利用散射计测量海面后向散射系数,并通过地球物理模型函数(geophysical model function, GMF)反演得到海面风场。目前散射计风场反演所采用的GMF一般只考虑雷达极化方式、雷达入射角、风速和相对风向对海面后向散射系数的影响,而相关研...利用散射计测量海面后向散射系数,并通过地球物理模型函数(geophysical model function, GMF)反演得到海面风场。目前散射计风场反演所采用的GMF一般只考虑雷达极化方式、雷达入射角、风速和相对风向对海面后向散射系数的影响,而相关研究表明海表温度(sea surface temperature, SST)对Ku波段散射计风场反演具有不可忽略的影响。文章利用海洋二号A卫星散射计(Haiyang-2AScatterometer,HY2A-SCAT)后向散射系数观测值、欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts, ECMWF)再分析风矢量和SST数据,采用人工神经网络方法,建立起一种SST相关的GMF (TNGMF)。对TNGMF进行分析后发现,海面后向散射系数随着SST的增加而增加,并且其增加幅度与雷达极化方式、风速有关。为了对比,文章使用相同数据集和相同方法建立了不包含SST的GMF (NGMF),将美国国家航天航空局散射计-2 (National Aeronautics and Space Administration Scatterometer-2, NSCAT2) GMF、TNGMF和NGMF分别用于HY2A-SCAT风场反演实验。试验结果表明,采用NSCAT2 GMF、NGMF反演得到的风速在低温时系统性偏小,在高温时系统性偏大;而TNGMF可较好地纠正SST对风速偏差均值的影响,从而提高反演风场质量。展开更多
Ocean Drilling Program (ODP) Site 807A was recovered from the Ontong-Java plateau, western equatorial Pacific. Quantitative analysis of planktonic foraminifera, combined with oxygen and carbon isotope data, reveals th...Ocean Drilling Program (ODP) Site 807A was recovered from the Ontong-Java plateau, western equatorial Pacific. Quantitative analysis of planktonic foraminifera, combined with oxygen and carbon isotope data, reveals the glacial-interglacial variations of sea-surface temperature and the upper water vertical structure in this region during the late Quaternary. Our results indicate that since 530 ka sea-surface temperature (SST) and the depth of thermocline (DOT) have changed significantly in the western Pacific warm pool (WPWP). The average glacial-interglacial annual SST difference was up to 4.2 ℃, and the DOT fluctuations could exceed more than 100 m, further suggesting the instability of the WPWP. The spectral analyses of SST and DOT reveal two dominating cyclicities—the typical 100 ka cycle and the semi-precessional cycle, which is significant in the tropical spectrum, indicating that late Quaternary paleoceanographic changes in the study area were influenced not only by a high latitude forcing but also by tropic-driving factors.展开更多
文摘利用散射计测量海面后向散射系数,并通过地球物理模型函数(geophysical model function, GMF)反演得到海面风场。目前散射计风场反演所采用的GMF一般只考虑雷达极化方式、雷达入射角、风速和相对风向对海面后向散射系数的影响,而相关研究表明海表温度(sea surface temperature, SST)对Ku波段散射计风场反演具有不可忽略的影响。文章利用海洋二号A卫星散射计(Haiyang-2AScatterometer,HY2A-SCAT)后向散射系数观测值、欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts, ECMWF)再分析风矢量和SST数据,采用人工神经网络方法,建立起一种SST相关的GMF (TNGMF)。对TNGMF进行分析后发现,海面后向散射系数随着SST的增加而增加,并且其增加幅度与雷达极化方式、风速有关。为了对比,文章使用相同数据集和相同方法建立了不包含SST的GMF (NGMF),将美国国家航天航空局散射计-2 (National Aeronautics and Space Administration Scatterometer-2, NSCAT2) GMF、TNGMF和NGMF分别用于HY2A-SCAT风场反演实验。试验结果表明,采用NSCAT2 GMF、NGMF反演得到的风速在低温时系统性偏小,在高温时系统性偏大;而TNGMF可较好地纠正SST对风速偏差均值的影响,从而提高反演风场质量。
文摘Ocean Drilling Program (ODP) Site 807A was recovered from the Ontong-Java plateau, western equatorial Pacific. Quantitative analysis of planktonic foraminifera, combined with oxygen and carbon isotope data, reveals the glacial-interglacial variations of sea-surface temperature and the upper water vertical structure in this region during the late Quaternary. Our results indicate that since 530 ka sea-surface temperature (SST) and the depth of thermocline (DOT) have changed significantly in the western Pacific warm pool (WPWP). The average glacial-interglacial annual SST difference was up to 4.2 ℃, and the DOT fluctuations could exceed more than 100 m, further suggesting the instability of the WPWP. The spectral analyses of SST and DOT reveal two dominating cyclicities—the typical 100 ka cycle and the semi-precessional cycle, which is significant in the tropical spectrum, indicating that late Quaternary paleoceanographic changes in the study area were influenced not only by a high latitude forcing but also by tropic-driving factors.
