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28 December 2022, Volume 38 Issue 6 Previous Issue    Next Issue

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Large-eddy simulations of the tornado over Funing on June 23 using a four-dimension variational data assimilation Da-zhi LIU,Dan YAO,Xu-dong LIANG 2022, 38 (6):  1-9.  doi: 10.3969/j.issn.1673-503X.2022.06.001 Abstract ( 158 )   HTML ( 12 )   PDF (3067KB) ( 92 )   Save A simulation is produced for the June 23, 2016 Funing (in Yancheng city, Jiangsu province) via WRF model and four-dimensional data variational assimilation.Results show that the first guess can be improved by assimilation of high-resolution surface and radar wind field observations from NCEP/GFS data, while convection cells are generated near Funing.Based on this, the simulation successfully produces hook echo and the tornado-like vortex structure when the large-eddy simulation is conducted on the 100-m grid.Furthermore, both convective available potential energy and vertical wind shear can reach the threshold value favorable for the occurrence of supercell in the synoptic scale.The high storm relative helicity (SRH) exhibits in the realm of parent supercell within a storm scale range, which is an indication of tornadogenesis.Although the intensity of SRH varies with resolution, its spatial distribution has not changed significantly, and signals are manifest using a horizontal grid spacing of 3 km. Figures and Tables | References | Related Articles | Metrics

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Influence of conventional observation assimilation on numerical prediction of a short-time heavy precipitation process in Jilin province Mei-hui QU,Wen-gang ZHU,Shu-hong ZHAO,Xiao-tong ZHU,Gang TU,Zong-ting GAO 2022, 38 (6):  10-19.  doi: 10.3969/j.issn.1673-503X.2022.06.002 Abstract ( 230 )   HTML ( 12 )   PDF (5799KB) ( 71 )   Save Based on the Weather Research Forecast (WRF) Model and its 3D-Var (three-dimensional variational assimilation) system, the numerical prediction experiments of water vapor data from aircraft, automatic station, conventional sounding and GPS during a short-time heavy rainfall in Jilin province on July 13, 2017, were carried out to study the influence of variant conventional observation assimilation on the initial field and forecast field of the model.The results show that the assimilation of conventional observation can improve the initial humidity field and temperature field, increase the humidity in the central part of Jilin province at the initial moment, and strengthen the temperature difference between the north and south sides of the real rain belt, and better predict the evolution process of the physical quantity.The influence of different conventional observation data assimilation on the prediction of humidity field, vertical velocity, wind field, and convective effective potential energy appears discrepantly.Assimilation of aircraft data increases regional overlaps between the strong vertical movement and the moisture, relative humidity, and wind shear in the precipitation area, being conducive to the intersection and transport of warm and cold airmass.Assimilation of automatic station data can increase the vapor in the precipitation center and southeast Jilin province, while the temperature field is mainly weakened.The assimilation of GPS vapor data has the most significant influence on the central wind shear forecast of precipitation, but has a less significant effect on the temperature field adjustment.The prediction of vertical velocity and wind field shows deviations due to the assimilation of radiosonde data.The TS scores, missing report rates, and empty report rates of 24-hour accumulated precipitation are better than those of unassimilated precipitation, and the TS scores of light rain, moderate rain, and heavy rainstorm are significantly improved.In general, the forecast of precipitation from the assimilated aircraft data is the closest to the real situation.Higher TS scores appear in the prediction of heavy and the above rain, especially in the area and intensity of 100-milli meter precipitation. Figures and Tables | References | Related Articles | Metrics

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Comparison of abnormalism of meteorological factors on two extreme precipitations triggered by low vortex in Hubei province in 2020 Liang-peng DONG,Ping-ping ZHANG 2022, 38 (6):  20-28.  doi: 10.3969/j.issn.1673-503X.2022.06.003 Abstract ( 196 )   HTML ( 10 )   PDF (4834KB) ( 114 )   Save Based on the daily NCEP/NCAR reanalysis data and other conventional observation data, the abnormal characteristics of meteorological factors of two extreme low-vortex precipitation in Hubei province on June 27 and July 7, 2020, were compared and analyzed.The results show that the two processes both occurred during the Meiyu period, and the two-trough and one-ridge pattern appeared over the mid and high latitudes at 500 hPa, with low vortices being formed in the lower layers.The vapor in the whole layer showed obvious persistent abnormal characteristics, and the central value was 2.5 standard deviations higher than the climate average.The extreme precipitation occurred mainly in the central and western parts of Hubei province on June 27 was a convective precipitation process in the warm front area under the combined dynamic action of the southwest vortex and the surface thermal low pressure.The central intensity of the ultra-low level jet stream was three standard deviations stronger than the climatic average, and the lowest value of the development of the warm low was two standard deviations lower than the climatic average, with the convective available potential energy (CAPE) value reaching more than 1000 J·kg-1 and appearing 1.5 standard deviations higher than the climatic average.The positive vorticity and negative divergence of the southwest vortex were abnormally strong and superposition at the same time, forming a strong upward movement.The extreme precipitation occurred mainly in the central and eastern parts of Hubei province on July 7 was a frontal precipitation process formed by the combined dynamic action of a low vortex and ground stationary front in Jianghan plain.The anomalously strong cold high in North China, which was about one standard deviation above the climatic average, leads to the formation of a significant Meiyu front on the ground.The strong convergence in front of the low vortex in Jianghan plain is superimposed with the static front on the ground, resulting in abnormally strong dynamic conditions, which remain stable for about 12 hours. Figures and Tables | References | Related Articles | Metrics

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The radar observation characteristics of multiple tornadoes in the peripheral circulation of two landfall typhoons in eastern coastal areas of China Lu-lu WEN,Rui HAN,Ji-rong ZHANG 2022, 38 (6):  29-38.  doi: 10.3969/j.issn.1673-503X.2022.06.004 Abstract ( 125 )   HTML ( 4 )   PDF (5503KB) ( 49 )   Save Using CINRAD/SA data, sounding data, automatic meteorological station data, and disaster reports, the environmental physical variations, tornado storm evolution, and mean radial velocity characteristics in the peripheral circulation of typhoon "Fung-wong" in the northern Jiangsu province and "Yagi" in northeast Shandong province were analyzed.The results show that the tornadoes occur in the northeast quadrant of the weakening low-pressure center of typhoon, and are characterized by small convective suppression energy, low lift condensation height, medium or strong convective available potential energy, strong low-level vertical wind shear, and large storm-relative helicity.Tornado storms mostly occur in the convective cloud belts in the peripheral circulation of a typhoon and appear as relatively isolated convective cells in small numbers.The multiple tornadoes in the peripheral circulation of typhoon "Fung-wong" occur in thunderstorms at the back of the cloud belt, and the tornado monomer has the characteristics of backward propagation.The multiple tornadoes in the peripheral circulation of typhoon "Yagi" are mainly caused by thunderstorms in the front of the cloud belt and have a long life and persistent mesocyclone.The storms have large velocity differences between adjacent velocity gate pairs at low-level at the tornadoes occurring stage and are accompanied by a significant small-scale vortex.Before the tornadoes occurring stage, the low-level cyclonic vortex of the storm is strengthened significantly and maintained, and then is quickly moved down to the storm bottom where the cyclonic vortex is strengthened significantly.After the cyclonic vortex reaches a particular intensity, tornadoes appear on the ground. Figures and Tables | References | Related Articles | Metrics

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Comparative analysis of cold- and non-cold-air snowfalls in Dalian from 2018 to 2019 Yan LI,Han SAI,Ming-yue XIN,Xiao-chu LIU,Hang CHENG,Hao LI 2022, 38 (6):  39-47.  doi: 10.3969/j.issn.1673-503X.2022.06.005 Abstract ( 205 )   HTML ( 12 )   PDF (2897KB) ( 217 )   Save The two difficult prediction processes i.e.cold- and non-cold-air snowstorms in the Dalian area from 2018 to 2019 were analyzed using the data from the automatic station, conventional meteorological observation, NCEP reanalysis, Radar, and 1 km×1 km grid products.The results indicate that the process of the cold-air snowstorm has northeast airflow and strong cold advection below 500 hPa.The wind speed above 1 km is higher than that below 1 km.The process of a non-cold-air snowstorm has wind shear from near the ground to 850 hPa, a convergence line on the ground, and an inversion layer above 850 hPa.The wind direction near the ground is south and southwest.Two processes belong to unstable snowfall and both have meso and small scale convergence lines on the ground.The unstable conditions of a cold-air snowstorm are established earlier and are more unstable than that of a non-cold-air snowstorm.The cold-air snowstorm area is located downstream of the meso and small scale convergence line uplift area, while the non-cold-air snowstorm area is located in the meso and small scale convergence line uplift area.When the dry and cold air from the northwest passes through the Bohai sea surface, the air-sea interaction makes the water vapor on the warm ocean surface evaporate and converge for a long time, which is the source of the water vapor of the cold-air snowstorm.The water vapor of the non-cold-air snowstorm mainly comes from the horizontal transportation of warm and humid air in the south, and the water vapor condition is established for a short time.The cold-air snowstorm affecting Dalian has the radar echo moving from northwest to southeast and a large area of strong echo.Inversely, the non-cold-air snowstorm has the radar echo moving from southwest to northeast and moves consistent with the moving direction of the echo. Figures and Tables | References | Related Articles | Metrics

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The vertical distribution characteristics of the spectral dispersion and the number concentration of cloud droplets during a warm cloud process in Taiyuan of Shanxi province Zhi-ming YI,Su-ying YANG,Yi-yu LI,Na KANG,Guo-hang YU,Ya-ru LI,Yan ZHANG 2022, 38 (6):  48-56.  doi: 10.3969/j.issn.1673-503X.2022.06.006 Abstract ( 162 )   HTML ( 1 )   PDF (1358KB) ( 37 )   Save Based on an aircraft observation of a warm cloud in Taiyuan, Shanxi province on August 31, 2018, we analyzed the vertical distribution and causes of the number concentration (Nc) and spectral dispersion (ε) of cloud droplet.The results show that Nc and ε vary complexly with altitude, and their vertical distributions are mainly affected by vertical velocity, inversion zone, and clamp coil in clouds.When the upwelling (or downwelling) increases (weakens) with height, both ε and Nc increase, and show a positive correlation with each other.When there is a maximum of upwelling or downwelling, the upwelling is easy to produce collision coalescence growth, and Nc decreases with the increase of height and has a negative correlation with ε.However, the downwelling promotes aerosol reactivation and then makes cloud droplets increase and has a negative correlation with ε.The thickness and intensity of the inversion zone affect the vertical distribution of ε and the correlation between Nc and ε in the inversion zone and its upper cloud area.When the inversion layer is thicker, ε decreases with the increase in height, and Nc and ε are positively related.Inversely, when the inversion layer is thin, ε increases with the increase of height, and Nc and ε are negatively related.The upper cloud in the inversion area is not saturated, and the cloud droplet is evaporated, both Nc and ε decrease with increasing height and are positively correlated.The entrainment near the cloud top makes Nc decrease with the increase in height, and there is a positive correlation between Nc and ε. Figures and Tables | References | Related Articles | Metrics

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Comparative analysis of cloud forecast for top ten airports in China based on cloud diagnosis algorithms Ji-liang XU,Wei ZHANG,Yan-hua SU,Lei GU 2022, 38 (6):  57-64.  doi: 10.3969/j.issn.1673-503X.2022.06.007 Abstract ( 95 )   HTML ( 2 )   PDF (513KB) ( 57 )   Save The 6h numerical forecast data from NCEP reanalysis data FNL were selected to calculate the cloud base height and cloud cover of the lowest layer clouds below 1500 m in the top ten airports in China using the cloud diagnosis algorithm.The corresponding airport routine weather reports were used to check the calculation results and make a comparative analysis.The results showed that regardless of cloud cover, the accuracy rate and miss rate of the C cloud cover diagnosis method (C method) were lower than those of the WR95 method and optimized WR95 method (WR95opt) in most airports.The TS score of WR95 and WR95opt in Beijing, Shanghai Pudong, Kunming, and Shanghai Hongqiao is slightly higher than that of the C method, while in Chengdu, Xi'an, and Chongqing it is lower than that of the C method.While considering cloud cover, the calculation results from these methods are poor, the accuracy and TS score decrease, and the miss ratio increases.The calculation results of the C method for sparse cloud and above cloud are worse than that of less cloud.The relative error difference of cloud height calculated by each method is large, and the relative error spreads in both positive and negative.The calculation result of WR95opt in Beijing, Shanghai Pudong, Guangzhou, Shenzhen, Shanghai Hongqiao, Hangzhou, and Kunming is better, the calculation result of WR95 in Chengdu is better, and the calculation result of C method in Xi'an and Chongqing is better. Figures and Tables | References | Related Articles | Metrics

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Validation of real-time analysis products in total cloud cover in Sichuan province Wei WU,Xiao-long HUANG,Xu GUO,Hui-bing WANG 2022, 38 (6):  65-72.  doi: 10.3969/j.issn.1673-503X.2022.06.008 Abstract ( 111 )   HTML ( 4 )   PDF (1503KB) ( 86 )   Save Based on the total cloud cover data observed by 41 national ground meteorological observation stations in Sichuan province in 2019, the total cloud cover real-time analysis products developed by National Meteorological Information Center were validated from various aspects.The results show that there are some differences in the evaluation results of different spatial matching methods.The real-time analysis products can reflect the variation of total cloud cover, but its value is lower than the ground human observations.The real-time analysis products have a good ability to identify the total cloud cover in Sichuan province, the accuracy rate in summer is higher than that in winter, and the accuracy rate in Sichuan Basin is higher than that in the Western Sichuan Plateau and Panxi Region.From the test of the total cloud cover component level, the consistency rate is the highest, the error is the smallest on sunny days, and the accuracy rate is the highest on cloudy days. Figures and Tables | References | Related Articles | Metrics

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Distribution characteristics of wave elements in the sea area covered by Dalian offshore passenger routes from 2010 to 2019 Shan HUANG,Xiao-dong WU,Jian-jian WANG,Tian-jiao ZHOU,Yan WANG,Hui-lin CHANG 2022, 38 (6):  73-80.  doi: 10.3969/j.issn.1673-503X.2022.06.009 Abstract ( 129 )   HTML ( 9 )   PDF (2089KB) ( 99 )   Save Based on the wind and wave field data provided by the Global Atmospheric and oceanic reanalysis data of the European Center for Medium-Range Weather Prediction (ECMWF) from 2010 to 2019, the 10 m wind speed, effective wave height of mixed waves and average period of the sea area of Dalian offshore passenger transport routes were statistically analyzed.The multi-year average, seasonal, and inter-monthly variations of each wave element and surge index were analyzed.The results show that the effective wave height of the mixed waves is significantly affected by the surface wind field.The wave elements have obvious seasonal variation characteristics.The effective wave height of the mixed waves and the 10 m wind speed on the sea surface are the maximum in winter and the minimum in summer, while the maximum and minimum of the average period of the mixed waves are in summer.The mixed waves in spring and summer are mainly swell waves.Under the influence of cold air, the mixed waves are mainly wind waves in the sea areas in winter and the northern Bohai Sea in autumn.The offshore wind waves in Dalian are affected by the surface wind field, while the surge waves are mainly affected by the topography. Figures and Tables | References | Related Articles | Metrics

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Characteristics of air pollution before and during winter heating period in Harbin from 2014 to 2017 Shu ZHANG,Lin-jing QUE,Ying WANG,Lei WANG,Chen LUAN,Zhao-bin SUN 2022, 38 (6):  81-88.  doi: 10.3969/j.issn.1673-503X.2022.06.010 Abstract ( 128 )   HTML ( 6 )   PDF (1324KB) ( 54 )   Save Using conventional meteorological data, air pollutant concentration monitoring data, and meteorological reanalysis data (The European Centre for Medium-Range Weather Forecasts, ECMWF, and National Centers for Environmental Prediction, NCEP) in Harbin from 2014 to 2017, we compared the evolution and diurnal variation of five criteria air pollutants (PM2.5, PM10, CO, SO2, and NO2) before and after the winter heating period from 2014 to 2017, and analyzed the causes of air pollution in combination with meteorological data.The results indicated that during the heating period, the concentration of five criteria air pollutants increase significantly and remain at a relatively high level.The daily mean SO2 concentration is mostly affected by heating among all the five air pollutants.Concentrations of PM2.5, PM10, CO, and NO2 all have peak values or larger values in early November.PM2.5 and PM10 vary consistently with each other, exhibiting high homology.In terms of diurnal variation, PM2.5, PM10, NO2, SO2, and CO all exhibit bimodal distributions, but their variations are not completely consistent.Air pollutants released by coal burning during the heating period and the meteorological conditions that are not conducive to pollutants' diffusion lead to the aggravation of air pollution in Harbin.During the overlapping period of straw burning and heating emissions, straw burning seriously affects air quality, which can contribute to 69.4% of PM2.5 concentration. Figures and Tables | References | Related Articles | Metrics

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Urban waterlogging simulation in Tianjin based on designed rainstorm patterns Jing CHEN,Ming-cai LI,Jing-fu CAO,Ming-ming XIONG,Pei-yan LI,Hui WANG,Shu-ming ZHAO 2022, 38 (6):  89-97.  doi: 10.3969/j.issn.1673-503X.2022.06.011 Abstract ( 123 )   HTML ( 6 )   PDF (2192KB) ( 140 )   Save To analyze the impact of different design rainstorm patterns on the waterlogging in the central urban area of Tianjin, the numerical simulation of urban waterlogging in the central urban area of Tianjin was conducted using the Tianjin urban rainstorm waterlogging model (TJUWM), a hydrodynamic mathematical model.The validation of simulation results during three different precipitation processes in 2018 and 2019 in Tianjin shows that this model has a certain simulation accuracy.Thereafter, the waterlogging processes with different return periods, duration, and probabilities are simulated, and the simulated total water amount and area of waterlogging are compared and analyzed.Among three representative-designed rainstorm patterns, the rainstorms with short duration (6 h) and short return period (< 10 years) have a long duration of heavy precipitation, earlier peak time, and the largest total water amount and waterlogged area.The rainstorms with long return period (≥10 years) have concentrated heavy precipitation, the earliest peak time, and the largest total water amount and area.For precipitation with the equal duration of 12 h and 24 h, the simulated statistical results are the opposite. Figures and Tables | References | Related Articles | Metrics

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Study on multi-dimensional dynamic hybrid imaging technology based on FY-4A/AGRI Jun-jie YAN,Jian-hua QU,Fang-fang ZHANG,Xue-xing GUO,Yan-ting WANG 2022, 38 (6):  98-105.  doi: 10.3969/j.issn.1673-503X.2022.06.012 Abstract ( 107 )   HTML ( 5 )   PDF (1422KB) ( 97 )   Save We made the research on multi-dimensional dynamic hybrid imaging method in this study.In the process of visible light true color imaging of FY-4A data, the channel mixing method is applied to generate a "green light channel", which retains the data gradient information, avoids color jumps, and achieves smoothness and seamless splicing in the horizontal direction and dynamic superimposition of multi-layer images in the vertical direction.This method can assign dynamic transparency factors to each pixel and generate multi-channel color composite images with better quality.The analysis results of color image products generated by the multi-dimensional dynamic hybrid imaging technology show that the visible light region restores the true color of the surface during the day.The high clouds at night are white, and the low clouds are light blue, which can better distinguish the characteristics of the night clouds.The color transition at dawn and dusk is natural, and the image product quality is high.This technology has been widely used in the FY-4A weather imaging product production system.The system has been promoted in 43 cities and counties in China, which has promoted the in-depth application of FY-4A data in the fields of meteorology, ecological environment, and disaster reduction. Figures and Tables | References | Related Articles | Metrics

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Relationship between terrain factors and ground lightning activity in Changsha area based on DEM data Ming-wei ZHOU,Yue-yu LIU,Hao HUANG,Xin HU,Wei LIU 2022, 38 (6):  106-111.  doi: 10.3969/j.issn.1673-503X.2022.06.013 Abstract ( 99 )   HTML ( 9 )   PDF (1361KB) ( 93 )   Save Based on the ground lightning location data and 30-m precision elevation data in Changsha area from 2009 to 2018, the spatial distribution of ground lightning parameters was analyzed using mathematical statistics and regression analysis, and an annual average return strike frequency model and an average current intensity model for ground lightning per unit area were established based on surface factors. The results showed that ground lighting strikes mainly occur on plains and hills. With the increase in altitude, the return strike frequency of ground lightning in Changsha area decreases, and the average current intensity of ground lightning exhibits an increasing trend. The current intensity is mainly concentrated within the range of 25~65 kA, of which 77.84% occur in the plain. We used the lightning data in 2019 to test the model and found that the calculated value of annual return strike frequency per unit area is smaller than the observed value, with an average error of 9.20%. The average current intensity model has overestimation compared with observations, with an error of about 4.40%. Figures and Tables | References | Related Articles | Metrics