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The variability of aerosol optical thickness (AOT) in the tropical Indian Ocean (IO) and South China Sea (SCS) during the intermonsoon (February-May) is investigated using shipboard and satellite data from 2011 to 2014, in order to understand the mechanism controlling AOT production and transport. Overall AOT in tropical IO is significantly smaller than those in SCS, and a strong intraseasonal variability of AOT, along with significant dependence on wind speed (especially when <8 m s−1), is observed in both basins. Our analysis showed that in tropical IO, aerosols are mostly of natural marine production in spring, and the AOT shows greater dependence on the higher wind speeds in May, while in SCS, AOT dependence on wind speed increases when the prevailing wind turns from offshore (February, March) to onshore (April, May), due to less transport of terrestrial dust and anthropogenic aerosols from land. A better agreement between shipboard and once-daily satellite AOT is observed in the Equatorial belt (5° S-5° N, i.e. remote areas of IO) than in the Non-Equatorial area (5° N-25° N), and can be explained by the overall lower AOT values and the smaller diurnal variation in the Equatorial belt. Changes of wind regime during the monsoon evolution and the consequent transport of land-based aerosols reduce AOT dependence on wind speed and are the major drivers for the AOT variability. [ABSTRACT FROM AUTHOR]

This study analysed the spatio-temporal distributions of chlorophyll-a (chl-a) in the Indian Ocean during the 2004 South Asian tsunami and the effects of four variables (sea surface temperature, normalized water-leaving radiance, rainfall and wind speed) on chl-a distributions during the tsunami, using satellite data and spatial models. The results showed considerable variations in the spatio-temporal distributions of chl-a, and the effects of the four variables on chl-a around the tsunami. The results revealed that sea surface temperature and rainfall had negative effects on chl-a, while normalized water-leaving radiance and wind speed had positive effects. The effects of all the four explanatory variables were significant (positive or negative) before the tsunami. Except normalized water-leaving radiance, the other three variables all showed certain degrees of weakened effects on chl-a after the tsunami, which suggested the physical disturbance of the tsunami on the effects of these variables on chl-a distribution. [ABSTRACT FROM AUTHOR]

Abstract: The effects of rainfall and wind speed on the dynamics of suspended sediment concentration (SSC), during the 2004 Indian Ocean tsunami, were analyzed using spatial statistical models. The results showed a positive effect of wind speed on SSC, and inconsistent effects (positive and negative) of rainfall on SSC. The effects of wind speed and rainfall on SSC weakened immediately around the tsunami, indicating tsunami-caused floods and earthquake-induced shaking may have suddenly disturbed the ocean–atmosphere interaction processes, and thus weakened the effects of wind speed and rainfall on SSC. Wind speed and rainfall increased markedly, and reached their maximum values immediately after the tsunami week. Rainfall at this particular week exceeded twice the average for the same period over the previous 4years. The tsunami-affected air–sea interactions may have increased both wind speed and rainfall immediately after the tsunami week, which directly lead to the variations in SSC. [Copyright &y& Elsevier]

Abstract: The Sumatra tsunami on 26 December, 2004 in the Indian Ocean was generated by one of the largest earthquakes of the past 100 years. The present study investigated spatial and temporal changes of suspended sediment concentration (SSC) in North-East Indian Ocean (NEIO) after the Sumatra tsunami used satellite remote sensing data. The nLw551 products of MODIS-aqua data (using as indexing SSC) were analyzed for 5 years (2002–2006). Result shows SSC notably increased (55.6–200%) in large river estuaries along coast of the Bay of Bengal (BOB) in a short time (4 weeks) after the tsunami, especially the northwest coast of Indonesia, southeast coast of Myanmar, as well as the north offshore of BOB. Those increases were mainly caused by the re-suspension function induced by the initial surge of the tsunami. Monthly analysis indicates increases (4.26%) of SSC of the entire North-East Indian Ocean area in 2005; especially in November 2005 when increase of SSC increased by about 6.19% compared with other years; those may mainly be caused by the destruction of coastal vegetation and modifying of estuaries or wetlands by the 2004 tsunami. The increases of SSC have different mechanism in different region and period after the tsunami. [Copyright &y& Elsevier]