天山地区夏季极端降水特征及气候变化

基于1961—2007年天山地区32站的逐日降水资料,分析了夏季天山地区极端降水事件的气候分布和时间变化特征.结果表明:夏季天山地区的极端降水量、极端降水日和极端降水比分布存在明显的区域差异.局地极端降水频繁,平均3～4d就有1次发生,大范围极端降水较少发生.连续性极端降水以1d为主.极端降水量在天山南北坡均随地形增加而增多,地形高度对降水的影响,北坡要大于南坡.在相同高度范围内,北坡极端降水量基本均大于南坡.天山地区的极端降水事件呈增多趋势,在1970年代中后期至1980年代中前期,极端降水事件为低值期,而1990年代是高值期.     

The temporal variation of the spherical and Cartesian multipoles of the gravity field: the generalized MacCullagh representation

 The Cartesian moments of the mass density of a gravitating body and the spherical harmonic coefficients of its gravitational field are related in a peculiar way. In particular, the products of inertia can be expressed by the spherical harmonic coefficients of the gravitational potential as was derived by MacCullagh for a rigid body. Here the MacCullagh formulae are extended to a deformable body which is restricted to radial symmetry in order to apply the Love–Shida hypothesis. The mass conservation law allows a representation of the incremental mass density by the respective excitation function. A representation of an arbitrary Cartesian monome is always possible by sums of solid spherical harmonics multiplied by powers of the radius. Introducing these representations into the definition of the Cartesian moments, an extension of the MacCullagh formulae is obtained. In particular, for excitation functions with a vanishing harmonic coefficient of degree zero, the (diagonal) incremental moments of inertia also can be represented by the excitation coefficients. Four types of excitation functions are considered, namely: (1) tidal excitation; (2) loading potential; (3) centrifugal potential; and (4) transverse surface stress. One application of the results could be model computation of the length-of-day variations and polar motion, which depend on the moments of inertia. Received: 27 July 1999 / Accepted: 24 May 2000     

Present-day climatology and projected changes of warm and cold days in the CNRM-CM3 global climate model

The impact of global warming on the warmest and coldest days of the annual cycle is explored according to an A2 scenario simulated by the CNRM-CM3 climate model in the framework of the IPCC AR4 intercomparison. Given the multi-model spread in IPCC projections, a validation strategy is proposed using the NCEP/NCAR reanalysis. Validation of the late twentieth century model climatology shows that warm and cold model events are slightly too long and infrequent. Although interannual trends in the warm (cold) day occurrence were positive (negative) only for six (three) of the nine considered sub-continental regions, simulated model trends are always positive (negative). This different behaviour suggests that simulated non-anthropogenic decadal variability is small relative to anthropogenic trends. Large-scale synoptic processes associated with European regional warm and cold peaks are also described and validated. Regional cold peaks are better reproduced than warm peaks, whose intensity accuracy is limited by other physical variables. Positive (negative) winter anomalies of sea and land surface temperature lead to summers with severe (weak) temperatures. These inter-annual anomalies are generated by a persistent pressure dipole over Europe. Regarding climate change, warm (cold) events will become more (less) frequent and longer (shorter). The number of warm days will largely rise and the number of cold days will dramatically decrease. The intensity of warm days will be particularly pronounced over Europe, given the projected summer drying in this region. However, according to the limited skill of the CNRM model, these results must be considered with caution.     

德国在线和江苏MOS的评估分析及应用

江苏省分县逐日滚动MOS预报和德国天气在线是预报员经常参考的预报工具,本文对2003年3月到7月的资料用常规的统计方法和TS评分对这两种方法进行分析评估,利用得到的一些结论,在2004年汛期中使用,产生了较好的预报效果。     

理解前兆异常变化机理和地震短临前兆

本文概要介绍了国内外近几年在地壳形变一地球自转日长变化十年尺度相关性、静寂地震、前驱波三方面的重要研究发现,并分析了这三项研究发现在地震前兆异常机理认识中的作用。初步分析表明：深部核幔耦合作用引起的地壳形变、地球物理场十年尺度波动,是数年至十年尺度地震场兆波动性变化的重要调制因素之一;源于断层脆韧转换带(过渡层)的静寂地震一慢地震缓慢破裂过程,是数天至数月尺度地震短期异常变化产生的重要原因;源于脆韧转换层上部或弹脆性层薄弱部分慢地震过程所辐射出来的低频前驱波(慢地震波),是目前已发现的可重复出现的短临前兆信号,具有数小时至7天左右的地震短临预报指标意义。     

中国数字地震台网（CDSN）数据文件系统：—CDSN应用系列论文一

中国数字地震台网(CDSN)观测并生成的数字地震资料是开展数字地震学研究必不可少的高质量数据源。为了使科学家们更好地使用这些数据,本文主要从数字地震资料产生出的各个环节、数据结构与格式、数据物理量之间的换算向读者作概括的介绍.希望读者对数字化地震资料的数据文件、数据记录、数据字均能有透彻的理解,从而节省时间和精力,提高资料的使用率。     

Cretaceous length of day perturbation by mantle avalanche

These last 10 years, numerical models of mantle convection have emphasized the role of the 670 km endothermic phase change in generating avalanches that trigger catastrophic mass transfers between upper and lower mantle. On the other hand, scientists have emphasized the concomitance of large-scale worldwide geophysical and tectonic events, which could find their deep thermal roots in the huge mass transfers induced by the avalanches. In particular, the paleontological records show two periods of length of day (l.o.d.) shortening between 420 and 360, and 200 and 80 Myr BP. This last event is synchronous with a strong true polar wander and a global warming of the upper mantle. In order to study the potential effects of the avalanche on the main component of the Earth’s rotation, the Liouville equation has been solved and the l.o.d. evolution has been calculated from the perturbations of the inertia tensor. The results show that the inertia tensor of the Earth’s is mainly sensitive to the global transfers through the 670 km discontinuity. The l.o.d. perturbations will be synchronous with the global thermal effects of the avalanche. These theoretical results allow proposing a self-consistent physical mechanism to explain periods of the Earth’s rotation acceleration. Within this context, the l.o.d. shortening during the Cenozoic and Cretaceous brings one more clue to the possible participation of a mantle avalanche in generating the concomitant large scale events which have occurred during this very particular period of the Earth’s history.     

天线罩疏水层老化对微波辐射计观测的影响分析

地基微波辐射计因天线罩疏水层老化,在雨天探测时天线罩上易形成积水从而造成探测性能的不稳定,是影响其在科研业务中广泛应用的关键问题之一。本研究利用2017—2018年北京地区6台微波辐射计降雨期间的观测数据,分析天线罩疏水层老化对其观测亮温的影响,结果显示随着天线罩使用时间的增长,尤其是使用3个月以后,降水时亮温增大的幅度明显变大,降水结束后亮温增大的持续时间也有增长趋势。同时,在北京南郊站开展的微波辐射计天线罩淋雨试验结果表明,天线罩使用40 d以后,随着天线罩污染老化,淋雨时观测亮温增大的幅度呈跳跃式增长,且淋雨结束后亮温仍然偏高,最长时间达2 h以上。因此,为提高微波辐射计观测数据的可用性,建议在实际使用过程中每季度更换一次天线罩,对于京津冀等重污染地区可根据实际情况适当提高更换频次。