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791.
792.
海啸波传播的线性和非线性特征及近海陆架效应影响的数值研究 总被引:3,自引:2,他引:1
浅水方程被广泛应用于海啸预警报业务及研究,而针对线性浅水方程与非线性浅水方程在不同海区水深地形条件下的适用范围、计算效率问题是海啸研究人员急需了解的。本文应用基于浅水方程的海啸数值预报模型就海啸波在南海、东海传播的线性、非线性特征以及陆架对其传播之影响进行了数值分析研究。海啸波在深水的传播表征为强线性特征,此时线性系统对海啸波幅的模拟计算具有较高的精度和效率,而弱的非线性特征及弱的色散特征对海啸波幅的预报影响甚微,可以忽略不计。海啸波传播至浅水大陆架后受海底坡度变化、海底粗糙度等因素影响,波动的非线性效应迅速传播、积累,与线性浅水方程计算的海啸波相比表现出较大差异,主要表现为:在南海区,水深小于100m时,海啸波首波以后的系列波动非线性特征比较明显,两者波幅差别较大,但首波波幅的区别不大,因此对于该区域在不考虑海啸爬高的情况下,应用线性系统计算得到的海啸波幅也可满足海啸预警报的要求;在东海区由于陆架影响,海啸波非线性特征明显增强,水深小于100m区域,首波及其后系列波波幅均差异较大,故在该区域必须考虑海啸波非线性作用。本文就底摩擦项对海啸波首波波幅的影响进行了数值对比分析,结果表明:底摩擦作用对海啸波首波波幅影响仅作用于小于100m水深。最后,该文通过敏感性试验,初步分析了陆架宽度及陆架边缘深度对海啸波波幅的影响,得出海啸波经陆架传播共振、变形后,海啸波幅的放大或减小与陆架的宽度及陆架边缘水深有关。 相似文献
793.
三峡库区生态屏障区土地利用规划生态效应评估 总被引:5,自引:2,他引:3
以地处三峡库区腹心地带的重庆市云阳县为例,基于土地利用多功能性,以Costanza等的生态系统服务价值测算方法及谢高地等制定的生态服务价值系数为基础,构建不同土地利用类型生态服务价值修正系数,从生态系统服务价值以及景观格局视角定量估算三峡库区生态屏障区土地利用规划生态效应。结果表明,以土地生态功能建设为导向的土地利用规划能够快速提升生态屏障区生态系统服务价值,增强屏障区调节气候、保持土壤、维护生物多样性等方面能力,云阳县三峡库区生态屏障区生态系统服务总价值从2010年的15.53亿元提升到2020年的19.98亿元,年均变化率达到2.87%;至2020年云阳县三峡库区生态屏障区初步构建一个以"林地为骨架,耕地、园地、草地为补充"的生态系统服务格局;同时,云阳县三峡库区生态屏障区生态系统服务价值及其调节服务和支持服务价值表现出显著地空间分异特征,其中磨刀溪流域生态系统服务价值提升幅度最大,澎溪河流域次之,长江沿岸生态服务系统价值保持稳定增长,而长滩河流域变化不大。 相似文献
794.
Evapotranspiration is a key parameter for water stress assessment as it is directly related to the moisture status of the soil-vegetation system and describes the moisture transfer from the surface to the atmosphere. With the launch of the Meteosat Second Generation geostationary satellites and the setup of the Satellite Application Facilities, it became possible to operationally produce evapotranspiration data with high spatial and temporal evolution over the entire continents of Europe and Africa. In the frame of this study we present an evaluation of the potential of the evapotranspiration (ET) product from the EUMETSAT Satellite Application Facility on Land Surface Analysis (LSA-SAF) for drought assessment and monitoring in Europe.To assess the potential of this product, the LSA-SAF ET was used as input for the ratio of ET to reference evapotranspiration (ET0), the latter estimated from the ECMWF interim reanalysis. In the analysis two case studies were considered corresponding to the drought episodes of spring/summer 2007 and 2011. For these case studies, the ratio ET/ET0 was compared with meteorological drought indices (SPI, SPEI and Sc-PDSI for 2007 and SPI for 2011) as well as with the anomalies of the fraction of absorbed photosynthetic active radiation (fAPAR) derived from remote sensing data. The meteorological and remote sensing indicators were taken from the European Drought Observatory (EDO) and the CARPATCLIM climatological atlas.Results show the potential of ET/ET0 to characterize soil moisture variability, and to give additional information to fAPAR and to precipitation distribution for drought assessment. The main limitations of the proposed ratio for drought characterization are discussed, including options to overcome them. These options include the use of filters to discriminate areas with a low percentage vegetation cover or areas that are not in their growing period and the use of evapotranspiration without water restriction (ETwwr), obtained as output of the LSA-SAF model instead of ET0. The ET/ETwwr ratio was tested by comparing its accumulated values per growing period with the winter wheat yield values per country published by Eurostat. The results point to the potential of using the remote sensing based LSA-SAF evapotranspiration and the ET/ETwwr ratio for vegetation monitoring at large scale, especially in areas where data is generally lacking. 相似文献
795.
Angular effect of MODIS emissivity products and its application to the split-window algorithm 总被引:1,自引:0,他引:1
Huazhong RenGuangjian Yan Ling ChenZhaoliang Li 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(4):498-507
The angular effects of emissivity are ignored in current land surface temperature (LST) products. As a result, the directionality of these LST products limits their further application in many fields. Accurate correction of the angular problem of LST products requires explicit understanding of the angular effects of emissivity at the pixel scale. Currently, nearly ten years of global emissivity products of MODIS are available. However, the pixel-scale directionality of emissivity has never been analyzed. By performing a statistical analysis of 5-year MODIS emissivity products over most of East Asia, we generated the empirical relationships between the directional emissivity, land cover, and seasonal variations. Two look-up tables (LUTs) of directional emissivity were created for typical land cover types and applied to the generalized split-window algorithm to modify the MODIS LST. The results showed that the angular effect of emissivity could introduce a significant bias of −1-3 K to the 1 km resolution LST. Finally, the spatial scale effects of emissivity were analyzed, and it was found that the temperature differences caused by scale effects fell within +/−0.5 K for most pixels if 5 km emissivity was used in 1 km LST retrieval. Therefore, wide use of the LUTs can be expected. 相似文献
796.
介绍了TEQC及其辅助软件QCVIEW 32的功能以及在DOS系统下的操作命令,并运用这两种软件对试验数据进行了GPS多路径误差分析,得出了影响多路径误差的部分因素,试验证明,TEQC可以方便地用于多路径误差分析,并能取得良好的效果。 相似文献
797.
798.
利用抚州市11个气象观测站的气温、降水量与蒸发量资料,计算分析气候干早指数时空变化特征,同时分析降水、降水距平、蒸降差等特征变化,以揭示1962-2009年抚州地区气候干湿变化状况.结果表明,抚州市各地的干湿变化基本一致,干早指数的变化是波动的且呈下降趋势.20世纪60年代、80年代中后期至90年代中期,是抚州市干早出... 相似文献
799.
Effects of anthropogenic disturbance on the abundance and size of epibenthic jellyfish Cassiopea spp
Jellyfish blooms in pelagic systems appear to be increasing on a global scale because of anthropogenic impacts, but much less is known about the link between human activities and epibenthic jellyfish abundance. The aim of this study was to investigate whether the epibenthic jellyfish, Cassiopea spp., were found in greater abundance, and attained larger sizes, in coastal habitats adjacent to high human population densities compared to sites adjacent to uninhabited areas on Abaco Island, Bahamas. Cassiopea spp. were found to be significantly more dense and larger in areas with high human population densities. Ambient nutrient levels and nutrient content of seagrass were elevated in high human population density sites, and may be one mechanism driving higher abundance and size of Cassiopea spp. Cassiopea spp. may have important effects on community structure and ecosystem function in critical coastal ecosystems (e.g., seagrass beds), and their impacts warrant further study. 相似文献
800.