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Evolution of desertification in a two-dimensional energy balance model coupled with thermodynamics and dynamics

Science china Earth sciences 2010年第11期53卷 1726-1733页

作者： CHAO JiPing1,2 & LI YaoKun3,4 1National Marine Environmental Forecasting Center, beijing 100081, china 2First institute of Oceanography, state Oceanic Administration, Qingdao 266061, china 3state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics, institute of atmospheric physics, chinese academy of sciences, beijing 100029, china 4Graduate University of chinese academy of sciences, beijing 100049, china National Marine Environmental Forecasting Center Beijing China First institute of Oceanography State Oceanic Administration Qingdao China state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China

The relationship between desert evolution and change in albedo has been investigated quasi-analytically using a zonal mean two-dimensional energy balance model which considers the radiation transmission process due to thermodynamics and bound- ary layer movement caused by kinetics. A climate state including temperature, zonal wind, meridional wind and vertical wind can be simulated according to the current zonal distribution of albedo. Given desert distribution, characterized by the value and distribution of albedo, the response of climate on albedo has been studied to analyze the evolution of desert climate. One significant result is that the simple model can reproduce mean meridional circulation. Another result indicates that climate corresponds to two equilibria. This happens when the junction temperature between vegetation and desert is higher than a certain critical value. As for the first equilibrium, the desert belt is predicted to move southward in the northern hemisphere with the increasing values of albedo, which corresponds to the current trend of climate change. For the second equilibrium, vegetation will expand northward with increasing values of albedo, which would indicate a narrowing of the desert belt. In order to determine if the two equilibria exist, new physical models are needed.

关键词： two-dimensional energy balance model desertification two equilibria

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Sensitivity of sea ice and ocean simulations to sea ice salinity in a coupled global climate model

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Science china Earth sciences 2010年第6期53卷 911-918页

作者： LIU JiPing state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics, institute of atmospheric physics, chinese academy of sciences, beijing, 100029, china state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China

The impacts of the spatiotemporal variations of sea ice salinity on sea ice and ocean characteristics have not been studied in detail, as the existing climate models neglect or misrepresent this process. To address this issue, this paper formulated a parameterization with more realistic sea ice salinity budget, and examined the sensitivity of sea ice and ocean simulations to the ice salinity variations and associated salt flux into the ocean using a coupled global climate model. Results show that the inclusion of such a parameterization leads to an increase and thickening of sea ice in the Eurasian Arctic and within the ice pack in the Antarctic circumpolar region, and a weakening of the North Atlantic Deep Water and a strengthening of the Antarctic Bottom Water. The atmospheric responses associated with the ice changes were also discussed.

关键词： sea ice salinity coupled global climate model Arctic and Antarctic

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Computational properties of a new horizontal staggered grid

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Science china Earth sciences 2005年第9期48卷 1559-1568页

作者： LIU Yudistate key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics, institute of atmospheric physics, chinese academy of sciences, beijing 100029, china institute of Meteorology, PLA University of Science and Technology, Nanjing 211101, china state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric Ph Chinese Academy of Sciences Beijing China institute of Meteorology PLA University of Science and Technology Nanjing China

This paper presents a new horizontal staggered grid (LE grid), which defines h at a gridpoint, and both u and v at the same mid-gridpoint along the x and y directions. A general method is used to deduce the dispersion relationships of describing inertia gravity waves on LE grid and Arakawa A―E grids, which are then compared with the analytical solution (AS) in re- solved or under-resolved cases, using two-order central difference or four-order compact differ- ence scheme from the frequency and group velocity. Results show that in both resolved and under-resolved cases, no matter whether two-order central difference or four-order compact dif- ference scheme is used, the frequency and group velocity discrete errors on LE grid in describing inertia gravity waves are smaller than those of Arakawa A―E grids. At the same time, it is only on LE or Arakawa grid C that the employment of a compact difference scheme of higher difference precision can improve their accuracy in describing inertia gravity waves. However, as for the other four grids (Arakawa A,B,D and E), when the difference precision increases, the accuracy of simulating inertia gravity waves decreases.

关键词： horizontal staggered grid, inertia gravity wave, LE grid, Arakawa A-E grid, compact difference scheme, central difference.

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Optimality of a nonlinear stability criterion of two-layer Phillips model

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chinese Science Bulletin 1998年第8期43卷 656-659页

作者： MU Mu state key laboratory of numerical Modelling for atmospheric sciences and geophysical fluid dynamics, institute of atmospheric physics, chinese academy of sciences, beijing 100029, china state key laboratory of numerical Modelling for atmospheric sciences and geophysical fluid dynamics. institute of atmospheric physics Chinese Academy of Sciences Beijing China

The optimality of a nonlinear stability criterion of motions of two_layer Phillips model is investigated. The result shows that for a given zonal periodical channel, there exist cases that there is no normal mode which grows exponentially even if the sufficient conditions of the criterion are destroyed. On the other hand, the above criterion is optimal in the following sense: when the sufficient conditions of the criterion are destroyed, except some critical cases, there exists a finite zonal periodical channel, in which there is a zonal normal mode growing exponentially.

关键词： Phillips model nonlinearity stability.

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numerical SIMULATIONS OF SEA ICE WITH DIFFERENT ADVECTION SCHEMES

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Journal of Hydrodynamics 2011年第3期23卷 372-378页

作者： LIU Xi-ying state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China institute of Meteorology PLA University of Science and Technology Nanjing 211101 China

numerical simulations are carried out for sea ice with four different advection schemes to study their effects on the simulation results. The sea ice model employed here is the Sea Ice Simulator （SIS） of the geophysical fluid dynamics laboratory （GFDL） Modular Ocean Model version 4b （MOM4b） and the four advection schemes are, the upwind scheme originally used in the SIS, the Multi-Dimensional Positive Advection （MDPA） scheme, the Incremental Remapping Scheme （IRS） and the Two Step Shape Preserving （TSSP） scheme. The latter three schemes are newly introduced. To consider the interactions between sea ice and ocean, a mixed layer ocean model is introduced and coupled to the SIS. The coupled model uses a tri-polar coordinate with 120x65 grids, covering the whole earth globe, in the horizontal plane. Simulation results in the northern high latitudes are analyzed. In all simulations, the model reproduces the seasonal variation of sea ice in the northern high latitudes well. Compared with the results from the observation, the sea ice model produces some extra sea ice coverage in the Greenland Sea and Barents Sea in winter due to the exclusion of ocean current effects and the smaller simulated sea ice thickness in the Arctic basin. There are similar features among the results obtained with the introduced three advection schemes. The simulated sea ice thickness with the three newly introduced schemes are all smaller than that of the upwind scheme and the simulated sea ice velocities of movement are all smaller than that of the upwind scheme. There are more similarities shared in the results obtained with the MPDA and TSSP schemes.

关键词： advection scheme sea ice simulation

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Improved ENSO simulation in regional coupled GCM using regressive correction method

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Science china Earth sciences 2007年第8期50卷 1258-1265页

作者： FU WeiWei1 & ZHOU GuangQing2 1 Nansen-Zhu International Research Center (NZC), institute of atmospheric physics, chinese academy of sciences (CAS), beijing 100029, china 2 state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics (LASG), institute of At-mospheric physics, CAS, beijing 100029, china Nansen-Zhu International Research Center (NZC) Institute of Atmospheric Physics Chinese Academy of Sciences (CAS) Beijing China state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics (LASG) Institute of Atmospheric Physics CAS Beijing China

A regressive correction method is presented with the primary goal of improving ENSO simulation in regional coupled GCM. It focuses on the correction of ocean-atmosphere exchanged fluxes. On the basis of numerical experiments and analysis, the method can be described as follows: first, driving the ocean model with heat and momentum flux computed from a long-term observation data set; the pro-duced SST is then applied to force the AGCM as its boundary condition; after that the AGCM’s simula-tion and the corresponding observation can be correlated by a linear regressive formula. Thus the re-gressive correction coefficients for the simulation with spatial and temporal variation could be obtained by linear fitting. Finally the coefficients are applied to redressing the variables used for the calculation of the exchanged air-sea flux in the coupled model when it starts integration. This method together with the anomaly coupling method is tested in a regional coupled model, which is composed of a global grid-point atmospheric general circulation model and a high-resolution tropical Pacific Ocean model. The comparison of the results shows that it is superior to the anomaly coupling both in reducing the coupled model ‘climate drift’ and in improving the ENSO simulation in the tropical Pacific Ocean.

关键词： anomaly coupling regressive correction method regional coupled model ENSO simulation

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Influence of atmospheric heat sources over the Tibetan Plateau and the tropical western North Pacific on the inter-decadal variations of the stratosphere-troposphere exchange of water vapor

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Science china Earth sciences 2008年第8期51卷 1179-1193页

作者： ZHAN RuiFen1,2&LI JianPing2 1Shanghai Typhoon institute of china Meteorological Administration,Shanghai 200030,china 2state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics(LASG),institute of atmospheric physics,chinese academy of sciences,beijing 100029,china Shanghai Typhoon institute of china Meteorological Administration Shanghai China state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics (LASG) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China

This study investigates the Stratosphere-Troposphere Exchange(STE) of water vapor,emphasizes its interdecadal variations over Asia in boreal summer,and discusses the influences of atmospheric heat sources over the Tibetan Plateau and the tropical western North Pacific(WNP) on them by using the Wei method with reanalysis data from the European Centre for Medium-Range Weather Forecasts(ECMWF) for the years of *** climatology shows that the upward transport of water vapor across the tropopause in boreal summer is the most robust over the joining area of the South Asian Peninsula and Indian-Pacific Oceans(defined as AIPO).The upward transport over there can persistently convey the abundant water vapor into the stratosphere and then influence the distribution and variation of the stratospheric water *** analysis shows that interdecadal variations of the water vapor exchange over the AIPO are significant,and its abrupt change occurred in the mid-1970s and the early *** these three periods,as important channels of the water vapor exchange,the effect of Bay of Bengal-East Asia as well as South china Sea was gradually weakening,while the role of the WNP becomes more and more *** studies show that atmospheric heat sources over the Tibetan Plateau and the WNP are two main factors in determining the interdecadal variations of water vapor *** thermal influences over the Tibetan Plateau and the WNP have been greatly adjusted over the pass 44 *** synthesis influences the interdecadal variations of the water vapor exchange by changing the Asian summer monsoon,but their roles vary with time and *** after 1992,the influence of heat source over the Tibetan Plateau remarkably weakens,while the heat source over the WNP dominates the across-tropopause water vapor *** have important implications for understanding the transport of other components in the atmosphere and estimating the impact of human activities(

关键词： Tibetan Plateau tropical western North Pacific atmospheric heat source STE inter-decadal variations

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Nonlinear local Lyapunov exponent and atmospheric predictability research

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Science china Earth sciences 2006年第10期49卷 1111-1120页

作者： CHEN Baohua1, LI Jianping1,2 & DING Ruiqiang2 1. College of atmospheric sciences, Lanzhou University, Lanzhou 730000, china 2. state key laboratory of numerical modeling for atmospheric Science and geophysical fluid dynamics (LASG), institute of atmospheric physics, chinese academy of sciences, beijing 100029, china College of atmospheric sciences Lanzhou University Lanzhou China state key laboratory of numerical modeling for atmospheric Science and geophysical fluid dynamics (LASG) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China

Because atmosphere itself is a nonlinear system and there exist some problems using the linearized equations to study the initial error growth, in this paper we try to use the error nonlinear growth theory to discuss its evolution, based on which we first put forward a new concept: nonlinear local Lyapunov exponent. It is quite different from the classic Lyapunov exponent because it may characterize the finite time error local average growth and its value depends on the initial condition, initial error, variables, evolution time, temporal and spatial scales. Based on its definition and the at-mospheric features, we provide a reasonable algorithm to the exponent for the experimental data, obtain the atmospheric initial error growth in finite time and gain the maximal prediction time. Lastly, taking 500 hPa height field as example, we discuss the application of the nonlinear local Lyapunov exponent in the study of atmospheric predictability and get some reliable results: atmospheric predictability has a distinct spatial structure. Overall, predictability shows a zonal distribution. Prediction time achieves the maximum over tropics, the second near the regions of Antarctic, it is also longer next to the Arctic and in subtropics and the mid-latitude the predictability is lowest. Particularly speaking, the average prediction time near the equation is 12 days and the maximum is located in the tropical Indian, Indonesia and the neighborhood, tropical eastern Pacific Ocean, on these regions the prediction time is about two weeks. Antarctic has a higher predictability than the neighboring latitudes and the prediction time is about 9 days. This feature is more obvious on Southern Hemispheric summer. In Arctic, the predictability is also higher than the one over mid-high latitudes but it is not pronounced as in Antarctic. Mid-high latitude of both Hemispheres (30°S―60°S, 30°―60°N) have the lowest predictability and the mean prediction time is just 3―4 d. In addition, predictab

关键词： nonlinear, local, Lyapunov exponent, atmospheric predictability, maximal prediction time.

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EXPERIMENTS OF SEA ICE SIMULATION

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Journal of Hydrodynamics 2005年第6期17卷 686-692页

作者： LIU Xi-ying state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics （LASG） Institute of Atmospheric Physics （IAP） Chinese Academy of Sciences Beijing 100029 China

As a substitute for the original displaced pole grids, a simple rotated spherical coordinate system was intro duced into the Community Sea Ice Model version 4（CSIM4）, which is a component of the Community Climate System Model（CCSM） of the American National Center of atmospheric Researeh（NCAR）, to deal with the ＂pole problems＂. In the new coordinates, both the geographical North Pole and South Pole lie in the model equator and grid sizes near the polar region are more uniform. With reanalysis dataset of American National Centers for Environment Prediction （NCEP） and Levitus dataset without considering sub-mixed layer heat flux, the model was integrated for 100 years with thermodynamics *** involved only in the former 49 years and both dynamic and thermodynamic processes involved in the left time. Inner consistency of model results was checked with no contradiction found. The results of last 10 years＇ model output were analyzed and it is shown that the simulated sea ice seasonal variation is rational whereas sea ice extent in the Barcnts Sea in winter is larger than that of observation, numerical experiment on influence of sub-mixed layer heat flux was also carried out and it is shown that the sub-mixed layer heat flux can modulate seasonal variation of sea ice greatly. As a model component, the sea ice model with rotated spherical coordinates was coupled with other models （the oceanic general cir culation model is the LASG/IAP Climate System Ocean Model （LICOM） with reduced grid, other models are components of NCAR CCSM2） forming a climate system model and its preliminary results were also given briefly.

关键词： sea ice numerical simulation climate system model

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Change in the tilting of the ridgeline surface of the subtropical anticyclone and the predictability of the onset of the Asian summer monsoon

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chinese Science Bulletin 2003年第S2期48卷 18-23页

作者： MAO Jiangyu, DUAN Anmin, LIU Yimin WU Guoxiong state key laboratory of numerical modeling for Almospheric sciences and geophysical fluid dynamics (LASG), institute of atmospheric physics, chinese academy of sciences, beijing 100029, china chinese Acad Sci Inst Atmospher Phys Lab Numer Modeling Atmospher Sci & Geophys Fluid LASGState Key Lab Numer Modeling Atmospher Sci & Beijing 100029 Peoples R China

The NCEP/NCAR reanalysis data are used tostudy the relationships among the change in the tilting of theridgeline surface of the subtropical anticyclone, the estab-lishment of the so-called "seasonal transition axis (STA)" andthe onset of the Asian summer monsoon. It is shown that themonsoon onset is characterized by the overturning of themeridional temperature gradient (MTG) in the vicinity of theridgeline surface. A MTG index is then constructed to inves-tigate the predictability of the Asian summer monsoon onsetconceptually. Data diagnoses show that if the initial MTG isknown and the meridional gradient across the ridgeline sur-face of the local temperature tendency can be estimated, alate or early onset of the summer monsoon can be qualita-tively predicted in advance.

关键词： ridgeline surface meridional temperature gradient summer monsoon onset predictability.

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