POSTER 11: GD - Surface UHI from satellite
Evaluation of the Influence of Land-use/Land-cover Change on the Surface Temperature of Federal Capital City Abuja,Nigeria
Ahmadu Bello University,Zaria, Nigeria
As cities rapidly develop to accommodate the growing urban population, a transformation in city landscape becomes inevitable leading to changes in land use and land cover, this has environmental and ecological consequences one of which is the changes observed in the micro climate of major cities. This study employed remote sensing and GIS in evaluating the influence of land use/land cover (LULC) change in the Federal Capital City (FCC) Abuja on surface temperature. A nineteen year study period was chosen with specific objectives to examine land use land cover changes within the set period, assess the growth of urban FCC and examine the effect of this growth on surface temperature and subsequently, urban heat island (UHI) development. Three Landsat TM and ETM+ images of the study area (1987, 2001 and 2006), all acquired in the dry season (September to December) were used to complete the study; Land use/ land cover analysis was carried out using IDRISI 17.0 and Land surface temperature of the various land uses for all three years was extracted from thermal band (6). LULC was found to increase (18.57%) in areal extent for built up between 1987 and 2001 while by 2006, a 2.31% decrease for built up is recorded, showing changes in urban growth and consequently, on surface temperature. correlation analysis was carried out and the degree to which UHI was present in the city established.
Investigating Urban Cool Islands In Semi Arid Areas, With the case study of Erbil.
University of Leicester, United Kingdom
Remote Sensing data is frequently used to examine spatial and temporal variation of Urban Heat Island (UHI) in different climates. Diurnal Urban Cool and nocturnal Urban Heat Islands in semi-arid cities like Erbil have not been studied thoroughly enough. The purpose of this study is to investigate the spatial and temporal variation of UHI in semi-arid area. Thermal data of Landsat 5, 7, and 8 data from 1992 to 2013 in addition to use MODIS Aqua and Terra Land Surface Temperature (LST) was selected in this investigation. To measure UHI intensity, ten kilometre buffer zone around Erbil city compared as a rural area with the urban area. The result indicated at night the city area is 2.23°C higher temperature than the surrounding area proves the existence of nocturnal SUHI. However, LST during the day in the rural area was 1.22°C higher. The initial result of both Landsat and MODIS confirms the existence of a diurnal Urban Cool Island (UCI) in the study area. This indicates the increasing size of daily cooler regions in the city alongside the growth of the city in 2013.
Combining Satellite and Ground Observations to Assess the Urban Heat Island in Morocco
1LHEA,Vulnerability and Adaptation to Climate Change in Morocco (GRIVAC),Cadi Ayyad University ; Faculty of science Semlalia, Morocco; 2Cadi Ayyad University, FS Semlalia ;Research Group on impact,Vulnerability and Adaptation to Climate Change in Morocco (GRIVAC); 3NASAGoddard Space Flight Center Biospheric Sciences Laboratory
Urban areas are ecosystems that interact with climate. This interaction is currently little known because of lack of data, at appropriate spatial and temporal scales, to characterize the urban metabolism within the synoptic climate scale.
Landsat and MODIS are complementary instruments which offer a unique opportunity to describe the effects of urbanization on its immediate environment .This is especially true in a countries like Morocco where the observation is rare.
In this study we will use MODIS land surface temperature (LST), normalized difference vegetation index (NDVI) and land cover and land derived from them use in a spatial analysis to assess the urban heat island (UHI) generated by buildups, its amplitude, its spatial extent and its relationship to different ecological setting for most populous cities in morocco between 2003 and 2013.
We will also examine the relationship between the UHI and the shape of the urban settlement. A temporal analysis will then be performed to quantify how change in climate may alter urban heat islands.
Analysis of Surface Temperature Accuracy in ASTER Images according to Land-Use Type
1National Institute of Ecology, Korea, Republic of (South Korea); 2Changwon National University, Republic of (South Korea)
This study analyzed the accuracy of the surface temperature according to land-use type in an ASTER image of Changwon city, and derived a calibration model for each land-use type. Eight land-use types were considered: public facilities, urban park, commercial facilities, low-rise and high-rise apartments, and residential areas. A total of eight ASTER images were collected in the summer, from June 2012 to August 2014. Daytime images were collected on 5 scenes and nighttime images were collected on 3 scenes. To analyze the accuracy of the surface temperatures in the ASTER images, the temperatures were measured on-site using a thermal infrared thermometer (Testo 381; accuracy; ± 1.5˚C; emissivity: 0.95) at the same time the images were collected; thus, taking into account the land-cover types distributed in the target areas. The surface temperatures between the ASTER images and the on-site measurements were compared by analyzing the Vector GRID of the same spatial resolution as that of the ASTER images, and then calculating the area ratio by land-cover type. Then the surface temperature and emissivity measured on-site was used to analyze the mean surface temperature for each Vector GRID based on the on-site measured surface temperature and emissivity. In addition, a calibration model was derived by comparing the on-site measured temperature with the surface temperature of the ASTER image for the same location and performing a linear regression analysis for each land use type.
The results show that on July 28, 2012, when there was some influence of clouds in the ASTER image, the RMSE (root mean square error) of the on-site measured surface temperatures showed the largest difference (10.7 °C on average) and on September 23, 2012, in early fall, it showed the smallest difference (4.3 °C). Linear regression analysis was performed between the data of the ASTER images and the on-site measurements for each land-use type; the R2 of low-rise apartments was 0.7058, showing the highest correlation, followed by public facilities (0.5454), commercial facilities (0.6840), detached houses (0.6446), high-rise apartments (0.5395), and lawn squares (0.5607). On the contrary, the R2 of the urban park area was low (≤ 0.3). This may be due to the inaccurate characterization of the land cover characteristics of park areas because of the many high-traffic roads surrounding the urban parks. The RMSE was smaller in the nighttime as compared to that in the daytime; for September 21 and 28, 2012, about 2.5°C was obtained, and for August 14, 2013, the difference was the smallest (1.3 °C). The R2 for all the land-use types, except for urban park areas, was 0.9 or higher, showing very high correlations; however, the R2 of the urban park areas on August 14, 2013 was 0.0302, the lowest value in this study. Since the data for August and September were used for the nighttime, the differences in surface temperature caused by the change in season were large and thus, temperature was divided; the R2 was high in the linear regression analysis because of these distributions of surface temperatures. Therefore, for the nighttime, an additional analysis that considers more seasons should be performed.
Geospatial Assessment of Urban Expansion and Land Surface Temperature in Akure, Nigeria
Federal University of Technology, Akure, Nigeria
This study employs the use of geo-spatial techniques with survey to identify various transformations in land use land cover types and their corresponding land surface temperature (LST) between a 20-year time intervals in Akure, Nigeria. The analysis was done using available Landsat TM and ETM+ satellite data for 1986, 2002 and 2006. The variability of the LST has been investigated with respect to different land use / land cover types that were determined from the Visible and Near Infrared (NIR) channels. Also, the emissivity per pixel is retrieved directly from satellite data and estimated as narrow band emissivity at the satellite sensor in order to have the least error in the surface temperature estimation. The study revealed that the built up area has expanded from 17.88% of the total land area of Akure in 1986 to 27.02% in 2006 with a corresponding increase of 9.9 °C in LST, indicating an average annual increase of 0.5 °C. The vegetation cover has reduced from 47.23% to 37.79% with an increase of 2.79 °C in temperature. A very strong correlation between the LST and the NDVI has also been established. The implication of the uncontrolled unprecedented expansion in the city may exacerbate environmental and ecological problems such as the Urban Heat Island if not properly ameliorated. This study actually exploits the possibility of using Remote Sensing and Geographic information systems (GIS) in the drive towards achieving sustainable urban environment in terms of planning, policy and decision making.
KEYWORDS: Urban expansion, Land use, NDVI, LST, Emissivity
Urbanisation Influence on Microclimatic Conditions of a Pre-Colonial City in Nigeria
Federal University of Technology, Akure, Nigeria
This study examined the effects of urbanization on the microclimatic condition of Ibadan (located between latitude 7° 20´N – 7° 25´N and longitude 3° 51´E–3° 56´E), the largest and fastest growing indigenous pre-colonial tropical city in West Africa. Ibadan is the administrative capital of Oyo state in the south-western part of Nigeria. Fixed point observations and measurements were carried out during an intensive operation period from November 1st 2014 to November 23rd 2014 using shielded stand alone i- button thermocron temperature and relative humidity electronic sensors programmed at 10-minute sampling interval. The sensors were mounted on street lamp posts at above head height in selected locations representing different land use types and local climate zones classification. Variations in temperature, humidity and vapour pressure differences within the different LCZs were investigated and identified to be shapened by the different land use characteristics. The magnitudes of the differences in the microclimatic parameters, their diurnal and daily variation and influence of weather variability are further investigated. Areas outskirts of the city are characterized by higher relative humidity and lower air temperature as compared to the central traditional districts throughout the days of observation. It is pertinent to point out that the recommendations from this study can be adopted, in order to control the urbanization process in the study area, and to ensure sustainable urban development.
KEYWORDS: Urbanisation, local climate, land use, Precolonial city, Nigeria
Urban ‘heat island’ in Moscow by satellite data
1Lomonosov Moscow State University, Faculty of Geography; Russian Federation; 2‘Dubna’ International University of Nature, Society and Man; Russian Federation
The urban ‘heat island’ phenomenon in Moscow city has been studied by long-term data of ‘Aqua’ and ‘Terra’ satellites which are supplied by MODIS radiometers. The surface temperature has been analyzed in Moscow region with a spatial resolution of 1 km. Nearly 70 satellite images in cloudless conditions for the period from 2009 to 2013 have been found and studied. The average values of the surface temperature inside the city were compared with ones outside it (at rural zone) for this period. The average intensity of the urban ‘heat island’ by radiometer data has been received as equal from +2 to +3 ˚C. It varied from –0.2 to +6.5 ˚C so that sometimes in the midday this parameter may be a bit negative. These results have been compared with the data about ‘heat island’ in Moscow by network of ground meteorological stations.
The annual course of the ‘heat island’ intensity in Moscow has been studied.
Besides, the whole area of the city has been divided into four types of the surface including urban forests and parks, open water (river and lakes), area of dense urban saturation and all the rest (grasslands, separate buildings, etc.). As a result, the average surface temperature has been calculated for each of these types separately and compared both with each other and with conditions of rural zone outside the city.
Some methodical questions of satellite data interpretation, including comparison between surface temperature and air temperature have been discussed additionally.
Observation of Urban Thermal Regime in Abu Dhabi city using Satellite Remote Sensing
Masdar Institute of Science and Technology, United Arab Emirates
In this work, we evaluate the temporal and spatial variations of land surface temperature in Abu Dhabi city for various land covers. In a previous study, we observed that the urban heat island effect is inverted during the day time in dense urban areas in desert cities, especially in areas with vegetation. This study aims to study such behavior in greater detail by making use of the relatively high spatial resolution and temporal resolution offered by Landsat -8 satellite, which carries a two channel thermal imager on board, along with visible and near-infrared sensors. The thermal imager provides a ground pixel resolution of 100m and a temporal resolution of 16 days enabling a spatial and temporal analysis of thermal regime. The multispectral images consisting of visible, near-infrared and shortwave infrared images will be used to accurately classify the images into different classes of land cover and the thermal images will be used to estimate LST. A sequence of 23 images acquired over one year period is analyzed to describe the seasonal and spatial distribution of LST variation in Abu Dhabi City.
Identify oh heat island through the remote sensing in the Santarém Municipality.
1Universidade Federal do Oeste do Pará, Brazil; 2Universidade Federal do Oeste do Pará; 3Secretaria de Estado de Meio Ambiente; 4Universidade Federal do Pará
Studies in several countries around the world show that human activities are mainly responsible for changes in urban climate, resulting in the appearance of heat islands. This phenomenon is related to the heat absorption capacity of structure found in urban areas such as asphalt, bare soli, tile, concrete, as well as the lack of vegetation in surface temperature in the city of Santarem-Pará to verify the existence of heat islands and make an analysis of the albedo and the index of normalized difference vegetation (NDVI) from Santarém. For this, we used the satellite image Landsat 5 TM for the july 12, 2009. Obtaining the surface temperature, albedo and the index of normalizes difference vegetation (NDVI) was performed by applying the algorithm SEBAL software, ERDAS Imagine 9.1. Google Earth images were used to obtain an overview of the regions that showed temperatures significant for the study. The NDVI values were low for the urban area while the albedo showed high values. It was observed that areas with higer heating concentrated in urban areas, the temperatures ranged between 300C and 330C. The highest temperatures found were 340C and 350C in a central area of de municipality and peripheral part.
Analysing the climatic effects of local block rehabilitation programs in Budapest-Ferencvaros
Eotvos Lorand University, Hungary
Ferencvaros, the 9th district of the Hungarian capital Budapest is a very heterogeneous part of the city consisting of 3- and 4-storey old buildings, block houses with either 4 or 8 levels, brown industrial areas, and large areas occupied by the railways system. Partly due to the functional and structural changes of special subsections of the district substantial local climatic changes occurred in the past few decades. From the local government concentrated efforts were made to complete several block rehabilitation programs already starting from 1980s. Since 1993 in the most densely built inner part of the district entire blocks were renovated and modified in order to create more livable environment for the citizens. Within the framework of these programs inner parts of the blocks were demolished, thus, inside the blocks more common green areas could be created. The climatic effects are evaluated on the basis of satellite measurements, namely, surface temperature fields derived from radiation data of seven different infrared channels measured by sensor MODIS (onboard satellites Terra and Aqua). From the surface temperature data rural mean values around Budapest are used to calculate pixelwise SUHI (surface urban heat island intensity). Our main goal is to analyze whether the generally positive changes of the built environment can also be recognized in the urban heat island effect of this area.
Analysing the urban vegetation effect using satellite imagery for Budapest
1Eotvos Lorand University, Hungary; 2Hungarian Meteorological Service
Budapest is the Hungarian capital, which is divided by the river Danube into a hilly, greener Buda side on the west, and the flat, more densely built-up Pest side on the east. Most of the extended urban vegetation can be found in the Buda side in the form of forests. The effects of the past changing of these green areas are analyzed using surface temperature data calculated from satellite measurements in the infrared channels, and NDVI (Normalized Difference Vegetation Index) derived from visible and near-infrared satellite measurements. We aim to evaluate the relationship of surface temperature and NDVI in this urban environment with special focus on vegetation-related sections of the city where the vegetation cover either increased or decreased remarkably, e.g., recently built shopping centers in previously vegetated area or brown industrial area where low quality vegetation appeared in the past decade. Moreover, changing trends are also analyzed in connection to local effects of global warming.