The land use and land cover change database and its relative studies in China

In the mid-1990s, we established the national operative dynamic information serving systems on natural resources and environment. During building the land-use/land-cover change (LUCC) database for the mid-1990s, 520 scenes of remotely sensed images of Landsat Thematic Mapper (TM) were interpreted into land-use/land-cover categories at scale of 1:100,000 under overall digital software environment after being geo-referenced and ortho-rectified. The vector map of land-use/land-cover in China at the scale of 1:100,000 was recently converted into a 1-km raster database that captures all of the high-resolution land-use information by calculating area percentage for each kind of land use category within every cell. Being designed as an operative dynamic information serving system, monitoring the change in land-use/land-cover at national level was executed. We have completed the updating of LUCC database by comparing the TM data in the mid-1990s with new data sources received during 1999–2000 and 1989–1990. The LUCC database has supported greatly the national LUCC research program in China and some relative studies are incompletely reviewed in this paper.     

EFFECTS OF TROPOPAUSE AND POTENTIAL VORTICITY ANOMALY ON FRONTOGENESIS

A two-dimensional,semi-geostrophic numerical model incorporating the tropopause andstratosphere is used to investigate the effects of a positive potential vorticity anomaly and latentheat release on the frontogenetic process and the structure of the resulting frontal zone.It isdemonstrated that(1)the inclusion of tropopause and stratosphere significantly changes the frontalstructure only in the upper levels;(2)a clearly defined quasi-equivalent barotropic structure and aregion of upward motion of finite width appear when a positive potential vorticity anomaly exists onthe warm side of the maximum baroclinity in the lower troposphere,especially when it is locatedon the south edge of the baroclinic zone;(3)the above mentioned structure deteriorates as thefrontogenesis proceeds in a dry atmosphere but can be maintained in a moist frontogenetic processwith condensational heating;(4)the combination of a positive potential vorticity anomaly and thelatent heat release is able to accelerate the frontogenesis significantly with the time needed to forman intense frontal zone reduced to less than 15 h.The results have significant theoreticalimportance in understanding the complex nature of frontal structure and frontogenesis,especiallyin understanding the dynamic structure of the subtropical frontal zone observed during earlysummer over East Asia.     

对袁立功同志文章的回答

首先需要说明,“距离积分式天气雷达数字视频积分处理器积分精度”一文解决的问题是:由McGill大学首创、南京大学等单位改进研制的高分辨距离积分式数字视频积分处理器(DVIP)的积分精度,和通用的低分辨率距离——方位积分式DVIP积分精度可用单一的数值表示的情况不同,它本质上随距离和方位变化,无法进行理论分     

抚顺煤田煤变质特征

抚顺煤田的煤变质表现为一种具有浅成、高温、作用时间较短的岩浆热变质作用的特征。在西露天矿坑内和龙凤矿井下见有十分发育的接触热变质带,接触热变质煤未形成良好的天然焦,而是形成“炭渣状煤”或“烧变煤”。煤变质带明显,在平面上和垂向上都有所反映。煤变质带的分布与后期侵入的辉绿岩的分布关系密切。     

地震预报专家系统(ESEP/PC)中的证据可信度确定与类框架知识表示

本文根据实际地震预报中分析异常证据可信度的过程,提出了确定异常证据可信度的模型。指出异常证据的可信度可根据两类不同的影响因子(全局因子与局部因子)由证据可信度组合公式确定。据此在地震预报专家系统ESEP/PC中提出了“类框架”知识表示法。文中通过实例对应用中的有关问题进行了分析与讨论。     

陕西省及汾渭地震带的发震概率

本文用韦布尔(Weibull)分布对陕西省及汾渭地震带的中强地震活动进行概率统计分析,得到所研究地区的中强地震平均复发周期和发震概率。通过陕西省及汾渭地震带的韦布尔概率模型可以获得任一预测时间内的发震概率。     

Coherent motions in windbreak flow

Experimental data on windbreak flows have been analysed, using several statistical methods. Our analysis demonstrates that coherent structures exist in the mixing region of a porous windbreak (50% porosity) flow, and are largely responsible for the momentum transport that re-accelerates the leeward flow. A comparison between windbreak flow and laboratory turbulent mixing layers suggests that the dominant structures in these two flows are similar. Some previous numerical and experimental results are interpreted in light of the coherent structures and the self-similar property in the mixing region of a windbreak flow.     

北京地区气温和降水百年变化规律的探讨

本文通过对北京地区１２０年气温和１５０年降水资料的分析发现:（１）年和季的平均气温变化有着明显的一致性，１９２０年是个转折点，前期偏低，后期偏高。（２）冬、夏季的极端最高气温近２０年来呈偏低趋势，而极端最低气温呈持续偏高趋势。（３）年、季极端气温差值距平１９７２年以前以正距平为主，１９７２年以后以负距平为主。５０年来差值持续变小。（４）北京与中国东部、北半球、全球平均气温在１９２０年以前趋势相同。１９２０年以后，北京和中国东部的趋势相同，而和北半球、全球有着明显的差别。（５）北京的年降水从５０年代至８０年     

Petrogenesis of the granite related to the Baishaziling Sn deposit,Dayishan ore field,Southern China

The Baishaziling greisen-type tin deposit is located in the Dayishan ore field, Nanling Range, Southern China. In this study, for the first time, we present both zircon and cassiterite UPb dating, whole-rock elements, zircon LuHf and apatite Nd isotopic compositions to better constrain the petrogenesis of granite and its genetic link with Sn mineralization. Zircon UPb ages of fine-grained granite and coarse-grained granite are 154 ± 1.8 Ma and 153 ± 2.1 Ma, respectively, which are consistent with the cassiterite UPb dating of 154 ± 5.4 Ma, implying genetic relationship between the Baishaziling granite and tin metallogenesis. The Baishaziling granites exhibit high SiO₂, K₂O + Na₂O, Zr + Nb + Ce + Y contents, low P₂O₅ and Sr contents, and high ratios of Ga/Al, ^TFeO/(^TFeO + MgO), implying A-type granite affinity with characteristics of high-K calc-alkaline and weakly peraluminous. The zircon ε_Hf(t) values and apatite ε_Nd(t) values of the granite vary from ?4.46 to ?1.81 and ?8.37 to ?7.10, with two-stage Hf and Nd model ages of 1.40 to 1.50 Ga and 1.52 to 1.64 Ga, indicating that they were generated by the partial melt of the Proterozoic basement with the involvement of mantle magma. In addition, formation of Dayishan granite was likely associated with an intraplate extensional setting caused by the subduction of the Palaeo-Pacific plate. The Baishaziling reduced granites have high stannum and boron contents, which are in favor of the tin mineralization.     

宁镇、茅山山脉微观构造变形及变形环境的探讨

宁镇,茅山山脉褶皱逆冲一推覆构造带的构造岩类型主要为碎裂岩系列,其次为糜棱岩系列。主要超微构造为位错构造。经计算,区内印支、燕山期古差应力值约为90~100MPa,应变速率为:3.1x10~(-14)≤(?)≤2.0x10~(-10)。构造变形环境为低温、高压、高应变速率环境,微观机制主要为位错滑移。