On the relationship of SAPS to storm-enhanced density     

《Journal of Atmospheric and Solar》2007,69(3):303-313

We use magnetic field-aligned mapping between the ionosphere and the magnetosphere to intercompare ground-based observations of storm enhanced density (SED), and plasmasphere drainage plumes imaged from space by the IMAGE EUV imager, with the enhanced inner-magnetosphere/ionosphere SAPS electric field which develops during large storms. We find that the inner edge of the SAPS electric field overlaps the erosion plume and that plume material is carried sunward in the SAPS overlap region. The two phenomena, SED in the ionosphere and the erosion plume at magnetospheric heights, define a common trajectory for sunward-propagating cold plasma fluxes in the midnight—dusk–postnoon sector. The SAPS channel at ionospheric heights and its projection into the equatorial plane serve to define the sharp outer boundary of the erosion plume. The SAPS electric field abuts and overlaps both the plasmasphere boundary layer and the plasmasphere erosion plume from pre-midnight through post-noon local times.  相似文献   

应用FY-1D气象卫星监测雾   总被引：4，自引：0，他引：4  

梁益同  张家国  刘可群  黄靖 《气象》2007,33(10):68-72

简要介绍了FY-1D气象卫星的特点。利用典型的FY-1D资料,通过直方图分析法,探讨了雾在FY-1D不同通道的光谱特征。分析结果表明,可见光通道1和红外通道4是FY-1D卫星监测雾的代表通道。通道1图像上,雾的反照率在20%～48%之间,且纹理均匀,顶部光滑,边缘清晰,而通道4图像上,雾的亮温在272～289K之间,与地表温差不超过6K。  相似文献   

Diagnosing the spatiotemporal diversity of westerly wind events in the tropical Pacific     

《Dynamics of Atmospheres and Oceans》2019

Westerly Wind Events (WWEs) over the tropical Pacific are characterized by their spatiotemporal diversity and classified into six types based on their different locations and durations. Various types of WWEs exhibit quite different characteristics in terms of their amplitudes. The long events with a 10–30-day duration are stronger than the short events with a 6–10-day duration, and the maximum amplitudes of the Central-Pacific (C) type and Eastern-Pacific (E) type of long events are larger than the Western-Pacific (W) type of long ones. The evolutions of these six types of WWEs are also quite different. The W-type short and long events and the C-type long events show a distinct eastward propagation, whereas the C-type short events and the E-type short and long events have no apparent propagation direction. We demonstrate that such a difference in the eastward propagation of WWEs can be significantly associated with the Madden-Julian Oscillation (MJO). The W-type events are more influenced heavily by the MJO, as indicated by their more distinct eastward propagation patterns, than the two other types of WWEs. In addition to the MJO, the convectively coupled Kelvin waves are also associated with the WWEs, especially for the short events.  相似文献   

基于地基微波辐射计对武汉夏季暴雨过程的观测分析     

韩芳蓉  舒斯  郭英莲  许建玉 《沙漠与绿洲气象(新疆气象)》2017,11(6):83-88

利用地基微波辐射计获取的高时空分辨率资料,结合卫星云图资料,对2012年7月12—13日武汉站发生的暴雨过程中各气象要素与降水的关系进行了分析。结果表明:(1)相对湿度、液态水含量、不稳定能量的值和其大值区所在的垂直高度在降水期均明显大于非降水期,说明这些要素变化特征与降水有较好的对应关系,应用地基微波辐射计资料要素分析降水过程具有很高的可靠性。(2)以小时雨量10 mm将降水分界为弱降水和强降水时段。云底高度在强降水时段才为零;温度的垂直分布在降水时段存在逆温,且强降水比弱降水时段逆温层更高;水汽密度在有降水发生时,底层的大值区有所抬升,并在强降水时段对流层低层出现26 g/m3的大值中心。可以通过地基微波辐射计对降水做进一步的量级划分,有助于明确雨团性质和降水效率。  相似文献   

Measuring visual enclosure for street walkability: Using machine learning algorithms and Google Street View imagery     

《Applied geography (Sevenoaks, England)》2016

One major limitation currently with studying street level urban design qualities for walkability is the often inconsistent and unreliable measures of streetscape features across different field surveyors even with costly training due to lack of more objective processes, which also make large scale study difficult. The recent advances in sensor technologies and digitization have produced a wealth of data to help research activities by facilitating improved measurements and conducting large scale analysis. This paper explores the potential of big data and big data analytics in the light of current approaches to measuring streetscape features. By applying machine learning algorithms on Google Street View imagery, we generated objectively three measures on visual enclosure. The results showed that sky areas were identified fairly well for the calculation of proportion of sky. The three visual enclosure measures were found to be correlated with pedestrian volume and Walk Score. This method allows large scale and consistent objective measures of visual enclosure that can be done reproducibly and universally applicable with readily available Google Street View imagery in many countries around the world to help test their association with walking behaviors.  相似文献   

Petrogenesis and tectonic evolution of Lianyunshan complex,South China: Insights on Neoproterozoic and late Mesozoic tectonic evolution of the central Jiangnan Orogen     

《Gondwana Research》2016

The Yangtze and Cathaysia blocks in South China are separated by the ca. 1500 km long Jiangnan Orogen. The Lianyunshan complex, located in the central segment of Jiangnan Orogen, includes wide exposures of late Mesozoic granites. Here we report geological, geochronological and geochemical data from the Lianyunshan late Mesozoic granites and their Neoproterozoic host rocks belonging to the Lengjiaxi Group. Detrital zircon U–Pb ages reveal a single prominent peak at ca. 840 Ma in the metamorphosed and deformed Lengjiaxi Group samples. Ten of the youngest zircon grains in these rocks have a weighted mean age of 828.8 ± 7.1 Ma, which is tentatively interpreted as the maximum depositional age of the Lengjiaxi Group. Two stages of late Mesozoic S-type granites are dated at ca. 150 Ma and ca. 140 Ma from the Lianyunshan domain. From early to late, these rocks show decreasing MgO, CaO, Fe₂O₃^T, TiO₂ contents and increasing SiO₂, K₂O, Eu/Eu*, Rb/Sr ratios and differentiation index, suggesting continuous magmatic evolution dominated by fractional crystallization. The εHf(t) values of zircons with late Mesozoic ages are all negative, with their two-stage model ages mainly ranging from 1.9 to 1.4 Ga, which is significantly different from the model age of the host rocks belonging to the Lengjiaxi Group. These results indicate that the late Mesozoic granites were mainly derived from the partial melting of Paleo-Mesoproterozoic basement rocks that are older than Lengjiaxi Group. Major and trace element features suggest that the protoliths of these early stage granites in Lianyunshan are probably mixed greywacke and shale. The arc-like trace elements signature of all the late Mesozoic granites were possibly inherited through crustal contamination during the magma genesis caused by slab rollback associated with Paleo-Pacific subduction during 150- to 140 Ma beneath the central Jiangnan belt.  相似文献   

全球地表(海表)前期温度与中国及华中地区夏季降水的关联   总被引：2，自引：1，他引：1  

张礼平  丁一汇 《气象学报》2005,63(3):325-332

用SVD方法分析了1月全球地表(海表)温度与中国及华中区域夏季降水场的关系,分析结果表明:1月热带地区地表(海表)温度与夏季长江中游降水关系最好,呈正相关。与新疆西北部、青海东北部、长江上游有弱的正相关,与山东大部分地区、浙江沿海地区有弱的负相关。前期热带海洋海表温度偏高,可能预示长江中游夏季降水偏多,反之亦然。由于分析的范围为全球的陆面和海面,因而其关联范围较已有成果有很大的扩展,不仅仅为热带西太平洋、印度洋和南海,而是整个热带地区,包括热带的海洋和陆地。预报信号也提前了4个月,可为预测长江中游夏季降水提供更长时效的参考和依据。  相似文献   

The Tancheng-Lujiang Wrench fault system: edited by Xu Jiaway. Wiley, 1993, 279 p., US $175.00 (ISBN 0-471-93332-5)     

《Geochimica et cosmochimica acta》1994,58(8):1965

  相似文献   

Preliminary analysis on the source properties and seismogenic structure of the 2017 <Emphasis Type="Italic">M</Emphasis><Subscript>s</Subscript>7.0 Jiuzhaigou earthquake     

Zujun Xie  Yong Zheng  Huajian Yao  Lihua Fang  Yong Zhang  Chengli Liu  Maomao Wang  Bin Shan  Huiping Zhang  Junjie Ren  Lingyun Ji  Meiqin Song 《中国科学:地球科学(英文版)》2018,61(3):339-352

At GMT time 13:19, August 8, 2017, an M_s7.0 earthquake struck the Jiuzhaigou region in Sichuan Province, China, causing severe damages and casualties. To investigate the source properties, seismogenic structures, and seismic hazards, we systematically analyzed the tectonic environment, crustal velocity structure in the source region, source parameters and rupture process, Coulomb failure stress changes, and 3-D features of the rupture plane of the Jiuzhaigou earthquake. Our results indicate the following: (1) The Jiuzhaigou earthquake occurred on an unmarked fault belonging to the transition zone of the east Kunlun fault system and is located northwest of the Huya fault. (2) Both the mainshock and aftershock rupture zones are located in a region where crustal seismic velocity changes dramatically. Southeast to the source region, shear wave velocity at the middle to lower crust is significantly low, but it rapidly increases northeastward and lies close to the background velocity across the rupture fault. (3) The aftershock zone is narrow and distributes along the northwest-southeast trend, and most aftershocks occur within a depth range of 5–20 km. (4) The focal mechanism of the Jiuzhaigou earthquake indicates a left-lateral strike-slip fault, with strike, dip, and rake angles of 152°, 74° and 8°, respectively. The hypocenter depth measures 20 km, whereas the centroid depth is about 6 km. The co-seismic rupture mainly concentrates at depths of 3–13 km, with a moment magnitude (M_w) of 6.5. (5) The co-seismic rupture also strengthens the Coulomb failure stress at the two ends of the rupture fault and the east segment of the Tazang fault. Aftershocks relocation results together with geological surveys indicate that the causative fault is a near vertical fault with notable spatial variations: dip angle varies within 66°–89° from northwest to southeast and the average dip angle measures ~84°. The results of this work are of fundamental importance for further studies on the source characteristics, tectonic environment, and seismic hazard evaluation of the Jiuzhaigou earthquake.  相似文献   

Meridional movement of northern and southern equatorial ionization anomaly crests in the East-Asian sector during 2002–2003 SSW     

XiaoHua Mo  DongHe Zhang  Larisa Goncharenko  ShunRong Zhang  YongQiang Hao  Zuo Xiao  JiaZheng Pei  Akimasa Yoshikawa  HaDuyen Chau 《中国科学:地球科学(英文版)》2017,60(4):776-785

The present paper investigates the asymmetrical variability of the location of the north and the south equatorial ionization anomaly (EIA) crests in the East-Asian sector, along with their association with simultaneous observations of equatorial electrojet (EEJ) strength, geomagnetic activity index, and solar flux index during the 2002–2003 sudden stratospheric warming (SSW) event. Analysis of these observations indicates the existence of a large-scale quasi 16-day periodic meridional movement in both EIA crests, and also reveals a strong correlation between the quasi 16-day oscillation in geomagnetic latitudes of the EIA crest and EEJ strength. The latitude of the northern/southern EIA crest and the EEJ strength indicate that obvious synchronous periodic oscillations were in-phase in the northern and southern hemisphere when the SSW occurred. In addition, it is also found that both the EIA crest location and amplitude of the periodic movement of the EIA locations exhibit hemispheric asymmetry. The amplitude of the periodic movement of the EIA location in the southern hemisphere is larger than that of the northern hemisphere, and the southern EIA crest is further off from the equator than the north one. Understanding these asymmetries requires a combination of mechanisms that involve at least trans-equator meridional winds and the position of a sub-solar point; however, potential disturbances in neutral winds associated with the SSW may additionally complicate the equatorial ionospheric dynamics.  相似文献