ISSN 1000-0526
CN 11-2282/P

Volume 45,Issue 10,2019 Table of Contents

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  • 1  A Case Study of Aircraft Icing Conditions in Anqing Area
    SUN Jing CAI Miao WANG Fei SHI Yueqin
    2019, 45(10):1341-1351. DOI: 10.7519/j.issn.1000-0526.2019.10.001
    [Abstract](1529) [HTML](271) [PDF 8.36 M](1092)
    Aircraft icing observation test was conducted in 8-9 March 2016 in Anqing Area of China. The icing conditions for the test are studied in this paper using observations of satellite, radar, soundings, aircraft, NCEP reanalysis data and simulations of the CPEFS model. The multi-scale structure about icing cloud is discussed and the results of several icing indexes are compared. The results show that large-scale weather system of the icing case was the cold wave on the surface. Strong cold air induced frontal temperature inversion. On the top of stratiform cloud after the convective rainfall, icing was detected by the aircraft. The height of the icing was under the layer of the front inversion. The cloud top height was about 3.4 km and the cloud top temperature was -10℃. There was no precipitation and radar reflectivity at this time. The cloud was composed of large number of supercooled water without ice particles. The average supercooled water during the icing time was 0.36 g·m-3. When the cloud top lifted again and ice particles increased to snow, the aircraft icing was not observed because of the poor supercooled water. The CIP initial icing potential results described this aircraft icing well. The cloud structure simulated by CPEFS model was basically consistant with observations.
    2  Comparative Analysis of Aircraft Icing Forecasting Algorithms and Research on Ensemble Prediction Model
    BIAN Shuangshuang HE Hongrang AN Hao PAN Xiaobin ZHANG Yun
    2019, 45(10):1352-1362. DOI: 10.7519/j.issn.1000-0526.2019.10.002
    [Abstract](627) [HTML](505) [PDF 1.15 M](1042)
    Based on the aircraft icing data which were obtained from the artificial rainfall enhancement, this paper uses the Weather Research and Forecasting Model to simulate 51 aircraft icing processes, contrasts and analyses the prediction results of icing potential area and intensity forecasted by seven kinds of commonly-used icing forecasting algorithms, then utilizes the score weight integration method to establish the ensemble forecasting model of aircraft icing intensity, and tests its forecasting effect. The results show that (1) in forecasting an icing case that occurred in 4 April 2002, the forecasting effect of the false frost point temperature empirical method is consistent with the actual condition but there are great differences between the effect forecasted by the other icing algorithms and the observed condition. (2) After the statistical test for the 51 aircraft icing forecast effects, the prediction effect of the false frost point temperature empirical method is the best, whose accurate rate of icing intensity forecast is up to 72.55%, followed by the RAOB method, IC index method and I icing index method, but that of improved IC index method is the poorest, only 19.61%. (3) By comparing the forecasting effects of the ensemble forecasting models established by different icing algorithms, we find that when using IC index method, the false frost point temperature empirical method, and RAOB method to forecast, the forecast accuracy rate is the highest, which is 8% higher than the best forecast accuracy by a single forecasting algorithm and the false negative rate, weak rate and strong rate can all be controlled within 10%, and the false negative rate is reduced by 4%, the strong rate is reduced by 8%.
    3  Formation Mechanism of an Infrequent Blizzard in Beijing in April
    DU Jia YANG Chengfang DAI Yi XING Nan YU Bo
    2019, 45(10):1363-1374. DOI: 10.7519/j.issn.1000-0526.2019.10.003
    [Abstract](1533) [HTML](331) [PDF 4.99 M](1097)
    During 4-5 April 2018, an infrequent snowstorm stuck Beijing. This paper analyzes the extremes and formation mechanism of the blizzard process by using multi-source observation data such as raindrop disdrometer, Doppler weather radar, microwave radiometer, ground encryption automatic station, EC reanalysis data and climate reorganization data. The results showed that (1) the 5th of April 2018 was the first pure snow day in Beijing in April. The snowfall and snow depth both exceeded the historical record and the 1000-850 hPa temperature normalized SD value was less than -3. So, it was an extreme weather process. (2) The invasion of low-level cold air forced the warm and humid air to climb along the cold pad. Conditional symmetric instability from 800 hPa to 500 hPa in Beijing Area was caused by strongly warming and humidification from 700 hPa strong southwest low-level jet and triggered by the strong ri-sing motion of warm air above the front, resulting in elevated convection and radar echo like thunderstorm cells in summer, which enhanced the snowfall. (3) The snowfall process was affected by two cold air superimposition successively. The continuous violent cooling induced by a strong cold air before the snowfall caused the low-level temperature to be extremely low and reached the temperature threshold of snow in Beijing, which was the decisive factor for the extreme snowfall. (4) Microwave radiometer monitoring showed that the duration of snowfall had a good correspondence with the temperature inversion, and the precipitation phase mainly depended on the temperature change below 1 km.
    4  Research on Storm Intensity Formula and Design Rain Pattern Sampling Method
    LIAO Daiqiang ZHU Haonan ZHOU Jie SUN Jia WANG Ying
    2019, 45(10):1375-1381. DOI: 10.7519/j.issn.1000-0526.2019.10.004
    [Abstract](882) [HTML](188) [PDF 676.03 K](886)
    A new sampling method for storm pattern samples: precipitation natural sliding sampling was designed in this paper. According to this sampling method which is used in the urban rainstorm intensity formula and the design technique for determining rainstorm pattern, the four sampling methods—return period sampling, annual maximum sampling, natural field sampling and precipitation natural sliding sampling, are analyzed and compared by using the minute precipitation data at the Shapingba National Basic Station of Chongqing from 1961 to 2016. The results showed that precipitation natural sliding sampling has the advantages of simple flow and higher sample representation. This method can provide a new reference for formulating rainstorm intensity formula and designing rain pattern sampling in future.
    5  Application of Precipitation Extreme Forecast Index from ECMWF in Typhoon Rainstorm in East China
    LUO Ling LOU Xiaofen FU Liang QIAN Hao
    2019, 45(10):1382-1391. DOI: 10.7519/j.issn.1000-0526.2019.10.005
    [Abstract](1049) [HTML](191) [PDF 12.10 M](1314)
    The typhoon heavy rainfall can easily induce an extreme weather event, and it is difficult to predict. In this study, we investigate the statistical relationship between the precipitation extreme forecast index (EFI) from ECMWF ensemble forecast system and the observed typhoon heavy rainfall with 13 typhoons that affected East China during 2013-2017. The results show that the EFI is a good indicator to predict the typhoon rainfall. Different EFI thresholds should be used as the reference for precipitation of rainstorm area. Overall, the possibility of heavy rainfall occurrence increases with the increase of EFI. The threshold of EFI gradually decreases when the forecast lead time increases. With the criteria of TS maximization, the EFI thresholds for different lead times and different storm levels are estimated in East China. Higher TS scores and reasonable BS scores are obtained when the thresholds are 0.7/0.8, 0.7, 0.6, 0.5 for rainstorm precipitation with lead time of 24, 48, 72, 96 h, respectively. Therefore, they can be used as EFI thresholds for different lead times. Significant positive correlation is found between the EFI and the climatic percentile of precipitation. The larger precipitation percentile appears when the EFI increases. When the EFI is prominently large, the typhoon rainfall can be estimated with the corresponding climatic percentile of observed rainfall. The EFI is a good indicator for extreme rainfall, and can predict the situation 3-5 days in advance.
    6  Analysis of Moisture Source and Transport Pathways of a Rainstorm with Tropical Cyclone in Nanchang
    XU Bin XIONG Qiufen ZHANG Yuting
    2019, 45(10):1392-1401. DOI: 10.7519/j.issn.1000-0526.2019.10.006
    [Abstract](736) [HTML](315) [PDF 3.61 M](982)
    Analysis of the rainstorm on 22 June 2015 in Nanchang was carried out using conventional observations. Backward trajectories up to 240 h were simulated and studied based on the HYSPLIT model and the NCEP 6 h 1°×1° reanalysis data. Cluster analysis of mid-low level trajectories was performed to analyze the change of moisture content of air parcels. The results showed that (1) the rainstorm developed ahead of the 500 hPa trough and the northwestern periphery of subtropical high. Tropical cyclone “Kujira” in the South China Sea also induced low-pressure systems, shear lines, low-level jets in the mid-low levels and divergence at 200 hPa. The rainstorm was located near a cold front with little potential instability and weak vertical wind shear. (2) In general, six major paths of moisture transport were found by clustering. Water vapor mainly came from the western part of Western North Pacific (46.7% of 180 backward trajectories) above 1500 m, followed by the eastern part of the South China Sea (24.4%) below 3000 m. 11.7% of the trajectories were originated from the east of the Bay of Bengal, the south of Indochina Peninsula and the south of Yunnan Province of China, and the remaining three clusters constituted less than 9%. (3) Air parcels from the two major clusters were observed to have higher moisture content as they were close to the surface over their maritime origins, which made the air parcels still have high specific humidity and relative humidity when they reached Nanchang, thus contributing greatly to the rainstorm. Air parcel that ended up in Nanchang over 3000 m and came from the Western North Pacific was originally dry in nature, but it became much more humid after it subsided and picked up moisture. With steady subtropical high and a tropical cyclone in the South China Sea just south of the subtropical high, moisture brought along by the easterlies or southeasterlies at the periphery of the high was an essential ingredient of rainstorms in the northern part of Jiangnan Region.
    7  Numerical Simulation of Typhoon Merbok Effect on Rainstorm During Meiyu Period
    CHEN Youli QIAN Yanzhen DUAN Jingjing XU Difeng GUO Jianmin
    2019, 45(10):1402-1414. DOI: 10.7519/j.issn.1000-0526.2019.10.007
    [Abstract](588) [HTML](184) [PDF 8.93 M](830)
    Based on the dense observation data, satellite images and reanalysis data, the reasons of Meiyu heavy rainfall in Zhejiang on 13 June 2017 are analyzed. The results show that low-level easterly and southwest winds could bring significant water vapor and energy, and Typhoon Merbok had an important role on the southwest air transport. The non-hydrostatic WRF V3.6.1 model was used to simulate heavy rainfall at high resolution with two nests. The sensitivity experiments show that Typhoon Merbok can enhanced south wind transport to Zhejiang, making the northeastern and southeastern flows meet in Zhejiang. The gradient of the north and south winds increased obviously, which made convergence streng-thened obviously. Meantime, “Merbok” enhanced the water vapor transport. A convergence in the left side of the mid-low-level southwest wind was accompanied by a divergence on the right side of the upper-level jet. This was conducive to the occurrence of vertical motion, promoting the increase of rainstorm. Sensitivity experiments show that the stronger the typhoon, the more water vapor transport in southwest flow, the stronger convergence, the more conducive to the development of vertical motion and convection, and the heavier the precipitation.
    8  Study of Macro and Micro Properties of Cloud and Precipitation Caused by Tibetan Plateau Vortex Based on Radar Observations
    LI Xiaoyang ZHENG Jiafeng ZHU Keyun ZHANG Jie WANG Yuqi
    2019, 45(10):1415-1425. DOI: 10.7519/j.issn.1000-0526.2019.10.008
    [Abstract](796) [HTML](205) [PDF 3.48 M](880)
    In order to enhance the understanding of the macro and micro physical structures and characteristics of cloud-precipitation under the plateau vortex, conventional weather data, combined with the data of millimeter-wave cloud radar and rain droplet disdrometer from TDPEX-Ⅲ were used in this paper for comprehensive analysis of a plateau vortex weather which affected the Nagqu Region, including weather background, horizontal and vertical structures of cloud-precipitation and evolution characteristics. The conclusions are as follows. The vortex cloud system formed under the plateau vortex and this process evolved from convective clouds to cumulostratus mixed clouds. In the stage of convective clouds, echoes mostly distributed sparsely with small area and short duration, accompanied by strong ascending motion. The positive velocity zone in the cloud was mostly strips or thin strips, and the convective clouds had higher cloud top, which was “mushroom-shaped”. The rain intensity was weak and the concentration of droplet particles was low. In the stage of mixed clouds, the echoes were mostly in the form of regular patches with larger area and durations were longer. The positive velocity zone in the cloud were often columnar or block-shaped. Near the surface, bright bands were obvious, caused by the phase change of the particles. Due to the collision of the precipitation particles, the reflectivity factor below the bright band was significantly reduced. Droplets were mostly in the size of 1-3 mm with larger concentrations. Thus, there are obvious differences of radar echoes and precipitation features between different stages under the process of plateau vortex, and the finding might provide some references for the research of plateau weather forecasting and physical processes.
    9  Impact of Cold Pool on Mesoscale Convective System for Extreme Rainfall over Xinxiang on 9 July 2016
    XU Shu DONG Gaohong XIONG Mingming
    2019, 45(10):1426-1438. DOI: 10.7519/j.issn.1000-0526.2019.10.009
    [Abstract](874) [HTML](243) [PDF 6.16 M](1341)
    Based on a variety of NCEP reanalysis data, conventional weather data, temperature of black bold (TBB) data from FY-2E satellite, Doppler radar products and densely observed data from automatic surface weather observation system, the mesoscale characteristics of the torrential rain process that occurred over Xinxiang on 9 July 2016 are analyzed. Furthermore, the formation mechanism of the cold pool is revealed and its impact on mesoscale convective system (MCS) produced extreme rainfall is studied. The results show that: the back-building-quasi-stationary and vortex-shaped MCS, with low-qualify core structure, led to the extreme severe rain over Xinxiang. The cold pool outflow, caused by stratiform precipitation and convective precipitation, led to the surface convergence, and furthermore, the surface convergence triggered and intensified the convection. MCS obtained unstable energy from the dense zone of surface potential pseudo-equivalent temperature formed by cold pool flow and ambient wind. The cold pool outflow and ambient wind were similar in strength, resulting in a stable dense zone of surface potential pseudo-equivalent temperature. For the frontogenetic function, the warm and moist air was lifted to the point of saturation, and upstream reignited deep convection in the south of the cold pool. Such backward propagation decreased the moving speed of MCS, and even made it into a quasistatic state. Under the effect of surface mesoscale vortex system, new convective cells organically rotated like vortex, and repeatedly passed Xinxiang, bringing continuous heavy rain to Xinxiang. The moist cold pool was an important source for the surface water vapor. The Taihang Mountain was thought to trap the cold pool from spreading. As a result, the cold pool moved in the opposite direction of the steering flow. Canyon effect of small topography contributed to the south movement of the cold pool. In addition, it provided an important northwest flow for the surface mesoscale vortex system.
    10  Meteorological Disaster Volume Model and Its Preliminary Application
    YIN Yizhou GAO Ge WANG Guofu
    2019, 45(10):1439-1445. DOI: 10.7519/j.issn.1000-0526.2019.10.010
    [Abstract](615) [HTML](386) [PDF 912.21 K](904)
    Based on the conceptual model of disaster magnitude, a four-dimensional meteorological disaster volume model is proposed. The disaster plane, which is composed of the numbers of affected people, affected area and direct economic losses, is considered as the basic scale of the disaster loss. The number of deaths and missing people is the fourth dimension, which is in the vertical direction of the disaster plane. Then, a four-dimensional meteorological disaster volume is formed. The disaster volume model has initially been applied to the annual evaluation of meteorological disasters in China, and the annual evaluation results show that meteorological disaster losses are obviously heavier in 2003, 2006 and 2010. The verification results show that the disaster volume model considers the number of the dead and missing people as a special dimension, highlighting its weight in the assessment of the whole disaster loss. In addition, the disaster area is added, making the evaluation results more complete.
    11  Analysis of Abnormal Characteristics at 500 hPa Signal Field in Major Cryogenic Freezing Rain and Snow Processes in Guangxi
    TANG Yi ZHOU Xiuhua ZHENG Chuanxin LI Weiwei
    2019, 45(10):1446-1456. DOI: 10.7519/j.issn.1000-0526.2019.10.011
    [Abstract](527) [HTML](182) [PDF 3.58 M](753)
    Using 500 hPa average circulation signal field and average temperature signal field, we analyzed the circulation abnormal characteristics of the first 40 major cryogenic rain and snow processes. The results showed that (1) This method that uses cold and wet index to select process has the function of assessing the influence degree cryogenic freezing rain and snow in Guangxi. (2) Most signals of the 40 cases have strong area and strong signal reflection, having prominent positive anomalies. The anomalies are usually represented by a positive system in the high field, known as the ridge. The development of high latitude ridge in winter is usually combined with the strengthening of cold advection. Cold air accumulation is the key to the continuous freezing of low temperature rain and snow in Guangxi. (3) The signal field analysis can be divided into three categories. The weather system and its performance can be understood after the analysis of the signal field and high average field. The key areas and key systems for the cold and snow freezing weather in Guangxi are the Ural ridge and the front of transversal trough, the Baikal ridge and the front of northeast transversal trough, and the small trough in northwestern Xinjiang.
    12  Typhoon Observation and Analysis of Domestic Marine Meteorological Drift Buoy Experiment
    CAO Xiaozhong LI Xiaoxia LEI Yong WEN Huayang WANG Xie
    2019, 45(10):1457-1463. DOI: 10.7519/j.issn.1000-0526.2019.10.012
    [Abstract](575) [HTML](234) [PDF 2.68 M](767)
    This study introduces the domestic marine meteorological drifting observer which can continuously, reliably and accurately observe the severe sea conditions based on Beidou navigation communication. It was independently developed by China and integrated with marine hydrological element (sea surface temperature, seawater salinity) and meteorological elements (air temperature, pressure, wind speed and direction). Up to now the observation test has been carried out in a number of sea areas. From 20 August to 5 September 2017, three drifting observers were placed in Guangdong Bohe Test Base for observing test, one on the shore, and the other two in the offshore seas. During the trial, the Typhoon Hato and the Typhoon Pakhar hit the area. The data analysis shows that the drifting observer data have a good correlation with the data from the national operation observation stations. The drifting observer obtained the observation data of air temperature, pressure and sea temperature in the period of typhoon weather, which had obvious characteristics of typhoon weather process, and showed a reasonable and apparent diurnal variation characteristic. The tests have shown that the marine meteorological drift observation instrument has the ability to perform actual observations under severe sea conditions.
    13  Error Analysis of Sounding Temperature Data Based on the FNL and GRAPES Analysis Fields
    QIAN Yuan MA Xulin GUO Qiyun YANG Rongkang CAO Xiaozhong
    2019, 45(10):1464-1475. DOI: 10.7519/j.issn.1000-0526.2019.10.013
    [Abstract](558) [HTML](240) [PDF 2.58 M](769)
    Based on the FNL data of the United States NCEP and the analysis fields of Chinese GRAPES, the temperature data of Beijing sounder station are evaluated, including observation residuals, average deviations, standard deviations, probability density distributions, kurtosis coefficients, skewness coefficients, correlation coefficient and root mean square error. Then, the quality control of temperature data of sounding is conducted and the quality control effect is analyzed according to the evaluation results. The test results show that the sounding temperature is of good quality and the error is within ±1℃ basically. There is a slight difference between the evaluations of the FNL analysis and the GRAPES results. The threshold values of the suspicious value and error value selected at a single time can determined by itself adaptively according to the characteristics of residual distribution based on the analysis fields. The quality of the sounding temperature is improved and the data retain the original characteristics after quality control according to the evaluation. The quality control method can effectively eliminate the seasonal difference and the evaluation results of the two reference standards are basically consistent after quality control.
    14  Status of Land Cover Datasets for the BCC_AVIM Land Surface Model
    ZHOU Wenyan LUO Yong SHI Xueli LI Weiping ZHANG Yanwu
    2019, 45(10):1476-1482. DOI: 10.7519/j.issn.1000-0526.2019.10.014
    [Abstract](852) [HTML](386) [PDF 381.33 K](872)
    The land cover (LC) data is an important basic input in land surface and climate models. The LC datasets are introduced in this paper by taking the BCC_AVIM model as an example, including the data resolution, sources of different land types, and especially the vegetation cover with different types and classification methods are comparatively analyzed. The available international and domestic global LC datasets about the sources, classification strategy methods, and spatial resolutions are briefly overviewed. The applications of the various LC datasets into the land surface model are briefly discussed. There are some gaps between LC datasets and model use. Then, the possible solution to the poor consistency among different LC remote sensing datasets and possible application methods of the LC datasets in numerical models are addressed so as to make better use of the global LC datasets.
    15  Features and Possible Causes for the Spring Climate Anomalies in 2019
    LIU Yunyun CHEN Lijuan
    2019, 45(10):1483-1493. DOI: 10.7519/j.issn.1000-0526.2019.10.015
    [Abstract](1566) [HTML](235) [PDF 6.40 M](1276)
    In spring 2019 (March-April-May, MAM), the average temperature in China is 11.5℃, ranking the fourth in the same period since 1961. The average precipitation in China is 148.7 mm (near normal), with profound spatial differences. The precipitation is more than normal over Northeast China, east part of Northwest China and South China, but less than normal over Huanghuai, Jianghuai and most of Yunnan Province in MAM 2019. The MAM precipitation in Yunnan is the least since 1961. High temperature and uneven spatial distribution of precipitation lead to the coexistence of drought and flood disasters in MAM 2019. The sub-seasonal climate variability in spring 2019 is significant, showing the characteristics of the transition period from East Asian winter monsoon circulation to summer monsoon circulation. The high temperature in most China in spring (especially in March and April) is obviously affected by the mid-latitude circulation anomalies pattern. The Ural Mountains and to their north regions are the center of negative height anomaly, while the areas east of Ural Mountains to Lake Baikal are the center of positive height anomaly. Such an anomalous circulation pattern is very helpful to the overall high temperature in China. The atmospheric circulation systems present an obvious response to the tropical SST anomalies in MAM 2019. The western North Pacific subtropical high (WPSH) is strong, westward and southward extending, which basically determines the spatial pattern of spring precipitation anomaly in China. The intensity and location of WPSH not only directly control the pattern of precipitation anomaly in southern China, but also affect the distribution of precipitation over northern China through the interaction of circulation anomalies in mid-high latitudes. Further analysis on the influence of tropical SST forcing shows that the warming of tropical Indian Ocean SST plays a more important role in the sustained strengthening and westward trend of WPSH in the El Ni〖AKn~D〗o decaying spring. The influence of the El Ni〖AKn~D〗o event on the intensity of WPSH gradually weakens in spring, and the effect on the north-south position of WPSH becomes more obvious.
    16  Analysis of the July 2019 Atmospheric Circulation and Weather
    XIE Jin ZHOU Ningfang
    2019, 45(10):1494-1500. DOI: 10.7519/j.issn.1000-0526.2019.10.016
    [Abstract](844) [HTML](273) [PDF 4.44 M](1033)
    The main characteristics of the general atmospheric circulation in July 2019 are shown as follows. There were two polar vortex centers with stronger strength than normal in the Northern Hemisphere. As the 500 hPa geopotential height showed, the cold vortex over Europe was stronger than normal. The western Pacific subtropical high was by south during the first and middle dekads and moved northward during the last dekad of this month. In July, the monthly mean precipitation of China was 126.3 mm, more than the normal by 4.7%. The positive anomaly of precipitation was more than 100% in most regions of Jiangnan and the Southwest China while the negative anomaly of rainfall reached more than 50% in Huanghuai and Jianghuai regions. The monthly mean temperature of China was 22.1℃, which is a little higher than the usual. The mean high temperature days in July were 5.7 d, which is more than the usual (4.3 d). The high temperature days were significantly more than the normal in the south of North China, Huanghuai, Jianghuai and the south of Xinjiang. There were 61 stations where extreme high temperature events occurred and these stations are mostly located in the provinces of Shanxi, Liaoning, Xinjiang and Guangdong. There were seven regional torrential rain processes, most in South China and many stations measured extreme daily precipitation. Four typhoons were generated and only one landed China in July, less than normal.

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