石花形恐龙幻迹：中国重庆綦江区下白垩统夹关组的罕见遗迹化石

在中国重庆綦江区虎山足迹点发现了2个大型恐龙天然足模化石,化石赋存于砂质富集的夹关组的一悬崖底面。它们属于罕见的幻迹,同类足迹也发现于韩国和北美白垩系足迹点。放射状、同心及半脆性形变使这些幻迹具有切断状或网状外观,有时呈现出类似裂断花或菜花的形态。这正是当地“石头开花”民间传说的来源。这些特征表明,造迹者必然是恐龙,同时也清晰地展现了其外形态学特征。     

切分法固定断面测量

改变航迹线和交会定位公式进行水上固定断面测量,更新了传统水上固定断面复测定位法,新法具有不偏线、点位密、计算简便、精度高等优点,能为生产、设计、研究提供相对精确的地理模型。     

Sinuosity of tropical cyclone tracks in the South West Indian Ocean: Spatio-temporal patterns and relationships with fundamental storm attributes

The shapes of 268 tropical cyclone tracks in the South West Indian Ocean (SWIO) basin are investigated over the period 1977 to 2011 using an established metric for track sinuosity. Original cyclone position data from the RSMC La Réunion area of responsibility were accessed from the IBTrACS archive maintained by NOAA. Cyclone track sinuosity was measured within a GIS environment and the filtered results were normalised with a cube-root transformation function to reduce positive skew in the output sinuosity distribution. Several key findings from spatial and temporal analysis of sinuosity results may be highlighted. To assess geographical patterns, mapping tracks within designated quartile categories (straight, quasi-straight, curving and sinuous tracks) indicates which land areas in the SWIO are more likely to be affected by cyclones following sinuous tracks that are more difficult to forecast, in particular Madagascar and the islands of Réunion and Mauritius. Over the past three decades, the temporal sinuosity pattern shows a high degree of variability that will probably continue into the future. Yet crucially, a number of conspicuous episodes of relatively magnified or subdued sinuosity are recognised compared to long-term averages. This may present opportunities for identifying major climatic controls on regional anomalous cyclone migration behaviour. Within the average yearly cyclone season, the early months (September–December) have a tendency to produce more predictable straighter-moving cyclones, whereas January stands out as the singular month marking an abrupt swing towards a greater proportion (64%) of curving and sinuously-moving storms. This finding is of importance for vulnerability assessment, because a strong positive correlation is also identified between track sinuosity and cyclone longevity, such that storms steering less predictable sinuous courses are also those that tend to survive for longer durations.     

Sensitivity of Cyclone Tracks to the Initial Moisture Distribution： A Moist Potential Vorticity Perspective

In this study, the characteristics of moist potential vorticity （MPV） in the vicinity of a surface cyclone center and their physical processes axe investigated. A prognostic equation of surface absolute vorticity is then used to examine the relationship between the cyclone tracks and negative MPV （NMPV） using numerical simulations of the life cycle of an extratropical cyclone. It is shown that the MPV approach developed herein, i.e., by tracing the peak NMPV, can be used to help trace surface cyclones during their development and mature stages. Sensitivity experiments are conducted to investigate the impact of different initial moisture fields on the effectiveness of the MPV approach. It is found that the lifetime of NMPV depends mainly on the initial moisture field, the magnitude of condensational heating, and the advection of NMPV. When NMPV moves into a saturated environment at or near a cyclone center, it can trace better the evolution of the surface cyclone due to the conservative property of MPV. It is also shown that the NMPV generation is closely associated with the coupling of large potential temperature and moisture gradients as a result of frontogenesis processes. Analyses indicate that condensation, confluence and tilting play important but different roles in determining the NMPV generation. NMPV is generated mainly through the changes in the strength of baroclinicity and in the direction of the moisture gradient due to moist and/or dry air mass intrusion into the baroclinic zone.     

Convective radiation fluid‐dynamics: formation and early evolution of ultra low‐mass objects

The formation process of ultra low‐mass objects is some kind of extension of the star formation process. The physical changes towards lower mass are discussed by investigating the collapse of cloud cores that are modelled as Bonnor‐Ebert spheres. Their collapse is followed by solving the equations of fluid dynamics with radiation and a model of time‐dependent convection that has been calibrated to the Sun. For a sequence of cloud‐cores with 1 to 0.01 solar masses, evolutionary tracks and isochrones are shown in the mass‐radius diagram, the Hertzsprung‐Russel diagram and the effective temperaturesurface gravity or Kiel diagram. The collapse and the early hydrostatic evolution to ages of few Ma are briefly discussed and compared to observations of objects in Upper Scorpius and the low‐mass components of GG Tau. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)