ISSN 1000-0526
CN 11-2282/P

Volume 45,Issue 5,2019 Table of Contents

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  • 1  Improving the Meiyu Simulation Using Spectral Nudging of SingleElement and MultiElement in HighResolution Regional Numerical Model
    DONG Meiying CHEN Feng JI Chunxiao
    2019, 45(5):593-605. DOI: 10.7519/j.issn.1000-0526.2019.05.001
    [Abstract](1043) [HTML](201) [PDF 2.83 M](1168)
    This paper reviews the development of the technology for seamless fine gridded weather forecasting in China since 2014. And the key technical difficulties in the future development are analyzed. It is pointed out that the high spatiotemporal resolution observations capturing the fine structure of weather systems, the analysis products by multisource data fusion, the realtime rapid updating assimilation and prediction system, the high resolution regional model providing shorttime and shortterm weather prediction, the global numerical forecast model providing 10 days’ weather forecasting, and the oceanatmosphere coupled ensemble prediction system providing 46 days’ weather prediction, have jointly established the premise and foundation of the seamless gridded weather forecasts. After nearly 5 years’ exploration and constant efforts, the technology system of seamless fine gridded forecasting with different temporal resolutions has been established. The highfrequency lagrangian extrapolation skills are used for 0-4 h forecasting based on GRAPESMeso model forecast products and radar data over China. For the 4 h to 30 d leadtime forecasting, it mainly depends on the downscaling, error correction, model output statistics and postprocessing methodologies based on regional and global models of different spatiotemporal resolutions to improve forecast skills and resolution. At the same time, automatic and intelligent interactive forecasting platform is developed to meet the demand of combining efficient objective forecasting with forecasters’ subjective intelligence. In order to assess and track the performance of high resolution gridded forecasting, a spatial analysis verification method based on gridded observation data is developed. It is also stressed that the future gridded forecasting technology system should be able to reflect the latest technology development including the artificial intelligence application, more advanced statistical postprocessing skills, key technics for consistency forecasting and unified complete technical architecture and standards.
    2  Comparative Study of the Cause of Rainfall and Its Forecast Biases of Two Cold Vortex Rainfall Events in North China
    FU Jiaolan CHEN Shuang SHEN Xiaolin ZHANG Xidi QUAN Wanqing
    2019, 45(5):606-620. DOI: 10.7519/j.issn.1000-0526.2019.05.002
    [Abstract](942) [HTML](292) [PDF 82.55 M](1922)
    By using the conventional observation, and the radiosonde, satellite, radar, wind profile, NCEPFNL analysis data as well as the data of three deterministic global forecast systems, causes of rainfall and forecast biases of two cold vortex rainfall events in 2017 over North China are comparatively studied. The results show that the event that occurred on 22 June 2017 is characterized by persistent and steady rainfall with weak rainfall intensity and lower convective height. The rainfall echo is of convectivestratiform mixed type. However, the rainfall on 6 July is shorttime severe rainfall and the height of convective echo top is very high. The background conditions are quite different between these two cases. For the 22 June event, cold vortex is at its mature stage and subtropical high is far south. Moreover, a warm section convection occurred on the previous day, and its cold pool is quite strong, leading to the release of convective energy, thus the convective energy and water vapor are normal for the first case. Comparatively, for the second case the cold vortex is at its developing phase and subtropical high is located more northward.By using the conventional observation, and the radiosonde, satellite, radar, wind profile, NCEPFNL analysis data as well as the data of three deterministic global forecast systems, causes of rainfall and forecast biases of two cold vortex rainfall events in 2017 over North China are comparatively studied. The results show that the event that occurred on 22 June 2017 is characterized by persistent and steady rainfall with weak rainfall intensity and lower convective height. The rainfall echo is of convectivestratiform mixed type. However, the rainfall on 6 July is shorttime severe rainfall and the height of convective echo top is very high. The background conditions are quite different between these two cases. For the 22 June event, cold vortex is at its mature stage and subtropical high is far south. Moreover, a warm section convection occurred on the previous day, and its cold pool is quite strong, leading to the release of convective energy, thus the convective energy and water vapor are normal for the first case. Comparatively, for the second case the cold vortex is at its developing phase and subtropical high is located more northward.
    3  Cause Analysis of Different Types of Severe Convective Weather Under Cold Vortex Background
    CAI Xuewei CHEN Yun SHEN Xinyong ZHENG Yongguang TAO Yiwei
    2019, 45(5):621-631. DOI: 10.7519/j.issn.1000-0526.2019.05.003
    [Abstract](1013) [HTML](392) [PDF 7.32 M](1453)
    Using conventional meteorological data, automatic weather station data, satellite data, radar data and NCEP reanalysis data, and focusing on the different types of severe convective weather that occurred in the northeast of North China and Huanghuai Region in the background of cold vortex on 22 August 2015, the evolution process of two mesoscale convective systems caused by different weathers and reasons of different severe convective weather with cold vortex are analyzed in this paper. The results show that: (1) With same cold vortex, Northeast of North China is located in southwest quadrant of cold vortex and in front of ground cold high pressure. Dispersive multicell storm lies in vortex cloud at the periphery of 〖JP2〗cold vortex, leading to 〖JP〗severe convective weather dominated by shortterm heavy rainfall. Huanghuai Region is in the rear of cold vortex and ahead of cold front on ground. Multiple convective cells form in clear sky behind the trough, forming a herringbone squall line which leads to heavy rainfall, thunderstorm and hail. (2) The differences of environmental heat and water vapor provide a condition for the formation of different severe convective weathers. The northeast of North China is affected by highlevel warm ridge, and eastward airflow at the back of ground high pressure brings water vapor. The whole layer in warm and humid conditions is conducive to generating intense precipitation. The upper air over Huanghuai Region gets supplementary dry and cold air, which benefits the development of thermal instability. However, the lowlevel water vapor in the region is not enough, so strong wind and hail are not easily triggered in the dry environment. (3) The convection triggering mechanisms for different severe convections are different. Both initial convections are triggered along the same ground convergence line, but with the terrain lifting, new cells are continuously generated in northeast of North China. After initial local geothermal convection in Huanghuai Region is formed, the divergent outflow at leading edge forms a new convergence with ambient wind, causing the original convergence line to break and turn. (4) When there are different severe convections, the vertical wind shear in the mid level of severe convection over Huanghuai is significant, which is helpful for the formation of a persistent severe storm. When severe convective weather occurs, the evolution of middle and lower winds in northeast of North China is related to the change of synoptic scale systems. The vertical distribution of middle and lower winds in Huanghuai Region is related to the occurrence and development of mesoscale convective system.
    4  Characteristics of ShortTime Heavy Rainfall in Hedong Area of Gansu Based on CopulaFunction
    YANG Yin LI Yanying CHEN Yuying CHEN Ziyan LIU Rong
    2019, 45(5):632-640. DOI: 10.7519/j.issn.1000-0526.2019.05.004
    [Abstract](974) [HTML](196) [PDF 2.17 M](1153)
    Based on minutely precipitation collected from Lanzhou, Linxia, Hezuo, Dingxi, Wudu, Tianshui, Pingliang and Xifeng weather stations in Hedong Area of Gansu Province during 1960-2014, the spatiotemporal distribution characteristics of heavy rainfall frequencies are analyzed. Besides, the risk analysis on duration and accumulated precipitation is obtained by Copula function based 〖JP2〗on a bivariate Copu〖JP〗la distribution model for heavy rainfall variables. The results show that: (1) The main characteristics of heavy rainfall in Hedong Area during recent 55 years are short duration and low accumulated precipitation. The occurring frequency is 1.64 time/(a?station), average duration is 2.88 h, average accumulated precipitation is about 23.4 mm and the probability of duration less than 1 h is up to 13.4%. (2) Heavy rainfall occurs mainly from April to September, and the monthly variation is in the normal distribution. The Mexico Hat wavelet analysis shows that there are obviously interdecadal changes of 22-23 years and 13-15 years, and interannual changes 3-7 years in the heavy rainfall. (3) The frequency of heavy rainfall from large to small is Pingliang, Xifeng, Tianshui, Dingxi, Wudu, Linxia, Lanzhou and Hezuo in order. Correspondingly, the maximum frequency occurrs in eastern Gansu, second in southern Gansu, and the smallest central Gansu.
    5  Simulation of Wire Ice Thickness During a Freezing Rain Process in Henan Province
    DU Shuang ZHOU Ning HAN Yongxiang LI Zhe LU Zhengqi GONG Jianfu LIU Weijia
    2019, 45(5):641-650. DOI: 10.7519/j.issn.1000-0526.2019.05.005
    [Abstract](881) [HTML](322) [PDF 4.37 M](1170)
    The atmospheric circulation analysis and ice thickness simulation are conducted to the freezing rain process in Henan Province in 8-11 February 2010 by using the Weather Research and Forecasting (WRF) mesoscale numerical model coupled with the Jones ice thickness model. The results show that: (1) The emergence of an intense inversion layer and the mixing of cold and warm air masses above Henan and northern Anhui reached the freezing weather conditions. (2) The simulated precipitation and 10 m wind direction and wind speed were similar to the observed values, but the intensity of the simulated precipitation center was slightly larger. (3) The simulated wire ice accretion appeared and developed rapidly when the surface temperature went below 0℃. In the icing growth and maintenance phase, the vertical temperature and hydrate simulation results show that the height and low altitude configuration is consistent with the change trend of ice thickness. Ice accretion first appeared to the north of Funiu Mountain, and then extended to the southeast. The evolution of the simulated ice range and the thickness of the wire ice accretion generally coincided with the observed data, which proves that this model can be applied to the prediction of ice accumulation in Henan Province. (4) The simulated ice thickness was too large in some areas, which might be attributed to many reasons, for example, as simulation demands highly accurate terrain data, the simulated wind speed is too large, the angle between the wind direction and the electric wire is ideally assumed, and the threshold range of the Jones ice model is narrowed. Although the WRF model of ice thickness has some capability in the simulation of wire ice accretion, it still needs further improvement.
    6  Study on the Combined Model of Forecasting the Days of Sand Dust Weather Based on Wavelet Decomposition—Taking the Time Series of Dust Weather in the Transitional Zone of Qira Desert Oasis During 2008-2016 as an Example
    PANG Jinfeng LIU Bo ZHANG Bo ZHANG Pengpeng WANG Bo ZENG Fanjiang
    2019, 45(5):651-658. DOI: 10.7519/j.issn.1000-0526.2019.05.006
    [Abstract](710) [HTML](168) [PDF 780.54 K](937)
    The area of southern Xinjiang is a high occurrence area of dust weather, which has a serious impact on local residents’ life. To reveal the characteristics of local windsand weather variation and predict future trends, a wavelet decomposition method is used to decompose the time series of dust weather in the southern edge of the Taklimakan Desert from 2008 to 2016 into stationary fluctuation terms and nonlinear trend terms, according to the characteristics of the data. The autoregressive (AR) model and the least square support vector machine (LSSVM) are selected to predict the variation trend. Finally, the time series prediction of the number of dust weather days is achieved by the addition principle reconstruction. The results show that the dust weather is a typical spring and summer type, mainly concentrated in the period from March to September, and the peak value appears in May. The predicted value of the combined model is basically consistent with the measured value, and has a higher prediction accuracy (absolute error is 4 d, root mean square error is 3.764 d). Compared with the prediction results of AR model and LSSVM, the correlation coefficient of combined model increases 0.12 and 0.31 respectively), and has a better application prospect. Thus, it could provide scientific basis for preventing wind and sand disaster and guiding actual production and life in the research area.
    7  Analysis of Heavy Fog SpatioTemporal Distribution and Meteorological Element Evolution in Guizhou from 2016 to 2017
    HU Yuewen QIN Jie SU Jingwen NIU Diyu JI Tingyan
    2019, 45(5):659-666. DOI: 10.7519/j.issn.1000-0526.2019.05.007
    [Abstract](831) [HTML](920) [PDF 1.26 M](1327)
    The hourly observation data of automatic station in Guizhou Province from 2016 to 2017 were used to analyze the spatiotemporal distribution characteristics of heavy fog. Meanwhile, 31 days of front fog and 17 days of radiation fog were screened out via analyzing the synoptic data, and the evolution characteristics of meteorological elements such as wind, temperature and humidity were compared and analyzed. The results are as follows. (1) Heavy fog happens frequently in late autumn and early spring in Guizhou. The occurrence time period of the highest frequency is from 02:00 to 09:00 BT, reaching the peak at 07:00 BT. (2) The southwest, central, eastern and northern parts of Guizhou are the foggy areas from west to east. (3) Frontal fog mainly appears in the central and western Guizhou. The most extensive range covers about 20 county stations, and the duration can be 10-13 h. Some single station can have fog more than 60 h. Radiation fog mainly appears in the central and eastern Guizhou. The widest range can be close to 40 county stations, far more than the frontal fog range, and the duration is relatively short. (4) The 10 min average wind speed is 0-3 m?s-1, the relative humidity is 97%-100%, and the difference between temperature and dew point is 0-0.5℃. Temperature is in a state of decline at the beginning or before the formation of fog. In the period of extinction, warming is more obvious. The difference in temperature between surface and atmosphere presents a trend from negative to positive or from low to high, which reflects the process in which the nearsurface atmosphere changes from a more stable inversion temperature environment to an unstable environment. The early cooling and later heating up are not obvious in frontal fog, also the temperature has no regular distribution between ground surface and atmosphere, only some cases are in line with frontal fog.
    8  Impact of Temperature Factors on Full Bloom Stage of Rape Petal
    ZHANG Zhiwei GAO Ping WANG Hongbin AI Wenwen SUN Jiaqing BAO Jing XU Min
    2019, 45(5):667-675. DOI: 10.7519/j.issn.1000-0526.2019.05.008
    [Abstract](672) [HTML](410) [PDF 979.40 K](1157)
    Temperature is one of most important climatic factors in the plant flowering time. Using phenology observed data of rape petal in Gaochun from 1986 to 2016, this paper analyzes the characteristics of fullbloom stage and temperature factors in different years. Path analysis method is used to analyze the effect of three temperature factors on fullbloom stage of rape petal. The three factors are days of mean air temperature lower than 5℃, accumulated temperature of mean air temperature lower than 5℃, and days with strong cold air. The results could provide theoretical foundation for the predicting of optimum viewing period and tourism meteorological services of rape petal in Gaochun. Finally, the results show that there is no fluctuation of fullbloom stage before 2001. However, along with the decadal variation, it shows an early trend obriously. The type of fullbloom stage changes with the average temperature stabilized at 5°C. Specifically, the early years of fullbloom stage are less than normal early years and normallate years, less than normal years, and less than later years. There is a significant correlation between fullbloom stage in late years and days of mean air temperature lower than 5℃ (Ta<5℃). Beginning from the winter solstice, the fullbloom stage of rape petal next year would be later than April 4 if the Ta<5℃ days are more than 53 d, or accumulated temperature of mean air temperature lower than 5℃ (Ta<5℃) is more than 137℃?d. Then, rape fullbloom stage next year would be pushed back with the more days reaching level of strong cold air. With three indice of low temperature, the largest factor impact on rape petal fullbloom stage is the accumulated temperature of mean air temperature lower than 5℃ (Ta<5℃).
    9  Correction Technology of Regional Wind Speed Forecasting Based on Partial Least Square Regression
    YANG Cheng JIANG Yujun YU Zhenshou JIANG Wendong KANG Lili WANG Liji
    2019, 45(5):676-684. DOI: 10.7519/j.issn.1000-0526.2019.05.009
    [Abstract](920) [HTML](156) [PDF 4.06 M](1005)
    Based on the partial least square regression, the nearsurface wind speed predicted by Zhejiang WRF ADAS Real Time Modeling System in winters of 2013-2016 is corrected and evaluated. The forecast product is used as the independent variable while the corresponding observational data of the automatic weather stations are used as the dependent variable. At most of the 956 stations, the correction of wind speed has been improved. Through quantitative analysis, we find that the improvement effect is best for the stations in the western region of Zhejiang, up to 91.7%. The improved stations in the central part account for 86.5%. The improvement of the stations in the eastern coastal region is slightly worse, with 67% obviously improved stations. The improvement percentage of wind speed correction, indicates the station performance of each city is good. Except for Zhoushan (49.9%), the rate of wind speed improvement is more than 50% in other cities. Based on the analysis of the gale process in the northeastern coast Zhejiang on 20 January 2017, the corrected wind speed is closer to the observation, especially at the nearshore stations.
    10  Comparative Analysis of Several Drought Indices to Use in Fujian Province
    ZUO Bingjie SUN Yujun
    2019, 45(5):685-694. DOI: 10.7519/j.issn.1000-0526.2019.05.010
    [Abstract](612) [HTML](323) [PDF 1.34 M](1270)
    Using reasonable drought index to monitor drought has always been one of the difficulties in drought research. The study of the applicability of different indices can provide a certain reference for drought monitoring. Based on the daily meteorological observation data of the Fujian provincial meteorological stations during 1960-2017, we compare the applicability of the percentage of precipitation anomalies (Pa), the standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI), relative humidity index (MI) and improved comprehensive meteorological drought index (CInew) in Fujian Province with 120 typical historical drought events. Besides, we correct the thresholds of the five drought indices by using the frequency accumulation method and also calculate weights of drought events at different levels by Analytic Hierarchy Process. The results show that: CInew is suitable for the monitoring of the spring, autumn, winter and annual droughts and MI is suitable for the monitoring of the summer, autumn and winter droughts. The two indices have better monitoring effect on severe drought and specially severe drought events. SPI and SPEI are suitable for moderate drought and light drought events. All the five indices can describe the development process of drought events. CInew’s monitoring results are more close to reality and more consistent with the mechanism of drought. Therefore, CInew is more suitable for drought monitoring in Fujian Province, followed by MI.
    11  Analysis of SpatioTemporal Distribution and Connecting Factors of Air Pollution in Beijing, Tianjin, Shijiazhuang and Zhengzhou in Winter of 2016
    JIANG Qi WANG Fei ZHANG Hengde Lv Mengyao HE Jiabao
    2019, 45(5):695-704. DOI: 10.7519/j.issn.1000-0526.2019.05.011
    [Abstract](526) [HTML](218) [PDF 2.86 M](1084)
    Based on the observations of PM2.5 mass concentration, reactive gases and related meteorological elements in Beijing, Tianjin, Shijiazhuang and Zhengzhou from December 2016 to February 2017, the physical and chemical characteristics of the air pollution, transmission and elimination rules are discussed. The results show that the frequency distributions of PM2.5 mass concentration in Beijing, Shijiazhuang, Tianjin and Zhengzhou all had two obvious peaks. The mean values of PM2.5 concentrations were 10.1, 19.2, 40.0 and 47.1 μg?m-3 in the four regions respectively at the time with the highest PM2.5 frequency distribution. The degree of air oxidation in Beijing was the lowest followed by Shijiazhuang, Tianjin and Zhengzhou in order. Traffic sources had important contribution to the environmental air pollution in the four study areas. The correlation between CO and PM2.5 at low relative humidity was higher than that with high humidity. However, the correlation between NO2 and PM2.5 at low relative humidity was lower than that with high humidity. With the wind speed increasing, the PM2.5 mass concentration decreased rapidly and then tended to be gentle, of which the wind speed threshold was 3 m?s-1 in Beijing, Shijia zhuang and Zhengzhou, and for Tianjin it was 4 m?s-1. Affected by upstream pollution transport, southerly wind transport effect was about 20-30 h later than reaching the maximum and the effect of the northerly wind delayed 8-12 h before reaching the maximum.
    12  Benefit Assessment of Geological Hazard Meteorological Services Based on Inverse Algorithm and Evaluation Method of Delphi
    DI Jingyue XU Hui XU Fengwen YANG Yin BAO Hongjun ZHANG Guoping
    2019, 45(5):705-712. DOI: 10.7519/j.issn.1000-0526.2019.05.012
    [Abstract](588) [HTML](136) [PDF 1.30 M](1079)
    Serious harm was caused by geological disasters induced by precipitation, and people’s lives and property were threatened. The assessing of meteorological services and disaster 〖JP2〗mitigation effect in geological〖JP〗 disaster is needed. Based on the disaster and direct economic losses and the weather forecast data from 2009 to 2016, the relationship between the disaster losses and meteorological service benefits is analyzed in the paper. By the inverse algorithm and the Delphi method, the assessing model is established in this paper. The parameterization entering into the model is successful. The input variables are accuracy as geological disaster weather forecast and the direct economic losses, the output are disaster prevention and mitigation benefit value and meteorological service direct economic benefits. The model was adopted to describe the capacity of disaster prevention and mitigation and meteorological service’s level and performed well in geological hazard meteorological benefit assessment in 2017.
    13  Characteristic Analysis of Hail Cloud Doppler Radar Parameters in the Eastern Hebei Province
    WANG Sha SHA Yong SONG Jinme PEI Yujie WU Linlin
    2019, 45(5):713-722. DOI: 10.7519/j.issn.1000-0526.2019.05.013
    [Abstract](758) [HTML](216) [PDF 849.04 K](1320)
    Various parameters are inversed when hail occurred by using Qinhuangdao Doppler weather radar data, and the relationship between various parameters and occurrence of hailstorms is extracted with 36 hailstorm cases during 2008-2015 in the eastern Hebei Province. The study results show that the averages of maximum radar base reflectivity (MaxREF), top of the storm (TOP) and vertically integrated liquid (VIL) are 62 dBz, 9.9 km and 51.6 kg?m-2 respectively when hails occur. The average storm thickness above 0℃ level layer is 5.8 km, the average thickness between 0℃ level layer and -20℃ level layer is 3.1 km, MaxREF height of the storm is 4.6 km, and the average storm moving speed is 9 m?s-1. The radar parameters corresponding to different sizes of hailstones do not change significantly. During the occurrence of hail, suddenincrease phenomenon for MaxREF between the two volume scan is 7 dBz on average, suddenincrease phenomenon for TOP between the two volumn scans is 6.7 km on average and suddenincrease phenomenon for VIL between the two volumn scans is 17 kg?m-2 on average. This transition occurred 39, 30 and 25 min earlier than the average time of hailstorm occurrence. Such sepcical phenonmenon could be an important criterion for hail warning. In addition, the WSR88D hail algorithm HI is evaluated. The results show that probability of detection and false acceptance rate of the hail algorithm are relatively higher. The forecasting rate of hail by the algorithm is about 43 min on average, and the hail forecast results are larger.
    14  Assessment of Impacts of XBand Weather Radar Electromagnetic Radiation on Environment
    WANG Hui LI Lin ZHENG Guofeng YANG Meilin LI Siteng MENG Qingchun WEI Tao TIAN Ye
    2019, 45(5):723-729. DOI: 10.7519/j.issn.1000-0526.2019.05.014
    [Abstract](641) [HTML](1254) [PDF 945.34 K](1187)
    In order to quantitatively analyze the effect of the electromagnetic radiation of Xband dualpolari zation radar on the environment, on the basis of the main performance parameters of Xband weather radar, we derive electromagnetic radiation characteristics of Xband weather radar, and analyze the surrounding environment of Xband radar station. The electromagnetic radiation is monitored horizontally and vertically. The theoretical calculation and actual measurement results show that Xband radar electromagnetic radiation meets the requirements of the “Controlling Limits for Electromagnetic Environment” (GB8702-2014) and the “Guidline on Management of Radioactive Environmental Protection Electromagnetic Radiation Monitoring Instruments and Methods” (HJ/T10.2-1996). The electromagnetic radiation level is lower than the public exposure control limit value.
    15  Application Evaluation of Precipitation Phenomenon Instrument Observation
    DU Chuanyao YIN Jiali LI Lin WU Yongxue Jiang Tao
    2019, 45(5):730-737. DOI: 10.7519/j.issn.1000-0526.2019.05.015
    [Abstract](686) [HTML](246) [PDF 3.02 M](1047)
    In this paper, data acquired by artificial observation and precipitation phenomena observation instruments at 20 observation stations of Beijing from September 2017 to Augusta 2018 are used to compare and assess the precipitation phenomena observation instruments. The results show that the lack of measurement rate of precipitation phenomenon instrument is 0.01%, false prediction rate is 0.6%, the capture rate is 93.5%, the missing report rate is 27.9%, and misreporting rate is 10.0%. From the above statistical parameters, we can see that the lack of measurement rate and false prediction rate of the instruments are low and precipitation phenomena capture rate is high, which shows the good performance of the instruments. The missing report rate and misreporting rate are high, indicating missing and misidentification casetend to happen frequently. Missing report mainly happens in the process of light precipitation and the misreporting mainly in the process of drizzle identification. The time consistency of distinguishing the beginning of precipitation processes is better, but poor at the ending time. The existing problems of the instruments are that raindrop overlap misidentification is easy to appear during heavy precipitation, and the identification rate is reduced during light precipitation. The quality control process is lacking in the case of wrong outputs of precipitation when no precipitation is seen.
    16  Analysis of the February 2019 Atmospheric Circulation and Weather
    LI Xiaolan HE Lifu
    2019, 45(5):738-744. DOI: 10.7519/j.issn.1000-0526.2019.05.016
    [Abstract](879) [HTML](265) [PDF 22.17 M](1360)
    The main characteristics of the general atmospheric circulation in February 2019 are as follows. The polar vortex center in the Northern Hemisphere was stronger than normal and located by north in the Eastern Hemisphere. The circulation at middlehigh latitudes of Eurasia showed a fourwave pattern, and the degree of meridionality was lower than normal generally. The Western Pacific subtropical high was strong relatively, and the Bay of Bengal trough was weaker and more to the west than normal. Cold air processes attacked China twice in February, one nationalwide strong cold air process and one moderate cold air process. The monthly mean temperature was -1.3℃, higher than normal by 0.4℃. The temperature was abnormally high in Northeast China. The monthly mean precipitation amount was 23.2 mm, 33.3% higher than normal. Also, one persistent rainy weather event happened in southern China. Snowfall hit the Tibetan Plateau frequently, causing snow disaster in southeastern part of Qinghai Province. In addition, continues foghaze weather appeared in the central and eastern part of China in late February.

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