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The Mid-Holocene Climate Simulated by a Grid-Point agcm Coupled with a Biome Model

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Advances in Atmospheric Sciences 2002年第2期19卷 205-218页

作者：王会军 LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing

The climate simulation for the mid–Holocene about 6000 years before present (6 ka BP) is carried out with a grid–point atmospheric general circulation model (agcm) coupled with a biome model. This coupled model simulation employs orbital parameters of 6 ka BP but present forcing conditions. Results show that large–scale climate differences between now and then are substantial in summer with dramatically strong African–Asian monsoon flow and precipitation during mid–Holocene. Although the results of this coupled model are qualitatively close to those of the agcm, the coupled model shows a larger changes in both precipitation and temperature in summer over the North African monsoon area with weaker cooling in the Northern autumn.

关键词： Mid–Holocene Monsoon agcm Biome model

IAP agcm 4.1对淮河流域夏季降水的预报技巧评估

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气象科学 2018年第4期38卷 489-497页

作者：陈子煊林朝晖江志红俞越南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际联合实验室南京210044 南京信息工程大学气象灾害预报预警与评估协同创新中心南京210044 中国科学院大气物理研究所国际气候与环境科学中心北京100029 中国科学院大学北京100049

基于中国科学院大气物理研究所新一代大气环流模式IAP agcm 4.1共30 a(1981—2010年)的集合回报试验结果,评估了模式对淮河流域夏季降水的预报技巧。分析结果表明,模式总体上可以较好地再现出淮河流域夏季平均降水南多北少的空间分布特... 详细信息

基于中国科学院大气物理研究所新一代大气环流模式IAP agcm 4.1共30 a(1981—2010年)的集合回报试验结果,评估了模式对淮河流域夏季降水的预报技巧。分析结果表明,模式总体上可以较好地再现出淮河流域夏季平均降水南多北少的空间分布特征,其中模式模拟的6月降水量与观测值的空间相关可达0.93。但降水强度与观测相比具有系统性的偏差,且模式模拟的降水年际变率显著偏弱。基于降水距平相关系数的确定性预报技巧分析表明,模式对流域西南部夏季降水的预测技巧较高,达到0.2以上,且模式对6月降水异常的预测能力相对最好,7月次之。针对淮河不同子流域的预报技巧分析表明,IAP agcm 4. 1对蚌埠、鲁台子、王家坝水文控制站以上集水面积的夏季面雨量异常具有一定的预报技巧,30 a集合回报的时间相关系数分别为0. 11、0. 13、0. 16。基于降水等级的概率预报技巧评估表明,模式对7月淮河流域南部少雨事件具有很好的预报能力,同时对6月流域中部多雨事件的预报技巧也较高。

关键词： IAP agcm 4. 1大气环流模式季节预测淮河流域夏季旱涝面雨量

The Boreal Summer Intraseasonal Oscillation Simulated by Four Chinese agcms Participating in the CMIP5 Project

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Advances in Atmospheric Sciences 2014年第5期31卷 1167-1180页

作者： ZHAO Chongbo ZHOU Tianjun SONG Lianchun REN Hongli Laboratory for Climate Studies National Climate Center China Meteorological Administration State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences National Climate Center China Meteorological Administration

The performances of four Chinese agcms participating in the Coupled Model Intercomparison Project Phase 5 （CMIP5） in the simulation of the boreal summer intraseasonal oscillation （BSISO） are assessed. The authors focus on the major characteristics of BSISO： the intensity, significant period, and propagation. The results show that the four agcms can reproduce boreal summer intraseasonal signals of precipitation; however their limitations are also evident. Compared with the Climate Prediction Center Merged Analysis of Precipitation （CMAP） data, the models underestimate the strength of the intraseasonal oscillation （ISO） over the eastern equatorial Indian Ocean （IO） during the boreal summer （May to October）, but overestimate the intraseasonal variability over the western Pacific （WP）. In the model results, the westward propagation dominates, whereas the eastward propagation dominates in the CMAP data. The northward propagation in these models is tilted southwest-northeast, which is also different from the CMAP result. Thus, there is not a northeast-southwest tilted rain belt revolution off the equator during the BSISO＇s eastward journey in the models. The biases of the BSISO are consistent with the summer mean state, especially the vertical shear. Analysis also shows that there is a positive feedback between the intraseasonal precipitation and the summer mean precipitation. The positive feedback processes may amplify the models＇ biases in the BSISO simulation.

关键词： boreal summer intraseasonal oscillation agcm simulation feedback

Simulation of the western North Pacific subtropical high in El Ni?o decaying summers by CMIP5 agcms

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Atmospheric and Oceanic Science Letters 2017年第2期10卷 146-155页

作者： DONG Xiao FAN Fang-Xing LIN Ren-Ping JIN Jiang-Bo LIAN Ru-Xu International Center for Climate and Environment Sciences Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China

The performances of CMIP5 atmospheric general circulation models （agcms） in simulating the western North Pacific subtropical high （WNPSH） in El Nino decaying summers are examined in this study. Results show that most models can reproduce the spatial pattern of both climatological and anomalous circulation associated with the WNPSH in El Nino decaying summers. Most CMIP5 agcms can capture the westward shift of the WNPSH in El Nino decaying summers compared with the climatological location. With respect to the sub-seasonal variation of the WNPSH, the performances of these agcms in reproducing the northward jump of the WNPSH are better than simulating the eastward retreat of the WNPSH from July to August. Twenty-one out of twenty-two （20 out of 22） models can reasonably reproduce the northward jump of the WNPSH in El Nino decaying summers （climatology）, while only 7 out of 22 （8 out of 22） agcms can reasonably reproduce the eastward retreat of the WNPSH in El Nino decaying summers （climatology）. In addition, there is a close connection between the climatological WNPSH location bias and that in El Nino decaying summers.

关键词： Western North Pacific subtropical high El Nino decaying summer CMIPS agcm sub-seasonal variation

Equilibrium Mechanism Analysis on the Physical Processes of IAP3.0

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Advances in Atmospheric Sciences 2005年第4期22卷 525-533页

作者：左瑞亭王丽琼曾庆存张铭 P.O.Box 2781 Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100080 Meteorology Institute Science and Engineering University of the P.L.A. Nanjing 211101 Meteorology Institute Science and Engineering University of the P.L.A. Nanjing 211101 P.O.Box 2781 Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100080

Based on the detection of the dynamic and thermodynamic functions of the physical processes in IAP3.0, the equilibrium mechanisms of the temperature, moisture and wind axe analyzed. The negative feedback between the longwave radiation and temperature is verified. The cooling regulation of net radiation on temperature is mostly balanced by the heating of precipitation; the leading actions on temperature of other processes such as vertical diffusion, shallow cumulus convection and friction are merely available for lower air. The moisture consumption of precipitation is compensated on the whole by the provision of shallow cumulus convection, which sustains the moisture conservation to a high degree. The wind field is directly regulated by the momentum redistribution of cumulus, the dry adiabatic convection and vertical diffusion. Yet, the prominent influences of these processes are generally confined to the lower level. The east wind at low latitudes and the west wind at high latitudes are both weakened by the regulations and furthermore, by virtue of the transportation of mean meridional circulation, such a variation exactly maintains the angular momentum conservation.

关键词： physical processes equilibrium mechanism numerical simulation agcm

Attribution of Biases of Interhemispheric Temperature Contrast in CMIP6 Models

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Advances in Atmospheric Sciences 2024年第2期41卷 325-340页

作者： Shiyan ZHANG Yongyun HU Jiankai ZHANG Yan XIA Laboratory for Climate and Ocean-Atmosphere Studies Department of Atmospheric and Oceanic SciencesSchool of PhysicsPeking UniversityBeijing 100871China College of Atmospheric Sciences Lanzhou UniversityLanzhou 730000China School of Systems Science Beijing Normal UniversityBeijing 100875China

One of the basic characteristics of Earth's modern climate is that the Northern Hemisphere(NH) is climatologically warmer than the Southern Hemisphere(SH). Here, model performances of this basic state are examined using simulation results from 26 CMIP6 models. Results show that the CMIP6 models underestimate the contrast in interhemispheric surface temperatures on average(0.8 K for CMIP6 mean versus 1.4 K for reanalysis data mean), and that there is a large intermodel spread, ranging from -0.7 K to 2.3 K. A box model energy budget analysis shows that the contrast in interhemispheric shortwave absorption at the top of the atmosphere, the contrast in interhemispheric greenhouse trapping, and the crossequatorial northward ocean heat transport, are all underestimated in the multimodel mean. By examining the intermodel spread, we find intermodel biases can be tracked back to biases in midlatitude shortwave cloud forcing in agcms. Models with a weaker interhemispheric temperature contrast underestimate the shortwave cloud reflection in the SH but overestimate the shortwave cloud reflection in the NH, which are respectively due to underestimation of the cloud fraction over the SH extratropical ocean and overestimation of the cloud liquid water content over the NH extratropical *** that underestimate the interhemispheric temperature contrast exhibit larger double ITCZ biases, characterized by excessive precipitation in the SH tropics. Although this intermodel spread does not account for the multimodel ensemble mean biases, it highlights that improving cloud simulation in agcms is essential for simulating the climate realistically in coupled models.

关键词： interhemispheric temperature contrast energy balance shortwave cloud forcing ITCZ CMIP6 agcm

The Influence of Regional SSTs on the Interdecadal Shift of the East Asian Summer Monsoon

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Advances in Atmospheric Sciences 2013年第2期30卷 330-340页

作者： FU Jianjian LI Shuanglin Climate Changes Research Center and Nansen-Zhu International Research Centre Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 Key Laboratory of Regional Climate-Environment for East Asia Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029

East Asia has experienced a significant interdecadal climate shift since the late 1970s. This shift was accompanied by a decadal change of global SST. Previous studies have suggested that the decadal shift of global SST background status played a substantial role in such a climatic shift. However, the individual roles of different regional SSTs remain unclear. In this study, we investigated these roles using ensemble experiments of an atmospheric general circulation model, GFDL （Geophysical Fluid Dynamics Laboratory） AM2. Two kinds of ensembles were performed. The first was a control ensemble in which the model was driven with the observed climatological SSTs. The second was an experimental ensemble in which the model was driven with the observed climatological SSTs plus interdecadal SST background shifts in separate ocean regions. The results suggest that the SST shift in the tropics exerted more important influence than those in the extratropics, although the latter contribute to the shift modestly. The variations of summer monsoonal circulation systems, including the South Asian High, the West Pacific Subtropical High, and the lower-level air flow, were analyzed. The results show that, in comparison with those induced by extratropical SSTs, the shifts induced by tropical SSTs bear more similarity to the observations and to the simulations with global SSTs prescribed. In particular, the observed SST shift in the tropical Pacific Ocean, rather than the Indian Ocean, contributed significantly to the shift of East Asian summer monsoon since the 1970s.

关键词： East Asian summer monsoon interdecadal shift SST agcm

Different Summer Rainfall Anomaly Patterns in Northeast China Associated with Two Kinds of El Ni?o Events

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Journal of Tropical Meteorology 2020年第2期26卷 223-230页

作者： WANG Qin LI Shuang-lin Civil Aviation Flight University of China GuanghanSichuan 618307 China Nansen-Zhu International Research Centre Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029 China

The relationship between summer rainfall anomalies in northeast China and two types of El Ni?o events is investigated by using observation data and an atmospheric general circulation model(agcm).It is shown that,for different types of El Ni?o events,there is different rainfall anomaly pattern in the following *** the following year of a typical El Ni?o event,there are remarkable positive rainfall anomalies in the central-western region of northeast China,whereas the pattern of more rainfall in the south end and less rainfall in the north end of northeast China easily appears in an El Ni?o Modoki *** reason for the distinct difference is that,associated with the different sea surface temperature anomalies(SSTA)along the equatorial Pacific,the large-scale circulation anomalies along east coast of East Asia shift northward in the following summer after El Ni?o Modoki *** by the anomalous anticyclone in Philippine Sea,southwesterly anomalies over eastern China strengthen summer monsoon and bring more water vapor to northeast ***,convergence and updraft is strengthened by the anomalous cyclone right in northeast China in typical El Ni?o *** moisture and atmospheric circulation conditions are favorable for enhanced ***,because of the northward shift,the anomalous anticyclone in the Philippine Sea in typical El Ni?o cases shifts to the south of Japan in Modoki years,and the anomalous cyclone in northeast China in typical El Ni?o cases shifts to the north of northeast China,leading to the"dipole pattern"of rainfall *** to the results of numerical experiments,we further confirm that the tropical SSTA in different types of El Ni?o event can give rise to observed rainfall anomaly patterns in northeast China.

关键词： typical El Niño El Niño Modoki summer rainfall in northeast China agcm

An Efficient Text Recognition System from Complex Color Image for Helping the Visually Impaired Persons

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Computer Systems Science & Engineering 2023年第7期46卷 701-717页

作者： Ahmed Ben Atitallah Mohamed Amin Ben Atitallah Yahia Said Mohammed Albekairi Anis Boudabous Turki MAlanazi Khaled Kaaniche Mohamed Atri Department of Electrical Engineering College of EngineeringJouf UniversitySakakaSaudi Arabia Laboratory of Informatics Gaspard-MongeA3SIESIEE ParisCNRSGustave Eiffel UniversityFrance LETI ENISUniversity of SfaxSfaxTunisia Remote Sensing Unit College of EngineeringNorthern Border UniversityArarSaudi Arabia Laboratory of Electronics and Microelectronics(LR99ES30) University of MonastirTunisia Department of Computer Engineering and Networks College of Computer and Information SciencesJouf UniversitySakakaSaudi Arabia College of Computer Sciences King Khalid UniversityAbhaSaudi Arabia

The challenge faced by the visually impaired persons in their day-today lives is to interpret text from *** this context,to help these people,the objective of this work is to develop an efficient text recognition system that allows the isolation,the extraction,and the recognition of text in the case of documents having a textured background,a degraded aspect of colors,and of poor quality,and to synthesize it into *** system basically consists of three algorithms:a text localization and detection algorithm based on mathematical morphology method(MMM);a text extraction algorithm based on the gamma correction method(GCM);and an optical character recognition(OCR)algorithm for text recognition.A detailed complexity study of the different blocks of this text recognition system has been *** this study,an acceleration of the GCM algorithm(agcm)is *** agcm algorithm has reduced the complexity in the text recognition system by 70%and kept the same quality of text recognition as that of the original *** assist visually impaired persons,a graphical interface of the entire text recognition chain has been developed,allowing the capture of images from a camera,rapid and intuitive visualization of the recognized text from this image,and text-to-speech *** text recognition system provides an improvement of 6.8%for the recognition rate and 7.6%for the F-measure relative to GCM and agcm algorithms.

关键词： Text recognition system GCM agcm OCR color images graphical interface