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991.
J. C. Hargreaves D. J. T. Carter P. D. Cotton J. Wolf 《Journal of Atmospheric & Ocean Science》2002,8(1):41-66
This paper describes the development and application of a technique for using satellite altimeter measurements as boundary data to drive the nearshore spectral wave model, SWAN. The aim was to assess the impact in coastal areas of extreme events or changes in offshore climatology and to extend the usefulness of satellite altimetry further inshore.
For the purpose of verifying the technique, three test areas where both bathymetry and some in situ data were available were chosen. The technique could, potentially, be applied to any coastal location where there is bathymetric information although, as the results reported in this paper show, intelligence must be used in adapting the methodology for different sites. It is also necessary to have information on the local wind field from either models or measurements.
The experiments at the three test areas demonstrated that there is not a simple relationship between the offshore wave height climate and the inshore climate in a particular region. Important complicating factors are bathymetry, tidal range and incident wave angle. As was most clearly demonstrated in the Carmarthen Bay test area, bathymetric complexity leads to high spatial variation in the amount of wave energy dissipated close to the coast. In the study of extreme wave events described in this paper the exact value of the local wind field was not found to be critical.
This work was a first trial combining wave climatology derived from satellite altimetry with a third generation coastal wave model so was necessarily experimental. The general trends and patterns of spatial variation obtained are encouraging but there remains significant, unquantifiable uncertainty in the results. Better observations of nearshore waves, improved understanding of the joint probability distribution of water level and waves as well as more knowledge of future climate change would all improve accuracy. 相似文献
For the purpose of verifying the technique, three test areas where both bathymetry and some in situ data were available were chosen. The technique could, potentially, be applied to any coastal location where there is bathymetric information although, as the results reported in this paper show, intelligence must be used in adapting the methodology for different sites. It is also necessary to have information on the local wind field from either models or measurements.
The experiments at the three test areas demonstrated that there is not a simple relationship between the offshore wave height climate and the inshore climate in a particular region. Important complicating factors are bathymetry, tidal range and incident wave angle. As was most clearly demonstrated in the Carmarthen Bay test area, bathymetric complexity leads to high spatial variation in the amount of wave energy dissipated close to the coast. In the study of extreme wave events described in this paper the exact value of the local wind field was not found to be critical.
This work was a first trial combining wave climatology derived from satellite altimetry with a third generation coastal wave model so was necessarily experimental. The general trends and patterns of spatial variation obtained are encouraging but there remains significant, unquantifiable uncertainty in the results. Better observations of nearshore waves, improved understanding of the joint probability distribution of water level and waves as well as more knowledge of future climate change would all improve accuracy. 相似文献
992.
The ability of the Tropical Rainfall Measuring Mission Microwave Imager(TRMM/TMI)forcloud liquid water(CLW)retrieval has been demonstrated in this study.Due to the greatsensitivity of the TMI 85.5 GHz channels to CLW,the liquid water path(LWP)ofnonprecipitating clouds over land can be successfully estimated using the VDISORT model basedon the iteration steps.Both the vertical-polarized 85. 5 GHz single-channel method and thepolarization-difference of 85.5 GHz method were applied to the LWP estimates over land regionsduring the Huaihe River Basin Energy and Water Cycle Experiment(HUBEX)in China.Theretrieval results show reasonable agreement with the ground-based microwave radiometermeasurements.When the surface emissivity or skin temperature is difficult to be made sure,thepolarization-difference method shows advantages of providing estimates of LWP especially for lowclouds because of its extremely insensitiveness to the surface skin temperature. 相似文献
993.
双向卫星时频传递系统与应用 总被引：2，自引：0，他引：2
系统地阐述了双向卫星时频传递（TWSTFT）系统的原理、误差因素和结构实现，对系统的模块、流程操作进行了说明，并介绍了TWSTFT在国家授时中心的应用，最后提出了TWSTFT在我国的发展设想。 相似文献
994.
The value of ocean reflections of GPS signals to enhance satellite altimetry: data distribution and error analysis 总被引：4，自引：0，他引：4
The time and space distribution of general reflection altimetry from two satellites (senders and receivers) via the the oceans surface is examined with specific reference to GPS senders and two current receiving satellites. While a considerable enhancement of conventional altimeter coverage is possible in all configurations if the reflection signals can be used, repeating passes of these (with GPS senders) having reasonably small cycle times (days to tens of days) occur only if the receiving orbit is nearly polar. Results of an analysis of the fundamental geometry show that over a large range of reflection angles the error of recovered sea heights depends almost entirely on the errors in the delay signal and the radial error of the receiving satellite (using current estimates of GPS orbit accuracies). The most critical element is the precision of the delay measurement. Both it and the accuracy of the receiving orbit should be below the decimeter level for the technique to achieve its full potential. 相似文献
995.
996.
997.
This study aims at investigating the value added by an explicit representation of floodplain processes in hydraulic models, by comparing the results of a pure 1D model to the ones of an integrated 1D-2D model. The analysis is performed on a 96 km reach of the River Po (Italy). For this test site, two different model structures (1D and 1D-2D) are implemented and compared. The models are first calibrated using high water marks of a high magnitude event and then validated by means of a coarse resolution space-borne flood extent map of a low-magnitude event. The explicit inclusion of 2D features strongly improves the performance of the model, both in terms of accuracy and robustness. The possible causes of this behaviour are investigated and some statements are drawn based on the analysis of the features of the two flood events. Some general conclusions on the effect of the choice between 1D and 2D models arise from the analysis of the calibration-validation procedure. In this context a new measure of fit is proposed, to be used if binary (wet/dry) observations are available and is proven to be able to better distinguish among different sets of model parameters. Lastly, the study also shows the ability of timely low resolution satellite imagery to assist the selection of the most appropriate hydraulic model structure. 相似文献
998.
采用2000～2010年的陆地卫星TM数据,选取叶绿素a作为主要水质参数对浙江省德清市境内的水体富营养化程度进行反演。在同步实测数据缺乏的条件下,基于波段特征的比值法可以有效地进行叶绿素a的反演,对于反演结果分析总结德清地区水质污染情况并分析原因。 相似文献
999.
自然语言空间查询是智能信息检索在GIS领域的扩展。自然语言的自由灵活性在降低用户查询难度的同时,也对查询语句的规则匹配增加了难度。鉴于此,提出基于编辑距离的规则匹配模型。在词语层面,计算编辑相似度和语义相似度提供候选项,通过用户选择来建立未登录词与空间词库的匹配关系;在语句层面,应用编辑距离的思想来实现未登录句式的规则匹配。最后,开发了规则匹配工具,通过实验验证了模型的可行性。 相似文献
1000.
新一代"图谱合一"的星载遥感传感器"推扫式宽视场成像光谱仪"设置了CH18(8.125~8.825μm)和CH19(8.925~9.275μm)这2个波长在10μm以内的热红外通道用于地温反演。为了验证传统的针对10~14μm大气窗口的分裂窗算法在8.0~9.3μm大气窗口的适应性,介绍了基于Sobrino,FrancaCracknell和Becker算法的3种分裂窗算法;针对8.0~9.3μm大气窗口的分裂窗波段设置进行了参数计算公式的修正;并结合MODTRAN提供的热带模型、中纬度夏季模型、中纬度冬季模型、极地夏季模型、极地冬季模型和1976美国标准大气等6种标准大气模型,验证了各算法的地温反演精度。结果表明,FrancaCracknell和Becker算法的误差在2 K以内,可以较好地移植于CH18和CH19的分裂窗反演地温;但现行的3种分裂窗算法都难以保证地温误差小于1 K的要求。 相似文献