, Yang LIU, Li SUN, Nan SHAN, Tie-ning ZHANG, Meng-jia ZHANG 2021, 37 (4):  1-8.  doi: 10.3969/j.issn.1673-503X.2021.04.001 Abstract ( 263 )   HTML ( 26 )   PDF (2155KB) ( 187 )   Save Based on the data observed from a millimeter wavelength cloud radar (8 mm) and a micro rain radar (12.5 mm) at Fuxin national weather station (121.7458°E, 42.0672°N) in Liaoning province during a precipitation event caused by a cold vortex in Northeast China on August 12-13, 2020, we analyzed the characteristics of vertical structures of cloud and precipitation and discussed the precipitation mechanism. The results indicated that clouds develop unevenly in the horizontal direction during the precipitation, dominated by stratiform clouds and stratocumulus mixed clouds, and sometimes convective bubbles are embedded in the clouds. The cloud precipitation has changed significantly in stages, with stratiform cloud precipitation, stratocumulus mixed cloud precipitation, and convective cloud precipitation successively occurring. Both stratiform cloud precipitation and stratocumulus mixed cloud precipitation exhibit obvious bright bands, and the radar echo intensity, echo top height, and precipitation intensity of the stratiform mixed cloud precipitation are greater than that of the stratiform cloud precipitation. The radar echo of convective cloud precipitation attenuates obviously due to the heavy precipitation, thus the echo top height cannot indicate the actual cloud top situation. During the precipitation stage of stratiform clouds, the cloud radar reflectivity increases slowly as the altitude decreases, and the reflectivity decreases due to the combined effects of evaporation and collision of raindrops during their falling process. Compared with the precipitation in the stratiform cloud, the colliding effect of stratocumulus mixed cloud precipitation is stronger, and the evaporation under the cloud becomes weak due to the near-surface humidification effect of the previous precipitation. During the stage of convective cloud precipitation, the increase in reflectivity mainly occurs in the ice-water mixed layer, which favors generating large droplets, broadens the cloud drop spectrum, and improves the efficiency of collision. Figures and Tables | References | Related Articles | Metrics

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Characteristics and causes of a high precipitation supercell in Beijing in May of 2019 Yan-jie LIU,Qing-chuan WANG,Min XU,He-ling ZHOU 2021, 37 (4):  9-17.  doi: 10.3969/j.issn.1673-503X.2021.04.002 Abstract ( 271 )   HTML ( 15 )   PDF (9974KB) ( 101 )   Save On the evening of May 17, 2019, local extremely heavy precipitation, thunderstorms gales, and hail occurred in Tongzhou District of Beijing. A detailed analysis of this weather process was conducted using various observation data from surface intensive automatic stations, radars, microwave radiometers, and European Center Mesoscale Weather Forecast reanalysis data (ERA-interim) with a temporal resolution of 6 h. The results indicated that a high precipitation supercell is a direct system that caused the severe convective weather, and this typical characteristic can be identified from the radar echo. In the afternoon, a small thermal and low-pressure system occurs near the surface and at the ultra-low altitudes in the southern part of Beijing, which makes the southeasterly wind significantly strengthened. On the one hand, it provides abundant water vapor and forms an unstable stratification of upper dry and lower wet. Meanwhile, the interaction between the low-level southwesterly flow and the upper-level westerly jet enhances vertical wind shear and produces vertical circulation. The low-level temperature inversion layer exists for a long period, and the energy continues to accumulate, making it possible to increase the explosiveness of thunderstorms in the afternoon. The outflow of the surface cold pool flow confronts the southerly wind, forming a dense zone of surface pseudo-equivalent potential temperature. The cold pool was maintained steadily for a long time, and a moist-warm convergence line of the boundary layer occurred ahead of the cold pool. The frontogenesis causes the warm and humid airflow to be continuously uplifted, and the convective system is strengthened and in a quasi-static state. In a favorable environment, combined with sufficient water vapor supply and strong boundary layer convergence and uplift, thunderstorms strongly develop into a high precipitation supercell. Then the storm splits, and the storm on the right develops into a supercell, passing through eastern Tongzhou again and forming the rainstorm center. Figures and Tables | References | Related Articles | Metrics

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Characteristics of atmospheric boundary layer and sources of a sand-dust event during spring 2018 in Beijing Hai-lin GUI, He QIN, Pei-tao ZHAO, Fei WANG, Zhi-jun TANG, Ji-kang WANG, Yuan-yuan ZHU, Yang-xi CHU 2021, 37 (4):  18-25.  doi: 10.3969/j.issn.1673-503X.2021.04.003 Abstract ( 214 )   HTML ( 10 )   PDF (2544KB) ( 97 )   Save From March 27 to 28, 2018, a large-scales and-dust event occurred in central and eastern Inner Mongolia, Northeast China, and North China. In the early morning of March 28, massive dust particles arrived in Beijing, causing severe air pollution in the city. In this study, we analyzed the characteristics of the atmospheric boundary layer, the source of sand and dust, and the features of air pollution during this sandstorm event, using surface routine observation data of China Meteorological Administration, retrieved data from aerosol lidar and wind profiler radar, and atmospheric composition data from the Ministry of Ecology and Environment of the People's Republic of China. The results indicated that the depolarization ratio of dust aerosols during this dusty weather in Beijing is about 0.25-0.40. The depolarization radio data show that sand particles entered Beijing from a high altitude, about 6 h earlier than entering from the ground. These sand particles affecting Beijing mainly come from the north, and sand particles from the east have a certain supplement. During this event, the concentrations of Ca, Fe, Na, K, Mn, and other elements in Beijing increase significantly, which are equivalent to the abundance of the substance in the crust. The concentrations of pollutant elements such as Cu, Zn, Pb, Cd and As decrease, and they are much higher than the abundance of the substance in the earth's crust. Figures and Tables | References | Related Articles | Metrics

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Research on application of multi-source precipitation forecast integration technology Xian TANG,Rong-wei ZHOU,Xiao-feng HE,Jing-yu WANG,Xiao-chen REN 2021, 37 (4):  26-32.  doi: 10.3969/j.issn.1673-503X.2021.04.004 Abstract ( 170 )   HTML ( 2 )   PDF (2215KB) ( 69 )   Save The integrated forecasting of 3-d precipitation was conducted based on precipitation forecast results of the global high-resolution European Centre for Medium-Range Weather Forecasts (ECMWF) model, the Chinese new generation of operational Globe/Range Assimilation and Prediction Enhance System (GRAPES_Meso), and the Weather Research Forecast (WRF) model. Taking the three-source (ground-satellite-radar) hourly precipitation grid product in China (CMPA-Hourly V2.0) as the "observed value", we adopted a simple bias-removed ensemble mean (ENSM) method and a multi-model ensemble (MME) method to conduct integrated precipitation forecast in the mainland of China. The performance of integrated precipitation forecasts was evaluated using precipitation observation data from 2800 national automatic weather stations. The results indicated that the MME method can integrate the advantages of each model member's precipitation forecast field, and provide a more stable, reliable, and high-quality refined precipitation forecast product with a higher resolution. During the test period, the EST score of the precipitation forecast based on the MME method during the flood season in the mainland China is better than that using the ENSM method and using the optimal single-mode precipitation forecast. The BIAS score is closer to 1, and the anomaly correlation coefficients between the forecasts using the MME method and the observed values increases. The MME method has a better ability to capture large values of precipitation, especially for improving the prediction of grades above moderate precipitation. Figures and Tables | References | Related Articles | Metrics

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Numerical simulation on the spatiotemporal distribution of PM2.5 in the Yangtze River Delta Min XU 2021, 37 (4):  33-39.  doi: 10.3969/j.issn.1673-503X.2021.04.005 Abstract ( 133 )   HTML ( 7 )   PDF (2408KB) ( 82 )   Save The spatiotemporal characteristics of fine particulate matter (PM2.5) concentration over the Yangtze River Delta in 2018 were simulated using the third-generation air quality forecast model, Long Term Ozone Simulation-European Operational Smog (LOTOS-EUROS). Comparing with ground observations, the rationality of this model to simulate the long-term characteristics of PM2.5concentration was verified, and the spatiotemporal variation of PM2.5 in this region was explored. The results showed that the LOTOS-EUROS model can well reproduce the spatiotemporal characteristics of PM2.5 concentration in the Yangtze River Delta. The overall correlation coefficient between the observation and simulation values of the monitoring stations reaches 0.64, which means that this model can be applied to the simulation of fine particulate matter in the Yangtze River Delta. The PM2.5 concentration in the Yangtze River Delta is high in winter of the northwest, and is low in summer of the southeast. High PM2.5 concentrations in winter occur in the northwestern region of the Yangtze River Delta, and the maximum concentrationin in Anhui province and other areas can reach 160 μg·m-3. In spring and autumn, high PM2.5 concentrations are concentrated in the north of 30°N and the west of 120°E, with values ranging from 40 μg·m-3 to 80 μg·m-3. Whereas in summer, PM2.5 concentration decreases significantly and remains around 20-40 μg·m-3 in most areas. The low-value center of PM2.5 concentration (lower than 10 μg·m-3) occurs in coastal cities in the southeast of the Yangtze River Delta, with the lowest value reaching 5 μg·m-3. Figures and Tables | References | Related Articles | Metrics

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Analysis of air pollution characteristics and influencing factors in the winter of 2018 in Northwest Shandong province Yu-tian DAI, Xue-bin YANG 2021, 37 (4):  40-47.  doi: 10.3969/j.issn.1673-503X.2021.04.006 Abstract ( 181 )   HTML ( 13 )   PDF (2035KB) ( 294 )   Save Using the daily mass concentrations of PM2.5, PM10, NO2, SO2, CO, and O3 and the corresponding meteorological data from December of 2018 to February of 2019, the characteristics and influencing factors of air pollution in Northwest Shandong province were analyzed. The results show that in the winter of 2018, air pollution is relatively serious in Northwest Shandong province. In Liaocheng, Dezhou, and Binzhou, the number of days with mild or above pollution is 61%, 60%, and 54%, respectively, and the number of days with severe or above pollution is 24%, 11%, and 9%, respectively. The main pollutants include PM2.5, PM10, and NO2, among which PM2.5 accounts for more than 60%. The diurnal variation of PM2.5, PM10, SO2, NO2, and CO shows a double-peak and double-trough pattern. The diurnal variation of PM2.5, PM10, SO2, NO2, and CO shows a double-peak and double-trough pattern. The diurnal variation of PM2.5, PM10, SO2, NO2, and CO appears at 04:00-07:00 and 15:00-17:00, respectively, and the peak value is lower in the afternoon than in the morning. O3 presents a unimodal distribution, with a minimum value at 09:00 and a maximum value at 18:00-19:00. PM2.5 is the main primary pollutant in the northwest of Shandong province. It is significantly positively correlated with PM10, CO, and NO2, and reaches the significance test of 0.01 level. The correlation between PM2.5 and NO2 at low relative humidity (< 60%) is higher than that at high relative humidity (≥ 60%), and its correlation with CO at high relative humidity is higher than that at low relative humidity. The average relative humidity and temperature in the polluted period (PM2.5>75 μg·m-3) are significantly higher than those in the clean period (PM2.5 ≤ 75 μg·m-3), and the wind speed and air pressure in the clean period are significantly higher than those in the polluted period. Figures and Tables | References | Related Articles | Metrics

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Characteristics of O3 concentration and its relationships with meteorological factors in the southern foot of Taihang Mountains from 2015 to 2019 Qiang-jun LIU, Jun-fang SONG, Cheng-yu NIU, Jun ZHAO, Yu-jun ZHANG 2021, 37 (4):  48-53.  doi: 10.3969/j.issn.1673-503X.2021.04.007 Abstract ( 136 )   HTML ( 5 )   PDF (1164KB) ( 97 )   Save Based on the data of O3 concentration at the southern foot of Taihang Mountains (i. e. Jincheng city, Shanxi province) and the total solar radiation from 2015 to 2019, the temporal and spatial variation characteristics of O3 concentration and its relationships with meteorological factors such as wind, relative humidity, precipitation, haze, temperature, and solar radiation were analyzed. The conclusions are as follows: the O3 concentration increases year by year. Its concentration in summer is significantly higher than that in winter. The monthly variation of O3 concentration is unimodal. The results show that the peak value appears in June and the valley value appears in January, and the diurnal variation is higher in the daytime than that in the night. The spatial distribution of O3 concentration has obvious regional differences, showing the characteristics of high in the middle and south, low in the East and West and North, i. e., showing the characteristics consistent with the climate tendency rate. When the wind speed is less than 1.5 m·s-1, the rising rate of O3 concentration is faster, and when the wind speed is larger than 2.5 m·s-1, the concentration of O3 decreases rapidly. The concentration of O3 is negatively correlated with relative humidity, and the peak appears in the region with 30%-70% relative humidity. The influence of precipitation with different ranks on O3 concentration is quite different. The concentration of O3 is lower in moderate rain and higher in other ranks. The concentration of O3 during the day without precipitation is significantly greater than that during the day with precipitation. When there is haze, the concentration of O3 is significantly lower than that without haze. The positive correlation between O3 concentration and temperature is very obvious. There is also a positive correlation between O3 concentration and solar radiation, but the correlation level is lower than that with temperature. Figures and Tables | References | Related Articles | Metrics

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Analysis on climatic characteristics of continuous precipitation rain in autumn from 1961 to 2019 in He'nan province Ming-zhe DU, Tan LU, Yu-zhou ZHU, Rong-wei LIAO, Xiao-yi FANG 2021, 37 (4):  54-62.  doi: 10.3969/j.issn.1673-503X.2021.04.008 Abstract ( 358 )   HTML ( 13 )   PDF (4243KB) ( 254 )   Save Based on the daily data of 103 meteorological stations in He'nan province from 1961 to 2019, the temporal statistical characteristics and spatial distribution characteristics of regional continuous precipitation were analyzed using moving average, wavelet analysis, and EOF decomposition. The regional circulation of continuous precipitation was objectively classified using the self-organizing maps (SOM) of neural network method. The results show that the process of continuous precipitation in autumn in He'nan province is mainly 7-9 days, followed by more than 10 days. In the 1960s and 1980s, the regional continuous precipitation in autumn occurs frequently in He'nan province, and in the 1990s, it occurs less frequently. The frequency in the 1970s and 2010s is the same as the average annual frequency in the recent 59 years. In the 2010s, it is stronger than that in other years, and the intensity is the weakest in the 1990s. The mean precipitation of continuous precipitation in autumn in the 1970s has a quasi-5-year period, and in the first half of the 2000s and 1980s it has a 2-3-year period. In recent 59 years, the regional mean precipitation of continuous precipitation in autumn in He'nan province is higher in the south of the Yellow River than that in the north of the Yellow River, and higher in the mountainous area than that in the plain area. The distribution of large precipitation values is basically the same as that of the mountainous area. On the spatial distribution pattern of regional mean precipitation of continuous precipitation in autumn in He'nan province, the most important characteristic is the consistent variation pattern of the whole province, followed by the inverse pattern of the north and south. The SOM method can not only distinguish the difference of circulation shape, but also distinguish the occurrence time of circulation pattern and the periodic evolution characteristics of circulation during continuous rainy and cloudy periods. According to the SOM classification, there are 8 types of regional circulation types with continuous precipitation, which can be summarized as blocking, low trough and direct circulations in synoptic sense. Most of the regional continuous precipitation processes in He'nan province are the combination of two or three circulation types, and there is a conversion relationship among different circulation types. Figures and Tables | References | Related Articles | Metrics

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Effect of persistent blocking in Eurasian on temperature and precipitation in June in Greater Khingan Mountains and the precursor signal of temperature Bo ZHANG,Chao YU,Wei HUANG,Chuan-lei CHEN 2021, 37 (4):  63-69.  doi: 10.3969/j.issn.1673-503X.2021.04.009 Abstract ( 252 )   HTML ( 1 )   PDF (4232KB) ( 195 )   Save Based on a newly developed international discrimination method for identifying continuous closed blocking and open high ridge events, the frequency of 500 hPa persistent high-value events (PMZs) in different regions of Eurasia and its influence on summer temperature and precipitation in the Greater Khingan Mountains were discussed. The results show that the PMZ events in the region of Eurasia from 105°-125° E are closely related to the summer temperature in the Greater Khingan Mountains, especially in June. When PMZ events occur frequently in the 105°-125° E region, the subsidence warming caused by the abnormally high pressure from Lake Baikal to Northeast China and the clear sky radiation results in the high air temperature in the Greater Khingan Mountains region. Meanwhile, the relative humidity in the lower troposphere of this region is poor, combined with the abnormal anticyclonic circulation system in the middle and lower troposphere and the subsidence movement. It is not conducive to significant precipitation in the Greater Khingan Mountains region. In addition, the geopotential height in the Mesopotential Basin of Central Asia in May can be used as a pre-forecast index of the temperature in the Greater Khingan Mountains in June. When the geopotential height field in the Mesopotential Basin of Central Asia in May is high (low), the geopotential height in the east of Lake Baikal in June is high (low), corresponding to the temperature in the Greater Khingan Mountains in the same period is high (low). Figures and Tables | References | Related Articles | Metrics

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Analysis of circulation characteristics and cause of extremely high temperature and drought in midsummer of 2018 over Dalian area Xiu-ping WANG,Yan LI,Yue ZHANG,Han SAI,Xiao-xiao LI 2021, 37 (4):  70-77.  doi: 10.3969/j.issn.1673-503X.2021.04.010 Abstract ( 285 )   HTML ( 5 )   PDF (5221KB) ( 108 )   Save Based on temperature and precipitation data of seven meteorological stations from 1951 to 2018 in the Dalian area, the daily precipitation data of the 220 automatic stations during July and August of 2018, the NCEP/NCAR (National Centers for Environmental Prediction-the National Center for Atmospheric Research Reanalysis) daily mean reanalysis data during 1948-2018, the features of the persistent and serious high temperature and drought from July 1 to August 31 of 2018 in Dalian and its causes of atmospheric circulation anomalies were analyzed. The results show that it records a breaking extreme value of the number of long persistent high-temperature days and no-precipitation days in the midsummer of 2018 in the Dalian area. The rainfall is at least 70%-80% lower than the historical average. The Dalian area is controlled by an unusual anticyclone from the lower troposphere to the upper troposphere and jointed the teleconnection pattern over the Eurasia continent (EU pattern). At the same time, the pattern of "-+-" of 500 hPa geopotential height anomaly along the East Asian coast from south to north, which means to show a negative East Asia Pacific teleconnection pattern, a cyclonic circulation of wind anomalies at 850 hPa dominates around the south of Japan and Philippines. The abnormally westward and northward Western Pacific Subtropical high exist a tendency to move in opposite directions and the South Asian high, which is abnormally eastward and northward, their intensity enhance at the same time and overlap over the Dalian area, which causes atmospheric warming of the entire troposphere. Meanwhile, the East Asian subtropical westerly jet lies significantly northward compared with the average situations, so it is not favorable for the cold air moving southwards. Under the combined impacts of the subtropical and mid-high latitude atmospheric circulation over Eurasia, the Dalian region is affected by an abnormal anticyclone. The anomalous cyclonic circulation on the southern side of the anomalous anticyclonic circulation blocks the warm and humid airflow to Dalian, and its anomalous airflow divergence area of water vapor flux occurs in the region, combined with the descending motion effects, which result less precipitation. All the key reasons bring about the anomalous high-temperature and drought weather in Midsummer of 2018 over the Dalian area. Figures and Tables | References | Related Articles | Metrics

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Change characteristics of air temperature and urban heat island in Anshan from 1951 to 2017 Wei JIN,Wei-hua LIU,Jing LI,Xiao-yu KANG 2021, 37 (4):  78-85.  doi: 10.3969/j.issn.1673-503X.2021.04.011 Abstract ( 542 )   HTML ( 15 )   PDF (573KB) ( 165 )   Save Based on the data of daily mean, minimum and maximum air temperatures observed four times per day in the Anshan region from 1951 to 2017, the change characteristics of the annual, seasonal, and monthly mean air temperatures and extreme air temperatures and their variation ratios as well as the variation of urban heat island were analyzed. The results showed that the increasing trend is strongest for the annual mean minimum air temperature followed by the mean air temperature and is the weakest for the average maximum air temperature in Anshan in the studied period, and all these results have passed the significance test. The annual extreme maximum air temperature in Anshan shows a weak decreasing trend from 1951 to 2017 and experiences a decreasing trend from 1951 to 1987 (before the mutation) and an increasing trend from 1988 to 2017 (after the mutation). Inversely, the annual extreme minimum air temperature shows a significant increasing trend from 1951 to 2017, and a stronger increasing trend from 1951 to 1987 (before the mutation) relative to the former, while shows a decreasing trend from 1988 to 2017 (after the mutation). On the whole, the variations of extreme maximum and minimum air temperatures before and after the mutation are opposite. From 1958 to 2017, urban heat island intensity in Anshan is the largest for annual minimum air temperature, followed by the mean air temperature, and is the smallest for the maximum air temperature with the weakest increasing trend. The intensities of the urban heat island in Anshan in autumn and winter are stronger than in other seasons with a significantly increasing heat island index. Among the four regular temperature observations per day, the intensity of the heat island in Anshan is the smallest at 14 o'clock and the largest at 02 o'clock, and the heat island index shows a decreasing trend at 14 o'clock and a significantly increasing trend at the other times. The mean air temperature in Anshan shows a significantly increasing trend. The intensity of urban heat island and the heat island index in Anshan both increase significantly, especially at nighttime, indicating that the significant increase of the intensity of urban heat islands is one of the main reasons for climate warming in Anshan. Figures and Tables | References | Related Articles | Metrics

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Responses of growth, yield, and grain quality to reduced nitrogen application of spring maize Ni-na CHEN,Rui-peng JI,Na MI,Shu-jie ZHANG,Wen-ying YU,Yuan FANG,Yu-shu ZHANG 2021, 37 (4):  86-92.  doi: 10.3969/j.issn.1673-503X.2021.04.012 Abstract ( 112 )   HTML ( 2 )   PDF (549KB) ( 140 )   Save Given the current problem of excessive nitrogen application in Northeast China, studying the effects of reduced nitrogen application on spring maize growth and development, yield, and grain quality were of great significance to optimizing scientific management techniques of nitrogen fertilizer and promoting the green and efficient development of spring maize production. In this study, the Danyu 405 was used as the experimental material, and the farmer's habitual nitrogen application rate was used as the control. Three levels of 11.1%, 55.5%, and 100% nitrogen reduction experiments were conducted. The response mechanisms of yield and grain quality to reduced nitrogen application were analyzed. The results showed that at the seedling stage of maize, nitrogen reduction results in the reduction of growth and development indicators (plant height, stem diameter, leaf area index, dry and fresh weights of biomass, leaf specific gravity, etc.), which is not conducive to the growth of shoots and the distribution of dry matter to leaves. As the amount of nitrogen reduction increases, the reduction rates increase. After the seedling stage, the appropriate amount of nitrogen reduction promotes the growth of maize shoots, and the biological characteristics such as plant height, stem thickness, leaf area index, biomass, and leaf proportion have an increasing trend. A moderate amount of nitrogen reduction results in an increase in ear length, ear thickness, 100-kernel weight, theoretical yield, grain water content, and starch content, and a decrease in grain fat content, as well as a first increase then decrease in amino acid and crude protein content. With the increase in nitrogen reduction, the increased amplitudes in ear length, ear thickness, 100-kernel weight, and theoretical yield all decrease, and those in grain water content and starch content increase, and the decreased amplitude in fat content decreases. When the nitrogen application rate is 240 kg·hm-2 which is reduced by 11.1%, the increase rates of ear length, ear thickness, theoretical yield reach peak values which are 1.9%, 3.7%, and 11.5%, respectively, and the maize yield reaches the maximum i. e. 945.4 g·m-2, while the fat content of the grain i. e. 2.4 g·100 g-1 is the least, the amino acid content i. e. 83.9 μmol·g-1 is the largest and the crude protein content i. e. 6.8% is the highest. The research results provide more complete fertilization management for local corn production and guidance for farmers to apply fertilizer scientifically. Figures and Tables | References | Related Articles | Metrics

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Characteristics of abnormal continuous drought in summer and autumn in the middle and lower reaches of the Yangtze River in 2019 Qi GAO,Ming XU 2021, 37 (4):  93-99.  doi: 10.3969/j.issn.1673-503X.2021.04.013 Abstract ( 143 )   HTML ( 7 )   PDF (3848KB) ( 191 )   Save A server drought occurred in the middle and lower reaches of the Yangtze River basin from midsummer to fall in 2019. The characteristics of this abnormal drought were analyzed based on the NCEP/NCAR reanalysis data and meteorological observation data. The results showed that the drought is characterized by a long duration, less precipitation, more rainless day, higher average air temperature, and higher temperature days. The stronger western Pacific subtropical high(WPSA)and its north and west position are the main reason for continuous drought in summer and autumn in the middle and lower reaches of the Yangtze River. The negative vorticity extending eastward and the eastward of the South Asia high are in favour of the western extending of the WPSA. The middle and lower reaches of the Yangtze River are located on the right side of the East Asia subtropical westerly jet exit area and the superposition of negative vorticity in the middle and upper troposphere, which makes the vertical subsidence and divergence significantly enhanced. The dam formed by a high-pressure ridge from the Ural Mountains and Lake Baikal and maintained anomalous middle and high latitude circulation patterns such as the weaker the polar vortex and East Asia trough make it uneasy for the cyclonic disturbance in the westerly belt to affect the subtropical region, which is conducive to the stability of the WPSA and maintenance of drought. In addition, the frequent activities of the tropical system make the subtropical high further strengthened under the negative vorticity in the north of the tropical convective heating area, and leads to the changes of the southwest, cross-equatorial and southeast airflows in the lower troposphere on the northward transport path, and results in the weaker water vapor convergence in the middle and lower reaches of the Yangtze River, thus the drought maintained. Figures and Tables | References | Related Articles | Metrics

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Temporal and spatial distribution characteristics of lightning in the Yangtze River Delta of China from 2011 to 2019 Kai WANG,Li-ya ZHOU,Xiao-yu JU,Xiang-yang CHENG 2021, 37 (4):  100-106.  doi: 10.3969/j.issn.1673-503X.2021.04.014 Abstract ( 187 )   HTML ( 4 )   PDF (2524KB) ( 118 )   Save Based on the data observed by the ADTD lightning location system from the 27 stations in Jiangsu, Zhejiang, and Anhui provices from 2011 to 2019, the lightning frequency and intensity in the Yangtze River Delta region of China i. e. the integrated and coordinated development area including three provinces and one city(Jiangsu, Zhejiang and Anhui provinces, Shanghai)were statistically analyzed, and the spatial distributions of lightning frequency were also investigated with the EOF method. The results showed that in the Yangtze River Delta region of China, the number of negative lightning accounts for more than 95% of the total number, and the average current intensity of positive lightning is greater than the absolute value of that of negative lightning. The maximum and absolute minimum values of the average current intensity of positive and negative lightning appear in Jiangsu and Zhejiang provinces, respectively. The daily and monthly variation curves of total lightning frequency and intensity both feature single peak and single valley. For daily variation, the minimum value of total lightning intensity appears at 03:00 p. m. and the peak value appears during 04:00-05:00 p. m. For monthly variation, the total lightning frequency and intensity reach peak and minimum in August, respectively. The high-frequency period of positive lightning is in April, July, and November every year. The spatial distribution of total lightning frequency is entirely consistent with the terrain, that is, there is a high lightning frequency in high altitude areas, while the spatial distribution of total lightning intensity is opposite. According to the principal component analysis on the total lightning frequency, the cumulative variance contribution of the first 4 feature vectors reaches 51.07%, indicating both regional consistency and obvious difference. The spatial distribution pattern of lightning frequency can be divided into regional consistency, north-south division, stagger division, eastern-western division types. Figures and Tables | References | Related Articles | Metrics

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Analysis of characteristics of lightning current amplitude in Liaoning province from 2010 to 2018 Pan CHENG,Yang ZENG,Lei CHENG,Wen-jing PANG,Guang-liang XIAO,Xian-yuan RONG 2021, 37 (4):  107-113.  doi: 10.3969/j.issn.1673-503X.2021.04.015 Abstract ( 102 )   HTML ( 2 )   PDF (897KB) ( 206 )   Save The temporal variation characteristics of lightning current amplitude were analyzed using a statistical method based on the lightning data (ADTD) from 2010 to 2018 in Liaoning province. The cumulative probability densities of lightning current amplitude, calculated using the specification calculation formula and the formula recommended by IEEE, were compared with the real data curve to analyze the error. The formula recommended by IEEE was fitted with the least square method. The results show that the major CG lightning with a proportion of 89% are negative in Liaoning province from 2010 to 2018, and their current amplitudes are mainly concentrated between -50~-20 kA. The frequency of CG lightning increases year by year from 2011 to 2013 and then decreases year by year. The average lightning current amplitudes of total and negative CG lightning decreases from 2010 to 2013 year by year and then increases year by year. The CG lightning mainly occurs in the flood season from July to August, and the average lightning current amplitude is the highest in winter with a stable diurnal variation. The probability density curves of the total and negative CG lightning with the lightning current amplitude between 20-50 kA experience the fastest decrease, while those whose lightning current amplitudes are about 20 kA begin to decline slowly. The cumulative probability density curves of lightning current amplitude fitted with the formula recommended by IEEE are closer to the actual situation now than before. Figures and Tables | References | Related Articles | Metrics

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Spatiotemporal differentiation of short-duration rainstorm pattern and its influence on urban waterlogging in Tianjin Jing-fu CAO,Yan-juan YANG,Jun GUO,Jing CHEN 2021, 37 (4):  114-121.  doi: 10.3969/j.issn.1673-503X.2021.04.016 Abstract ( 273 )   HTML ( 8 )   PDF (5113KB) ( 142 )   Save Using the minute-level precipitation data from 1961 to 2018, the short-term rainstorm process in Tianjin was counted, and the rainstorm process was classified with the fuzzy recognition method. The temporal and spatial distribution characteristics of the rainstorm type were analyzed. Based on the urban rainstorm internal waterlogging numerical model of Tianjin, the impacts of different rain patterns on the total amount of waterlogged were assessed. The results showed that in the past 58 years, the short-term rainstorm in the Tianjin area is dominated by unimodal type (type I, type II, and type III), and the 60-minute rainstorm in each period is dominated by type Ⅰ and type Ⅲ. The 120-minute and 180-minute rainstorms are dominated by Type I. Short-term rainstorms occur concentratedly in July and August, and the rainstorm process is dominated by unimodal type. The 60-minute rainstorm type is almost type I in July, and type III is the most in August. Both the 120-min and 180-min rainstorm types are mainly Type I. The short-term rainstorm patterns in each area are mostly unimodal type, following the bimodal type and less the uniform type. From the perspective of dominant rainfall patterns in various regions, the 60-minute and 180-minute rainstorms are different, including type I, type III, and type V. The 120-minute rainstorm type is consistent with type I in all areas. There is obvious spatiotemporal differentiation in short-term rainstorm patterns in Tianjin, and different rain patterns affect the peak occurrence time of the total amount of waterlogging. Among them, the peak time of the total amount of waterlogging of type I appears early, which is the rain type that the urban drainage design focuses on. In summary, the impact of climate change and urbanization on the process of heavy rain should be fully considered in the engineering design. Figures and Tables | References | Related Articles | Metrics

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Analysis of the cause of rare foggy weather in Liaoning province Sai-di WANG,Qi YAN,Xiao-li WANG,Fang-da TENG 2021, 37 (4):  122-127.  doi: 10.3969/j.issn.1673-503X.2021.04.017 Abstract ( 253 )   HTML ( 12 )   PDF (2550KB) ( 84 )   Save Using conventional meteorological observations, intensive automatic stations, visibility observation data, and NCEP-FNL reanalysis data, the cause of a rare long-term large-scale foggy weather in Liaoning province was analyzed. The results showed that the process of heavy fog on November 20 to 22, 2014 is divided into two phases. After the explosive development of the fog at 14-16 o'clock on November 21, the extremely dense fog lasts 12 hours. This situation is rare in Liaoning province for nearly 20 years. The first stage of heavy fog is radiation fog. The weak warm advection in the lower layer before the fog is conducive to warming up. The weak cold advection in the middle layer during the fog is conducive to the occurrence of clear sky radiation conditions. Under the action of radiation cooling at night, a temperature inversion is formed below 975 hPa. The temperature drops, the temperature dew point difference decreases, and the relative humidity increases. The near-surface breeze is beneficial to reduce the temperature and the water vapor is not easy to flow out. The temperature inversion effect makes it difficult for the water vapor to diffuse to the upper layer, and the concentration of water vapor near the surface layer increases, resulting in the explosive development of the first stage of fog. The second stage of heavy fog is frontal fog. During the explosive development stage of heavy fog, there is no temperature inversion. A weak cold front passes, and convergence near the front causes water vapor to rise and cool and condense. At the same time, low clouds near the front cause raindrops to evaporate in the dry and cold air, which is conducive to water vapor saturation and condensation near the ground. This is the cause of the explosive development of heavy fog. It is relatively rare in Liaoning province. Figures and Tables | References | Related Articles | Metrics

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Characteristics of lightning activity during severe convective weather in Dalian area based on satellite data Yao-ren ZOU,Yun WANG,Shu-yi WANG,Dan XU 2021, 37 (4):  128-133.  doi: 10.3969/j.issn.1673-503X.2021.04.018 Abstract ( 134 )   HTML ( 6 )   PDF (2521KB) ( 150 )   Save Using the cloud top temperature (CTT) data retrieved from FY-4 satellite and radar echo data, we analyzed the characteristics of lightning activity in Dalian from June to September of 2019, focusing on the analysis of the correlation between the characteristics of lightning activity and radar echo and CTT in severe convective weather in this region on September 4, 2019. The results showed that the thunderstorm in this process started from the southeast of Dalian. In the initial stage of thunderstorms, cloud flashes are dominant, and the height of cloud flashes is mainly concentrated in 7-12 km. Lightning activity is mainly concentrated in the area where the radar echo intensity is greater than 30 dBz, and the corresponding cloud top height exceeds 8 km. There is a good correlation between lightning activity and CTT retrieved from the FY-4 satellite. Lightning mainly occurs in the area where the CTT is around 240-250 K. A quantitative analysis of the radar and lightning activity in Dalian from May to August of 2019 found that the lightning activity is mainly concentrated in the area near the radar combined reflectivity of 39.38 dBz, and the corresponding cloud top height is 8.21 km. Figures and Tables | References | Related Articles | Metrics

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Analysis on changing trend characteristics of acid rain in Shanxi province from 2006 to 2019 Ya-jun LI 2021, 37 (4):  134-138.  doi: 10.3969/j.issn.1673-503X.2021.04.019 Abstract ( 224 )   HTML ( 3 )   PDF (517KB) ( 40 )   Save Using the acid rain observation data from five stations at Wutai Mountain, Datong, Taiyuan, Changzhi, and Houma in Shanxi province from 2006 to 2019, the changes and spatial distribution characteristics of the number and frequency of acid rain, precipitation pH, conductivity K value on different time scales in Shanxi province were analyzed. The change characteristics of acid rain frequency with different acidity and rainfall levels were revealed. The results showed that the number and frequency of acid rain in Shanxi province from 2006 to 2019 show a downward trend. The annual average pH value ranges from 5.43 to 6.49, and the annual average conductivity K value ranges from 73.4 μs·cm-1 to 120 μs·cm-1. Among four seasons, the average pH is minimum in autumn, which is 5.70, and the highest in spring, which is 6.11. The conductivity K is higher in spring. Compared with each month, the pH value of acid rain is lowest in September, which is 5.58, and the highest in April, which is 6.20. The monthly average acid rain frequency is negatively correlated with the pH value of precipitation. The correlation coefficient R is 0.96. Compared with each station, the annual average precipitation pH and the conductivity K value in Taiyuan are significantly higher than in other cities. The acid rain pH value is Taiyuan (6.90) > Changzhi (5.95) > Datong (5.71) > Houma (5.57) > Wutai Mountain (5.55). The frequency of acid rain in different grades of precipitation varies greatly. The frequency of acid rain is the largest when it is light rain (1.0-10.0 mm). The frequency of strong acid rain and weak acid rain is 54.9% and 67.0%, respectively. When the precipitation exceeds 10.0 mm, the frequency of strong and weak acid rain decreases with the increase of precipitation. Figures and Tables | References | Related Articles | Metrics

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Study on the nonlinear response relationship between electricity consumption and air temperature in Tianjin area Hui LAN,Jia-hui YU,Jing-fu CAO,Yu-kun LIU,Mei-ling SUN,He HUANG 2021, 37 (4):  139-144.  doi: 10.3969/j.issn.1673-503X.2021.04.020 Abstract ( 494 )   HTML ( 279 )   PDF (905KB) ( 266 )   Save Using the threshold regression model and the nonlinear sliding regression model, the nonlinear relationship between the daily electricity consumption and temperature in Tianjin from 2014 to 2019 was explored, and the threshold temperature under different response relationships was calculated. The results showed that the threshold temperature in Tianjin is significantly different under different response relationships. Under the "V"-shaped nonlinear response relationship, the threshold temperature is 18.8℃, while under the "U"-shaped response relationship, the comfort zone of the linear asymmetric model is 12.3-23.4℃, and the comfort zone range of the nonlinear model is 13.7-21.7℃. Comparing the prediction effects of different models, it is considered that the "U" model is better than the "V" model, and the nonlinear model is better than the linear model. The analysis on the influence factors of the threshold temperature showed that relative humidity has a greater impact on the threshold temperature of the comfort zone and the cooling zone. The threshold temperature is 2.2℃ higher when the relative humidity is 30%-50% than when the relative humidity is 50%-70%. In contrast, relative humidity has little effect on the threshold temperature of the comfort zone and heating zone. The threshold temperature in Tianjin will change significantly over time, and the range of the comfort zone in 2002-2005 is 1.4℃ larger than that in 2014-2019. In practical applications, the threshold temperature should be selected according to the needs of the model, and the influence of relative humidity and time changes should be fully considered, to improve the accuracy of electricity consumption prediction. Figures and Tables | References | Related Articles | Metrics