Simulation of equatorial and high-latitude jets on Jupiter in a deep convection model

The bands of Jupiter represent a global system of powerful winds. Broad eastward equatorial jets are flanked by smaller-scale, higher-latitude jets flowing in alternating directions. Jupiter's large thermal emission suggests that the winds are powered from within, but the zonal flow depth is limited by increasing density and electrical conductivity in the molecular hydrogen-helium atmosphere towards the centre of the planet. Two types of planetary flow models have been explored: shallow-layer models reproduce multiple high-latitude jets, but not the equatorial flow system, and deep convection models only reproduce an eastward equatorial jet with two flanking neighbours. Here we present a numerical model of three-dimensional rotating convection in a relatively thin spherical shell that generates both types of jets. The simulated flow is turbulent and quasi-two-dimensional and, as observed for the jovian jets, simulated jet widths follow Rhines' scaling theory. Our findings imply that Jupiter's latitudinal transition in jet width corresponds to a separation between the bottom-bounded flow structures in higher latitudes and the deep equatorial flows.     

湾流及其邻近海域中尺度涡统计特征分析

为了得到中尺度涡的特征,综合利用1993-2012年共20a的卫星高度计资料及Argo浮标资料等,对湾流及其邻近海域的中尺度涡特征进行统计,并采用合成方法对涡的三维结构特征进行分析。结果表明:该海域气旋涡(CE)和反气旋涡(AE)的平均生命史及平均半径十分相近;湾流主体段与延续段的涡动能(EKE)、涡能量密度(EI)和涡度明显大于其他区域,气旋涡平均强度大于反气旋涡;对于生命周期内的长周期涡,半径和EKE的变化幅度较大,EI和涡度的变化较小;涡以西向移动为主,平均移速3.2cm/s;长周期气旋涡和反气旋涡均具有向赤道移动的特征;在垂直剖面上,气旋涡(反气旋涡)存在2个温度负(正)异常结构和上下2个盐度负(正)异常结构,涡对海水温盐的垂向影响可达1km以上。     

室内空气流动过程的模型实验研究

为了分析在不同的进风位置、射流方向以及进风温度条件下,房间壁温对室内空气流动的影响,在缩小模型实验的基础上,利用流动可视化和定量测量相结合的办法测量了不同工况下室内的空气流动形态、速度以及模型整体换热情况。结果表明:壁温恒定时,进风温度的降低引起水平进风方式的自由射流区缩短;垂直进风方式下射流形成的涡的中心位置向壁面靠近;中间垂直进风方式下射流向左侧偏转;右侧垂直进风方式下射流向右侧壁面偏转;同时浮升力引起的自然对流作用增强,换热温差加大,提高了围护结构漏热量。     

Mid-depth recirculation observed in the interior Labrador and Irminger seas by direct velocity measurements

The Labrador Sea is one of the sites where convection exports surface water to the deep ocean in winter as part of the thermohaline circulation. Labrador Sea water is characteristically cold and fresh, and it can be traced at intermediate depths (500-2,000 m) across the North Atlantic Ocean, to the south and to the east of the Labrador Sea. Widespread observations of the ocean currents that lead to this distribution of Labrador Sea water have, however, been difficult and therefore scarce. We have used more than 200 subsurface floats to measure directly basin-wide horizontal velocities at various depths in the Labrador and Irminger seas. We observe unanticipated recirculations of the mid-depth (approximately 700 m) cyclonic boundary currents in both basins, leading to an anticyclonic flow in the interior of the Labrador basin. About 40% of the floats from the region of deep convection left the basin within one year and were rapidly transported in the anticyclonic flow to the Irminger basin, and also eastwards into the subpolar gyre. Surprisingly, the float tracks did not clearly depict the deep western boundary current, which is the expected main pathway of Labrador Sea water in the thermohaline circulation. Rather, the flow along the boundary near Flemish Cap is dominated by eddies that transport water offshore. Our detailed observations of the velocity structure with a high data coverage suggest that we may have to revise our picture of the formation and spreading of Labrador Sea water, and future studies with similar instrumentation will allow new insights on the intermediate depth ocean circulation.     

Pumping of nutrients to ocean surface waters by the action of propagating planetary waves

Primary productivity in the oceans is limited by the lack of nutrients in surface waters. These nutrients are mostly supplied from nutrient-rich subsurface waters through upwelling and vertical mixing, but in the ocean gyres these mechanisms do not fully account for the observed productivity. Recently, the upward pumping of nutrients, through the action of eddies, has been shown to account for the remainder of the primary productivity; however, these were regional studies which focused on mesoscale (100-km-scale) eddies. Here we analyse remotely sensed chlorophyll and sea-surface-height data collected over two years and show that 1,000-km-scale planetary waves, which propagate in a westward direction in the oceans, are associated with about 5 to 20% of the observed variability in chlorophyll concentration (after low-frequency and large-scale variations are removed from the data). Enhanced primary production is the likely explanation for this observation, and if that is the case, propagating disturbances introduce nutrients to surface waters on a global scale--similar to the nutrient pumping that occurs within distinct eddies.     

Interannual atmospheric variability forced by the deep equatorial Atlantic Ocean

Climate variability in the tropical Atlantic Ocean is determined by large-scale ocean-atmosphere interactions, which particularly affect deep atmospheric convection over the ocean and surrounding continents. Apart from influences from the Pacific El Ni?o/Southern Oscillation and the North Atlantic Oscillation, the tropical Atlantic variability is thought to be dominated by two distinct ocean-atmosphere coupled modes of variability that are characterized by meridional and zonal sea-surface-temperature gradients and are mainly active on decadal and interannual timescales, respectively. Here we report evidence that the intrinsic ocean dynamics of the deep equatorial Atlantic can also affect sea surface temperature, wind and rainfall in the tropical Atlantic region and constitutes a 4.5-yr climate cycle. Specifically, vertically alternating deep zonal jets of short vertical wavelength with a period of about 4.5?yr and amplitudes of more than 10?cm?s(-1) are observed, in the deep Atlantic, to propagate their energy upwards, towards the surface. They are linked, at the sea surface, to equatorial zonal current anomalies and eastern Atlantic temperature anomalies that have amplitudes of about 6?cm?s(-1) and 0.4?°C, respectively, and are associated with distinct wind and rainfall patterns. Although deep jets are also observed in the Pacific and Indian oceans, only the Atlantic deep jets seem to oscillate on interannual timescales. Our knowledge of the persistence and regularity of these jets is limited by the availability of high-quality data. Despite this caveat, the oscillatory behaviour can still be used to improve predictions of sea surface temperature in the tropical Atlantic. Deep-jet generation and upward energy transmission through the Equatorial Undercurrent warrant further theoretical study.     

辨别胶子喷注和夸克喷注的能量法则研究

用蒙特卡洛方法研究了e^ e湮灭产生的3-喷注事件,将强子3-喷注按能量排序并通过与部分子层次的3-喷注配对来辨别胶子喷注和夸克喷注．分析了能量法则挑选喷注的纯度;用改进后的能量法则计算了3-喷注事件中的三个喷注的平均多重数,平均横动量随喷注能量的分布以及胶子喷注和夸克喷注的平均多重数之比和平均横动量之比．并与角度法则的相应结果进行了比较．结果显示用改进后的能量法则挑选喷注的方法是可行的．     

Dynamical impact of anomalous East-Asian winter monsoon on zonal wind over the equatorial western Pacific

Abstract Zonal wind anomaly over the equatorial western Pacific plays an important role in the occurrence of ENSO. The mechanism to produce zonal wind anomaly over the equatorial western Pacific is studied in this paper. It is shown clearly that zonal wind anomaly over the equatorial western Pacific is closely related to the anomaly of EastAsian winter monsoon. Anomalous strong （weak） East-Asian winter monsoon can excite not only the westerly （easterly）anomaly over the equatorial western Pacific but also a cyclonic （an anticyclonic） circulation over the east of the Philippines. The above anomalous circulation results from dynamical impacts of anomalous pressure pattern due to the East-Asian winter monsoon. Because there is westward （eastward） pressure gradient over the equatorial western Pacific, i.e. there is αp/αx 〈 0 （〉 0）, during strong （weak） East-Asian winter monsoon.     

频散效应对自由大气能量输送的影响

本文应用扩大的Ｐｒａｎｄｔｌ混合长理论分析自由大气中的Ｒｅｎｏｌｄｓ平均运动方程组，着重分析了频散效应对自由大气大迟度运动能量输送的影响。分析指出：频散效应的自由大气中能量由扰动动能向平均动能转换（即能量逆转）的根本原因；正压大气能量逆转只能在扰动的尺度小于临界迟度Ｌｃ时才能发生；斜压大气能量逆转主要在扰动的厚度小于临界厚度Ｄｃ时发生。不同尺度的扰动与包含和不包含频率散效应的简单模式结果验证了上面     

Circulation in the South China Sea in summer of 1998

Based on the CTD and meteorological data obtained by R/VXiangyanghong No. 14 in the South China Sea (SCS) in the summer of 1998, both current velocity and volume transport are calculated by using a modified inverse model. Circulation in the SCS is analyzed by combining the calculated results with ADCP data. The following results are obtained, (i) The most important feature of the circulation in the northeastern SCS is that a branch of the Kuroshio intrudes into the SCS with a small volume transport. It flows anticyclonically through the Bashi Strait and towards the southwest off the Taiwan Island, and it does not intrude into the inner SCS. (ii) The northern SCS is dominated mainly by a cyclonic circulation system with two cold eddies, (iii) The central and southwestern SCSs are mainly occupied by anticyclonic circulation systems, including three anticyclonic and one stronger cyclonic eddies. (iv) In the southeastern SCS, there is a large scope of cyclonic circulation extending in the SW-NE direction, (v) There is a “multi-eddy phenomenon” in the SCS, and a larger eddy contains several small eddies. (vi) There is western intensifying of the currents and eddies in the SCS.     

与低空急流相伴的暴雨天气诊断分析

 对1998年5月～2002年5月7例与低空急流相伴的云南全省性暴雨过程进行了合成诊断分析.结果表明:临近暴雨发生时,西南低空急流的形成应是云南暴雨产生的主要原因,暴雨天气通常出现在低空急流北侧风矢呈气旋性弯曲、风速递减的梯度十分明显的区域内;低空急流对于水汽和能量的输送起非常重要的作用,它一方面为暴雨的产生提供了所需要的大量水汽,另一方面又使得暴雨区低层大气增湿增暖,从而引起对流不稳定加强,为暴雨的发生提供大量的不稳定能量.湿位涡分析表明,暴雨发生前,冷暖空气在云南交汇,使大气温湿结构发生变化,θ_e等值面坡度加大,当低空急流移向对流不稳定区时,便有气旋性涡度剧烈发展,导致暴雨天气的发生.     

Extended magnetic reconnection at the Earth's magnetopause from detection of bi-directional jets

Magnetic reconnection is a process that converts magnetic energy into bi-directional plasma jets; it is believed to be the dominant process by which solar-wind energy enters the Earth's magnetosphere. This energy is subsequently dissipated by magnetic storms and aurorae. Previous single-spacecraft observations revealed only single jets at the magnetopause--while the existence of a counter-streaming jet was implicitly assumed, no experimental confirmation was available. Here we report in situ two-spacecraft observations of bi-directional jets at the magnetopause, finding evidence for a stable and extended reconnection line; the latter implies substantial entry of the solar wind into the magnetosphere. We conclude that reconnection is determined by large-scale interactions between the solar wind and the magnetosphere, rather than by local conditions at the magnetopause.     

基于共生理论的东西部和谐发展研究

东部和西部的共生关系主要表现为:资源是共生单元,合作是共生模式,互补关系是共生环境.东西部和谐发展需要坚持3B和3E原则,文章据此提出了相应的对策.     

Lag influences of winter circulation conditions in the tropical western Pacific on South Asian summer monsoon

<正>By means of monthly mean NCEP/NCAR data analyses, this note investigates the lag influences of winter circulation conditions in the tropical western Pacific on South Asian summer monsoon through the methods of composite, correlation and statistical confident test. The results indicate clearly that winter climate variations in the equatorial western Pacific would produce significant influences on the following South Asian summer monsoon, and with the lapse of time the lag influences show clearly moving northward and extending westward features. When winter positive (negative) sea level pressure anomalies occupy the equatorial western Pacific, there is an anticyclonic (cyclonic) circulation anomaly appearing in the northwestern Pacific. With the lapse of time, the anticyclonic (cyclonic) circulation anomaly gradually moves to northeast, and its axis in the west-east directions also stretches, therefore, easterly (westerly) anomalies in the south part of the anticyclonic (cyclonic) circulation anomaly continuously expand westward to the peninsula of India. Undoubtedly, the South Asian summer monsoon is weak (strong).     

粤西沿岸流和物质输移模型研究及应用

本文通过建立FVCOM三维数值模型模拟广东沿岸海流,分析了粤西沿岸海流特征,研究结果表明,粤西沿岸海流主要为西南向流,只有在夏季西南季风较大时才会有东北向流。在海流模拟基础上建立物质输移扩散模型,模拟粤西沿岸的物质输移状况,模型结果显示,粤西沿岸的物质扩散以西向为主,只有夏季季风较大时物质才向东扩散,且扩散速度较小,琼州海峡的物质扩散终年向西。     

大气湿对流的类型和深厚湿对流触发机制综述

梳理大气湿对流和强对流天气的定义和特征,综述深厚湿对流(DMC)的触发机制研究进展。类似贝纳德对流的大气浅薄湿对流积云的组织形态取决于边界层大气垂直风切变强度。按照触发高度,可将DMC划分为地基对流和高架对流;按照强弱程度,也可以将DMC划分为强雷暴和普通雷暴。虽然强对流天气的定义具有一定的主观性,不同国家的定义标准存在差异,但都具有极端性和易致灾等特点。然而,全面监测这些天气的类型和强度的难题依然存在。地基对流的触发机制实际上位于边界层,最为复杂多样;很多DMC的触发是辐合线相互作用或不同机制共同作用的结果。未来需要加强边界层的精细探测能力,深入研究DMC触发机制的气候学特征和机理,更需要提升高时空分辨率资料同化水平和边界层过程的数值模拟能力。     

太平洋地区地球主磁场长期变化特征的研究

研究太平洋地区主磁场的长期变化特征,对揭示该地区的“偶极子窗”的时间演变和长期变化规律有重要意义.作者使用最新的国际地磁参考场IGRF13模型资料,分析1900—2020年期间太平洋地区主磁场的长期变化特征.结果表明1900—2020年太平洋地区主磁场的空间展布符合“太平洋偶极子窗”的分布特征.该地区主磁场的长期变化在赤道以北为缓慢变化,以南则是较快变化.偶极子场成分变化缓慢,非偶极子场成分变化较快.非偶极子场的长期变化以西向漂移为主,但各分量的西漂速率有显著的差异.垂直分量（Z）和北向分量（X）的西漂速率分别为0.23°/a和0.21°/a,均接近于0.2°/a的全球非偶极子西漂速率;东向分量（Y）的西漂速率为0.17°/a,低于全球非偶极子西漂速率. Y分量的长期变化在34°N附近发生扭曲并且在北太平洋表现为缓慢东漂,这一长期变化特征可能与太平洋北部的30°N和45°N之间在核幔边界处存在的古板块的俯冲过程有关.     

Lightning in Saturn’s atmosphere

There exists large-scale lightning in Saturn’s water cloud. Based on the powerful moist convection in the water cloud, we establish a thermal-induced convective model to interpret the mechanism for the processes of charge generation and separation. We also estimate the breakdown field of Saturn’s atmosphere quantitatively and interpret the discharge process.     

共轭传热室内自然对流数值模拟研究

研究建筑围护结构传热与流体流动综合作用下室内自然对流数值模拟，建立了一套同时在固体一流体区域整体求解连续性方程、动量方程和能量方程的数值模拟方法。具体分析了瑞利数变化范围为10^4到10^6时建筑围护结构传热对室内自然对流的影响。数值预测结果表明：该方法能够真实反映室内自然对流问题。为室内自然对流问题数值模拟提供了一种实用有效的方法。