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The Walker circulation (WC) has always been an important issue in atmospheric science research due to the association between the WC and tropical Pacific sea surface temperature (SST), and between the WC and ENSO events. In this paper, a new index-Omega index (OMGI) - is constructed for WC characterization based on the NCEP / NCAR reanalysis data of monthly mean vertical velocity in recent 70 years (1948-2017). Results show that the OMGI can accurately depict the variation characteristics of WC on seasonal, annual and decadal time-scales. There is a significant inverse correlation between the OMGI and equatorial eastern and central Pacific SST. Meanwhile, the peak of the OMGI appears ahead of the ENSO peak, and therefore is able to reflect the SST in the equatorial Pacific. Especially, in 35 ENSO events, the peak of the OMGI appears earlier than Ni?o 3.4 index for 19 times with 2.6 months ahead on average. In 16 El Ni?o events, the peak of the OMGI occurs ahead of the El Ni?o for 9 times with 4 months ahead on average. In 19 La Ni?a events, the OMGI peak arises 10 times earlier than the La Ni?a peak, with an average of 1.4 months ahead. OMGI shows obvious leading effect and stability over ENSO events with different strengths and types of single peak and multi peaks: the peak of the OMGI keeps about 2-3 months ahead of the ENSO. Compared with other WC indexes such as UWI and SPLI, OMGI has some advantages in the ability to describe WC changes and present the probability and thetime of prediction of ENSO event peaks. 相似文献
143.
以Zn(Ac)2.2H2O和NaOH为原料,十六烷基三甲基溴化胺(CTAB)为表面活性剂,采用水热法合成了不同形态的氧化锌。利用X-ray粉末衍射仪(Powder X-ray Diffractometer,XRD)、红外光谱仪(Infra-red Spectrometer,IR)、场发射扫描电镜表征所合成材料的结构和形貌。用紫外可见光度计、荧光光度计研究了氧化锌的光学性能。为了评估氧化锌的催化性能,进行了纳米氧化锌对乙酸和正丁醇合成乙酸正丁酯的催化实验。实验结果表明,纳米氧化锌对酯化反应具有很好的催化作用,催化活性与颗粒大小有一定的关系。 相似文献
144.
Xiaolong CHEN Zhun GUO Tianjun ZHOU Jian LI Xinyao RONG Yufei XIN Haoming CHEN Jingzhi SU 《Journal of Meteorological Research》2019,(1)
Climate sensitivity and feedbacks are basic and important metrics to a climate system. They determine how large surface air temperature will increase under CO_2 forcing ultimately, which is essential for carbon reduction policies to achieve a specific warming target. In this study, these metrics are analyzed in a climate system model newly developed by the Chinese Academy of Meteorological Sciences(CAMS-CSM) and compared with multi-model results from the Coupled Model Comparison Project phase 5(CMIP5). Based on two idealized CO_2 forcing scenarios, i.e.,abruptly quadrupled CO_2 and CO_2 increasing 1% per year, the equilibrium climate sensitivity(ECS) and transient climate response(TCR) in CAMS-CSM are estimated to be about 2.27 and 1.88 K, respectively. The ECS is near the lower bound of CMIP5 models whereas the TCR is closer to the multi-model ensemble mean(MME) of CMIP5 due to compensation of a relatively low ocean heat uptake(OHU) efficiency. The low ECS is caused by an unusually negative climate feedback in CAMS-CSM, which is attributed to cloud shortwave feedback(λSWCL) over the tropical Indo-Pacific Ocean.The CMIP5 ensemble shows that more negative λSWCL is related to larger increase in low-level(925–700 hPa)cloud over the tropical Indo-Pacific under warming, which can explain about 90% of λSWCL in CAMS-CSM. Static stability of planetary boundary layer in the pre-industrial simulation is a critical factor controlling the low-cloud response and λSWCL across the CMIP5 models and CAMS-CSM. Evidently, weak stability in CAMS-CSM favors lowcloud formation under warming due to increased low-level convergence and relative humidity, with the help of enhanced evaporation from the warming tropical Pacific. Consequently, cloud liquid water increases, amplifying cloud albedo, and eventually contributing to the unusually negative λSWCL and low ECS in CAMS-CSM. Moreover, the OHU may influence climate feedbacks and then the ECS by modulating regional sea surface temperature responses. 相似文献
145.
The ability of climate models to correctly reproduce clouds and the radiative effects of clouds is vitally important in climate simulations and projections. In this study, simulations of the shortwave cloud radiative effect(SWCRE) using the Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM) are evaluated. The relationships between SWCRE and dynamic–thermodynamic regimes are examined to understand whether the model can simulate realistic processes that are responsible for the generation and maintenance of stratus clouds. Over eastern China, CAMS-CSM well simulates the SWCRE climatological state and stratus cloud distribution. The model captures the strong dependence of SWCRE on the dynamic conditions. Over the marine boundary layer regions, the simulated SWCRE magnitude is weaker than that in the observations due to the lack of low-level stratus clouds in the model. The model fails to simulate the close relationship between SWCRE and local stability over these regions. A sensitivity numerical experiment using a specifically designed parameterization scheme for the stratocumulus cloud cover confirms this assertion. Parameterization schemes that directly depict the relationship between the stratus cloud amount and stability are beneficial for improving the model performance. 相似文献
146.
文章基于ASTER和Landsat-8OLI两种多光谱遥感数据,采用高光谱遥感技术混合调谐滤波(MTMF)、多光谱遥感技术相对吸收深度(RBD)、波段比值(BR)等方法提取了西藏多龙矿集区地堡那木岗斑岩型铜金矿床地表的蚀变矿物组合。其结果表明,基于ASTER数据的MTMF技术可将Al—OH矿物划分为白云母+高岭石/蒙脱石和地开石+蒙脱石+累托石两种组合,进一步可细分出斑岩型矿床多光谱遥感地表蚀变矿物组合并呈现出良好的分带特征:地堡那木岗铜金矿床自内而外依次为白云母+高岭石/蒙脱石→地开石+蒙脱石+累托石→Mg—OH类矿物组合,分别对应于前人野外调查所勘测到的的绢英岩化带+泥化带→泥化带→青磐岩化带,Fe3+矿物叠加于绢英岩化带、泥化带及其两带的叠合部位。所提取的多光谱遥感蚀变矿物组合分带特征对该区斑岩型铜金矿床的勘查工作提供了重要的遥感线索,对定位找矿靶区具有指导意义。 相似文献
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针对无人机倾斜摄影技术受遮挡影响较大和难以穿透植被茂密地区的问题,本文提出了城市复杂地形环境下倾斜模型结合LiDAR点云进行小区域大比例尺数字地形图的更新方法。首先采用五镜头六旋翼无人机分别以垂直和平行主要建筑物楼群方向进行2次全区域拍摄,以及无人机机载激光雷达全区域采集点云,并对高度不足10 m的别墅区进行单镜头低空补飞。然后融合倾斜影像点云与机载激光点云建模,经过3种建模方案对比,融合建模的倾斜三维模型的位置精度和模型质量均最优。最后基于此模型进行测图。精度评定结果表明,城市复杂地形环境下在飞行方案和像控点布设合理的情况下,通过倾斜三维模型采集的数字地形图的平面和高程精度完全满足并优于深圳市1∶1000数字地形图动态更新的精度指标。 相似文献
150.