Elsevier

Urban Climate

Volume 24, June 2018, Pages 600-615
Urban Climate

Surveying of Heat waves Impact on the Urban Heat Islands: Case study, the Karaj City in Iran

https://doi.org/10.1016/j.uclim.2017.12.004Get rights and content

Abstract

From July 6th to August 5th of 2014, a severe heatwave happened in Iran. This study analysis the formation and relative effect of this heatwave event on the environmental situation in the Karaj city (west of Iran capital). This city has experienced warm summers and high amounts of heat-related mortality. This research is accomplished according to the statistical-synoptic-approach and mobile survey data. Two main data sets are collected during this event from 20 stations in the urban and rural areas. The results of data are derived from hierarchical cluster analysis by using Ward's method. Analysis of mid-level synoptic charts demonstrate a low pressure at ground level in North West of India (Gange's thermal low pressure) which covers the case study area together with a high-pressure system that dominates in the middle levels. This phenomenon affects the thickness of the atmosphere and causes warm air subsidence, abnormal air heating and a stable urban heat island (UHI) in the region. Compared to the rural areas, the temperature of the city is about 1 °C warmer within the day times and up to 2.5 °C warmer at nights. Furthermore in comparison with the rural areas, in urban environment the temperature value combination of surrounding humidity stations, determined systematically warmer status. This intensity of UHI is the simplest and most quantitative indicator of the thermal modification imposed by the Karaj city upon its territory, and shows its relative warming compared to the surrounding rural environment at night times.

Introduction

Heatwave patterns and urban heat island phenomena have influenced environmental conditions by creating numerous problems in societies. Most of the human activities are sensitive to extreme temperature (Cox and Tikvart, 1990). Heat waves are the main point of the contemporary global climate changes that are caused damaged to live and properties in terms of its frequency of occurrence (Cohen, 2008). In meteorological terms, a heat wave is defined as a prolonged period of unusually hot weather (Hajat et al., 2002, Diaz et al., 2002, Kyselý, 2004, Michelozzi et al., 2004).

Statistically, heat waves imply to make positive fluctuation over the mean daily temperature that is continuity referring to consecutive days (sometimes weeks or months) in certain geographical spaces. According to definition, two factors of time and geographical region have become more important for occurrence or non-occurrence of heat waves. For example, high temperature upper than 24 °C is the heat wave threshold in the UK, but in Iran this threshold is much higher. The heat wave threshold is about 42 °C when the high temperature is continued for at least two days or more. In classification of environmental hazards, heatwave is the subgroup of extreme temperatures (Oke et al., 1999).

Urban heat island (UHI) is a well-known and thoroughly researched phenomena in urban climatology. In certain cities of the temperate climatic zone, structures and features of the UHI are well documented (Jerome et al., 2005, Kovatsand and Hajat, 2008). A higher urban-rural temperature forms the basis of UHI effect, which is a common urban phenomena (Arnfield, 2003).

Studies about UHI illustrate that temperature difference between municipal, rural and suburb areas is more obvious in minimum temperature condition (Bulut et al., 2008, Süleyman and Yilmaz, 2010). A number of reasons for this temperature differences can be the release of anthropogenic global warming (Zhang et al., 2014, Zhang et al., 2014), increase in urban pollution layer by absorption of longwave radiation emitted from the surface of that part will emit to the surface of land again (Shahmohamadi et al., 2011). Geometry of the cities with high buildings creates a unique three-dimensional edifice by producing air stagnation or slow speed of wind which in return creates lower cold air entrance to cities, changing the in land shield, spoiling vegetation, forming impermeable surfaces. Constructed materials such as asphalt and concrete have upper heat capacity and thus decrease evaporation, transpiration and release the absorbed energy slowly (Grize et al., 2005). The UHI intensity is greatest when it is under system conditions of stationary high-pressure, stable air and clear sky. This tends to disappear if cloudiness and wind speed increases.

Unprecedented heat wave in 2014 has brought many damages to Karaj city. The objective of present study is to determine if urban heat islands are present or not and to confirm whether any apparent urban-rural differences are statistically significant. Moreover, this study will identify circulation patterns in superheat days through synoptic approach. Then the UHI's impact on the environmental conditions of the Karaj city will be quantified and it will be shown how human health conditions could be exacerbated due to the intense UHIs. Heat waves will exacerbate by urban heat island effect which in return could have this potential to negatively influence the health and welfare of urban residents. In Section 2 we will bring materials and methods in which a brief discussion about importance and motivation of study for the chosen area is brought up and tools which used to investigate the question of study are fully described. Then in the third section findings and results of this work are fully discussed and addressed, and finally in Section 4, conclusions are brought up.

Section snippets

Research background

The increase of extreme climatic conditions is either the most important and as well, the worst effect of global warming. There exist significant relations between heat wave occurrence and mortality (Susanna et al., 2007). UHIs are associated with thermal and hygrometric discomfort because of the rise in temperature (Amorim, 2005). Correlation of atmospheric processes and Heat Waves involve significant mid troposphere anomalies that extended periods of subsidence and clear skies, light winds,

Synoptic patterns: recognition and analysis

According to previous studies (Kim and Baik, 2002, Rodriguez and Jimenez, 2000, Roth, 2012, Stewart, 2011, Yague et al., 1991), synoptic conditions strongly exert control on the heat island magnitude, In addition, the prevailing weather conditions during heat island measurements, as well as antecedent conditions leading up to a heat island event, strongly affect the observed temperature differences between urban and rural sites (Stewart, 2011).

In order to recognize the predominant sea level

Conclusions

The accelerated development of the Karaj city has changed the urban environment fiber. Surfaces have become impermeable and dry because of replacement of vegetation with other seats like asphalt. Continuation of this trend has warmed urban and the suburb of the region, which in return this has created heat islands with higher temperatures. Comparing the urban areas of Karaj city with its suburbs, the results demonstrated a considerable UHI sign whereby temperature amount was warmer > 2.5 °C at

Acknowledgements

We would like to acknowledge Karaj Meteorological Organization for obtaining marmonix temperature datalogger in order to register synoptic data during the research that was very useful.

References (93)

  • M. Unkašević et al.

    An analysis of heat waves in Serbia

    Glob. Planet. Change J.

    (2009)
  • C. Yague et al.

    Statistical analysis of the Madrid urban heat island

    Atmos. Environ.

    (1991)
  • B. Zhang et al.

    The cooling effect of urban green spaces as a contribution to energy-saving and emission-reduction: a case study in Beijing, China

    Build. Environ.

    (2014)
  • A. Ahmadabadi et al.

    Assessment and zoning of tourism climate of Iran using tourism climate index (TCI)

    Phys. Geogr. Res. Q.

    (2010)
  • E.K. Ahmadnezhad et al.

    Excess mortality during heat waves, Tehran Iran: an ecological time series study

    J. Res. Health Sci.

    (2013)
  • B. Alijani

    The relation between pressure distribution and air pollution concentration in Tehran

  • S.P. Almeida et al.

    Effects of apparent temperature on daily mortality in Lisbon and Oporto, Portugal

    Environ. Health J.

    (2010)
  • M.C.C.T. Amorim

    Intensidade e forma da ilha de calor urbana em Presidente Prudente/SP

    Geosul

    (2005)
  • A.J. Arnfield

    Two decades of urban climate research: a review of turbulence, exchanges of energy and water, and the urban heat island

    Int. J. Climatol.

    (2003)
  • L. Balkestahl et al.

    The influence of weather types on the urban heat island's magnitude and patterns at Paranhos (Porto): a case study from November 2003 to January 2005

  • Y. Bulut et al.

    Urban-rural climatic differences over a 2-year period in the City of Erzurum, Turkey

    Atmosfera

    (2008)
  • I. Camilloni et al.

    Temporal variability of the Buenos Aires, Argentina, urban heat island

    Theor. Appl. Climatol.

    (2012)
  • F. Chen et al.

    A synoptic climatology of summertime heat and humidity in the Piedmont region of North Carolina

    J. Appl. Meteorol. Climatol.

    (2006)
  • S. Cohen

    Analog European Heat waves for U.S. cities to analyze impacts on heat-related mortality

    Bull. Am. Meteorol. Soc.

    (2008)
  • A.C. Comrie

    Mapping a wind-modified Urban Heat Island in Tucson, Arizona (with comments on integrating research and undergraduate learning)

    Bull. Am. Meteorol. Soc.

    (2000)
  • A. Costello et al.

    Making climate change part of global health, interview by Mark Honigsbaum

    Lancet

    (2009)
  • J. Diaz et al.

    Heat waves in Madrid 1986–1997: effects on the health of the elderly

    Int. Arch. Occup. Environ. Health

    (2002)
  • D. Doyle et al.

    Assessing a small summer urban heat island in rural south central Pennsylvania

    Geogr. Bull.

    (2008)
  • V. Dubreuil et al.

    Métodos e monitoramento da variabilidade Espaçotemporal da ilha de calor em cidades de porte médio—Rennes/França e Presidente Prudente/Brasil

  • I. Eliasson

    Intra-urban nocturnal temperature differences: multivariate approach

    Clim. Res.

    (1996)
  • L. Feudale et al.

    Influence of sea surface temperature on the European heat wave of 2003 summer. Part I: an observational study

    Clim. Dyn.

    (2011)
  • W. Fisher

    The Cambridge History of Iran, Physical Geography

    (1968)
  • L. Gartland et al.

    de Calor Como Mitigar Zonas de Calor em Áreas Urbanas

    (2010)
  • A.L. Gomez et al.

    La isla de calor en Madrid: Avance de un estudio de clima urbano

    Estud. Geogr.

    (1984)
  • E.I. Griggs et al.

    Guide for estimating differences in building heating and cooling energy due to changes in solar reflectance of a low-sloped roof

  • S. Grimmond

    Urbanization and global environmental change: local effects of urban warming

    Geogr. J.

    (2007)
  • L. Grize et al.

    Heatwave 2003 and mortality in Switzerland

    Swiss Med. Wkly.

    (2005)
  • Y. Guo et al.

    The impact of temperature on mortality in Tianjin, China: a case-crossover design with a distributed lag nonlinear model

    Environ. Health Perspect.

    (2011)
  • S. Hajat et al.

    Impact of hot temperatures on death in London: a time series approach

    J. Epidemiol. Community Health

    (2002)
  • S. Hajat et al.

    Mortality displacement of heat-related deaths: a comparison of Delhi, São Paulo, and London

    Epidemiology

    (2005)
  • H.R. Heidari et al.

    Validation of humidex in evaluating heat stress in the outdoor jobs in arid and semi-arid climates of Iran

    Journal of Health and Safety at Work (JHSW)

    (2016)
  • K.M. Hinkel et al.

    The urban heat island in winter at Barrow, Alaska

    Int. J. Climatol.

    (2003)
  • E.D. Hunt et al.

    Significant inversions and rapid in situ cooling at a well-sited Oklahoma Mesonet station

    J. Appl. Meteorol. Climatol.

    (2007)
  • IPCC, Climate Change

    The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change

    (2007)
  • D. Jerome et al.

    Pseudovertical temperature profiles and the urban heat island measured by a temperature datalogger network in Phoenix, Arizona

    J. Appl. Meteorol.

    (2005)
  • D.B. Johnson

    Urban modification of diurnal temperature cycles in Birmingham, U.K.

    J. Climatol.

    (1985)
  • Cited by (26)

    • Spatial pattern of the green heat sink using patch- and network-based analysis: Implication for urban temperature alleviation

      2022, Sustainable Cities and Society
      Citation Excerpt :

      Vegetation cover in the study area includes gardens, municipal green areas, parks, agricultural lands, and dense and sparse rangelands (Mokhtari, Barghjelveh & Sayahnia, 2021). Karaj has followed a significant sprawl and scattered pattern of development expansion (Ghobadi, Khosravi & Tavousi, 2018; Taleshi & Ghobadi, 2012), leaving plenty of vacant and barren land within the urban environment (Fig. 1). Currently, the city hosts a population of over 1592,000 people (https://www.amar.org.ir).

    View all citing articles on Scopus
    View full text