Implications of CMIP3 model biases and uncertainties for climate projections in the western tropical Pacific   总被引：1，自引：0，他引：1  

Jaclyn N. Brown  Alex Sen Gupta  Josephine R. Brown  Les C. Muir  James S. Risbey  Penny Whetton  Xuebin Zhang  Alexandre Ganachaud  Brad Murphy  Susan E. Wijffels 《Climatic change》2013,119(1):147-161

Regional climate projections in the Pacific region are potentially sensitive to a range of existing model biases. This study examines the implications of coupled model biases on regional climate projections in the tropical western Pacific. Model biases appear in the simulation of the El Niño Southern Oscillation, the location and movement of the South Pacific Convergence Zone, rainfall patterns, and the mean state of the ocean–atmosphere system including the cold tongue bias and erroneous location of the edge of the Western Pacific warm pool. These biases are examined in the CMIP3 20th century climate models and used to provide some context to the uncertainty in interpretations of regional-scale climate projections for the 21st century. To demonstrate, we provide examples for two island nations that are located in different climate zones and so are affected by different biases: Nauru and Palau. We discuss some of the common approaches to analyze climate projections and whether they are effective in reducing the effect of model biases. These approaches include model selection, calculating multi model means, downscaling and bias correcting.  相似文献   

Simulating a white dwarf dominated Galactic halo     

Chris B. Brook  Daisuke Kawata  Brad K. Gibson 《Monthly notices of the Royal Astronomical Society》2003,343(3):913-923

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REVISED AGE FOR THE GOSSES BLUFF IMPACT STRUCTURE,NORTHERN TERRITORY,AUSTRALIA, BASED ON 40Ar/39Ar DATING     

Daniel J. Milton  John F. Sutter 《Meteoritics & planetary science》1987,22(3):281-289

⁴⁰Ar/³⁹ Ar dating of a pumiceous suevite clast from the melt breccia at Gosses Bluff consisting largely of extremely fine-grained sanidine yields a discordant age spectrum, probably reflecting some diffusional loss of argon. High-temperature increments that together yield a near-plateau age of 142.5 Ma are apparently not affected by argon loss and offer the best estimate of the date of the Gosses Bluff event. The event may fall in the latest Jurassic Period, but more likely falls in the earliest Cretaceous, probably in one of the reverse-polarity magnetochrons M16, M17, or M18.  相似文献   

N-body simulations of the Magellanic stream   总被引：1，自引：0，他引：1  

Tim W. Connors  Daisuke Kawata  Brad K. Gibson 《Monthly notices of the Royal Astronomical Society》2006,371(1):108-120

A suite of high-resolution N -body simulations of the Magellanic Clouds–Milky Way system are presented and compared directly with newly available data from the H  i Parkes All-Sky Survey (HIPASS). We show that the interaction between Small Magellanic Clouds (SMC) and Large Magellanic Clouds results in both a spatial and kinematical bifurcation of both the stream and the leading arm. The spatial bifurcation of the stream is readily apparent in the HIPASS data, and the kinematical bifurcation is also tentatively identified. This bifurcation provides strong support for the tidal disruption origin for the Magellanic stream. A fiducial model for the Magellanic Clouds (MCs) is presented upon completion of an extensive parameter survey of the potential orbital configurations of the MCs and the viable initial boundary conditions for the disc of the SMC. The impact of the choice of these critical parameters upon the final configurations of the stream and leading arm is detailed.  相似文献   

A conceptual model of avalanche hazard     

Grant Statham  Pascal Haegeli  Ethan Greene  Karl Birkeland  Clair Israelson  Bruce Tremper  Chris Stethem  Bruce McMahon  Brad White  John Kelly 《Natural Hazards》2018,90(2):663-691

This conceptual model of avalanche hazard identifies the key components of avalanche hazard and structures them into a systematic, consistent workflow for hazard and risk assessments. The method is applicable to all types of avalanche forecasting operations, and the underlying principles can be applied at any scale in space or time. The concept of an avalanche problem is introduced, describing how different types of avalanche problems directly influence the assessment and management of the risk. Four sequential questions are shown to structure the assessment of avalanche hazard, namely: (1) What type of avalanche problem(s) exists? (2) Where are these problems located in the terrain? (3) How likely is it that an avalanche will occur? and (4) How big will the avalanche be? Our objective was to develop an underpinning for qualitative hazard and risk assessments and address this knowledge gap in the avalanche forecasting literature. We used judgmental decomposition to elicit the avalanche forecasting process from forecasters and then described it within a risk-based framework that is consistent with other natural hazards disciplines.  相似文献   

Circulation of the Venus upper mesosphere/lower thermosphere: Doppler wind measurements from 2001–2009 inferior conjunction,sub-millimeter CO absorption line observations     

R. Todd Clancy  Brad J. Sandor  Gerald Moriarty-Schieven 《Icarus》2012,217(2):794-812

Sub-millimeter ¹²CO (346 GHz) and ¹³CO (330 GHz) line absorptions, formed within the mesospheric to lower thermospheric altitude (70–120 km) region of the Venus atmosphere, have been mapped across the nightside disk of Venus during 2001–2009 inferior conjunctions, employing the James Clerk Maxwell Telescope (JCMT). Radiative transfer analysis of these thermal line absorptions supports temperature and CO mixing profile retrievals, as described in a companion paper (Clancy et al., 2012). Here, we consider the analysis of the sharp line absorption cores of these CO spectra in terms of accurate Doppler wind profile measurements at 95–115 km altitudes versus local time (～8 pm–4 am) and latitude (～60N–60S). These Doppler wind measurements support determinations of the nightside zonal and subsolar-to-antisolar (SSAS) circulation components over a variety of timescales. The average behavior fitted from 21 retrieved maps of ¹²CO Doppler winds (obtained over hourly, daily, weekly, and interannual intervals) indicates stronger average zonal (85 m/s retrograde) versus SSAS (65 m/s) circulation at the 1 μbar pressure (108–110 km altitude) level. However, the absolute and relative magnitudes of these circulation components exhibit extreme variability over daily to weekly timescales. Furthermore, the individual Doppler wind measurements within each nightside mapping observation generally show significant deviations (20–50 m/s, averaged over 5000 km horizontal scales) from the simple zonal/SSAS solution, with distinct local time and latitudinal characters that are also time variable. These large scale residual circulations contribute 30–70% of the observed nightside Doppler winds at any given time, and may be most responsible for global variations in nightside lower thermospheric trace composition and temperatures, as coincidentally retrieved CO abundance and temperature distributions do not correlate with solution retrograde zonal and SSAS winds (see companion paper, Clancy et al., 2012). Limited comparisons of these nightside submillimeter results with dayside infrared Doppler wind measurements suggest distinct dayside versus nightside circulations, in terms of zonal winds in particular. Combined ¹²CO and ¹³CO Doppler wind mapping observations obtained since 2004 indicate that the average zonal and SSAS wind components increase by 50–100% between altitudes of 100 and 115 km. If gravity waves originating from the cloud levels are responsible for the extension of zonal winds into the thermosphere (Alexander, M.J. [1992]. Geophys. Res. Lett. 19, 2207–2210), such waves deposit substantial momentum (i.e., break) in the lower nightside thermosphere.  相似文献   

Celebrating fifty years of NASA and Earth Observations from Space. Part III: Urban Remote Sensing and Sustainable Urban Systems     

Kamlesh Lulla  M. Duane Nellis  Brad Rundquist 《国际地球制图》2013,28(3):177-178

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Celebrating Geocarto International's Reach     

Kamlesh Lulla  M. Duane Nellis  Brad Rundquist 《国际地球制图》2013,28(1):1-2

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South Korea reaches a major milestone in earth observations     

Kamlesh Lulla  M. Duane Nellis  Brad Rundquist 《国际地球制图》2013,28(4)

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Comparative Evaluation of Single‐Well LNAPL Tracer Testing at Five Sites          下载免费PDF全文

Andrew Pennington  Jonathon Smith  Brad Koons  Craig E. Divine 《Ground Water Monitoring & Remediation》2016,36(2):45-58

Light nonaqueous phase liquid (LNAPL) tracer testing is a technique used to directly measure LNAPL flow in situ and evaluate LNAPL mobility and recoverability. The test method consists of adding a fluorescent oil‐soluble tracer to LNAPL within a well, isolating small volumes of LNAPL with known tracer concentrations for use as in‐well calibration standards, and measuring the rate of tracer concentration decline in the well over time. The test measures LNAPL flux through the well, which is directly related to LNAPL mobility and recoverability in the surrounding formation. Test results for a total of 29 wells at five sites are presented. Results from LNAPL tracer testing were comparable to results obtained through other methods, and the method offers a time‐averaged result measured over a relatively long period, in ambient conditions, and reflects the influences of heterogeneity and hydraulic changes. In some cases, tracer concentration decline followed unexpected patterns, and these data have led to a better understanding of test assumptions, mechanisms influencing tracer distribution, and options to improve test execution and data interpretation. Method improvements developed over the course of the field studies included refinement of pre‐test screening of LNAPL fluorescence and improvements to measurement equipment. Overall, the field studies confirmed the technical validity and usefulness of the LNAPL tracing technique to support LNAPL mobility and recoverability assessments.  相似文献