Study of the Impact of Urban Development on Surface Temperature Using Remote Sensing in Ho Chi Minh City,Southern Vietnam

Rapid urbanisation and industrialisation have resulted in sharp land cover changes. Urban change not only impacts on land cover but also on urban climate. Land surface and atmospheric modifications due to urbanisation generally lead to a modified thermal climate that is warmer than the surrounding, non-urbanised areas. In this research remote sensing technology was used to evaluate urban growth patterns and its thermal characteristics through mapping impervious surfaces and evaluating thermal infrared images. The case study was carried out in the northern part of Ho Chi Minh City, which has experienced accelerated urban development since the late 1980s. Landsat and Aster images were used to calculate variations in urban impervious surfaces from 1989 to 2006. Thermal bands were processed to obtain radiant surface temperatures for investigating the urban heat island effect associated with increasing impervious surfaces, both spatially and temporally. Impacts of urban development on surface temperature were shown by investigating the surface urban heat island effect intensity. The results show that the built-up area in the northern part of Ho Chi Minh City expanded by 6.5 times between 1989 and 2006. Urban development has altered the magnitude and pattern of the surface urban heat island, with the highest land surface temperature cores found in the industrial (greater than 45^oC) and urban areas (within 36^oC and 40^oC). In suburban and rural areas, where agricultural land still remains with full vegetation cover, the land surface temperature is usually lower. Using remote sensing, the impervious surface was extracted with overall accuracy and a Kappa coefficient for all three years greater than 96%, and the retrieved land surface temperatures with variations from in-situ measurements of less than 2^oC. The results presented here indicate that remote sensing can help to spatially monitor urban development and land surface temperature changes over the whole area and over a long period of time.     

Dynamics of Land Surface Temperature in Response to Land‐Use/Cover Change

In this study, we employed Geographical Information Systems and remote sensing techniques to investigate the impact of land‐use/cover change on land surface temperature (LST) in a rapidly urbanisation city, Kunming in south‐west China. Spatial patterns of LST and land use for 1992 and 2006 were derived from Landsat images to examine how LST responded to urban growth. Remote sensing indices were used to quantify land‐use types and employed as explanatory variables in LST modelling. The geographically weighted regression (GWR), a location dependent model, was performed to explore the influences of the spatially varied land‐use conditions on the LST patterns. Results revealed that rapid urbanisation in Kunming altered the local thermal environment, particularly in increasing the LST in the zone surrounding the urban core. Remote sensing indices demonstrated that water and vegetation played an important role in mitigating the urban heat island effect, while built‐up and barren land accounted for the increase in LST. The GWR improved the goodness‐of‐fit for LST modelling and provided insights into the spatially varied relationship between LST and land‐use conditions.     

Geographic information system‐based evaluation of spatial accessibility to maternal health facilities in Siaya County,Kenya

Maternal mortality is a major problem in middle‐income and low‐income countries, and the availability and accessibility of healthcare facilities offering safe delivery is important in averting maternal deaths. Siaya County, in Kenya, has one of the highest maternal mortality rates in the country—far more than the national average. This study aimed to evaluate geographic access to health facilities offering delivery services in Siaya County. A mixed‐methods approach incorporating geographic information system analysis and individual data from semi‐structured interviews was used to derive travel time maps to facilities using different travel scenarios: AccessMod5 and ArcGIS were used for these tasks. The derived maps were then linked to georeferenced household survey data in a multilevel logistic regression model in R to predict the probability of expectant women delivering in a health facility. Based on the derived travel times, 26 per cent (13,140) and 67 per cent (32,074) of the estimated 46,332 pregnant women could reach any facility within one and two hours, respectively, while walking with the percentage falling to seven per cent (3,415) and 20 per cent (8,845) when considering referral facilities. Motorised transport significantly increased coverage. The findings revealed that the predicted probability of a pregnant woman delivering in a health facility ranged between 0.14 and 0.86. Significant differences existed in access levels with transportation‐based interventions significantly increasing coverage. The derived maps can help health policy planners identify underserved areas and monitor future reductions in inequalities. This work has theoretical implications for conceptualising healthcare accessibility besides advancing the literature on mixed methodologies.     

Influence of meteorological conditions on the intensity and form of the urban heat island effect in Regina

This study investigates the influence of meteorological conditions on the intensity and spatial configuration of the urban heat island effect in Regina, Saskatchewan. A sample of 31 nocturnal heat island intensities measured via automobile surveys averages 3°C, with a maximum intensity reaching 7.5°C. On nights with clear skies and light winds, heat island morphology in Regina is characterized by a clearly defined cliff, plateau, and peak. Regression analysis reveals that heat island intensities are highly sensitive to changes in wind conditions, and relatively insensitive to changes in humidity and atmospheric pressure. However, when antecedent weather conditions preceding each heat island event are included in the analysis, cloud cover supersedes wind speed as a more important control on heat island intensity. Daytime and post‐sunset cloud cover explain 20 percent more variance in the ensuing nocturnal heat island intensities than do daytime and post‐sunset wind speeds. This result challenges the widely‐held notion that wind speed is a more important heat island control than sky cover. Cette étude se penche sur l'influence des conditions météorologiques sur l'intensité et la configuration spatiale de l'effet d'îlot thermique urbain à Régina, Saskatchewan. Un échantillon de 31 intensités d'îlots thermiques nocturnes prélevées par automobile atteint une moyenne de 3°C, avec une intensité maximale de 7,5°C. Par nuit claire et vent léger, la morphologie des îlots thermiques à Régina est nettement caractérisée par un courant ascentionnel, un palier et une crête. L'analyse de régression révèle que les intensités d'îlots thermiques sont très sensibles aux changements de vents coincidents, et relativement insensibles aux changements d'humidité et de pression atmosphérique. Cependant, quand les conditions atmosphériques précédant chaque effet d'îlot thermique sont prises en considération, la couverture nuageuse supplante la vitesse du vent comme contrôle majeur de l'intensité. Quand on compare couverture nuageuse et vitesse du vent pendant la journée et après le coucher du soleil, la valeur explicative de la première est de 20 pour cent supérieure à celle de la dernière en ce qui concerne la variation d'intensité dans les îlots thermiques nocturnes qui s'ensuivent. Ce résultat remet en question la ‘conviction’ que dans le contrôle des îlots thermiques, la vitesse du vent est plus importante que la couverture nuageuse.     

Population Estimation Using Landsat Enhanced Thematic Mapper Imagery

An assessment of two groups of approaches for estimating urban population with remote-sensing information is presented in this article. These approaches, zonal and pixel-based models, are applied to Landsat Enhanced Thematic Mapper images of a portion of Columbus, Ohio , to generate population estimates. The zonal approach uses impervious surface fraction, spectral radiance, and land-use/land-cover classification to derive population estimates. The pixel-based approach uses impervious surface fraction and spectral radiance to estimate the population of residential areas. To assess robustness, these models were applied to Dayton, Ohio . A comparative study indicates that the models generated promising results in estimating regional population counts. However, zonal regression with spectral radiance produced large errors (76%) for census block groups, whereas other models gave significantly better estimation accuracy. Comparing the performance of the indicators, impervious surface fraction is competitive, and slightly but consistently better than land-use classification. In comparison with traditional zonal approaches, pixel-based models give somewhat better estimation accuracy.     

Beyond Kyoto? Media Representation of an Environmental Issue

Human‐induced climatic change, and particularly the enhanced greenhouse effect, became significant environmental issues in the 1990s. They were given prominent coverage in the Australian media at the time of the Third Conference of the Parties to the Climate Convention (COP3) in Kyoto in 1997, when Australia obtained permission for an 8 per cent increase in its greenhouse gas emissions by 2012. Meanwhile, other major emitters of greenhouse gases were accepting targets of significantly reduced emissions. Given the controversy associated with this, it might have been expected that the Australian media's coverage of COP4 in Buenos Aires, only 11 months later, would have been extensive. This was not the case. Analysis of seven Australian newspapers shows that, with the exception of an alternative weekly newspaper, the coverage of COP4 was an example of ‘embodiment’ (the uncritical acceptance of certain assumptions and practices) and ‘distanciation’ (the separation of cause and effect in regard to an issue).     

The Age of Environmental Impasse? Globalization and Enviromental Transformation of Metropolitan Cities

Metropolitan cities are undergoing a major spatial and environmental transformation. The proliferation of business districts, corporate headquarters and international hotels is prompting a massive verticalization and densification of land use, which is affecting the urban environment and infrastructure in a number of ways. Nowhere are urban environmental pressures so accentuated as in Third World metropolitan cities. Here the rush to gain a competitive edge in the global economy, in order to attract multinational firms and become a ‘global city’, is leading to an inconsistent urban policy framework in which development policies frequently clash with environmental policies. This article explores the environmental complexity of Third World metropolitan cities, focusing on the cases of Beijing and São Paulo. After a conceptual review of the relationship between globalization, cities and urban environmental problems, it examines how globalization is prompting spatial and environmental transformations in both cities; looks at the dichotomy between development policies and environmental policies by analysing the instruments in place; and investigates the role of globalization vis‐à‐vis urban sustainability issues.     

Some great railway enterprises

An investigation is made into the effect of the urban area on the microclimate of Glasgow, using data gathered by a series of mobile traverses. The study showed a maximum “heat‐island” to occur under clear skies, light winds and anticyclonic conditions. A cellular pattern of temperatures was also identified, it is suggested that anthropogenic heat may be the causal factor.     

The Colonial Sinews of Imperial Power: The Political Economy of Jamaican Taxation, 1768–1838

This article uses a new data-set to calculate the ‘political economy’ or nature and purpose of taxation and spending in Jamaica between 1768 and 1839. It argues that these levels increased considerably, both in absolute terms and relative to the size of the population and economy of the island, and that the assembly raised taxes mainly to protect the white elite and the plantation economy against slave revolts and foreign invasion. Although the balance of spending shifted after Emancipation in 1834, the purpose did not, since military spending was simply redirected to subsidise policing and the cost of public order. Depending on how the national income or gross domestic product of the island is calculated, levels of taxation rose from 2 per cent in peacetime to about 4–6 per cent in wartime, peaking at 6–8 per cent in moments of crisis. White elites therefore made a significant contribution to the cost of their own defence, and to the wider projection of imperial power, and were willing to tolerate increasingly high levels of taxation because it was spent in ways that suited their interests. They thereby formed the colonial sinews of imperial power.     

Variabilité et fréquence des cycles de gel‐dégel dans la région de Québec, 1977–2006

Freeze‐thaw cycles are most common at the beginning or near the end of the winter season. These cycles have various effects on the ecosystems of Eastern Canada, affecting both biotic and abiotic components of temperate cold environments. Using air temperature minima and maxima from four meteorological stations close to Québec City, we determined the frequency of daily freeze‐thaw cycles for the last 30 years. The results show no significant increase in the number of freeze‐thaw cycles despite a small increase in air temperature. Polynomial curves describing the relationship between mean air temperatures and the number of freeze‐thaw cycles were calculated. Based on these equations and anticipating a climate change scenario, we projected future freeze‐thaw cycles. Assuming a 5 °C increase in mean air temperatures by 2100, we estimated that the number of days with a freeze‐thaw cycle could increase by approximately 20 days per winter. The increase in the number of such cycles will be concentrated during the coldest months of the winter (January and February).     

Whose Wealth Is It Anyway? Mozambique's Outstanding Economic Growth with Worsening Rural Poverty

Despite rapid economic growth and massive inflows of aid, rural poverty in Mozambique is worsening. Agricultural production and productivity have not increased in the last decade. Use of chemical fertilizers and other modern technology is at a low level and decreasing. The present development model emphasizes that the role of government and donors is to provide human capital and infrastructure, while the private sector is responsible for economic development and ending poverty. The most recent national surveys confirm what is being seen elsewhere in Africa — that this non‐interventionist strategy does not raise agricultural productivity or reduce poverty. While 80 per cent of Mozambique's population is engaged in agriculture, this sector contributes only 20 per cent of GDP. This suggests that investments in agriculture are likely to generate pro‐poor growth, both to rural and urban dwellers. This policy failure is increasingly recognized, but donors and government have invested too much political capital in the current policy to change easily.     

Environmental influences on skilled worker migration from Bangladesh to Canada

We conducted focus groups in Toronto with 44 recent skilled worker immigrants from Bangladesh to explore whether their decisions to migrate to Canada may have been influenced by environmental problems. Previous research has documented how floods, cyclones, droughts, and seasonal precipitation variations affect rural‐urban migration patterns within Bangladesh, and to its neighbours. Most participants had not experienced such environmental hazards, having lived in Dhaka prior to migrating. However, Dhaka's ongoing problems with air and water pollution, sanitation, lack of green space, and food adulteration were cited by 70% as being relevant considerations for the decision to migrate. The degree of influence varied considerably among participants. Roughly 16% said pollution was their primary motivation for leaving, household members having suffered from illnesses traceable to air pollution or poor sanitation. Another 54% stated that Dhaka's environmental problems were part of a wider range of quality‐of‐life concerns that had some influence on their decision. The findings suggest that current migration to Canada is not connected with environmental migration that takes place within Bangladesh, but that urban environmental problems combined with other social, economic, and political factors can help drive migration.     

The effects of ageing and urbanisation on China’s future rural and urban populations

This paper estimates China’s future population and labour force by developing a novel forecasting model for population. It combines information about age-specific parameters on fertility and mortality for both rural and urban areas using information about rural–urban migration and the transformation of rural areas into urban ones. This model takes into account the effects of urbanisation on changes in the age structure of the Chinese population; and provides separate projections on the rural and urban populations. Our findings show that (i) the shares of people aged 65 and over, in China’s rural and urban populations, will double between 2010 and 2030; this implies that the ageing problem in rural areas will continue to be more serious than in urban areas; (ii) the rural labour force will shrink by 45 per cent, between 2010 and 2030, while the urban labour force will grow by 34 per cent; and (iii) China’s urbanisation rate will increase to 71 per cent by 2030.     

OUT-MIGRATION FROM MATLAB—A RURAL AREA OF BANGLADESH

Rural landlessness and pauperisation are ongoing processes in Bangladesh, forcing people to migrate to other areas or countries in search of a livelihood. The study estimates levels of and differentials in out-migration of adult Bangladeshis, and examines reasons for migration and place of destination, using longitudinally collected migration data in the International Centre for Diarrhoeal Disease Research, Bangladesh's (ICDDR,B's) Matlab surveillance area during the periods 1997–1999 and 2006–2008. The out-migration rate increased over time (48 per cent men versus 28 per cent women). Men migrated primarily for economic reasons (73–76 per cent), and women, for familial reasons (77–78 per cent). The younger, educated and well-off were more likely to migrate to urban areas and foreign countries than their older, less educated and poorer peers, who were more likely to migrate to other rural areas. Effective steps are needed to check rural-urban migration, and its numerous adverse consequences.     

Heat transport at boiling,near‐critical conditions

Two‐phase flow and near‐critical phenomena are likely to enhance energy transport in high‐temperature hydrothermal systems. We present a series of two‐dimensional simulations of two‐phase flow of pure water at near‐critical conditions. The results show that at near‐critical conditions, two‐phase convection can be more efficient in transporting energy than single‐phase convection. The highest heat fluxes are attained when two‐phase heat‐pipes form near the bottom boundary, recharging the root of the upflow zone and thereby enabling the formation of broad upflow regions. When the system becomes more vapor‐dominated, it loses this ability, upflow zones become narrower and the energy efficiency drops to more moderate values.     

VALUING ENVIRONMENTAL QUALITY: A SPACE‐BASED STRATEGY*

ABSTRACT This paper develops and applies a space‐based strategy for overcoming the general problem of deriving the implicit demand for nonmarket goods. It focuses specifically on evaluating one form of environmental quality, distance from Environmental Protection Agency designated environmental hazards, via the single‐family housing market in the Puget Sound region of Washington State. A spatial two‐stage hedonic price analysis is used to: (i) estimate the marginal implicit price of distance from air release sites, hazardous waste generators, hazardous waste handlers, superfund sites, and toxic release sites; and (ii) estimate a series of implicit demand functions describing the relationship between the price of distance and the quantity consumed. The analysis, which represents an important step forward in the valuation of environmental quality, reveals that the information needed to identify second‐stage demand functions is hidden right in plain sight—hanging in the aether of the regional housing market.     

Correlating Vegetation,Water Use,and Surface Temperature in a Semiarid City: A Multiscale Analysis of the Impacts of Irrigation by Single‐Family Residences

Urban heat islands (UHIs) and the vegetation that mitigates them vary across space and time, but little research has investigated this coupled natural–human system using both spatial and temporal analyses. Focusing on semiarid, water‐scarce Tucson, Arizona, we examined whether outdoor water use by residents of single‐family homes (a practice that uses close to half of residential water supplies) contributes to urban “greenness” and the mitigation of UHI effects. Specifically, we investigated how different types of residential development mediate vegetation–water use–temperature interactions. Our data sets include Landsat‐derived normalized difference vegetation index (NDVI) and surface temperatures, parcel‐level zoning and assessor data, and residential water use records at the quarter section level (0.63 km²). We analyzed these data at multiple spatial and temporal scales. Spatial analysis results demonstrate that cooling from vegetative evapotranspiration is mediated by development factors as well as by topography and wind patterns. Findings also suggest that outdoor water use aside from irrigation, particularly the use of swimming pools, promotes cooling without elevating the NDVI. Temporal analysis reveal that most residential areas maintained or increased greenness despite declining 1995–2008 water use due most likely to long‐term regional climate cycles. Only high‐density developments with little undeveloped ground cover and few natural drainage channels exhibit a strong relationship between household water use and NDVI trends. These results suggest that the preservation of natural drainage channels and limitation of impervious surfaces, as well as the siting of development in naturally cooled microclimates, may be sustainable strategies for UHI mitigation in water‐scarce regions. Análisis multi‐escalar de los impactos de riego en residencias unifamiliares: la correlación entre la vegetación, el uso del agua y la temperatura superficial en un área urbana semiárida Las islas de calor urbano (urban heat islands‐UHIs) y las áreas con vegetación que ayudan a mitigarlas varían en su distribución especial y temporal. Sin embargo, existe relativamente poca investigación dedicada al análisis espacio‐temporal de este sistema acoplado humano‐ambiental urbano. El artículo examina la medida en la cual el uso de agua al aire libre por parte de residentes de viviendas unifamiliares (practica que consume mas de la mitad de los recursos hídricos) contribuye al “verdor” de áreas urbanas y a la mitigación de los efectos de las UHs. El área de estudio es Tucson, Arizona, una ciudad ubicada en un ambiente semiárido que sufre de escasez hídrica. En términos más concretos, los autores investigan cómo los diferentes tipos de desarrollos urbanos residenciales sirven de mediadores en las interacciones entre la vegetación, la temperatura y el uso del agua. Como datos se utilizaron índices de vegetación (Normalized difference vegetation index‐NDVI) y temperaturas superficiales derivados de imágenes Landsat. Así mismo se usaron datos catastrales a nivel de parcela de zonificación, y registros de uso residencial de agua a nivel de cuarto de sección (quarter‐section) (0,63 km2). Los datos fueron analizados a múltiples escalas espaciales y temporales. Los resultados de análisis espacial demuestran que el enfriamiento de la evapotranspiración vegetal está influenciado por los factores de desarrollo urbano residencial así como por los patrones topográficos y climáticos (viento). Los resultados también sugieren que los usos de agua al aire libre, aparte de riego, en particular el uso de las piscinas (o albercas), promueven el enfriamiento sin elevar el valor del NDVI. El análisis temporal revela que la mayoría de zonas residenciales mantuvieron o aumentaron el ‘verdor’ a pesar de la disminución del uso del agua entre 1995 y 2008, debido probablemente a los ciclos climáticos regionales de largo plazo. Únicamente las zonas urbanas de alta densidad con escasas áreas verdes y pocos canales naturales de drenaje muestran una fuerte relación entre el uso del agua residencial y las tendencias del NDVI. Estos resultados sugieren que la preservación de los canales de drenaje natural y la reducción de superficies impermeables, así como el emplazamiento del desarrollo urbano en áreas con microclimas naturalmente más fríos, pueden ser estrategias sostenibles para la mitigación de UHIs en regiones con escasez de agua. 城市热岛与可缓解其效应的植被均随时间和空间变化,但鲜有研究从时空分析视角关注这一自然‐人文耦合系统。本文聚焦于半干旱、缺水的亚利桑那州图森市,主要调查独户家庭户外用水（其用水量大约是住宅供应水量的一半）是否对城市“绿化”和缓解城市热岛效应作出贡献。特别地,我们调查不同类型住宅开发是如何调节植物‐用水‐温度间的相互作用。数据集包括从美国陆地资源卫星获得的归一化植被指数（NDVI）和地表温度,地块区划和评估数据, 约160英亩（0.63 km²）用地面积的住户用水记录。我们从时空多尺度视角对这些数据进行了分析。 空间分析结果表明,植被蒸散作用导致的降温不仅受开发因素也受地形和风模式的调节。同时也发现：包括灌溉的户外用水,尤其是泳池用水,在促进地表降温时并未促使归一化植被指数（NDVI）提高。时间分析揭示,大多数居住区即使在1995–2008用水减少的情况下仍保持和增加“绿化”,最可能归因于长期的区域气候循环。只是在植被覆盖和自然排水系统均很少的高密度开发地区,家庭用水与NDVI趋势上显示出强相关性。这些结果昭示保留自然排水系统和限制不透水地表,以及在具有自然降温作用的微气候上选址发展区,或许是缺水地区缓解热岛效应的可持续策略。     

Estimating the Variability of Active‐Layer Thaw Depth in Two Physiographic Regions of Northern Alaska

The active layer is the zone above permafrost that experiences seasonal freeze and thaw. Active‐layer thickness varies annually in response to air and surface temperature, and generally decreases poleward. Substantially less is known about thaw variability across small lateral distances in response to topography, parent material, vegetation, and subsurface hydrology. A graduated steel rod was used to measure the 1998 end‐of‐season thaw depth across several transects. A balanced hierarchical sampling design was used to estimate the contribution to total variance in active‐layer depth at separating distances of 1, 3, 9, 27, and 100 meters. A second sampling scheme was used to examine variation at shorter distances of 0.3 and 0.1 meter. This seven‐stage sample design was applied to two sites in the Arctic Foothills physiographic province, and four sites on the Arctic Coastal Plain province in northern Alaska. The spatial variability for each site was determined using ANOVA and variogram methods to compare intersite and inter‐province variation. Spatial variation in thaw depth was different in the Foothills and Coastal Plain sites. A greater percentage of the total variance occurs at short lag distances (0–3 meters) at the Foothills sites, presumably reflecting the influence of frost boils and tussock vegetation on ground heat flow. In contrast, thaw variation at the Coastal Plain sites occurs at distances exceeding 10 meters, and is attributed to the influence of well‐developed networks of ice‐wedge polygons and the presence of drained thaw‐lake basins. This information was used to determine an ongoing sampling scheme for each site and to assess the suitability of each method of analysis.     

Correlation between dental occlusal wear and approximal facet length

The aim of this paper is to examine the relationship between occlusal surface wear and approximal facet length in a North American archaeological sample of modern human hunter–gatherers (n = 111) and agriculturalists (n = 123). First maxillary molars (M¹) were selected. The approximal wear facet was measured on the mesial surface of each M¹ at the widest breadth using needle tipped digital callipers. Digital images were taken of the occlusal surface and wear was recorded as the percentage of dentine exposed to the total occlusal surface. Independent age estimate was based on age‐related changes, (pubic symphysis and auricular surface). Results show the hunter–gatherers had a significantly faster rate of wear on both tooth surfaces compared to the agriculturalists in each of the four age groups. Both lifeway groups showed a positive correlation between the two tooth surfaces during the early stages of tooth wear (less than 25% occlusal wear), where the percentage of occlusal wear and the length of the approximal facet increased at a similar rate. During the middle and final stages of tooth wear (occlusal wear greater than 35%) there was a strong negative correlation between the two surfaces in both groups. It is suggested this pattern is due to the shape and function of the M¹. Both correlations were more extreme in the hunter–gatherers than the agriculturalists. When the per cent of occlusal wear exceeded 35% the length of the approximal facet started to decrease, and it is therefore recommended studies that include approximal wear exclude molars with heavy occlusal wear. Copyright © 2010 John Wiley & Sons, Ltd.