Spatio – temporal variations of urban heat island over Delhi

Pandey, Alok Kumar; Singh, Sachchidanand; Berwal, Shivesh; Kumar, Dinesh; Pandey, Puneeta; Prakash, Amit; Lodhi, Neelesh K.; Maithani, Sandeep; Jain, V. K.; Kumar, Krishan

doi:10.1016/j.uclim.2014.10.005

Cited by 60 publications

(24 citation statements)

References 47 publications

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“…The UHI has been the focus in many studies [12] [13] [14] [15] while a significant number of these studies document that cities often remain cooler than the countryside from the early morning until the early afternoon during fair weather and low wind speed conditions. Some earlier studies qualitatively suggest that the UHI may originate from shadow effects in the urban canyon [16], the daytime energy storage in the urban, attenuate the net radiation due to aerosols [17], or the difference in land cover and the available soil moisture altering the surface energy balance.…”

mentioning

confidence: 99%

Seasonal Variation of Urban Heat Island and Its Impact on Air-Quality Using SAFAR Observations at Delhi, India

Aslam¹,

Krishna²,

Beig³

et al. 2017

AJCC

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This paper discussed the urban heat island (UHI) intensity and local air quality by using observational data of project of the System of Air Quality Forecasting and Research (SAFAR) over Delhi during the month of May and December 2013. It is found that UHI magnitudes ~2.2˚C and ~1.5˚C are formed at the evening traffic hours during May and December respectively. Also, intensity of UHI < 0˚C over daytime is referred as Urban Cool Island (UCI) during May and December. The diurnal PM 2.5 concentration shows a bimodal pattern with peaks at morning and evening traffic hours during May and December. The planetary boundary layer height (PBLH) values show higher in magnitude during the daytime and lower in magnitude during the night-time. Whereas, the Ground Heat Flux values are lower during the daytime and higher during the night-time. The wind speed shows lower values during the UHI and higher magnitudes during the UCI formation hours. Concentration of PM 2.5 and wind speed shows a strong negative correlation during May (r = −0.56, p = 0.002) and December (r = −0.57, p = 0.001) at C V Raman (CVR) site, however, high values in the concentration of PM 2.5 during the low wind speed favour the condition for the formation of UCI. The regression analysis indicated that PM 2.5 plays a significant role in the daytime cooling and nighttime warming over the urban areas during the low wind speed condition.

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confidence: 99%

Seasonal Variation of Urban Heat Island and Its Impact on Air-Quality Using SAFAR Observations at Delhi, India

Aslam¹,

Krishna²,

Beig³

et al. 2017

AJCC

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“…Pandithurai et al, 14 reported that AOD at 0.5 mm increases from 0.55 (March) to 1.2 (June) due to dust aerosol over New Delhi during pre-monsoon and a decrease in Angstrom exponent from 1.28 (March) to 0.47 (June) indicating an increased amount of coarse particles due to dust storms from nearby Thar region. Pandey et al 8 reported higher values of AOD confined to the highly built-up areas of Delhi as compared to the surrounding rural region which are pre-dominantly agricultural land. Another important parameter for the high AOD could be the presence of Black Carbon emissions in urban areas 23 .…”

Section: Resultsmentioning

confidence: 99%

“…Solar irradiance plays a major role in governing the climatology of the region in addition to the other above mentioned applications and therefore it is highly important to be investigated as extensively as possible. This region has seen changes in its air quality and climatology such as an increase in temperature over the city compared to the surrounding rural areas by the formation of urban heat islands (UHIs) 8,9 . Also, high temperatures especially during summer season increases the convection and uplifting of dust.…”

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confidence: 99%

Spatial variation of Aerosol Optical Depth and Solar Irradiance over Delhi -NCR during Summer season

Bhardwaj

Pandey

Kumar

et al. 2017

Curr. World Environ

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Present study shows the spatial variation of Aerosol Optical Depth (AOD), solar irradiance and their association at the urban and rural sites in Delhi and National Capital Region (NCR) during the summer season of the year 2015. Summer-time AOD data from the NASA’s Terra satellite MODIS sensor has been used to study the spatial distribution of aerosols over Delhi and its surrounding rural area. The ground data for the direct and global solar irradiances was collected over this region at urban and rural locations in Delhi and NCR using a Fieldspec Spectro-radiometer. HYSPLIT model has been used for the air mass trajectory analysis. The AOD values were observed to be higher over Delhi compared to the relatively lower AOD in rural area of NCR. The NCR site observed higher average solar irradiances than Delhi during the summer season. This may be because of the higher aerosol concentration in Delhi as compared to its outskirts. Also, this region is affected by the severe dust storm events during the summer season which further increases the aerosol load in the atmosphere. HYSPLIT results show the influence of western Thar Desert air masses on the Delhi-NCR. Windblown as well anthropogenic aerosols play a major role in scattering and absorption of the incoming solar radiation and hence, in governing the micro-climatology of the region.

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“…The selected city area was chosen to facilitate the diverse variety of urban features. The complete city can be sub-divided into three major zones like Municipal Corporation of Delhi (MCD), New Delhi Municipal Council (NDMC), and Delhi Cantonment Board (DCB) 35 , 36 . The River Yamuna is a prominent source of water in this area and the city experiences an average annual rainfall of about 61 cm (i.e.…”

Section: Methodsmentioning

confidence: 99%

Urban objects detection from C-band synthetic aperture radar (SAR) satellite images through simulating filter properties

Kumar

2021

Sci Rep

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Satellite-based remote sensing has a key role in the monitoring earth features, but due to flaws like cloud penetration capability and selective duration for remote sensing in traditional remote sensing methods, now the attention has shifted towards the use of alternative methods such as microwave or radar sensing technology. Microwave remote sensing utilizes synthetic aperture radar (SAR) technology for remote sensing and it can operate in all weather conditions. Previous researchers have reported about effects of SAR pre-processing for urban objects detection and mapping. Preparing high accuracy urban maps are critical to disaster planning and response efforts, thus result from this study can help to users on the required pre-processing steps and its effects. Owing to the induced errors (such as calibration, geometric, speckle noise) in the radar images, these images are affected by several distortions, therefore these distortions need to be processed before any applications, as it causes issues in image interpretation and these can destroy valuable information about shapes, size, pattern and tone of various desired objects. The present work aims to utilize the sentinel-1 SAR datasets for urban studies (i.e. urban object detection through simulation of filter properties). The work uses C-band SAR datasets acquired from Sentinel-1A/B sensor, and the Google Earth datasets to validate the recognized objects. It was observed that the Refined-Lee filter performed well to provide detailed information about the various urban objects. It was established that the attempted approach cannot be generalised as one suitable method for sensing or identifying accurate urban objects from the C-band SAR images. Hence some more datasets in different polarisation combinations are required to be attempted.

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Spatio – temporal variations of urban heat island over Delhi

Cited by 60 publications

References 47 publications

Seasonal Variation of Urban Heat Island and Its Impact on Air-Quality Using SAFAR Observations at Delhi, India

Seasonal Variation of Urban Heat Island and Its Impact on Air-Quality Using SAFAR Observations at Delhi, India

Spatial variation of Aerosol Optical Depth and Solar Irradiance over Delhi -NCR during Summer season

Urban objects detection from C-band synthetic aperture radar (SAR) satellite images through simulating filter properties

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