Characteristics of aerosols over Hyderabad in southern Peninsular India: synergy in the classification techniques

Abstract

Abstract. The present study focuses on analyzing the seasonal changes in aerosol characteristics using a classification scheme proposed by Gobbi et al. (2007). This scheme is based on the correlation between theÅngström exponent (α) in the 440-870 nm range and the difference in α values [dα = α (440-675 − α(675-870)] including the size of finemode particles (R f ) and the fine-mode fraction (η). The classification scheme can therefore provide information on the aerosol characteristics and their modification in transit. Spectral aerosol measurements using the Microtops-II sun photometer (MT-II) have systematically been conducted in Hyderabad, India during April 2009-March 2010 and analysed to study the seasonal effects. The results reveal a seasonal dependence, i.e. the presence of fine-mode aerosols under turbid atmospheres in winter and post-monsoon, a mixture of fine and coarse aerosol types in pre-monsoon and a significant influence of marine mixed with dust air masses during the monsoon season. The identification of the aerosol source type and the modification processes are discussed along with clustered air-mass trajectory analysis. Furthermore, we have also checked the consistency of this scheme with the findings arrived from the columnar size distributions (CSDs) computed by numerical inversion of spectral AOD using King's inversion algorithm and the scatter plot between AOD and spectral α. The comparison clearly demonstrates the usefulness of the classification scheme and highlights its advantages for the monitoring and study of seasonal variation of the aerosol types and the modification processes in the atmosphere.

Role of Coarse and Fine Mode Aerosols in MODIS AOD Retrieval: a case study over southern India

“…The volume sizedistribution is found to be predominantly bi-modal for most seasons with a clear dip between the two modes. Sinha et al (2012) have studied aerosol size distribution from Hyderabad (17.47 • N, 78.58 • E) -a major city in southern India and have also reported bi-modal size distribution using hand-held sun-photometer. The size distribution should be ideally split into two parts from centre of the dip.…”

“…Location of Gadanki is shown with a white star on the map. Air-masses coming from the northeastern direction via the Bay of Bengal are expected to be rich in anthropogenic aerosols whereas the air-masses coming from the Indian Ocean are expected to be rich in natural aerosols (Corrigan et al, 2006;Jayaraman et al, 2006;Suresh Babu et al, 2007;Rajeev et al, 2010).…”

“…Hence the ability to differentiate particles with respect to their size can provide a mean to quantify the influence of human activities on the abundance of atmospheric aerosols. Separating contributions from smaller and bigger particles in aerosol optical depth (AOD) is a step forward in this direction and can serve as a proxy to study many of the effects discussed above (Kosmopoulos et al, 2008;Lee et al, 2010;Kaskaoutis et al, 2012;Sinha et al, 2012).…”

Identification and Classification of Different Aerosol Types over a Subtropical Rural Site in Mpumalanga, South Africa: Seasonal Variations as Retrieved from the AERONET Sunphotometer

“…The same scheme was performed over Skukuza (South Africa), a subtropical rural site, with the initiation of earlier researchers (Gobbi et al, 2007;Basart et al, 2009) who reported in their work to explore information about aerosol types over this site. Recently, it has been applied over oceanic environment during ICARB in summer (Arabian Sea) (Kaskaoutis et al, 2010), W-ICARB in winter (Bay of Bengal) (Kaskaoutis et al, 2011), while over different urban environments of Athens by means of MFR data (Gerasopoulos et al, 2011) and over Hyderabad from MICROTOPS II Sunphotometer observations (Sinha et al, 2012). Gobbi et al (2007) used only cases of AOD > 0.15 from eight different AERONET stations in three continents to avoid errors larger than ~30%.…”

Synergistic Approach for the Aerosol Monitoring and Identification of Types over Indo-Gangetic Basin in Pre-Monsoon Season

“…have studied the aerosol type discrimination (e.g., polluted continental, polluted dust, non-absorbing aerosols) using fine mode fraction (FMF) of AOD and single scattering albedo (SSA), which reveals higher contribution of polluted dust over Kanpur, while the polluted continental and carbonaceous aerosols dominate over Gandhi College (eastern IGB) during the PrM period. Recently, aerosol classifications were reported using the relationship between AE 440-870 and the difference in AE [Δ AE = AE 440-675 -AE ] including the FMF over a southern city (Hyderabad) of India (Sinha et al, 2012). Pathak et al (2012) have classified five different categories (viz.…”