ISSN 1000-0526
CN 11-2282/P

Volume 45,Issue 7,2019 Table of Contents

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  • 1  Evaluation on Forecasting Heavy Rainfall over Jiangsu Region Using Ensemble Forecast Techniques and Products
    CHEN Shengjie LIU Mei ZHANG Hanbin YU Jianwei CHEN Chaohui
    2019, 45(7):893-907. DOI: 10.7519/j.issn.10000526.2019.07.001
    [Abstract](1096) [HTML](342) [PDF 1.71 M](1410)
    Using global ensemble forecast of European Centre for MediumRange Weather Forecasts (ECMWF) from THORPEX Interactive Grand Global Ensemble (TIGGE) data, and the 24 h observed daily accumulated precipitation data from 20:00 BT to the next 20:00 BT, the applications of the EC ensemble forecast and multiple EC ensemble products and various forecast products of heavy rainfalls by postprocess techniques over Jiangsu Region are evaluated. The results show that the ensemble mean forecast exhibits a high missing forecast rate, and the threat score (TS) is lower than that of EC deterministic forecast. Distinct differences in the forecast skills of each member of EC members and greatly higher TS of the synthesis of the optimal forecasts indicate that the EC ensemble forecast holds great potential application for forecasting heavy rainfall. Multiple postprocess products of ensemble forecast have different performances. Maximum value, the optimal percentage, the frequencymatched based on precipitation forecast bias correction, probabilistic forecasts, ensemble anomaly forecast approach and DuZhou performanceranking method based on the maximum all have higher TS by more than 10%. Then, the TSs of 90% percentage, fusion, the fusionprobability matching and the DuZhou performanceranking method based on the mean or median values are all higher than the EC deterministic forecast. However, the median value and probability matching of EC ensemble forecast are less skillful than ensemble mean with small values in reference. The results of this evaluation may enhance the cognitions of ensemble forecast products and kinds of postprocess techniques, providing forecasters with a useful reference of the utilization of ensemble forecast products for the forecasting of heavy rainfall.
    2  Comparison of the MultiModel Forecasts for Severe Precipitation Based on the Object Verification
    QU Qiaona SHENG Chunyan FAN Sudan RONG Yanmin
    2019, 45(7):908-919. DOI: 10.7519/j.issn.10000526.2019.07.002
    [Abstract](775) [HTML](174) [PDF 2.42 M](1044)
    Aiming at the poor performance of the TS verification method, objectbased verification method is introduced, by which the objects in the two datasets are matched in area, position, morphology and intensity to get potential forecast information of spatial field. Taking EC_THIN, T639, ensemble forecast of WRF and BCSH for example, for the purpose of integrating the characteristics of multimodel, the optimal times about the forecast of each severe precipitation are selected and the boxandwhisker plots are used. The circulation patterns and influence systems of severe precipitation are typed. The results show that the score is the best about the forecast of heavy rainfall caused by tropical cyclone with midlow latitude circulation. The score of lowpressure vortex and shear line of heavy rainfall processes is better, of which the best forecast of model is BCSH and EnMAX. The forecasts of 12 models for pressure trough are ordinary. When the system is extratropical cyclone with heavy rainfall, the score is the worst.
    3  Response of Tropical Cyclone in the Northwest Pacific for Summer and Autumn ENSO Events
    TU Shifei XU Feng CHANG Shujie JI Qianqian ZHANG Yu
    2019, 45(7):920-930. DOI: 10.7519/j.issn.10000526.2019.07.003
    [Abstract](892) [HTML](125) [PDF 3.41 M](840)
    Based on historical track data of tropical cyclones (TC) in Northwest Pacific, 〖JP2〗ERAInterim reana〖JP〗lysis dataset and oceanic Ni〖AKn~D〗o indices, the characteristics of tropical cyclones in the Northwest Pacific during the two types of ENSO period are discussed by using statistical methods. The results indicate that the intensity and duration of TC are increasing and severe typhoon activities are more frequent over the Northwest Pacific in summer (SU) El Ni〖AKn~D〗o period. During the occurrence of autumn (AU) El Ni〖AKn~D〗o, the duration and intensity of TC are longer and larger than those generated in SU El Ni〖AKn~D〗o, and the frequency of TC is lower, but the number of super typhoons accounts for one third of total TC, with fewer of TCs landing in China. In addition, the formation positions of TC are more eastward than SU El Ni〖AKn~D〗o. However, the intensity and duration of TC are smaller and shorter, with more lowlevel TCs generated in the SU La Ni〖AKn~D〗a epoch. When the AU La Ni〖AKn~D〗a occurs, the intensity, duration, and TC strength are slightly larger and the generation location is eastward than those TC generated in SU La Ni〖AKn~D〗a period. Furthermore, it is found that the differences of relative vorticity, vertical shear and SSTA in the Central Pacific are important reasons for the diversification of TC activities during the two types of ENSO, and the intensity and position of subtropical high also have a greater impact on TC activity.
    4  MCS Classification and Characteristic Analyses of Extreme ShortTime Severe Rainfall in Hubei Province
    WANG Jue ZHANG Jiaguo WU Tao ZHONG Min WANG Shanshan ZHOU Jinlian HUANG Xiaoyan HAN Fangrong WANG Xiaoci
    2019, 45(7):931-944. DOI: 10.7519/j.issn.10000526.2019.07.004
    [Abstract](984) [HTML](243) [PDF 8.50 M](1256)
    Using the data of CINRAD, conventional sounding and surface observation, the radar echo characteristics during the mesoscale convective system (MCS) processes of 62 extreme shorttime severe rainfalls in Hubei Province during 2008-2015 were analyzed. Six MCS patterns were studied and summarized, including 4 linear patterns (trailingstratiform, parallelstratiform, backbuilding/quasistationary and training line/adjoining stratiform) and 2 nonlinear patterns (vorticitystratiform and surroundingstratiform). The study reveals that (1) the 4 linear MCS patterns and vertical distribution of ambient wind relative to the convective line component are basically consistent with the results of earlier studies. (2) The typical characteristic of the nonlinear vorticitystratiform MCS is that the spiral vortex convective echo bands are enwrapped by the wide range stratiformcloud rain echo. The vorticitystratiform MCSs are mostly formed near the shear line in front of the southwest vortex, which is mainly related to the triggering and organization of the mesoscale vortex system in the boundary layer over the transitional zone between mountain and plain of western Hubei. (3) The backbuilding/quasistationary MCSs mostly occur on the windward slope, which is related to the blocking function of the mesoscale terrain and the organizational role of the cold pool. (4) The vorticitystratiform pattern has the longest duration and the largest range, while the surroundingstratiform pattern is the shortest in duration.
    5  Millimeter Wave Radar Observation of Hydrometeor Distribution Characteristics of Cloud in Summer in Nagqu, QinghaiTibet Plateau
    ZHU Yijie QIU Yujun LU Chunsong
    2019, 45(7):945-957. DOI: 10.7519/j.issn.10000526.2019.07.005
    [Abstract](605) [HTML](151) [PDF 3.51 M](1076)
    Based on the millimeterwave radar data and sounding temperature data obtained from the third QinghaiTibet Plateau Atmospheric Scientific Experiment during July-August 2014, this study inverses the phase of cloud hydrometeor in summer in Nagqu, Tibet with the fuzzy logic method and conducts analysis research on its distribution features. Firstly, the typical cases of stratocumulus, nimbostratus, and deep convective clouds are analyzed, and it is found that the vertical distribution of reflectance factor, Doppler velocity, velocity spectrum width and depolarization factor of the three types of clouds are quite different, and the characteristics of radar measurements and distribution of hydrometeor phase are also quite different. Secondly, radar reflectivity characteristics of liquid, mixed and ice clouds are studied, which shows that both warm clouds and supercooled water have high value centers of reflectivity factor. The reflectivity distribution center of mixed clouds is invariable with height. The high reflectivity factor of ice cloud is mainly over 6 km and tends to concentrate with the increase of altitude. The high frequencies of the three phase clouds are concentrated at the heights of 1 km, 2-3 km and 3-4 km above the surface respectively. The frequency of liquid phase clouds is the highest in the morning, the frequency of mixed phase clouds is high in the afternoon and the frequency of ice phase clouds is the highest in the evening. The heights of three phase clouds in the morning are lower than that in the afternoon and evening, and the perpendicular range maximizes at night. The thickness of liquid phase clouds is generally less than 0.3 km, and the average thickness of ice phase clouds is the largest when the top of ice phase clouds is located at about 9 km height, while the thickness of mixed phase and ice phase in midlevel clouds varies only a little.
    6  Characteristics of Cloud Vertical Structure Under Different Synoptic Systems in Liaoning Province Based on CloudSat Observation
    SUN Li MA Jiali ZHAO Shuhui YANG Lei LIU Yang QIN Xin ZHANG Jinguang YUAN Jian
    2019, 45(7):958-967. DOI: 10.7519/j.issn.10000526.2019.07.006
    [Abstract](700) [HTML](110) [PDF 1.17 M](926)
    In order to distinguish the cloud vertical structure (CVS) under different synoptic systems and provide reference for artificial rainfall enhancement, the characteristics of 500-850 hPa surface circulation field during Liaoning artificial rainfall enhancement periods from 2004 to 2014 and the CVS observed by CloudSat under typical synoptic systems (occurrence frequency larger than twice per year) are analyzed. According to the configuration difference of circulation filed, about 225 episodes, namely 17 types of synoptic systems, are identified, of which 4 typical types are selected, including westerly troughshear linecold front (CF), westerly troughvertexMongolia cyclone (MCW), westerly troughvertexsouthern cyclone (SC) and vertexvertexMongolia cyclone (MCV). The analysis of CVS under typical systems shows that the dominated clouds are singlelayer clouds. Under the influence of SC, the heights of cloud bases are lower and cloud thicknesses are thicker than that of other systems while that of MCW are opposite. More than 50% of cloud intervals’ thicknesses are smaller than 1 km, and this proportion increases with the layer numbers. Taking the clouds with base height ≤2 km and thickness ≥2 km as the target clouds for artificial rainfall enhancement, we achieve the results that the proportion of qualified clouds under cloudy condition of SC is the highest (59.7%) and that of MCW is the lowest (14.5%). The target clouds are dominated by singlelayerlowcold clouds with base heights lower than 1 km and top heights higher than 7 km. Moreover, the thicknesses of cloud intervals have little effect on cold clouds seeding.
    7  Temporal-Spatial Variations of Summer Heavy Fog and Its Meteorological Influence Factors in Jiangsu Province
    ZONG Chen QIAN Wei BAO Yunxuan YUAN Chengsong ZHOU Linyi CUI Chixiao WANG Hongbin
    2019, 45(7):968-977. DOI: 10.7519/j.issn.10000526.2019.07.007
    [Abstract](670) [HTML](333) [PDF 2.55 M](1018)
    Based on the consecutive observational data per ten minute from 70 surface stations on the National Automatic Weather Observational Net during from 2013 to 2016 in Jiangsu Province, the temporal-spatial distribution patterns of summer heavy fog and its meteorological influence factors are analyzed. The results show that: (1) The heavy fog tends to be formed under the condition that the temperature is less than 29℃, the wind speed is slower than 3 m·s-1 and prevailing in the easterly wind. The low temperature and high humidity during the Meiyu season are probably the causes for the summer heavy fog with a higher frequency (42.4%) in June. (2) The diurnal variation of summer heavy fog is significantly different from the diurnal variations in autumn and winter. The heavy fog mainly appears from 00:00 BT to 06:00 BT and dissipates from 05:00 BT to 08:00 BT, and the duration is mainly within 6 hours. (3) Summer fog is mainly radiation fog. The radiation fog, advection fog and front fog account for 58.1%, 35.5% and 6.4% respectively. (4) The frequency of heavy fog presents a general decrease trend from the northeastern coastal region to the southwestern inland because the cooling rate in the north of the Huaihe River of Jiangsu is higher than that in the southern Jiangsu. (5) The weak rainfall of 6-24 h before the fog formation provides water vapor to the near-surface layer. After that, the weather clears with the stable atmosphere statically, which is beneficial to the appearance of summer heavy fog.
    8  Construction and Application of the Urban Surface High-Resolution and Fast Wind Field Model
    XING Pei FANG Xiaoyi ZHANG Ning CHENG Chen WANG Xinyao LIU Yonghong DU Wupeng YANG Ruozi DANG Bing
    2019, 45(7):978-988. DOI: 10.7519/j.issn.10000526.2019.07.008
    [Abstract](599) [HTML](350) [PDF 5.23 M](1098)
    This paper introduces the construction of the Urban Surface High-resolution and Fast Wind Field (USHFWF) model, which uses the mesoscale model simulation as the background field and 5 m resolution building data as the model input data. The USHFWF model is developed through block processing, spatial interpolation based on partition function and mass conservation constraint, in order to achieve the near-surface wind field with a high resolution (horizontal resolution of 10 m×10 m grid) covering city scale over a short period of time (about 2-3 h). Based on this model, wind field with 10 m resolution in downtown of Beijing (i.e. within Fourth Ring Road, 20 km×19 km) is simulated and validated at 8 typical times. The main results are as follows: (1) In terms of wind speed, the simulation is usually larger than the observed values. The accuracy rates of the four times in summer and winter are more than 90% and 60%, respectively. In terms of wind direction, the accuracy rate of the eight times is all more than 40%. (2) The high-resolution wind field simulated by USHFWF model reflects the diurnal variation characteristics of wind in the central part of Beijing. Obviously, the area with large wind speed usually corresponds to the underlying surface with less roughness, and the area with small wind speed and disturbed flow usually corresponds to the underlying surface with high-density or high-rise buildings. (3) The USHFWF model can also show fine scale characteristics of the key block’s wind field. Take a block near the East Second Ring Road as an example. The simulated wind field can clearly reflect the flow due to the distribution of buildings, such as diffluence, confluence, local circulation, and wake flow. In summary, USHFWF model provides an effective way to obtain high-resolution near surface wind field covering urban scale in a short time. It is helpful to identify the key areas that need to be improved or restricted to development, and to facilitate the rational construction and implementation of the urban ventilation corridors, so as to achieve the ultimate goal of optimizing the internal ventilation performance, alleviate the urban heat island effect and improve the wind-environment comfort.
    9  Evaluation of Multi-NWPs Rainstorm Forecasting Performance in Different Time Scales in Huaihe River Basin and Discussion on Flood Predictability
    HAO Ying WANG Yuan WANG Hao QIU Xuexing
    2019, 45(7):989-1000. DOI: 10.7519/j.issn.10000526.2019.07.009
    [Abstract](540) [HTML](161) [PDF 5.42 M](1044)
    In order to make the numerical forecast products achieve the best application effect in Huaihe River Basin meteorological operation, and to provide decision support for flood control, the forecasting performances of four numerical weather predictions (EC, JMA, WRF and INCA) for 24 h, 12 h, 6 h, 3 h and 1 h time-scale rainstorms in Huaihe River Basin during flood seasons from 2015 to 2017 were evaluated by means of TS score, false alarm rate and missing forecast respectively. The lead time of usable forecast of four models for various time scale rainstorms was compared and analyzed as well. On this basis, EC precipitation forecasting with 24 h time resolution was selected to drive distributed hydrological model CREST and construct a meteorological-hydrological coupling flood forecasting model for the upper reaches of the Huaihe River. Moreover, the real-time operation results of June-August 2016 and May-August 2017 were evaluated, and the predictability of flood in the Huaihe River basin was discussed. The main conclusions are as follows: (1) EC has the best forecasting performance and the longest usable time for 24 h and 12 h rainstorms. When the time scale of rainstorm is 6 h, the WRF’s forecasting performance and usable time are both better than EC. When the rainstorm occurs within 3 h, the advantage of WRF is more obvious. JMA has the worst forecast performance for all time scale rainstorms. (2) EC and WRF show abnormally high missing forecast rate and low TS when the lead time is less than 3 h. So the two NWPs cannot provide valuable reference for rainstorm nowcasting. However, INCA shows perfect performance in rainstorm nowcasting with TS score of 54% in 1 h forecast, and the lead time of usable forecast is 3 h. (3) The performances for 6 h and 3 h time scale rainstorm forecasting of EC, JMA and WRF have obvious features of diurnal variation. (4) The lead time of usable forecast for flood forecasting in the upper reaches of Huaihe River is 108 h.
    10  Research on Accelerated Optimization of Climate Models Based on GPU-OpenACC
    XIAO Sa WEI Min DENG Shuai XU Da ZHANG Chenchen
    2019, 45(7):1001-1008. DOI: 10.7519/j.issn.10000526.2019.07.010
    [Abstract](541) [HTML](226) [PDF 1.52 M](832)
    In order to make the numerical model adapt to the fast development trend of high performance computing with hybrid architecture, based on the OpenACC, this paper presents the GPU accelerated optimization test for the three-segment procedure which is Beijing Climate Center Atmospheric General Circulation Model version 3.0 (BCC_AGCM3.0) in dynamic part. By means of asynchronous execution settings, cyclic inward migration, data management and vector parameterized configuration, we parallel the GPU acceleration of the computationally intensive part of the program segments in model, compare the optimization efficiency and validate the correctness. The experimental results show that the efficiency of the three-stage GPU acceleration in BCC_AGCM climate model, is increased by more than three times and the relative error of global vorticity root mean square (RMS) is controlled within a certain range. The acceleration methods and strategies are valuable for transplanting and optimizing numerical weather and climate models in heterogeneous environments.
    11  Comparison Study on Several Grid Temperature Rolling Correction Forecasting Schemes
    ZENG Xiaoqing XUE Feng ZHAO Ruixia ZHAO Shengrong
    2019, 45(7):1009-1018. DOI: 10.7519/j.issn.10000526.2019.07.011
    [Abstract](898) [HTML](167) [PDF 10.69 M](1189)
    To obtain more accurate and faster grid temperature forecast products, the study used a high-frequency gridded observation fusion product and eight kinds of error correction methods to carry out a rolling correction forecast test for the 2 m temperature forecast filed of the European Centre for Medium-Range Weather Forecasts. The test was conducted on two forecast simulations from 1 January to 28 February 2017 and from 1 June to 30 July 2017, starting at 14:00 BT and 20:00 BT in Beijing, and was performed in 3-24 hours rolling prediction correction. The forecast results were tested and analyed using grid observation fusion data and site observation data. The results show that the eight methods have positive correction effects on the direct model output. The full-grid sliding error regression model correction and the full-grid sliding two-factor regression model have the best correction effect. Both schemes can make the average absolute error of the grid of the correction field below 2℃, and the grid accuracy of 3 h, 6 h and 9 h is above 0.9. The prediction results of the full-grid sliding error regression model are slightly better than the prediction results of the full-grid sliding two-factor regression model. This shows that the error field at the beginning of the forecasting time plays an important role in the correction as a predictor of the regression model.
    12  Northern Hemisphere Atmospheric Circulation Characteristics in Winter 2018/2019 and Its Impact on Temperature Anomalies in China
    ZHI Rong GAO Hui
    2019, 45(7):1019-1027. DOI: 10.7519/j.issn.10000526.2019.07.012
    [Abstract](802) [HTML](148) [PDF 3.61 M](1166)
    The East Asian winter monsoon and the Siberian high were both stronger than normal during the 2018/2019 winter. For geopotential height anomalies at 500 hPa in Northern Hemisphere, the Ural Mountain Area was positive anomaly, and Baikal Lake-Barkash Lake Area was negative anomaly. The mid-high latitudes of Eurasia were mainly dominated by meridional circulation. In winter 2018/2019, the cold air processes occurred frequently and the intensity was strong. The temperature in the northeastern, southwestern and central and eastern parts of South China were higher than normal, but the other parts were on the low side due to the influence of the cold air processes. In addition, the intraseasonal variation of circulation of the mid-high latitudes of Eurasia was significant, which leads to the periodic characteristics of temperature anomaly in China. The lower concentration of sea ice in the Barents Sea and Kara Sea in the early autumn is the main reason for the strong East Asian winter monsoon.
    13  Analysis of the April 2019 Atmospheric Circulation and Weather
    ZHOU Xiaomin ZHANG Tao
    2019, 45(7):1028-1036. DOI: 10.7519/j.issn.10000526.2019.07.013
    [Abstract](806) [HTML](105) [PDF 7.70 M](1031)
    The main characteristics of the general atmospheric circulation in April 2019 are as follows. Two polar vortex centers were in the Northern Hemisphere. The circulation in middle-high latitudes of the Eurasian showed an atypical three-wave pattern, and there was a positive anomaly of the geopotential height over most of China. The strength of Western Pacific subtropical high and the Bay of Bengal trough were both stronger than the climatological normal. The monthly mean temperature was 12.7℃, higher than the normal (11.0℃) by 1.7℃. The monthly mean precipitation amount was 49 mm, more than the normal (44.7 mm) by 9.6%. Two nationwide strong cold air processes happened in this month. There were eight heavy rainfall events and nine severe convection events throughout the country in this month. Several provinces were attacked by severe thunderstorms and hail disaster while severe droughts occurred in the northeast of Inner Mongolia and Northeast China. In addition, Northern China experienced four sand-dust weather events.

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