Mapping regional land cover and land use change using MODIS time series

Coarse resolution satellite observations of the Earth provide critical data in support of land cover and land use monitoring at regional to global scales. This dissertation focuses on methodology and dataset development that exploit multi-temporal data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to improve current information related to regional forest cover change and urban extent. In the first element of this dissertation, I develop a novel distance metric-based change detection method to map annual forest cover change at 500m spatial resolution. Evaluations based on a global network of test sites and two regional case studies in Brazil and the United States demonstrate the efficiency and effectiveness of this methodology, where estimated changes in forest cover are comparable to reference data derived from higher spatial resolution data sources. In the second element of this dissertation, I develop methods to estimate fractional urban cover for temperate and tropical regions of China at 250m spatial resolution by fusing MODIS data with nighttime lights using the Random Forest regression algorithm. Assessment of results for 9 cities in Eastern, Central, and Southern China show good agreement between the estimated urban percentages from MODIS and reference urban percentages derived from higher resolution Landsat data. In the final element of this dissertation, I assess the capability of a new nighttime lights dataset from the Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) for urban mapping applications. This dataset provides higher spatial resolution and improved radiometric quality in nighttime lights observations relative to previous datasets. Analyses for a study area in the Yangtze River Delta in China show that this new source of data significantly improves representation of urban areas, and that fractional urban estimation based on DNB can be further improved by fusion with MODIS data. Overall, the research in this dissertation contributes new methods and understanding for remote sensing-based change detection methodologies. The results suggest that land cover change products from coarse spatial resolution sensors such as MODIS and VIIRS can benefit from regional optimization, and that urban extent mapping from nighttime lights should exploit complementary information from conventional visible and near infrared observations

A Satellite Assessment of the Urban Heat Island in Morocco

Urban ecosystems interact with surroundings via land cover changes and their subsequent impact on surface temperature. In emerging countries, large urban agglomerations often form around cities, and only few studies have evaluated their impact. This study carries out the first ever large-scale assessment of urban heat island (UHI) and reflects on its mitigation in Morocco.The analysis reveals a well-defined UHI in urban-areas built within vegetated lands and an urban heat sink (UHS) in urban-areas built within arid regions. Both UHI and UHS amplitudes are higher during day than nighttime, emphasizing vegetation physiological activity. We show a monotonic increase in UHI amplitude with urban-area size. However, unlike previous studies, our analysis shows that as urban-areas built in desert-like environments grow in size, the UHS gradually decreases to ultimately turn into an UHI. On average, cities built within vegetation are warmer than rural fringe by 1.51C during daytime. This suggests that daytime urban heating may exacerbate the potential climate warming. Our results also suggest that adapted trees constitute a natural cooling mechanism and should be part of urban heating mitigation in Morocco

Examining Urban Heat Island Effect and Its Public Health Implications with Remotely Sensed Data

The Urban heat island (UHI) as a byproduct of urbanization has long been studied utilizing remote sensing technologies. However, issues remain to be addressed. Land surface temperature (LST) as the indicator of surface UHI can be retrieved from remotely sensed data, but its accuracy is limited as existing studies neglect the neighboring effect. Further, while LST serves well as an indicator of surface thermal condition, it lacks the ability to reveal human heat stress, which is an environmental hazard that can seriously affect productivity, health or even survival of individuals. Although human heat stress has long been studied and can be quantified by many heat stress indices, it has never been explored across continuous spaces. Aiming to address these issues, the objectives of this research include: (1) taking into account the neighboring effect during LST retrieval using a moving window method; (2) revealing human heat stress with remotely sensed data; and (3) exploring the relationship between heat stress and land cover composition and configuration. My results indicate that the accuracy of LST estimation is improved when neighboring effect is considered. Discomfort index (DI) as an indicator of human heat stress can be retrieved from remotely sensed data, and its spatial distribution and relationship with land cover composition is largely affected by relative humidity. Spatial configuration of different land covers has an impact on DI, which may provide insights for policy makers and urban designers on mitigating hazardous environmental effect brought by urbanization

Land use and land cover changes in South East Asia: The effects of land transformations on biophysical variables in Indonesia

Au cours des dernières décennies, l'Indonésie a connu des transformations spectaculaires des terres avec une expansion des plantations de palmiers à huile au détriment des forêts tropicales. L'Indonésie est actuellement l'une des régions ayant le plus haut taux de transformation de la surface terrestre dans le monde à cause de l'expansion des plantations de palmiers à huile et d'autres agricultures qui remplacent les forêts à grande échelle. Comme la végétation est un modificateur du climat près du sol, ces transformations à grande échelle ont des impacts majeurs sur les variables biophysiques de surface telles que la température de surface, l'albédo, les indices de végétation (NDVI), sur le bilan énergétique de surface et le partitionnement énergétique. Ce travail de thèse vise à quantifier les impacts des changements d’usage des terres en Indonésie sur les variables biophysiques de surface. Pour évaluer ces changements à l'échelle régionale, des données de télédétection sont nécessaires. Étant une variable clé de nombreuses fonctions écologiques, la température de surface (LST) est directement affectée par les changements de la couverture terrestre. Nous avons analysé la LST à partir de la bande thermique d'une image Landsat et produit une carte de température de surface avec une haute résolution (30m) pour les basses terres de la province de Jambi à Sumatra (Indonésie), une région qui a subi de grandes transformations au cours des dernières décennies. La comparaison des LST, albédo, NDVI et évapotranspiration (ET) entre sept différents types de couverture terrestre (forêts, zones urbaines, terres incultes, plantations de palmiers à huile jeunes et matures, plantations d'acacias et de caoutchouc) montre que les forêts ont des températures de surface inférieures à celles des autres types de couvert végétal, ce qui indique un effet de réchauffement local après la conversion des forêts vers des plantations. Les différences de LST atteignaient 10,1 ± 2,6 ºC (moyenne ± écart-type) entre les forêts et les terres déforestées. Les différences de températures de surface s'expliquent par un effet de refroidissement évaporatif des forêts, qui compense l'effet de réchauffement de l'albédo. Basé sur des différences observées dans les variables biophysiques entre les plantations de palmiers à huile jeunes et matures, nous avons analysé trois images Landsat couvrant une chronoséquence de plantations de palmiers à huile pour étudier la dynamique des variables biophysiques de surface pendant le cycle de rotation de 20-25 ans des plantations de palmiers à huile. Nos résultats montrent que les différences entre les plantations de palmiers à huile à différents stades du cycle de rotation du palmier à huile se reflètent dans les différences du bilan énergétique de surface, du partitionnement énergétique et des variables biophysiques. Au cours du cycle de rotation des plantations de palmiers à huile, les différences de température à la surface diminuent graduellement et se rapprochent de zéro autour du stade mature de la plantation de palmiers à huile de 10 ans. Parallèlement, le NDVI augmente et l'albédo diminue à proximité des valeurs typiques des forêts. Le bilan énergétique de surface et le partitionnement énergétique montrent des tendances de développement liés aux variables biophysiques et à l'âge des plantations de palmiers à huile. Les nouvelles plantations et les jeunes plantations (<5 ans) ont un rayonnement net plus faible que les plantations de palmiers à huile matures, mais ont des températures de surface plus élevées que les plantations de palmiers à huile matures. Les changements dans les variables biophysiques, le bilan énergétique et la répartition de l'énergie au cours du cycle d’une rotation du palmier à huile peuvent s'expliquer par l'effet de refroidissement évaporatif précédemment identifié dans les forêts, qui compense l'effet de réchauffement de l'albédo. L'un des principaux déterminants de ce mécanisme est la couverture végétale au cours des différentes phases du cycle de rotation du palmier à huile. Le NDVI en tant qu'indicateur du couvert végétal a montré une relation inverse cohérente avec LST de différentes plantations de palmiers à huile âgés, une tendance qui est également observée pour différents types d'utilisation des terres dans cette étude. Une analyse régionale et à plus long terme de la tendance LST entre 2000 et 2015 basée sur les données MODIS montre que dans la journée la température moyenne de Jambi a augmenté de 1,05 ºC, suivant la tendance des changements observés et dépassant les effets du réchauffement climatique. Afin d'évaluer les effets de l'expansion du palmier à huile sur le climat, le bilan énergétique de surface, le partitionnement énergétique et les processus biophysiques jouent un rôle important et le cycle complet de rotation des plantations de palmiers à huile doit être envisagé. Basé sur nos résultats, nous construisons le cycle de rotation des plantations de palmiers à huile et les changements qui se produisent au cours du développement de la végétation de palmiers à huile. Cette étude fournit des preuves que l'expansion des plantations de palmiers à huile et d'autres cultures commerciales entraîne des changements dans les variables biophysiques, réchauffant la surface du sol et augmentant ainsi l'augmentation de la température de l'air à cause du changement climatique. En utilisant des données Landsat à haute résolution, nous avons pu inclure les effets du changement d'utilisation des terres sur les variables biophysiques. Comprendre les effets du changement de la couverture terrestre sur les variables biophysiques peut soutenir des politiques concernant la conservation des forêts existantes, la planification et l'expansion des plantations de palmiers à huile et les mesures de boisement possibles. La connaissance des variables biophysiques, du bilan radiatif et de la répartition énergétique au cours du cycle de rotation du palmier à huile peut inclure de nouvelles pratiques de gestion susceptibles de réduire les conditions environnementales et microclimatiques extrêmes dans la phase initiale des plantations de palmiers à huile.In den letzten Jahrzehnten hat Indonesien umfassende Veränderungen der Landnutzung mit einer Ausweitung von Ölpalmplantagen auf Kosten tropischer Wälder erlebt. Derzeit ist Indonesien weltweit eine der Regionen mit der höchsten Umwandlungsrate der Landnutzung, die mit der Ersetzung von Wäldern durch Ölpalmplantagen und andere Nutzpflanzen verbunden ist. Da die Vegetation ein Einflussfaktor für das Bodenklima ist, haben diese großflächigen Landtransformationen große Auswirkungen auf die biophysikalischen Variablen wie Landoberflächentemperatur (LST), Albedo, Vegetationsindizes (z.B. der normalisierte Differenzvegetationsindex, NDVI) und auf die Energiebilanz und die verschiedenen Komponenten der ausgetauschten Energie. Trotz des großen Umfangs der bereits vollzogenen und von der Regierung geplanten Landtransformationen in Indonesien hin zu Ölpalmplantagen und anderen Nutzpflanzen, ist dies die bisher erste Studie, welche die Auswirkungen dieser Landtransformation auf die biophysikalischen Variablen in Indonesien quantifiziert. Um solche Veränderungen auf regionaler Ebene zu bewerten, werden Fernerkundungsdaten benötigt. Als einer der Hauptantriebsfaktoren für viele ökologische Prozesse ist die LST direkt von Veränderungen der Landnutzung betroffen. Wir analysieren die LST aus dem thermischen Band eines Landsat-Bildes und erstellen eine hochauflösende Oberflächentemperaturkarte (30 m) für das Tiefland der Provinz Jambi auf Sumatra (Indonesien), eine Region die in den letzten Jahrzehnten eine große Landumwandlung hin zu Ölpalmen und anderen Nutzpflanzen erfahren hat. Der Vergleich von LST, Albedo, NDVI und Evapotranspiration (ET) zwischen sieben verschiedenen Landbedeckungstypen (Wald, städtische Gebiete, Brachland, junge und reife Ölpalmplantagen, Akazien- und Kautschukplantagen) zeigt, dass Wälder niedrigere Oberflächentemperaturen haben als die anderen Landbedeckungstypen, was auf einen lokalen Erwärmungseffekt nach der Umwandlung des Waldes in einen anderen Landbedeckungstyp hindeutet. Die LST-Unterschiede betrugen bis zu 10,1 ± 2,6 ºC (Mittelwert ± Standardabweichung) zwischen Wald und Brachland. Die Unterschiede in den Oberflächentemperaturen lassen sich durch einen Verdunstungskälteeffekt, der den Albedo-Erwärmungseffekt kompensiert erklären. Auf Grundlage der beobachteten Unterschieden in den biophysikalischen Variablen zwischen reifen und jungen Ölpalmplantagen, analysieren wir drei Landsat-Bilder, die eine Chronosequenz von Ölpalmplantagen enthalten um die Entwicklung von biophysikalischen Oberflächenvariablen während des 20-25 jährigen Rotationszyklus der Ölpalmplantagen zu untersuchen. Unsere Ergebnisse zeigen, dass sich die Unterschiede zwischen Ölpalmplantagen in verschiedenen Phasen des Ölpalmen-Rotationszyklus in Unterschieden in der Energiebilanz, Energiepartitionierung und biophysikalischen Variablen widerspiegeln. Während des Lebenszyklus der Ölpalmplantage nehmen die Oberflächentemperaturunterschiede allmählich ab und nähern sich grob den Werten der reifen Ölpalmphase mit einem Alter von 10 Jahren. Gleichzeitig nimmt der NDVI zu und der Albedo ab und beide Größen nähern sich den typischen Werten von Wäldern. Die Energiebilanz und die Energiepartitionierung zeigen einen Entwicklungstrend, der mit den biophysikalischen Variablen und mit dem Alter der Ölpalmplantagen zusammenhängt. Neu etablierte und junge Plantagen (<5 Jahre) haben eine geringere Nettostrahlung als reife Ölpalmplantagen, aber eine höhere Oberflächentemperaturen als reife Ölpalmplantagen. Die Veränderungen der biophysikalischen Variablen, der Energiebilanz und der Energieaufteilung während des Ölpalmen-Rotationszyklus können durch den zuvor identifizierten Verdunstungskälteeffekt erklärt werden, durch den der Albedo-Erwärmungseffekt kompensiert wird. Eine Hauptdeterminante in diesem Mechanismus ist die Vegetationsbedeckung während der verschiedenen Phasen im Rotationszyklus der Ölpalme. Der NDVI als Proxy für die Vegetationsbedeckung zeigt einen inversen Zusammenhang zur LST der Ölpalmplantagen unterschiedlichen Alters; ein Trend, der auch für andere Landnutzungstypen in dieser Studie beobachtet wurde. In einer auf MODIS Daten basierenden regionalen und langfristigeren Analyse des LST-Trends zwischen den Jahren 2000 und 2015 zeigt sich, dass die durchschnittliche Tagesoberflächentemperatur in der Provinz Jambi um 1,05 °C gestiegen ist, was dem Trend der beobachteten Landbedeckungsänderungen folgt und die Auswirkungen der Klimaerwärmung übersteigt. Um die volle Auswirkungen der Ölpalmenexpansion auf das Klima abzuschätzen, spielen die Energiebilanz, die Energiepartitionierung und biophysikalische Prozesse eine wichtige Rolle, wobei der gesamte Rotationszyklus von Ölpalmplantagen berücksichtigt werden muss. Basierend auf unseren Ergebnissen entwickeln wir eine Struktur des Rotationszyklus von Ölpalmplantagen der die während der Entwicklung der Ölpalmenvegetation auftretenden Veränderungen darstellt. Diese Studie belegt, dass die Ausweitung von Ölpalmplantagen und anderen Nutzpflanzen zu Veränderungen der biophysikalischen Variablen führt, die die Landoberfläche erwärmen und somit den Anstieg der Lufttemperatur aufgrund des Klimawandels verstärken. Durch den Einsatz von hochauflösenden Landsat-Daten konnten wir die Auswirkungen von Landnutzungsänderungen auf biophysikalische Variablen in unserer Analyse einbeziehen. Ein besseres Verständnis der Auswirkungen von Landbedeckungsänderungen auf die biophysikalischen Variablen kann Maßnahmen zur Erhaltung der bestehenden Wälder, zur Planung und zum Ausbau von Ölpalmplantagen und zu möglichen Aufforstungsmaßnahmen unterstützen. Wissen über biophysikalische Variablen, Strahlungsbilanz und Energieaufteilung während des Rotationszyklus der Ölpalme können verwendet werden, um neue Managementpraktiken einzubeziehen, die die extreme ökologischen und mikroklimatischen Bedingungen in der Anfangsphase der Ölpalmplantagen reduzieren könnten.Over the last decades, Indonesia has experienced dramatic land transformations with an expansion of oil palm plantations at the expense of tropical forests. Indonesia is currently one of the regions with the highest transformation rate of the land surface worldwide related to the expansion of oil palm plantations and other cash crops replacing forests on large scales. As vegetation is a modifier of the climate near the ground these large-scale land transformations have major impacts on surface biophysical variables such as land surface temperature (LST), albedo, vegetation indices (e.g. the normalized difference vegetation index, NDVI), on the surface energy balance and energy partitioning. Despite the large historic land transformation in Indonesia toward oil palm and other cash crops and governmental plans for future expansion, this is the first study so far to quantify the impacts of land transformation on biophysical variables in Indonesia. To assess such changes at regional scale remote sensing data are needed. As a key driver for many ecological functions, LST is directly affected by land cover changes. We analyze LST from the thermal band of a Landsat image and produce a high-resolution surface temperature map (30 m) for the lowlands of the Jambi province in Sumatra (Indonesia), a region which experienced large land transformation towards oil palm and other cash crops over the past decades. The comparison of LST, albedo, NDVI, and evapotranspiration (ET) between seven different land cover types (forest, urban areas, clear cut land, young and mature oil palm plantations, acacia and rubber plantations) shows that forests have lower surface temperatures than the other land cover types, indicating a local warming effect after forest conversion. LST differences were up to 10.1 ± 2.6 ºC (mean ± SD) between forest and clear-cut land. The differences in surface temperatures are explained by an evaporative cooling effect, which offsets an albedo warming effect. Young and mature oil palm plantations differenced in their biophysical. To study the development of surface biophysical variables during the 20 – 25 years rotation cycle of oil palm plantations, we used three Landsat images from the Jambi province in Sumatra/Indonesia covering a chronosequence of oil palm plantations. Our results show that differences between oil palm plantations in different stages of the oil palm rotation cycle are reflected in differences in the surface energy balance, energy partitioning and biophysical variables. During the oil palm plantation lifecycle the surface temperature differences to forest gradually decrease and approach zero around the mature oil palm plantation stage of 10 years. Concurrently, NDVI increases and the albedo decreases approaching typical values of forests. The surface energy balance and energy partitioning show a development patterns related to biophysical variables and the age of the oil palm plantations. Newly established and young plantations (< 5 years) have less net radiation available than mature oil palm plantations, yet have higher surface temperatures than mature oil palm plantations. The changes in biophysical variables, energy balance and energy partitioning during the oil palm rotation cycle can be explained by the previously identified evaporative cooling effect in which the albedo warming effect is offset. A main determinant in this mechanism is the vegetation cover during the different phases in the oil palm rotation cycle. NDVI as a proxy for vegetation cover showed a consistent inverse relation with the LST of different aged oil palm plantations, a trend that is also observed for different land use types in this study. On a regional and longer time scale, the analysis of the LST trend between 2000 and 2015 based on MODIS data shows that the average daytime surface temperature in the Jambi province increased by 1.05 ºC, which followed the trend of observed land cover changes and exceed the effects of climate warming. In order to assess the full climate effects of oil palm expansion the surface energy balance, energy partitioning and biophysical processes play an important role and the full rotation cycle of oil palm plantations need to be considered. Based on our result we construct the rotation cycle of oil palm plantations and the changes that occur during the development of oil palm vegetation. This study provides evidence that the expansion of oil palm plantations and other cash crops leads to changes in biophysical variables, warming the land surface and thus enhancing the increase of air temperature because of climate change. By using high-resolution Landsat data we were able to include the effects of land use change on biophysical variables. Understanding the effects of land cover change on the biophysical variables may support policies regarding conservation of the existing forests, planning and expansion of the oil palm plantations and possible afforestation measures. Knowledge of biophysical variables, radiation balance and energy partitioning during the rotation cycle of oil palm can be used to including new management practices that could reduce the extreme environmental and microclimatic conditions in the initial phase of the oil palm plantations

Mapping daily evapotranspiration at Landsat spatial scales during the BEAREX’08 field campaign

Robust spatial information about environmental water use at field scales and daily to seasonal timesteps will benefit many applications in agriculture and water resource management. This information is particularly critical in arid climates where freshwater resources are limited or expensive, and groundwater supplies are being depleted at unsustainable rates to support irrigated agriculture as well as municipal and industrial uses. Gridded evapotranspiration (ET) information at field scales can be obtained periodically using land–surface temperature-based surface energy balance algorithms applied to moderate resolution satellite data from systems like Landsat, which collects thermal-band imagery every 16 days at a resolution of approximately 100 m. The challenge is in finding methods for interpolating between ET snapshots developed at the time of a clear-sky Landsat overpass to provide complete daily time-series over a growing season. This study examines the efficacy of a simple gap-filling algorithm designed for applications in data-sparse regions, which does not require local ground measurements of weather or rainfall, or estimates of soil texture. The algorithm relies on general conservation of the ratio between actual ET and a reference ET, generated from satellite insolation data and standard meteorological fields from a mesoscale model. The algorithm was tested with ET retrievals from the Atmosphere–Land Exchange Inverse (ALEXI) surface energy balance model and associated DisALEXI flux disaggregation technique, which uses Landsat-scale thermal imagery to reduce regional ALEXI maps to a finer spatial resolution. Daily ET at the Landsat scale was compared with lysimeter and eddy covariance flux measurements collected during the Bushland Evapotranspiration and Agricultural Remote sensing EXperiment of 2008 (BEAREX08), conducted in an irrigated agricultural area in the Texas Panhandle under highly advective conditions. The simple gap-filling algorithm performed reasonably at most sites, reproducing observed cumulative ET to within 5–10% over the growing period from emergence to peak biomass in both rainfed and irrigated fields

Impact of land use change on urban surface temperature and urban green space planning; case study of the island of Bali, Indonesia

Land use and surface temperature were monitored from 1995 to 2013 to examine green space development in Bali using Landsat and ASTER imageries. Urban areas were formed by conversion of vegetation and paddy fields. Heat islands with surface temperature of over 29 ºC were found and influenced by urban area types. High priority, low priority and not a priority zones for green space were resulted by weighted overlay of LST, NDVI and urban area types

Participatory Roles of Urban Trees in Regulating Environmental Quality

abstract: The world has been continuously urbanized and is currently accommodating more than half of the human population. Despite that cities cover only less than 3% of the Earth’s land surface area, they emerged as hotspots of anthropogenic activities. The drastic land use changes, complex three-dimensional urban terrain, and anthropogenic heat emissions alter the transport of mass, heat, and momentum, especially within the urban canopy layer. As a result, cities are confronting numerous environmental challenges such as exacerbated heat stress, frequent air pollution episodes, degraded water quality, increased energy consumption and water use, etc. Green infrastructure, in particular, the use of trees, has been proved as an effective means to improve urban environmental quality in existing research. However, quantitative evaluations of the efficacy of urban trees in regulating air quality and thermal environment are impeded by the limited temporal and spatial scales in field measurements and the deficiency in numerical models. This dissertation aims to advance the simulation of realistic functions of urban trees in both microscale and mesoscale numerical models, and to systematically evaluate the cooling capacity of urban trees under thermal extremes. A coupled large-eddy simulation–Lagrangian stochastic modeling framework is developed for the complex urban environment and is used to evaluate the impact of urban trees on traffic-emitted pollutants. Results show that the model is robust for capturing the dispersion of urban air pollutants and how strategically implemented urban trees can reduce vehicle-emitted pollution. To evaluate the impact of urban trees on the thermal environment, the radiative shading effect of trees are incorporated into the integrated Weather Research and Forecasting model. The mesoscale model is used to simulate shade trees over the contiguous United States, suggesting how the efficacy of urban trees depends on geographical and climatic conditions. The cooling capacity of urban trees and its response to thermal extremes are then quantified for major metropolitans in the United States based on remotely sensed data. It is found the nonlinear temperature dependence of the cooling capacity remarkably resembles the thermodynamic liquid-water–vapor equilibrium. The findings in this dissertation are informative to evaluating and implementing urban trees, and green infrastructure in large, as an important urban planning strategy to cope with emergent global environmental changes.Dissertation/ThesisDoctoral Dissertation Civil, Environmental and Sustainable Engineering 201