Trends in Spatial Statistics     

Trisalyn A. Nelson 《The Professional geographer》2013,65(1):83-94

With many leading spatial analysts nearing retirement, reflection on the discipline becomes beneficial. To capture some of their collective perspective, fifty-eight researchers were surveyed on key spatial analysis developments, future challenges, and essential readings for newcomers. Geographic information systems (GIS), new data sources, improved understanding of spatial autocorrelation, spatially local methods, and the spread of spatial analysis beyond geography featured prominently among the twenty-four respondents. Future challenges included overcoming methodological limitations and retaining spatial analysis within geography. Twelve books highlighted by respondents are also summarized. Finally, a synthesis and some thoughts based on survey results are presented.  相似文献   

The Evolution and Research Trends of Port Geography     

Adolf K. Y. Ng 《The Professional geographer》2013,65(1):65-86

Despite the long existence of port geography research, there has been no systematic investigation on its evolution and research trends. Hence, through investigating 155 port geography articles featured in geography journals between 1956 and 2011, this article studied the evolution and research trends of port geography. The article argues that port geography had gradually evolved from a secondary and encyclopedic subdiscipline within transport and human geographies to a primary and specialized one. Such a trend had blurred its “geographicalness,” however, with port geography moving toward the more applied and interdisciplinary transportation. The article also indicates that further research would be required to understand the communication between port geography and other disciplines, as well as philosophical and epistemological issues.  相似文献   

Spatio-temporal analysis of tree height in a young cork oak plantation     

L. Sedda  P.M. Atkinson  M.R. Filigheddu  G. Cotzia  S. Dettori 《International journal of geographical information science》2013,27(7):1083-1096

Cork oak is one of the most valuable natural forest genera in the Mediterranean basin. Modelling cork oak growth has been a challenge for foresters in recent years because of strong site and genetic influences, below-ground competition, management regimes and age effects. Because cork productivity is related to forest height, which is, in turn, related directly with site characteristics, an increase in the accuracy of height prediction implies improved productivity estimation. A Bayesian maximum entropy (BME) geostatistical model was applied to characterize the space–time pattern of height of young cork oak in a forest stand from central Sardinia in the years 2000, 2002, 2003, 2006 and 2008. Cork oak height maps were produced for each of the 5 years. The main goals were to analyse and interpret through time (i) the changes in spatial correlation and (ii) the changes in spatial distribution of cork oak height. The plantation was characterized by an increasing spatial dependence through time, whereas the temporal range was 2 years. Cork oak height was significantly correlated with wind speed (reduced by a neighbouring forest) in all the years implying a single trend. The correlations were larger for 2006 and 2008 than for previous years. Three other environmental variables (shade, elevation and slope) were less significant and their influence restricted to 2 years only. This research has several implications for the management of cork oak in the young phase.  相似文献   

Hydro-climatic trends in the Abay/Upper Blue Nile basin,Ethiopia     

《Physics and Chemistry of the Earth》2013

Trends of the three hydro-meteorological variables precipitation, temperature and stream flow, represented by 13, 12, and 9 gauging stations, respectively, within the Abay/Upper Blue Nile basin have been studied to support water management in the region. The Trends were evaluated over different time periods depending on data availability at the stations. The statistical Mann–Kendall and Pettitt tests have been used to assess trends and change points respectively. The tests have been applied to mean annual, monthly, seasonal, 1- and 7-days annual minimum and maximum values for streamflow, while mean annual, monthly and seasonal timescales were applied to meteorological variables. The results are heterogeneous and depict statistically significant increasing/decreasing trends. Besides, it showed significant abrupt change of point upward/downward shift for streamflow and temperature time series. However, precipitation time series did not show any statistically significant trends in mean annual and seasonal scales across the examined stations.Increasing trends in temperature at different weather stations for the mean annual, rainy, dry and small rainy seasons are apparent. The mean temperature at Bahir Dar – typical station in the Lake Tana sub basin, has been increasing at the rate of about 0.5 °C/decade, 0.3 °C/decade in rainy season (June–September), 0.6 °C/decade in small rainy season (March–May), and 0.6 °C/decade in dry season (October–February). Other stations in the Abay/Upper Blue Nile show comparable results. Overall it is found that trends and change point times varied considerably across the stations and catchment to catchment. Identified significant trends can help to make better planning decisions for water management. However, the cause attributes to the observed changes in hydro-meteorological variables need further research. In particular the combined effects of land use/land cover change and climate variability on streamflow of Abay/Blue Nile basin and its tributaries needs to be understood better.  相似文献   

The contrasted evolution of high and low flows and precipitation indices in the Duero basin (Spain)     

Enrique Morán-Tejeda  Juan Ignacio López-Moreno  Sergio M. Vicente-Serrano  Jorge Lorenzo-Lacruz  Antonio Ceballos-Barbancho 《水文科学杂志》2013,58(4):591-611

Abstract

Trends in high and low flows are valuable indicators of hydrological change because they highlight changes in various parts of the frequency distribution of streamflow series. This enables improved assessment of water availability in regions with high seasonal and inter-annual variability. There has been a substantial reduction in water resources in the Duero basin (Iberian Peninsula, Spain) and other areas of the Mediterranean region during the last 50 years, and this is likely to continue because of climate change. In this study, we investigated the evolution and trends in high and low flows in the Spanish part of the Duero basin, and in equivalent or closely-related precipitation indices for the period 1961–2005. The results showed a general trend of decrease in the frequency and magnitude of high flows throughout most of the basin. Moreover, the number of days with low flows significantly increased over this period. No clear relationship was evident between the evolution of high/low flows and changes in the distribution frequencies of the precipitation series. In contrast to what was expected, the number of days with heavy precipitation and the mean annual precipitation did not show significant trends across the basin, and the number of days without rainfall decreased slightly. The divergence between precipitation and runoff evolution was more accentuated in spring and summer. In the absence of trends in precipitation, it is possible that reforestation processes in the region, and increasing temperatures in recent decades, could be related to the decreasing frequency of high flows and the increasing frequency of low flows.

Editor Z.W. Kundzewicz; Associate editor S. Grimaldi

Citation Morán-Tejeda, E., López-Moreno, J.I., Vicente-Serrano, S.M., Lorenzo-Lacruz, J. and Ceballos-Barbancho, A., 2012. The contrasted evolution of high and low flows and precipitation indices in the Duero basin (Spain). Hydrological Sciences Journal, 57 (4), 591–611.  相似文献   

Discussion of “Neuro-fuzzy models employing wavelet analysis for suspended sediment concentration prediction in rivers”     

Robert J. Abrahart  Nick J. Mount 《水文科学杂志》2013,58(7):1325-1329

Citation Abrahart, R.J. & Mount, N.J. (2011) Discussion of “Neuro-fuzzy models employing wavelet analysis for suspended sediment concentration prediction in rivers by S.A. Mirgagheri et al. (2010, Hydrol. Sci. J. 55(7), 1175–1189).” Hydrol. Sci. J. 56(7), 1325–1329.  相似文献   

Analysis of trends of annual and seasonal precipitation from 1956 to 2000 in Guangdong Province,China     

Dedi Liu  Shenglian Guo  Xiaohong Chen  Quanxi Shao 《水文科学杂志》2013,58(2):358-369

Abstract

The trends of annual, seasonal and monthly precipitation in southern China (Guangdong Province) for the period 1956–2000 are investigated, based on the data from 186 high-quality gauging stations. Statistical tests, including Mann-Kendall rank test and wavelet analysis, are employed to determine whether the precipitation series exhibit any regular trend and periodicity. The results indicate that the annual precipitation has a slightly decreasing trend in central Guangdong and slight increasing trends in the eastern and western areas of the province. However, all the annual trends are not statistically significant at the 95% confidence level. The average precipitation increases in the dry season in central Guangdong, but decreases in the wet season, meaning that the precipitation becomes more evenly distributed within the year. Furthermore, the analysis of monthly precipitation suggests that the distribution of intra-annual precipitation changes over time. The results of wavelet analysis show prominent precipitation with periods ranging from 10 to 12 years in every sub-region in Guangdong Province. Comparing with the sunspot cycle (11-year), the annual precipitation in every sub-region in Guangdong province correlates with Sunspot Number with a 3-year lag. The findings in this paper will be useful for water resources management.

Editor Z.W. Kundzewicz; Associate editor Sheng Yue

Citation Dedi Liu, Shenglian Guo, Xiaohong Chen and Quanxi Shao, 2012. Analysis of trends of annual and seasonal precipitation from 1956 to 2000 in Guangdong Province, China. Hydrological Sciences Journal, 57 (2), 358–369.  相似文献   

Essai de définition     

G. CASTANY  J. MARGAT 《水文科学杂志》2013,58(1):74-81

Abstract

The apprehension and elaboration of hydrological maps in parallel with the development of hydrogeological maps render inevitable at first a clarification of terminology, besides an examination of the whole problem concerning the mapping of the data relating to water. It states theoretical (limits and validity of mapping in this property) and practical problems (methods, cooperation and distribution of work between using specialists and organizations).  相似文献   

Flooding in Fiji: findings from a 100-year historical series     

《水文科学杂志》2013,58(5):1004-1015

Abstract

Correspondence from a long-established sugar mill provided the opportunity to construct the longest flood series for a river in Fiji—the Ba River in northwest Viti Levu—from 1892 to 2002. Flood waters reached the mill floor every four years on average. Contrary to common lore, this study could detect no increase in the frequency of major floods over the course of the 20th century, despite intensification of land use and siltation of the river channel over that time. Large, slow-moving tropical cyclones situated northwest of the valley have generated large floods, but so too have tropical rainstorms. Major floods have occurred in months when the Southern Oscillation Index (SOI) was both negative and positive, suggesting that the SOI is a poor indicator of flood potential for the Ba River.  相似文献   

PCBs in Central Vietnam coastal lagoons: levels and trends in dynamic environments     

Giuliani S  Piazza R  Bellucci LG  Cu NH  Vecchiato M  Romano S  Mugnai C  Nhon DH  Frignani M 《Marine pollution bulletin》2011,62(5):1013-1024

PCBs were analysed in surficial sediments and selected sediment cores collected between 2002 and 2008 in Central Vietnam coastal lagoons. The aim was to determine contamination levels and trends, and to evaluate the effects of anthropogenic pressures and natural events. Samples were mostly fine-grained with low total PCB concentrations (0.367-44.7 μg kg⁻¹). Atmospheric transport and post depositional processes modify to some degree the fingerprint of PCB inputs to the environment favouring the predominance of 3, 4 and 5 chlorinated congeners. The similarity of congener distributions in contemporary surficial samples also suggests the presence of a unique source over the entire study area, probably connected to mobilisation and long range transports from land-based stocks. The removal of consistent sediment layers is hypothesised based on repeated samplings of the same area. Natural meteorological events (such as typhoons) are suspected to be responsible for these sediment losses.  相似文献