The Mesoproterozoic to early Neoproterozoic passive margin Lajeado Group and Apiaí Gabbro,Southeastern Brazil

The Lajeado Group in the Ribeira Belt,southeastern Brazil,corresponds to an open-sea carbonate platform,comprised of seven overlapping siliciclastic and carbonatic formations,intruded in its upper portion by the Apiai Gabbro.These rocks have a Neoproterozoic tectonometamorphic overprint related to arc magmatism and the Brasiliano collisional orogeny.Geochronological constraints are given by new UPb SHRIMP and LA-ICP-MS data for Lajeado Group detrital zircons and for magmatic zircons from the Apiai Gabbro.The youngest detrital zircons in the Lajeado Group are 1400-1200 Ma,and constrain its maximum age of deposition to be 1200 Ma,whereas the 877 ± 8 Ma age for magmatic zircons in the Apiai Gabbro give the minimum age.Detritus source areas are mainly Paleoproterozoic(2200-1800 Ma)with some Archean and Mesoproterozoic contribution(1500-1200 Ma),with distal or tectonic stable cratonic character.The Lajeado Group should be a Stenian-Tonian carbonate platform passive margin of a continent at this time,namely the Columbia/Nuna or the Rodinia.The Apiai Gabbro displays similar age to other intrusive basic rocks in the Lajeado and Itaiacoca groups and represents tholeiitic MORB-like magmatism that we relate to the initial break-up of a Mesoproterozoic continent and the formation of the Brasiliano oceans.     

航摄底片信息容量的确定

为了定量地分析航摄底片的信息容量,本文在影象数字化的基础上,从理论上分析信息容量的估算公式,监重点研究用\     

美国国家天气局地面观测自动化现状与展望

当前,一个限制或削减全部工作和费用的压力正漫延着整个美国联邦政府,国家天气局在八十年代期间必须对此有所准备。同时,又要尽可能地满足广大公众对预报准确率和提高天气服务方面提出的要求。国家天气局准备在以下几方面进行努力:1.国家气象中心计算机的更换和继续改进指导产品;2.改进国内通讯(AFOS)和传递;3.提高卫星、雷达(RADAP,多普勒)和地面观测水平;4.改组预报组织。现就地面观测自动化概述如下:目前,国家天气局(NWS)现有人员1,200人,260多个地面观测站提供地面天气观测资料。观测方法仍以人工操作为主。随着各种先进传感器的出     

Some experiments with multivariate objective analysis scheme of heights and winds using optimum interpolation

A two-dimensional, multitvariate objective analysis scheme for simultaneous analysis of geopotential height and wind fields has been developed over Indian and adjoining region for use in numerical weather prediction. The height-height correlations calculated using daily data of four July months (1976-1979), are used to derive the other autocorrelations and cross-correlations assuming geostropic relationship. A Gaussian function is used to model the autocorrelation function. Since the scheme is multivariate the regression coefficients (weights) are matrix.Near the equator, the geostrophic approximation relating mass and wind is decoupled in a way similar to Bergman (1979). The objective analyses were made over Indian and adjoining region for 850, 700, 500, 300 and 200 hPa levels for the period from 4 July to 8 July 1979, 12 GMT. The analyses obtained using multivariate optimum in-terpolation scheme depict the synoptic situations satisfactorily. The analyses were also compared with the FGGE ana-lyses (from ECMWF) and also with the station observations by computing the root mean square (RMS) errors and the RMS errors are comparable with those obtained in other similar studies.     

东北太平洋上暴发性发展生成的气旋

1.引言 Sanders和Gyakum(1980年)把24小时内中心气压至少减少24毫巴的温带气旋定义为气象炸弹。他们提到的加深率本来是对北纬60度而言的,为了得到任何纬度θ的     

全球增暖对甲烷生物圈源的影响及其气候后果

1.引言人们认为工业活动对全球气候的影响主要是二氧化碳的温室效应。近来,已经提出在北半球观测到的可能是由于人类活动产生的较高的臭氧浓度会造成气候增温0.2 K(Fishman等,1979)。而且,在气候-化学耦合     

Relationship between 500 hPa ridge axis positions over the indian and the west Pacific regions and the Indian summer monsoon rainfall

500 hPa ridge positions over the Indian and the West Pacific regions during April are related with the summer monsoon rainfall over India. The ridge position over the Indian region shows better relation with monsoon rainfall than that shown by the ridge over the Pacific region. The multiple correlation of these ridge positions with monsoon rainfall exceeds 0.7. These predictive relationships are better than those shown by other parameters, viz. (1) Northern Hemispheric surface temperature; (2) East-Pacific sea surface tempera-ture; (3) El-Nino events and (4) Tahiti-Darwin pressure difference, and index of southern oscillation, over the 30-year samples analysed.     

大气中痕量有机胺测量方法的研究进展

作为大气中最重要的含氮有机化合物,有机胺易与硫酸、硝酸气体生成胺盐,促进新颗粒的形成,同时也可与臭氧、OH自由基、NO₃自由基发生氧化反应,是二次气溶胶的前体物.综述了国内外关于大气有机胺检测技术的研究进展,对常规的离线检测技术和在线质谱技术进行了介绍和对比,重点介绍了质谱法工作原理以及测定大气有机胺的优越性,并对其未来发展进行了展望.