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Acta meteorologica Sinica 2002年第1期16卷 165-179页

作者：刘一鸣丁一汇 National Climate Center Beijing 100081

By comparison of simulated cumulus convection processes in RegCM2,using the Kuo scheme, the Grell scheme and the mass flux scheme (MFS),it is found that the MFS can simulate the cumulus heating and moistening very well.A series of sensitivity tests show that the parameters for specifying the conversion coefficient from cloud droplets to raindrops,the turbulent entrainment and detrainment rates in updrafts anddowndrafts,and the intensity of thedowndrafts have different degrees of influence upon the cumulus convection.Therefore.it is quite important for cumulus parameterization scheme to define these parameters as accurately as possible.

关键词： mass flux scheme(MFS) cumulus convection sensitivity experiment

Effect of compressive strength on the performance of the NEMO-LIM model in Arctic Sea ice simulation

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Journal of Oceanology and Limnology 2023年第1期41卷 1-16页

作者： Chunming DONG Xiaofan LUO Hongtao NIE Wei ZHAO Hao WEI School of Marine Science and Technology Tianjin UniversityTianjin 300072China

Satellite records show that the extent and thickness of sea ice in the Arctic Ocean have significantly decreased since the early 1970s.The prediction of sea ice is highly important,but accurate simulation of sea ice variations remains highly challenging.For improving model performance,sensitivity experiments were conducted using the coupled ocean and sea ice model(NEMO-LIM),and the simulation results were compared against satellite observations.Moreover,the contribution ratios of dynamic and thermodynamic processes to sea ice variations were analyzed.The results show that the performance of the model in reconstructing the spatial distribution of Arctic sea ice is highly sensitive to ice strength decay constant(C^(rhg)).By reducing the C^(rhg) constant,the sea ice compressive strength increases,leading to improved simulated sea ice states.The contribution of thermodynamic processes to sea ice melting was reduced due to less deformation and fracture of sea ice with increased compressive strength.Meanwhile,dynamic processes constrained more sea ice to the central Arctic Ocean and contributed to the increases in ice concentration,reducing the simulation bias in the central Arctic Ocean in summer.The root mean square error(RMSE)between modeled and the CryoSat-2/SMOS satellite observed ice thickness was reduced in the compressive strength-enhanced model solution.The ice thickness,especially of multiyear thick ice,was also reduced and matched with the satellite observation better in the freezing season.These provide an essential foundation on exploring the response of the marine ecosystem and biogeochemical cycling to sea ice changes.

关键词： sea ice compressive strength sensitivity experiment ocean-sea ice model Arctic Ocean

Using the Newtonian relaxation technique in numerical sensitivity studies

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Science China Earth Sciences 2016年第12期59卷 2454-2462页

作者： SHAO AiMei QIU ChongJian WANG XueJiao ZHANG YuXuan Key Laboratory of Arid Climatic Changes and Disaster Reduction of Gansu Province Key Laboratory for Semi-Arid Climate Change of the Ministry of EducationCollege of Atmospheric SciencesLanzhou University

In model-based sensitivity studies,the growth of model error over long-term integrations may lead to serious deviations between the simulated and actual states.To reduce these errors,we have developed a new modeling approach with application of the Newtonian relaxation technique,or nudging.In this approach,an identical artificial Newtonian relaxation term that reflects the difference between the model reference state and its analysis(available in many sensitivity studies) is added to the prognostic equations of the two simulated states,the reference state and the perturbed state(for which observations are nonexistent).We have conducted idealized sensitivity experiments with a shallow-water model to evaluate the benefits and viability of this approach and to test its sensitivity to changes in the nudging period and error in the analysis data.The experimental results confirm that this approach lead to more credible atmospheric responses to modified external forcing if the data error is within a reasonable range.The results also indicate that a 12-hour period is more favorable for nudging than a 24-hour period.

关键词： Numerical simulation sensitivity experiment Newtonian relaxation Shallow-water model

Multi-year Simulations and experimental Seasonal Predictions for Rainy Seasons in China by Using a Nested Regional Climate Model (RegCM_NCC). Part Ⅰ: sensitivity Study

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Advances in Atmospheric Sciences 2006年第4期23卷 323-341页

作者：丁一汇史学丽刘一鸣刘艳李清泉钱永甫苗蔓倩翟国庆高昆 Laboratory for Climate Studies Chinese Academy of Meteorological Science Department of Atmospheric Sciences Department of Geoscience

A modified version of the NCAR/RegCM2 has been developed at the National Climate Center （NCC）, China Meteorological Administration, through a series of sensitivity experiments and multi-year simulations and hindcasts, with a special emphasis on the adequate choice of physical parameterization schemes suitable for the East Asian monsoon climate. This regional climate model is nested with the NCC/IAP （Institute of Atmospheric Physics） T63 coupled GCM to make an experimental seasonal prediction for China and East Asia. The four-year （2001 to 2004） prediction results are encouraging. This paper is the first part of a two-part paper, and it mainly describes the sensitivity study of the physical process paraxneterization represented in the model. The systematic errors produced by the different physical parameterization schemes such as the land surface processes, convective precipitation, cloud-radiation transfer process, boundary layer process and large-scale terrain features have been identified based on multi-year and extreme flooding event simulations. A number of comparative experiments has shown that the mass flux scheme （MFS） and Betts-Miller scheme （BM） for convective precipitation, the LPMI （land surface process model I） and LPMII （land surface process model Ⅱ） for the land surface process, the CCM3 radiation transfer scheme for cloud-radiation transfer processes, the TKE （turbulent kinetic energy） scheme for the boundary layer processes and the topography treatment schemes for the Tibetan Plateau are suitable for simulations and prediction of the East Asia monsoon climate in rainy seasons. Based on the above sensitivity study, a modified version of the RegCM2 （RegCM_NCC） has been set up for climate simulations and seasonal predictions.

关键词： regional climate model sensitivity experiment physical process parameterization mei-yu

sensitivity and nonlinearity of Eurasian winter temperature response to recent Arctic sea ice loss

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Acta Oceanologica Sinica 2017年第8期36卷 52-58页

作者： SUI Cuijuan ZHANG Zhanhai YU Lejiang LI Yi SONG Mirong College of Physical and Environmental Oceanography Ocean University of ChinaQingdao 266100China National Marine Environmental Forecasting Center Beijing 100081China Polar Research Institute of China Shanghai 200129China Institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029China

The recent decline in the Arctic sea ice has coincided with more cold winters in Eurasia. It has been hypothesized that the Arctic sea ice loss is causing more mid-latitude cold extremes and cold winters, yet there is lack of consensus in modeling studies on the impact of Arctic sea ice loss. Here we conducted modeling experiments with Community Atmosphere Model Version 5 （CAM5） to investigate the sensitivity and linearity of Eurasian winter temperature response to the Atlantic sector and Pacific sector of the Arctic sea ice loss. Our experiments indicate that the Arctic sea ice reduction can significantly affect the atmospheric circulation by strengthening the Siberian High, exciting the stationary Rossby wave train, and weakening the polar jet stream, which in turn induce the cooling in Eurasia. The temperature decreases by more than I^C in response to the ice loss in the Atlantic sector and the cooling is less and more shifts southward in response to the ice loss in the Pacific sector. More interestingly, sea ice loss in the Atlantic and Pacific sectors together barely induces cold temperatures in Eurasia, suggesting the nonlinearity of the atmospheric response to the Arctic sea ice loss.

关键词： cold winter CAM5 sensitivity experiment jet stream

Adjoint sensitivity experiments of a Meso-β-scale Vortex in the Middle Reaches of the Yangtze River

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Advances in Atmospheric Sciences 2006年第2期23卷 267-281页

作者：王智高坤 Shanghai Meteorology Center Shanghai 200030 Department of Earth Sciences Zhejiang University Hangzhou 310027

A relatively independent and small-scale heavy rainfall event occurred to the south of a slow eastwardmoving meso-α-scale vortex. The analysis shows that a meso-β-scale system is heavily responsible for the intense precipitation. An attempt to simulate it met with some failures. In view of its small scale, short lifetime and relatively sparse observations at the initial time, an adjoint model was used to examine the sensitivity of the meso-β-scale vortex simulation with respect to initial conditions. The adjoint sensitivity indicates how small perturbations of initial model variables anywhere in the model domain can influence the central vorticity of the vortex. The largest sensitivity for both the wind and temperature perturbation is located below 700 hPa, especially at the low level. The largest sensitivity for the water vapor perturbation is located below 500 hPa, especially at the middle and low levels. The horizontal adjoint sensitivity for all variables is mainly located toward the upper reaches of the Yangtze River with respect to the simulated meso-β-scale system in Hunan and Jiangxi provinces with strong locality. The sensitivity shows that warm cyclonic perturbations in the upper reaches can have a great effect on the development of the meso-β-scale vortex. Based on adjoint sensitivity, forward sensitivity experiments were conducted to identify factors influencing the development of the meso-β-scale vortex and to explore ways of improving the prediction. A realistic prediction was achieved by using adjoint sensitivity to modify the initial conditions and implanting a warm cyclone at the initial time in the upper reaches of the river with respect to the meso-β-scale vortex, as is commonly done in tropical cyclone prediction.

关键词： mei-yu front heavy rainfall meso-β-scale vortex adjoint method sensitivity experiment

Simulating global soil-CO_2 flux and its response to climate change

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Journal of Environmental Sciences 2000年第3期12卷 257-265页

作者： PENG Chang-hui Michael JApps Ontario Forest Research Institute Ministry of Natural Resources1235 Queen Street EastSault Ste.MarieON P6A 2E5Canada. Morthern Forestry Center Canadian Forest Service5320-122 StreetEdmontonAlberta T6H3S5 Canada

It has been argued that increased soil respiration would become a major atmospheric source of CO\-2 in the event of global warming. The simple statistical models were developed based on a georeferenced database with 0 5°×0 5° longitude/latitude resolution to simulate global soil\|CO\-2 fluxes, to investigate climatic effects on these fluxes using sensitivity experiments, and to assess possible responses of soil\|CO\-2 fluxes to various climate change scenarios. The statistical models yield a value of 69 PgC/a of global soil\|CO\-2 fluxes for current condition. sensitivity experiments confirm that the fluxes are responsive to changes in temperature, precipitation and actual evapotranspiration, but increases in temperature and actual evapotranspiration affect soil\|CO 2 fluxes more than increases in precipitation. Using climatic change projections from four global circulation models, each corresponding to an equilibrium doubling of CO 2, it can be found that the largest increases in soil\|CO 2 fluxes were associated with the boreal and tundra regions. The globally averaged soil\|CO 2 fluxes were estimated to increase by about 35% above current values, providing a positive feedback to the greenhouse effect.

关键词： climatic variable sensitivity experiment soil respiration statistical model

Primary Reasoning behind the Double ITCZ Phenomenon in a Coupled Ocean-Atmosphere General Circulation Model

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Advances in Atmospheric Sciences 2004年第6期21卷 857-867页

作者：李江龙张学洪俞永强戴福山 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 National Climate Center Beijing 100081 Beijing Institute of Applied Meteorology Beijing 100029

This paper investigates the processes behind the double ITCZ phenomenon, a common problem in Coupled ocean-atmosphere General Circulation Models (CGCMs), using a CGCM—FGCM-0 (Flexible General Circulation Model, version 0). The double ITCZ mode develops rapidly during the ?rst two years of the integration and becomes a perennial phenomenon afterwards in the model. By way of Singular Value Decomposition (SVD) for SST, sea surface pressure, and sea surface wind, some air-sea interactions are analyzed. These interactions prompt the anomalous signals that appear at the beginning of the coupling to develop rapidly. There are two possible reasons, proved by sensitivity experiments: (1) the overestimated east-west gradient of SST in the equatorial Paci?c in the ocean spin-up process, and (2) the underestimated amount of low-level stratus over the Peruvian coast in CCM3 (the Community Climate Model, Version Three). The overestimated east-west gradient of SST brings the anomalous equatorial easterly. The anomalous easterly, a?ected by the Coriolis force in the Southern Hemisphere, turns into an anomalous westerly in a broad area south of the equator and is enhanced by atmospheric anomalous circulation due to the underestimated amount of low-level stratus over the Peruvian coast simulated by CCM3. The anomalous westerly leads to anomalous warm advection that makes the SST warm in the southeast Paci?c. The double ITCZ phenomenon in the CGCM is a result of a series of nonlocal and nonlinear adjustment processes in the coupled system, which can be traced to the uncoupled models, oceanic component, and atmospheric component. The zonal gradient of the equatorial SST is too large in the ocean component and the amount of low-level stratus over the Peruvian coast is too low in the atmosphere component.

关键词： coupled ocean-atmosphere general circulation model double intertropical convergence zone heat budget sensitivity experiment

A piecewise-integration method for simulating the influence of external forcing on climate

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Progress in Natural Science:Materials International 2008年第10期18卷 1239-1247页

作者： Zhifu Zhang Chongjian Qiu Chenghai Wang Key Laboratory of Arid Climatic Changing and Reducing Disaster of Gansu Province,College of Atmospheric Sciences,Lanzhou University.Lanzhou 730000.China Key Laboratory of Arid Climatic Changing and Reducing Disaster of Gansu Province College of Atmospheric Sciences Lanzhou University Lanzhou 730000 China

Climate drift occurs in most general circulation models (GCMs) as a result of incomplete physical and numerical representation of the complex climate system,which may cause large uncertainty in sensitivity experiments evaluating climate response to changes in external forcing.To solve this problem,we propose a piecewise-integration method to reduce the systematic error in climate sensitivity studies. The observations are firstly assimilated into a numerical model by using the dynamic relaxation technique to relax to the current state of atmosphere,and then the assimilated fields are continuously used to reinitialize the simulation to reduce the error of climate simulation. When the numerical model is integrated with changed external forcing,the results can be split into two parts,background and pertur- bation fields,and the background is the state before the external forcing is changed.The piecewise-integration method is used to con- tinuously reinitialize the model with the assimilated field,instead of the background.Therefore,the simulation error of the model with the external forcing can be reduced.In this way,the accuracy of climate sensitivity experiments is greatly improved.Tests with a simple low-order spectral model show that this approach can significantly reduce the uncertainty of climate sensitivity experiments.

关键词： Climate model External forcing sensitivity experiment Low-order spectral model Dynamic relaxation technique

AN IMPROVED LAND-SURFACE PROCESS MODEL AND ITS SIMULATION experiment——PART I:LAND-SURFACE PROCESS MODEL AND ITS“OFF-LINE”TESTS AND PERFORMANCE ANALYSES

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Acta meteorologica Sinica 1999年第3期13卷 257-277页

作者：张晶丁一汇 National Climate Center Beijing 100081

Based on the existing land-surface schemes and models,an improved Land-surface Process Model(LPM-ZD)has been developed.It has the following major characteristics:(1)The combination of physical equations and empirical analytical formulae are used to construct the governing equations of soil temperature and moisture.Higher resolution of model level and physical equations are adopted for the upper soil layers,and for the lower soil layers,lower resolution of model level is adopted and empirical analytical formulae are used.(2)In land surface hydrological process,the sub-grid distribution of rainfall and its effects are taken into account. (3)A simple snow cover submodel has been used,which includes effects of snow cover on soil thermodynamics and hydrology,as well as albedo. By use of this model and three groups of point observation data,a series of“off-line”tests have been carried out.The simulation results indicate that land-surface process model has good performance and can well simulate diurnal and seasonal variation of land surface processes for many kinds of land surface covers(forest,grass,crops and desert)in different climate zone.The results simulated by the model are consistent with the observations.Later,by use of one group of observation data and the model,a series of sensitivity experiments have been done.It is shown that the model is much sensitive to some parameters,such as initial soil moisture,vegetation physical parameters as well as the proportion of the grid covered with rain.Therefore it is much important for land-surface process model to define these parameters as accurately as possible.

关键词： land-surface process model “off-line”test sensitivity experiment