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28 April 2022, Volume 38 Issue 2 Previous Issue    Next Issue

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Comparison of characteristics and causes of two northward typhoon rainstorms in the Southeast Peninsula of Liaoning province Yao-peng CUI,Lei YANG,Li SUN,Yan-bo GAO,Hai-ning WEI,Jing-jing HUA,Jing-xuan CUI,Chun-xi LIU 2022, 38 (2):  1-11.  doi: 10.3969/j.issn.1673-503X.2022.02.001 Abstract ( 514 )   HTML ( 213 )   PDF (4936KB) ( 321 )   Save Based on the conventional meteorological observations, the National Centers for Environmental Prediction (NCEP) Final (FNL) reanalysis data, satellite and radar measurements, we compared the characteristics and causes of precipitation during two extreme rainstorm events in the Southeast Peninsula of Liaoning province caused by the Typhoon "Damrey" in 2012 (Process 1) and the Typhoon "Haitang" in 2017 (Process 2) in this study.The results indicated that the precipitation during the two processes shows different characteristics.The stable and persistent heavy precipitation (lasting for 30 h) occurs over large areas during Process 1, due to the train effect caused by the multiple mesoscale cloud clusters triggered by a typhoon inverted trough.Process 2 is characterized by higher hourly precipitation intensity (reaching 113 mm·h-1) and obvious convective precipitation.During Process 2, small-scale cumulus continue to regenerate and pour into the mesoscale cloud clusters.The radar charts show backward propagation, with basic reflectivity of strong storms of 50-60 dBz.The mesoscale convergent winds expand up to 9 km, and convective clouds develop more vigorously.Process 1 develops within the typhoon inverted trough, and Process 2 is generated by the interaction between warm-humid air transported by the typhoon and dry-cold air in the troposphere.During the two processes, a water vapor conveyor belt spanning 10 latitudes is formed between the typhoon remnant vortex and the Subtropical High, with the water vapor flux at 850 hPa reaching 20-25 g-1·cm-1·hPa-1·s-1 and the values of specific humidity and water vapor flux divergence reaching the rainstorm forecast thresholds for the landing typhoon in Liaoning province.The long-distance typhoons play a key role in blocking the southward movement of the Subtropical High and establishing the guiding airflow for the typhoons' northward movement.Due to the residual vortex inverted trough of typhoon "Damrey", the convergence layer extends from the ground to the height of 500 hPa during Process 1, exhibiting stronger dynamic uplift conditions.During Process 2, the pseudo-equivalent temperature at 850 hPa reaches 354 K, and the potential instability is stronger.Due to the large-scale convergence and forced uplift of terrains, deeper convective clouds are formed and generates more distinct convective precipitation. Figures and Tables | References | Related Articles | Metrics

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Correction tests of ECMWF modeling quantitative precipitation using frequency matching method in Jiangxi provice Hui-meng BAO,Da-feng GUO,Wei LI 2022, 38 (2):  12-20.  doi: 10.3969/j.issn.1673-503X.2022.02.002 Abstract ( 257 )   HTML ( 184 )   PDF (2048KB) ( 128 )   Save Based on the precipitation forecast data from European Centre for Medium-Range Weather Forecasts (ECMWF) and precipitation observations at 93 meteorological stations in Jiangxi province from 2016 to 2019, we analyzed the rainfall frequency using four statistical methods and conducted the correcting test (without zone division) on precipitation forecast based on a frequency matching method.In addition, we also conducted correcting test on precipitation during flood seasons over different zones according to the climatic characteristics of a rainstorm in Jiangxi province and analyzed some typical heavy precipitation events.The results show that the frequency matching method reduces the false alarm rate of light rain and the missing alarm rate of heavy rain and rainstorm, leading to obvious improvement in the forecast technique.Among the four statistical methods for a precipitation frequency, the quasi-symmetric sliding average method performs the best.The zone-division tests make a better correction than the tests without zone division, and they have better correction capability in the modelling precipitation prediction using positive techniques than that without using techniques.For the rainstorm prediction with poor (Test Sore, TS=0), normal (0 < TS < 0.2), and good (TS ≥ 0.2) forecast levels, their improvement probabilities using zone-division tests are 40.8%, 89.1%, and 66.7%, respectively.The predicted rainfall areas after using zone-division correction based on the frequency matching method are closer to the observation, however, the locations of the heavy rainfall can not be improved.The correction method has a better (poor) performance for the cases with the shape and location of predicted heavy precipitation close to (having a large deviation from) the real situation. Figures and Tables | References | Related Articles | Metrics

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Validation of three forecast products of air temperature in Heilongjiang province Ying-ying MENG,Shu-ling LI,Ling ZHAO,Xue-mei BAI,Min-hui YAN 2022, 38 (2):  21-30.  doi: 10.3969/j.issn.1673-503X.2022.02.003 Abstract ( 223 )   HTML ( 175 )   PDF (2760KB) ( 81 )   Save Using the T639 model forecast products and air temperature observations at 83 national weather stations in Heilongjiang province, we selected forecast factors using an optimal selection method, and established the Model Output Statistics (MOS) prediction equations for daily maximum air temperature (TMAX) and daily minimum air temperature (TMIN) using a multiple regression method.In addition, we comparatively analyzed and validated the forecast performance of TMAX and TMIN from the MOS, the guide forecasts of the Central Meteorological Observatory (SCMOS), and three air temperature forecast products from the T639 model, and examined the consistency of spatiotemporal distribution between the predicted and observed air temperature using the Empirical Orthogonal Function (EOF) method.The results showed that the MOS and SCMOC perform better in predicting the spatiotemporal distribution of air temperature, while the T639 model performs relatively poorer.The values of 2℃ forecast accurate rate (TT2) for TMAX and TMIN from the MOS and SCMOC are mostly higher than those using the T639 model, and the TT2 values for TMAX/TMIN from the MOS are higher/lower than those from SCMOC.MOS can improve the air temperature forecast from the T639 model, especially for the TMIN forecast in winter.There is a negative correlation between the improvement of MOS relative to the T639 forecast and the performance of the T639 forecast.The MOS's improvement is better over mountain areas with low TT2 predicted by the T639 model than that over plain areas.In spring and summer, the MOS's improvement is better for the TMAX with low TT2 than the TMIN, while in winter, the MOS improvement is better for the TMIN with low TT2 than the TMAX.This MOS air temperature forecast method has a good forecast capability and can be applied to the interpretation and application of other numerical model products.The SCMOC can be used in the TMIN forecast in Heilongjiang province considering its good forecast performance; the TMIN parameter is usually difficult to forecast in Heilongjiang province. Figures and Tables | References | Related Articles | Metrics

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Intraseasonal variation of wintertime air temperature in Heilongjiang province and circulation anomalous characteristics from 1961 to 2019 De-jun LOU,Ji WANG,Xian-wei ZHOU,Zhi-min LI 2022, 38 (2):  31-39.  doi: 10.3969/j.issn.1673-503X.2022.02.004 Abstract ( 281 )   HTML ( 15 )   PDF (3036KB) ( 104 )   Save Based on air temperature data, the National Centre for Environment and Prediction (NCEP) reanalysis data, and circulation indices in Heilongjiang province in winter from 1961 to 2019, we analyzed the intraseasonal variation of wintertime air temperature in Heilongjiang province and the circulation anomalous characteristics using the methods of multivariate empirical orthogonal function (EOF) decomposition, synthetic analysis, correlation analysis, etc.We also compared the relative contribution of main circulation factors in the different modes during the intraseasonal evolution of temperature.The results showed that the intraseasonal variation of wintertime air temperature in Heilongjiang province is one of its basic features.There are three major modes for wintertime air temperature in Heilongjiang province, including the intraseasonal consistent variation, the antiphase variation between December and January-February in the next year, and the antiphase variation between December-January and February.When the air temperature in winter shows the first mode and distributes uniformly warm (cold), the circulation is characterized by an Arctic Oscillation (AO) positive (negative) phase and relatively weaker (stronger) East Asian winter monsoon.When a warm-cold transition occurs in winter, significant variation can be found in the intraseasonal polar vortex, the upper-level jets, the Siberian High (SH), and EAWM intensity, and mid-high latitudes circulation meridian, etc.The circulation in January in the second mode and in February in the third mode show a similar distribution to the Polar Eurasian (PEA) and the East Atlantic (EA) teleconnections, respectively.AO, SH, EAWM, PEA, and EA are the important influencing factors on the intraseasonal variation of wintertime air temperature. Figures and Tables | References | Related Articles | Metrics

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Characteristics of the continuous cold vortex over Northeast China from 1979 to 2019 Qi YAN,Shuang LI,Jing-long LU,Fang-da TENG 2022, 38 (2):  40-45.  doi: 10.3969/j.issn.1673-503X.2022.02.005 Abstract ( 280 )   HTML ( 25 )   PDF (1118KB) ( 262 )   Save Using ERA5 reanalysis data from 1979 to 2019, the characteristics of the northeast cold vortex with a lifetime of > 3 days during the forty years were analyzed using statistical methods including the Morlet wavelet and Mann-Kendall test.The results show that the continuous northeast cold vortex occurred 32.8 times on average, with a maximum of 41 times and a minimum of 22 times per year.The continuous northeast cold vortex process mostly happened in May and June and the cycles of annual times were 17 years, 9 years, 5 years and 3 years, respectively.The longer the duration of northeast cold vortex processes were, the less frequent they may occur.The longest duration could reach 13 days and those lasted 3 or 4 days appeared most frequently.The durations reaching 9 or 10 days occurred once per ten years and those lasted more than ten days appeared most significantly in June.The frequencies from high to low were the central vortex, north vortex and south vortex, with little monthly differences for the north vortex and much more during May and June for the center and south vortex.The cold vortex centers were most located in the region of 120°-130°E, 45°-55°N, and the pattern of two troughs and one ridge was the unique circulation background in the northeast cold vortex extreme months during both summer and winter half years over East Asia. Figures and Tables | References | Related Articles | Metrics

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Aerosol vertical variations and the origin analysis on a pollution event in Shenyang on March 2021 Xiao-xiao LI,Hu-jia ZHAO,Yan-jun MA,Xiao-chu LIU,Si-xu LI,Xiao-lan LI,Yang-feng WANG,Ye HONG 2022, 38 (2):  46-54.  doi: 10.3969/j.issn.1673-503X.2022.02.006 Abstract ( 228 )   HTML ( 22 )   PDF (3418KB) ( 274 )   Save Based on the observation data of particulate matter mass concentration, radiosonde data, NECP reanalysis data and ground-based Lidar, a pollution event in Shenyang from March 13 to 15, 2021 was analyzed.The variations of PM concentration, atmospheric circulation background and aerosol vertical distribution were discussed.The results show that PM2.5 mass concentrations peaked at 06:00-07:00 on March 13 with the values of 220.0-230.0 μg·m-3, followed by a significant decline at 12:00 on March 15 and a significant enhancement of PM10 at 15:00 with the concentrations up to 258.3 μg·m-3.High levels of SO2 and NO2 appeared at about 10:00 on March 13 with the concentrations of 40.1 μg·m-3 and 101.3 μg·m-3, respectively.The maximum concentration of CO appeared between 16:00 and 17:00 on March 13 with the values of around 8.8 mg·m-3.The highest levels of ozone always appeared in the afternoon with the values of 102.4-113.7 μg·m-3 from 12:00 to 16:00 on March 13 and 14.Due to the enhancement of Mongolian cyclone during its eastward moving, the dust was transported southeast by the northwest wind.The unstable stratification appeared while the dust was flourishing in Shenyang, accompanied by significant upward movement, which was conducive to the vertical mixing and transport downstream of dust particles.The maximum aerosol extinction appeared at the height of 0.7 km with the values of around 6.0 km-1 at 10:00 on March 15, when the surface lidar depolarization ratio significantly increased to 0.4-0.5, indicating that the dust or floating dust was dominated by non-spherical particles (coarse particles). Figures and Tables | References | Related Articles | Metrics

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Meteorological transport conditions and spatial variations of contribution source for PM2.5 in Anshun of Guizhou province Qing CAO,Xiao-ping GU,Chi-peng ZHANG,Zhen-hong CHEN,Zhe-hong WU 2022, 38 (2):  55-61.  doi: 10.3969/j.issn.1673-503X.2022.02.007 Abstract ( 149 )   HTML ( 12 )   PDF (1318KB) ( 76 )   Save Using air pollutant data and meteorological data from Anshun, Guizhou province, the characteristics of air quality and pollutants from 2015 to 2019 in Anshun were analyzed.Using HYSPLIT backward trajectory model, along with GDAS data and PM2.5 concentration data, seasonal transport pathways and pollution trajectories were analyzed as well.The potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) were applied to evaluate the vertical and horizontal variations of transport pathways in all days with PM2.5 polluted (i.e., concentrations above 75 μg·m-3).The results show that PM2.5 was the major pollutant in the urban area of Anshun and air transport accounted for a large proportion for this in winter, with the major pathways to the northeast and south of Guizhou province.Polluted airmass from the northeast direction led to PM2.5 pollution, during which the tracks were mainly distributed at the height of 880-980 hPa.The areas with high potential source values were mainly concentrated over the whole area of Guiyang, Bijie Zhijin County, Qianxi County, Jinsha County, etc., whereas the areas with high contribution values were mainly concentrated in Ziyun County, Zhenning County, Bijie Zhijin County, Dafang County, etc. Figures and Tables | References | Related Articles | Metrics

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Characteristics of ozone pollution and its relationship with meteorological conditions from 2016 to 2019 in Tangshan Xiao-dong ZHANG,Guan WANG,Xiu-ling WANG,Fen-e CUI,Yan-ping ZHENG 2022, 38 (2):  62-69.  doi: 10.3969/j.issn.1673-503X.2022.02.008 Abstract ( 193 )   HTML ( 14 )   PDF (789KB) ( 268 )   Save Based on the hourly data of O3 concentration and meteorological data in Tangshan from 2016 to 2019, the characteristics of O3 pollution and its relationship with meteorological conditions were analyzed.The results show that the number of days when the concentration of O3 exceeds the threshold value in Tangshan is 53 days in 2016 and that in 2017 to 2019 is more than 70 days per year, so the pollution degree is high.The monthly average concentration of O3 shows a bimodal distribution.The concentration of O3 is the highest (with 112.26 μ g ·m-3) in June, followed by September.The days with the concentration of O3 exceeding the standard occur from March to October, and mostly happen in summer, followed by spring and autumn.The concentration of O3 reaches its maximum at 15:00, and shows a unimodal distribution during the day.O3 concentration is positively correlated with temperature and wind speed, and negatively correlated with relative humidity.High temperature is an important factor leading to excessive concentration of O3.When the daily maximum temperature exceeds 25℃, it should be considered that the concentration of O3 exceeds the standard.When the relative humidity is about 50% and ranges from 60% to 80%, the overstandard rate of O3 concentration is more than 30%.When the relative humidity is 60% to 70%, the average concentration of O3-8h reaches the maximum.The over standard rate of O3 concentration in summer and autumn is related to the surface breeze and lower mixing layer height during the daytime.When the average wind speed during the day is greater than 1 m · s-1 and less than or equal to 4 m ·s-1, the overstandard rate of O3 concentration is higher.The weather situation prone to moderate or above O3 pollution is influenced by northwest airflow or high-pressure ridge at 500 hPa, and southwest or south airflow passes through at 850 hPa.The ground is mostly in the rear of high pressure, front of the low pressures, or convergence area of low pressure. Figures and Tables | References | Related Articles | Metrics

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Characteristics of the vertical distribution of CH4 in the troposphere in autumn in Shijiazhuang based on aircraft observations Rong MAI,Yang YANG,Gen-chang FAN,Feng LV,Xiao-bo DONG,Miao LIANG,Bo YAO 2022, 38 (2):  70-77.  doi: 10.3969/j.issn.1673-503X.2022.02.009 Abstract ( 169 )   HTML ( 11 )   PDF (1180KB) ( 203 )   Save To study the vertical distribution characteristics of CH4 within the troposphere in autumn in Shijiazhuang, the King Air 350 aircraft with Picarro greenhouse gas online observer and meteorological observation equipment were used to detect CH4 concentrations over Shijiazhuang (600-5500 m) in September, 2018.A total of seven flights were made during the survey period, and seven CH4 concentration profiles were obtained.The results show that the average concentration of CH4 near the surface layer (below 1000 m) over Shijiazhuang is positively correlated with that at Shangdianzi station during the same period (r=0.81, P < 0.03).During the detection period, the minimum CH4 concentration of the seven profiles is 1898×10-9, the maximum is 2219×10-9, and the average concentration is 1981×10-9.The seven profiles obtained by observations are all consistent.The concentration above 2000 m increases first and then decreases with height.The backward trajectory mode-HYSPLIT model is used to analyze the main air transport paths at different altitudes over Shijiazhuang during the detection period.The transport pathways at 600 m are shorter, and the concentration of CH4 is greatly influenced by local emissions.At 3000 m, the air mass with higher CH4 concentration may be transported over Shijiazhuang by the west-southwest path.The air mass transport at 5000 m has little influence on CH4 concentration.The CH4 concentration at this level is relatively stable and insensitive to the change of transport path. Figures and Tables | References | Related Articles | Metrics

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Spatial and temporal characteristics of climatic comfort and analysis of key meteorological factors in Hohhot-Baotou-Ordos region Jia-qi ZHAO 2022, 38 (2):  78-88.  doi: 10.3969/j.issn.1673-503X.2022.02.010 Abstract ( 226 )   HTML ( 11 )   PDF (1484KB) ( 173 )   Save Based on the daily meteorological data in the Hohhot-Baotou-Ordos region from 1970 to 2019, the daily temperature-humidity index (THI), wind-efficiency index (WEI), index of clothing (ICL), and comprehensive comfort index (CCI) were used as the evaluation index for climate comfort.The characteristics of the climate comfort index, the key meteorological factors affecting the index, and the spatial distribution characteristics of comfortable days in this region were analyzed using trend analysis, Mann-Kendall test and path analysis.The results show that WHI, WEI and CCI show a significant upward trend, while ICL shows a significant downward trend.The comfort period is from April to October.The number of comfortable days reaches 68%-93% from May to September.The whole period from June to August is comfortable or relatively comfortable.Under the background of climate change in central Inner Mongolia in the 1990s, the comfort of the temperature, humidity and wind efficiency changed towards warm.The comprehensive comfort of the human body is getting better and better, which is suitable to live, travel and take summer vacation.Temperature and wind speed are the key meteorological factors to affect the climate comfort in the region, followed by sunshine.The number of comfortable and relatively comfortable days is less in the north and than in the south.As a whole, the number of comfortable days shows a fluctuating change.Compared with comfortable days, the number of relatively comfortable days continuously increases.Industrial production, human activities and the ecological environment affect the number of comfortable or relatively comfortable days.This study provides a scientific basis for the evaluation of the human settlement environment and summer tourism conditions, rational development of tourism resources, optimal development of future urban agglomerations, and the industrial expansion of urban construction and human activities.It provides theoretical support for the analysis of climate comfort change characteristics and key meteorological factors in a specific region. Figures and Tables | References | Related Articles | Metrics

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The spatio-temporal characteristics of the number of human comfortable days in Shaanxi province during 1971-2018 Yang-na LEI,Ming-ce MAO,Ming LI,Xia ZHANG 2022, 38 (2):  89-96.  doi: 10.3969/j.issn.1673-503X.2022.02.011 Abstract ( 198 )   HTML ( 17 )   PDF (1216KB) ( 125 )   Save Based on the daily meteorological data from 94 stations in Shaanxi province from 1971 to 2018, the temporal and spatial characteristics of the number of human comfortable days (HCDs) were analyzed using the analytical methods including linear tendency rate, cumulative anomaly, wavelet analysis, and empirical orthogonal function (EOF) analysis.The results indicated that the body feeling status ranges from cold to comfort in most time with the number of days accounting for 85.2 percent of the year.There is a small number of days when the body feels warm and there are no hot and sultry days.The annual mean number of HCDs is 132 d in Shaanxi province from 1971 to 2018 with an increasing linear trend of 0.524 d·a-1.The number of HCDs in spring and summer increases most significantly.There are two periodic oscillations of quasi 4 years and quasi 8 years for the number of HCDs during the studied period.The results of the sliding-T test show that the number of HCDs in Shaanxi province and the three regions occurs significantly abrupt change over 1997.HCDs appear from March to November, and focus mainly on the period from May to September.There is the largest number of HCDs in northern Shaanxi province from July to August, in Guanzhong from June to August, and in southern Shaanxi province from June to September.The number of annual HCDs is larger in the south than in the north, and is the largest in Hanzhong and Ankang.The EOF analysis results show that the abnormal distribution of annual HCDs is consistent across the province.The spatial distribution of the trend displays that the number of HCDs increases in 80% of regions of the province, but decreases in only 11 districts including north Yulin, north Yan'an, and east Ankang.The number of human uncomfortable days in the province shows a significant decreasing trend with a tendency rate of -0.548 d·a-1, and the number of cold uncomfortable days decreases significantly.In addition, the discomfort of the human body in Shaanxi province is mainly manifested as cold discomfort which appears mainly in the northwest of northern Shaanxi province, the southern mountainous areas, and the high mountainous areas of Taibai and Huashan in Guanzhong.However, the region of human thermal discomfort is mainly distributed in Hanzhong and Ankang areas in southern Shaanxi province and Xi'an in Guanzhong, and the number of days is small. Figures and Tables | References | Related Articles | Metrics

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Automatic observation of frozen soil and its time consistency detection of minute data in Liaoning provice and Inner Mongolia Autonomous region in 2019 Zhi-gang LIU,Dong-li WU,Chang-liang SHAO,Li-xia WU,Shu-zhen HU,Shu-li SONG 2022, 38 (2):  97-104.  doi: 10.3969/j.issn.1673-503X.2022.02.012 Abstract ( 115 )   HTML ( 9 )   PDF (663KB) ( 111 )   Save Five types of frozen soil automatic observational instruments were installed for field experiment at Kazuo station, Liaoyang station in Liaoning province and Manzhouli station in Inner Mongolia Autonomous region.The minute frozen soil data were collected from March to June 2019.These dataset were processed with the control of the time consistency and quality adopting the vertical and horizontal extreme value set method and compared with the manual timing data of the three stations.According to the manual observation data in the same period, the thresholds of abnormal suspicious data and abnormal data of automatic observation of frozen soil were recognized as 5 cm and 11 cm respectively, and the verification was carried out accordingly.The results show that the integrity rate of minute data of frozen soil automatic observation instrument is 99.59%.The average number of frozen soil layers observed with the automatic instrument is consistent with the manual observation, which is in line with the distribution characteristics of frozen soil data applied in business.The five types of frozen soil automatic observation instruments can better reflect the minute changes of frozen soil data in different climatic regions, and the quality control threshold of minute data from frozen soil automatic observation is reasonable and reliable. Figures and Tables | References | Related Articles | Metrics

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Study on automatic recognition of root system image of spring maize in situ Qing-yu JIA,Yan-bing XIE,Yi-jun ZHAO,Rong WANG,Jing-miao LIU,Ri-hong WEN 2022, 38 (2):  105-111.  doi: 10.3969/j.issn.1673-503X.2022.02.013 Abstract ( 139 )   HTML ( 11 )   PDF (1586KB) ( 50 )   Save Minirhizotron technology promotes the study of root phenotype, but the root length and diameter still require human eye recognition to draw the track, which consumes a lot of manpower and time.This study introduced U-Net semantic segmentation technology into plant root image recognition, and developed iRoot-V02 software based on machine learning to solve this problem.The iRoot-V02 software was used to identify the root length, diameter, projection area, and root tip number from plant root imaging images obtained by Minirhizotron technology.The results show that the average speed of iRoot-V02 software for processing 600 dpi images in batches is 26.6 seconds per picture.The skeleton information and total length of roots are essentially consistent with the human eye recognition results.According to the diameter of each 0.1 mm as a level, the correlation coefficient between the obtained root length of different diameters and the eye recognition results is larger than 0.76, reflecting that the software accurately captures the changes of root lengths of different diameters in the vigorous growth period of maize.In addition, the analysis of the parameters of root images with 300 dpi and 600 dpi resolutions shows that their results are highly correlated.Therefore, the relationship equation between low-and high-resolution root parameters can be established to confirm more accurate root parameters with the low-resolution root image and to reduce the workload.Root growth information obtained by using iRoot-V02 software is similar to that of human eye recognition.On a whole, compared with human eye recognition, iRoot-V02 has great advantages in mass root image intelligent recognition, automation and fast target detection. Figures and Tables | References | Related Articles | Metrics