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801.
多普勒雷达资料在冷涡强对流天气中的同化应用试验 总被引:3,自引:0,他引:3
应用WRF模式的三维变分同化系统(WRF-3DVAR),对沈阳多普勒天气雷达资料在东北冷涡暴雨个例中的同化应用进行了试验.研制了多普勒雷达资料质量控制系统,实现了对径向风和反射率因子的直接同化,不但可以反演中尺度三维气象要素场,而且可以为模式提供初始场.以天气尺度资料为背景场同化多普勒雷达资料,WRF-3DVAR可以较好地反演冷涡中尺度对流系统的三维结构,反演的地面强对流辐散气流及在对流层中层涡旋都符合中尺度系统概念模型,通过与实际地面探测资料进行了对比,风场环流基本接近,同化了雷达资料的气象要素场可为预报业务提供较好的包含中小尺度系统的实时三维分析场.通过冷涡个例同化试验,应用WRF-3DVAR同化雷达资料后,中尺度模式对对流降水的预报总体有正的影响,对强对流中的一些中小尺度雨团的预报也略有改善. 相似文献
802.
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804.
以甘肃干旱区连作5年和轮作1年的苜蓿(Medicago sativa)地土壤为研究对象,对不同耕作方式下土壤团粒结构、容重、含水量指标进行研究。结果表明:在轮作和连作模式下,随着土壤深度的增加,0.25mm土壤团粒质量在干筛和湿筛处理下均降低,0.25mm团粒累积质量越大,分形维数越小。在浸水条件下,粒径为0.5~0.25mm的土壤团聚体含量最高,其它粒径团聚体含量依粒径的增大而降低。轮作土壤含水量呈现先增加后降低、最后再增加的变化过程;0~60cm土层水分含量最高(13.881%),60~80cm土层含水量下降到较低值(10.343%),80~100cm土层水分迅速恢复(13.811%)。连作和轮作土壤容重随土壤深度均呈现依次增大变化,连作最大值为1.425%比最小值高出17.6%,轮作最大值1.432%比最小值高出18.7%。 相似文献
805.
The Purulia carbonatite, ‘carbonatite’-‘alkali-pyroxenite’-‘apatite-magnetite rock’ association, is located at Beldih area
of Purulia district, West Bengal and falls within the 100 km long Northern Shear Zone (NSZ). Published literature suggests
that the Purulia carbonatite was formed by the process of liquid immiscibility from under-saturated silicate parent magma.
However, no silica under-saturated rocks like ijolite, nepheline-syenite etc. is known from the area. The trace element geochemistry
(Ba/La, Nb/Th, Nb/Pb and Y/Ce ratios in the present study) also does not support this view. Present study indicates that the
Purulia carbonatite is enriched in ΣREE and incompatible elements but the carbonatite is also poorer in Nb, Th and Pb compared
to the world average of calicocarbonatites. The lower value of Nb is characteristics of carbo(hydro)thermal carbonatite where
carbonatite is associated with alkali-pyroxenite and suggests probable origin of the carbonatite as carbothermal residua evolved
from an unknown parentage. However, the field, petrographic and geochemical data indicate the genesis of this carbonatite
from a primary carbonatitic magma of mantle decent. The 87Sr/86Sr ratio of the carbonatite and apatite separated from the carbonatite (∼0.703) implies primary magmatic derivation of the
Purulia carbonatite. Close similarity of the apatite of the apatite-magnetite rock with the mantle apatite (of type Apatite
B) indicates that they are also of primary magmatic origin. The present work portrays a unique example where primary magmatic
carbonatite is associated with the alkali-pyroxenite. 相似文献
806.
Doppler weather radar based nowcasting of cyclone Ogni 总被引:3,自引:0,他引:3
Soma Sen Roy V. Lakshmanan S. K. Roy Bhowmik S. B. Thampi 《Journal of Earth System Science》2010,119(2):183-199
In this paper, we describe offline analysis of Indian Doppler Weather Radar (DWR) data from cyclone Ogni using a suite of
radar algorithms as implemented on NEXRAD and the advanced algorithms developed jointly by the National Severe Storms Laboratory
(NSSL) and the University of Oklahoma. We demonstrate the applicability of the various algorithms to Indian radar data, the
improvement in the quality control and evaluate the benefit of nowcasting capabilities in Indian conditions. New information
about the tropical cyclone structure, as derived from application of the algorithms is also discussed in this study. 相似文献
807.
Short-Term Solar Flare Prediction Using Predictor Teams 总被引:1,自引:0,他引:1
A short-term solar flare prediction model is built using predictor teams rather than an individual set of predictors. The information provided by the set of predictors could be redundant. So it is necessary to generate subsets of predictors which can keep the information constant. These subsets are called predictor teams. In the framework of rough set theory, predictor teams are constructed from sequences of the maximum horizontal gradient, the length of neutral line and the number of singular points extracted from SOHO/MDI longitudinal magnetograms. Because of the instability of the decision tree algorithm, prediction models generated by the C4.5 decision tree for different predictor teams are diverse. The flaring sample, which is incorrectly predicted by one model, can be correctly forecasted by another one. So these base prediction models are used to construct an ensemble prediction model of solar flares by the majority voting rule. The experimental results show that the predictor team can keep the distinguishability of the original set, and the ensemble prediction model can obtain better performance than the model based on the individual set of predictors. 相似文献
808.
A. K. Sen 《Astrophysics》2010,53(4):560-569
The deflection of a ray of light passing close to a gravitational mass is generally calculated from the null geodesic which
the light ray (photon) follows. However, there is an alternate approach, where the effect of gravitation on the ray of light
is estimated by considering the ray to be passing through a material medium. Calculations have been done in this paper, following
the latter approach, to estimate the amount of deflection due to a static non-rotating mass. The refractive index of such
a material medium, has been calculated in a more rigorous manner in the present work, and the final expression for the amount
of deflection calculated here is claimed to be more exact than all other expressions derived so far, using material medium
approach. Based on this expression, the amount of deflection for a sun grazing ray has also been calculated. The exact amount
of deflection can be performed in a number of ways, without the material medium approach. However, the method presented here
using the material medium approach and without any weak field approximation is believed to be original. 相似文献
809.
Hai-Juan Cui Hai-Guang Xu Jun-Hua Gu Jing-Ying Wang Li-Yi Gu Yu Wang Zhen-Zhen Qin Tao An 《中国天文和天体物理学报》2010,10(4)
By creating and analyzing two dimensional gas temperature and abundance maps of the RGH 80 compact galaxy group with high-quality Chandra data,we detect a high-abundance (■0.7 Z⊙) arc,where the metal abundance is significantly higher than the surrounding regions by ■0.3Z⊙.This structure shows tight spatial correlations with the member galaxy PGC 046529,as well as with the arm-like feature identified on the X-ray image in the previous work of Randall et al.(2009).Since no apparent signature of AGN activity i... 相似文献
810.
马坞金矿分布于岷-礼成矿带的东部,矿体产于中泥盆统浅变质碎屑岩中,受断裂破碎蚀变带的控制。围岩蚀变以中-低温热液蚀变为主,蚀变强度与金矿化强度呈正相关;矿区共圈定6条矿脉,沿走向及倾向具有尖灭再现、局部膨大缩小的特点,沿裂隙发育的矿脉金品位较高。 相似文献