Urban Heat Island Assessment for a Tropical Urban Airshed in India

Abstract

There has been paucity of field campaigns in India in past few decades on the urban heat island intensities (UHI). Remote sensing observations provide useful information on urban heat island intensities and hotspots as supplement or proxy to in-situ surface based measurements. A case study has been undertaken to assess and compare the UHI and hotspots based on in-situ measurements and remote sensing observations as the later method can be used as a proxy in absence of in-situ measurements both spatially and temporally. Capital of India, megacity Delhi has grown by leaps and bounds during past 2 - 3 decades and strongly represents tropical climatic conditions where such studies and field campaigns are practically non-existent. Thus, a field campaign was undertaken during summer, 2008 named DELHI-I (Delhi Experiments to Learn Heat Island Intensity-I) in this megacity. Urban heat island effects were found to be most dominant in areas of dense built up infrastructure and at commercial centers. The heat island intensity (UHI) was observed to be higher in magnitude both during afternoon hours and night hours (maximum up to 8.3?C) similar to some recent studies. The three high ranking urban heat island locations in the city are within commercial and/or densely populated areas. The results of this field campaign when compared with MODIS-Terra data of land surface temperature revealed that UHI hotspots are comparable only during nighttime. During daytime, similar comparison was less satisfactory. Further, available relationship of maximum UHI with population data is applied for the current measurements and discussed in the context of maximum UHI of various other countries

Urban Heat Island and Overheating Characteristics in Sydney, Australia. An Analysis of Multiyear Measurements

“…It is well known that the UHI is better developed under low wind conditions [38]. Several UHI studies in European, Asian and Australian cities have demonstrated that UHI is better developed below a threshold wind speed that depends on the city's characteristics [39][40][41][42]. Strong winds may modify the cooling and heating rates in both the urban and rural environments and decrease the intensity of the UHI phenomenon.…”

Resilience of Outdoor Spaces in an Era of Climate Change: The Problem of Developing Countries

“…Although UHI intensities in tropical and subtropical cities are generally lower than those of temperate cities with comparable populations [18], intensive UHIs are found in cities located in low latitudes [19][20][21][22]. For example, a heat island intensity of up to 8.3 °C was detected in Delhi, India, with the highest magnitude during the afternoon and night hours [23]. The UHI shows a seasonal variation, with lower (higher) intensities during the wet (dry) season [18], indicating its larger effect in the dry season, which is characterized in these latitudes by the highest temperatures.…”

Ilha De Calor Urbana Em Cidade De Pequeno Porte E a Influência De Variáveis Geourbanas

“…Normalmente as maiores intensidades das ilhas de calor tendem a ocorrer em dias sem nebulosidade, e em períodos sem chuvas (ELAGIB, 2011;MOHAN et al, 2012). A água precipitada, no momento que interage com a superfície aquecida, começa o processo de evaporação, liberando calor latente, tornando o ar menos aquecido, portanto, a intensidade da ICU tende a ser menor.…”