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A three-dimensional variational ocean data assimilation system:Scheme and preliminary results

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Science china Earth Sciences 2006年第11期49卷 1212-1222页

作者： ZHU Jiang1,2. ZHOU Guangqing1, YAN Changxiang1, FU Weiwei1 & YOU Xiaobao1,3.1. International Center for Climate and Environment Sciences, institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 10002.,{3. 2. Jiangsu Key Laboratory of Meteorological Disaster, {2. University of Information Science and Technology, nanjing 21004.,{3. 3. Beijing institute of Applied meteorology, Beijing 10002.,{3. 1. International Center for Climate and Environment Sciences Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China 2. Jiangsu Key Laboratory of Meteorological Disaster Nanjing University of Information Science and Technology Nanjing 210044 China 3. Beijing institute of Applied meteorology Beijing 100029 China

A new 3.VAR-based Ocean Variational Analysis System (OVALS) is developed. OVALS is capable of assimilating in situ sea water temperature and salinity observations and satellite altimetry data. As a component of OVALS, a new variational scheme is proposed to assimilate the sea surface height data. This scheme considers both the vertical correlation of background errors and the nonlinear temperature-salinity relationship which is derived from the generalization of the linear balance constraints to the nonlinear in the 3.VAR. By this scheme, the model temperature and salinity fields are directly adjusted from the altimetry data. Additionally, OVALS can assimilate the temperature and salinity profiles from the ARGO floats which have been implemented in recent years and some temperature and salinity data such as from expendable bathythermograph, moored ocean buoys, etc. A 2.-year assimilation experiment is carried out by using OVALS and the Tropical Pacific circulation model. The results show that the assimilation system may effectively improve the estimations of temperature and salinity by assimilating all kinds of observations. Moreover, the root mean square errors of temperature and salinity in the upper dept. less than 42. m reach 0.63. and 0.3. psu.

关键词： data assimilation, 3.VAR, sea surface height, ARGO floats.

Case studies on mesoscale structures of heavy rainfall system in the Yangtze River generated by Meiyu front

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Science china Earth Sciences 2005年第8期48卷 1303-1311页

作者： LIU Liping1, RUAN Zheng1 & QIN Danyu2.1. Chinese Academy of Meteorological Sciences, Beijing 100081, china 2.{3.,{2., china 1. Chinese Academy of Meteorological Sciences 100081 Beijing China 2. nanjing institute of meteorology 210044 Nanjing China

A heavy rainfall system was observed over the Yangtze River during Meiyu season by using dual-Doppler radar systems in the field experiment conducted by the project of National Fundamental Research Planning “Research on formation mechanism and the prediction theory of hazardous weather over china”. The three-dimensional mesoscale kinematic structure and process of a heavy rain on 2. and 2. July, 2.02.are investigated by using the radial velocity and dual-Doppler radar technique. The results show that a southwest-northeast oriented rain band with the length of about 1000 km involves numbers of meso-β or meso-γ-scale convective cells with the size of 2.―50 km. The heavy rain band in the middle reaches of the Yangtze River ex-ists in a low-level wind shear. The interaction between southwest low-level jet on the southern side of wind shear and east wind on the northern side formed the updraft. The wind disturbance, wind shear and convergence generate the convective action. The new cell developed in right rear flank of rain band and moved to the southwest wind area, where the vapor is abundant. This kind of echo can last a long time and developed well. The strong convective echoes are often ac-companied by the meso-γ-scale vortex and convergence.

关键词： heavy rainfall in Meiyu front, mesoscale structure, dual-Doppler radar, middle reaches of the Yangtze River, low-level jet.

Zonal propagation of kinetic energy and convection in the South china Sea and Indian monsoon regions in boreal summer

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Science china Earth Sciences 2004年第12期47卷 1076-1084页

作者： CHEN Longxun 1 ,GAO Hui 2.,HE Jinhai 2.,TAO Shiyan 3.& JIN Zuhui 3.1.Chinese Academy of Meteorological Sciences,Beijing 100081,china 2.nanjing {2. of meteorology,nanjing 21004.,china 3.{2. of Atmospheric Physics,Chinese Academy of Sciences,Beijing 10002.,china 1. Chinese Academy of Meteorological Sciences 100081 Beijing China 2. nanjing institute of meteorology 210044 Nanjing China 3. Chinese Academy of Sciences Institute of Atmospheric Physics 100029 Beijing China

Zonal propagation of kinetic energy (KE) and convection in the South china Sea (SCS) and Indian summer monsoon areas are examined in present study. Results suggest that the SCS and Indian summer monsoon prevailed regions (5 —15°N) are dominated by the southwesterly wind, however, the disturbances of KE at 850 hPa and convection are observed mainly coming from the western Pacific Ocean (140—150°E), after passing through the SCS, and westward propagated into the Bay of Bengal (90—100°E). In the Indian summer monsoon domain, where the disturbances of KE are found mainly coming from the Arabian Sea (AS) and eastward propagated into the Bay of Bengal. Therefore, the SCS and the Indian summer mon- soon are quite different in zonal propagation of KE and convection. The SCS summer monsoon is mainly affected by the KE and convection coming from the tropical western Pacific. The Indian summer monsoon, however, can be partly influenced by the AS and the SCS summer monsoon. The analysis also suggests that the interaction region between the SCS and the Indian summer monsoon is around 90—95°E, rather than 105°E as proposed by earlier studies.

关键词： zonal propagation of KE and convection, East Asian monsoon, Indian monsoon.

Annual precipitation fields secular variation over global land areas for 1948—2.00

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Chinese Science Bulletin 2003年第3期48卷 281-286页

作者： SHI Neng & CHEN Luweng Department of Atmospheric Sciences, nanjing institute of meteorology, nanjing 21004.,{2. Department of Atmospheric Sciences Nanjing Institute of Meteorology Nanjing 210044 China

The secular variation over the global land an-nual precipitation (GLAP) fields for 1948—2.00 is investi-gated. Evidence suggests that the GLAP abruptly reduced around 1978 and experienced a decrease of 0.54 mm/a, on average. Fuzzy clustering is used to group the annual pre-cipitation over commonly-used 3. latitudes belts into six belts for examining its secular variation. The results show that, except northern high-latitudes (60°—90°N) where it is slightly increased, the precipitation is decreased, especially in 3.°N—3.°S, and the diminution is the maximum of 0.98 mm/a at tropics. Moreover, identification of 1948—2.00 flood/drought years on a global basis is made, showing no-ticeable interdecadal variations. During the years of warm (cold) events the precipitation decreases (increases) by 15.4 mm (14.4 mm) per year, on average. It can be assumed that global warming and frequent ENSO occurrences from the end of the 1970s maybe serve as the root cause of the dimi-nution.

关键词：全球降水长期变化年降水 ENSO 陆地 1948-2.00年

Estimation of annual actual evapotranspiration from nonsaturated land surfaces with conventional meteorological data

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Science china Earth Sciences 2004年第3期47卷 239-246页

作者： QIU Xinfa1, ZENG Yan2. MIAO Qilong1 & YU Qiang2.1. Department of Geography, nanjing institute of meteorology,{3.,{2. 2. institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101,{2. nanjing Inst Meteorol Dept Geog Nanjing 210044 Peoples R China Chinese Acad Sci Inst Geog Sci Beijing 100101 Peoples R China Chinese Acad Sci Nat Resources Res Beijing 100101 Peoples R China

Views diverge greatly on the relationship between actual evapotranspiration (AE) and potential evapotranspiration (PE). Penman showed that AE is determined in intensity by PE and changes proportionally as a function of PE. In contrast, Bouchet indicated that AE deter-mines PE and varies inversely with PE. Based on nearly 3. years data from 43.0}weather stations and 512.hydrological stations in china, the two different theories, Penman抯 assumption and Bouchet抯 complementary relationship between AE and PE, were tested on nine river basins. With data integration technique, the complementary relationship between AE and PE was dis-played entirely. A general model to estimate the actual evapotranspiration from nonsaturated surfaces by routine meteorological observations has been established on the basis of thorough analysis of the concept of PE. The results show that the calculations are all in error control of <10%, except for a few years over the Yellow River Basin.

关键词： complementary relationship of evapotranspiration, potential evapotranspiration, actual evapotranspiration.

Possible mechanism of the effect of convection over Asian-Australian “land bridge” on the East Asian summer monsoon onset

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Science china Earth Sciences 2006年第11期49卷 1223-1232页

作者： HE Jinhai1, WEN Min2. DING Yihui3.& ZHANG Renhe2.1. Jiangsu Key Laboratory of Meteorological Disaster (KLME), nanjing institute of meteorology, {3. University of Informa- tion Science and Technology,{2., china 2. State Key Laboratory of Severe Weather (LaSW), Chinese Academy of Meteorological Sciences, Beijing 100081, china 3. National Climate Center, Chinese Meteorological Administration, Beijing 100081, china 1. Jiangsu Key Laboratory of Meteorological Disaster (KLME) Nanjing Institute of Meteorology Nanjing University of Information Science and Technology Nanjing 210044 China 2. State Key Laboratory of Severe Weather (LaSW) Chinese Academy of Meteorological Sciences Beijing 100081 China 3. National Climate Center Chinese Meteorological Administration Beijing 100081 China

The Asian-Australian “land bridge” is an area with the most vigorous convection in Asian monsoon region in boreal spring, where the onset and march of convection are well associated with the onset of East Asian summer monsoon. The convection occurs over Indo-china Peninsula as early as mid-April, which exerts critical impact on the evolution of monsoon circulation. Before mid-April there are primarily sensible heatings to the atmosphere over Indo-china Peninsula and Indian Peninsula, so the apparent heating ratios over them decrease with height. However, after mid-April it changes into latent heating over Indo-china Peninsula due to the onset of convection, and the apparent heating ratio increases with height in mid- and lower troposphere. The vertical distribution of heating ratio and its differences between Indo-china Peninsula and Indian Peninsula are the key factors leading to the splitting of boreal subtropical high belt over the Bay of Bengal. Such mechanism is strongly supported by the fact that the evolution of the vertical heating ratio gradient above Indo-china Peninsula leads that of 850 hPa vorticity over the Bay of Bengal. Convections over Indo-china Peninsula and its surrounding areas further increase after the splitting. Since then, there is a positive feedback lying among the convective heating, the eastward retreat of the subtropical high and the march of monsoon, which is a possible mechanism of the advance of summer monsoon and convection from Indo-china Peninsula to South china Sea.

关键词： Asian-Australian 'land bridge', tropical convection, Indo-china Peninsula, the splitting of boreal subtropical high belt, East Asian summer monsoon onset.

Numerical Analysis on Soil and Rock Formation of Ancient Gravel Strata Around nanjing

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Pedosphere 2001年第3期11卷 263-269页

作者： XIA JIA and CHEN XINMIN dept. of Civil Engineering, nanjing Architectural and Civil Engineering {2., nanjing 2.0009 (china) 南京航空航天大学江苏南京 210009

Research samples were taken from an ancient gravel stratum which is not only a representative soil layer along the middle-lower reaches of the Yangtze River in East china, but also one of the primary Neozoic strata in Naming district. Located mostly on the second and third terraces, the ancient gravel strata formed the geomorphic landscapes of terrace and step. They were complex in constitution, varied widely in stability, of multiple sources, locally derived, and associated with braided streams in the deposition environment. A CIPW (Cross, Iddings, Pirsson and Washington) method modified by the author was used to analyze the soil-rock-forming materials of finer grains (less than 2.mm in size) of the ancient gravel stratum. Results of the analysis showed that the sandy grains were composed of apatite, ilmenite, potassium feldspar, plagioclase, enstatite and free quartz, the clay mainly of kaolinite, and the cement of a combination of silicon, aluminum and iron at a ratio of 46:44:10. In the soil-rock-forming processes, including compactional solidification, water-stable illuviation-cementation t homogeneous overgrowth and so on, the loose soil-rock-forming components gradually changed into consolidated soil and further to the early stage of lithification. Meanwhile, from the analysis, we found that the ancient gravel stratum had been protected by the overlying Xiashu loess or basalt and the overloading resulted in overconsolidated strata. The modified CIPW method was applicable and effective for semi-quantitative analysis.

关键词： ancient gravel stratum numerical analysis soil-rock-forming processes

EXPLICIT SIMULATION ON THE TRACK AND INTENSITY OF TROPICAL CYCLONE WINNIE (1997)

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Journal of Hydrodynamics 2006年第6期18卷 736-741页

作者： ZHONG Zhong ZHANG Jirl-shan institute of meteorology PLA University of Science and Technology Nanjing 211101 China nanjing Hydraulic Research institute Nanjing 210029 China

An explicit simulation of the tropical cyclone Winnie （1997） was conducted by use of a triply-nested 3.D nonhydrostatic mesoscale model MM5, before and after its landfall. The simulated results show that the model can well reproduce the track of Winnie （1997） with a BOGUS storm-like vortex inserted in the large-scale first-guess field at the initial model time. The mean track error in a 6 h interval is 54.5 km, which is much less than that obtained with the operational prediction. Comparisons between simulation and observation near the landfall place show that the main temporal variation features of sea level pressure and surface wind speed can also be successfully captured. The characteristics of the eyewall, the spiral cloud band and the corresponding precipitation were disclosed, and the applications of the model outputs were also discussed.

关键词： tropical cyclone simulation track intensity,eyewall spiral cloud band storm surge

Influence of interannual variability of Antarctic oscillation on mei-yu along the Yangtze and Huaihe River valley and its importance to prediction

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Chinese Science Bulletin 2003年第S2期48卷 61-67页

作者： GAO Hui~(1,2., XUE Feng~1 WANG Huijun~1 1. institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 10002.,{3. 2. Department of Atmospheric Sciences,{2., nanjing 21004..{3. Chinese Acad Sci Inst Atmospher Phys Beijing 100029 Peoples R China nanjing Inst Meteorol Dept Atmospher Sci Nanjing 210044 Peoples R China

Both correlation analysis and case study indi-cate that Antarctic oscillation (AAO) is closely related withsummer rainfall in eastern china. When AAO is stronger inboreal spring, especially in May, there is more mei-yu rain-fall in summer with a longer period along the Yangtze andHuaihe River valley. In contrast, there is less rainfall with ashorter period corresponding to a weaker AAO. Besides, ananomalous AAO changes the position and intensity of severalcirculation systems, which are important to summer rainfallalong the Yangtze and Huaihe River valley. Furthermore, theAntarctic sea ice is negatively correlated with the intensity ofAAO with a 6-month leading time. The result in this studyprovides a new method for the prediction of mei-yu.

关键词： Antarctic oscillation interannual variability mei-yu Antarctic sea ice.