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Urban effects and summer thunderstorms in a tropical cyclone affected situation over Guangzhou city

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Science China Earth Sciences 2007年第12期50卷 1867-1876页

作者： MENG WeiGuang1,3,YAN JingHua1 & HU HaiBo2 1 Institute of Tropical and Marine Meteorology,Chinese Meteorological Administration(CMA),Guangzhou 510080,China 2 Institute of Urban Meteorology,CMA,Beijing 100089,China 3 State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences,Beijing 100081,China Institute of Tropical and Marine Meteorology Chinese Meteorological Administration (CMA) Guangzhou China State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing China Institute of Urban Meteorology CMA Beijing China

With data mainly from Guangzhou mesonet Automatic Weather Stations(AWS),Guangzhou Doppler Radar and satellite TBB data,characteristics and evolution of the urban heat island(UHI) over Guang-zhou City were analyzed in a tropical cyclone affected situation for early August 2005.In particular,two thunderstorms occurring during this period respectively at the night of 4 August and in the afternoon of 7 August were investigated to study the relationships between the development of thunderstorms and the UHI.Results showed that two thunderstorms were associated with the UHI effects.UHI induced local air convergence and initiated the thunderstorm convections.Both cases showed a general agreement in time and space for the locations of maximum UHI,convergence,convection,and pre-cipitation.Convection was found to be more favorable to developing in time periods and locations with stronger intensity of UHI.Analysis also showed that,due to the urban effects,both thunderstorms got strengthened when moving over Guangzhou City,with maximum radar echoes observed right over the urban area and precipitation located within the city.All these features reveal that two thunderstorms were urban-induced storms.

关键词： summer thunderstorms, urban heat islands (UHI), urban effects, tropical cyclone

Options for reducing the negative effects of nitrogen in agriculture

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Science China(Life Sciences) 2005年第Z2期48卷 861-870页

作者： J.R.Freney CSIRO Plant Industry G.P.O.Box 1600 CanberraA.C.T.2601Australia

After addition to farms by fertilizer, crop residues, biological fixation and animal excreta, nitrogen can be lost through gaseous emission, runoff and leaching to contaminate the atmosphere and water bodies, and cause adverse health effects. The efficiency of fertilizer hitrogen can be increased and losses reduced, by matching supply with crop demand, optimizing split application schemes, changing the form to suit the conditions, and use of slow-release fertilizers and inhibitors. In addition, agronomic practices such as higher plant densities, weed and pest control and balanced fertilization with other nutrients can also increase efficiency of nitrogen use. Efficiency of use by animals can be increased by diet manipulation. Feeding dairy cattle low degradable protein and high starch diets, and grazing sheep and cattle on grasses high in water soluble carbohydrate result in less nitrogen excretion in urine and reduced ammonia volatilization.

关键词： options for reducing the negative effects, nitrogen in agriculture.

Evolution of the Ordos Plateau and environmental effects

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Science China Earth Sciences 2007年第Z2期50卷 19-26页

作者： YUE LePing LI JianXing ZHENG GuoZhang LI ZhiPei State Key Laboratory of Continental Dynamics (Northwest University) Geology Department Northwest University Xi'an 710069 China State Key Laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences(CAS)Xi'an 710075 China State Key Laboratory of Continental Dynamics(Northwest University) Geology Department Northwest University Xi'an 710069 China Xi'an Institute of Geology and Mineral Resources Xi'an 710054 China College of Urban and Environment Science Shanxi Normal University Linfen 041004 China Xi'an Institute of Geology and Mineral Resources Xi'an 710054 China

Based on the analysis of temporary-spatial distribution, geomorphic position, contact relationship with underlying strata and grain size of red clay, we studied the formation and environmental background of red clay. During late Miocene-Pliocene, the Ordos Block finished the transformation from the basin to the plateau, which had an obvious environmental effect on the topography, indicated by the formation of highland undergoing wind erosion and lowland receiving red clay deposits. The red clay materials were sourced from dusts carried by wind energy and covered on the initial topography. Unlike Quaternary loess dust covering the overall the Loess Plateau, red clay deposited on the highland would be transported to the lowlands by wind and fluvial process. As a result, there was no continuous "Red Clay Plateau" in the Ordos region and red clay was only preserved in former lowlands. However, red clay was discontinuously distributed through the Loess Plateau and to some extent modified the initial topography. The differential uplift in interior plateau is indicated by the uplift of northern Baiyushan, central Ziwuling and southern Weibeibeishan. The Weibeibeishan Depression formed earlier and became the sedimentary center of red clay resulting in the thicker red clay deposits in Chaona, Lingtai and Xunyi. Since Quaternary the aridity in the northern plateau enhanced and accelerated loess accumulation caused the formation of the Loess Plateau. During the late Pleistocene the rapid uplift led to the enhancement of erosion. Especially after the cut-through of Sanme Lake by the Yellow River, the decline of base level caused the falling of ground water level and at the same time the increase of drainage density resulting in the enhancement of evaporation capacity, which enhanced the aridity tendency of aridity in the Loess Plateau region.

关键词： the Ordos Plateau, environmental effects, red clay-loess

Thermal-mechanical coupled effect on fracture mechanism and plastic characteristics of sandstone

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Science China(Technological Sciences) 2007年第6期50卷 833-843页

作者： ZUO JianPing1,2, XIE HePing2,3, ZHOU HongWei1,2 PENG SuPing1 1 State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083, China 2 Institute of Rock Mechanics and Fractals, China University of Mining and Technology, Beijing 100083, China 3 Sichuan University, Chengdu 610065, China State Key Laboratory of Coal Resources and Safe Mining China University of Mining and Technology Beijing China Institute of Rock Mechanics and Fractals China University of Mining and Technology Beijing China Sichuan University Chengdu China

Scanning electronic microscopy (SEM) was employed to investigate fractographs of sandstone in mine roof strata under thermal-mechanical coupled effect. Based on the evolution of sandstone surface morphology in the failure process and frac- tography, the fracture mechanism was studied and classified under meso and mi- cro scales, respectively. The differences between fractographs under different tem- peratures were examined in detail. Under high temperature, fatigue fracture and plastic deformation occurred in the fracture surface. Therefore, the temperature was manifested by these phenomena to influence strongly on micro failure mechanism of sandstone. In addition, the failure mechanism would transit from brittle failure mechanism at low temperature to coupled brittle-ductile failure mechanism at high temperature. The variation of sandstone strength under differ- ent temperature can be attributed to the occurrence of plastic deformation, fatigue fracture, and microcracking. The fatigue striations in the fracture surfaces under high temperature may be interpreted as micro fold. And the coupled effect of tem- perature and tensile stress may be another formation mechanism of micro fold in geology.

关键词： sandstone, thermal-mechanical coupled effects, fractograph, plastic deformation, SEM, micro fold

Identifiability of causal effect for a simple causal model

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Science China Mathematics 2002年第3期45卷 335-341页

作者：郑忠国童行伟张艳艳 Dept. of Probability and Statistics Peking University Beijing 100871 China Tianjin Normal University Tianjin 301700 China

Counterfactual model is put forward to discuss the causal inference in the directed acyclic graph and its corresponding identifiability is thus studied with the ancillary information based on conditional independence. It is shown that the assumption of ignorability can be expanded to the assumption of replaceability,under which the causal efiects are identifiable.

关键词： directed acyclic graph, intervention, causal effects, ancillary information, ignorability,replaceability.

The atomic structure and the properties of Ununbium (Z=112) and Mercury (Z=80)

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Science China(Physics,Mechanics & Astronomy) 2007年第6期50卷 707-715页

作者： S.FRITZSCHE B.FRICKE Institut fr Physik Universita..t Kassel 34132Germany

A super heavy element Uub (z = 112) has been studied theoretically in conjunction with rela-tivistic effects and the effects of electron correlations.The atomic structure and the oscillator strengths of low-lying levels have been calculated,and the ground states have also been determined for the singly and doubly charged ions. The influence of relativity and correlation effects to the atomic properties of such a super heavy element has been investigated in detail. The results have been compared with the properties of an element Hg. Two energy levels at wave numbers 64470 and 94392 are suggested to be of good candidates for experimental observations.

关键词： super heavy element, atomic structure, relativistic effects, electron correlation effects, MCDF method A super heavy element Uub (Z = 112) has been studied theoretically in conjunction with rela-tivistic effects and the effects of electron correlations. The atomic structure and the oscillator strengths of low-lying levels have been calculated, and the ground states have also been determined for the singly and doubly charged ions. The influence of relativity and correlation effects to the atomic properties of such a super heavy element has been investigated in detail. The results have been compared with the properties of an element Hg. Two energy levels at wave numbers 64470 and 94392 are suggested to be of good candidates for experimental observations.……

Seasonal patterns and environmental control of ecosystem respiration in subtropical and temperate forests in China

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Science China Earth Sciences 2005年第Z1期48卷 93-105页

作者： YU Guirui, WEN Xuefa, LI Qingkang, ZHANG Leiming, REN Chuanyou, LIU Yunfen & GUAN Dexin Chinese Ecosystem Research Network Synthesis Research Center, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China Graduate School of the Chinese Academy of Sciences, Beijing 100039, China Chinese Ecosystem Research Network Synthesis Research Center Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Chinese Ecosystem Research Network Synthesis Research Center Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China

Continuous measurement of carbon dioxide exchange using the eddy covariance (EC) technique was made at two ChinaFLUX forest sites including the young subtropical Pinus plantation (Qianyanzhou) and old temperate broad-leaved Korean pine mixed forest (Changbai Mountains) as part of the ChinaFLUX network. Seasonal patterns and environmental control of ecosystem respiration in the subtropical and temperate forests were evaluated by the often-used multiplicative model and Q10 model as a function of temperature and soil water content. The resuits suggested that ( i ) temperature was found to be a dominant factor in the ecosystem respiration, and most of the temporal variability of ecosystem respiration was explained by temperature. However, in the drought-stressed ecosystem, soil water content controlled the temporal variability of ecosystem respiration other than temperature effects, and soil water content became a dominat factor when severe drought affected the ecosystem respiration; (ii) the regression models analysis revealed that in the drier soil, ecosystem respiration was more sensitive to soil moisture than was expressed by the often-used multiplicative model. It was possible to accurately estimate the seasonal variation of ecosystem respiration based on the Q10 model; and (iii)annual ecosystem respiration derived from the often-used multiplicative model was 1209 g C m-2and 1303 g C m-2, and was consistently a little higher than the Q10 model estimates of 1197 g C m-2 and 1268 g C m-2 for Qianyanzhou and Changbai Mountains, respectively.

关键词： ChinaFLUX, eddy covariance, Q10, drought effects, temperature effects.