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251.
Monthly prediction of tropical cyclone activity over the South China Sea using the FGOALS-f2 ensemble prediction system
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本研究基于新一代FGOALS-f2动力集合预测系统35年(1981-2015年)的热带气旋历史回报试验对南海台风季(7-11月)热带气旋活动超前10天的月预测技巧进行评估,并对2020年南海台风季热带气旋活动进行了实时月预测尝试.结果表明:FGOALS-f2能较好地预测南海热带气旋路径密度演变特征,预测的热带气旋生成个... 相似文献
252.
GPS positioning precision is affected by various error sources, and traditional combinations of GPS carrier phase observations have their own limitations such as the wide-lane, the narrow-lane and the ionospheric-free combinations. To obtain the optimal positioning precision, a new linear combination method is addressed through the variance-covariance (VCV) of the GPS multi-frequency carrier phase combination equations, and the impact of the positioning precision is analyzed with the changing of the observation errors deduced by the law of error propagation. For the high precision positioning with only one carrier phase combination, the optimal combination method is deduced and further validated by an example of a baseline resolution with 60 km length. The result indicates that this method is the simplest, and the positioning precision is the best. Therefore, it is useful for long baseline quick positioning for different precision requirements in various distances. 相似文献
253.
Xia Li Yihan Zhang Xiaoping Liu Yimin Chen 《International journal of geographical information science》2013,27(9):1667-1687
This article presents a new method of assimilating process context information into change detection for monitoring land use changes. The accurate information about land use changes is important for implementing many global and regional environmental models. Two types of models have been independently developed to obtain such information, including change detection models (e.g. pixel-to-pixel comparison, post-classification comparison and object-based change analysis) and simulation models (e.g. cellular automata (CA) and agent-based modelling). These models may have limitations in capturing land use dynamics when used alone. In this study, the ensemble Kalman filter is used to obtain the best estimate of land use changes by combining remote-sensing observations with urban simulation. Urban simulation is able to provide process context information such as diffusion and coalescence of urban development. This type of complementary information is useful for improving the performance of change detection. Compared with traditional change detection models, this integrated model has the potential to improve the performance of change detection in terms of accuracies and landscape metrics. For example, the assimilating (MLC + CA) method can show improvement of the total accuracy and the kappa coefficient by 2.5–5.2% and 3.6–7.4%, respectively, in this study. 相似文献
254.
WU Yue PAN Yong FAN Yimin WANG Xiaojun 《地球空间信息科学学报》2007,10(4):245-249
GPS positioning precision is affected by various error sources, and traditional combinations of GPS carrier phase observations have their own limitations such as the wide-lane, the narrow-lane and the ... 相似文献
255.
Summary Three dimensional numerical simulations of the Australian West Coast Trough were conducted using a mesoscale model. These
simulations represent the process of formation, development and disappearance of the trough and highlight the role of surface
features in trough behaviour. Strong land surface heating strengthens the trough whereas topography and sea surface temperatures
are of marginal importance. Diurnal variations in surface heating between the land and ocean lead to the trough line oscillating
around the coast whereas its more general eastward movement is synoptically controlled. The sea breeze circulation influences
local trough orientation through maritime cooling.
Received December 23, 1999 Revised November 7, 2000 相似文献
256.
Some features associated with Eastern China Precipitation (ECP), in terms of mean climatology, sea-sonal cycle, interannual
variability are studied based on monthly rainfall data. The rainfall behavior over Eastern China has fine spatial structure
in the seasonal variation and interannual variability. The revealed characteristics of ECP motivate us dividing Eastern China
into four sub—regions to quantify significant lag—correlations of the rainfalls with global sea surface temperatures (SSTs)
and to study the ocean’s pre-dominant role in forcing the eastern China summer monsoon rainfalls. Lagged correlations between
the mid—eastern China summer monsoon rainfalls (MECSMRs) and the global SSTs, with SST leading to rain-fall, are investigated.
The most important key SST regions and leading times, in which SSTs are highly corre-lated with the MECSMRs, are selected.
Part of the results confirms previous studies that show links between the MECSMRs and SSTs in the eastern equatorial Pacific
associated with the El Nino — Southern Oscillation (ENSO) phenomenon. Other findings include the high lag correlations between
the MECSMRs and the SSTs in the high and middle latitude Pacific Ocean and the Indian Ocean, even the SSTs over the Atlantic
Ocean, with SST leading—time up to 4 years. Based on the selected SST regions, regression equa-tions are developed by using
the SSTs in these regions in respective leading time. The correlation coefficient between the observed rainfalls and regressed
rainfalls is over 0.85. The root mean square error (RMSE) for regressed rainfall is around 65% of the standard deviation and
about 15% of the mean rainfall. The regression equation has also been evaluated in a forecasting mode by using independent
data. Discussion on the consistence of the SST—rainfall correlation with circulation field is also presented.
This work was jointed supported by Chinese Academy of Sciences under Grant “Hundred Talents” for “Validation of Coupled Climate
models” and by U.S. Department of Energy under Grant DEFG0285ER 60314 to SUNY at Stony Brook. The authors are grateful to
Professor R. D. Cess at SUNY, Stony Brook for his supports. 相似文献
257.
Xiaohong Wang Yushu Gao Yimin Wang S.I. Andreev 《Geostandards and Geoanalytical Research》2003,27(3):251-257
A research project involving the preparation of three Co-rich crust reference materials (GSMC-1 to 3) has been preliminarily completed. The samples were collected from the eastern and central Pacific seamount zones and their main chemical composition is MnO2 . After the raw materials were dried in ambient air and at low temperature (60-100 C), they were ground in a ball mill to form a well-mixed powder. The proportion of particle size fractions of < 74 μm and < 3 μm was over 98% and 50% respectively. The homogeneity of the materials was tested using wavelength dispersive X-ray fluorescence spectrometry (WD-XRF). The relative standard deviation (% RSD) of the measurements for all the selected elements in forty sub-samples randomly taken from the bottles was less than 0.4%. Sixteen laboratories from Germany, Russia, France, Australia and China participated in the collaborative analysis programme. Fifty seven elements or constituents were analysed, and among those, forty six elements were certified in each sample. The sum of contents of the major and minor elements or components was 99.5% for GSMC-1, 99.6% for GSMC-2 and 99.2% for GSMC-3. 相似文献
258.
季节转换期间副热带高压带形态变异及其机制的研究 Ⅲ:热力学诊断 总被引:5,自引:1,他引:5
利用NCEP/NCAR再分析资料从能量收支的角度探讨了气候平均状态下副热带高压形态变异和季节转换的物理机制。在考察温度场和加热场季节变化的基础上 ,发现中国江南地区春季降水所形成的非绝热加热源非常显著 ,该热源对后期亚洲季节转换有影响。副热带高压脊面附近经向温度梯度反转取决于温度脊所在纬度位置的变化。温度脊北移是由脊轴北侧的增温率大于脊轴附近的增温率而造成的。热力学方程诊断结果表明 ,亚洲各季风区 (孟加拉湾、南海和南亚 )季节转换的热力机制不同。导致孟加拉湾温度脊显著北跳的主要因素在季风爆发初期是经向暖平流 ,爆发以后是下沉运动 ;引起南海地区经向温度梯度反转的因素有经向暖平流、纬向暖平流和江南地区的非绝热加热 ,特别是经向暖平流的贡献更大 ;造成南亚季风区经向温度梯度逆转的原因是下沉增温。 相似文献
259.
260.