title: Direct radiative forcing properties of atmospheric aerosols over semi-arid region, Anantapur in India.
abstract: This paper describes the aerosols optical, physical characteristics and the aerosol radiative forcing pertaining to semi-arid region, Anantapur for the period January 2013-December 2014. Collocated measurements of Aerosol Optical Depth (AOD) and Black Carbon mass concentration (BC) are carried out by using MICROTOPS II and Aethalometer and estimated the aerosol radiative forcing over this location. The mean values of AOD at 500nm are found to be 0.47±0.09, 0.34±0.08, 0.29±0.06 and 0.30±0.07 during summer, winter, monsoon and post-monsoon respectively. The Angstrom exponent (α380-1020) value is observed maximum in March (1.25±0.19) and which indicates the predominance of fine - mode aerosols and lowest in the month of July (0.33±0.14) and may be due to the dominance of coarse-mode aerosols. The diurnal variation of BC is exhibited two height peaks during morning 07:00-08:00 (IST) and evening 19:00-21:00 (IST) hours and one minima noticed during afternoon (13:00-16:00). The highest monthly mean BC concentration is observed in the month of January (3.4±1.2μgm(-3)) and the lowest in July (1.1±0.2μgm(-3)). The estimated Aerosol Direct Radiative Forcing (ADRF) in the atmosphere is found to be +36.8±1.7Wm(-2), +26.9±0.2Wm(-2), +18.0±0.6Wm(-2) and +18.5±3.1Wm(-2) during summer, winter, monsoon and post-monsoon seasons, respectively. Large difference between TOA and BOA forcing is observed during summer which indicate the large absorption of radiant energy (36.80Wm(-2)) which contributes more increase in atmospheric heating by ~1K/day. The BC contribution on an average is found to be 64% and is responsible for aerosol atmospheric heating.
authors.affiliation: Aerosol & Atmospheric Research Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, Andhra Pradesh, India.
authors.forename: Raja Obul Reddy
authors.initials: ROR
authors.lastname: Kalluri
authors.affiliation: Aerosol & Atmospheric Research Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, Andhra Pradesh, India.
authors.forename: Balakrishnaiah
authors.initials: B
authors.lastname: Gugamsetty
authors.affiliation: Aerosol & Atmospheric Research Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, Andhra Pradesh, India. Electronic address: krgverma@yahoo.com.
authors.forename: Rama Gopal
authors.initials: RG
authors.lastname: Kotalo
authors.affiliation: Aerosol & Atmospheric Research Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, Andhra Pradesh, India.
authors.forename: Siva Kumar Reddy
authors.initials: SKR
authors.lastname: Nagireddy
authors.affiliation: Aerosol & Atmospheric Research Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, Andhra Pradesh, India.
authors.forename: Chakradhar Rao
authors.initials: CR
authors.lastname: Tandule
authors.affiliation: Aerosol & Atmospheric Research Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, Andhra Pradesh, India.
authors.forename: Lokeswara Reddy
authors.initials: LR
authors.lastname: Thotli
authors.affiliation: Aerosol & Atmospheric Research Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, Andhra Pradesh, India; Srinivasa Ramanujan Institute of Technology, B.K. Samudram Mandal, Anantapur 515 701, Andhra Pradesh, India.
authors.forename: Reddy
authors.initials: R
authors.lastname: Rajuru Ramakrishna
authors.affiliation: Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695 022, Kerala, India.
authors.forename: Suresh Babu
authors.initials: SB
authors.lastname: Surendranair
keywords: Aerosol optical depth; Anantapur; Angstrom exponent value; BC concentration; Radiative forcing