Critical review of the Climate Change Impact on urban areas by assessment of Heat Island effect Case of Pune, India Town Planning, Civil Department Prof. Omkar Parishwad, [email protected] Climate Change Impact on Urban Areas • The Intergovernmental Panel on Climate Change (IPCC) had indicated that ‘observed warming has been, and transient greenhouse-induced warming is expected to be, greater over land than over the oceans’. • Impact of Urbanization: Over the past 35 years, more than 20,000 people have died of heat- related causes in Indian megacities. Statistics show reported deaths due to such heat waves in urban parts of India. 2500 Source: National 1247 1216 1165 Disaster 793 Management Annual surface air temperature increase Authority, Heat Wave; ndma.gov.in 2011 2012 2013 2014 2015 Urban Heat Island Effect.. • Urban Heat Islands (UHIs) develop as heat is emitted from a range of built-up surfaces, under favorable meteorological conditions (i.e. direction and velocity of wind, low water vapor content, etc.). • Urban heat islands have a direct impact on human health and urban energy consumption patterns. • Studies also indicate global urban population (which is over 50% of the total population) per capita energy usage for operating cooling systems, to be over 3 times than the rural dwellers. Source: Understanding UHI’s, Lahore Conservation Society Case Study: Pune (PMC), India • Pune a historically and strategically prominent city with a biodiverse climate (being near to Western Ghat region). • Latitude: 18°37’30" N- 18°24’30" N, • Longitude: 73°45’30" E - 73°58’30" E • Altitude: 550-1000m (1,840 ft) above sea level • Pune Municipal Corp. Area: 243.80 sq.km • Population: 31,15,454 (Census 2011) and is the 9th largest city in India. • Seasons: Summer (March – May; 25 ° to 39°C) Monsoon and Winter (November to February;. 6° - 28 ° C). Average rainfall is about 62.5 cm. • In short, the weather is Clear and Sub-tropical. Figure 1. PMC Study Area (Contour Map) Methodology for the Research • A study -Thapliyal and Kulshreshtha, 1991; on temperature trends in Pune indicates a slight warming between 1901 - 1990, using manual surveying. • Gadgil and Dhorde, 2005 studied temporal variations in temperature over Pune city, during the period 1901- 2000 showing significant decrease in annual average and maximum temperatures, ascribing to a significant increase in the amount of suspended particulate matter (SPM) in its ambient temperature. Satellite Data Acquisition Temporal • LandSAT 7 ETM+ imagery results (available Sensors Spatial Resolution Resolution for free download) were compared with One cycle per GOES 4 km LandSAT 8 (OLI/TIRS) imagery for its day Daily 8 days, MODIS 1km, 5km, 0.05 degree accuracy. It made sense to compromise on monthly spatial resolution while acquiring thermal LandSAT7 ETM+ Resampled to 30m(60) 16 days data for better signal to noise ratio (SNR). 30 m (OLI), 100m LandSAT 8 16 days • LandSAT 8 imagery was available for free (TIRS) ASTER 90m 16 days download since 1 January, 2017. The image AVHRR 1.099km 24 days quality (9) and thermal band accuracy, SVISSR 1.25km 4 years 4 km ground produce motivating results; imagery available VHRR (INSAT 3D) 26 minutes resolution after March 2013. LandSAT 7 ETM+ imagery VHRR (Kalpana) 2 km 35 days available after August 1999. Table 1: Available thermal sensors and their specifications Satellite Data Processing Land Cover Analysis LandSAT 7/8 Satellite imagery for 2001 & 2016 (Summer (April) and Winter (January), as per Pune’s season’s) is acquired for analyzing the increase in Urban Green Cover Change Detection and interrelating the heat island effect with climate change factors. NDVI = (RNIR – RRED) / (RNIR+RRED) R Near InfraRed (NIR) band (0.722- 0.898 μm) NIR Land Use NDVI RRED Red band (0.631 – 0.692 μm) Water Bodies -0.070 Barren Land 0.027 Built Area 0.107 Table 2: Generic NDVI values for Sparse Vegetation 0.320 specific land covers Dense Vegetation 0.425 Land Surface Temperature Estimation • Radiant (brightness) temperature can be estimated on the basis of DN values for pixels of thermal bands of LandSAT imagery. • For LandSAT 8, TIRS and OLI band data are converted to top of atmosphere (TOA) spectral radiance using the radiance rescaling factors. • Land Surface emissivity is then calculated for both LandSAT (7/8) imagery, using NDVI and proportion of emissivity • Correlating emissivity by calibration constants, effective Land Surface temperature (LST) is computed. • LST relating to the ambient temperature, in the imagery are computed spatially for concluding on the specto-temporal variations in temperatures in summer and winter for 2001 & 2016 LandSAT (7/8) imagery. NDVI and Land Surface Temperature April 2001 April correlations for correlations Summer Analysis of imagery obtained from LandSAT 7 ETM+ from USGS (SLC-on) NASA Land Processes Distributed Active Archive Center (LP DAAC) Products NDVI and Land Surface Temperature April 2016 April correlations for for correlations Summer Analysis of imagery obtained from LandSAT 8 OLI/TIRS from USGS, NASA Land Processes Distributed Active Archive Center (LP DAAC) Products NDVI and Land Surface Temperature Analysis of imagery obtained from LandSAT 7 ETM+ from USGS (SLC-on) NASA Land Winter correlations for January2001 for correlations Winter Processes Distributed Active Archive Center (LP DAAC) Products NDVI and Land Surface Temperature Analysis of imagery obtained from LandSAT 8 OLI/TIRS from USGS, NASA Land Winter correlations for January2016 for correlations Winter Processes Distributed Active Archive Center (LP DAAC) Products Change Detection analysis for the NDVI and LST Maps NDVI change detection give specific results regarding increase or simultaneous decrease in the classified land covers viz. Water Bodies, Barren Land, Built Area, Sparse Vegetation, and Dense Vegetation or Agriculture land. The change detection results indicate that the built up area have increased considerably with respect to the green cover and vegetation. Open spaces too have reduced, as have the water bodies. Land Cover 2001 2016 Change Table 3: Change Area % Area % Area % detection in Land (sq.km.) (sq.km.) (sq.km.) Cover Area Water 2.00 0.62 1.70 0.52 -0.32 -0.10 (2001-2016) Barren land 100.80 31.30 105.00 32.60 4.19 1.30 Built Up 97.60 30.30 108.90 33.80 11.28 3.50 Sparse Vegetation 65.70 20.40 57.60 17.88 -8.12 -2.52 Dense Vegetation 56.00 17.38 49.00 15.20 -7.02 -2.18 Total area 322.20 100.00 322.20 100.00 Correlation regression analysis for accuracy assessment • Normalized Difference Vegetation Index (NDVI) is inversely proportional to Land Surface Temperature (LST). In both the seasons the LST values decreases with increasing NDVI values. However, the coefficient of determination (R2) is more for summer. • The allied reason for LST to be more dominant 50 46 and leading to UHI effect in summer is the 41 40 38 33 33 already high atmospheric temperature. The 30 27 difference in slope for trends quantify the 24 24 20 20 13 prominence of this cooling effect. 10 • The cooling effect reduces as a logarithmic 0 function to distance from the green space. 0 20 40 60 80 100 120 Normalized Difference Vegetation Index (NDVI) This spatial autocorrelation seems to extend up Surface LandTemperature (LST) to 4 km in direct proportion with the area and LST Winter LST Summer green index of the open space and water. Linear ( LST Winter) Linear (LST Summer) Climate Change Analysis for LST over Common Land Cover Apr-01 Apr-16 • The average change in the LST SUMMER 80 38.1 from 2001 to 2016 for summer and 32.4 60 28.82 30.75 28.1 winter seasons is shown in the 40 29.9 35.8 29.36 graphs. 20 25.36 26.36 • It is clear that the rise in average 0 Water Barren Built Up Sparse Dense LST is observed majorly over body Land Vegetation Vegetation barren land and built up. • Thus, over a period of 15 years Jan-01 Jan-16 WINTER the rise in Land Surface 60.0 29.2 25.9 Temperature is higher in areas 40.0 21.3 21.9 20.8 25.9 where there is more built-up and 20.0 19.8 22.8 20.4 19.2 barren land which ultimately 0.0 relates to the reduced green Water Barren Built Up Sparse Dense cover in these areas. body Land Vegetation Vegetation Climate Change? Yes! Heat Island effect?? • LST in summer varies more as compared Average difference to winter as the dense cover decreases. Green cover is more in winter due to earlier LULC Classes in LST (2001 – 2016) monsoon rains. While the green cover Summer Winter decreases more in Summer. Thus, heat Water Bodies 1.3 °C 1.6°C Island effect seems more prominent in Barren Land 2.9°C 3.1°C Summer. Built Areas 3.9°C 3.4°C • In the core areas of Pune, the temp is Sparse Vegetation 1.45°C 1.5°C interestingly low, which does not relate Dense Vegetation 1.74°C 1.6°C Pune area with most of the western cases Table 4: Temperature differences for LULC for Urban Heat Island effect. (2001-2016) • As the outskirts or border areas of the city show elevated temperatures than the core areas of the city, should it be concluded that we have no heat island effect? Inferences • The Vernacular City Pattern- dissipating heat by obstructing and circulating winds • The built materials used in the core city are stone and other natural materials, instead of concrete, asphalt. • The Indian cities have a considerably low rise pattern in its core and high rise concrete pattern in its newly developed areas in its fringe areas.