北极地区不同冰龄的海冰厚度变化研究

In this study, changes in Arctic sea ice thickness for each ice age category were examined based on satellite observations and modelled results. Interannual changes obtained from Ice, Cloud, and Land Elevation Satellite(ICESat)-based results show a thickness reduction over perennial sea ice(ice that survives at least one melt season with an age of no less than 2 year) up to approximately 0.5–1.0 m and 0.6–0.8 m(depending on ice age) during the investigated winter and autumn ICESat periods, respectively. Pan-Arctic Ice Ocean Modeling and Assimilation System(PIOMAS)-based results provide a view of a continued thickness reduction over the past four decades. Compared to 1980 s, there is a clear thickness drop of roughly 0.50 m in 2010 s for perennial ice. This overall decrease in sea ice thickness can be in part attributed to the amplified warming climate in north latitudes. Besides, we figure out that strongly anomalous southerly summer surface winds may play an important role in prompting the thickness decline in perennial ice zone through transporting heat deposited in open water(primarily via albedo feedback) in Eurasian sector deep into a broader sea ice regime in central Arctic Ocean. This heat source is responsible for enhanced ice bottom melting, leading to further reduction in ice thickness.     

我国西北降水变化趋势和预估

利用观测资料、GPCC再分析资料和第六次耦合模式比较计划（CMIP6）模拟结果,研究了我国西北地区近几十年及未来降水变化趋势。结果表明,1979—2019年我国西北干旱半干旱区降水在全年各季节均有显著增加,其中秋季增加最多。CMIP6模拟结果显示,随着全球变暖,我国西北地区降水在2015—2100年将继续增加。至21世纪末,在SSP2-4.5和SSP5-8.5情景下,我国西北地区年平均降水量将分别增加约13.7%（37 mm）和25.8%（78 mm),其中降水量增加最多的季节分别为夏季和春季。考虑到西北地区蒸发量也将随全球变暖而增加,模式平均的结果显示西北地区年平均净降水量在两种情景下的增幅分别约1.4%和4.9%,表明我国西北地区未来气候呈现显著的变湿趋势。进一步分析表明,西北地区未来降水增加可能与局地大气低层位势高度降低和上升运动加强有关。     

Parallels plane projection and its geometric features

A new equivalent map projection called the parallels plane projection is proposed in this paper. The transverse axis of the parallels plane projection is the expansion of the equator and its vertical axis equals half the length of the central meridian. On the parallels plane projection, meridians are projected as sine curves and parallels are a series of straight, parallel lines. No distortion of length occurs along the central meridian or on any parallels of this projection. Angular distortion and the proportion of length along meridians (except the central meridian) introduced by the projection transformation increase with increasing longitude and latitude. A potential application of the parallels plane projection is that it can provide an efficient projection transformation for global discrete grid systems.     

基于投影寻踪原理的动态聚类模型及其在气候区划中的应用

以投影寻踪原理为基础, 结合动态聚类方法, 建立了基于投影寻踪原理的动态聚类模型, 并首次将其应用于气候区划分析中。首先, 利用线性投影技术将多因素聚类问题转换为投影特征值的线性聚类问题; 其次, 利用动态聚类方法完成投影特征值序列的聚类分析; 最后, 通过气候区划实例验证了基于投影寻踪原理的动态聚类模型的可行性与有效性。     

适用于H.264的高性能快速运动估计算法

提出了一种适用于H .2 6 4的快速运动估计方法 :使用一维映射作为块排除准则 ,并充分利用H .2 6 4中的运动估计模式间的匹配冗余 ,使得 7种运动估计模式并行执行。试验结果表明 ,在估计精度几乎无损的情况下 ,本文算法比传统的全局搜索速度快 6倍以上     

地球极表象为直线的再投影法

对于地球极表象为直线的投影，本文运用对偶变换和广义轴位变换，得出了它们的几种新款式。     

投影寻踪自回归和多维混合回归模型及其在大河长河段洪水预报中的应用

投影寻踪自回归和多维混合回归模型，是将投影寻踪技术应用于时间序列分析中的一种新型的非线性时序分析模型。本文将此模型用于长江寸滩－宜昌河段的洪水演算，不必使用区间雨量资料，仅仅根据上下游站的流量资料，就可做出预见期为４８－７２ｈ的复杂长河段洪水预报，并取得了令人满意的的研究成果。     

特大型精密工程SSC测量投影方式的选择

目前世界上最大的工程超导超级对撞机(SSC)正在建造之中,作者参与这项大型精密工程测量的方案设计和部分咨询工作。根据工程的特点,设计测量投影方式是其中一项工作。本文讨论所设计的双重正形投影(stereographic double conformal projection)以及各种观测量投影归化中的问题。