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Predicted changes in fire weather suggest increases in lightning fire initiation and future area burned in the mixedwood boreal forest 总被引:1,自引:0,他引:1
Forecasting future fire activity as a function of climate change is a step towards understanding the future state of the western mixedwood boreal ecosystem. We developed five annual weather indices based on the Daily Severity Rating (DSR) of the Canadian Forest Fire Weather Index System and estimated their relationship with annual, empirical counts of lightning fire initiation for 588 landscapes in the mixedwood boreal forest in central-eastern Alberta, Canada from data collected between 1983 and 2001 using zero-inflated negative binomial regression models. Two indices contributed to a parsimonious model of initiation; these were Seasonal Severity Rating (SSR), and DSR-sequence count. We used parameter estimates from this model to predict lightning fire initiation under weather conditions predicted in 1 × CO2 (1975–1985), 2 × CO2 (2040–2049) and 3 × CO2 (2080–2089) conditions simulated by the Canadian Regional Climate Model (CRCM). We combined predicted initiation rates for these conditions with existing empirical estimates of the number of fire initiations that grow to be large fires (fire escapes) and the fire size distribution for the region, to predict the annual area burned by lightning-caused fires in each of the three climate conditions. We illustrated a 1.5-fold and 1.8-fold increase of lightning fire initiation by 2040–2049 and 2080–2089 relative to 1975–1985 conditions due to changes in fire weather predicted by the CRCM; these increases were calculated independent of changes in lightning activity. Our simulations suggested that weather-mediated increases in initiation frequency could correspond to a substantial increase in future area burned with 1.9-fold and 2.6-fold increases in area burned in 2040–2049 and 2080–2089 relative to 1975–1985 conditions, respectively. We did not include any biotic effects in these estimates, though future patterns of initiation and fire growth will be regulated not only by weather, but also by vegetation and fire management. 相似文献
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Piran C L White Steve Cinderby Dave Raffaelli Annemarieke de Bruin Alison Holt Meg Huby 《Area》2009,41(4):414-424
There has been much debate about the importance of policy-relevant research in geography over the last decade. There has also been an increasing recognition by policymakers of the importance of integrative (interdisciplinary and transdisciplinary) approaches to policy-relevant research. However, geographers have been more reluctant than their colleagues in other social and natural sciences to embrace integrative research collaborations. For integrative research to achieve its full potential and to encourage greater participation from the geographical research community, we need to increase our understanding of its potential value, but also some of the challenges that it poses, and how these can be overcome. In this paper, we consider the processes involved in conducting successful integrative research from the perspective of researchers involved in these projects. We base our analysis on the results of a questionnaire survey of international integrative research programmes on environmental issues in rural areas, combined with our own experiences of working in integrative research. We conclude that effective integrative research depends on the establishment of a clear conceptual framework, the use of appropriate temporal and spatial scales in the research, effective language and communication, time and commitment, and trust and respect. We also highlight the value of stakeholder involvement in integrative research to ensure the policy relevance of the work and provide a mechanism to assist with effective knowledge transfer of the results. 相似文献
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Threats to rural livelihoods and rural landscapes have increased over time as developed nations in particular look for cheaper and more locally based alternatives to traditional energy sources to drive national economies. In New South Wales, through the expansion of coal mines and coal seam gas (CSG), small towns such as Gloucester on the edge of the Upper Hunter are faced with competing visions which seek to redefine their future. Powerful and competing discourses over land use threaten not only the sustainability of the region but the integrity of its sense of place, centred on community, rurality, agricultural production and confrontation of risk from mining. The different discourses of local groups such as ‘tree-changers’, established residents and farmers conflict with those of external organisations such as the State government and mining/CSG companies which envisage Gloucester as a ‘balanced’ space of co-existence and position it as a new node in the carbon supply chain. 相似文献
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Paolo Padovani †‡ Luigi Costamante Paolo Giommi Gabriele Ghisellini rea Comastri Anna Wolter Laura Maraschi Gianpiero Tagliaferri C. Megan Urry 《Monthly notices of the Royal Astronomical Society》2001,328(3):931-943
We present new BeppoSAX observations of seven BL Lacertae objects selected from the 1-Jy sample plus one additional source. The collected data cover the energy range (observer's frame), reaching ∼50 keV for one source (BL Lac). All sources characterized by a peak in their multifrequency spectra at infrared/optical energies (i.e., of the low-energy peaked BL Lac type, LBL) display a relatively flat X-ray spectrum, which we interpret as inverse Compton emission. Four objects (two-thirds of the LBLs) show some evidence for a low-energy steepening, which is probably due to the synchrotron tail merging into the inverse Compton component around ∼ . If this were generally the case with LBLs, it would explain why the ROSAT spectra of our sources are systematically steeper than the BeppoSAX ones . The broad-band spectral energy distributions fully confirm this picture, and a synchrotron inverse Compton model allows us to derive the physical parameters (intrinsic power, magnetic field, etc.) of our sources. Combining our results with those obtained by BeppoSAX on BL Lacs covering a wide range of synchrotron peak frequency, ν peak , we confirm and clarify the dependence of the X-ray spectral index on ν peak originally found in ROSAT data. 相似文献
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D. A. Schwartz D. E. Harris H. Landt A. Siemiginowska H. L. Marshall J. M. Gelbord E. S. Perlman M. Georganopoulos M. Birkinshaw D. M. Worrall C. C. Cheung L. Stawarz S. G. Jorstad A. P. Marscher Y. Uchiyama C. M. Urry 《Astrophysics and Space Science》2007,311(1-3):341-345
We present a Chandra image of the quasar, jet, and lobes of PKS 1354+195 (=4C 19.44). The radio jet is 18 arcsec long, and appears to be very
straight. The length gives many independent spatial resolution elements in the Chandra image while the straightness implies that the geometrical factors are constant along the jet although their values are uncertain.
We also have 4 frequency radio images with half to one arcsecond angular resolution, and use HST and Spitzer data to study
the broad band spectral energy distributions. The X-ray and radio spectra are both consistent with a spectrum f
ν
∝
ν
−0.7 for the integrated jet. Using that spectral index, the model of inverse Compton scattering of electrons on the cosmic microwave
background (IC/CMB) gives magnetic field strengths and Doppler factors that are relatively constant along the jet. Extended
X-ray emission is evident in the direction of the otherwise unseen counter-jet. X-ray emission continues past the radio jet
to the South, and is detected within both the southern and northern radio lobes. 相似文献