Tropospheric distribution of sulphate aerosols mass and number concentration during INDOEX-IFP and its transport over the Indian Ocean: a GCM study S. Verma1,*, O. Boucher2, M. Shekar Reddy2, H. C. Upadhyaya1, P. Le Van3, F. S. Binkowski4, and O. P. Sharma1 1Centre for Atmospheric Sciences, Indian Institute of Technology Delhi, New Delhi, India 2Laboratoire d'Optique Atmosphérique, CNRS/Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France 3Laboratoire de Météorologie Dynamique Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France 4Environmental Science and Engineering, University of North Carolina, Chapel Hill, USA *now at: Centre of Excellence in Climatology, Birla Institute of Technology (BIT) Mesra, Extn Centre Jaipur, Rajasthan, India
Abstract. The sulphate aerosols mass and number concentration during the Indian Ocean
Experiment (INDOEX) Intensive Field Phase-1999 (INDOEX-IFP) has been
simulated using an interactive chemistry GCM. The model considers an
interactive scheme for feedback from chemistry to meteorology with internally
resolving microphysical properties of aerosols. In particular, the
interactive scheme has the ability to predict both particle mass and number
concentration for the Aitken and accumulation modes as prognostic variables.
On the basis of size distribution retrieved from the observations made along
the cruise route during IFP-1999, the model successfully simulates the order
of magnitude of aerosol number concentration. The results show the southward
migration of minimum concentrations, which follows ITCZ (Inter Tropical
Convergence Zone) migration. Sulphate surface concentration during INDOEX-IFP
at Kaashidhoo (73.46° E, 4.96° N) gives an agreement within a
factor of 2 to 3. The measured aerosol optical depth (AOD) from all aerosol
species at KCO was 0.37 ± 0.11 while the model simulated sulphate AOD
ranged from 0.05 to 0.11. As sulphate constitutes 29% of the observed AOD,
the model predicted values of sulphate AOD are hence fairly close to the
measured values. The model thus has capability to predict the vertically
integrated column sulphate burden. Furthermore, the model results indicate
Indian contribution to the estimated
sulphate burden over India is more than 60% with values upto 40% over
the Arabian Sea.
Citation: Verma, S., Boucher, O., Shekar Reddy, M., Upadhyaya, H. C., Le Van, P., Binkowski, F. S., and Sharma, O. P.: Tropospheric distribution of sulphate aerosols mass and number concentration during INDOEX-IFP and its transport over the Indian Ocean: a GCM study, Atmos. Chem. Phys., 12, 6185-6196, doi:10.5194/acp-12-6185-2012, 2012.