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Numerical simulations of the bi-level and branched structure of intracloud lightning flashes

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Science china Earth sciences 2006年第6期49卷 661-672页

作者： TAN Yongbo1, TAO Shanchang1, ZHU Baoyou1, MA Ming2.& LU Weitao2.1. School of Earth and Space sciences, University of Science and Technology of china, Hefei 2.002., china 2. chinese academy of meteorological sciences, beijing 100081, china 1. School of Earth and Space sciences University of Science and Technology of China Hefei 230026 China 2. chinese academy of meteorological sciences Beijing 100081 China

Intracloud (IC) lightning flashes have been simulated in fine resolution (12.5 m) by using a bidirectional stochastic lightning parameterization scheme within 2.dimensional domain. The simu-lated results show that the IC flashes have a bilevel channel structure and the altitudes of the hori-zontal channels are at the same heights of potential wells, which are supported by the previous VHF source observations and balloon soundings of electric field profile in the thundercloud. Further con-clusions are: (1) After an IC flash is initiated near the boundary between positve and nagetive charge zone, the negative (or positive) leader tends to propagate into the positive (or negative) charge zone. Both types of positive and negative IC flashes have been reproduced and their polarity depends on the up and down disposition of the positive and negative charge regions. (2. The extension range of leaders is correlative with the cloud charge distribution. The leader is possible to extend through the inverted charge region all over where it is extending, but keeps away from the isolated charge area of the same polarity. (3) The channel structures also depend on the electric potential distributions in the thundercloud. Before propagating into the central area of potential wells, the leader tends to extend along the direction with the maximum of potential gradient. Once extending away from the center of potential wells, the leader tends to extend along the direction with the slowest potential change. (4) The IC flash channels have the fractal feature with fractal dimension 1.45 before leaders pass through the central area of charge regions. The exponent decreases rapidly once leaders extend into the low-density charge regions. (5) The induced charges of opposite polarity are deposited in the leader channels within preexisting positive and negative charge regions during IC flash discharges. This causes a new and complicated charge distribution in the thundercloud, and the potential

关键词： IC, lightning parameterization, branched bilevel structure, fractal feature, propagation tendency.

热带西太平洋大气气候基本态与厄尔尼诺期间赤道附近西风异常

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海洋学报 2002年第2期24卷 39-50页

作者：严邦良张人禾中国科学院大气物理研究所北京100080 中国气象科学研究院北京100081

利用合成分析的方法分析了自1961年以来观测到的8次厄尔尼诺事件中赤道西太平洋地区西风异常与大气气候基本态的关系,结果发现厄尔尼诺年赤道西太平洋地区西风异常具有和大气气候基本态相一致的季节变化特征.利用一个简单热带海-气耦合... 详细信息

利用合成分析的方法分析了自1961年以来观测到的8次厄尔尼诺事件中赤道西太平洋地区西风异常与大气气候基本态的关系,结果发现厄尔尼诺年赤道西太平洋地区西风异常具有和大气气候基本态相一致的季节变化特征.利用一个简单热带海-气耦合模式较好地模拟出了观测到的厄尔尼诺年赤道西太平洋地区西风异常的变化特征.对模式结果的分析表明,大气气候基本态对厄尔尼诺年赤道西太平洋地区西风异常的形成起重要作用,它是通过影响大气模式中的加热场来影响赤道西太平洋地区西风异常.大气模式中赤道太平洋地区的加热场的形成具有阶段性和地区性,在厄尔尼诺事件的初始阶段,大气气候基本态是大气模式中的加热场形成的主要因子,而在厄尔尼诺事件的发展和成熟阶段,赤道中东太平洋地区的海表温度异常（SSTA）是加热场形成的主要因子.模式模拟结果对大气气候基本态依赖的敏感性试验说明,在大气模式加热场中含有大气气候基本态的模拟中,沿中西太平洋赤道附近的纬向风异常表现出和观测类似的传播特征.

关键词：厄尔尼诺事件海气耦合模式大气气候基本态太平洋西风异常

Teleconnection between the Indian summer monsoon onset and the Meiyu over the Yangtze River Valley

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Science china Earth sciences 2008年第7期51卷 1021-1035页

作者： LIU YunYun1,2.3 & DING YiHui2.1 chinese academy of {2. sciences, beijing 100081, china 2.National Climate Center, beijing 100081, china 3 Graduate University of chinese academy of sciences, beijing 100049, china 1. chinese academy of {2. sciences Beijing 100081 China 2. National Climate Center Beijing 100081 China 3. Graduate University of chinese academy of {2. Beijing 100049 China

Based on the Indian and chinese precipitation data and the NCEP-NCAR reanalysis circulation data, the relationship between the Indian summer monsoon (ISM) onset and the Meiyu over the Yangtze River Valley has been discussed by the methods of correlation analysis and composite analysis. The results show that the date of ISM onset over Kerala in the southwestern coast of the Indian Peninsula is about two weeks earlier than the beginning of the Meiyu over the Yangtze River Valley. After the outbreak of ISM, the teleconnection mode sets up from the western coast of India via the Bay of Bengal (BOB) to the Yangtze River Valley and southern Japan. It is different both in time and space from the telecon- nection mode which is from the northwest of India via the Tibetan Plateau to northern china. The for- mer mode is defined as the "south" teleconnection of the Asian summer monsoon, forming in the pe- riod of ISM onset; while the latter mode is called the "north" teleconnection, mainly occurring in the Asian monsoon culminant period. During the process of the "south" teleconnection’s formation, the Asian monsoon circulation has experienced a series of important changes: ISM onset, the northward movement of the south Asia high (SAH), the onset vortex occurrence, the eastward extension of the stronger tropical westerly belt, and the northeastward jump of the western Pacific subtropical high (WPSH), etc. Consequently, since ISM sets up over Kerala, the whole Asian continent is covered by the upper SAH after about two weeks, while in the mid- and lower troposphere, a strong wind belt forms from the Arabian Sea via the southern India, BOB and the South china Sea (SCS), then along the western flank of WPSH, to the Yangtze River Valley and southern Japan. With the northward moving of the subtropical jet streams, the upper westerly jet stream and the low level jet have been coupled ver- tically over east Asia, while the Yangtze River Valley happens to locate in the ascending motion

关键词： Indian summer monsoon (ISM) the Meiyu over the Yangtze River Valley teleconnection mode

Persistent anomalous flows over the subtropical western Pacific insummer

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chinese Science Bulletin 1998年第8期43卷 672-675页

作者： ZHUANG Shiyu\+1 and JI Liren\+2.1. National meteorological Centre, china meteorological Administration, beijing 100081, china 2. LASG, Institute of Atmospheric Physics, chinese academy of sciences, beijing 100080, china National meteorological Ccntre China Meteomlcgical Administration Beijing China LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China

The distribution of global persistent anomalies shows that the subtropical western Pacific is a key region with high_frequency occurrence of persistent anomalies. Analyses of streamfunction anomalies, OLR anomalies etc. suggest that the convective heating related to Indian monsoon might be responsible for the development of WPA. The results of numerical experiment by two linear barotropic models support the observation.

关键词： persistent anomalies subtropical high Indian monsoon anomalous forcing.

Interannual variation of annual precipitation and urban effect on precipitation in the beijing region

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Progress in Natural Science:Materials International 2007年第9期17卷 1042-1050页

作者： Yu Shuqiu(State Key Laboratory on Severe Weather,chinese academy of {2. sciences,beijing 100081,china) State Key Laboratory on Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081， China

The large scale character of the interannual variation of precipitation and the urban effect on local annual precipitation anomaly are investigated in this paper based on the 1960-2.00 annual precipitation observations at 2. stations in the beijing *** results show that:the annual precipitation in the beijing region possesses the large scale variation character with the linear trend of-1.197/10 yr,which corresponds to a total reduction of 2..82.mm in annual precipitation in the 41 years;the local annual precipitation anomalies(percent of the normal 1960-2.00)show a positive center near the urban area,*** precipitation island(UPI),whose intensity increases with the linear trend of 0.662.%/10 yr,opposite to the interannual trend of large scale precipitation over the beijing region;changes in the UPI are also associated with the intensity of synoptic processes of precipitation,and when the synoptic processes are strong(wet years),the intensity of UPI strengthens,while the synoptic processes are weak(dry years),and the UPI disappears in the beijing region.

关键词： urban precipitation island effect interannual climate variation precipitation beijing atmospheric science

Relationship between the Asian-Pacific oscillation and the tropical cyclone frequency in the western North Pacific

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Science china Earth sciences 2008年第3期51卷 380-385页

作者： ZHOU BoTao1, CUI Xuan2.& ZHAO Ping3 1 Laboratory for Climate Studies, National Climate Center, china meteorological Administration,{2., china 2.National meteorological Center, china meteorological Administration,{2., china 3 chinese academy of meteorological {12., china meteorological Administration,{2., china 1. Laboratory for Climate Studies National Climate Center China Meteorological Administration Beijing 100081 China 2. National meteorological Center China Meteorological Administration Beijing 100081 China 3. chinese academy of {2. sciences China Meteorological Administration Beijing 100081 China

The relationship between the Asian-Pacific oscillation (APO) and the tropical cyclone frequency over the western North Pacific (WNP) in summer is preliminarily investigated through an analysis of ob- served data. The result has shown clearly that APO is significantly and positively correlated to the tropical cyclone frequency in the WNP. If APO is above (below) the normal in summer, more (less) tropical cyclones will tend to appear in the WNP. The present study also addresses the large-scale at- mospheric general circulation changes underlying the linkage between APO and the WNP tropical cy- clone frequency. It follows that a positive phase of summer APO is concurrent with weakened as well as northward and eastward located western Pacific subtropical high (WPSH), low-level convergence and high-level divergence, and reduced vertical zonal wind shear in the WNP, providing favorable envi- ronment for the tropical cyclone genesis, and thus more tropical cyclones will come into being, and vice versa.

关键词： Asian-Pacific oscillation western North Pacific tropical cyclone atmospheric circulation

An integrative estimation model of summer rainfall-band patterns in china

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Progress in Natural Science:Materials International 2007年第3期17卷 280-288页

作者： WEI Fengying (State Key Laboratory of Severe Weather, chinese academy of {2. sciences, beijing 100081, china) State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China

Three variation indices are defined to objectively and quantitatively represent fluctuations of three rainfall-band patterns in summers in china for the period from 1951 to 2.05, and the variation features of these indices are analyzed on both of interdecadal and interannual scales. A new method is proposed to establish an integrative estimation model based on the analysis of rainfall-band indices, and the model is applied to air, ocean factors to estimate their roles on variations of three rainfall-band patterns on different time-scales. The tests of estimation effects show that the fluctuations of three rainfall-band patterns are composed of variations on both significant inter-decadal and interannual scales, of which the interannual variation is mainly influenced by the Elnino/Lanina events, the East Asia monsoon and the ridge locations of subtropical high pressures in western pacific, while the interdecadal variation is mainly controlled by the Pacific decadal oscillation and interdecadal oscillations of the Arctic oscillation, ENSO, Nino3 sea surface temperature and summer monsoon. The estimated results from the integrative estimation model of rainfall-band patterns suggest that the way of estimation first according to each time scale of both the interdecadal and interannual scales, then estimating with an integration, which is proposed in this paper, has an obvious improvement on that without separation of time scales.

关键词： rainfall-band pattern interannual variation interdecadal variation integration estimation model.

Current status and future of acid rain in china

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chinese Science Bulletin 1997年第24期42卷 2076-2081页

作者： DING Guo’an, XU Xiaobing, FANG Xiumei, JIN Shaping, XU Xia, Tang Jie, LIU Qijun, WANG Shufeng and WANG Wenxing1. chinese academy of {2. sciences, beijing 100081, china 2. chinese academy of Environment sciences, beijing 100012. china chinese academy of {2. sciences Beijing 100081 China

As a part of the national key project of acid rain research, chemical element analysis of rainwater has been carried out based on observation of acid rain network in chinese meteorologicalAdministration over the years of 1992.and 1993. Samples of precipitation collected from eachacid rain station were taken according to the standard established by chinese meteorologicalAdministration. pH value was measured with pH meter (accuracy of 0. 01) made in

关键词： acid rain current status future.

Numerical experiments for the impacts of temperature and precipitation variation on the growth and development of winter wheat

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Journal of Environmental sciences 1993年第2期5卷 194-200页

作者： Zhang YuAgrometeorological Research Center, chinese {2. of meteorological sciences, beijing 100081, china Agrometeorological Research Center Chinese Academy of Meteorological Sciences Beijing 10081 China. China

The growth process of winter wheat was simulated by CERES-wheat model assuming the daily temperature increase -1, 0,1, 2. and daily precipitation increase -2., -10, -5, 0, 5, 10, and 2. percent, respectively. The case study site is Zhenjiang City of Jiangsu Province in the east china. Simulation results show that the impacts of temperature variation on winter wheat is stronger than that of precipitation. Climate warming would speed development rate and shorten phonological period. In general, the adverse effect of climate change on grain yield is greater than that of its beneficial effect, especially when the climate becoming cooler and dryer. The increase of temperature and decrease of precipitation would reduce the plant extractablc soil water content.

关键词： climate change winter wheat CERES-wheat model.