Seven year satellite observations of the mean structures and variabilities in the regional aerosol distribution over the oceanic areas around the Indian subcontinent

Nair, Sandhya K.; Parameswaran, K.; Rajeev, K.

doi:10.5194/angeo-23-2011-2005

Cited by 34 publications

(47 citation statements)

References 32 publications

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“…The strong contribution from nss-SO 2− 4 was in agreement with previous findings where virtually all nss-SO 2− 4 was likely to have been derived from the marine biogenic source of dimethyl sulfide (Norman et al, 2003). The strong contribution from NaCl, as expected in marine influenced air, was also in agreement with Norman et al (2003).…”

Section: Data Selectionsupporting

confidence: 90%

“…is mainly a contributor of biogenic derived sulfur containing particles and sea salts (Norman et al, 2003). Considering both the source regions and the meteorological situation leads to the election of two time periods being representative for continental influenced air with relatively high light absorption of BC (4 Mm −1 ) and for air with a minimal influence from combustion sources (0.4 Mm −1 ).…”

Section: Data Selectionmentioning

confidence: 99%

“…Mineral dust from the Middle East/Arabian peninsula is transported southwards over the Arabian Sea mixed with anthropogenic influenced aerosol particles from the Indian subcontinent and sea salt before reaching the MCOH (Nair et al, 2005 Fig. 3.…”

Section: Data Selectionmentioning

confidence: 99%

“…The Indian subcontinent is a major source region of anthropogenic emissions from biomass burning and fossil fuel combustion (Reddy et al, 2004;Nair et al, 2005), with the former dominating the BC composition according to C-14 analysis performed at samples from MCOH (Gustafsson et al, 2009). Mineral dust from the Middle East/Arabian peninsula is transported southwards over the Arabian Sea mixed with anthropogenic influenced aerosol particles from the Indian subcontinent and sea salt before reaching the MCOH (Nair et al, 2005 Fig.…”

Section: Data Selectionmentioning

confidence: 99%

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Reducing uncertainties associated with filter-based optical measurements of light absorbing carbon particles with chemical information

Engström

Leck

2011

Atmos. Meas. Tech.

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Abstract. The presented filter-based optical method for determination of soot (light absorbing carbon or Black Carbon, BC) can be implemented in the field under primitive conditions and at low cost. This enables researchers with small economical means to perform monitoring at remote locations, especially in the Asia where it is much needed.One concern when applying filter-based optical measurements of BC is that they suffer from systematic errors due to the light scattering of non-absorbing particles co-deposited on the filter, such as inorganic salts and mineral dust. In addition to an optical correction of the non-absorbing material this study provides a protocol for correction of light scattering based on the chemical quantification of the material, which is a novelty. A newly designed photometer was implemented to measure light transmission on particle accumulating filters, which includes an additional sensor recording backscattered light. The choice of polycarbonate membrane filters avoided high chemical blank values and reduced errors associated with length of the light path through the filter.Two protocols for corrections were applied to aerosol samples collected at the Maldives Climate Observatory Hanimaadhoo during episodes with either continentally influenced air from the Indian/Arabian subcontinents (winter season) or pristine air from the Southern Indian Ocean (summer monsoon). The two ways of correction (optical and chemical) lowered the particle light absorption of BC by 63 to 61 %, respectively, for data from the Arabian Sea sourced group, resulting in median BC absorption coefficients of 4.2 and 3.5 Mm comparison with other studies in the area indicated an overestimation of their BC levels, by up to two orders of magnitude. This raises the necessity for chemical correction protocols on optical filter-based determinations of BC, before even the sign on the radiative forcing based on their effects can be assessed.

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Section: Data Selectionsupporting

confidence: 90%

Section: Data Selectionmentioning

confidence: 99%

Section: Data Selectionmentioning

confidence: 99%

Section: Data Selectionmentioning

confidence: 99%

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Reducing uncertainties associated with filter-based optical measurements of light absorbing carbon particles with chemical information

Engström

Leck

2011

Atmos. Meas. Tech.

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“…This long range transport can modify aerosol properties such as their concentration, size distribution and chemical composition (Jennings and O'Dowd, 1990;Krishnamurti et al, 1998;Moorthy et al, 2005). Observations during the INDOEX (Indian Ocean Experiment, 1998) and the ARMEX-I (in 2001) have shown that the atmosphere over the Arabian Sea is strongly influenced by aerosols from west Asia, Africa and east/south east Asia brought by winds (Moorthy and Saha, 2000;Li and Ramnathan, 2002;Vinoj and Satheesh, 2003;Suresh Babu et al, 2004;Nair et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Validation of MODIS derived aerosol optical depth and an investigation on aerosol transport over the South East Arabian Sea during ARMEX-II

et al. 2009

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Abstract. The influence of wind and humidity on aerosol optical depth (AOD) over the Arabian sea is being investigated using MODIS (Moderate Resolution Imaging Spectroradiometer) Level 3 (Collection-5) and NCEP (National Centres for Environmental Prediction) reanalysis data for the second phase of the Arabian Sea Monsoon Experiment (ARMEX-II) over the South East Arabian Sea (SEAS) in the pre-monsoon period (14 March-10 April 2003). In order to qualify MODIS data for this study, MODIS aerosol parameters were first compared with ship borne Microtops measurements. This showed correlations 0.96-0.97 in the case of spectral AODs and a correlation 0.72 for the angstrom exponents. The daily AOD data from MODIS and winds from NCEP reveal that the ship observed episodic enhancement and decay of AOD at the TSL (Time Series Location) during 23 March-6 April 2003 was caused by the southward drift of an aerosol pocket driven by an intensification and reduction of surface pressure in the North Western Arabian Sea with a low altitude convergence prevailing over SEAS. The AOD increase coincided with a decrease in the Angstrom exponent and the fine mode fraction suggesting the pocket being dominated by coarse mode particles. A partial correlation analysis reveals that the lower altitude wind convergence is the most influential atmospheric variable in modulating AOD over the ARMEX-II domain during the TSL period. However, surface winds at a distant zone in the north/north west upwind direction also had a moderate influence, though with a lag of two days. But this effect was minor since the winds were not strong enough to produce marine aerosols matching with the high AODs over the ARMEX-II domain. These findings and the similarity between MODIS column mass concentration and the ship borne QCM (Quartz Crystal Microbalance) measured coarse mode mass concentration, suggest that the Correspondence to: M. Mohan (mannil mohan@vssc.gov.in) aerosol pocket was mostly composed of coarse mode mineral dust in the lower atmospheric altitudes transported from the Arabian deserts.

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Dust‐induced episodic phytoplankton blooms in the Arabian Sea during winter monsoon

Banerjee

Kumar

2014

JGR Oceans

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Phytoplankton blooms mediated by the oceanic supply of nutrients is a well-understood phenomenon in the Arabian Sea (AS), while the role of dust deposition in enhancing phytoplankton is less explored. In this paper, we show that during winter monsoon the central Arabian Sea (CAS), away from the realm of active winter convection, supports episodic phytoplankton blooms. These blooms cannot be fully explained by the oceanic input of nutrients through processes such as advection and mixing in the upper ocean. Using satellite images, we tracked about 45 dust storms over the AS during the winter monsoons of 2002-2003 to 2010-2011 of which only eight were followed by chlorophyll enhancements. We used a regional climate model to get possible fluxes of dust and the amount of nutrients (nitrate, phosphate, and iron) that can be derived from the dust depositions. Additionally, we used published in situ nutrients data in conjunction with carbon: nitrogen: phosphorus and iron: carbon molar ratios to compute the potential requirements of different nutrients for the eight cases of chlorophyll enhancements. It is likely that the deepening of the mixed layer can incorporate nitrate and phosphate, but not enough iron from the subsurface waters leading to potential iron limitation. Although, all the phytoplankton blooms within CAS were observed following episodic dust events, only four blooms can be attributed to dust depositions. Our work shows that phytoplankton blooms fueled by episodic dust storms are important in driving the interannual variability in chlorophyll in a region away from active winter convection.

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Seven year satellite observations of the mean structures and variabilities in the regional aerosol distribution over the oceanic areas around the Indian subcontinent

Abstract: Abstract. Aerosol distribution over the oceanic regions around the Indian subcontinent and its seasonal and interannual variabilities are studied using the aerosol optical depth (AOD) derived from NOAA-14 and NOAA-16 AVHRR data for the period

Cited by 34 publications

References 32 publications

Reducing uncertainties associated with filter-based optical measurements of light absorbing carbon particles with chemical information

Reducing uncertainties associated with filter-based optical measurements of light absorbing carbon particles with chemical information

Validation of MODIS derived aerosol optical depth and an investigation on aerosol transport over the South East Arabian Sea during ARMEX-II

Dust‐induced episodic phytoplankton blooms in the Arabian Sea during winter monsoon

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