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81.
Using the Met Office Global and Regional Ensemble Prediction System (MOGREPS) implemented at the Korea Meteorological Administration (KMA), the effect of doubling the ensemble size on the performance of ensemble prediction in the warm season was evaluated. Because a finite ensemble size causes sampling error in the full forecast probability distribution function (PDF), ensemble size is closely related to the efficiency of the ensemble prediction system. Prediction capability according to doubling the ensemble size was evaluated by increasing the number of ensembles from 24 to 48 in MOGREPS implemented at the KMA. The initial analysis perturbations generated by the Ensemble Transform Kalman Filter (ETKF) were integrated for 10 days from 22 May to 23 June 2009. Several statistical verification scores were used to measure the accuracy, reliability, and resolution of ensemble probabilistic forecasts for 24 and 48 ensemble member forecasts. Even though the results were not significant, the accuracy of ensemble prediction improved slightly as ensemble size increased, especially for longer forecast times in the Northern Hemisphere. While increasing the number of ensemble members resulted in a slight improvement in resolution as forecast time increased, inconsistent results were obtained for the scores assessing the reliability of ensemble prediction. The overall performance of ensemble prediction in terms of accuracy, resolution, and reliability increased slightly with ensemble size, especially for longer forecast times. 相似文献
82.
Song-Hu Wang Xu Zhou Hui Zhang Ji-Lin Zhou Hui-Gen Liu Ze-Yang Meng Jun Ma Tian-Meng Zhang Zhou Fan Hu Zou 《天文和天体物理学研究(英文版)》2014,(3):345-356
In January,2008 the Chinese Small Telescope ARray(CSTAR) was successfully deployed at Dome A,Antarctica.Because CSTAR consists of four static14.5 cm telescopes pointing at the same 4.5°× 4.5°field around the south celestial pole,diurnal motion can be seen in its field of view.The stars are centered at different positions in different exposure frames.During four months of continuous observations during the polar night of 2008,about 0.3 million i-band images were obtained.In the latest version of the released photometric catalog,the effects of diurnal motion of the stars on the static CSTAR optical system can be obviously found.In this work,we update the CSTAR catalog by carefully analyzing and correcting the systematic errors caused by diurnal motion of stars on imperfectly flat-fielded frames. 相似文献
83.
Hui Zhao Jing-Xiu Wang Jun Zhang Chi-Jie Xiao National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2005,5(5):443-447
Employing the Poincare index of isolated null-points in a vector field, we worked out a mathematical method of searching for 3D null-points in coronal magnetic fields. After introducing the relevant differential topology, we test the method by using the analytical model of Brown & Priest. The location of null-point identified by our method coincides precisely with the analytical solution. Finally we apply the method to the 3D coronal magnetic fields reconstructed from an observed MDI magnetogram of a super-active region (NOAA 10488). We find that the 3D null-point seems to be a key element in the magnetic topology associated with flare occurrence. 相似文献
84.
ZHANG Huiyuan LIU Guihuan WANG Jinnan WAN Jun 《中国地理科学(英文版)》2007,17(2):179-185
The ecological protection of the watersheds in China is being confronted with a lot of problems such as soil and water erosion, water pollution at present. Therefore watershed eco-compensation is becoming a question of common interest. Based on the analyses of the major problems and their origins in the watershed protection in China, the paper discusses the concerned policies including relative rules and laws, financial policies and water right transaction policies. Simultaneously the paper reviews the practices carried out in China, including the ecological construction project in the western China, the trans-provincial eco-compensation practice and the small watershed eco-compensation practice. According to the present situation of eco-compensation practices and the future policy requirement, this paper finally puts forward four key problems to be solved in the watershed eco-compensation of China in the future. 相似文献
85.
Fog Detection over China’s Adjacent Sea Area by using the MTSAT Geostationary Satellite Data 总被引:1,自引:0,他引:1
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A fog threshold method for the detection of sea fog from Multi-function Transport Satellite (MTSAT1R) infrared (IR) channel data is presented.This method uses principle component analysis (PCA),texture analysis,and threshold detection to extract sea fog information.A heavy sea fog episode that occurred over China’s adjacent sea area during 7 8 April 2008 was detected,indicating that the fog threshold method can effectively detect sea fog areas nearly 24 hours a day.MTSAT-1R data from March 2006,June 2007,and April 2008 were processed using the fog threshold method,and sea fog coverage information was compared with the meteorological observation report data from ships.The hit rate,miss rate,and false alarm rate of sea fog detection were 66.1%,27.3%,and 33.9%,respectively.The results show that the fog threshold method can detect the formation,evolution,and dissipation of sea fog events over period of time and that the method has superior temporal and spatial resolution relative to conventional ship observations.In addition,through MTSAT-1R data processing and a statistical analysis of sea fog coverage information for the period from 2006 to 2009,the monthly mean sea fog day frequency,spatial distribution and seasonal variation characteristics of sea fog over China’s adjacent sea area were obtained. 相似文献
86.
Jun Ma ;Richard de Grijs ;Zhou Fan ;Soo-Chang Rey ;Zhen-Yu Wu ;Xu Zhou ;Jiang-Hua Wu ;Zhao-Ji Jiang ;Jian-Sheng Chen ;Kyungsook Lee ;Sangmo Tony Sohn 《天体物理学报》2009,(6):641-652
Mayall Ⅱ = G1 is one of the most luminous globular clusters (GCs) in M31. Here, we determine its age and mass by comparing multicolor photometry with theoretical stellar population synthesis models. Based on far- and near-ultraviolet GALEX photometry, broad-band UBVRI, and infrared JHKs 2MASS data, we construct the most extensive spectral energy distribution of G 1 to date, spanning the wavelength range from 1538 to 20 000A. A quantitative comparison with a variety of simple stellar population (SSP) models yields a mean age which is consistent with G1 being among the oldest building blocks of M31 and having formed within ~1.7 Gyr after the Big Bang. Irrespective of the SSP model or stellar initial mass function adopted, the resulting mass estimates (of order 10^7M⊙) indicate that GI is one of the most massive GCs in the Local Group. However, we speculate that the cluster's exceptionally high mass suggests that it may not be a genuine GC. Our results also suggest that G1 may contain, on average, (1.65±0.63) × 10^2L⊙ far-ultraviolet-bright, hot, extreme horizontal-branch stars, depending on the adopted SSP model. In addition, we demonstrate that extensive multi-passband photometry coupled with SSP analysis enables one to obtain age estimates for old SSPs that have similar accuracies as those from integrated spectroscopy or resolved stellar photometry, provided that some of the free parameters can be constrained independently. 相似文献
87.
88.
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89.
ZHAO Xiaojian WU Yuezhong DUAN Jun QIAO Gengbiao CHEN Denghui WANG Xingan 《《地质学报》英文版》2014,88(Z2):249-250
Please?refer?to?the?attachment(s)?for?more?details. 相似文献
90.
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