Rural livelihoods and climate variability in Ningxia, Northwest China     

Yue Li  D. Conway  Yanjuan Wu  Qingzhu Gao  S. Rothausen  Wei Xiong  Hui Ju  Erda Lin 《Climatic change》2013,119(3-4):891-904

This study addresses the role of climate variability in the livelihoods of agricultural communities in Ningxia, Northwest China. Data sources comprise meteorological observations and official reports, complemented by questionnaires and focus group discussions designed around a livelihoods framework. Sample villages were located in three different agricultural systems: irrigated, mixed irrigated/grazing, and rainfed. Much of Ningxia is perennially dry and this is a significant limiting factor to agricultural production in the region, exacerbated by drought and buffered by irrigation mainly supplied from the Yellow River. Climate observations show stable temperatures from the 1950s to the 1980s followed by a positive trend (0.38°C/decade 1961–2010). Precipitation shows very modest trends and low decadal variability. Recent climate variability, particularly a drought from 2004–2006, was perceived to have had a significant effect on agricultural production and access to water, but it was not the only challenge respondents had faced. Susceptibility to drought was higher in the mixed irrigated and grazing and rainfed areas, due to farmers’ greater exposure to climatic hazards and because a higher proportion of their income originated from farming activities. Respondents were using a wide range of measures to retain and enhance soil moisture and maintain agricultural production. The discussion examines challenges in disentangling the role of climate within rapidly changing livelihood systems.  相似文献   

An imaging survey of a uniform sample of brightest cluster galaxies and intracluster light     

Parimal Patel  S. Maddox  Frazer R. Pearce  A. Aragón-Salamanca  E. Conway 《Monthly notices of the Royal Astronomical Society》2006,370(2):851-883

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The optical jet in 3C 31 on 15 arcsec scales     

J. H. Croston  M. Birkinshaw  E. Conway  R. L. Davies 《Monthly notices of the Royal Astronomical Society》2003,339(1):82-86

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Not developed yet? Alternative ways to include locations without changes in land use change models     

Tenley M. Conway  Christopher C. Wellen 《International journal of geographical information science》2013,27(10):1613-1631

Biogeographers have developed a new generation of statistical models called presence-only models, which require no data concerning the absence of a species and do not assume that the absence of a species indicates habitat unsuitability. Both characteristics are especially useful when modeling a species that is actively spreading across a landscape. Although urban expansion is sometimes equated to an invading species, the applicability of presence-only models has not yet been explored when modeling urban growth. This article compares predictions of urban growth using a presence-only model (ecological niche factor analysis) and a more traditional presence–absence model (logistic regression). An additional model used pseudo-absence sites, from the presence-only model output, as input into the presence–absence model. The models were applied to New Jersey's Barnegat Bay Watershed. Overall, the traditional presence–absence model performed the best, although the presence-only model was sufficiently similar to warrant further exploration of presence-only models when no reliable absence data (i.e., locations where no conversion occurred) exists. However, due to data-formatting requirements of the presence-only model, it is difficult to accommodate data pertaining to administrative boundaries, which are inherently Boolean. Finally, the output based on the pseudo-absence approach overpredicted urban conversion when compared to the other approaches.  相似文献   

Getting Charlie off the MTA: a multiobjective optimization method to account for cost constraints in public transit accessibility metrics     

Matthew Wigginton Conway  Anson F. Stewart 《International journal of geographical information science》2019,33(9):1759-1787

Most analyses of accessibility by public transit have focused on travel time and not considered the cost of transit fares. It is difficult to include fares in shortest-path algorithms because fares are often path-dependent. When fare policies allow discounted transfers, for example, the fare for a given journey segment depends on characteristics of previous journey segments. Existing methods to characterize tradeoffs between travel time and monetary cost objectives do not scale well to complex networks, or they rely on approximations. Additionally, they often require assumed values of time, which may be problematic for evaluating the equity of service provision. We propose a new method that allows us to find Pareto sets of paths, jointly minimizing fare and travel time. Using a case study in greater Boston, Massachusetts, USA, we test the algorithm’s performance as part of an interactive web application for computing accessibility metrics. Potential extensions for journey planning and route choice models are also discussed.  相似文献   

Future cereal production in China: The interaction of climate change,water availability and socio-economic scenarios   总被引：4，自引：0，他引：4  

Xiong Wei  Conway Declan  Lin Erda  Xu Yinlong  Ju Hui  Jiang Jinhe  Holman Ian  Li Yan 《Global Environmental Change》2009,19(1):34-44

Food production in China is a fundamental component of the national economy and driver of agricultural policy. Sustaining and increasing output to meet growing demand faces significant challenges including climate change, increasing population, agricultural land loss and competing demands for water. Recent warming in China is projected to accelerate by climate models with associated changes in precipitation and frequency of extreme events. How changes in cereal production and water availability due to climate change will interact with other socio-economic pressures is poorly understood. By linking crop and water simulation models and two scenarios of climate (derived from the Regional Climate Model PRECIS) and socio-economic change (downscaled from IPCC SRES A2 and B2) we demonstrate that by the 2040s the absolute effects of climate change are relatively modest. The interactive effects of other drivers are negative, leading to decreases in total production of ?18% (A2) and ?9% (B2). Outcomes are highly dependent on climate scenario, socio-economic development pathway and the effects of CO₂ fertilization on crop yields which may almost totally offset the decreases in production. We find that water availability plays a significant limiting role on future cereal production, due to the combined effects of higher crop water requirements (due to climate change) and increasing demand for non-agricultural use of water (due to socio-economic development). Without adaptation, per capita cereal production falls in all cases, by up to 40% of the current baseline.By simulating the effects of three adaptation scenarios we show that for these future scenarios China is able to maintain per capita cereal production, given reasonable assumptions about policies on land and water management and progress in agricultural technology. Our results are optimistic because PRECIS simulates much wetter conditions than a multi-model average, the CO₂ crop yield response function is highly uncertain and the effects of extreme events on crop growth and water availability are likely to be underestimated.  相似文献   

Progress in global environmental change     

W. Neil Adger  Katrina Brown  Declan Conway 《Global Environmental Change》2010,20(4):547-549

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Variations in the column-average dry-air mole fractions of CO2 in the vicinity of St. Petersburg     

A. V. Rakitin  A. V. Poberovskii  Yu. M. Timofeev  M. V. Makarova  T. J. Conway 《Izvestiya Atmospheric and Oceanic Physics》2013,49(3):271-275

The results obtained from ground-based spectroscopic measurements of column-average dry-air mole fractions of CO₂ in the atmosphere over the St. Petersburg region are given for the period April 2009–October 2011 (～900 measurement runs, 151 measurement days). These results show significant variations in the CO₂ mixing ratio in the atmosphere over the St. Petersburg region. The minimum value of this mixing ratio (373.1 ppm) was observed on April 27, 2011, and its maximum value (420.8 ppm) was observed on February 10, 2010. The typical seasonal behavior of the CO₂ mixing ratio with its summer minimum was observed in 2009. In July 2010 and 2011, the values of the CO₂ mixing ratio increased apparently due to high air temperatures. In 2010 an additional contribution to this increase in the CO₂ mixing ratio could have been made by strong natural fires.  相似文献   

Les radiotélescopes: Émile-Jacques Blum: Presses Universitaires de France. 1972. 128 pp. 3.95 F.fr.     

R.G Conway 《Planetary and Space Science》1973,21(7):1271-1272

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Atmospheric CO2 variations at Barrow,Alaska, 1973–1982     

Peterson  James T.  Komhyr  W. D.  Waterman  L. S.  Gammon  R. H.  Thoning  K. W.  Conway  T. J. 《Journal of Atmospheric Chemistry》1986,4(4):491-510

The first 10 years (1973–1982) of atmospheric CO₂ measurements at Barrow, Alaska, by the NOAA/GMCC program are described. The paper updates and extends the Barrow CO₂ record presented in Tellus (1982). The data are given in final form, based on recent calibrations of the Scripps Institution of Oceanography, with selected values identified as representative of large, spacescale conditions. Analyses of the data show: (1) a long-term CO₂ average increase of 1.3 ppm per year, but with large year-to-year variations in that growth rate; (2) a suggestion, not statistically significant, of a secular increase in the amplitude of the annual cycle, presumably a reflection of global-scale biospheric variability; and (3) good absolute agreement between the Barrow results and those from four neighboring high latitude sites between 50 and 82°N.  相似文献