南极普里兹湾及其邻近海域水团研究

普里兹湾及其邻近海域是中国南大洋调查研究的传统优势海域与重点区域。围绕夏季表层水、冬季水、陆架水、绕极深层水、南极底层水、普里兹湾底层水、冰架水等研究海区主要水团的特征和分布,总结了前人在南极普里兹湾及其邻近海域基于调查资料开展的水团研究中所取得的成果。研究表明,前人在对陆架水的示性指标界定上,将陆架水是否区分为高盐陆架水和低盐陆架水存在较大争议,在高盐陆架水和普里兹湾底层水的定义上存在重叠;目前尚没有证据表明绕极深层水向南可以伸展到普里兹湾的陆架区域,也没有发现在普里兹湾附近海域生成南极底层水的直接证据。     

A bio-optical inversion model to retrieve absorption contributions and phytoplankton size structure from total minus water spectral absorption using genetic algorithm

We propose a bio-optical inversion model that retrieves the absorption contributions of phytoplankton and colored detrital matter(CDM),as well as the phytoplankton size classes(PSCs),from total minus water absorption spectra.The model is based on three-component separation of phytoplankton size structure and a genetic algorithm.The model performance was tested on two independent datasets(the NASA bio-Optical Marine Algorithm Dataset(NOMAD) and the northern South China Sea(NSCS) dataset).The relationships between the estimated and measured values were strongly linear,especially for aCDM(412),and the Root Mean Square Error(RMSE) of the CDM exponential slope(SCDM) was relatively low.Next,the inversion model was directly applied to in-situ total minus water absorption spectra determined by an underwater meter during a cruise in September 2008,to retrieve the phytoplankton size structure in the seawater.By comparing the measured and retrieved chlorophyll a concentrations,we demonstrated that total and size-specific chlorophyll a concentrations could be retrieved by the model with relatively high accuracy.Finally,we applied the bio-optical inversion model to investigate changes in phytoplankton size structure induced by an anti-cyclonic eddy in the NSCS.     

南极半岛东北海域表层沉积有机质来源及其沉积环境

采用气相色谱-质谱技术对南极半岛东北海域海底表层沉积物的总有机碳、有机质碳同位素(δ13 Corg)和生物标志化合物等进行了测试分析。研究区表层沉积物总有机碳TOC平均值高于现代深海沉积物中的平均含量。δ13 Corg的变化说明该海域有机碳来源呈海洋水生生物来源和陆源混合的特征。正构烷烃的峰型分布、主峰碳、饱和烃轻重比C-21/C+22和(C21+C22)/(C28+C29)、甾烷组合和藿烷组合证实研究区西部表层沉积物有机质来源以陆源高等植物为主,其陆源可能来自于附近的南极半岛和南舍得兰群岛;研究区东部表层沉积物有机质来源偏以海源为主,且以低等浮游生物、藻类及细菌生物等海源输入为主。碳优势指数(Carbon preference index,CPI)、奇偶优势指数(Odd-even Predominance,OEP)和甾烷C29ααα20S/(20S+20R)比值显示研究区D1-7站位和D5-9沉积物有机质演化程度较高,D5-2和D2-4站位的有机质演化程度低,其他站位介于中间状态。饱和烃中姥鲛烷、植烷及其比值(Pr/Ph)等组合显示研究区西部以氧化-弱还原的沉积环境为主,其可能是受高温低盐别林斯高晋海水流和附近火山喷发的影响所致;研究区东部以还原—强还原沉积环境为主,可能是受低温高盐的威德尔底层水(WSBW)和威德尔海深层水(WSDW)影响所致。     

“4D”技术及其应用

介绍“４Ｄ”（即数字地面模型、数字正射影像、数字栅格地图和数字线划地图）系列产品的生产流程、关键技术、及其在耕地保护、防灾减灾救灾和城市规划等方面的应用方法。     

Is it possible to detect earlier ionospheric precursors before large earthquakes using principal component analysis (PCA)?

The goal of this study was to determine whether principal component analysis (PCA) can be used to process GPS ionospheric total electron content (TEC) data on a monthly basis to identify early earthquake-associated TEC anomalies. PCA is applied to GPS (mean value of a month) ionospheric TEC records collected from the Japan GEONET system to detect TEC anomalies associated with 10 earthquakes in Japan (M?≥?6.0) from 2006 to 2007. According to the results, PCA was able to discriminate clear TEC anomalies in the months when all 10 earthquakes occurred. After reviewing the months when no M?≥?6.0 earthquake occurred but the geomagnetic storm activity was present, it is possible that the maximal principal eigenvalues PCA returned for these 10 earthquakes indicate earthquake-associated TEC anomalies. Previously, PCA has been used to discriminate earthquake-associated TEC anomalies recognized by other researchers who found that a statistical association between large earthquakes and TEC anomalies could be established in the 5 days before earthquake nucleation and in 24 h before earthquake; however, since PCA uses the characteristics of principal eigenvalues to determine earthquake-related TEC anomalies, it is possible to show that such anomalies existed earlier than this 5-day statistical window. In this paper, this is shown through the application of PCA to one-dimensional TEC data relating to the earthquake of 17 February 2007 (M?=?6.0). The analysis is applied to daily TEC and reveals a large principal eigenvalue (representative of an earthquake-associated anomaly) for 02 February, 15 days before the 17 February earthquake.     

Simulation of summer precipitation diurnal cycles over the Tibetan Plateau at the gray-zone grid spacing for cumulus parameterization

Climate Dynamics - The Tibetan Plateau (TP) is often referred to as the “water tower of Asia” or the “Third Pole”. It remains a challenge for most global and regional models...     

南亚高压区Rossby波能量向上穿越对流层顶传播的特征与机制

夏季平流层盛行强东风,Rossby波能量难以从对流层向上传播至平流层,而冬季平流层盛行西风,Rossby波能量容易上传,因此以往对Rossby波能量向平流层传播的研究多考虑冬季的情况.而事实上,因为夏季高原上空南亚高压反气旋环流,并非只有强东风存在,所以Rossby波能量也可能在南亚高压区向上传播,从而影响平流层的温度、风场及大气成分等.因此,本文利用ERA-interim逐日再分析资料,分析了1979-2015年夏季南亚高压区Rossby波能量穿越对流层顶传播的特征与机制.结果表明：Rossby波能量可以从南亚高压西北部的窗口区上传至平流层,最高可到达平流层顶,而在南亚高压的其他部分,Rossby波能量均不能穿越对流层顶上传或穿越对流层顶后无法继续上传.南亚高压西北区Rossby波能量可以穿越对流层顶传播的原因是盛行西风,且西风急流出现的频率很小,同时涡动热量通量异常引起的垂直分量的第一项对其上传有很大贡献.南亚高压东北区也盛行西风,然而Rossby波能量不能向上穿越对流层顶的原因是强西风出现频率较高,且温度脊与高度脊位相相近,不利于上传.南亚高压南部均盛行东风,在平流层中下层均为稳定层结,因此Rossby波能量很难上传.南亚高压西南区在对流层位于青藏高原环流的伊朗高原下沉区附近,层结稳定,并且温度脊超前于高度脊,所以Rossby波能量很难上传.而南亚高压东南区在对流层位于南海-西太平洋热带幅合带,层结不稳定,存在Rossby波能量较弱的上传,达到对流层顶后无法继续上传,该区域温度脊落后于高度脊的温压场配置也为Rossby波能量在对流层内的传播提供了条件.

     

A contrast of two typical LUCC processes and their driving forces in oases of arid areas: A case study of Sangong River Watershed at the northern foot of Tianshan Mountains

Aerial photographs taken in 1978 and 1987, Landsat TM images in 1998 as well as soil, hydrology and socio-economic data for the oases in Sangong River Watershed were processed by Remote Sensing (RS) and Geographic Information System (GIS). There are two typical agricultural land uses in oases, Farm-based Land Use with large-scale intensified agricultural activities (FLU) and Household Responsibility-based Land Use with small-scale activities (HRLU). The Index Model of Land Use/Land Cover Change (LUCC), Weighted Index Sum (WIS) and logistic stepwise regression model were established to contrast the two typical LUCC processes and their driving forces. The land use patterns were dominated by cropland and grassland for the entire region, and cropland, residential and industrial land were increasing stably. In the HRLU areas, woodland and grassland declined dramatically, but in the FLU areas, grassland decreased only by 12.0%, whereas woodland increased by 13.7%. LUCC was stronger in the earlier stage (1978–1987) than in the later stage (1987–1998) for the entire region. LUCC was more intense in the HRLU areas than in the FLU areas during the entire period (1978–1998). Policy was a key factor in the land use change, and water resources were a precondition in land use. Under the control of policy and water resources, the main human driving factors included population and economy, and the main natural restrictions were soil fertility and groundwater depth. Human driving factors controlled the land change in the HRLU areas, but natural restriction factors dominated in the FLU areas. In the mean time, intensification of LUCC in the region had some spatiotemporal implications with a fluctuation of impact factors.     

干湿循环下原状黄土抗压强度试验研究

黄土是干旱、半干旱条件下形成的,具有特殊结构的土,季节性的降雨和蒸发作用必将引起其力学性质和结构改变,从而造成其强度降低和变形增大的问题。通过单轴抗压强度试验探讨了黄土抗压强度与含水率、干湿循环次数的变化规律,借助SEM图像定性和定量分析了其强度变化的微观机制。试验结果表明：黄土单轴抗压强度随含水率的减小表现为非线性的增大;随干湿循环次数的增加而减小,经历多次干湿循环后趋于稳定;含水率增大和干湿循环次数的增加不仅仅会使得粗颗粒的接触方式改变与胶体物质和腐殖质数量减少,还会使得土体孔隙直径增大,大、中孔隙所占百分比之和明显增多,进而从微观结构阐述了土体宏观强度的变化规律。