地磁静日期内北半球电离层NmF2的结构分布

用北半球陆地上48个地面电离层垂测站资料，以及国际参考电离层IRI 90模式，考察1985年1月6～7日F2层电子密度最大值日变化的纬度剖面和经度效应. 结果表明，在亚洲地区的20°N～30°N内，F2层赤道异常“喷泉效应”产生的NmF2“北驼峰”最高，其最大值出现在中午，或稍迟时间. 30°N ～50°N区域内，NmF2的白天峰值幅度逐渐下降，峰值时间移至午前约10:00 LT. 更高纬度(50°N～62°N )台站上，中午前后NmF2出现双峰，傍晚有谷值，夜间又再次抬升. 欧、美地区的低纬台站很少，但借助IRI 90模式分析可发现，在270°E经圈上，“喷泉效应”造成的“北驼峰”幅度最小，而且随纬度增大时，NmF2白天幅度下降也不明显，即纬度剖面的经度效应非常显著. 对中国、日本地区台站资料的小范围经度差异分析表明，在驼峰区的90°E～140°E内，各站NmF2无明显差别；但在中纬地区30°N～50°N内，中国西部上空NmF2白天变化幅度较大，且较为陡直，而中国东部和日本台站上空则相对平缓.     

Short-term residence and movement patterns of the annular seabream Diplodus annularis in a temperate marine reserve

The short-term movements of a small temperate fish, the annular seabream Diplodus annularis (Linnaeus 1758), were examined using standard tag-recapture and passive acoustic telemetry in Palma Bay (NW Mediterranean), a marine protected area (MPA). The study aimed to provide valuable information for assessing the recreational fishery and its results suggest that MPAs can be used to protect the adult stock of D. annularis. All the fish tagged with standard tags were recaptured near the release locations, with a maximum distance of ∼300 m. The maximum time between release and recapture was 185 d. Two different arrays of acoustic receivers were deployed, one in 2008 and another in 2009, within the MPA. Twenty adults were surgically tagged with acoustic transmitters. Fish monitored in 2008 (n = 12) were translocated from the point of capture to analyse the movement behaviour after artificial displacement. Upon release at displaced locations, 67% of the fish moved towards the original capture location using a time of return that ranged from 0.75 to 15.25 h. Fish monitored in 2009 (n = 8) were released at the point of capture. They showed high site fidelity with a maximum period of 27 d between the first time and the last time they were detected.     

磁偏角和热层风对中纬电离层TEC经度分布的影响

本文利用北美、南美和大洋洲三个地区的电离层TEC数据,分析了磁偏角为零的经度线两侧中纬电离层TEC的差异.结果表明,在2001年至2010年的几乎所有季节,在磁偏角为零的经度东西两侧,北美、南美和大洋洲中纬电离层TEC都存在规则性的差异;中纬电离层TEC的这种经度差异显著地依赖地方时,对季节和太阳活动水平也有不同程度的依赖.地磁场影响下电离层与热层动力学耦合的分析表明,磁偏角的经度变化和热层风的地方时变化两者的共同作用是引起磁偏角为零的经度两侧中纬电离层TEC差异的重要原因之一.     

Fast spherical collocation: theory and examples

 It has long been known that a spherical harmonic analysis of gridded (and noisy) data on a sphere (with uniform error for a fixed latitude) gives rise to simple systems of equations. This idea has been generalized for the method of least-squares collocation, when using an isotropic covariance function or reproducing kernel. The data only need to be at the same altitude and of the same kind for each latitude. This permits, for example, the combination of gravity data at the surface of the Earth and data at satellite altitude, when the orbit is circular. Suppose that data are associated with the points of a grid with N values in latitude and M values in longitude. The latitudes do not need to be spaced uniformly. Also suppose that it is required to determine the spherical harmonic coefficients to a maximal degree and order K. Then the method will require that we solve K systems of equations each having a symmetric positive definite matrix of only N × N. Results of simulation studies using the method are described. Received: 18 October 2001 / Accepted: 4 October 2002 Correspondence to: F. Sansò     

日面新生黑子的经度分布

以云南天文台对５２２个太阳自转周的观测资料统计,在可见日面上新生的黑子,各个太阳活动周出现频数不等。从中筛选出面积ＣＹ≥５００的２２８群,以及ＣＹ≥１２００的２９群,它们分别都在经度上呈相对集中性,但又多随时间变化而漂移,在时间分布上无规律性。在可比的太阳第２１和２２活动周内,新生黑子对应的最强烈活动区只有８１２００和９２３９０,另外是８２４９５回转的８２５３３对应在最强烈活区,说明新生大黑子无固定的活动源。     

The summer maximum in total ozone over northwest Europe

Station records of ozone observations have been critically reviewed to investigate the reality of the reported maximum in total ozone over northwest Europe in July. The existence of a longitudinal excess of ozone over the British Isles is confirmed but strong horizontal gradients can be verified only over central Europe and there is no evidence for east-west gradients over the Atlantic. Ozone sounding data as well as total ozone daily variability make it most plausible that the ozone excess over northwest Europe is confined to the lower stratosphere. The isopleths in the region of strong ozone gradients are parallel to the mean flow at 100 mb as required by the calculated constraint on the magnitude of the mean flow advection. It is proposed that analyses of the ozone distribution over oceanic areas could be improved by extending ozone isopleths parallel to the mean lower stratospheric flow from land areas where the pattern is better defined.     

早二叠世塔里木陆块的经度：来自大火成岩省的制约

经度的确定是板块重建的难点. 塔里木盆地下二叠统大规模溢流玄武岩已被确定为大火成岩省, 提供了一次根据大火成岩省来定量确定塔里木陆块早二叠世经度的机遇. 核幔边界约2800 km深处地震波低速带与全球300 Ma以来喷发的大火成岩省之间的关系已得到建立: 恢复喷发位置后, 大火成岩省全部分布在核幔边界低速带的边缘之上, 其中大部分在非洲LLSVP和太平洋LLSVP边缘, 个别在规模较小的LSVPs边缘. 在使用塔里木陆块早二叠世古地磁数据来限定其纬度的基础上, 本文利用上述理论方法, 并联系前人的地质结论, 发现塔里木大火成岩省约290 Ma喷发时的位置最可能为20°N, 60°E. 本文提出, 塔里木大火成岩省与西伯利亚大火成岩省相似, 其喷发时并不在两大LLSVPs的边缘带上, 而最可能与非洲LLSVP东侧附近一个单独的、范围较小的LSVP(20°N, 60°E)相关联, 暗示重建之前的假设"塔里木大火成岩省源自核幔边界"是合理的. 如果塔里木、峨眉山和西伯利亚大火成岩省都源自核幔边界, 上述(20°N, 60°E)位置的获得说明三者都不是同一幔源.     

极区Hall电流经度差异特征的统计学研究:CHAMP卫星观测

本文利用2001至2010年间CHAMP(CHallenging Minisatellite Payload)卫星标量磁力仪(Overhauser Magnetometer)观测的磁场数据,反演得到电离层霍尔(Hall)电流,并且对极区电离层Hall电流的特征进行了统计学研究.研究主要关注平静期,即重联电场小于2 mV·m~(-1)条件下,在磁纬60°至90°范围内的Hall电流在不同太阳活动、季节、磁经度、磁地方时等条件下的变化特征.研究发现:Hall电流具有明显的经度差异,在南北半球呈现显著一波经度结构,而且南北半球反相,即北半球电流密度呈现峰-谷-峰结构,而南半球呈现谷-峰-谷结构.Hall电流密度的经度结构与太阳活动紧密相关,太阳活动高年经度差异最大,太阳活动中年经度差异次之,太阳活动低年经度差异最小.研究发现,在磁地方时为10-14MLT的白天,影响Hall电流的因素主要是太阳辐射;而磁地方时为21-03MLT的夜晚,除了电导率的影响之外,可能存在其他的重要的物理过程影响着Hall电流的经度分布.本文还研究了与电流相关的焦耳热的经度分布情况,发现其在南北半球分别呈现单峰、单谷结构,经度差异亦十分明显.     

高空西风急流东西向形态变化对梅雨期降水空间分布的影响

利用40年的NCEP/NCAR再分析候平均资料和同期长江中下游地区逐日降水资料,使用合成方法分析了梅雨期东亚副热带高空西风急流的东西位置和形态变化特征,探讨了高空西风急流对梅雨期降水空间分布的影响.分析结果表明,梅雨期东亚大陆上空西风急流强度减弱且持续维持、西太平洋上空西风急流核分裂减弱直至出梅后消失,这是梅雨期200 hPa东亚高空西风急流东西向位置变化的主要特征.梅雨期,200 hPa副热带西风急流中心呈现东西向位置变化和海陆分布形态差异,西风急流中心东西向位置变化对梅雨起讫有着较好的指示意义.梅雨期东亚副热带高空西风急流东西形态分布差异不仅影响到长江中下游地区降水空间集中区的位置而且还影响到降水中心强度.进一步分析表明,当东亚西风急流主体位于西太平洋上空时,在长江下游地区形成高低空急流耦合的环流形势,强烈的辐合上升运动加上充足的水汽条件供应,有利于在长江下游形成集中的强降水区域.当高空西风急流位于东亚大陆上空时,在长江中下游地区高低空急流无耦合形势存在,长江中下游地区也没有强的集中降水区域.因此,东亚副热带高空西风急流东西向形态变化对长江中下游地区的高低空环流结构、地面集中降水区域的空间分布具有重要的影响.     

Bathymetry of Lake Lisan controls late Pleistocene and Holocene stream incision in response to base level fall

This paper examines the millennial-scale evolution of the longitude profile of Nahal (Wadi) Zin in the Dead Sea basin in the northern Arava valley, Israel. Nahal Zin has incised ~ 50 m into relatively soft late Pleistocene Lake Lisan sediments. Incision was forced by the regressive (> 10 km) lake level fall of a total of > 200 m of Lake Lisan from its highest stand at ~ 25 ka and exposure of the lake-floor sediments to fluvial and coastal processes. Alluvial cut terraces of the incising channel are well preserved along the 17.5 km of the lowermost reach of Nahal Zin. At its outlet into the Dead Sea basin, Nahal Zin deposited a Holocene alluvial fan at the base of a 10–80 m high escarpment in unconsolidated sediments. The escarpment is associated with the Amazyahu fault, which forms the southern structural boundary of the present Dead Sea basin. Geomorphic mapping, optically stimulated luminescence (OSL) ages, and soil stratigraphy allowed correlation of terrace remnants and reconstruction of several past longitudinal profiles of Nahal Zin and its incision history. Together with the published lake level chronology, these data provide an opportunity to examine stream incision related to base level lowering at a millennial scale. OSL ages of the terraces fit relatively well with the established lake level chronology and follow its regression and fall. For a few thousands of years the longitudinal profile response to the lake level fall was downstream lengthening onto the exposed former lake bed. Most of the incision (~ 40 m) occurred later, when the lake level reached the top of the Amazyahu fault escarpment and continued to drop. The incision was a relatively short episode at about 17 ka and cut through this escarpment almost to its base. The fast incision, its timing, and the profiles of the incising channels indicate that the escarpment was an underwater feature and was not formed after the lake retreated.This fairly simple scenario of regressive lake level fall and knickpoint exposure and incision is modeled here using a one-dimensional numerical incision model based on a linear diffusion equation. The calculated diffusion coefficient fits earlier results and data obtained from other streams in the area and confirms the upscaling of this simple model to the millennial scale.