title: Atmospheric aerosol radiative forcing over a semi-continental location Tripura in North-East India: Model results and ground observations.
abstract: Northeast India (NEI) is located within the boundary of the great Himalayas in the north and the Bay of Bengal (BoB) in the southwest, experiences the mixed influence of the westerly dust advection from the Indian desert, anthropogenic aerosols from the highly polluted Indo-Gangetic Plains (IGP) and marine aerosols from BoB. The present study deals with the estimation and characterization of aerosol radiative forcing over a semi-continental site Tripura, which is a strategic location in the western part of NEI having close proximity to the outflow of the IGP. Continuous long term measurements of aerosol black carbon (BC) mass concentrations and columnar aerosol optical depth (AOD) are used for the estimation of aerosol radiative forcing in each monthly time scale. The study revealed that the surface forcing due to aerosols was higher during both winter and pre-monsoon seasons, having comparable values of 32W/m2and 33.45W/m2respectively. The atmospheric forcing was also higher during these months due to increased columnar aerosol loadings (higher AOD ~0.71) shared by abundant BC concentrations (SSA ~0.7); while atmospheric forcing decreased in monsoon due to reduced magnitude of BC (SSA ~0.94 in July) as well as columnar AOD. The top of the atmosphere (TOA) forcing is positive in pre-monsoon and monsoon months with the highest positive value of 3.78W/m2in June 2012. The results are discussed in light of seasonal source impact and transport pathways from adjacent regions.
authors.affiliation: Department of Physics, Tripura University, Suryamaninagar 799022, India.
authors.forename: Pranab
authors.initials: P
authors.lastname: Dhar
authors.affiliation: Department of Physics, Tripura University, Suryamaninagar 799022, India.
authors.forename: Barin Kumar
authors.initials: BK
authors.lastname: De
authors.affiliation: Department of Physics, Tripura University, Suryamaninagar 799022, India.
authors.forename: Trisanu
authors.initials: T
authors.lastname: Banik
authors.affiliation: Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022, India.
authors.forename: Mukunda M
authors.initials: MM
authors.lastname: Gogoi
authors.affiliation: Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022, India.
authors.forename: S Suresh
authors.initials: SS
authors.lastname: Babu
authors.affiliation: Department of Physics, Tripura University, Suryamaninagar 799022, India. Electronic address: anirban1001@yahoo.com.
authors.forename: Anirban
authors.initials: A
authors.lastname: Guha
keywords: Aerosol optical depth; Aerosol radiative forcing; Black carbon concentration; Single scattering albedo