Durham E-Theses The Eect of Land Cover on the Air and Surface Urban Heat Island of a Desert Oasis AL-ALI, ABDULRAHMAN,MUBARAK,H How to cite: AL-ALI, ABDULRAHMAN,MUBARAK,H (2015) The Eect of Land Cover on the Air and Surface Urban Heat Island of a Desert Oasis , Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/11290/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk 2 The Effect of Land Cover on the Air and Surface Urban Heat Island of a Desert Oasis Submitted for the degree of Doctor of Philosophy Submitted by Abdulrahman Mubarak H. Al Ali Department of Geography Durham University United Kingdom June 2015 The Effect of Land Cover on the Air and Surface Urban Heat Island of a Desert Oasis Abdulrahman Mubarak H. Al Ali Abstract Cities often experience a distinct climate compared to the surrounding area characterized by differences in air temperature, humidity, wind speed and direction, and amount of precipitation. Thus far, research on the urban heat island (UHI) effect has focused on cool temperate, Mediterranean and tropical climatic regions, whereas less attention has been given to the study of arid regions where the daytime surface temperature can be extremely high. This study concerns the Al Ahsa oasis, Saudi Arabia, which is a rapidly developing urban centre in an arid region. The aim of this study is to analyze the effect of land cover on the urban and sub-urban environment using ground data and multi-scale and multi-temporal satellite thermal imagery. Land surface temperatures derived from satellite thermal imagery are compared with observations from ground-based fixed and mobile temperature and relative humidity logging stations for periods in February and July. Thermal radiometers from different sensors, Landsat 7 ETM+ and MODIS, were used to measure the outgoing radiation budget at specific locations within the urban landscape. Fieldwork was undertaken contemporary with satellite overpasses to measure the diurnal air temperatures and relative humidity across different land cover types including agriculture, urban, water, exposed rock surfaces, sabkha and sand dunes. These data provide the most complete experiment so far conducted to test and refine models of the thermal radiation budget of the arid zone at the sub-city scale. The findings of this study have emphasized the effectiveness of combining the two methods, ground and satellite data, to investigate the relationship between land cover and UHI intensity. Results reveal a significant relationship between UHI spatial distribution and land cover using the two methods: mobile traverses and remote sensing. The UHI intensity is higher during the summer than the winter and at night-time than in the day. The highest UHI intensity, (10.5 °C), is located over the two major cities in the oasis (Al Hufuf and Al Mubarraz) while the lowest temperatures (- 6.4 °C below UHI), are recorded in the small villages and vegetated areas during summer at night. The outcome of this thesis will help future urban development and planning projects and provide a framework for implementing rules and regulations by local government agencies for a sustainable urban development approach. Table of Contents TABLE OF CONTENTS i LIST OF ILLUSTRATIONS vii DECLARATION xvii ACKNOWLEDGEMENTS xviii Chapter 1: Introduction ...................................................................................................... 1 1.1 Applied Climatology and Urban Climate ................................................................ 1 1.2 Urban Heat Islands ................................................................................................... 2 1.2.1 Definition and Background .............................................................................. 2 1.2.2 Types of Urban Heat Islands ............................................................................ 4 1.2.2.1 Surface Urban Heat Islands ...................................................................... 4 1.2.2.2 Atmospheric Urban Heat Islands .............................................................. 5 1.3 Microclimates and the Urban Heat Island ............................................................... 6 1.3.1 The formation of urban heat islands................................................................. 8 1.3.1.1 Reduced vegetation cover in urban areas ................................................. 8 1.3.1.2 Properties of urban materials .................................................................... 9 1.3.1.3 Urban geometry ...................................................................................... 10 1.3.1.4 Radiation and energy budget .................................................................. 11 1.3.1.4.1 Short-wave radiation ............................................................................ 11 1.3.1.4.2 Thermal storage ................................................................................... 12 1.3.1.5 Anthropogenic heat ................................................................................. 13 1.3.1.6 Weather conditions and geographical location ....................................... 13 1.4 Measuring Urban Heat Islands............................................................................... 14 1.4.1 Ground Data Applications.............................................................................. 14 i 1.4.2 Remote Sensing Applications ........................................................................ 18 1.5 Significance of this Research ................................................................................. 24 1.5.1 Global Warming ............................................................................................. 24 1.5.2 Land Cover Change........................................................................................ 25 1.5.3 Energy Use ..................................................................................................... 26 1.5.4 Air Quality ..................................................................................................... 27 1.5.5 Human Health and Comfort ........................................................................... 28 1.5.6 Water Quality ................................................................................................. 29 1.6 Research Questions, Aims and Objectives ............................................................ 29 1.6.1 Research Questions ........................................................................................ 29 1.6.2 The Aim ......................................................................................................... 30 1.6.3 The Research Objectives ................................................................................ 30 1.7 Thesis Structure ..................................................................................................... 30 Chapter 2: Description of the Study Area ....................................................................... 32 2.1 Introduction ............................................................................................................ 32 2.2 Geographical location and background ................................................................. 32 2.3 Topography ............................................................................................................ 36 2.3.1 Aeolian formations ......................................................................................... 36 2.3.2 Sabkha deposits .............................................................................................. 37 2.3.3 Gravel deposits ............................................................................................... 38 2.3.4 Hills and Mesas .............................................................................................. 38 2.4 Local Climate ......................................................................................................... 38 2.4.1 Air Temperature ............................................................................................. 39 2.4.1.1 Summer and winter temperatures ........................................................... 39 2.4.1.2 Spring and autumn temperatures ............................................................ 40 2.4.1.3 Relative humidity .................................................................................... 41 2.4.1.4 Synoptic systems and wind patterns in the study area ............................ 41 ii 2.4.1.4.1 Pressure systems and winds in the winter ............................................ 42 2.4.1.4.2 Pressure systems and winds in the summer ......................................... 43 2.4.2 Rainfall ........................................................................................................... 44 2.5 Population