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Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
Urban heat islands
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Urban heat islands

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2012 …

2012
By Manju mohan

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  • 1. Delhi 2050 Workshop, Delhi, 30 Jan – 3 Feb 2012Assessment of Urban Heat Island Effect in Megacity Delhi Manju Mohan, Professor Centre for Atmospheric Sciences Indian Institute of Technology, Delhi India mmohan6@hotmail.com 1
  • 2. Urban Heat Island: Introduction• The urban heat island effect is defined as any urban area which has a tendency to be warmer than a surrounding rural/lesser developed area.• Some of the earliest incidences of urban heat island effect were observed in late nineteenth century in cities such as London , Paris, Berlin and other European cities which were major centers of industrial activity.• Today, the phenomenon of urban heat island is an existent issue of concern in many cities of both developed and developing nations of the world. Prof. Manju Mohan, IIT Delhi 2 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 3. Classical representation of temperature profile of an urban areaProf. Manju Mohan, IIT Delhi 3 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 4. Heat Island Effect: Causes• Absorption of heat by urban infrastructure – Urban areas are characterised by concrete surfaces, high rise buildings and dense human as well as vehicular population. – Man made structures such as roads absorb solar radiation during the day resulting in increase of temperature of those surfaces and the air in contact with them. – As the day progresses, a dome of warm air forms over the urban areas. – After the sun sets, the buildings form a canopy structure preventing the heat loss to the upper atmosphere. Thus temperatures remain elevated, and so the heat island effect persists during the night as well. Prof. Manju Mohan, IIT Delhi 4 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 5. Heat Island Effect: Causes• Lack of vegetation surface – Vegetated surfaces provide moisture for evaporation. Thus lack of moisture restricts heat dissipation. Prof. Manju Mohan, IIT Delhi 5 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 6. Heat Island Effect: Causes• Apart from changes in LULC, Anthropogenic Heat adds to the urban heat island effect. – Heat released by electrical equipments and air conditioners, and heating systems – heat released by vehicle exhaust Prof. Manju Mohan, IIT Delhi 6 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 7. Urban Heat Island Effect in DelhiProf. Manju Mohan, IIT Delhi 7 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 8. Introduction• Delhi, the capital city of India, has witnessed a consistent decennial population growth at the rate of over 45 % for last six decades.• The corresponding urban infrastructure development is steadily increasing the resource dependency and anthropogenic heat emissions.• Most of the studies on UHI in Delhi were conducted in 1980’s and thus there exists a dearth of recent studies regarding urban climatological assessment in Delhi.Prof. Manju Mohan, IIT Delhi 8 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 9. Land Cover Changes in Delhi: 1997-2008*Land Cover changes for different classes from 1997-2008 (Sq. km in Total area) *Mohan et al, JEP, 2011 Prof. Manju Mohan, IIT Delhi Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 10. Land Cover Changes in Delhi: 1997-2008*• An overall net increase of 251.18 km2 (16.87 %) in built–up area has been observed in last decade.• On the other hand there is a decrease in agricultural area of 146.75 km2 by combining the decrease in crop and fallow land.• There is another significant decrease in wasteland by 80.62 km2 by combining scrub-land and sandy areas.• Area covered by water bodies reduced from 58.26 km2 in 1997 to 27.43 km2 in 2008 which is about 52.9% decrease in a ten year period. *Mohan et al, JEP, 2011 Prof. Manju Mohan, IIT Delhi 10 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 11. Land Cover Changes in Delhi: 1997-2008 contd..• Thus increase in built-up area in the city has been on the expense of majorly from the agricultural and waste land together with the shrinking water bodies.• As the city developed, the built-up category replaced most of the land classes like sandy areas, fallow land and scrub land. The changes in LU- LC classes are more from population pressure as the population growth is very high in Delhi. Prof. Manju Mohan, IIT Delhi 11 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 12. Temperature trends in Delhi*• An increasing trend shows impact of urbanisation in form of increase in built up area.• increasing warming trends in the night-time temperatures reflect the contribution of changing land-use patterns and additional anthropogenic heat. *Mohan et al, JEP, 2011 Prof. Manju Mohan, IIT Delhi Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 13. Temperature trends as proxy to urbanization• The association of increasing temperatures with urbanization was further strengthened by the trends of differences in annual mean minimum temperature of the two stations within the city namely Safdarjung and Palam. Annual Mean Minimum Temperature difference between Safdarjung and Palam during 1968 - 2005• During the 1968-1985, it was Safdarjung which had higher night time temperatures because it was more built up than Palam. After 2000, the two stations had almost the same annual mean minimum temperatures as in subsequent years Palam had also urbanized. Prof. Manju Mohan, IIT Delhi Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 14. Prof. Manju Mohan, IIT Delhi 14 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 15. Delhi: Usual Climate Scenario• Delhi is located at 28.61 °N and 77.23 °E at mean sea level of 216 m.• With a population of 22.4 million and daily influx of about 665 people, the city and its surrounding areas form fourth largest urban agglomeration in the world.• Delhi has four distinct seasons namely: - Summer (March, April, May and June), - Monsoon (July, August and first half of September), - Post Monsoon (October, November) and - Winter (December-February).Prof. Manju Mohan, IIT Delhi 15 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 16. Study Area Network of Delhi (contd..)• The national capital territory of Delhi covering an area of 32 x 32 km was chosen as the study area as shown in Figure• The entire area is divided in 16 major grid cells of 8 x 8 km where at least one ground level station was allocated.• Some of the grids with different land-use type had more than one station so as to get a representation of the terrains therein.• The locations and LULC categories of these stations is depicted in Figure 1.• LULC categories used for location of measurement sites can broadly be classified into Urban Built Up areas, Green Areas, Open Areas and Riverside categories. Prof. Manju Mohan, IIT Delhi 16 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 17. Layout of field measurement points their LULC category in the study area Prof. Manju Mohan, IIT Delhi 17 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 18. Classified Image of Study DomainProf. Manju Mohan, IIT Delhi 18 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 19. Study Area Network of Delhi (contd..)• In all, 30 sites (including 3 weather stations and 27 surface micrometeorological stations) were chosen throughout the city so as to represent a wide variety of land use/land cover categories.• Temperature and humidity measuring instruments were installed at the micrometeorological stations and weather stations were installed at the rooftop and were equipped with instruments used for recording wind speed and direction, dry bulb temperature, relative humidity, atmospheric pressure and direct solar radiation.Prof. Manju Mohan, IIT Delhi 19 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 20. Site ClassificationBuilt Up Area Green Cover Open Area Riverside Dense Urban Canopy Medium Dense Medium Dense Canopy-1 Forests [MDUC I] Medium Dense Canopy- 2 [MDUC II] Less Dense Parks and Canopy GardensProf. Manju Mohan, IIT Delhi 20 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 21. BUILT UP AREASDense Urban Canopy GREEN AREAS •Sitaram Bazar (30) Medium Dense Forests •Bhikaji Cama (7)Medium Dense Urban Canopy •Sanjay Van (24) •Dwarka (6) : MDUC-I Parks & Gardens •Lajpat Nagar (9) : MDUC-I •Hauz Khas Distt Park (28) •Noida Sec-19 (10 ) •Buddha Jayanti Park (8) • Janakpuri (12)-MDUC-I •CP (14): MDUC-I •Kaushambi(16): MDUC-I Micro- OPEN AREAS •Rohini (17) :MDUC-I Meteorological •Adarsh Nagar(19): MDUC-I •IIT (2) •Civil Lines (20): MDUC-I Stations •Loni2 (23) •Neb Sarai (4): MDUC-II •JNU •Moti Nagar (13) : MDUC-II •Vasant Kunj (24): MDUC-II •Chirag Delhi (26) : MDUC-II RIVERSIDE AREAS •Yusuf Sarai (29): MDUC-IILess Dense Urban Canopy •Majnu Ka Tila (11) •Gurgaon,Sec-23(1) •Sailing Club, Jamia Nagar (21) •IIT (2) Prof. Manju Mohan, IIT Delhi 21 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 22. Data Collection and Experiment Description(Indo-Japanese Cooperative Study: IITD, IITR and Meisei University, Japan)* *Mohan et al, ICUC-7, Yokohama, Japan, 2009 Prof. Manju Mohan, IIT Delhi 22 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 23. Experiment Description• Field experiments were carried out during 25-28 May 2008 and were named as DELHI-I.• The month of May is a typical summer month in Delhi.• Temperature and humidity measuring instruments were fixed at all micrometeorological stations. The instruments were installed at a height of about 1.5 m from the ground level such that the ‘immediate’ surroundings of the instrument were open and not obstructed by any tree or building.• These instruments were set facing the South Direction to receive the solar insolation for maximum duration of the day.• In addition, 3 weather stations at the rooftop level (15m approximately) measured wind speed and direction, dry bulb temperature, atmospheric pressure, and global solar radiation. Prof. Manju Mohan, IIT Delhi 23 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 24. Setting Up of Weather Stations Calibration Phase Calibration Set-Up of Micrometeorological InstrumentsProf. Manju Mohan, IIT Delhi 24 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 25. Weather Station installed at a roofProf. Manju Mohan, IIT Delhi 25 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 26. Setting Up of Micrometeorological Instrument at SiteProf. Manju Mohan, IIT Delhi 26 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 27. Loni- Open AreaSitaram Bazar- Dense Urban Canopy Prof. Manju Mohan, IIT Delhi 27 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 28. Green Areas Buddha Jayanti Park Hauz Khas Distt Park Natural Green AreaNatural + Cultivated Green Area (Medium Dense Forest) Prof. Manju Mohan, IIT Delhi 28 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 29. Sailing Club (River Bank) Riverside Areas Majnu Ka Tila (Near River Bank) 29Prof. Manju Mohan, IIT Delhi Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 30. Weather Conditions during the Field Campaign Parameter DELHI-I (25-28 May 2008) Maximum Temperature 33.4 °C -37.2 °C Minimum Temperature 19.6 °C -23.9 °C Wind Speed 0-3.6 ms-1 Wind Direction WNW to SW Rainfall Events 25 May, 26 MayProf. Manju Mohan, IIT Delhi 30 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 31. Results: UHI Intensities in DELHI-I (May 2008)• The dense commercial zone of Cannaught Place-Sitaram Bazar observes higher temperatures on all experimental days.• The heat island effect develops in the order of Cannaught Place- Sitaram Bazar zone > Bhikaji Cama zone> Janakpuri Zone.• The maximum UHI intensity of 8.3 °C was observed at Sitaram Bazar.• All green areas (IIT-Hauz Khas-Sanjay Van and Buddha Jayanti Park) fall under cooler pockets on all the days.• Overall heat island intensity has been found to increase from 25th May to 28th May.• The riverside areas experience higher temperatures than green areas but lower than those of urban canopies in vicinity. Prof. Manju Mohan, IIT Delhi 31 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 32. 32 32 30 30 22 22 28 19 23 Riverside 28 19 23 17 17 Areas 26 26 20 4 20 4 4 .2 24 21 24 21 3 .8 26 27 3 .6 3 .6 22 22 3 .4 3 .2 3 .2 13 13 M M 20 20 3 2 .8 2 .8 18 30 16 18 30 16 2 .6 12 14 2 .4 A A 12 14 2 .4Y (k m ) Y (k m ) 16 16 2 .2 8 2 8 2 14 1 .6 Y Y 14 1 1 .8 .6 12 6 12 6 1 .4 Dense 1 .2 1 .2 10 10 7 7 10 10 1 29 9 11 0 .8 29 9 11 0 .8 8 28 2 26 0 .4 Commercial 8 28 2 26 0 0 .6 .4 25 Areas 25 6 6 0 .2 24 27 0 24 27 0 4 T e m p e ra tu re 4 T e m p e ra tu re 1 4 ( C) 1 4 ( C) 2 2 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 32 X (k m ) UHI contours 32 X (k m ) 30 22 23 (DELHI-I, 30 22 23 May 2008) 28 28 26 17 19 26 17 19 20 20 3:00 am 4 .6 5 .6 24 21 24 21 5 .2 4 .2 22 4 .8 22 3 .8 4 .4 13 13 20 18 30 16 3 .4 3 28 29 20 18 30 16 4 3 .6 12 14 M M 12Y (k m ) 14 Y (k m ) 3 .2 16 2 .6 16 8 8 2 .8 14 2 .2 1 .8 A A 14 2 .4 2 6 Y 12 6 Y 12 1 .6 10 1 .4 10 10 7 10 7 29 9 11 Green 1 .2 1 29 9 11 8 28 8 28 0 .8 2 0 .6 2 26 Areas 26 0 .4 6 25 6 25 24 27 0 .2 24 27 0 4 T e m p e ra tu re 4 T e m p e ra tu re 1 4 ( C) 1 ( C) 2 2 4 32 Prof. Manju Mohan, IIT Delhi 2 4 6 8 10 12 14 16 X (k m ) 18 20 22 24 26 28 30 32 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012 2 4 6 8 10 12 14 16 X (k m ) 18 20 22 24 26 28 30 32
  • 33. Summary Table of Maximum UHI (°C) in DELHI-I Experiments Date Time 3:00 am 9:00 am 3:00 pm 9:00 pm 25 May 2008 - 4.6 6.3 2.8 26 May 2008 4.1 6.4 3.8 5.1 27 May 2008 4.2 5.1 7.6 4.2 28 May 2008 4.6 5.3 6.7 8.3 29 May 2008 5.6 - - -Prof. Manju Mohan, IIT Delhi 33 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 34. The Indian Express, 25 September, 2009Prof. Manju Mohan, IIT Delhi 34 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 35. Prof. Manju Mohan, IIT Delhi 35 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 36. The Hindustan Times, 26 September, 200936
  • 37. 37
  • 38. Comparison with other international megacities• Table 1 shows compilation of some reported UHIs in major cities of the world based on various field observations.• The average maximum daily UHI observed in DELHI-I measurements is comparable to other cities like London, Beijing and Tokyo indicating that urban heat island phenomenon in Delhi is of significant importance as in other megacities of the world.• With increasing urbanization, stronger heat island intensities are expected to be observed here. Prof. Manju Mohan, IIT Delhi 38 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 39. Table 1: UHI of some major megacites of the world Heat Island Remarks City Source Intensity Maximum: 5.4°C UHI in summer 2002New York Gaffin et al (2008) Mean: ~3°C Maximum: 6°C Sarkar and Ridder 12 Day experiment in Paris Mean: 2.56°C (2011) June 2006 Maximum UHI in London 8-9 °C GLA (2006) summer 2003 heat wave episode Wang and Hu Maximum UHI in July Beijing 7.9 °C (2006) 2002 Maximum: 8.1° C Nocturnal UHI in March Tokyo Saitoh et al (1996) Mean: 5.3° C 1992 Maximum 8.2 °C 25-28 May 2008 Delhi DELHI-I Mean: 4.7 °CProf. Manju Mohan, IIT Delhi 39 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 40. Urban Heat Islands: Impacts• Increased energy consumption: – Higher temperatures in summer increase energy demand for cooling and add pressure to the electricity grid during peak periods of demand.• Compromised human health and comfort – Warmer days and nights, along with higher air pollution levels, can contribute to general discomfort, respiratory difficulties, heat cramps and exhaustion, non-fatal heat stroke, and heat-related mortality.• Elevated emissions of air pollutants and greenhouse gases – Increasing energy demand generally results in greater emissions of air pollutants and greenhouse gas emissions from power plants. Higher air temperatures also promote the formation of ground- level ozone. Prof. Manju Mohan, IIT Delhi 40 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 41. Conclusions• The urban heat island effect is prevalent in Delhi and its magnitude has been observed to be of the order of about 8°C.• Maximum UHI was observed at dense residential and commercial area of Sitaram Bazar during nighttime. Other stations with highest UHI were Bhikaji Cama, Connaught Place, and Noida.• Comparison with maximum and average UHI of other cities of the world revealed that UHI in Delhi is comparable to other major cities of the world such as London, Tokyo and Beijing.• More field campaigns at higher spatial resolution and longer duration along with satellite data would provide greater insight . Prof. Manju Mohan, IIT Delhi 41 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 42. Prof. Manju Mohan, IIT Delhi 42 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012
  • 43. References• Mohan M, Pathan SK, Kolli NR, Kandya A, Pandey S. (2011) Dynamics of Urbanization and Its Impact on Land-Use/Land-Cover: A Case Study of Megacity Delhi, J Environ Prot 2: 1274-1283• Mohan M, Kandya A, Battiprolu A (2011) Urban Heat Island Effect over National Capital Region of India: A Study using the Temperature Trends. J Environ Prot 2:465-472.• Mohan M, Kikegawa Y, Gurjar BR, Bhati S, Kandya A, Ogawa K (2009) Assessment of Urban Heat Islands Intensities over Delhi. The Seventh International Conference on Urban Climate (ICUC-7), June 2009, Japan. Prof. Manju Mohan, IIT Delhi 43 Delhi 2050 Workshop, 30 Jan – 3 Feb 2012

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