ISSN 1000-0526
CN 11-2282/P

Volume 42,Issue 3,2016 Table of Contents

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  • 1  Abrupt Decrease of Yunnan Summer Rainfall in the Early 21st Century and Its Possible Reasons
    XIAO Ziniu SHI Wenjing DUAN Wei
    2016, 42(3):261-270. DOI: 10.7519/j.issn.1000-0526.2016.03.001
    [Abstract](1537) [HTML](84) [PDF 2.53 M](1058)
    Abstract:
    Based on the observation data from 125 stations in Yunnan Province, the reanalysis data from National Centers for Environmental Prediction/National Center for Atmospheric Research and the monthly extended reconstructed sea surface temperature data from the National Oceanic and Atmospheric Administration in 1960-2013, the variation of the Yunnan rainfall and its related atmospheric circulation were analyzed. Major results are as follows: Yunnan rainfall experienced an abrupt decrease in 2002, which is mainly attributed to the notable reduction of Yunnan summer rainfall. Further analyses verified that the prominent decrease in Yunnan summer rainfall seems to be related to the intensified easterly of lower troposphere and strengthened westerly of upper troposphere over tropical Indian Ocean. Besides, the increasing temperature of the Asia continent in middle and high latitudes also play an important role in the abrupt decrease of Yunnan summer rainfall.
    2  Characteristics of the First Soaking Rain in Northeast China and  Its Response to Surface Heat Source over the Tibetan Plateau
    XU Shiqi LI Dongliang
    2016, 42(3):271-279. DOI: 10.7519/j.issn.1000-0526.2016.03.002
    [Abstract](1162) [HTML](69) [PDF 4.19 M](858)
    Abstract:
    Based on the precipitation data in April and May for the period 1958-2012 from 178 meteorological stations in Northeast China, JRA55 and NCEP/NCARI reanalysis, the study is performed of the first soaking rain date as well as its relation with the soaking rainfall and the total rainfall from April to May. In addition, response of the soaking rain date to the surface heat source over the Tibetan Plateau is also discussed. The results suggest that, since 1958, the soaking rain date in Northeast China, has shown a positive relation with the soaking rainfall and a negative relation with the total rainfall, suggestive of the place where the soaking rain date is early (late), the soaking rainfall is smaller (larger) and the total rainfall is larger (smaller). Besides, the correlation between the surface heat source over the Tibetan Plateau in April and the soaking rain date is negative, which means when the surface heat source in April gets enhanced, cold air from the north and warm air from the south intersect over Northeast China, updrafts, are strengthened, and water vapor transport is abundant, making the soaking rain date in Northeast China come early (late).
    3  Analysis on Environmental Conditions and Structural Features  of Typical Convective Tornado Storm in Meiyu Period
    ZENG Mingjian WU Haiying WANG Xiaofeng JIANG Yifang
    2016, 42(3):280-293. DOI: 10.7519/j.issn.1000-0526.2016.03.003
    [Abstract](1188) [HTML](156) [PDF 5.23 M](943)
    Abstract:
    By reanalysis data (1°×1°) 4 times a day from FNL/NCEP, Doppler radar, and automatic weather station (AWS), this paper analyzed the formation and structure characteristics of the convective storms which resulted in tornadoes from Anhui Tianchang to Jiangsu Gaoyou on 7 July 2013 after analyzing on environmental characteristics and feature extraction of convective parameters of tornadoes in Jiangsu Province in recent ten years’ Meiyu period. The results show that during the Meiyu period in YangtzeHuaihe Region, tornadoes are prone to occur in the right side of mesoscale cyclone (100 km), the lower right side of mesoscale vortex (200-300 km) and the left rear of lowlevel jet stream. General circulation in the Meiyu period provides plentiful moisture, favorable unstable stratification and dynamic conditions for tornadoes. The lowlevel cyclonic vorticity develops strongly before tornado. Vertical wind shear in boundary layer promotes cyclonic vorticity in tornado storm to strengthen rapidly, and enhancement of convergence in low troposphere is conducive to initialization of convection. As for tornadoes in Meiyu period, the demand to convective energy accumulation is lower than hails and thunderstorm gales. Bias between convective parameters feature value and climatic average value provides references for shortrange forecast of tornado. The tornado convective storm that triggered the tornado on 7 July 2013 initialized near surface convergence line. The strength of surface convergence and mesoscale frontal zone contributed to the development of convective storm. The series of tornadoes were produced by a longlife supercell storm which had echo characteristics of typical supercell. The mesocyclone inside the storm maintained two hours. Generally, the evolution of the mesocyclone parameters has great reference value to tornado warning, which shows that when the bottom height is low and shear values are significantly enhanced in the mesocyclone, tornadoes are more likely to occur.
    4  An Analysis of Vorticity Evolution and Physics Mechanism on an Extratropical Cyclone
    XIONG Qiufen ZHANG Xin TAO Zuyu
    2016, 42(3):294-304. DOI: 10.7519/j.issn.1000-0526.2016.03.004
    [Abstract](1252) [HTML](84) [PDF 5.27 M](1268)
    Abstract:
    As cyclone is vortex, the parameter relative vorticity (for brevity, vorticity) can be used to exactly describe the position and intensity of extratropical cyclone. Thus, the research of the extratropical cyclone development is actually the mechanism analysis of vorticity. With the geostrophic wind vorticity at 1000 hPa adopted in this study, a typical extratropical cyclone with a spiral track occurred during 6-10 June 2014 is diagnosed using conventional observations and NCEP 1°×1° reanalysis data. Based on Petterssen’s equation, and the configuration of positive vorticity advection and divergence at 300 hPa and thermal advection at 850 hPa, this paper investigates the contributions of thermal advection in middlelower layer of troposphere, the vorticity advection at 500 hPa and the divergence induced by the vorticity advection at 300 hPa to the development of surface cyclone. The results show that: (1) Vorticity transferred between 2 positive vorticity zones at 300 hPa and 500 hPa. The first positive vorticity zone was the main one during cyclogenesis and development while the other became dominant in the decaying period. (2) In the whole troposphere, the vorticity centers moved cyclonically on a curve path. During the development of the surface cyclone, the positive vorticity centers tilted rearward with height, and while weakening, they were vertically overlapped at different levels. (3) The temperature advection played a major role in cyclogenesis while positive vorticity advection at 500 hPa was the main factor in the cyclonic development. (4) Cyclone would develop when the divergence caused by positive vorticity advection at 300 hPa was located above the frontal zone at 850 hPa.
    5  Analysis on Causes for the Severe Rainfall in Northeastern  Zhejiang Induced by Typhoon ChanHom (1509)
    ZHOU Fu QIAN Yanzhen FANG Yanying GU Xiaoli WANG Yi
    2016, 42(3):305-313. DOI: 10.7519/j.issn.1000-0526.2016.03.005
    [Abstract](1645) [HTML](144) [PDF 5.60 M](1210)
    Abstract:
    This paper analyzes the cause of the extremely heavy rainfall in northeastern Zhejiang induced by Typhoon ChanHom (1509) from 10 to 11 July 2015 by using conventional observation, AWS data, satellite and NECP reanalysis data. The results show that under the effect of the special terrain in northeast of Zhejiang, strong intensity and wild impaction of ChanHom meeting with the longtime northeast airflow contributed for this heavy rain process. During the early stage of the ChanHom impact, this area was in a state of convective instability. Besides, the abundant water vapor, lowlevel convergence and upperlevel divergence provided a beneficial condition for the heavy rainfall. In the rainstorm areas, the MPV1 changed from negative to positive at low level, leading to an increase of vertical vorticity. The longtime maintenance of the high θse energy region at 925 hPa also benefited the updraft. The longtime transportation of water vapor was not only favorable for ChanHom’s maintenance, but also beneficial to the formation of the heavy rainfall. There was a positive correlation of 6-12 h in advance for the increasing and decreasing of the heavy rainfall with the vapor transportation, surface convergence zone and θse at 925 hPa. And the special topography enhanced the heavy rainfall supported by the northeast airflow because of the effects of the upslope and terrain convergence, which were formed by the trumpetshaped terrain of Hangzhou Bay, Siming Mountain, elongated northeastsouthwest Xiangshan Harbor and its southern mountains.
    6  Analysis on Advective Transport Condition for Heavy Air Pollution Processes in Beijing During the 2013-2014 Winter Months and  Design of Transmission Weather Index
    HUA Cong ZHANG Hengde ZHANG Bihui
    2016, 42(3):314-321. DOI: 10.7519/j.issn.1000-0526.2016.03.006
    [Abstract](1291) [HTML](147) [PDF 2.89 M](1107)
    Abstract:
    Surface observation and air quality data are applied for the analysis of advective transport characteristics in Beijing during the 2013-2014 winter months with cluster analysis. Meanwhile, potential source contribution function (PSCF) is used for the analysis of potential source area. The results show that air masses which influence Beijing mainly come from southwest, east and northwest, and the probability for heavy pollution weather in southwest and east paths are 56.58% and 43.80% respectively, which indicates the two directions are typical pollutants transmission paths. It is also revealed that high PSCF values caused by underlying emission and small air mass velocity cover the western Shandong, central and southern Hebei, Tianjin and other places. These places are affected by air masses from southwest and east. Combined with emission intensity of PM2.5, transmission weather index is designed based on the former conclusions. It is found that the index is consistent with PM2.5 concentration, and has a forecast of about 6 hours in advance. Therefore, combining transmission weather index with weather analysis may lead to a better understanding of heavy air pollution and play a reference role in forecasting operation and assessment.
    7  Improvement of Mosaic Method for LAPS Radar Reflectivity and  Research on Filling Method for the “Cone of Silence”
    HAN Chengming LI Yaodong SHI Xiaokang
    2016, 42(3):322-329. DOI: 10.7519/j.issn.1000-0526.2016.03.007
    [Abstract](1150) [HTML](176) [PDF 3.22 M](775)
    Abstract:
    This paper aims at the problem of data gap when Local Analysis and Prediction System (LAPS) is merged with the raw data of new generation Doppler radar in China. Mosaic method of maximum value and distance index weights are designed for improving the original nearest neighbor algorithm in LAPS, and the reflectivity of “cone of silence” is simulated by the least square method. The results indicate that maximum value and distance index weight methods can make full use of multiple radar observed reflectivity, effectively improve the phenomenon of data gap between high elevations, and fill some grids in “cone of silence”, especially those in midtroposphere. The test of “cone of silence” reflectivity simulation by the least square method has certain effects and can simulate well the situation when observation data are enough around “cone of silence”. Thus, this research would improve the capacity of LAPS Doppler radar data assimilation, and the utilization efficiency of multiple radar observations, which would make positive effect on LAPS cloud analysis.
    8  Statistical Characteristics Analysis for AMDAR  Temperature Observation Error
    WANG Ruiwen WAN Xiaomin TIAN Weihong WANG Dan
    2016, 42(3):330-338. DOI: 10.7519/j.issn.1000-0526.2016.03.008
    [Abstract](1059) [HTML](72) [PDF 5.48 M](804)
    Abstract:
    Error structural characteristic of observation data is one of the most important factors that affect data assimilation. The error structural characteristics of observation data in GRAPES come from numerical weather prediction system abroad. In order to improve the application effect of aircraft meteorological data relay (AMDAR) data, statistical analysis of the temperature difference between AMDAR data and NCEP reanalysis data is done according to different latitude zones, flight states, and identifications. The AMDAR data is from realtime database in National Meteorological Information Centre (NMIC), and the period of time for the data is May-July 2013. The statistical results show that there is a maximum temperature bias in the midlatitude (20°-50°N) of Northern Hemisphere, where the number of AMDAR data is at most. The temperature bias is about -2--1℃, and the standard deviation of temperature is about 1.2-1.6℃. The temperature standard deviation varies with latitude zones in different flight states. The minimum standard deviation of temperature appears in cruise phase in the equatorial region (20°S-50°N), being about 0.8℃. The maximum standard deviation of temperature appears in cruise phase in the high latitude (50°-90°N) of the Northern Hemisphere, and it is about 1.5-2℃. By analyzing the error character of AMDAR data, we can do better in quality control and bias correction, improving the effect of data assimilation and forecasting.
    9  LongTerm Trends in Extreme Temperature over China  Mainland Based on Homogenized Dataset
    XIAO Bingshuang MA Yuxia ZHAO Tianbao YAN Shuhao
    2016, 42(3):339-346. DOI: 10.7519/j.issn.1000-0526.2016.03.009
    [Abstract](1584) [HTML](127) [PDF 1.56 M](934)
    Abstract:
    The world has become warmer over the past century, which is associated with the increase of hot days and warm nights, and the reduction of cool days and cold nights. Based on the homogenized daily temperature data from 542 Chinese stations during 1960-2012, this paper calculated the several extreme temperature indicators series, by dividing China into 8 subregions, and using percentile method of defining extreme high and low temperature threshold. Meanwhile, using timetrend analysis, we analyzed the spatiotemporal distribution and varying tendency features of extreme temperatures and the indices in China. The results show that with the global warming, the increasing trends of the minimum and the maximum temperature are all statistically significant over most regions of China, except in Southwest China, during the last 53 years, of which temperature increases most in Northeast China. The increase of seasonal extreme temperature is the most in winter, but the least in summer. Minimum temperature is significantly increased, so is the maximum temperature, but the increasing magnitude of the minimum temperature is higher than that of the maximum counterpart. The frequency of cold days and cold nights show a decreasing trend, while the warm nights and warm days has increased. The change of cold night index is most prominent, presenting the phenomenon of regional differences. These results can provide some reference for regional assessment and further researches.
    10  Numerical Simulation Research on Silver Iodide Cold Cloud Seeding
    LIU Xiang’e GAO Qian HE Hui JI Lei
    2016, 42(3):347-355. DOI: 10.7519/j.issn.1000-0526.2016.03.010
    [Abstract](1085) [HTML](92) [PDF 4.23 M](793)
    Abstract:
    Nnumerical simulation research on silver iodide (AgI) cold cloud seeding is conducted, focusing on the precipitation process that happened in North China from 9 to 11 May 2014. The WRF model coupled with silver iodide cold cloud catalytic module is used and the model parameter settings are based on actual artificial precipitation operations. The effect and mechanism of the precipitation are discussed and then two sensitivity tests on operation height and catalyst content are carried out. The results show that seeding appropriate catalyst content of AgI at about 5-6 km height and temperature of -20--15℃ can make ground precipitation increased significantly. Ground rain enhancement begins at about 30 minutes after seeding operation, and 70 minutes to reach the maximum, while rain reduction occurs after 90 minutes, and 110 minutes later the reduction of rain is more than the increase of rain. The main mechanism for precipitation is as follows. The AgI seeding makes the cold water content above〖JP2〗 the melting layer in cloud remarkably reduced, snow and ice content increased, and coalescence processes of rain and snow and rain capture cloud droplets enhanced. Increased snow crystals fall into the warm zone and melt into raindrops, then the rainfall significantly increases. Regarding the magnitude of microphysical processes, the snow particles’ melting is the main process leading to increased precipitation. Results of the two sensitivity tests show that the catalytic effects are better when seeding in clouds with rich supercooled cloud water, low temperature and low ice crystal content, and increasing the amount of catalyst could have better seeding result.
    11  Analysis of the Causes for the Difference of Rainstorm Intensity Design in Huangshi and Daye Cities
    FANG Yi CHEN Zhenghong SUN Pengjie CHEN Youjiao CHEN Cheng
    2016, 42(3):356-362. DOI: 10.7519/j.issn.1000-0526.2016.03.011
    [Abstract](904) [HTML](128) [PDF 992.57 K](997)
    Abstract:
    By using the minute rainfall data of Huangshi and Daye Cities which are located 20 km apart and according to the related standards, this paper calculates the parameters of the rainstorm intensity formula and analyzes the difference of the designed rainfall intensities in the two cities. The results show that in the return period of 0.5-100 years, the rainfall intensity of Huangshi in every period of time (5-120 min) is stronger than Daye’s, getting to 27.34%. Except the annual mean rainfall, the maximum annual rainfall, the maximum monthly rainfall, the maximum daily rainfall, the average annual rainstorm days in Huangshi are more than Daye’s. By analyzing the rainfall data, it is found that Huangshi has bigger average value of the the first maximum rainfall, for the other 7 second heaviest rainfalls, the values for Daye are larger than that for Huangshi. The standard deviation of Huangshi calculated by the first eight maximum precipitation amounts are about 1.4 times more than Daye’s. In short, these results show that the large rainfall in a short time is the cause for the design of the stronger rainfall intensity of Huangshi than Daye’s. The designed rainfall intensity is more sensitive to the first heaviest rainfall and the standard deviation.
    12  Quality Control Method for MultiSource Data of Surface Rainfall
    ZHANG Lejian YU Xiaoding LI Feng CHU Ling
    2016, 42(3):363-371. DOI: 10.7519/j.issn.1000-0526.2016.03.012
    [Abstract](1080) [HTML](137) [PDF 1.69 M](1177)
    Abstract:
    Based on the analysis of radar and automatic weather station (AWS) data, a quality control (QC) method for multisource data of surface rainfall is presented in this study. The QC methods include MRAWS which combines the radar and AWS data and MAWS which only uses AWS data. At the same time, the two methods are compared with the spatiotemporal QC method (MTS). The analysis results show that the performance of MRAWS and MAWS is significantly better than that of MTS, because MRAWS and MAWS are able to utilize more observational elements effectively. Although the result of MAWS is slightly worse than that of MRAWS due to the absence of radar data, MAWS is also an effective QC method for surface rainfall. But further analysis suggests that the methods of MRAWS and MAWS are likely to be applied only in judging whether rainfall occurs or not, for they are not good enough to evaluate the rainfall correctly.
    13  Analysis on the Characteristics of Meteorological Factors and  Forecast Ideas for Regional Advection Fog in Jiangxi
    XU Aihua CHEN Xiangxiang XIAO An XU Bin
    2016, 42(3):372-381. DOI: 10.7519/j.issn.1000-0526.2016.03.013
    [Abstract](1566) [HTML](94) [PDF 3.65 M](1786)
    Abstract:
    Based on the 2000-2012 conventional surface observations and sounding data in Jiangxi Province, this paper analyzed 54 regional advection fog weather events and meteorological factors by using the synthetic and statistical method, obtaining the statistical characteristics of the advection fog temperature inversion layer, temperature and humidity conditions, lowlevel wind field and the impact system. The results showed that: (1) The Jiangxi regional advection fog mainly occurs in February and March, seen more in the north than in the south. (2) The situation features are as follows: The lowlevel of Jiangnan Region has obvious warm and humidity advection, the shear line or convergence zone at 850 hPa is located in the region from Yangtze River to Jianghuai, the southwest wind speed at 925 hPa and 850 hPa is up to 3-8 m·s-1 and 7-15 m·s-1 respectively. Surface situation is mostly inverted trough and low pressure in the forepart of cold front, followed by the bottom of high pressure.(3) The relative humidity is ≥80% below 850 hPa, while it is ≤50% in the middle layer at 500 hPa. The surface air temperature and dew point range within 10-16℃, and the air is nearly saturated.(4) The advection fog mostly has single temperature inversion layer, whose inversion layer is higher and thicker than radiation fog. The intensity of temperature inversion is mainly between 1℃ and 3℃. Finally, the forecast focuses and forecast ideas of advection fog weather in Jiangxi (South China) are put forward.
    14  Analysis of the December 2015 Atmospheric Circulation and Weather
    LI Ming HUA Cong MA Xuekuan
    2016, 42(3):382-388. DOI: 10.7519/j.issn.1000-0526.2016.03.014
    [Abstract](1014) [HTML](66) [PDF 9.47 M](923)
    Abstract:
    The main characteristics of the general atmospheric circulation in December 2015 are as follows: There is one polar vortex center in the Northern Hemisphere, located near Greenland. The Eurasia midhigh latitude circulation presents the troughridgetrough pattern. The south branch trough behaves actively, lying around 90°E averagely. The subtropical high is stronger and has larger area than normal years. The monthly mean temperature over China is -2.1℃, 1.1℃ higher than normal (-3.2℃). The distribution of precipitation is inhomogeneous. Largescale rainy weather appears in the southern part of China. The monthly precipitation in the south of the Yangtze River and South China is 100-200 mm, and for the whole country it is 24.1 mm, 1.3 times more than normal (10.5 mm), which is the maximum value for the corresponding periods since 1951. There are three cold air processes, three major rainfall processes and two largescale foghaze weather processes during this month, of which the foghaze event from 19 to 25 December is characterized by long duration, large scale and heavy air pollution, and the haze affected area is the largest in 2015.

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