1998年东亚夏季风环流相互作用的低频耦合模态及其位相特征

利用1998年SCSMEX试验期降水观测资料和NCEP／NCAR再分析资料，将物理量场在降水EOF分析得到的时间系数上展开，分析东亚夏季风环流低频变化特征。在揭示环流及我国东部降水异常观测事实的基础上，研究了它们之间相互作用的低频耦合模态及其可能机理，并讨论了低频位相变化与长江流域降水的关系，指出暴雨期次级环流是高低空环流相互作用的可能纽带。     

2003年广东省夏季的异常高温天气及气候背景

对2003年夏季广东省出现的异常高温天气时空分布特点及其异常的原因进行了分析，用小波分析研究了高温期的低频振荡，并用EOF和相关分析研究高温天气的气候特征及其气候背景。结果表明，2003年广东夏季的高温天气主要出现在7月初-8月中旬初。除雷州半岛以外的广东其余地区均出现异常高温，且高温日数大多比历年同期偏多1．2倍。高温天气具有明显的阶段性变化，存在60—80天左右的季节内振荡。影响高温天气的主要系统为副热带高压，当菲律宾附近同时有热带气旋活动时，有利于广东出现异常的高温天气。2003年7月乌拉尔山以西和鄂霍次克海附近地区异常偏强的阻塞高压及前冬太平洋海温距平呈厄尔尼诺的分布型，有利于西北太平洋副高异常偏强，位置偏南，持久控制江南到华南。广东高温天气始于5月，结束于10月，主要发生在7-8月份，具有相当的同步性。从1960年代起，高温天气主要发生在1960年代初、1980年代末到1990年代初、1990年代末至今。     

A cloud mask methodology for high resolution remote sensing data combining information from high and medium resolution optical sensors

This study presents a novel cloud masking approach for high resolution remote sensing images in the context of land cover mapping. As an advantage to traditional methods, the approach does not rely on thermal bands and it is applicable to images from most high resolution earth observation remote sensing sensors. The methodology couples pixel-based seed identification and object-based region growing. The seed identification stage relies on pixel value comparison between high resolution images and cloud free composites at lower spatial resolution from almost simultaneously acquired dates. The methodology was tested taking SPOT4-HRVIR, SPOT5-HRG and IRS-LISS III as high resolution images and cloud free MODIS composites as reference images. The selected scenes included a wide range of cloud types and surface features. The resulting cloud masks were evaluated through visual comparison. They were also compared with ad-hoc independently generated cloud masks and with the automatic cloud cover assessment algorithm (ACCA). In general the results showed an agreement in detected clouds higher than 95% for clouds larger than 50 ha. The approach produced consistent results identifying and mapping clouds of different type and size over various land surfaces including natural vegetation, agriculture land, built-up areas, water bodies and snow.     

The Impact of the Tropical Indian Ocean on South Asian High in Boreal Summer

The tropical Indian Ocean (TIO) is warmer than normal during the summer when or after the El Nio decays. The present study investigates the impact of TIO SST on the South Asian High (SAH) in summer. When the TIO is warmer, the SAH strengthens and its center shifts southward. It is found that the variations in the SAH cannot be accounted for by the precipitation anomaly. A possible mechanism is proposed to explain the connection between the TIO and SAH: warmer SST in the TIO changes the equivalent potential temperature (EPT) in the atmospheric boundary layer (ABL), alters the temperature profile of the moist atmosphere, warms the troposphere, which produces significant positive height anomaly over South Asia and modifies the SAH. An atmospheric general circulation model, ECHAM5, which has a reasonable prediction skill in the TIO and South Asia, was selected to test the effects of TIO SST on the SAH. The experiment with idealized heating over the TIO reproduced the response of the SAH to TIO warming. The results suggest that the TIO-induced EPT change in the ABL can account for the variations in the SAH.     

Dynamics of dissolved organic carbon after a cyanobacterial bloom in hypereutrophic Lake Taihu (China)

To establish the influence of the cyanobacterial bloom collapse on the characteristics of dissolved organic carbon (DOC) in Lake Taihu, high-molecular-weight dissolved organic matter (HMW-DOM), with sizes between 1 kDa and 0.5 μm, were collected using cross-flow ultrafiltration, from three different eutrophic regions. Isolated HMW-DOM was further characterized by atomic carbon to nitrogen ratio and neutral sugars composition by gas chromatography and mass spectrometry. The results indicated that the cyanobacterial cell lysis induced by nitrate depletion is the likely mechanism for DOC release. The relatively high DOC level was associated with the high chlorophyll a concentration in Meiliang Bay, one of the most eutrophic bays in the northern part of the lake. However, no significant correlations were observed between chlorophyll a concentration and HMW-DOC concentration during the demise of the cyanobacterial bloom in Lake Taihu. No significant differences were found in the HMW-DOC concentration among the three sampling sites, which were selected to represent different eutrophic status. However, a significant difference in the HMW-DOC concentration was found between October 2009 and January 2010 in all three sampling sites (p = 0.02). The HMW-DOC release may be attributed to the cyanobacterial cell lysis after the peak of summer bloom. The similarity in neutral sugar composition between the HMW-DOM and cyanobacterial exopolysaccharides suggests that the cyanobacterial bloom is the source of HMW-DOM. However, the significant correlation between the carbon to nitrogen ratio in HMW-DOM and chlorophyll a concentration was only observed in Meiliang Bay, which implies that apart from the cyanobacteria-derived DOC, a fraction of DOC was from riverine input. The decline of the cyanobacterial bloom also changed the overall DOM pool, leading to a shift in the component of HMW-DOM from a C-enriched material to an N-enriched material, as revealed by the variation in the carbon to nitrogen ratios. Overall, these results demonstrate that the quantitative and qualitative DOM is affected by the post-cyanobacterial bloom in Lake Taihu.     

Gas exsolution and flow during supersaturated water injection in porous media: II. Column experiments and continuum modeling

Degassing and in situ development of a mobile gas phase takes place when an aqueous phase equilibrated with a gas at a pressure higher than the subsurface pressure is injected in water-saturated porous media. This process, which has been termed supersaturated water injection (SWI), is a novel and hitherto unexplored means of introducing a gas phase in the subsurface. We give herein a first macroscopic account of the SWI process on the basis of continuum scale simulations and column experiments with CO₂ as the dissolved gas. A published empirical mass transfer correlation [Nambi IM, Powers SE. Mass transfer correlations for nonaqueous phase liquid dissolution from regions with high initial saturations. Water Resour Res 2003;39(2):1030. doi:10.1029/2001WR000667] is found to adequately describe non-equilibrium transfer of CO₂ between the aqueous and gas phases. Remarkably, the dynamics of gas-water two-phase flow, observed in a series of SWI experiments in homogeneous columns packed with silica sand or glass beads, are accurately predicted by traditional two-phase flow theory and the corresponding gas relative permeability is determined. A key consequence of this finding, namely that the displacement of the aqueous phase by gas is compact at the macroscopic scale, is consistent with pore scale simulations of repeated mobilization, fragmentation and coalescence of large gas clusters (i.e., large ganglion dynamics) driven entirely by mass transfer. The significance of this finding for the efficient delivery of a gas phase below the water table is discussed in connection to the alternative process of in situ air sparging, and potential advantages of SWI are highlighted.     

太原基准地震台数字化形变观测仪器干扰源调查

太原基准地震台数字化形变观测仪器伸缩仪和体应变仪记录的分钟值固体潮曲线上叠加有锯齿状的高频干扰,为探寻干扰源,对附近的抽水井、高压输电线、溶洞及煤矿进行调查分析,发现其对观测仪器的影响均不明显,认为与山洞下面可能存在的裂隙带有关。     

一次水汞观测高值异常的分析研究

2009年9月份之前,聊古一井水汞观测值在正常范围内波动,9月1日聊古1井水汞观测中出现高值异常,经过重复观测,水汞浓度是观测背景值的22倍.通过对流体测项其他敏感组分的分析和仪器运行情况的检查,没有发现异常.对观测环境现场调查发现,8月28日1支水银温度计不慎被打破,随后在不同环境下进行水汞对比观测分析,认为是水银温...     

贵阳地区太阳紫外辐射变化特征及主要影响因子分析

利用贵阳地区近6年太阳紫外辐射的观测资料及相关的气象因子,分析了该地区太阳紫外辐射的变化特征。结果表明,贵阳地区紫外辐射逐时平均最大值为21W.m-2（四级强度）,瞬时最大值为26.4W.m-2,未出现很强辐射（五级）的情况;4～9月出现强紫外辐射的时段较长,在10：00～15：00可达四级;13：00强紫外辐射在4～...     

日本9级和缅甸7.2级地震热辐射表现特征

应用中国静止气象卫星热红外遥感亮温资料获得其相对功率谱信息,对大范围全时段的相对功率谱信息进行了分析,其结果为:日本9.0级和缅甸7.2级地震发生前存在显著的亮温变化,震前6个月左右异常开始出现,相对变化幅度达10倍以上;这两次地震的异常区域大小和时间变化形态存在明显差异,可能是地质和气候环境所致.