Modelling aerosol dispersion from Indian subcontinent into the oceanic region

Author(s): Apoorva Purohit

After observing the AOD (Aerosol optical depth) patterns measured by MODIS satellite sensors in theArabian sea and Bay of Bengal which decay in radially outward direction fromthe Indian landmass, itwas hypothesized that the AOD distribution pattern in the Arabian sea and Bay of Bengal at large time scales could be captured by using an atmospheric dispersion model considering the Indian subcontinent as a source of aerosol particles which are dispersed nearly equally in all directions into the oceanic region. In order to validate the hypothesis, a dispersion model with emission, advection and deposition was assumed and the broad goal of the current work was to solve it and estimate the AOD distribution inArabian sea and Bay of Bengal. The parameters required for this analysis are: dispersion diffusivity, average wind direction and magnitude, mass extinction efficiencies and source and sink flux’s altitude variation for different aerosols (Black Carbon, Organic Carbon, Sea-salt, sulphate, dust). In this work, the average wind direction and magnitude was identified for the entire Indian subcontinent. The dispersion diffusivity values for eight different Indian locations were calculated at eight altitude levels.Also the average frictionvelocities were estimated and an attempt was made to find the relation between dispersion diffusivity and friction-velocity.With the estimation of source and sink variation with altitude and mass extinction efficiencies of various aerosols, it will be possible to estimate the AOD patterns and validate whether atmospheric dispersion models can capture the aerosol distribution inArabian sea and Bay of Bengal at large time-scales.

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