Aerosol black carbon radiative forcing at an industrial city in northern India

Tripathi, Sachchida Nand

doi:10.1029/2005gl022515

Cited by 185 publications

(176 citation statements)

References 22 publications

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“…In the UNI case, HR is comparable to the results of Angevine et al (1998);Jochum et al (2004) and Tripathi (2005), who found 4 K day −1 , 6 K day −1 and 2 K day −1 respectively. The HR values obtained for both UNI and TOP experiments are prescribed in our LES.…”

Section: Design Of Numerical Experimentssupporting

confidence: 74%

“…Since then, several studies have followed: Angevine et al (1998) measured HR in the lower troposphere of around 4-5 K day −1 for the FLATLAND series of experiments. Tripathi (2005) found via a field campaign in Kampur, located in urbancontinental India, that aerosol SW absorption leads to HR ≈ 1.8 K day −1 . Malavelle et al (2011) found HR associated with SW absorption in West Africa as high as 1.2 K day −1 , with 0.4 K day −1 as a diurnal mean.…”

Section: Introductionmentioning

confidence: 99%

“…How shortwave (SW) radiation and aerosols interact in the atmosphere is one of the largest uncertainties in climate prediction (Satheesh and Ramanathan 2000;Tripathi 2005;Johnson et al 2008). Aerosols modify the vertical profile of radiative heating by absorbing and scattering radiation (Quijano et al 2000).…”

Section: Introductionmentioning

confidence: 99%

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Impacts of Aerosol Shortwave Radiation Absorption on the Dynamics of an Idealized Convective Atmospheric Boundary Layer

Barbaro

Arellano

Krol

et al. 2013

Boundary-Layer Meteorol

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We investigated the impact of aerosol heat absorption on convective atmospheric boundary-layer (CBL) dynamics. Numerical experiments using a large-eddy simulation model enabled us to study the changes in the structure of a dry and shearless CBL in depthequilibrium for different vertical profiles of aerosol heating rates. Our results indicated that aerosol heat absorption decreased the depth of the CBL due to a combination of factors: (i) surface shadowing, reducing the sensible heat flux at the surface and, (ii) the development of a deeper inversion layer, stabilizing the upper CBL depending on the vertical aerosol distribution. Steady-state analytical solutions for CBL depth and potential temperature jump, derived using zero-order mixed-layer theory, agreed well with the large-eddy simulations. An analysis of the entrainment zone heat budget showed that, although the entrainment flux was controlled by the reduction in surface flux, the entrainment zone became deeper and less stably stratified. Therefore, the vertical profile of the aerosol heating rate promoted changes in both the structure and evolution of the CBL. More specifically, when absorbing aerosols were present only at the top of the CBL, we found that stratification at lower levels was the mechanism responsible for a reduction in the vertical velocity and a steeper decay of the turbulent kinetic energy throughout the CBL. The increase in the depth of the inversion layer also modified the potential temperature variance. When aerosols were present we observed that the potential temperature variance became significant already around 0.7z i (where z i is the CBL height) but less intense at the entrainment zone due to the smoother potential temperature vertical gradient.

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Section: Design Of Numerical Experimentssupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Impacts of Aerosol Shortwave Radiation Absorption on the Dynamics of an Idealized Convective Atmospheric Boundary Layer

Barbaro

Arellano

Krol

et al. 2013

Boundary-Layer Meteorol

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“…Tripathi et al (2005) for an urban location Kanpur situated in the IGP region, but for the winter season in 2004. The mean atmospheric forcing over the Ocean region during both BFA and BNFA were negligibly small compared to the corresponding values over Land region.…”

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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“…Specifically, the role of light absorbing aerosols is poorly understood, as they transform electromagnetic radiation into thermal energy thereby changing the temperature profiles of their surroundings and reducing the incident solar flux/radiation below the absorbing aerosols (Schwartz and Buseck, 2000;Streets et al, 2006). The heating caused by the aerosols can cause a positive topof-atmosphere radiative forcing (Tripathi et al, 2005) if they decrease the planetary albedo (as seen from space) or if their single scattering albedo (SSA) is lower than the surface or the clouds below them. Recently, there is more evidence that carbonaceous aerosols are much more dominant and widespread in the atmosphere than previously thought (Novakov et al, 1997;Petzold et al, 2007;Reddy et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

et al. 2012

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Abstract. One of the major uncertainties in the understanding of Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. Aerosols exposed to high humidity will change their chemical, physical, and optical properties due to their increased water content. To model hydrated aerosols, atmospheric chemistry and climate models often use the volume weighted mixing rule to predict the complex refractive index (RI) of aerosols when they interact with high relative humidity, and, in general, assume homogeneous mixing. This study explores the validity of these assumptions. A humidified cavity ring down aerosol spectrometer (CRD-AS) and a tandem hygroscopic DMA (differential mobility analyzer) are used to measure the extinction coefficient and hygroscopic growth factors of humidified aerosols, respectively. The measurements are performed at 80 % and 90 %RH at wavelengths of 532 nm and 355 nm using size-selected aerosols with different degrees of absorption; from purely scattering to highly absorbing particles. The ratio of the humidified to the dry extinction coefficients (f RH ext (%RH, Dry)) is measured and compared to theoretical calculations based on Mie theory. Using the measured hygroscopic growth factors and assuming homogeneous mixing, the expected RIs using the volume weighted mixing rule are compared to the RIs derived from the extinction measurements.We found a weak linear dependence or no dependence of f RH(%RH, Dry) with size for hydrated absorbing aerosols in contrast to the non-monotonically decreasing behavior with size for purely scattering aerosols. No discernible difference could be made between the two wavelengths used. Less than 7 % differences were found between the real parts of the complex refractive indices derived and those calculated using the volume weighted mixing rule, and the imaginary parts had up to a 20 % difference. However, for substances with growth factor less than 1.15 the volume weighted mixing rule assumption needs to be taken with caution as the imaginary part of the complex RI can be underestimated.

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Aerosol black carbon radiative forcing at an industrial city in northern India

Cited by 185 publications

References 22 publications

Impacts of Aerosol Shortwave Radiation Absorption on the Dynamics of an Idealized Convective Atmospheric Boundary Layer

Impacts of Aerosol Shortwave Radiation Absorption on the Dynamics of an Idealized Convective Atmospheric Boundary Layer

Absorbing aerosols facilitate transition of Indian monsoon breaks to active spells

Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

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