Quantitative analysis of the feedback induced by the freshwater flux in the tropical Pacific using CMIP5     

Hai Zhi  Rong-Hua Zhang  Pengfei Lin  Lanning Wang 《大气科学进展》2015,32(10):1341-1353

Freshwater flux (FWF) directly affects sea surface salinity (SSS) and hence modulates sea surface temperature (SST) in the tropical Pacific. This paper quantifies a positive correlation between FWF and SST using observations and simulations of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) to analyze the interannual variability in the tropical Pacific. Comparisons among the displacements of FWF, SSS and SST interannual variabilities illustrate that a large FWF variability is located in the west-central equatorial Pacific, covarying with a large SSS variability, whereas a large SST variability is located in the eastern equatorial Pacific. Most CMIP5 models can reproduce the fact that FWF leads to positive feedback to SST through an SSS anomaly as observed. However, the difference in each model's performance results from different simulation capabilities of the CMIP5 models in the magnitudes and positions of the interannual variabilities, including the mixed layer depth and the buoyancy flux in the equatorial Pacific. SSS anomalies simulated from the CMIP5 multi-model are sensitive to FWF interannual anomalies, which can lead to differences in feedback to interannual SST variabilities. The relationships among the FWF, SSS and SST interannual variabilities can be derived using linear quantitative measures from observations and the CMIP5 multi-model simulations. A 1 mm d-1 FWF anomaly corresponds to an SSS anomaly of nearly 0.12 psu in the western tropical Pacific and a 0.11°C SST anomaly in the eastern tropical Pacific.  相似文献   

Simulation of the equatorially asymmetric mode of the Hadley circulation in CMIP5 models     

Juan Feng  Jianping Li  Jianlei Zhu  Fei Li  Cheng Sun 《大气科学进展》2015,32(8):1129-1142

The tropical Hadley circulation (HC) plays an important role in influencing the climate in the tropics and extra-tropics. The realism of the climatological characteristics, spatial structure, and temporal evolution of the long-term variation of the principal mode of the annual mean HC (i.e., the equatorially asymmetric mode, EAM) was examined in model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The results showed that all the models are moderately successful in capturing the HC's climatological features, including the spatial pattern, meridional extent, and intensity, but not the spatial or temporal variation of the EAM. The possible reasons for the poor simulation of the long-term variability of the EAM were explored. None of the models can successfully capture the differences in the warming rate between the tropical Southern Hemisphere (SH) and Northern Hemisphere (NH), which is considered to be an important driver for the variation of the AM. Most of the models produce a faster warming in the NH than in the SH, which is the reverse of the observed trend. This leads to a reversed trend in the meridional gradient between the SH and NH, and contributes to the poor simulation of EAM variability. Thus, this aspect of the models should be improved to provide better simulations of the variability of the HC. This study suggests a possible reason for the poor simulation of the HC, which may be helpful for improving the skill of the CMIP5 models in the future.  相似文献   

Synergistic contribution of precipitation anomalies over northwestern India and the South China Sea to high temperature over the Yangtze River Valley   总被引：1，自引：0，他引：1  

Ge Liu  Renguang Wu  Shuqing Sun  Huimei Wang 《大气科学进展》2015,32(9):1255-1265

This study explores the characteristics of high temperature anomalies over eastern China and associated influencing factors using observations and model outputs. Results show that more long-duration (over 8 days) high temperature events occur over the middle and lower reaches of the Yangtze River Valley (YRV) than over the surrounding regions, and control most of the interannual variation of summer mean temperature in situ. The synergistic effect of summer precipitation over the South China Sea (SCS) region (18°-27°N, 115°-124°E) and the northwestern India and Arabian Sea (IAS) region (18°-27°N, 60°-80°E) contributes more significantly to the variation of summer YRV temperature, relative to the respective SCS or IAS precipitation anomaly. More precipitation (enhanced condensational heating) over the SCS region strengthens the western Pacific subtropical high (WPSH) and simultaneously weakens the westerly trough over the east coast of Asia, and accordingly results in associated high temperature anomalies over the YRV region through stimulating an East Asia-Pacific (EAP) pattern. More precipitation over the IAS region further adjusts the variations of the WPSH and westerly trough, and eventually reinforces high temperature anomalies over the YRV region. Furthermore, the condensational heating related to more IAS precipitation can adjust upper-tropospheric easterly anomalies over the YRV region by exciting a circumglobal teleconnection, inducing cold horizontal temperature advection and related anomalous descent, which is also conducive to the YRV high temperature anomalies. The reproduction of the above association in the model results indicates that the above results can be explained both statistically and dynamically.  相似文献   

Estimating Sea-Level Allowances for Atlantic Canada using the Fifth Assessment Report of the IPCC     

Li Zhai  Blair J.W. Greenan  John Hunter  Thomas S. James  Guoqi Han  Phillip MacAulay 《大气与海洋》2015,53(5):476-490

Abstract

Sea-level allowances at 22 tide-gauge sites along the east coast of Canada are determined based on projections of regional sea-level rise for the Representative Concentration Pathway 8.5 (RCP8.5) from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5) and on the statistics of historical tides and storm surges (storm tides). The allowances, which may be used for coastal infrastructure planning, increase with time during the twenty-first century through a combination of mean sea-level rise and the increased uncertainty of future projections with time. The allowances show significant spatial variation, mainly a consequence of strong regionally varying relative sea-level change as a result of glacial isostatic adjustment (GIA). A methodology is described for replacement of the GIA component of the AR5 projection with global positioning system (GPS) measurements of vertical crustal motion; this significantly decreases allowances in regions where the uncertainty of the GIA models is large. For RCP8.5 with GPS data incorporated and for the 1995–2100 period, the sea-level allowances range from about 0.5?m along the north shore of the Gulf of St. Lawrence to more than 1?m along the coast of Nova Scotia and southern Newfoundland.  相似文献   

Influence of future tropical cyclone track changes on their basin-wide intensity over the western North Pacific: Downscaled CMIP5 projections     

Chao Wang  Liguang Wu 《大气科学进展》2015,32(5):613-623

The possible changes of tropical cyclone(TC) tracks and their influence on the future basin-wide intensity of TCs over the western North Pacific(WNP) are examined based on the projected large-scale environments derived from a selection of CMIP5(Coupled Model Intercomparison Project Phase 5) models. Specific attention is paid to the performance of the CMIP5 climate models in simulating the large-scale environment for TC development over the WNP. A downscaling system including individual models for simulating the TC track and intensity is used to select the CMIP5 models and to simulate the TC activity in the future.The assessment of the future track and intensity changes of TCs is based on the projected large-scale environment in the21 st century from a selection of nine CMIP5 climate models under the Representative Concentration Pathway 4.5(RCP4.5)scenario. Due to changes in mean steering flows, the influence of TCs over the South China Sea area is projected to decrease,with an increasing number of TCs taking a northwestward track. Changes in prevailing tracks and their contribution to basin-wide intensity change show considerable inter-model variability. The influences of changes in prevailing track make a marked contribution to TC intensity change in some models, tending to counteract the effect of SST warming. This study suggests that attention should be paid to the simulated large-scale environment when assessing the future changes in regional TC activity based on climate models. In addition, the change in prevailing tracks should be considered when assessing future TC intensity change.  相似文献   

基于主成分分析的相对重力观测零漂和固体潮提取     

于红娟  郭金运  李九龙  穆大鹏  孔巧丽 《大地测量与地球动力学》2015,35(5):906-910

利用主成分分析PCA提取2014-08-15~23CG-5相对重力仪静态相对观测的零点漂移和固体潮。结果显示,PCA提取的零点漂移值与最小二乘线性拟合结果非常一致,其差仅在10-2μGal/d量级;PCA估算的固体潮值与CG-5重力仪内部软件提供的固体潮模型计算值统计结果基本一致,两者之差均小于8μGal,均方根均小于5μGal。  相似文献   

热带海气相互作用对大气BSISO年际振荡的影响     

林爱兰  LITim  李春晖  梁建茵  LUOJing-Jia 《海洋学报(英文版)》2011,30(4):62-73

利用卫星观测OLR资料以及海气耦合数值模拟试验结果,从每年波-频分析结果提取了各种传播模态的强度指数序列,分析了热带北半球夏季季节内振荡(BSISO)各种传播模态的年际变化谱特征,探讨了热带各海区海气相互作用对其影响。主要结果如下:赤道外西传波和印度洋北传波以准2 a为显著振荡周期,赤道东传波、南海北传波和西太平洋北传波则都包含准2 a和准5 a两种周期,南海北传波是5种指数中惟一以准5 a为最主要周期振荡的模态。热带印度洋、西太平洋、东太平洋各海区海气相互作用对各指数准2 a振荡、准5 a振荡既有加强作用,也有削弱作用。各海区比较而言,对赤道东传波准2 a和准5 a振荡、南海北传波准2 a和准5 a振荡起最大加强作用的是西太平洋海区海气相互作用;对赤道外西传波准2 a振荡、西太平洋北传波准2 a和准5 a振荡起最大加强作用的是印度洋海区海气相互作用。  相似文献   

岛屿地形对热带气旋强度影响的数值模拟研究     

班浩然  端义宏 《中国海洋大学学报(自然科学版)》2011,41(3):1-10

本文用理想数值模拟分析的方法,在MM5模式中构造对称初始涡旋,在理想的环境场中发展为成熟的TC并移动经过从台湾岛抽象出的岛屿地形,揭示岛屿对TC强度和结构影响的机理。结果表明,理想模拟试验的方法对TC强度及结构变化的模拟具有很好的可靠性和客观性;TC中心登岛至到达岛屿山顶过程中,由于岛屿地形的抬升作用使得垂直方向上产生了局地的狭管收缩效应,使得TC在通过时强度短暂加强;TC在过岛过程中,风速垂直结构以及暖心结构的对称性会因地形的抬升和扰动影响而破坏,同时二者的大值区范围缩小;TC在过岛时,暖心结构在中高层分裂成一大一小2个部分,低层暖心偏离TC低压中心而伸向地面,TC由准正压系统变为斜压系统,使得TC整体强度减弱;次生低压对翻山后的TC中心的吸引融合加速了其过山后的北折过程;TC过岛后强度减弱十分明显,这是由于岛屿地形对环流摩擦阻力较大,对水汽供应的减弱和阻断,以及对TC对称结构的破坏。  相似文献   

中国近海蒸发波导的数值模拟与预报研究     

陈莉  高山红  康士峰  吴增茂 《中国海洋大学学报(自然科学版)》2011,(Z1):1-8

利用中尺度大气模式MM5对2007年中国近海大气蒸发波导进行了全年的高分辨的数值模拟。模拟结果统计表明,整个海域蒸发波导的平均出现概率约为90%。本文重点关注强度较大的蒸发波导,详细分析了其季节分布特征及其与海洋环流和海面气象条件的相关关系。研究发现,25°N以南的开阔海域的蒸发波导出现概率全年都较高,而以北的东海西北部、黄海与渤海,蒸发波导的出现概率呈现明显的季节特征;蒸发波导的空间分布受中国近海海洋环流的强烈影响,存在1个与黑潮区域相一致的带状波导高出现概率区域,台湾暖流、黄海暖流和对马暖流使得在某些季节相应海域蒸发波导出现概率高于其周围海域。此外,本文还基于WRF模式及其3DVAR系统构建了大气波导数值预报系统,尝试对中国东南海域的蒸发波导进行数值预报。  相似文献   

遥感技术在矿山开采动态监测中的应用——以豫西某铝土矿矿集区为例     

魏也纳  赵鸿燕 《地域研究与开发》2011,30(2)

以像西某铝土矿矿集区为试验区,以SPOT-5、资源二号卫星、QuickBird影像为数据源,提出矿山开采动态遥感监测的技术流程,并对试验区铝土矿开采状况进行动态遥感监测.根据基准年及现状年的监测结果,在基准年至现状年的3年间,试验区铝土矿开采量急剧增加,存在越界和界外开采现象,开采秩序一度比较混乱;现状年与基准年相比,越界和界外已停采面积均大幅增加,开采秩序好转;至现状年大多数铝土矿采场未进行复垦和环境治理.研究结果表:研究中采用的集3S技术于一体的矿业开发与矿山地质环境遥感监测技术方法是有效可行的,对其他矿山开采的动态遥感监测具有一定的借鉴意义;监测结果可为矿山的合理开发及可持续发展提供决策依据.  相似文献