Predictability of tropical cyclone events on intraseasonal timescales with the ECMWF monthly forecast model     

Russell L. Elsberry  Mary S. Jordan  Frederic Vitart 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(2):135-153

The objective of this study is to provide evidence of predictability on intraseasonal time scales (10–30 days) for western North Pacific tropical cyclone formation and subsequent tracks using the 51-member ECMWF 32-day forecasts made once a week from 5 June through 25 December 2008. Ensemble storms are defined by grouping ensemble member vortices whose positions are within a specified separation distance that is equal to 180 n mi at the initial forecast time t and increases linearly to 420 n mi at Day 14 and then is constant. The 12-h track segments are calculated with a Weighted-Mean Vector Motion technique in which the weighting factor is inversely proportional to the distance from the endpoint of the previous 12-h motion vector. Seventy-six percent of the ensemble storms had five or fewer member vortices. On average, the ensemble storms begin 2.5 days before the first entry of the Joint Typhoon Warning Center (JTWC) best-track file, tend to translate too slowly in the deep tropics, and persist for longer periods over land. A strict objective matching technique with the JTWC storms is combined with a second subjective procedure that is then applied to identify nearby ensemble storms that would indicate a greater likelihood of a tropical cyclone developing in that region with that track orientation. The ensemble storms identified in the ECMWF 32-day forecasts provided guidance on intraseasonal timescales of the formations and tracks of the three strongest typhoons and two other typhoons, but not for two early season typhoons and the late season Dolphin. Four strong tropical storms were predicted consistently over Week-1 through Week-4, as was one weak tropical storm. Two other weak tropical storms, three tropical cyclones that developed from precursor baroclinic systems, and three other tropical depressions were not predicted on intraseasonal timescales. At least for the strongest tropical cyclones during the peak season, the ECMWF 32-day ensemble provides guidance of formation and tracks on 10–30 day timescales.  相似文献   

Long-term influence of maritime access works on the distribution of cohesive sediments: analysis of historical and recent data from the Belgian nearshore area (southern North Sea)     

Michael Fettweis  Jean-Sébastien Houziaux  Isabelle Du Four  Vera Van Lancker  Cecile Baeteman  Mieke Mathys  Dries Van den Eynde  Frederic Francken  Stanislas Wartel 《Geo-Marine Letters》2009,29(5):321-330

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A note on the isolation of the bacteriumVibrio parahaemolyticus from estuarine North Carolina     

Robert B. Jonas  Earle N. Buckley  Frederic K. Pfaender 《Estuaries and Coasts》1978,1(4):264-266

The potentially pathogenic bacterium,Vibrio parahaemolyticus, was isolated from water, sediment, and oyster samples collected from estuarine North Carolina. In October, when water temperatures were 15–18°C,V. parahaemolyticus was still detected in all substrates. However, the organism was detected only in one sediment sample in January when water temperatures were 4–5°C. No correlation was observed between the occurrence of the bacterium and domestic wastewater contamination.  相似文献   

Are people of Indian origin (PIO) “Indian”? A case study of South Africa     

Frederic Landy  Brij Maharaj 《Geoforum》2004,35(2):203-215

A necessary condition for a migration to be considered as a “diaspora” is the upholding of contacts in the land of origin in various forms, real or imaginary, material or cultural. This paper examines whether this is so in the case of Indian South Africans, most of whose ancestors came to the country as indentured labourers between 1860 and 1911. A key contention was that there could be some cultural and emotional factors partly explaining the economic relations and the geography of flows between the South Africans of Indian origin and India. However, this eventually proved to be wrong. This is all the more paradoxical since the “Indian” identity is still very alive in Durban. However, it is highly fragmented, according to the generations, the religions and the socio-economic classes. India is still a key referent, but “transcendentally”: either as a country which has only an abstract existence, which is spoken of, even dreamt of, without ever being visited; or it is visited but considered only as a whole, since the region of one’s ancestors is almost never at the forefront. Furthermore, the vulnerable situation of “Indians” within South African society does not encourage stronger relationships with India.  相似文献   

Effects of Spectral Nudging on Oceanic States in a Coarse-Resolution Model     

Zeliang Wang  Guoqi Han  Frederic Dupont 《大气与海洋》2015,53(3):351-362

A 1-degree global model is used to investigate the skill of spectral nudging at coarse resolution by performing two numerical experiments, one with spectral nudging and the other without. In the spectral nudging experiment, the model temperature and salinity are nudged to an observed climatological monthly-mean field. The study compares the model mean state, as well as the interannual and decadal variability of oceanic quantities with observations, (e.g., sea surface height (SSH) and sea surface temperature (SST)). Spectral nudging is found to be effective in constraining model drift from the observed mean state of temperature and salinity in the global ocean, which has been reported in previous studies. The present study further shows that spectral nudging significantly improves the model skill of topostrophy (a measure of currents flowing along the topography) in water depth below 2000?m with no clear improvement elsewhere. Despite its known ability to damp oceanic variability at various time scales, spectral nudging can still represent the interannual and decadal variability of SSH and SST well, to a degree comparable to the other experiment.  相似文献   

The patchy accretion disc in HT Cassiopeiae     

Sonja Vrielmann  Frederic V. Hessman  Keith Horne 《Monthly notices of the Royal Astronomical Society》2002,332(1):176-192

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Runaway collisions in young star clusters – II. Numerical results     

Marc Freitag †  M. Atakan Gürkan  Frederic A. Rasio 《Monthly notices of the Royal Astronomical Society》2006,368(1):141-161

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Eccentricities of Planets in Binary Systems     

Genya Takeda  Frederic A. Rasio 《Astrophysics and Space Science》2006,304(1-4):239-242

The most puzzling property of the extrasolar planets discovered by recent radial velocity surveys is their high orbital eccentricities, which are very difficult to explain within our current theoretical paradigm for planet formation. Current data reveal that at least 25% of these planets, including some with particularly high eccentricities, are orbiting a component of a binary star system. The presence of a distant companion can cause significant secular perturbations in the orbit of a planet. At high relative inclinations, large-amplitude, periodic eccentricity perturbations can occur. These are known as “Kozai cycles” and their amplitude is purely dependent on the relative orbital inclination. Assuming that every planet host star also has a (possibly unseen, e.g., substellar) distant companion, with reasonable distributions of orbital parameters and masses, we determine the resulting eccentricity distribution of planets and compare it to observations? We find that perturbations from a binary companion always appear to produce an excess of planets with both very high (?0.6) and very low (e ? 0.1) eccentricities. The paucity of near-circular orbits in the observed sample implies that at least one additional mechanism must be increasing eccentricities. On the other hand, the overproduction of very high eccentricities observed in our models could be combined with plausible circularization mechanisms (e.g., friction from residual gas) to create more planets with intermediate eccentricities (e? 0.1–0.6).  相似文献   

The Cu isotopic composition of iron meteorites     

Matthew Cole BISHOP  Frederic MOYNIER  Charlotte WEINSTEIN  Jean‐Gabriel FRABOULET  Kun WANG  Julien FORIEL 《Meteoritics & planetary science》2012,47(2):268-276

Abstract– High‐precision Cu isotopic compositions have been measured for the metal phase of 29 iron meteorites from various groups and for four terrestrial standards. The data are reported as the δ⁶⁵Cu permil deviation of the ⁶⁵Cu/⁶³Cu ratio relative to the NIST SRM 976 standard. Terrestrial mantle rocks have a very narrow range of variations and scatter around zero. In contrast, iron meteorites show δ⁶⁵Cu approximately 2.3‰ variations. Different groups of iron meteorites have distinct δ⁶⁵Cu values. Nonmagmatic IAB‐IIICD iron meteorites have similar δ⁶⁵Cu (0.03 ± 0.08 and 0.12 ± 0.10, respectively), close to terrestrial values (approximately 0). The other group of nonmagmatic irons, IIE, is isotopically distinct (?0.69 ± 0.15). IVB is the iron meteorite group with the strongest elemental depletion in Cu and samples in this group are enriched in the lighter isotope (δ⁶⁵Cu down to ?2.26‰). Evaporation should have produced an enrichment in ⁶⁵Cu over ⁶³Cu (δ⁶⁵Cu >0) and can therefore be ruled out as a mechanism for volatile loss in IVB meteorites. In silicate‐bearing iron meteorites, Δ¹⁷O correlates with δ⁶⁵Cu. This correlation between nonmass‐dependent and mass‐dependent parameters suggests that the Cu isotopic composition of iron meteorites has not been modified by planetary differentiation to a large extent. Therefore, Cu isotopic ratios can be used to confirm genetic links. Cu isotopes thus confirm genetic relationships between groups of iron meteorites (e.g., IAB and IIICD; IIIE and IIIAB); and between iron meteorites and chondrites (e.g., IIE and H chondrites). Several genetic connections between iron meteorites groups are confirmed by Cu isotopes, (e.g., IAB and IIICD; IIIE and IIIAB); and between iron meteorites and chondrites (e.g., IIE and H chondrites).  相似文献   

Fundamental changes in the activity of the natrocarbonatite volcano Oldoinyo Lengai, Tanzania     

Matthieu Kervyn  Gerald G. J. Ernst  Jörg Keller  R. Greg Vaughan  Jurgis Klaudius  Evelyne Pradal  Frederic Belton  Hannes B. Mattsson  Evelyne Mbede  Patric Jacobs 《Bulletin of Volcanology》2010,72(8):913-931

On September 4, 2007, after 25 years of effusive natrocarbonatite eruptions, the eruptive activity of Oldoinyo Lengai (OL), N Tanzania, changed abruptly to episodic explosive eruptions. This transition was preceded by a voluminous lava eruption in March 2006, a year of quiescence, resumption of natrocarbonatite eruptions in June 2007, and a volcano-tectonic earthquake swarm in July 2007. Despite the lack of ground-based monitoring, the evolution in OL eruption dynamics is documented based on the available field observations, ASTER and MODIS satellite images, and almost-daily photos provided by local pilots. Satellite data enabled identification of a phase of voluminous lava effusion in the 2 weeks prior to the onset of explosive eruptions. After the onset, the activity varied from 100 m high ash jets to 2–15 km high violent, steady or unsteady, eruption columns dispersing ash to 100 km distance. The explosive eruptions built up a ∼400 m wide, ∼75 m high intra-crater pyroclastic cone. Time series data for eruption column height show distinct peaks at the end of September 2007 and February 2008, the latter being associated with the first pyroclastic flows to be documented at OL. Chemical analyses of the erupted products, presented in a companion paper (Keller et al. 2010), show that the 2007–2008 explosive eruptions are associated with an undersaturated carbonated silicate melt. This new phase of explosive eruptions provides constraints on the factors causing the transition from natrocarbonatite effusive eruptions to explosive eruptions of carbonated nephelinite magma, observed repetitively in the last 100 years at OL.  相似文献