Observed daily large-scale rainfall patterns during BOBMEX-1999     

A. K. Mitra  M. Das Gupta  R. K. Paliwal  S. V. Singh 《Journal of Earth System Science》2003,112(2):223-232

A daily rainfall dataset and the corresponding rainfall maps have been produced by objective analysis of rainfall data. The satellite estimate of rainfall and the raingauge values are merged to form the final analysis. Associated with epochs of monsoon these rainfall maps are able to show the rainfall activities over India and the Bay of Bengal region during the BOBMEX period. The intra-seasonal variations of rainfall during BOBMEX are also seen using these data. This dataset over the oceanic region compares well with other available popular datasets like GPCP and CMAP. Over land this dataset brings out the features of monsoon in more detail due to the availability of more local raingauge stations.  相似文献   

The subsystem of open clusters in the post-hipparcos era: Cluster structural parameters and proper motions     

N. V. Kharchenko  L. K. Pakulyak  A. E. Piskunov 《Astronomy Reports》2003,47(4):263-275

The wide neighborhoods of 401 open clusters are analyzed using the modern, high-precision, homogeneous ASCC-2.5 all-sky catalog. More than 28000 possible cluster members (including about 12500 most probable members) are identified using kinematic and photometric criteria. Star counts with the ASCC-2.5 and USNO-A2.0 catalogs are used to determine the angular and linear radii of the cluster cores and coronas, which exceed the previously published values by factors of two to three. The segregation (differing central concentration) of member stars by magnitude is observed. The mean proper motions are determined directly in the Hipparcos system for 401 clusters, for 183 of them for the first time. The heliocentric distances of 118 clusters are determined for the first time based on color-magnitude diagrams for their identified members.  相似文献   

The chemically distinct nucleus and structure of the S0 galaxy NGC 80     

O. K. Sil’chenko  S. E. Koposov  V. V. Vlasyuk  O. I. Spiridonova 《Astronomy Reports》2003,47(2):88-98

The giant lenticular galaxy NGC 80, which is the brightest member of a rich group, possesses a central evolutionarily-distinct region: the stars in the nucleus and in a circumnuclear ring of radius 5″t–7″ have a mean age of only 7 Gyr, whereas the stellar population of the bulge is older than 10 Gyr. The nucleus of NGC 80 is also chemically distinct: it is a factor of 2–2.5 richer in metals than its immediate neighborhood and is characterized by a high magnesium-to-iron abundance ratio [Mg/Fe]≈+0.3. The global stellar disk of NGC 80 has a two-tiered structure: its outer part has an exponential scale length of 11 kpc and normal surface density, while the inner disk, which is also exponential and axisymmetric, is more compact and brighter. Although the two-tiered structure and the chemically distinct nucleus obviously have a common origin and owe their existence to some catastrophic restructuring of the protogalactic gaseous disk, the origin of this remains unclear, since the galaxy lacks any manifestations of perturbed morphology or triaxiality.  相似文献   

Impact of Sea-level Rise and Storm Surges on a Coastal Community   总被引：7，自引：7，他引：7  

K. L. Mcinnes  K. J. E. Walsh  G. D. Hubbert  T. Beer 《Natural Hazards》2003,30(2):187-207

A technique to evaluate the risk of storm tides (the combination of a storm surge and tide) under present and enhanced greenhouse conditions has been applied to Cairns on the north-eastern Australian coast. The technique combines a statistical model for cyclone occurrence with a state-of-the-art storm surge inundation model and involves the random generation of a large number of storm tide simulations. The set of simulations constitutes a synthetic record of extreme sea-level events that can be analysed to produce storm tide return periods. The use of a dynamic storm surge model with overland flooding capability means that the spatial extent of flooding is also implicitly modelled. The technique has the advantage that it can readily be modified to include projected changes to cyclone behaviour due to the enhanced greenhouse effect. Sea-level heights in the current climate for return periods of 50, 100, 500 and 1000 years have been determined to be 2.0 m, 2.3 m, 3.0 m and 3.4 m respectively. In an enhanced greenhouse climate (around 2050), projected increases in cyclone intensity and mean sea-level see these heights increase to 2.4 m, 2.8 m, 3.8 m and 4.2 m respectively. The average area inundated by events with a return period greater than 100 years is found to more than double under enhanced greenhouse conditions.  相似文献   

Impact of horizontal resolution on prediction of tropical cyclones over Bay of Bengal using a regional weather prediction model     

M. Mandal  U. C. Mohanty  K. V. J. Potty  A. Sarkar 《Journal of Earth System Science》2003,112(1):79-93

The present study is carried out to examine the performance of a regional atmospheric model in forecasting tropical cyclones over the Bay of Bengal and its sensitivity to horizontal resolution. Two cyclones, which formed over the Bay of Bengal during the years 1995 and 1997, are simulated using a regional weather prediction model with two horizontal resolutions of 165 km and 55 km. The model is found to perform reasonably well towards simulation of the storms. The structure, intensity and track of the cyclones are found to be better simulated by finer resolution of the model as compared to the coarse resolution. Rainfall amount and its distribution are also found to be sensitive to the model horizontal resolution. Other important fields, viz., vertical velocity, horizontal divergence and horizontal moisture flux are also found to be sensitive to model horizontal resolution and are better simulated by the model with finer horizontal grids.  相似文献   

Mercury-bearing black shales and human Hg intake in eastern Finland: impact and mechanisms   总被引：1，自引：0，他引：1  

K. Loukola-Ruskeeniemi  M. Kantola  T. Halonen  K. Seppänen  P. Henttonen  E. Kallio  P. Kurki  H. Savolainen 《Environmental Geology》2003,43(3):283-297

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Flood Management in India     

Mohapatra  P. K.  Singh  R. D. 《Natural Hazards》2003,28(1):131-143

In this paper, flood problems in India, regional variabilityof the problem, present status of the ongoing management measures, their effectiveness and futureneeds in flood management are covered. Flood problems in India are presented by four zonesof flooding, viz. (a) Brahmaputra River Basin, (b) Ganga River Basin, (c) North-WestRivers Basin, and (d) Central India and Deccan Rivers Basin. Some special problems,related to floods like dam break flow, and water logging in Tal areas, are also mentioned.Progress of various flood management measures, both structural and non-structural, arediscussed. In addition, future needs to achieve efficient and successful flood managementmeasures in India are also pointed out.  相似文献   

Preface     

Roger Bilham  S. K. Srivastav 《Journal of Earth System Science》2003,112(3):313-314

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Atomistic simulation of the structure and elastic properties of pyrite (FeS2) as a function of pressure     

Sithole  H.M.  Ngoepe  P.E.  Wright  K. 《Physics and Chemistry of Minerals》2003,30(10):615-619

Interatomic potential parameters have been derived at simulated temperatures of 0 K and 300 K to model pyrite FeS₂. The predicted pyrite structures are within 1% of those determined experimentally, while the calculated bulk modulus is within 7%. The model is also able to simulate the properties of marcasite, even though no data for this phase were included in the fitting procedure. There is almost no difference in results obtained for pyrite using the two potential sets; however, when used to model FeS₂ marcasite, the potential fitted at 0 K performs better. The potentials have also been used to study the high-pressure behaviour of pyrite up to 44 GPa. The calculated equation of state gives good agreement with experiment and shows that the Fe–S bonds shorten more rapidly that the S–S dimer bonds. The behaviour of marcasite at high pressure is found to be similar to that of pyrite.  相似文献   

Ultrahigh-pressure metamorphism in the forbidden zone: the Xugou garnet peridotite, Sulu terrane, eastern China   总被引：21，自引：3，他引：21  

R. Y. Zhang  J. G. Liou  J. S. Yang  K. Ye 《Journal of Metamorphic Geology》2003,21(6):539-550

The Xugou garnet peridotite body of the southern Sulu ultrahigh‐pressure (UHP) terrane is enclosed in felsic gneiss, bounded by faults, and consists of harzburgite and lenses of garnet clinopyroxenite and eclogite. The peridotite is composed of variable amounts of olivine (Fo₉₁), enstatite (En_92?93), garnet (Alm_20?23Prp_53?58Knr_6?9Grs_12?18), diopside and rare chromite. The ultramafic protolith has a depleted residual mantle composition, indicated by a high‐Mg number, very low CaO, Al₂O₃ and total REE contents compared to primary mantle and other Sulu peridotites. Most garnet (Prp_44?58) clinopyroxenites are foliated. Except for rare kyanite‐bearing eclogitic bands, most eclogites contain a simple assemblage of garnet (Alm_29?34Prp_32?50Grs_15?39) + omphacite (Jd_24?36) + minor rutile. Clinopyroxenite and eclogite exhibit LREE‐depleted and LREE‐enriched patterns, respectively, but both have flat HREE patterns. Normalized La, Sm and Yb contents indicate that both eclogite and garnet clinopyroxenite formed by high‐pressure crystal accumulation (+ variable trapped melt) from melts resulting from two‐stage partial melting of a mantle source. Recrystallized textures and P–T estimates of 780–870 °C, 5–7 GPa and a metamorphic age of 231 ± 11 Ma indicate that both mafic and ultramafic protoliths experienced Triassic UHP metamorphism in the P–T forbidden zone with an extremely low thermal gradient (< 5 °C km^?1), and multistage retrograde recrystallization during exhumation. Develop of prehnite veins in clinopyroxenite, eclogite, felsic blocks and country rock gneiss, and replacements of eclogitic minerals by prehnite, albite, white mica, and K‐feldspar indicate low‐temperature metasomatism.  相似文献