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Application of LICOM to the numerical study of the water exchange between the South China Sea and its adjacent oceans

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Acta Oceanologica Sinica 2005年第4期24卷 10-19页

作者： CAI Shuqun LIU Hailong LI Wei LONG Xiaomin key laboratory of Tropical Marine Environmental dynamics （LED） South China Sea Institute of Oceanology Chinese Academy of Sciences Guangzhou 510301 China state key laboratory of numberical modelling for atmospheric sciences and geophysical fluid dynamics （lasg） Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

On the basis of 900-year integration of a global ocean circulation model-LICOM driven by ECMWF reanalysis wind data with uniform 0.5°-grids, a quantitative estimate of the annual and monthly mean water exchange of the South China Sea （SCS） with its adjacent oceans through 5 straits is obtained. Among them, the annual transport is the largest in the Luzon Strait, then in the Taiwan Strait, and then in the Sunda Shelf, in the Balabac Strait and in the Mindoro Strait in turn, the largest monthly transport variation appears in the Luzon Strait and Sunda shelf. It is shown that the mass transport through the Taiwan Strait is affected by monsoon, while the transport through the Luzon Strait may be associated with the bifurcation position of the North Equatorial Current off the east Philippines shore; the transports in the Luzon Strait and Sunda Shelf are out of phase in direction but well correlated in magnitude. The annual and monthly mean heat and salinity exchange of the SCS through the straits are also calculated and shown to be in phase with the mass transport. The Kuroshio water carries about 0.43 PW heat transport and 151.33 kt/s salinity transport into the SCS, while most of them is carried out of the SCS through the Taiwan Strait and Sunda Shelf annually. The further model integration based on the 900-year integration for another 44 a from 1958 to 2001 driven by real wind data （ERA40 data） shows that the monthly mean mass transport via these straits varies annually with a large variation range, which may be associated with the seasonal and interannual variations in the current field and sea surface height in the SCS. The mean mass transport through the Taiwan Strait, Luzon Strait, Mindoro Strait, Balabac Strait and Sunda Shelf is 2.012×10^6, -4.063×10^6, -0.124×10^6, -0.083×10^6 and 2.258×10^6 m^3/s, respectively.

关键词： mass transport heat transport salinity transport numerical model South China Sea

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Computational uncertainty principle in nonlinear ordinary differential equations (I)——Numerical results

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Science China(Technological sciences) 2000年第5期43卷 449-460,561页

作者：李建平曾庆存丑纪范 state key laboratory of Numerical modelling for atmospheric sciences and geophysical fluid dynamics (lasg) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Department of atmospheric sciences Lanzhou University Lanzhou 730000 China

In a majority of cases of long-time numerical integration for initial-value problems, roundoff error has received little attention. Using twenty-nine numerical methods, the influence of round-off error on numerical solutions is generally studied through a large number of numerical experiments. Here we find that there exists a strong dependence on machine precision (which is a new kind of dependence different from the sensitive dependence on initial conditions), maximally effective computation time (MECT) and optimal stepsize (OS) in solving nonlinear ordinary differential equations (ODEs) in finite machine precision. And an optimal searching method for evaluating MECT and OS under finite machine precision is presented. The relationships between MECT, OS, the order of numerical method and machine precision are found. Numerical results show that round-off error plays a significant role in the above phenomena. Moreover, we find two universal relations which are independent of the types of ODEs, initial values and numerical schemes. Based on the results of numerical experiments, we present a computational uncertainty principle, which is a great challenge to the reliability of long-time numerical integration for nonlinear ODEs.

关键词： ordinary differential equations (ODEs) computational uncertainty principle round-off error discretization error strong dependence on machine precision maximally effective computation time (MECT) optimal stepsize (OS) universal relation no

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Significance of the normalized seasonality of wind field and its rationality for characterizing the monsoon

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Science China Earth sciences 2000年第6期43卷 646-653页

作者：李建平曾庆存 state key laboratory of Numerical modelling for atmospheric sciences and geophysical fluid dynamics (lasg) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Correspondence should be addressed to Li Jianping

The significance of the normalized seasonality of wind field is theoretically studied and the intrinsic relationship between its critical value and the definition of the monsoon region is revealed. As a result, the rationality which the monsoon region is characterized by the significant normalized seasonality is proved. Based on this, by use of the NECP/NCAR reanalysis data during 1958-1997, the spatial structure of the significant normalized seasonality of wind field is investigated, and the significant baroclinity of the seasonal variation of the atmospheric general circulation in the vertical direction is verified. Moreover, in the tropics there exists an anti-symmetric distribution between the significant seasonality in the eastern hemisphere and that in the western hemisphere, and the monsoon is linked closely to some important systems such as the subtropical highs, the night jet and the west wind channels.

关键词： normalized seasonality monsoon monsoon region significance baroclinity western hemisphere tropical monsoon.

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Computational uncertainty principle in nonlinear ordinary differential equations——Ⅱ.Theoretical analysis

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Science China(Technological sciences) 2001年第1期44卷 55-74页

作者：李建平曾庆存丑纪范 1. state key laboratory of Numerical modelling for atmospheric sciences and geophysical fluid dynamics (lasg) Institute of Atmospheric Physics Chinese Academy of Sciences 100029 Beijing China 2. Department of atmospheric sciences Lanzhou University 730000 Lanzhou China

The error propagation for general numerical method in ordinarydifferential equations ODEs is studied. Three kinds of convergence, theoretical, numerical and actual convergences, are presented. The various components of round-off error occurring in floating-point computation are fully detailed. By introducing a new kind of recurrent inequality, the classical error bounds for linear multistep methods are essentially improved, and joining probabilistic theory the “normal” growth of accumulated round-off error is derived. Moreover, a unified estimate for the total error of general method is given. On the basis of these results, we rationally interpret the various phenomena found in the numerical experiments in part I of this paper and derive two universal relations which are independent of types of ODEs, initial values and numerical schemes and are consistent with the numerical results. Furthermore, we give the explicitly mathematical expression of the computational uncertainty principle and expound the intrinsic relation between two uncertainties which result from the inaccuracies of numerical method and calculating machine.

关键词： computational uncertainty principle round-off error discretization error universal relation ma-chine precision maximally effective computation time (MECT) optimal stepsize (OS) convergence.

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Consistency Problem with Tracer Advection in the atmospheric Model GAMIL

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Advances in atmospheric sciences 2008年第2期25卷 306-318页

作者：张恺万慧王斌张美根 state key laboratory of Numerical Modeling for atmospheric sciences and geophysical fluid dynamics (lasg) Institute of Atmospheric Physics. Chinese Academy of Sciences state key laboratory of atmospheric Boundary Layer Physics and atmospheric Chemistry (LAPC) Institute of Atmospheric Physics Chinese Academy of Sciences

The radon transport test, which is a widely used test case for atmospheric transport models, is carried out to evaluate the tracer advection schemes in the Grid-Point atmospheric Model of IAP-lasg （GAMIL）. Two of the three available schemes in the model are found to be associated with significant biases in the polar regions and in the upper part of the atmosphere, which implies potentially large errors in the simulation of ozone-like tracers. Theoretical analyses show that inconsistency exists between the advection schemes and the discrete continuity equation in the dynamical core of GAMIL and consequently leads to spurious sources and sinks in the tracer transport equation. The impact of this type of inconsistency is demonstrated by idealized tests and identified as the cause of the aforementioned biases. Other potential effects of this inconsistency are also discussed. Results of this study provide some hints for choosing suitable advection schemes in the GAMIL model. At least for the polax-region-concentrated atmospheric components and the closely correlated chemical species, the Flux-Form Semi-Lagrangian advection scheme produces more reasonable simulations of the large-scale transport processes without significantly increasing the computational expense.

关键词： numerical climate modelling tracer transport advection scheme consistency

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Impacts of Land Surface on Climate of July and On set of Summer Monsoon:A Study with an AGCM plus SSiB

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Advances in atmospheric sciences 1997年第3期14卷 2-8,10+12+14-16+18-2页

作者： Liu Hui Wu Guoxiong state key laboratory of Numerical modelling for atmospheric sciences and geophysical fluid dynamics (lasg) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing

ＩｍｐａｃｔｓｏｆＬａｎｄＳｕｒｆａｃｅｏｎＣｌｉｍａｔｅｏｆＪｕｌｙａｎｄＯｎｓｅｔｏｆＳｕｍｍｅｒＭｏｎｓｏｏｎ：ＡＳｔｕｄｙｗｉｔｈａｎＡＧＣＭｐｌｕｓＳＳｉＢ①ＬｉｕＨｕｉ（刘辉）ａｎｄＷｕＧｕｏｘｉｏｎｇ（... 详细信息

ＩｍｐａｃｔｓｏｆＬａｎｄＳｕｒｆａｃｅｏｎＣｌｉｍａｔｅｏｆＪｕｌｙａｎｄＯｎｓｅｔｏｆＳｕｍｍｅｒＭｏｎｓｏｏｎ：ＡＳｔｕｄｙｗｉｔｈａｎＡＧＣＭｐｌｕｓＳＳｉＢ①ＬｉｕＨｕｉ（刘辉）ａｎｄＷｕＧｕｏｘｉｏｎｇ（吴国雄）ＳｔａｔｅＫｅｙＬａｂｏｒ...

关键词： AGCM plus SSiB Impacts of land surface processes

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GRACE terrestrial water storage data assimilation based on the ensemble four-dimensional variational method PODEn4DVar:Method and validation

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Science China Earth sciences 2015年第12期58卷 371-384页

作者： SUN Qin XIE ZhengHui TIAN XiangJun state key laboratory of Numerical modelling for atmospheric sciences and geophysical fluid dynamics(lasg) Institute of Atmospheric PhysicsChinese Academy of Sciences University of Chinese Academy of sciences Numerical Weather Prediction Center China Meteorological Administration

Seasonal and interannual changes in the Earth's gravity field are mainly due to mass exchange among the atmosphere,ocean,and continental water *** terrestrial water storage changes,detected as gravity changes by the Gravity Recovery and Climate Experiment(GRACE) satellites,are mainly caused by precipitation,evapotranspiration,river transportation and downward infiltration *** this study,a land data assimilation system LDAS-G was developed to assimilate the GRACE terrestrial water storage(TWS) data into the Community Land Model(CLM3.5) using the POD-based ensemble four-dimensional variational assimilation method PODEn4 DVar,disaggregating the GRACE large-scale terrestrial water storage changes vertically and in time,and placing constraints on the simulation of vertical hydrological variables to improve land surface hydrological *** ideal experiments conducted at a single point and assimilation experiments carried out over China by the LDAS-G data assimilation system showed that the system developed in this study improved the simulation of land surface hydrological variables,indicating the potential of GRACE data assimilation in large-scale land surface hydrological research and applications.

关键词： data assimilation land surface model terrestrial water storage ensemble four-dimensional variational data assimilation method

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Arctic Oscillation and Antarctic Oscillation in Internal atmospheric Variability with an Ensemble AGCM Simulation

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Advances in atmospheric sciences 2007年第1期24卷 152-162页

作者：陆日宇李颖 Buwen DONG state key laboratory of Numerical Modeling for atmospheric sciences and geophysical fluid dynamics （lasg） and Center for Monsoon System Research （ CMSR） Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 Graduate University of the Chinese Academy of sciences Beijing 100039 National Centre for atmospheric Science-Climate （ NCAS） Centre for Global atmospheric modelling Department of Meteorology University of Reading Reading United Kingdom

In this study, we investigated the features of Arctic Oscillation （AO） and Antarctic Oscillation （AAO）, that is, the annular modes in the extratropics, in the internal atmospheric variability attained through an ensemble of integrations by an atmospheric general circulation model （AGCM） forced with the global observed SSTs. We focused on the interannual variability of AO/AAO, which is dominated by internal atmospheric variability. In comparison with previous observed results, the AO/AAO in internal atmospheric variability bear some similar characteristics, but exhibit a much clearer spatial structure： significant correlation between the North Pacific and North Atlantic centers of action, much stronger and more significant associated precipitation anomalies, and the meridional displacement of upper-tropospheric westerly jet streams in the Northern/Southern Hemisphere. In addition, we examined the relationship between the North Atlantic Oscillation （NAO）/AO and East Asian winter monsoon （EAWM）. It has been shown that in the internal atmospheric variability, the EAWM variation is significantly related to the NAO through upper-tropospheric atmospheric teleconnection patterns.

关键词： internal atmospheric variability North Atlantic Oscillation Arctic Oscillation Antarctic Oscillation extratropical climate anomalies East Asian winter monsoon

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Observational analysis and numerical simulation of the interannual variability of the boreal winter Hadley circulation over the recent 30 years

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Science China Earth sciences 2013年第2期56卷 647-661页

作者： SUN Yong ZHOU TianJun ZHANG LiXia state key laboratory of Numerical modelling for atmospheric sciences and geophysical fluid dynamics (lasg) Institute of Atmospheric Physics Chinese Academy of Sciences Graduate University of Chinese Academy of sciences Climate Change Research Center Chinese Academy of Sciences

The interannual variability of the boreal winter （DJF） Hadley Cell strength during 1979-2008 is investigated using NCEP/NCAR reanalysis data. The results of AMIP simulation of lasg/IAP AGCM GAMIL2.0 are compared against the re- analysis data. Both the reanalysis data and the simulation show that the interannual variability of the Hadley Cell strength has a non-uniform spatial distribution, as evidenced by the 1st Empirical Orthogonal Function （EOF） mode. The change of Hadley cell strength in the tropics is opposite to that in the subtropical regions. Our analysis indicates that a positive phase of EOF1 is associated with an E1 Nifio-like warmer equatorial central and eastern Pacific and a warmer southern Indian Ocean. Above features are also seen in the results of GAMIL2.0 simulation, indicating that the interannual variability of the Hadley Cell strength is driven by the tropical ocean variability. Our analysis also demonstrates that the contribution of the warmer cen- tral-eastern Pacific to the 1st EOF mode is larger than that of the South Indian Ocean. The SST forcing enhances the local Hadley circulation strength in the central Pacific and Africa （30°S-30°N, 150°E-90°W）, while it weakens the local Hadley circulation in other regions （30°S-30°N, 90°-10°W）. The western Pacific anticyclone remotely driven by the E1 Nifio forcing leads to a weakened local Hadley cell in the Northern Hemisphere, while the South Indian Ocean anticyclone driven by the remote E1 Nifio forcing and the local warmer SST anomalies in the southern Indian Ocean results in a weakened local Hadley Cell in the Southern Hemisphere. The enhancement of the Pacific local Hadley Cell is stronger （weaker） than that of the Atlan- tic, the western Pacific, and the southern Indian Ocean in the tropical （subtropical） part, thus for the zonal mean condition the strength of the total Hadley Cell is stronger （weaker） in the tropical （subtropical） limb. The amplitude of the Hadley Cell change in the Northern

关键词： Hadley circulation interannual variability GAMIL2.0

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Low-Level Jets over Southeast China: The Warm Season Climatology of the Summer of 2003

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atmospheric and Oceanic Science Letters 2012年第5期5卷 394-400页

作者： LIU Hong-Bo LI Li-Juan WANG Bin state key laboratory of Numerical modelling for atmospheric sciences and geophysical fluid dynamics (lasg) Institute of At- mospheric Physics Chinese Academy of Sciences Beijing 100029 China Center for Earth System Science Tsinghua University Beijing 100084 China

The southwesterly low-level jet （LLJ） over southeast China in the summer of 2003 is analyzed in this study. The analysis is based on the National Centers for Environmental Prediction （NCEP） Final （FNL） operational global analysis data on 1.0-1.0-degree grids at 6-h intervals. The major criteria for choosing the LLJ ineluded the following： a maximum wind speed equal to or greater than 12.0 m s-1, a wind direction of between 180° and 270°, and the height of wind maximum at 900-700 hPa, not confined to single pressure level. The results show that the LLJs over southeast China dominate at 850 and 800 hPa. These LLJs are closely associated with the topography of this area and tend to locate regions with large terrain gradients, including the northeastern and eastem Yunnan-Guizhou Plateau. Under the influence of mid-latitude westerly winds, the LLJs above 750 hPa move northward to the Yangtze-Huai River Basin. Com- pared to the ten-year （2000-2009） mean climate condi- tions, the LLJs in the warm season of summer 2003 were exceptionally active and strong, as reflected by the posi- tive anomalies of LLJ occurrence numbers and wind speed. In addition, the 2003 LLJs showed strong diurnal variation, especially at pressure levels below 800 hPa. The majority of the LLJs appeared between midnight and the early moming hours （before 8 a.m.）. Finally, the summary of LLJ grid numbers indicates that more than 80% of LLJs in June and July 2003 occurred within the 33-d rainy period. Thus, these LLJs are directly related to the anomalously heavy rainfall in the Yangtze-Huai River Basin.

关键词： low-level jet anomaly diurnal variation heavy rainfall

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