Aerosol optical properties and radiative forcing over mega-city Karachi

Alam, Khan; Trautmann, Thomas; Blaschke, Thomas

doi:10.1016/j.atmosres.2011.05.007

Cited by 162 publications

(90 citation statements)

References 37 publications

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“…Likewise, in the southern Sindh AODs values greater than 0.98 were reported. Similar increases in AOD during the summer season have previously been reported in other cities of Pakistan (Alam et al, 2010(Alam et al, , 2011a(Alam et al, , b, c, 2012(Alam et al, , 2014(Alam et al, , 2015. In contrast, very low AOD values were observed in almost whole region during the winter season.…”

Section: Seasonal Variations In Aerosol Optical Depth (Aod)supporting

confidence: 63%

Spatio-Temporal Distribution of Aerosol and Cloud Properties over Sindh Using MODIS Satellite Data and a HYSPLIT Model

Sharif

Alam

Afsar

2015

Aerosol Air Qual. Res.

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In this study, aerosols spatial, seasonal and temporal variations over Sindh, Pakistan were analyzed which can lead to variations in the microphysics of clouds as well. All cloud optical properties were analyzed using Moderate Resolution Imaging Spectroradiometer (MODIS) data for 12 years from 2001 to 2013. We also monitored origin and movements of air masses that bring aerosol particles and may be considered as the natural source of aerosol particles in the region. For this purpose, the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to make trajectories of these air masses from their sources. Aerosol optical depth (AOD) high values were observed in summer during the monsoon period (June-August). The highest AOD values in July were recorded ranges from 0.41 to 1.46. In addition, low AOD values were found in winter season (December-February) particularly in December, ranges from 0.16 to 0.69. We then analyzed the relationship between AOD and Ångström exponent that is a good indicator of the size of an aerosol particle. We further described the relationships of AOD and four cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP) by producing regional correlation maps of their data values. The analyses showed negative correlation between AOD and Ångström exponent especially in central and western Sindh. The correlation between AOD and WV was throughout positive with high correlation values > 0.74 in whole Sindh except eastern most arid strip of the Thar Desert in the region. The correlation between AOD and CF was positive in southern Sindh and goes to negative in northern Sindh. AOD showed a positive correlation with CTP and CTT in northern Sindh and a negative correlation in southern Sindh. All these correlations were observed to be dependent on the meteorological conditions for all of the ten sites investigated.

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Section: Seasonal Variations In Aerosol Optical Depth (Aod)supporting

confidence: 63%

Spatio-Temporal Distribution of Aerosol and Cloud Properties over Sindh Using MODIS Satellite Data and a HYSPLIT Model

Sharif

Alam

Afsar

2015

Aerosol Air Qual. Res.

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“…The results obtained in this study also show great differences with respect to those obtained in large polluted cities such as Lahore and Karachi in Pakistan. At these stations the ARF values are around -70 and -19 W m -2 at the SURF and at the TOA, respectively (Alam et al, 2011;Alam et al, 2014). Fig.…”

Section: Aerosol Radiative Forcingmentioning

confidence: 99%

“…where α is Ångstrom Exponent in the wavelength range of 440-870 nm (Alam et al, 2011). The dataset used in this study is composed of cloud-free shortwave irradiance simulated values integrated over the spectral interval 285-2800 nm.…”

Section: Methodsmentioning

confidence: 99%

Thirteen Years of Aerosol Radiative Forcing in Southwestern Iberian Peninsula

Muñoz

Costa

Silva

et al. 2017

Aerosol Air Qual. Res.

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Notable uncertainties in the aerosol impact on the Earth's radiative budget still remain, mainly at local scales. This study aims to accurately quantify the shortwave aerosol radiative forcing (ARF) and its efficiency (ARFE) at Évora (Portugal, Southwestern Europe). This is an interesting region affected by different aerosol types and sources. Towards this goal, ARF and ARFE are calculated for Évora during thirteen years (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015), which is the longest period ever analyzed for this region. For this calculation, the most updated AERONET data have been used to simulate irradiance with the libRadtran code. Thus, 1676 daily values were analyzed, obtaining a mean ARF of -7.4 W m -2 at the Earth's surface (SURF) and -1.1 W m -2 at the top of the atmosphere (TOA), indicating a cooling of the Earth-atmosphere system. The difference in ARF between TOA and SURF indicates a mean net gain of 6.3 W m -2 for the atmosphere. While no ARF seasonal pattern is observed at the TOA, a clear seasonal cycle is detected at the SURF with the most negative values occurring in summer. On the other hand, ARFE shows mean values of -62.7 W m -2 τ -1 at the SURF and -14.3 W m -2 τ -1 at the TOA. Results show that ARFE highly depends on the aerosol single scattering albedo, showing opposite behavior at the SURF and at the TOA. The large temporal variability detected in the aerosol properties in the region of study confirms the general need for long time series of measurements to achieve an accurate estimation of the ARF and ARFE.

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“…Few aerosol studies in Indian subcontinent have reported that aerosols showed high spatial-temporal variations [1], [20]. [16] found maximum AOD during pre-monsoon over Bangladesh and [1] also found highest AOD values during summer seasonsin Pakistan.…”

Section: Introductionmentioning

confidence: 99%

“…MODIS satellite data has been shown to have tremendous efficient for mapping the distribution and properties of aerosols [4]. Aerosol concentrations are regularly increasing especially in Asia due to growing populations, rapid urbanization with consequent land use changes, increasing industrializations and increasing motorized traffic [1]. There are quite sphere of aerosol studies in Bangladesh [16], [17].…”

Section: Introductionmentioning

confidence: 99%

An observational study of aerosol optical properties and their relationships with meteorological parameters over Bangladesh

Mamun¹

2014

IOSRJAGG

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Aerosol optical properties and radiative forcing over mega-city Karachi

Cited by 162 publications

References 37 publications

Spatio-Temporal Distribution of Aerosol and Cloud Properties over Sindh Using MODIS Satellite Data and a HYSPLIT Model

Spatio-Temporal Distribution of Aerosol and Cloud Properties over Sindh Using MODIS Satellite Data and a HYSPLIT Model

Thirteen Years of Aerosol Radiative Forcing in Southwestern Iberian Peninsula

An observational study of aerosol optical properties and their relationships with meteorological parameters over Bangladesh

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