In this paper a new .mnultidimensional time series forecasting scheme based on the empirical orthogonal function (EOF) stepwise iteration process is introduced. The scheme is tested in a series of forecast experiments...In this paper a new .mnultidimensional time series forecasting scheme based on the empirical orthogonal function (EOF) stepwise iteration process is introduced. The scheme is tested in a series of forecast experiments of Nino3 SST anomalies and Tahiti-Darwin SO index. The results show that the scheme is feasible and ENSO predictable.展开更多
In order to improve the accuracy of prediction when using the empirical orthogonal function （EOF） method, this paper describes a novel approach for two-dimensional （2D） EOF analysis based on extrapolating both the...In order to improve the accuracy of prediction when using the empirical orthogonal function （EOF） method, this paper describes a novel approach for two-dimensional （2D） EOF analysis based on extrapolating both the spatial and temporal EOF components for long-term prediction of coastal morphological changes. The approach was investigated with data obtained from a process-based numerical model, COAST2D, which was applied to an idealized study site with a group of shore-parallel breakwaters. The progressive behavior of the spatial and temporal EOF components, related to bathymetric changes over a training period, was demonstrated, and EOF components were extrapolated with combined linear and exponential functions for long-term prediction. The extrapolated EOF components were then used to reconstruct bathymetric changes. The comparison of the reconstructed bathymetric changes with the modeled results from the COAST2D model illustrates that the presented approach can be effective for long-term prediction of coastal morphological changes, and extrapolating both the spatial and temporal EOF components yields better results than extrapolating only the temporal EOF component.展开更多
A three-dimensional variational method is proposed to simultaneously retrieve the 3-D atmospheric temperature and moisture profiles from satellite radiance measurements. To include both vertical structure and the hori...A three-dimensional variational method is proposed to simultaneously retrieve the 3-D atmospheric temperature and moisture profiles from satellite radiance measurements. To include both vertical structure and the horizontal patterns of the atmospheric temperature and moisture, an EOF technique is used to decompose the temperature and moisture field in a 3-D space. A number of numerical simulations are conducted and they demonstrate that the 3-D method is less sensitive to the observation errors compared to the 1-D method. When the observation error is more than 2.0 K, to get the best results, the truncation number for the EOF＇s expansion have to be restricted to 2 in the 1-D method, while it can be set as large as 40 in a 3-D method. This results in the truncation error being reduced and the retrieval accuracy being improved in the 3-D method. Compared to the 1-D method, the rms errors of the 3-D method are reduced by 48% and 36% for the temperature and moisture retrievals, respectively. Using the real satellite measured brightness temperatures at 0557 UTC 31 July 2002, the temperature and moisture profiles are retrieved over a region （20°-45°N, 100°- 125°E） and compared with 37 collocated radiosonde observations. The results show that the retrieval accuracy with a 3-D method is significantly higher than those with the 1-D method.展开更多
[Objective] Study on the spatial distribution of summer precipitation patterns and interannual and interdecadal variability. [Method] The summer precipitation patterns were obtained from standard field of summer preci...[Objective] Study on the spatial distribution of summer precipitation patterns and interannual and interdecadal variability. [Method] The summer precipitation patterns were obtained from standard field of summer precipitation data for 160 observation stations in China during 1951 -2000 by the utilization of empirical orthogonal function （EOF）, and characteristics of interannual and interdecadal variability were analyzed. [Result] The summer precipitation mainly distributes in eastern part of China; The 1 st, 2nd and 3rd EOF modes of spatial distribution are especially remarkable as well consistent with the results of previous reports about three rainfall patterns from analysis on the percentages of precipitation anomaly of summer. [Conclusion] There exists interannual and interdecadal variability for summer precipitation in China.展开更多
近年来,我国风能资源开发增长迅速,甘肃省风能资源储量在全国名列前茅。为降低风电企业投资的风险,需要对当地多年的风速状况进行评估。文中选用甘肃省79个台站1976年至2010年35年的风速资料,30个台站的历史沿革资料,采用T检验法、SNHT(...近年来,我国风能资源开发增长迅速,甘肃省风能资源储量在全国名列前茅。为降低风电企业投资的风险,需要对当地多年的风速状况进行评估。文中选用甘肃省79个台站1976年至2010年35年的风速资料,30个台站的历史沿革资料,采用T检验法、SNHT(Standard Normal Homogeneity Test)方法及经验正交分解方法(EOF)对甘肃省风速资料进行分析。T检验表明,甘肃省79个站35年的风速资料有3.98%的存在非均一性;资料分析结果表明,甘肃各地风速除陇中及定西部分地区略有上升外,大部分地区风速呈下降趋势,包括风能资源丰富的地区,且下降趋势较明显,其中河西祁连山区风速下降在0.13m/s.10a～0.26m/s.10a之间,河西东部地形平坦区域风速下降在0.13m/s.10a以下;陇南及陇东大部分地区风速下降在0.13m/s.10a以下。甘肃台站风速每十年变化量与本站1976～2010年平均风速比较结果显示:除陇中及定西部分地区风速略有上升,每十年上升在5%～10%之间外,河西祁连山区风速每十年下降在5%～15%之间,河西东部地形平坦区域风速每十年下降在5%以下;陇南及陇东大部分地区风速每十年下降在5%～10%之间。这是今后风电场投资必须要考虑与防范的风险因素之一。展开更多
文摘In this paper a new .mnultidimensional time series forecasting scheme based on the empirical orthogonal function (EOF) stepwise iteration process is introduced. The scheme is tested in a series of forecast experiments of Nino3 SST anomalies and Tahiti-Darwin SO index. The results show that the scheme is feasible and ENSO predictable.
基金the School of Engineering at Cardiff University for providing the financial support of a Ph D studentship to accomplish the research
文摘In order to improve the accuracy of prediction when using the empirical orthogonal function （EOF） method, this paper describes a novel approach for two-dimensional （2D） EOF analysis based on extrapolating both the spatial and temporal EOF components for long-term prediction of coastal morphological changes. The approach was investigated with data obtained from a process-based numerical model, COAST2D, which was applied to an idealized study site with a group of shore-parallel breakwaters. The progressive behavior of the spatial and temporal EOF components, related to bathymetric changes over a training period, was demonstrated, and EOF components were extrapolated with combined linear and exponential functions for long-term prediction. The extrapolated EOF components were then used to reconstruct bathymetric changes. The comparison of the reconstructed bathymetric changes with the modeled results from the COAST2D model illustrates that the presented approach can be effective for long-term prediction of coastal morphological changes, and extrapolating both the spatial and temporal EOF components yields better results than extrapolating only the temporal EOF component.
基金the 973 Program (Grant No. 2004CB418305)the National Natural Science Foundation of China(Grant No. 40575049).
文摘A three-dimensional variational method is proposed to simultaneously retrieve the 3-D atmospheric temperature and moisture profiles from satellite radiance measurements. To include both vertical structure and the horizontal patterns of the atmospheric temperature and moisture, an EOF technique is used to decompose the temperature and moisture field in a 3-D space. A number of numerical simulations are conducted and they demonstrate that the 3-D method is less sensitive to the observation errors compared to the 1-D method. When the observation error is more than 2.0 K, to get the best results, the truncation number for the EOF＇s expansion have to be restricted to 2 in the 1-D method, while it can be set as large as 40 in a 3-D method. This results in the truncation error being reduced and the retrieval accuracy being improved in the 3-D method. Compared to the 1-D method, the rms errors of the 3-D method are reduced by 48% and 36% for the temperature and moisture retrievals, respectively. Using the real satellite measured brightness temperatures at 0557 UTC 31 July 2002, the temperature and moisture profiles are retrieved over a region （20°-45°N, 100°- 125°E） and compared with 37 collocated radiosonde observations. The results show that the retrieval accuracy with a 3-D method is significantly higher than those with the 1-D method.
文摘[Objective] Study on the spatial distribution of summer precipitation patterns and interannual and interdecadal variability. [Method] The summer precipitation patterns were obtained from standard field of summer precipitation data for 160 observation stations in China during 1951 -2000 by the utilization of empirical orthogonal function （EOF）, and characteristics of interannual and interdecadal variability were analyzed. [Result] The summer precipitation mainly distributes in eastern part of China; The 1 st, 2nd and 3rd EOF modes of spatial distribution are especially remarkable as well consistent with the results of previous reports about three rainfall patterns from analysis on the percentages of precipitation anomaly of summer. [Conclusion] There exists interannual and interdecadal variability for summer precipitation in China.
文摘近年来,我国风能资源开发增长迅速,甘肃省风能资源储量在全国名列前茅。为降低风电企业投资的风险,需要对当地多年的风速状况进行评估。文中选用甘肃省79个台站1976年至2010年35年的风速资料,30个台站的历史沿革资料,采用T检验法、SNHT(Standard Normal Homogeneity Test)方法及经验正交分解方法(EOF)对甘肃省风速资料进行分析。T检验表明,甘肃省79个站35年的风速资料有3.98%的存在非均一性;资料分析结果表明,甘肃各地风速除陇中及定西部分地区略有上升外,大部分地区风速呈下降趋势,包括风能资源丰富的地区,且下降趋势较明显,其中河西祁连山区风速下降在0.13m/s.10a～0.26m/s.10a之间,河西东部地形平坦区域风速下降在0.13m/s.10a以下;陇南及陇东大部分地区风速下降在0.13m/s.10a以下。甘肃台站风速每十年变化量与本站1976～2010年平均风速比较结果显示:除陇中及定西部分地区风速略有上升,每十年上升在5%～10%之间外,河西祁连山区风速每十年下降在5%～15%之间,河西东部地形平坦区域风速每十年下降在5%以下;陇南及陇东大部分地区风速每十年下降在5%～10%之间。这是今后风电场投资必须要考虑与防范的风险因素之一。
