Aerosol radiative forcing over a tropical urban site in India

Pandithurai, G.; Pinker, R. T.; Takamura, Toshinari; Devara, P. C. S.

doi:10.1029/2004gl019702

Cited by 77 publications

(40 citation statements)

References 17 publications

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“…Minor differences can be seen in estimated forcing values between the present study and the previous one by Pandithurai et al (2004). In order to ascertain the differences, we performed an exercise for the same months (November to April) by putting the uniform albedo value (0.15), as the case with previous study, in the model instead of wavelength dependence of albedo and found that the present values fall short by 9% and 85% at surface and TOA levels, respectively.…”

Section: Comparison and Implications To Regional Climatementioning

confidence: 99%

“…By definition, the aerosol direct short-wave (solar) radiative forcing (ADRF) is the change (DF) in the radiation flux (F) either at the surface (S) or at the TOA, respectively without and with the aerosol particles in the atmosphere (Russell et al, 1999;Podgorny et al, 2000;Yu et al, 2001;Pandithurai et al, 2004). This is generally represented as:…”

Section: Aerosol Radiative Forcingmentioning

confidence: 99%

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A long-term study of aerosol modulation of atmospheric and surface solar heating over Pune, India

Kumar¹,

Devara

2012

Tellus B: Chemical and Physical Meteorology

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A B S T R A C T Implications of aerosol characteristics, observed during a five-year (2004Á2009) period over Pune (a tropical urban location), to short-wave radiation budget are reported. A discrete ordinate radiative transfer (DISORT) model with a code, namely, Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART), has been used to carry out the radiative transfer computations. The validity of the method is demonstrated using independent ground-based remote sensing observations. Uncertainties in the estimates are also quantified. Clear-sky forcing reveals the points that include (1) Large negative bottom-of-the-atmosphere (BOA) forcing (more than (30 Wm (2 ) in all the months with peaks during October, December and March when the surface forcing exceeds Â (40 Wm (2 , and (2) Surface forcing values are higher for pre-monsoon months, while they are comparable for winter and post-monsoon months. The top-of-the-atmosphere (TOA) forcing is found to be negative during all the seasons. Large differences between TOA and BOA forcing during pre-monsoon, winter and post-monsoon indicate large absorption of radiant energy ( Â30 Wm (2 ) within the atmosphere during these seasons, thus increasing atmospheric heating by Â1 K/d. These values imply that aerosols have considerable impact on the atmosphereÁsurface system by causing substantial warming/cooling at the atmosphere/surface. This persistent trend in strong atmospheric absorption is likely to alter atmospheric thermodynamic conditions and thus affects circulation considerably.

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Section: Comparison and Implications To Regional Climatementioning

confidence: 99%

Section: Aerosol Radiative Forcingmentioning

confidence: 99%

A long-term study of aerosol modulation of atmospheric and surface solar heating over Pune, India

Kumar¹,

Devara

2012

Tellus B: Chemical and Physical Meteorology

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“…Such effects are produced by the optical, chemical and microphysical properties of the aerosols, nature of the underlying surface, cloudiness etc. (Babu et al 2002;Pandithurai et al 2004). The ARF is given by the expression:…”

Section: Role Of Aerosols On the Dynamical Responsementioning

confidence: 99%

Absorbing aerosols facilitate transition of Indian monsoon breaks to active spells

et al. 2010

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While some long breaks of monsoon intraseasonal oscillations (MISOs) are followed by active spells (BFA), some others are not (BNFA). The circulation during BFA (BNFA) cases helps (prevents) accumulation of absorbing aerosols over central India (CI) resulting in almost three times larger Aerosol Index (AI) over CI, during BFA cases compared to BNFA cases. A seminal role played by the absorbing aerosols in the transition from break to active spells is unraveled through modification of the north-south temperature gradient at lower levels. The meridional gradient of temperature at low level (DT) between aerosol-rich CI and pristine equatorial Indian Ocean is large ([6°C) and sustains for long time ([10 days) during BFA leading to significant moisture convergence to CI. The stability effect arising from surface cooling by the aerosols is overcome by the enhanced moisture convergence creating a moist static unstable atmosphere conducive for the large-scale organized convection over the CI region leading to the resurgence of active spells. The moisture convergence induced by DT was also able to overcome possible aerosol indirect effect (Twomey effect) and initiate deep convection and transition to active condition. During BNFA cases, however the maximum DT, which was weaker than the BFA cases by more than 1.5°C, could not sustain required moisture convergence and failed to lead to a sustained active spell. Using data from MODIS (MODerate resolution Imaging Spectroradiometer) onboard Terra and several other input parameters from various satellites for the period 2000-2009, the aerosol induced radiative forcing representative of two regions-the CI to the north and the pristine ocean to the south-were estimated and support the differences in observed DT during the two cases. Our results highlight the need for proper inclusion of absorbing aerosols in dynamical models for simulation of the observed variability of MISOs and their extended range prediction.

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“…Similarly, in the north Indian region also there are some studies on aerosol characterization and forcing but they are limited to pre-monsoon season only (Singh et al, 2005;Pandithurai et al, 2008;Beegum et al, 2008). Present study, for the first time, is focused on the monthly variation of clear sky direct aerosol radiation forcing (DARF) over a north Indian station, Delhi, for the whole year during January 2006 to January 2007.…”

Section: Introductionmentioning

confidence: 99%

Clear-sky direct aerosol radiative forcing variations over mega-city Delhi

et al. 2010

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Abstract. The direct aerosol radiative forcing (DARF) has been estimated for the clear-sky conditions over Delhi from January 2006 to January 2007 using Santa Barbara DISORT Atmospheric Radiative Transfer model (SBDART) in the wavelength range 300-3000 nanometer. The single scattering albedo (SSA) and the asymmetry parameter used in this model were estimated using the Optical Properties of Aerosol and Cloud (OPAC) model. The annual average AOD observed at 500 nm was ∼0.86±0.42 with an average Angstrom exponent ∼0.68±0.35. The average monthly AOD throughout the year over Delhi was found to be in the range 0.56 to 1.22 with the Angstrom exponent in the range 0.38 to 0.96. A high monthly average BC concentration in the range 4-15 µg m −3 led to monthly average SSA in the range 0.90±0.4 to 0.74±0.3 during the year. Consequently, the monthly average clear-sky DARF at the surface was found to vary in the range −46±8 W m −2 to −110±20 W m −2 , at TOA in the range −1.4±0.4 to 21±2 W m −2 , whereas in the atmosphere it was in the range 46±9 W m −2 to 115±19 W m −2 throughout the year. As the dust concentration in the atmosphere was highest (May-June) the SSA showed an increase with wavelength however when dust concentration was low the SSA decreased with the wavelength.

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Aerosol radiative forcing over a tropical urban site in India

Cited by 77 publications

References 17 publications

A long-term study of aerosol modulation of atmospheric and surface solar heating over Pune, India

A long-term study of aerosol modulation of atmospheric and surface solar heating over Pune, India

Absorbing aerosols facilitate transition of Indian monsoon breaks to active spells

Clear-sky direct aerosol radiative forcing variations over mega-city Delhi

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