潮汐混合对大西洋经圈翻转环流(AMOC)模拟影响的数值模拟研究

海洋中的潮汐混合对大西洋经圈翻转环流AMOC(Atlantic Meridional Overturning Circulation)模拟的影响是海洋环流模式研究的热点问题之一。本文采用IAP/LASG发展的气候系统海洋模式LICOM(LASG/IAP Climate system Ocean Model)及与海冰耦合模式进行了有无潮汐混合方案的试验,重点探讨了潮汐混合对AMOC强度模拟的影响。结果显示,引入潮汐混合后模拟的AMOC强度极大值比对照试验增加约1倍,更接近RAPID(Rapid Climate Change Programme)观测。而且,潮汐混合试验中模拟的AMOC上层环流深度(3200 m)比对照试验加深1000 m左右,同样更接近RAPID观测。海洋底部的垂直混合增强,使海洋层结变得更加不稳定,加强了北大西洋高纬地区,特别是拉布拉多海等地区的深对流,这是AMOC加强的直接原因。同时,潮汐混合试验中上层海洋环流也加强,增加了中低纬副热带高盐海水向高纬输送,使表层增密,海洋层结更加不稳定,也可以进一步增强AMOC。     

南海与邻近海洋的水通量交换

利用一个局地加密的全球海洋环流模式,给出位于细网格海域的南中国海与其邻近海洋之间水交换的年平均和月变化的定量结果。结果表明,南海与周围海洋交换的水通量受南海季风的影响较大,其中吕宋海峡的交换量最大,其次为南海南部边界的断面,再者依次为台湾海峡,民都洛海峡和巴拉巴克海峡,另外还对南海各个海峡的热通量,盐通量进行了估算。     

盐度对变化2014年东北太平洋“暖泡”的作用

A significant strong, warm "Blob"(a large circular water body with a positive ocean temperature anomaly)appeared in the Northeast Pacific(NEP) in the boreal winter of 2013–2014, which induced many extreme climate events in the US and Canada. In this study, analyses of the temperature and salinity anomaly variations from the Array for Real-time Geostrophic Oceanography(Argo) data provided insights into the formation of the warm"Blob" over the NEP. The early negative salinity anomaly dominantly contributed to the shallower mixed layer depth(MLD) in the NEP during the period of 2012–2013. Then, the shallower mixed layer trapped more heat in the upper water column and resulted in a warmer sea surface temperature(SST), which enhanced the warm"Blob". The salinity variability contributed to approximately 60% of the shallowing MLD related to the warm"Blob". The salinity anomaly in the warm "Blob" region resulted from a combination of both local and nonlocal effects. The freshened water at the surface played a local role in the MLD anomaly. Interestingly, the MLD anomaly was more dependent on the local subsurface salinity anomaly in the 100–150 m depth range in the NEP.The salinity anomaly in the 50–100 m depth range may be linked to the anomaly in the 100–150 m depth range by vertical advection or mixing. The salinity anomaly in the 100–150 m depth range resulted from the eastward transportation of a subducted water mass that was freshened west of the dateline, which played a nonlocal role.The results suggest that the early salinity anomaly in the NEP related to the warm "Blob" may be a precursor signal of interannual and interdecadal variabilities.     

道路网层次骨架控制的道路选取方法

提出了基于路网层次骨架控制的道路自动选取方法。首先,该方法以stroke为单位,利用中介中心性值对stroke进行层次结构划分;其次,采用结构特征识别完善道路层次骨架;第三,基于层次骨架间的连通关系建立逐层传递的stroke重要性计算模型;最后,通过该计算模型自上而下的逐层计算,得到stroke重要性,并据此完成道路网选取。采用3种典型道路网数据,对本方法与其他主要常规stroke选取方法进行对比,试验结果表明本方法不但对语义的依赖性极低,同时消除了中介中心性在评价道路重要性时对边缘道路的不利影响,在保持道路网整体结构和层次性上有较为明显的优势,可适用于各种形态的道路网选取。     

一个冰气相互作用数值模拟结果的可能统计解释

基于一个全球海-冰-气耦合模式的数值模拟结果,选取冬季格陵兰海海表面温度(SST)、海冰密集度、海表面感热通量等物理量以及3个相关区域海平面气压分别作经验正交函数展开,取第一模时间系数作相关分析。结果表明,上一年海冰密集度偏大(小)与来年的SST偏低(高)相联系,但二者同期相关性最大。当海气热通量交换变化超前一年时,其与SST相关性最大。模式最低层大气温度与海洋表面热通量之间的同时相关性最大,冬季模式最低层气温偏高(低)与海洋表面失去的感热、潜热通量偏少(多)相联系。气温、比湿都和冰岛低压区及格陵兰海的海平面气压相关性最强,冰岛低压气压偏低(高)与模式最低层气温和比湿偏高(低)相联系。所以,在海-冰-气年际尺度的相互作用中,主要关系是大气环流调整造成大气中云量和低层气温、湿度变化,进而影响海气界面上的通量交换,造成SST的变化。SST变化决定着海冰范围及海冰密集度的变化,但海冰变化时通过相变潜热的释放或吸收反过来对SST变化有较明显影响。     

用Argo温盐资料估计印度尼西亚贯穿流多年平均地转输送

利用Argo浮标资料，估计了2003—2007年期间印度尼西亚贯穿流（ITF）出口处114.5^οE断面上层(0—1000m)的地转流，并与WOA05资料进行对比。在114.5^οE断面上9.5^ο—18.5^οS之间，依据Argo资料计算的上层(0—1000m)地转流年平均输送为4.2Sv(1 Sv = 106m^3.s^-1)，比依据WOA05资料计算的流量大0.5Sv左右，与前人对IX1断面的估算接近。依据Argo资料计算的ITF的季节变化也与WOA05比较一致，最大输送都出现在7月份，可以达到10Sv，而冬季二者差异较大。比较了盐度资料的差异以及114.5^οE断面南侧缺测对估计ITF地转流输送的影响，发现盐度资料的改善可以改进对ITF地转输送量的估计，而断面南侧的缺测对ITF年平均输送的影响较小。因此，Argo资料可以作为监测ITF输送量的一种有效手段，特别是用于年平均流量的研究。     

全球气候模式中赤道东太平洋海表温度的季节循环：从CMIP5到CMIP6

The sea surface temperature(SST) seasonal cycle in the eastern equatorial Pacific(EEP) plays an important role in the El Ni?o–Southern Oscillation(ENSO) phenomenon. However, the reasonable simulation of SST seasonal cycle in the EEP is still a challenge for climate models. In this paper, we evaluated the performance of 17 CMIP6 climate models in simulating the seasonal cycle in the EEP and compared them with 43 CMIP5 climate models. In general, only CESM2 and SAM0-UNICON are able to successfully capture the annual mean SST characteristics,and the results showed that CMIP6 models have no fundamental improvement in the model annual mean bias.For the seasonal cycle, 14 out of 17 climate models are able to represent the major characteristics of the observed SST annual evolution. In spring, 12 models capture the 1–2 months leading the eastern equatorial Pacific region 1(EP1; 5°S–5°N, 110°–85°W) against the eastern equatorial Pacific region 2(EP2; 5°S–5°N, 140°–110°W). In autumn,only two models, GISS-E2-G and SAM0-UNICON, correctly show that the EP1 and EP2 SSTs vary in phase. For the CMIP6 MME SST simulation in EP1, both the cold bias along the equator in the warm phase and the warm bias in the cold phase lead to a weaker annual SST cycle in the CGCMs, which is similar to the CMIP5 results. However,both the seasonal cold bias and warm bias are considerably decreased for CMIP6, which leads the annual SST cycle to more closely reflect the observation. For the CMIP6 MME SST simulation in EP2, the amplitude is similar to the observed value due to the quasi-constant cold bias throughout the year, although the cold bias is clearly improved after August compared with CMIP5 models. Overall, although SAM0-UNICON successfully captured the seasonal cycle characteristics in the EEP and the improvement from CMIP5 to CMIP6 in simulating EEP SST is clear, the fundamental climate models simulated biases still exist.     

采用案例类比推理进行道路网智能选取

自动制图综合的智能化研究因受人类复杂思维制约,长期以来成为研究的薄弱环节。从人类学习和认知角度,借鉴人工智能领域基于案例推理学习的成果,提出一种基于案例类比推理的道路网智能选取新方法。该方法将制图专家对某区域道路网的交互选取结果作为参考标准,对其进行结构化描述并构建和转化为案例库;计算机采用一定的简化算法和泛化算法对该案例库进行分析和学习,获取检索效率更高和适应样本能力更强的案例模型库;计算机在对相似道路网自动选取时,根据获取的案例模型库,采用基于案例类比推理的方法,分析获取相应的解决方案,进而完成道路网智能选取。与已有研究成果相比,本方法以案例及其泛化模型来模拟专家思维,以计算机对案例模型的类比学习来进行相似道路网自动选取,弥补了传统道路网选取中智能性差的缺陷,为自动综合智能化研究找到了一条可行途径。论文最后对本方法的科学性和适用性进行了验证,并对实验结果做了分析和评价,同时指出了存在问题和进一步研究方向。     

Versions g1.0 and g1.1 of the LASGIAP Flexible Global Ocean–Atmosphere–Land System Model

The latest two versions of the IAP Flexible Global Ocean-Atmosphere-Land System (FGOALS) model- versions g1.0 and g1.1, are described in this study. Both two versions are fully coupled GCMs without any flux correction, major changes for g1.1 mainly lie in four aspects: (1) advection schemes for tracer in the ocean component model; (2) zonal filter scheme in high latitudes in the ocean component model; (3) coupling scheme for fresh water flux in high latitudes; and (4) an improved algorithm of airsea turbule...     

The flexible global ocean-atmosphere-land system model, Grid-point Version 2: FGOALS-g2

This study mainly introduces the development of the Flexible Global Ocean-Atmosphere-Land System Model: Grid-point Version 2 (FGOALS-g2) and the preliminary evaluations of its performances based on results from the pre-industrial control run and four members of historical runs according to the fifth phase of the Coupled Model Intercomparison Project (CMIP5) experiment design. The results suggest that many obvious improvements have been achieved by the FGOALS-g2 compared with the previous version,FGOALS-g1, including its climatological mean states, climate variability, and 20th century surface temperature evolution. For example,FGOALS-g2 better simulates the frequency of tropical land precipitation, East Asian Monsoon precipitation and its seasonal cycle, MJO and ENSO, which are closely related to the updated cumulus parameterization scheme, as well as the alleviation of uncertainties in some key parameters in shallow and deep convection schemes, cloud fraction, cloud macro/microphysical processes and the boundary layer scheme in its atmospheric model. The annual cycle of sea surface temperature along the equator in the Pacific is significantly improved in the new version. The sea ice salinity simulation is one of the unique characteristics of FGOALS-g2, although it is somehow inconsistent with empirical observations in the Antarctic.