2004年12月26日苏门答腊—安达曼地震激发的地球自由振荡

根据300~500S的面波估计得到的哈佛大学矩心矩张量断层机制,当周期大于1000S时,地球的地震自由振荡的振幅将异常地大。我们对一个比较陡的断层应用根据地震的体波和面波得到的更真实的破裂模型,估计了自由振荡的振幅近似等于地震矩(6.5×1022N.M),这相当于矩震级为9.15。由于破裂的持续时间达600S,故断层破裂模型足以描述地震的观测结果,但却低估了大地测量位移,这些位移表明在尼科巴群岛和安达曼群岛下面发生了缓慢的断层运动。     

In the other 90%: phytoplankton responses to enhanced nutrient availability in the Great Barrier Reef Lagoon

Our view of how water quality effects ecosystems of the Great Barrier Reef (GBR) is largely framed by observed or expected responses of large benthic organisms (corals, algae, seagrasses) to enhanced levels of dissolved nutrients, sediments and other pollutants in reef waters. In the case of nutrients, however, benthic organisms and communities are largely responding to materials which have cycled through and been transformed by pelagic communities dominated by micro-algae (phytoplankton), protozoa, flagellates and bacteria. Because GBR waters are characterised by high ambient light intensities and water temperatures, inputs of nutrients from both internal and external sources are rapidly taken up and converted to organic matter in inter-reefal waters. Phytoplankton growth, pelagic grazing and remineralisation rates are very rapid. Dominant phytoplankton species in GBR waters have in situ growth rates which range from approximately 1 to several doublings per day. To a first approximation, phytoplankton communities and their constituent nutrient content turn over on a daily basis. Relative abundances of dissolved nutrient species strongly indicate N limitation of new biomass formation. Direct ((15)N) and indirect ((14)C) estimates of N demand by phytoplankton indicate dissolved inorganic N pools have turnover times on the order of hours to days. Turnover times for inorganic phosphorus in the water column range from hours to weeks. Because of the rapid assimilation of nutrients by plankton communities, biological responses in benthic communities to changed water quality are more likely driven (at several ecological levels) by organic matter derived from pelagic primary production than by dissolved nutrient stocks alone.     

The spatial focus of U.S. interstate migration flows

"Despite the widespread interest in the changing geographies of national migration regimes, it is somewhat remarkable that no widely accepted measure of the spatial concentration or focus exhibited by such geographies has emerged. We examine four of the most popular indices of inequality in this paper and contrast their performance as measures of spatial focus. Adopting the coefficient of variation as our preferred alternative, we go on to examine the spatial focus of aggregate interstate migration steams in the U.S. over time. Then we consider disaggregations of the migration streams by age, race and nativity, and examine the role of states as national redistributors of these same subpopulations."     

降水系统的概念模式

雷达和卫星图象的解释是临近预报的主要内容之一。在做提前几小时的降水详细预报时,需要借助于天气尺度、中尺度现象和它们的机制对图象进行仔细的解释。本文综述了一些概念模式,这些模式描绘了热带和中纬地区的中纬度气旋、中尺度对流系统的各种表现。特别讨论了下述现象: (ⅰ)暖输送带,包括在上滑和下滑冷锋形势中具有后倾上升和前倾上升的输送带;(ⅱ)暖锋前的冷输送带;(ⅲ)出现在冷锋前低空急流边界层的与线对流相联系的窄雨带;(ⅳ)与对流层中层对流有关的中尺度宽雨带;(ⅴ)热带和中纬度飑线;(ⅵ)热带和中纬度非飑线中尺度对流系统;(ⅶ)与冷旋涡相联的次天气尺度逗点云;(ⅷ)极槽输送带和即刻锢囚(instant occlusion)。     

THE GATE SQUALL LINE OF 9－10 AUGUST 1974

A tropical squall line that passed over the ship array of the Global Atmospheric Research Programme’s Atlantic Tropical Experiment (GATE) on 9－10 August 1974 is analyzed. This squall line was similar to squall systems that passed over the GATE ship array on four other days. It began as a purely convective cloud line, then developed an associated stratiform cloud and precipitation area. The stratiform rain built up to a maxi-mum amount over a period of 8 h, then gradually diminished over a 6 h period. This stratiform rain is esti-mated to have accounted for 32% of the squall system’s total precipitation. As in other GATE squall lines, the upper-level cloud shield from which the stratiform rain fell, was advected slowly forward of the line during the system’s lifetime, the leading line of corrective clouds consisted of transient smaller-scale convective elements, which lent the line an irregular shape and pulsatory movement, and the stratiform portion of the system was characterized by the development of a mid-level mesoscale vortex similar to that seen in other GATE eases.     

正压大气中根据天气和同化资料制作统计-动力预报

1.前言从一些离散的观测站采样而得某一气象变量的主观分析多半会和它的真实情况不同。如果这种不确定的分析用作数值预报的初始状态,那么所作预报也将会有误差。格利森1961年发展的一种统计-动力理论对这种初始状态的误差及其随时间增长作了定量处理。在这种理论模式中用调整物理模式的动力项将初始误差的正态分布转为预报误差的正态分布。从最终的分布求得预报量处于其真实数值的某一允许偏差范围内的理论概率。实际上这样也就作出了对预报     

Tibetan immigrants in India

"This paper documents the current evidence of the state of the Tibetan society in India with special reference to the trends in social transformation, livelihood patterns and cultural adaptation to a geographically alien environment....Three-and-a-half decades of living in India [have] demonstrated how a culture group can survive by carving out ecological niches in ethnically segregated social space and yet adapt to a new cultural environment without losing its identity."     

有关森林天然火灾的低层风和温度廓线

1.引言对负责森林火险天气预报人员来说,查看一下简单的气象图表,并确定气象条件是否有利于星星之火发展到不可控制的大火那将是非常必要的。由于近地面天气状况是受制于高层天气过程的,而火灾又是一种三度空间现象,与大气的铅直剖面关系密切。风和温度随高度变化影响大气对流的强弱,也影响林火的发生和发展。近年来,人们一直在探讨这些因素对森林天然火灾的影响。 1954年,拜厄姆(Byram)提出了在“点燃”林火的上空是某些特殊的风廓线。其要点之一是在火场的上空,风力由近地面的最大值一直到大约2400米附近的高度,而后随高度递减。他认为这样有利于火场上空对流柱的发展,由此能增强在地面火势的强度。