Multi-year investigations of aerosols from an island station, Port Blair, in the Bay of Bengal: climatology and source impacts

Abstract

Abstract. Long-term measurements of spectral aerosol optical depth (AOD) using multi-wavelength solar radiometer (MWR) for a period of seven years (from 2002 to 2008) from the island location, Port Blair (11.63 • N, 92.7 • E, PBR) in the Bay of Bengal (BoB), along with the concurrent measurements of the size distribution of near-surface aerosols, have been analyzed to delineate the climatological features of aerosols over eastern BoB. In order to identity the contribution of different aerosol types from distinct sources, concentration weighted trajectory (CWT) analysis has been employed. Climatologically, AODs increase from January to reach peak value of ∼0.4 (at 500 nm) in March, followed by a weak decrease towards May. Over this general pattern, significant modulations of intra-seasonal time scales, caused by the changes in the relative strength of distinctively different sources, are noticed. The derivative (α ) of the Angstrom wavelength exponent α in the wavelength domain, along with CWT analysis, are used to delineate the different important aerosol types that influence this remote island. Corresponding changes in the aerosol size distributions are inferred from the numerical inversion of the spectral AODs as well from (surface) measurements. The analyses revealed that advection plays a major role in modifying the aerosol properties over the remote island location, the potential sources contributing to the accumulation mode (coarse mode) aerosols over eastern BoB being the East Asia and South China regions (Indian mainland and the oceanic regions).

Quantitative assessment of AOD from 17 CMIP5 models based on satellite-derived AOD over India

“…5c) is consistent with ground-based observations. The role of low AOD over the Arabian Sea and Bay of Bengal in producing the latitudinal and longitudinal variation in AOD observed in our study is corroborated by the studies of Vinoj et al (2008) and Naseema Beegum et al (2012). Vi- In order to further explore the model-satellite comparison, we examined the correlation coefficients of some of the models: IPSL-CM5A-MR (Dufresne et al, 2013), CSIRO-BOM-ACCESS1.0 (Bi et al, 2013), NOAA-GFDL-ESM2M, NOAA-GFDL-ESM2G (Dunne et al, 2012), MIROC-MIROC5 (Watanabe et al, 2010), MRI-CGCM3 (Yukimoto et al, 2012), NCC-NorESM1-M , NCC-NorESM1-ME (Tjiputra et al, 2013) over selected regions (Fig.…”

Aerosol characterization at the Saharan AERONET site Tamanrasset

“…A similar approach to connect distinct sources with different aerosol types has been previously performed by other authors (e.g. Naseema Beegum et al, 2012). A weighted AOD or AE value is assigned to each grid cell by averaging the values associated with the trajectories crossing that grid cell:…”