ISSN 1000-0526
CN 11-2282/P

Volume 42,Issue 2,2016 Table of Contents

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  • 1  Fuzzy Verification Test and Comparison of Three Types of Severe Convective Weather Nowcasting
    LI Baiping DAI Jianhua ZHANG Xin WANG Xiaohua
    2016, 42(2):129-143. DOI: 10.7519/j.issn.1000-0526.2016.02.001
    [Abstract](1706) [HTML](87) [PDF 4.37 M](1805)
    Abstract:
    Severe convective weather is hard to forecast because of the character of small scale and rapid development. Fuzzy verification methods can get evaluation information at different spatial scales by using a spatial window or neighborhood surrounding the forecast and/or observed points, and are introduced into the verification of severe convective weather in this article. Focusing on the three types of severe convective weather, some operational nowcasting products like as onehour reflectivity extrapolation product of the Chinese Meteorological Administration (CMA) SWAN (Severe Weather Analysis and Nowcasting) system, are verified using the fuzzy method. Then, three ideal severe convective weather models are also built and verified to give a further study on the abovementioned methods. The results show that compared to traditional metrics with the stagey of “point to point”, fuzzy verification can glean additional information in different scales and evaluation strategies, evaluating forecasts more comprehensively and objectively. Based on different evaluation strategies, one forecast has different optimal scales and each fuzzy verification method has its own feature and application. When forecast has large bias, fuzzy verification methods can still give effective or “useful” scores while traditional metric can only give poor scores. For the severe convective events with characteristics of high thresholds and small scales, the fuzzy verification methods including minimum coverage with low fraction, fuzzy logic and multievent contingency table show more potential value than the traditional ones.
    2  Characteristics of ShortTime Severe Rainfall Events Based on Weather  Flow and Key Environmental Parameters in Pearl River Delta
    CHEN Yuanzhao YU Xiaoding CHEN Xunlai
    2016, 42(2):144-155. DOI: 10.7519/j.issn.1000-0526.2016.02.002
    [Abstract](1955) [HTML](67) [PDF 2.78 M](1865)
    Abstract:
    In order to understand the environmental characteristics of shorttime severe rainfall event (hourly rainfall amount ≥50 mm) in Pearl River Delta, we researched the weather flow, Tlnp chart patterns and key physical parameters of 68 shorttime intense rain event for nearly 7 years (2007-2013) by using automatic weather station data, sounding data, satellite data in the Pearl River Delta region. The results showed that such severe rainfalls in Pearl River Delta are characterized by, first, the weather flow patterns, which include typhoon type, southwest monsoon type, Beibu Gulf low pressure type, cold shear line type and tropical cloud type. Different types have different frequencies in different seasons. Secondly, temperature profiles and wet adiabat are very close in Tlnp in most of the shorttime severe rain events, and the water vapor content are rich in the whole layer. Thirdly, the features of the key parameters of the severe rainfalls are that mainly the value of T850-T500 is small, usually 21-23℃ with a weak unstable stratification, higher ground dew point and PW. CAPE values are more moderate, mostly less than 1500 J·kg-1. CIN and vertical wind shear of 0-6 km are relatively weak, and lowlevel jets appear in most cases. The key conditions for most of the shorttime severe rainfall process are not the highaltitude cold air intrusion, but the warm air transport from low level. Although small CAPE value limits updraft, the cloud base of specific humidity is high. If combining the configuration method of flow pattern (type), the key environmental parameters, the range of parameters to set appropriate threshold according to the box whisker plots, we can provide valuable reference to rebuild the forecast method of shorttime severe rainfall in the Pearl River Delta region.
    3  Role of Supper Typhoon Danas in the Extreme Precipitation Caused by Severe Typhoon Fitow
    XIE Huimin REN Fumin LI Guoping MA Liangchen QIU Wenyu
    2016, 42(2):156-165. DOI: 10.7519/j.issn.1000-0526.2016.02.003
    [Abstract](1431) [HTML](125) [PDF 3.50 M](932)
    Abstract:
    By using the surface observational data, typhoon track data and ECMWF global reanalysis data, as well as the objective synoptic analysis technique (OSAT), tropical cyclone (TC) track similarity area index (TSAI) and the airflow trajectory model (HYSPLIT4.9), this paper analyzes the characteristics and the causes of the extreme precipitation created by the Severe Typhoon Fitow over the coastal region of Southeast China, and reveals the intensification role of binary typhoons in extreme precipitation. First, Fitow causes the maximum daily precipitation of 395.6 mm in Yuyao and Fenghua, which ranks the second daily extreme TC precipitation in Zhejiang Province in record. Two distinct intense precipitation stages are found in the precipitation process. Secondly, such intense and continuous rainfall during and after Fitow’s landfall is mainly due to the existence of Super Typhoon Danas. In the first stage of the severe precipitation the interaction of the binary tropical cyclones contributes to the extremity, causing Fitow to move much faster than before. Moreover, Danas transports about 79% moisture to the raining region, acting as an important contributor to the extreme precipitation over the southern coast of Hangzhou Bay. In the second stage, as the circulation of Typhoon Fitow almost dissipates, the combined interaction of Super Typhoon Danas and cold air causes the occurrence of the extreme precipitation.
    4  Analysis of an OccludedShape Mesoscale Convective System (MCS)  and Concomitant Mesoscale Convective Vortex (MCV) in Jiangsu
    CHEN Yonglin YU Xiaoding YANG Yinming WANG Hui LIU Hongya
    2016, 42(2):166-173. DOI: 10.7519/j.issn.1000-0526.2016.02.004
    [Abstract](1031) [HTML](199) [PDF 3.02 M](944)
    Abstract:
    By using the surface observational data, typhoon track data and ECMWF global reanalysis data, as well as the objective synoptic analysis technique (OSAT), tropical cyclone (TC) track similarity area index (TSAI) and the airflow trajectory model (HYSPLIT4.9), this paper analyzes the characteristics and the causes of the extreme precipitation created by the Severe Typhoon Fitow over the coastal region of Southeast China, and reveals the intensification role of binary typhoons in extreme precipitation. First, Fitow causes the maximum daily precipitation of 395.6 mm in Yuyao and Fenghua, which ranks the second daily extreme TC precipitation in Zhejiang Province in record. Two distinct intense precipitation stages are found in the precipitation process. Secondly, such intense and continuous rainfall during and after Fitow’s landfall is mainly due to the existence of Super Typhoon Danas. In the first stage of the severe precipitation the interaction of the binary tropical cyclones contributes to the extremity, causing Fitow to move much faster than before. Moreover, Danas transports about 79% moisture to the raining region, acting as an important contributor to the extreme precipitation over the southern coast of Hangzhou Bay. In the second stage, as the circulation of Typhoon Fitow almost dissipates, the combined interaction of Super Typhoon Danas and cold air causes the occurrence of the extreme precipitation.
    5  Analysis on a Gust Front of Squall Line Event in North China
    ZHENG Lina ZHENG Lina
    2016, 42(2):174-182. DOI: 10.7519/j.issn.1000-0526.2016.02.005
    [Abstract](1501) [HTML](157) [PDF 2.83 M](1096)
    Abstract:
    Using conventional observational data, surface meteorological observation data and Doppler radar data, the weather characteristics and causes of the gust front in North China on 4 August 2013 are analyzed. The results indicate that the configuration of ground front and forwardtilting trough is the favorable largescale circulation background of the gust front. Between the outflow cold air of surface mesoscale high and environment wind forms a mesoscale convergence line, which makes the convective activity get intensified, causing new thunderstorms to generate or be strengthened. In the mature stage, squall line has distinct characteristics, and develops to the right. At first, the gust front forms in front of severe thunderstorms of the squall line. The stronger the squall line, the stronger the gust front. The maintainance of the gust front relies mainly on the continued sinking airflow of the storm. The gust front weakens after the sinking airflow drops off. Meteorological elements have dramatic changes as the squall line and gust front are passing through the area. When the system develops stronger, the variation of meteorological elements of gust front is greater than that of squall line, but is weaker in the rest time. After the squall line gets weakened, the gust front still also maintains for a period of time, which needs to be observed more carefully.
    6  Backward Trajectory and Circulation Features in Different  Haze Processes in Winter of Zhejiang
    WENG Zhimei LI Liping YANG Wanyu LIU Liyuan
    2016, 42(2):183-191. DOI: 10.7519/j.issn.1000-0526.2016.02.006
    [Abstract](1530) [HTML](148) [PDF 4.01 M](1063)
    Abstract:
    Based on available observation data of Zhejiang Province for the period from 1981 to 2013, temporal and spatial distribution characteristics of winter haze in Zhejiang Province were analyzed. The results show that haze days have increased significantly since the mid1980s. Haze days in the northern and western part of the province are much more than the south and the east, also more in the basin and plain than on the hills and islands. The division of the haze distribution pattern is obtained according to the Kmeans clustering analysis, which shows the pattern can be divided into two categories. The first category accounts for 62% of the total haze, most of which happens in December, while most of the second category usually appears in January and December. In the end, according to the NCEP/NCAR reanalysis data, the different atmospheric circulation features, including the strength of cold high, vertical velocity and the distribution of water vapor, are discussed for the two kinds of haze patterns respectively. It is found that Zhejiang Province is controlled by cold high from northern China and the sinking airflow in the first haze pattern. In the second haze pattern, however, the cold high has transformed, and the sinking flow is also weakened, which makes air move slowly, so it is hard for pollutants to dissipate.
    7  Climate Characteristics and Impact Factors of LowVisibility  Heavy Fog on Jiangsu Coast Expressway
    WANG Boni PU Meijuan TIAN Li ZHANG Zhendong WU Jianjun
    2016, 42(2):192-202. DOI: 10.7519/j.issn.1000-0526.2016.02.007
    [Abstract](1592) [HTML](77) [PDF 3.51 M](1132)
    Abstract:
    This paper analyzed the dense fogs with low visibility (<0.5 km) that occurred from June 2012 to June 2014 on the Jiangsu Coast Expressway, and investigated the climate characteristics, meteorological elements and main circulation situation of these dense fogs with low visibility. The results indicated that there are significant differences in the monthly frequency of the dense fogs. Fogs occur frequently from March to June, and also from December to the next February. The frequency of the dense fog in spring and winter is higher than that in summer and autumn. The peak of the low visibility usually appears during 03:00-05:00 BT in the early morning, and dissipates at around 08:00 BT. If the visibility is lower than 0.5 km, the relative humidity increases to 97%, temperature is 0-4℃, wind speed decreases to less than 2 m·s-1, and wind direction is between ENE and SSE, then the visibility can further decrease to less than 0.2 km. The statistical analysis of the circulation background based on 150366 samples indicates that the low visibility in the northern and central section of the expressway is closely related to prefrontal fog. This section is located in the forepart of the cold front, and the warm sector exists in the midlow level part. The low visibility of the whole expressway is due to the advection fog and radiation fog. The radiation fog exists in the downdrafts of upper air, and the weak pressure field or the high pressure moves to the south on the surface. The advection fog is in the region of thermal advection in the midlow troposphere and behind the highpressure system entering the sea or at the east side of the inverted trough, while southeast and east winds are blowing on the surface. Before the dense fog (the visibility<0.2 km) comes, there is a largeamplitude oscillation with obvious “trunklike” fluctuating forepart in terms of the visibility on the Jiangsu Coast Expressway. This feature provides a basis for monitoring and warning of the dense fog with visibility below 0.2 km.
    8  Analysis of a Typical Air Pollution Event in Shanghai
    CHEN Lei MA Jinghui GENG Fuhai XU Jianming
    2016, 42(2):203-212. DOI: 10.7519/j.issn.1000-0526.2016.02.008
    [Abstract](1394) [HTML](69) [PDF 5.06 M](942)
    Abstract:
    A continuous air pollution event which occurred in Shanghai during 4-9 March 2013 was investigated. The main features of air pollution transportation and formation were preliminary discussed by using the hourly observation data of PM2.5 and PM10, conventional weather data, data from the groundbased Micro Pulse Lidar (MPL_4B), data from FY3A satellite and NCEP (1°×1°) reanalysis data. The results show that the pollution event was mainly influenced by the weather condition in upper and lower levels. The northwest wind after the trough, the stable stratification and the weak pressure field made air pollutants difficult to disperse. The northwest wind at 850 hPa could transport the dust to Shanghai, and then the dust subsided to the ground surface. The faint wind and the stable temperature stratification near the surface provided favorable conditions for the formation and maintenance of the heavy pollution event.
    9  Simplified Assessment Method and Application Research of Rainstorm Disaster Risk and Impact ——Using JingJinJi “7.21” Heavy Rain as an Example
    WANG Xiurong Zhongliang WANG Liping JIANG Weiguo MA Guobin
    2016, 42(2):213-220. DOI: 10.7519/j.issn.1000-0526.2016.02.009
    [Abstract](1539) [HTML](72) [PDF 7.41 M](906)
    Abstract:
    According to the spatiotemporal distribution characteristics of the rainfall and the geographic features, China is divided into four rainfall areas. On this basis, we developed the different assessment methods of the intensity grade of the heavy rains for every rainfall area. At the same time, elevation, standard deviation of elevation, drainage density and soil types have been identified as import controlling factors of the torrential rain disasters, and these factors were respectively classified into different grades. The comprehensive rainstorm disaster risk assessment model is established by weighted summation of the rainfall factors and the selected controlling factors. Based on the model, we further applied GIS to evaulate the number of affected urban and rural residents and land areas in different risk levels. Compared with the previous rainstorm risk assessment models, this rainstorm risk assessment model can be applied more widely in any regional rainstorm disaster risk assessment. Moreover, this model has stronger operation ability of pre assessment, realtime assesment and postassessment by using realtime or forecast rainfall data. Finally, combined with GIS, this model can achieve quantitative evaluation of the hazardaffected bodies at the different risk levels.
    10  Preliminary Study on Disastrous Law of Drought  and Flood in Hubei Province
    ZHOU Yue ZHOU Yuehua YE Limei GAO Zhengxu
    2016, 42(2):221-229. DOI: 10.7519/j.issn.1000-0526.2016.02.010
    [Abstract](1800) [HTML](117) [PDF 3.94 M](1087)
    Abstract:
    Using the daily precipitation and disaster census data of 76 meteorological stations in Hubei from 1960 to 2005, this paper studied the spatiotemporal distribution and disastrous laws of drought and flood. The results show that the frequent occurrence area of drought presents an eastwest zonal distribution, while the annual occurrence frequency and area of flood are significantly less than those of drought. The annual average drought and flood disasters show opposite variation trends after 1996 in which droughts were more experienced but floods became less. Both of the two disasters concentrate in summer. In addition some areas of Hubei suffered from serious drought disaster continously from 1996 to 2001. The cumulative effect of the drought disaster caused the agricultural economic loss to be leapfrog growth, reaching the maxima in 2001. The flood disastercausing intensity is quasi periodic oscillation. The damaged areas of agriculture crops and agricultural economic losses reach maximum values in the 1990s with correlation coefficient being 0.80. So, positive correlation exists between the floodaffected population and direct economic loss. The increasing speed of direct economic losses is accelerated with increasing floodaffected population, while the abilities to prevent flood disaster are also strengthened. The droughtflood abrupt alternation mainly occurs in the northwest and southeast of Hubei in summer. During sharpturn disaster processes, as drought strengthens the vulnerability of crops and causes serious economic loss in the early period, the increasing speed of agricultural economic losses is accelerated with the growth of disasteraffected areas, but the agricultural economic loss would be less than the losses separately caused by droughts or floods.
    11  Method Study of Classification and Recognition of Thunderstorm System Less than 50 km
    WANG Ping GAO Yi LI Cong
    2016, 42(2):230-237. DOI: 10.7519/j.issn.1000-0526.2016.02.011
    [Abstract](1129) [HTML](188) [PDF 1.37 M](998)
    Abstract:
    To solve the problem of automatic classification and recognition of thunderstorm system with horizontal scale less than 50 km, four features are constructed, including the density feature of thunderstorm system, emigation rate, liquid water content and cumulative liquid water content. There are significant differences in these features between hail and shorttime intense precipitation. In addition, these features can be used to describe complex system that generates hail and shorttime heavy precipitation at the same time. In view of the relationship between cumulative liquid water content and time series, the iterative mechanism is introduced in the classification tree. Experiments show that the recognition rate of systems generating shorttime heavy precipitation is as high as 89.1% and the false positive rate is 9.5%, while the recognition rate of systems generating hail is 79.8% and the false positive rate is 3.5%. The average critical success index (CSI) reaches 80.0%.
    12  Case Study on the Convective Clouds Seeding Effects  in YangtzeHuaihe Region
    JIA Shuo YAO Zhanyu
    2016, 42(2):238-245. DOI: 10.7519/j.issn.1000-0526.2016.02.012
    [Abstract](906) [HTML](59) [PDF 3.52 M](1018)
    Abstract:
    Convective clouds in YangtzeHuaihe Region are the main seeding objects of precipitation enhancement experiments in Anhui Province in summer. Unrandomized seeding operations are usually adopted using rocket launchers, artilleries or ground generators, rather than the randomized trials through strict test design due to some limited condition. Convective clouds have characteristics of short life span and considerable large local and natural variations, which add great difficulties to the objective, scientific and quantitative evaluation of the operation effects. Based on daily rainfall data of national ground stations of Anhui Province and SA Doppler Radar data of the operation areas, this paper makes a case study on the seeding effects of convective clouds in YangtzeHuaihe Region from 28 to 30 June 2012 with combination of regional historical regression statistical analysis and physical test method using Doppler Radar identification and track of cloud seeding. The results indicate that the rainfall of target area increases 37.2 mm and obtains an enhancement rate of 65.19% after seeding, with a significant level α<0.1. We identify and track seeded units according to the radar data, define appropriate control units and then compare the radar echo parameters of seeded units and control units before and after operation to give physical evidence of the operation effects.
    13  Performance Verification of MediumRange Forecast by T639 and ECMWF  and Japan Models from September to November 2015
    ZHANG Feng
    2016, 42(2):246-253. DOI: 10.7519/j.issn.1000-0526.2016.02.013
    [Abstract](897) [HTML](144) [PDF 6.50 M](770)
    Abstract:
    The mediumrange forecasts are verified and compared for the models of T639, ECMWF and Japan from September to November 2015. The results show that all of the three models can predict the variation and adjustment of the atmospheric circulation over Asian middle and high latitude areas well, of which ECMWF model performs the best. The ECMWF model has a good performance in predicting the position of the ridge line of western Pacific subtropical high, while T639 model is better at predicting the position of west ridge point. The three models do well in predicting the transitions of temperature at 850 hPa, and the temperature forecast biases for southern China are smaller than for northern China. As far as Typhoon Mujigae (No.1522) is concerned, the three models show different biases in its track and intensity forecasts, especially they are weak in the intensity forecasting at the early stage of the typhoon. T639 and ECMWF perform better in forecasting mediumrange static stability weather, while ECMWF does even better than T639 when forecasting cold airs that disperse fog and haze.
    14  Analysis of the November 2015 Atmospheric Circulation and Weather
    SHEN Xiaolin HE Lifu
    2016, 42(2):254-260. DOI: 10.7519/j.issn.1000-0526.2016.02.014
    [Abstract](1095) [HTML](127) [PDF 4.04 M](1512)
    Abstract:
    The main characteristics of the general atmospheric cirulation in November 2015 are listed as follows: There is one polar vortex centre in the Northern Hemisphere. In the midhigh latitudes, the circulation presents a threewave pattern. The average south branch trough is located around 90°E. The northwestern Pacific subtropical high is stronger than normal, located more westward. Meanwhile, monthly mean precipitation amount is 39.4 mm, which is 1.1 times more than its climatological mean. Monthly mean temperature is 4.1℃, being 1.2℃ higher than normal except the North and Northeast China. Two cold air processes and 4 severe rainfall events take place with extreme precipitation records observed at some stations in China. Moreover, the precipitation amount of Jiangnan, South China and other parts is 2-3 times more than normal. In addition, three heavy pollution weather processes are experienced during this month.

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