Intense tropical cyclogenesis over the northwest Australian region in 1998/1999: Causal factors     

L. M. Leslie  R. F. Abbey Jr.  M. S. Speer  T. C. L. Skinner 《Meteorology and Atmospheric Physics》2002,80(1-4):89-101

Summary The 1998/99 tropical cyclone (TC) season over northwest Australia was notable for an above average number of TCs (seven compared to five on average) and a number of unusually intense TCs making landfall (three category 5 TCs). The active 1998/99 TC season is attributed here to a combination of a number of broad-scale features over the south east Indian Ocean and the Australian region, with identifiable precursors favoring tropical cyclogenesis. These precursors include: below normal MSLP, abnormally warm ocean temperatures, above average relative humidity in the low- to mid-tropospheric levels and weak wind shears in the genesis region under study, that is, between 10° S to 20° S and 105° E to 135° E. These favorable conditions first appeared as early as August 1998. The appearance of favorable conditions so far ahead of the TC season indicates that they are the likely cause of the enhanced TC activity rather than simply an effect. Although the season as a whole was an active one, strong intra-seasonal variability was evident in that there were two named TCs in December 1998, forming within three days of each other. Only one formed in January 1999 and none in February. By contrast, in March and April 1999, TC activity was enhanced once again, with four named TCs, three of which attained category 5 status. The importance of the above-mentioned precursors in favoring tropical cyclogenesis during the 1998/99 season is discussed in terms of seasonal time scales of the preceding spring and down to synoptic and mesoscale time scales ranging from several days to 48 hours or less. Received October 5, 2001 Revised December 28, 2001  相似文献   

Light-cued emergence and re-entry events in a strongly tidal estuary     

Heather U. Abello  Shawn M. Shellito  Leslie H. Taylor  Peter A. Jumars 《Estuaries and Coasts》2005,28(4):487-499

Acoustic backscatter from an active sonar system (TAPS-6) over a range of six frequencies between 265 kHz and 3 MHz revealed characteristics of emergence and reentry events within 1 h of sunset and sunrise, respectively, at a site 10 m deep in the Damariscotta River estuary, Maine. Emergence traps indicated that the mysid shrimpNeomysis americana was the dominant migrator. Daily fluctuation in irradiance influenced the timing of dusk emergence. Local variability in irradiance apparently caused populations to emerge occasionally before sunset or to leave the surface after the beginning of nautical twilight near dawn. Emergence before sunset was marked by slower-than-average ascent, and departure from the surface after initiation of nautical twilight was marked by faster-than-average descent. This pattern would be expected for populations avoiding visual predators by concealment in dark water. Mean ascent (0.29 ± 0.03 cm s⁻¹ [±1 SE]) and descent (−0.26 ± 0.02 cm s⁻¹) velocities showed little difference in magnitude, suggesting that a similar mechanism controls both. Ascent initiation times for the first such event of the night were consistent with a cue based on relative rate of change in light intensity and inconsistent with either the progress of isolumes or with absolute rate of change in light intensity.  相似文献   

A deterministic algorithm for experimental design applied to tomographic and microseismic monitoring surveys   总被引：1，自引：0，他引：1  

Andrew Curtis  Alberto Michelini  David Leslie  Anthony Lomax 《Geophysical Journal International》2004,157(2):595-606

  相似文献   

A GIS framework for Traffic Emission Information System     

L. Xia  L. M. Leslie 《Meteorology and Atmospheric Physics》2004,87(1-3):153-160

Summary A coefficient-based vehicular exhaust emission model is being developed jointly with the variable-grid urban airshed model (UAM-V) of Systems Applications International (SAI), and integrated within a GIS (ArcInfo) framework. When coupled with a road network, traffic features and meteorological as well as geographical databases, this framework produces a Traffic Emission Information System (TEIS). With this TEIS, the emission coefficients of CO, NOx and VOC for Sydney in the calendar year 2000 are derived; and the emission rates of the pollutants are then estimated using sample traffic profile data for the Sydney metropolitan area. Finally, ongoing improvements to the system are presented.  相似文献   

Geochemical variations within a laminated evaporite deposit: evidence for brine composition during formation of the Permian Castile Formation, Texas and New Mexico, USA     

Alick B. Leslie  Gill M. Harwood  Alan C. Kendall 《Sedimentary Geology》1997,110(3-4):223-235

The Upper Permian Castile Formation of the Delaware Basin in northwest Texas and New Mexico consists of up to 600 m of evaporites and is subdivided into units of anhydrite overlain by halite. The Castile Formation has commonly been interpreted as a deep-water, deep-basin deposit in which sediments were laid down in several hundred metres of water or brine. Recent textural observations within anhydrite units, in which the thick-bedded anhydrite horizons have been interpreted as being of shallow-water origin, have challenged this assumption. This geochemical study of the oldest anhydrite unit in the Castile Formation (the Anhydrite 1 Member) attempts to resolve some of the problems regarding brine depth and evolution in the basin. The Anhydrite 1 Member has been subdivided into five major cycles on the basis of the distribution of stratigraphic units of thick-bedded anhydrite.

Stable isotopic analyses of sulphur from anhydrite, and oxygen and carbon from calcite show that the basin waters were chemically homogeneous during precipitation of anhydrite, and do not indicate any significant input of meteoric, continental-derived waters. Throughout the section studied progressive enrichment of ¹⁸O upwards within cored intervals indicates continuous evaporation of the water body. Carbon isotopes appear to indicate fluctuations in organic activity within the cycles. Trace elemental analyses of Fe, Mg, Sr, Mn, Al, Ba, Zn, Pb and Cu from the sulphate fraction of the samples show a very high variability. There is a distinct increase in trace elemental abundances at the tops of cycles which may indicate variations in precipitation kinetics. Analyses of texturally defined cycles show that up-core trends for many of the trace elements correlate with changes in δ¹⁸O, indicating a progressive increase in the influence of evaporation. In addition, cyclical variations in trace elemental composition indicate changes in basin conditions with around a 350-year cyclicity. These changes are independent of δ¹⁸O values. The geochemical data do not provide conclusive proof of water depth during deposition of the Castile Formation. The data are interpreted as reflecting small-scale changes in conditions of deposition, despite the fact that water input remained essentially constant in terms of chemical composition.  相似文献   

Risky subjects: changing geographies of employment in the automobile industry     

David Butz  & Deborah Leslie 《Area》2001,33(2):212-219

  相似文献   

An experimental investigation of the quartz, Na-K, Na-K-Ca geothermometers and the effects of fluid composition     

Leslie A. Pope  Andrew Hajash  Robert K. Popp 《Journal of Volcanology and Geothermal Research》1987,31(1-2)

To test the possible effect of different fluid compositions on some standard geothermometry techniques, experiments were conducted in which a rhyolite from the Presidio Bolson area of West Texas was interacted with fluids of two different compositions (0.1 M NaCl and 0.01 M NaHCO₃). The temperature range was 100–500°C, pressure was 1000 bars, water/rock mass ratios were 6:1 and 5:1, and the duration of the experiments ranged from 12 to 130 days.Results showed that the quartz geothermometer worked well in the experimental system up to temperatures of 400°C. The results were not affected by differences in the major anionic species.The Na-K geothermometer gave temperatures an average of 76°C lower than the experimental temperatures, regardless of fluid type. The experimental data from this study agree well with previous experimental work in feldsparquartz systems.The Na-K-Ca geothermometer did not work well for experiments using 0.01 M NaHCO₃ but did work well for experiments using 0.1 M NaCl. Benjamin et al. (1983) concluded that the Na-K-Ca geothermometer is based on alteration reactions rather than feldspar exchange; however, no evidence for alteration reactions was observed in this study.  相似文献   

A rare East Indian Ocean autumn season tropical cut-off low: impacts and a high-resolution modelling study     

B. W. Buckley  L. M. Leslie  W. Sullivan  M. Leplastrier  L. Qi 《Meteorology and Atmospheric Physics》2007,96(1-2):61-84

  相似文献   

A high-resolution simulation of microphysics and electrification in an idealized hurricane-like vortex   总被引：1，自引：0，他引：1  

A. O. Fierro  L. Leslie  E. Mansell  J. Straka  D. MacGorman  C. Ziegler 《Meteorology and Atmospheric Physics》2007,98(1-2):13-33

  相似文献   

Zircon U–Pb,O, and Hf isotopic constraints on Mesozoic magmatism in the Cyclades,Aegean Sea,Greece     

Bin Fu  Michael Bröcker  Trevor Ireland  Peter Holden  Leslie P. J. Kinsley 《International Journal of Earth Sciences》2015,104(1):75-87

  相似文献