On the Use of CloudSat and MODIS Data for Estimating Hurricane Intensity

This letter presents preliminary results concerning the use of new observations from the A-Train Constellation for testing a new technique of remotely sensing hurricane intensity from space based on modeling a hurricane as a balanced, convectively neutral vortex. The key observational requirements are simultaneous, accurate measurements of cloud-top height, cloudtop temperature, and cloud profiling information across the center of the storm, although there are ways to bypass the need for cloud-top temperature. In this letter, the Moderate Resolution Imaging Spectroradiometer onboard Aqua provides an estimation of the cloud-top temperature, and the near-simultaneous CloudSat observations provide the essential cloud-top height and cloud profiling information. Initial results indicate that the new technique is a promising method for estimating storm intensity when compared post facto to the best track database. Potential uncertainties and room for further refinement of the technique are discussed.     

Evidence for inherited Sm−Nd isotopes in granitoid zircons

This study presents evidence to show that, in addition to preserving U–Pb isotope systematics, refractory zircons also preserve, at least in part, an inherited Sm–Nd isotope component. The zircons analyzed during this study were taken from the Strontian granitoid (NW Scotland). The inner intrusion of this composite pluton is known from a previous study to contain substantial U–Pb zircon inheritance, whereas the outer part has only minor inheritance. Zircons from the inner intrusion were found to have significantly lower Nd₄₂₅ values than either their host rock, separated apatite or monazite. It is argued that this isotopic disequilibrium is due to the presence of an inherited Sm–Nd isotope component, rather than being due to a post-crystallization disturbance of the zircons. The preservation of inherted Sm–Nd isotopes within refractory zircons implies that they remain closed systems with respect to the diffusion of Sm and Nd (and presumably the other REE) to temperatures in excess of 700°C. The fact that zircons commonly have high Sm/Nd ratios, relative to sialic crustal material, means that the Nd isotopic evolution of inherited zircons will be very different to that of much of the continental crust.     

The isotopic and chemical evolution of Mount St. Helens

Isotopic and major and trace element analysis of nine samples of eruptive products spanning the history of the Mt. St. Helens volcano suggest three different episodes; (1) 40,000–2500 years ago: eruptions of dacite with ε_Nd = +5, ε_Sr = ?10, variable δ¹⁸O,²⁰⁶Pb/²⁰⁴Pb ～ 18.76, Ca/Sr ～ 60, Rb/Ba ～ 0.1, La/Yb ～ 18, (2) 2500-1000 years ago: eruptions of basalt, andesite and dacite with ε_Nd = +4 to +8, ε_Sr = ?7 to ?22, variable δ¹⁸O (thought to represent melting of differing mantle-crust reservoirs), ²⁰⁶Pb/²⁰⁴Pb= 18.81?18.87, variable Ca/Sr, Rb/Ba, La/Yb and high Zr, (3) 1000 years ago to present day: eruptions of andesite and dacite with ε_Nd = +6, ε_Sr = ?13, δ¹⁸O～6‰, variable²⁰⁶Pb/²⁰⁴Pb, Ca/Sr ～ 77, Rb/Ba= 0.1, La/Yb ～ 11. None of the products exhibit Eu anomalies and all are LREE enriched. There is a strong correlation between⁸⁷Sr/⁸⁶Sr and differentiation indices. These data are interpreted in terms of a mantle heat source melting young crust bearing zircon and garnet, but not feldspar, followed by intrusion of this crustal reservoir by mantle-derived magma which caused further crustal melting and contaminated the crustal magma system with mafic components. Since 1000 years ago all the eruptions have been from the same reservoir which has displayed a much more gradual re-equilibration of Pb isotopic compositions than other components suggesting that Pb is being transported via a fluid phase. The Nd and Sr isotopic compositions lie along the mantle array and suggest that the mantle underneath Mt. St. Helens is not as depleted as MORB sources. There is no indication of seawater involvement in the source region.     

Modern stable isotopic (δ18O, δ2H, δ13C) variation in terrestrial,fluvial, estuarine and marine waters from north‐central Sarawak,Malaysian Borneo

Stable isotope data on humid tropical hydrology are scarce and, at present, no such data exist for Borneo. Delta¹⁸O, δ²H and δ¹³C were analysed on 22 water samples from different parts of the Sungai (river) Niah basin (rain, cave drip, rainforest pool, tributary stream, river, estuary, sea) in north‐central Sarawak, Malaysian Borneo. This was done to improve understanding of the modern stable isotope systematics of the Sungai Niah basin, essential for the palaeoenvironmental interpretation of the Late Quaternary stable isotope proxies preserved in the Great Cave of Niah. The Niah hydrology data are put into a regional context using the meteoric water line for Southeast Asia, as derived from International Atomic Energy Agency/World Meteorological Organization isotopes in precipitation network data. Although the Niah hydrological data‐set is relatively small, spatial isotopic variability was found for the different subenvironments of the Sungai Niah basin. A progressive enrichment occurs towards the South China Sea (δ¹⁸O ?4·6‰; δ²H ?29·3‰; δ¹³C ?4·8‰) from the tributary stream (δ¹⁸O ?8·4‰; δ²H ?54·7‰; δ¹³C ?14·5‰) to up‐river (δ¹⁸O c. ?8‰; δ²H c. ?51‰; δ¹³C c. ?12‰) and down‐river values (δ¹⁸O c. ?7·5‰; δ²H c. ?45‰; δ¹³C c. ?11‰). This is thought to reflect differential evaporation and mixing of different components of the water cycle and a combination of depleted biogenic δ¹³C (plant respiration and decay) with enriched δ¹³C values (due to photosynthesis, atmospheric exchange, mixing with limestone and marine waters) downstream. Cave drip waters are relatively enriched in δ¹³C as compared to the surface waters. This may indicate rapid degassing of the cave drips as they enter the cave atmosphere. Copyright © 2005 John Wiley & Sons, Ltd.     

赣南地区石雷石英闪长岩的成因:岩石化学、副矿物微量元素、锆石U-Pb年代学与Sr-Nd-Hf同位素制约

石雷石英闪长岩是赣南崇-余-犹地区比较特殊的闪长质侵入体。锆石的原位U-Pb定年表明,该岩体侵位于433.5±3.4Ma。全岩主量元素特征上显示出中偏酸性(SiO2=56.92%～64.70%),富Al(Al2O3=14.10%～14.83%),富碱(Alk=6.41%～7.40%)特别是富钾(K2O=3.86%～4.85%),镁、铁含量较高,MgO:3.47%～5.95%,FeOT:5.23%～8.14%以及低磷(P2O5=0.27%～0.4%)的特点;微量元素上主要富集K、Rb、Cs等大离子亲石元素和轻稀土元素,亏损Nb、Ta、Ti、P等高场强元素。磷灰石微量元素特征上显示高度富集稀土元素特别是轻稀土元素的特征;具有Eu的负异常(δEu=0.37～0.45)。ISr位于0.7073～0.7132之间,εNd(t)变化于-8.41～-4.97之间,两阶段钕模式年龄介于1.58～1.86Ga之间,Hf同位素组成相对均一,εHf(t)主要集中变化于-8～-2之间,两阶段Hf模式年龄加权平均为1.77±0.09Ga,这些特征都暗示了该石英闪长质岩体的形成是强烈壳幔相互作用的产物,区内加里东晚期可能发生了局部的岩石圈的减薄。     

Longitudinal dispersion processes in the upper tamar estuary

Measurements of velocity, salinity, and suspended solids concentration have been used to investigate the intra-tidal variation of vertical and transverse shear-induced dispersion. For the study research the interaction of the longitudinal density gradient and vertical shear during the early part of the ebb tide accounted for much of the net longitudinal dispersion of solute landward. The same mechanism also is shown to lead to a net particulate transport landward. The landward flux, however, takes place during the flood tide. The field data are also used to elucidate the tidally averaged tidal pumping mechanism.     

Sensitivity of a hydraulic model to channel erosion uncertainty during extreme flooding

Recent research into flood modelling has primarily concentrated on the simulation of inundation flow without considering the influences of channel morphology. River channels are often represented by a simplified geometry that is implicitly assumed to remain unchanged during flood simulations. However, field evidence demonstrates that significant morphological changes can occur during floods to mobilize the boundary sediments. Despite this, the effect of channel morphology on model results has been largely unexplored. To address this issue, the impact of channel cross‐section geometry and channel long‐profile variability on flood dynamics is examined using an ensemble of a 1D–2D hydraulic model (LISFLOOD‐FP) of the ~1 : 2000 year recurrence interval floods in Cockermouth, UK, within an uncertainty framework. A series of simulated scenarios of channel erosional changes were constructed on the basis of a simple velocity‐based model of critical entrainment. A Monte‐Carlo simulation framework was used to quantify the effects of this channel morphology together with variations in the channel and floodplain roughness coefficients, grain size characteristics and critical shear stress on measures of flood inundation. The results showed that the bed elevation modifications generated by the simplistic equations reflected an approximation of the observed patterns of spatial erosion that enveloped observed erosion depths. The effect of uncertainty on channel long‐profile variability only affected the local flood dynamics and did not significantly affect the friction sensitivity and flood inundation mapping. The results imply that hydraulic models generally do not need to account for within event morphodynamic changes of the type and magnitude of event modelled, as these have a negligible impact that is smaller than other uncertainties, e.g. boundary conditions. Instead, morphodynamic change needs to happen over a series of events to become large enough to change the hydrodynamics of floods in supply limited gravel‐bed rivers such as the one used in this research. Copyright © 2014 John Wiley & Sons, Ltd.     

A late glacial Antarctic climate teleconnection and variable Holocene seasonality at Lake Pupuke, Auckland, New Zealand

We present the first continuous paleolimnological reconstruction from the North Island of New Zealand (37°S) that spans the last 48.2?cal kyr. A tephra- and radiocarbon-based chronology was developed to infer the timing of marked paleolimnological changes in Lake Pupuke, Auckland, New Zealand, identified using sedimentology, magnetic susceptibility, grain size and geochemistry (carbon, nitrogen and sulphur concentrations and fluxes, carbon and nitrogen stable isotopes). Variable erosional influx, biomass and benthic REDOX conditions are linked to changing effective precipitation and seasonality within three inferred broad intervals of climatic change: (1) the Last Glacial Coldest Phase (LGCP) of reduced effective precipitation and cooler temperatures, from 28.8 to 18.0?cal kyr BP, (2) the Last Glacial Interglacial Transition (LGIT) of increasing effective precipitation and warmer conditions, from 18.0 to 10.2?cal?kyr?BP, and (3) a Holocene interval of high effective precipitation, beginning with a warm period of limited seasonality from 10.2?cal?kyr?BP and followed by increasing seasonality from 7.6?cal?kyr?BP. The LGCP and LGIT also contain millennial-scale climate events, including the coldest inferred glacial conditions during the LGCP from 27.8 to 26.0 and 22.0?C19.0?cal?kyr?BP, and a climate reversal in the LGIT associated with lower lake level, from 14.5 to 13.8?cal?kyr?BP, coeval with the Antarctic Cold Reversal. The onset of seasonal thermal stratification occurred at 5.7?cal?kyr?BP and was linked to natural eutrophication of Lake Pupuke, which produced enhanced organic sedimentation.