Spectroscopic and polarimetric observations of QS Tel     

E. Romero‐Colmenero  S. B. Potter  D. A. H. Buckley 《Astronomische Nachrichten》2004,325(3):214-214

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Tree-ring records from New Zealand: long-term context for recent warming trend     

R. D. D’Arrigo  E. R. Cook  M. J. Salinger  J. Palmer  P. J. Krusic  B. M. Buckley  R. Villalba 《Climate Dynamics》1998,14(3):191-199

 Distinct periods of warmth have been identified in instrumental records for New Zealand and the surrounding southwest Pacific over the past 120 years. Whether this warming is due to natural climate variability or the effects of increasing greenhouse gases is difficult to determine given the limited length of instrumental record. Longer records derived from tree rings can help reduce uncertainties in detection of possible causes of climatic change, although relatively few such records have been developed for the Southern Hemisphere. In this work, we describe five temperature-sensitive tree-ring width chronologies for New Zealand which place the recent warming trend into a long-term (pre-anthropogenic) context. Included are three pink pine (Halocarpus biformis) chronologies, two for Stewart Island and one for the North Island of New Zealand. Two silver pine (Lagarostrobus colensoi) series, one each from the North and South Islands, are updated from previous work. The length of record ranges from AD 1700 for Putara, North Island to AD 1400 for Ahaura, South Island. The pink and silver pine are different species from those used previously to reconstruct temperatures for New Zealand. All five chronologies are positively and significantly correlated with warm-season (November-April) individual station temperature records, a New Zealand-wide surface air temperature index and gridded land/marine temperatures for New Zealand and vicinity. The highest 20 and 40-year growth periods in all five tree-ring series coincide with the New Zealand temperature increase after 1950. An exception is found for the 40-year interval at Ahaura, the least temperature-sensitive of the five sites. A t-test comparison indicates that these recent growth intervals are significantly higher (0.01 to 0.0001 level) than any of those prior to the twentieth century for three of the five sites, dating as far back as AD 1500. The results suggest that the recent warming has been distinctive, although not clearly unprecedented, relative to temperature conditions inferred from tree-ring records of prior centuries. Received: 18 February 1997/Accepted: 11 September 1997  相似文献   

Uncertainty Analyses of Fuel Hydrocarbon Biodegradation Signatures in Ground Water by Probabilistic Modeling   总被引：1，自引：0，他引：1  

Walt W. McNab Jr.  Brendan P. Dooher 《Ground water》1998,36(4):691-698

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Stereoscopic observations of gamma rays at the Whipple observatory     

F. Krennrich  C.W. Akerlof  J.H. Buckley  J. Bussóns-Gordo  D.A. Carter-Lewis  M.F. Cawley  M.A. Catanese  V. Connaughton  D.J. Fegan  J.P. Finley  J.A. Gaidos  K.H. Harris  A.M. Hillas  R.C. Lamb  M.J. Lang  G. Mohanty  J. Quinn  A.J. Rodgers  H.J. Rose  A.C. Rovero  M.S. Schubnell  G.H. Sembroski  T.C. Weekes  C. Wilson 《Astroparticle Physics》1998,8(4):213-221

Observations of photons at E ≥ 550 GeV from the Crab Nebula are presented and used to assess the potential of multi-telescope systems for γ-ray astronomy.

The Whipple observatory 10 m and 8 m imaging atmospheric erenkov telescopes have been used to provide a stereoscopic view of air showers to make a more complete measurement of air shower parameters. Here we present a measurement of the spread in the arrival direction of primary γ-rays originating from a point source. The data show that the shower arrival direction can be reconstructed with an accuracy of σ = 0.°14.  相似文献   

RX J0744−52: a probable new intermediate polar     

Gavin Ramsay  David A. H. Buckley  & Mark Cropper 《Monthly notices of the Royal Astronomical Society》1998,294(1):187-192

We present optical and X-ray data of the cataclysmic variable RX 0744−52 discovered using ROSAT by Motch et al. High-resolution spectroscopy centred on the Hα line indicates a probable orbital period of 3.60 h. From its distance (obtained using polarimetry), its X-ray luminosity, its X-ray colour and its X-ray/UV+optical ratio, we suggest that RX 0744−52 is a new intermediate polar. The absence of a significant coherent modulation in the X-ray light curve suggests either that RX 0744−52 has a low inclination or that the rotational and magnetic axes must be closely aligned. This is consistent with its small radial velocity amplitude.  相似文献   

X-ray confirmation of the new intermediate polar RX J1238–38     

Coel Hellier  A. P. Beardmore  & David A. H. Buckley 《Monthly notices of the Royal Astronomical Society》1998,299(3):851-854

By finding a 2147-s X-ray pulsation in the recently identified ROSAT   source RX  1238–38 we confirm that it is a member of the intermediate polar class of cataclysmic variable. We analyse the spectral changes over the white dwarf spin cycle, but are unable to distinguish between competing mechanisms for the cause of the pulsation. RX  1238–38 has an anomalous ratio of spin period to orbital period, similar to that of EX Hya.  相似文献   

Urban scale modelling: The Sydney hailstorm of 14 April 1999     

M. S. Speer  L. M. Leslie  L. Qi  B. W. Buckley 《Meteorology and Atmospheric Physics》2004,87(1-3):161-166

Summary The aim of this study is to point to the very large improvements that are taking place in a range of modelling applications in the urban areas. The particular phenomenon chosen in this study is a supercell, but it could well have been any other aspect of urban modelling. The Sydney hailstorm of 14 April 1999 was a long-lived, high precipitation supercell that produced a massive damage bill of over 2 billion Australian dollars from its hail swath. The Sydney hailstorm was poorly forecast for a number of reasons including: the severe weather season had officially ended so there were no specialist staff on duty when the hailstorm struck Sydney; the storm proved very difficult to predict and it was expected to continue heading out to sea; and the forecast guidance from all available operational numerical models was inadequate at the resolution required for a supercell simulation. Here, our interest is on the last of the problems, namely, the quality of the operational numerical model guidance, especially given the impact it had on a densely populated urban region.In this study, we compare the numerical guidance available at the time with current modeling capability which, although in research mode at present, will soon be available in real-time mode. The operational models were hydrostatic models run at horizontal resolutions of 25km at best, compared with 1km horizontal resolution for the non-hydrostatic research model. The research model also had a high-order differencing scheme and a sophisticated six phase cloud physics scheme compared with the much simpler parameterized convection in the operational models. The operational model produced very little convective precipitation and it was displaced well to the north of Sydney. The research model generated a supercell with a track and a hail size distribution that was encouragingly close to the observed.  相似文献   

Bedload sediment transport dynamics in a macrotidal embayment, and implications for export to the southern Great Barrier Reef shelf   总被引：1，自引：0，他引：1  

David A. Ryan  Brendan P. Brooke  Helen C. Bostock  Lynda C. Radke  Paulus J.W. Siwabessy  Nugzar Margvelashvili  Darren Skene   《Marine Geology》2007,240(1-4):197-215

Keppel Bay is a macrotidal embayment on a tectonically stable, tropical coast, which links the Fitzroy River with the Great Barrier Reef continental shelf. Estuaries and deltas act as conduits between catchments and inner shelf environments. Therefore, understanding sediment transport pathways in these complex systems is essential for the management of ecosystems such as coral-reefs that are potentially vulnerable to enhanced river sediment loads. Furthermore, the morphology and sediment dynamics of subtidal sand ridges and dunes are relatively poorly characterised in macrotidal estuaries, particularly in turbid, episodic systems such as the Fitzroy River and Keppel Bay. Our sedimentological analysis of seabed samples, shear-stress modelling and three-dimensional acoustic imaging reveals that Keppel Bay is a mixed wave- and tide-dominated estuarine system. Areas of sediment starvation and shoreward transport characterise the offshore zone, whereas a complex of both active and relict tidal sand ridges, and associated subaqueous dunes, dominate the relatively protected southern Keppel Bay. Transport within this region is highly dynamic and variable, with ebb-dominated sediment transport through tidal channels into the outer bay where there is a switch to wave-dominated shoreward transport. Ultimately, bedload sediments appear to be reworked back inshore and to the north, and are gradually infilling the bedrock-defined embayment. Our characterisation of the Keppel Bay system provides a detailed example of the physiography of the seaward portion of a tide-dominated system, and shows that sediment transport in these areas is influenced by a variable hydrodynamic regime as well as relict channels and bedrock topography.  相似文献   

The circulation, water masses and sea-ice of Baffin Bay   总被引：2，自引：0，他引：2  

Charles C.L Tang  Charles K. Ross  Tom Yao  Brian Petrie  Brendan M. DeTracey  Ewa Dunlap 《Progress in Oceanography》2004,63(4):183-228

The oceanographic, meteorological and sea-ice conditions in Baffin Bay are studied using historical hydrographic, satellite and meteorological data, and a set of current meter data from a mooring program of the Bedford Institute of Oceanography. Baffin Bay is partially covered by sea-ice all year except August and September. The interannual variation of the ice extent is shown to be correlated with winter air temperature. Available hydrographic data were used to study the water masses and the horizontal and vertical distribution of temperature/salinity. Three water masses can be identified – Arctic Water in the upper 100–300 m of all regions except the southeast, West Greenland Intermediate Water at 300–800 m in most of the interior of Baffin Bay, and Deep Baffin Bay Water in all regions below 1200 m. The temperature and salinity in Baffin Bay have limited seasonal variability except in the upper 300 m of eastern Davis Strait, northern Baffin Bay and the mouth of Lancaster Sound. Summer data have a temperature minimum at 100 m, which suggests winter convection does not penetrate deeper than this depth. Current meter data and results of a circulation model indicate that the mean circulation is cyclonic. The seasonal variation of the currents is complex. Overall, summer and fall tend to have stronger currents than winter and spring at all depths. Among the different regions, the largest seasonal variation occurs at the mouth of Lancaster Sound and the Baffin Island slope. Model generated velocity fields show a basic agreement with the observed currents, and indicate strong topographic control in the vicinity of Davis Strait and on the Greenland shelves. The model also produces a southward counter current on the Greenland slope, which may explain the observed high horizontal shears over the Greenland slope. Estimates of the volume and fresh water transports through Lancaster, Jones and Smith Sounds are reviewed. Transports through Davis Strait are computed from the current meter data. The balance of freshwater budget and sensitivity of the thermohaline circulation to freshwater transport are discussed.  相似文献   

Quantifying the local influence at a tall tower site in nocturnal conditions     

David?WerthEmail author  Robert?Buckley  Gengsheng?Zhang  Robert?Kurzeja  Monique?Leclerc  Henrique?Duarte  Matthew?Parker  Thomas?Watson 《Theoretical and Applied Climatology》2017,127(3-4):627-642

The influence of the local terrestrial environment on nocturnal atmospheric CO₂ measurements at a 329-m television transmitter tower (and a component of a CO₂ monitoring network) was estimated with a tracer release experiment and a subsequent simulation of the releases. This was done to characterize the vertical transport of emissions from the surface to the uppermost tower level and how it is affected by atmospheric stability. The tracer release experiment was conducted over two nights in May of 2009 near the Department of Energy’s Savannah River Site (SRS) in South Carolina. Tracer was released on two contrasting nights—slightly stable and moderately stable—from several upwind surface locations. Measurements at the 329-m level on both nights indicate that tracer was able to mix vertically within a relatively short (～24 km) distance, implying that nocturnal stable conditions do not necessarily prevent vertical dispersion in the boundary layer and that CO₂ measurements at the tower are at least partly influenced by nearby emissions. A simulation of the tracer release is used to calculate the tower footprint on the two nights to estimate the degree to which the local domain affects the tower readings. The effect of the nocturnal boundary layer on the area sampled by the tower can be seen clearly, as the footprints were affected by changes in stability. The contribution of local sources to the measurements at the tower was minimal, however, suggesting that nocturnal concentrations at upper levels are contributed mostly by regional sources.  相似文献