Observations and speculations on the northeast Towy ‘axis’, mid-Wales

Late Ashgill and Llandovery sedimentation across the Towy ‘axis’ southeast of Rhayader is interpreted within the context of the rapid southeasterly thickening of the upper portion of the Ashgill best demonstrable in the Chwefru valley. This thickening sequence overlies deep-water middle-fan arenites and is interpreted as a northwest prograding shelf/slope association. The slope eventually became non-depositional and was onlapped by the basinal facies of the Llandovery during relative sea-level rise. The non-depositional slope and associated major slump-scars at the shelf-edge explain many of the non-sequences- in the region previously ascribed to erosion related to episodes of tectonism. The regional strain history is thus simplified.     

Bifurcation of nonlinear Kelvin wave-CISK with conditional heating in a truncated spectral model: A possible mechanism of 30–60-day oscillation at the equator

In this paper, the nonlinear Kelvin wave equations with “positive-only” nonlinear (conditional) heating at the equator are reduced to a sixth-order nonlinear ordinary differential equation by using the Galerkin spectral truncated method. The stability analysis indicates that when the heating parameter increases, the supercritical pitchfork and Hopf bifurcations can occur for the prescribed three heating profiles. Numerical calculations are made with the help of the fourth-order Rung-Kutta method. It is found that the convec-tion heating-related Hopf bifurcation can lead to limit cycle and chaotic solutions. In a wide range of heat-ing parameter, the solutions possess 30-60-day periods, and are dominated by wavenumbers one and two, especially by wavenurnber-one. In addition, the zonal winds of the low-frequency solutions have a phase reversal between the upper and lower tropospheres. Thus, it appears that the convection heating-related Hopf bifurcation might be a possible mechanism of 30-60-day oscillation in the tropical atmosphere.     

全球变暖背景下的南极地区气候变化

南极地区气温冬季,春季和秋季都有上升趋势,而夏季则有下降趋势,年平均气温也趋上升,气温上升趋势最强烈的是冬季,其次是春季;降水各季和全年都有增加趋势。在年际尺度上,年均气温和降水与南极涛动指数是负相关,南极极涛动对不同区域影响的方向和程度也有区别。     

北半球夏季遥相关的年际振荡及其与ENSO循环的可能联系

利用４３年夏季５００ｈＰａ高度场资料刻划了北半球夏季东亚太平洋型遥相关和积雪强迫型遥相关的强度．分析结果揭示了它们准４年周期振荡间的位相关系,并推测了在该时间尺度上与ＥＮＳＯ循环的可能联系．     

水雾输送扩散的数值研究

本文利用边界层能量闭合模式,对金沙江上某地水电站泄洪产生的水雾的输送和扩散过程进行了模拟,分析了对下风方向湿度场的影响和水雾存在范围与主要气象条件的关系。模拟表明：水雾分布范围随水雾源强的增大而增大,并且随风速增加而增加,与背景相对湿度关系不大;相对湿度受影响的范围与背景相对湿度几乎无关,但与水雾的源强,风速有关;在较高背景相对湿度的河谷地带,影响水雾分布范围的最主要因素是水雾源强和风速。     

The EUV spectrum of sunspot plumes observed by SUMER on SOHO

We present results from sunspot observations obtained by SUMER on SOHO. In sunspot plumes the EUV spectrum differs from the quiet Sun; continua are observed with different slopes and intensities; emission lines from molecular hydrogen and many unidentified species indicate unique plasma conditions above sunspots. Sunspot plumes are sites of systematic downflow. We also discuss the properties of sunspot oscillations     

1994年中国华南大范围暴雨过程的形成与夏季风活动的研究

利用 1 994年夏季 ECMWF逐日两次的格点资料和日本的 TBB资料 ,结合这一年华南地区 6,7月的站点降水资料 ,诊断分析了 1 994年夏季风 (主要为南海季风 )活动、华南地区的两次特大暴雨过程以及两者之间的关系。结果发现 :这一年的夏季风十分活跃 ,南海夏季风与表征对流活动的 TBB低值带以低频振荡的形式 (周期约为 30～ 60 d)传播到暴雨区 ,与暴雨的发生有着密切的联系 ,强暴雨过程对应着季风的脉动或加强期 ;强劲的季风气流向暴雨区输送水汽 ,其中以南海地区的水汽输送为主 ;两次暴雨过程发生在不同的环流形势下 ,但是都位于较大的水汽辐合和对流不稳定区。     

低轨道磁化等离子体中运动航天器等离子体鞘层特性

用二维静电粒子模拟程序研究了在低轨道磁化等离子体中航天器充电过程和等离子体鞘层结构．采用磁化等离子体流经航天器的物理模型,并且考虑零级对流电场的影响．结果表明航天器在低轨道空间飞行时,如果不考虑光电子流,航天器会在短时间内(ｔ＝５４ω_ｐｅ^－１,ω_ｐｅ是电子等离子体频率)快速充电到平衡电位。在不考虑航天器运动的情况下其周围等离子体鞘层结构是围绕航天器对称的,等离子体鞘层宽度约２．４个德拜（Ｄｅｂｙｅ）长度．当考虑航天器运动时,航天器的平衡负电位绝对值减小．且在背离航天器运动方向上等离子体鞘层宽度为８．３个德拜长度．磁场的增大使负的平衡电位绝对值变小,当航天器运动从平行于磁场方向转向垂直于磁场方向时,航天器负平衡电位的绝对值减小．     

二阶线性差分方程新的振动与非振动准则

讨论二阶线性差分方程 Δ2 xn-1 pnxn=0解的振动与非振动性 ,其中 :pn≥ 0。结论是 :若存在自然数 n0 ,当 pn 在数集 { lmn0 ,lmn0 1,…… ,lm 1n0 - 1}上的有限和满足某种条件时 l、m∈ N,则可对方程的解的振动与非振动性作出判断。