Distribution of ozone and its precursors over Bay of Bengal during winter 2009: role of meteorology

Abstract

Abstract. Measurements of ozone and NO 2 were carried out in the marine environment of the Bay of Bengal (BoB) during the winter months, December 2008-January 2009, as part of the second Integrated Campaign for Aerosols, gases and Radiation Budget conducted under the Geosphere Biosphere Programme of the Indian Space Research Organization. The ozone mixing ratio was found to be high in the head and the southeast BoB with a mean value of 61 ± 7 ppb and 53 ± 6 ppb, respectively. The mixing ratios of NO 2 and CO were also relatively high in these regions. The spatial patterns were examined in the light of airflow patterns, air mass back trajectories and other meteorological conditions and satellite retrieved maps of tropospheric ozone, NO 2 , CO, and fire count in and around the region. The distribution of these gases was strongly associated with the transport from the adjoining land mass. The anthropogenic activities and forest fires/biomass burning over the Indo Gangetic Plains and other East Asian regions contribute to ozone and its precursors over the BoB. Similarity in the spatial pattern suggests that their source regions could be more or less the same. Most of the diurnal patterns showed decrease of the ozone mixing ratio during noon/afternoon followed by a nighttime increase and a morning high. Over this oceanic region, photochemical production of ozone involving NO 2 was not very active. Water vapour played a major role in controlling the variation of ozone. An attempt is made to simulate ozone level over the north and south BoB using the photochemical box model (NCAR-MM). The present observed features were compared with those measured during the earlier cruises conducted in different seasons.

Hygroscopic growth of particles nebulized from water-soluble extracts of PM2.5 aerosols over the Bay of Bengal: Influence of heterogeneity in air masses and formation pathways

“…4 also depicts the significant higher values in the mass fractions of WSOM, total WSM, and g(90%) WSM over the northern BoB. In contrast, mass fractions of K + showed higher values over the southern BoB, probably due to the dominant fire counts associated with SEA air masses (David et al, 2011). However, we couldn't find any significant difference between the northern and southern BoB in the mass fractions of NH 4 + and SO 4 2− .…”

“…In contrast, lower g(90%) WSM values were observed over the southern BoB, influenced by aged SEA air masses, which were also influenced by biomass burning (David et al, 2011). It is important to emphasize that lower growth factors over the southern BoB indicate that these particles were composed of low soluble inorganic and organic salts.…”

“…Moorthy et al (2010) reported high values of aerosol optical depth (AOD); Srinivas and Sarin (2013) observed high abundance of water-soluble organic carbon over the northern BoB when air masses are associated with the IGP during the same cruise. David et al (2011) reported higher mixing ratios of surface ozone and its precursor gases such as NO 2 and CO over the northern BoB, where the air masses are associated with the IGP owing to the advection from the IGP/Bangladesh whereas lower mixing ratios were observed in the southern BoB from the same cruise. In addition to this study, we present MODIS satellite images of aerosol optical depth (AOD@550 nm) and cloud condensation nuclei number concentrations (CCN_Ocean, CCN/cm 2 ) over the BoB during the cruise period (Dec, 08 to Jan., 09) in Fig.…”

Winter time chemical characteristics of aerosols over the Bay of Bengal: continental influence

“…This analysis again highlights the intense pollution of North-BoB and moderate pollution over SE-BoB by continental aerosols. While the trace gases like O 3 , CO showed higher mixing ratio over N-BoB and SE-BoB (David et al 2011), aerosol loading over SE-BoB (55±9 μg m −3 ) was lower than that over N-BoB (88±26 μg m −3 ).…”

In situ measured seasonal characteristics of near‐surface aerosols over Bay of Bengal and MODIS‐retrieved columnar properties: A multicampaign analysis

“…The high concentrations of oceanic species like Na, Cl − , and Mg over these regions confirm this source. The presence of K over middle and south BoB is due to the air mass flow from the landmass on the eastern side of BoB (Figure c), where biomass burning is strong as revealed by MODIS‐retrieved fire counts [ David et al ., ]. More details on the role of air mass trajectories in establishing transport pathways of aerosols and trace gases over BoB during premonsoon and winter are discussed elsewhere [ Nair et al ., ; David et al ., ; Girach and Nair , ; Aryasree et al ., ].…”