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

Fozia Sharif,Sheeba Afsar,Khan Alam

doi:10.4209/aaqr.2014.09.0200

Fozia Sharif, Sheeba Afsar + Show 1 more

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https://doi.org/10.4209/aaqr.2014.09.0200

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Abstract

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.

Highlights

Aerosols are minute solid and liquid particles suspended in the atmosphere
We further described the relationships of Aerosol optical depth (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
AOD spatial and temporal distributions were analyzed through the use of the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data

Summary

Introduction

Aerosols are minute solid and liquid particles suspended in the atmosphere. These may occur in the form of natural dust particles, volcanic dust, mist, clouds, fog, sea salts, anthropogenic aerosols, oceanic sulphates, industrial sulphates, soot (Black carbon), organic particles and some toxic pollutants after various physical and chemical processes that have several effects on our atmosphere ( Gupta et al, 2013).Interactions between aerosols and clouds have become a key topic of scientific research due to the importance of clouds in controlling climate (Mahowald and Kiehl, 2003; Alam et al, 2010, 2014). Aerosols are minute solid and liquid particles suspended in the atmosphere. These may occur in the form of natural dust particles, volcanic dust, mist, clouds, fog, sea salts, anthropogenic aerosols, oceanic sulphates, industrial sulphates, soot (Black carbon), organic particles and some toxic pollutants after various physical and chemical processes that have several effects on our atmosphere ( Gupta et al, 2013). Increasing anthropogenic aerosol concentrations lead to form cloud condensation nuclei (CCN) that ranges from smaller effective radii to longer-lived clouds, affecting the hydrological cycle (Ramanathan et al, 2001; Balakrishnaiah et al, 2012). A wide range of studies has shown aerosol and cloud interactions with large uncertainties in the magnitude of radiative forcing (e.g., Twomey et al, 1984; Coakley et al, 1987; Kaufman and Nakajima, 1993; Kaufman and Fraser, 1997a, b; Ackerman et al, 2000; Rosenfeld, 2000; Ramanathan et al, 2001; Rosenfeld et al, 2002; Schwartz et al, 2002; Kim et al, 2003; Andreae et al, 2004; Koren et al, 2004; Penner et al, 2004; Kaufman et al, 2005; Koren et al, 2005; Alam et al, 2010; Balakrishnaiah, 2012; Alam et al, 2014)

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