Impact of absorbing aerosols on the simulation of climate over the Indian region in an atmospheric general circulation model

Chakraborty, Arindam; Satheesh, S. K.; Nanjundiah, Ravi S.; Srinivasan, J.

doi:10.5194/angeo-22-1421-2004

Cited by 28 publications

(20 citation statements)

References 24 publications

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“…Many models seem to have a tendency to get locked into either the oceanic or the continental TCZ (Gadgil and Sajani 1998). & Emissions of scattering and absorbing aerosols in the region are found to affect the monsoon climate (Chakraborty et al 2004). The uncertainty in the level of these emissions and the ability to model their impact on the monsoon are a problem (Sajani et al 2012;Turner and Annamalai 2012).…”

Section: Discussionmentioning

confidence: 99%

Performance evaluation of AR4 Climate Models in simulating daily precipitation over the Indian region using skill scores

Anandhi

Nanjundiah

2014

Theor Appl Climatol

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The ability of Coupled General Circulation Models (CGCMs) participating in the Intergovernmental Panel for Climate Change's fourth assessment report (IPCC AR4) for the 20th century climate (20C3M scenario) to simulate the daily precipitation over the Indian region is explored. The skill is evaluated on a 2.5°×2.5°grid square compared with the Indian Meteorological Department's (IMD) gridded dataset, and every GCM is ranked for each of these grids based on its skill score. Skill scores (SSs) are estimated from the probability density functions (PDFs) obtained from observed IMD datasets and GCM simulations. The methodology takes into account (high) extreme precipitation events simulated by GCMs. The results are analyzed and presented for three categories and six zones. The three categories are the monsoon season (JJASO -June to October), non-monsoon season (JFMAMND -January to May, November, December) and for the entire year ("Annual"). The six precipitation zones are peninsular, west central, northwest, northeast, central northeast India, and the hilly region. Sensitivity analysis was performed for three spatial scales, 2.5°grid square, zones, and all of India, in the three categories. The models were ranked based on the SS. The category JFMAMND had a higher SS than the JJASO category. The northwest zone had higher SSs, whereas the peninsular and hilly regions had lower SS. No single GCM can be identified as the best for all categories and zones. Some models consistently outperformed the model ensemble, and one model had particularly poor performance. Results show that most models underestimated the daily precipitation rates in the 0-1 mm/day range and overestimated it in the 1-15 mm/day range.

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Section: Discussionmentioning

confidence: 99%

Performance evaluation of AR4 Climate Models in simulating daily precipitation over the Indian region using skill scores

Anandhi

Nanjundiah

2014

Theor Appl Climatol

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“…Menon et al () found a reduction of precipitation over north Indian Ocean when an atmospheric GCM was forced with radiative effects of carbonaceous aerosols over south Asian region. Chakraborty et al () used an atmospheric GCM with aerosol forcing obtained from INDOEX (Indian Ocean Experiment) field campaign to show that the change in precipitation during monsoon season due to aerosols depend on the cumulus scheme used in the model. The impact of black carbon aerosols on tropical convection and climate has been studied by Wang (, ).…”

Section: Introductionmentioning

confidence: 99%

Local and remote impacts of direct aerosol forcing on Asian monsoon

Chakraborty

Nanjundiah

Srinivasan

2013

Intl Journal of Climatology

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ABSTRACT:The impact of heating by black carbon aerosols on Indian summer monsoon has remained inconclusive. Some investigators have predicted that black carbon aerosols reduce monsoon rainfall while others have argued that it will increase monsoon rainfall. These conclusions have been based on local influence of aerosols on the radiative fluxes. The impact of aerosol-like heating in one region on the rainfall in a remote region has not been examined in detail. Here, using an atmospheric general circulation model, it has been shown that remote influence of aerosol-like heating can be as important as local influence on Indian summer monsoon. Precipitation in northern Arabian Sea and north-west Indian region increased by 16% in June to July when aerosol-like heating were present globally. The corresponding increase in precipitation due to presence of aerosol-like heating only over South Asia (local impact) and East Asia (remote impact) were 28 and 13%, respectively. This enhancement in precipitation was due to destabilization of the atmosphere in premonsoon season that affected subsequent convection. Moreover, pre-monsoon heating of the lower troposphere changed the circulation substantially that enabled influx of more moisture over certain regions and reduced the moist static stability of the atmosphere. It has been shown that regional aerosol heating can have large impact on the phase of upper tropospheric Rossby wave in pre-monsoon season, which acts as a primary mechanism behind teleconnection and leads to the change in precipitation during monsoon season. These results demonstrate that changes in aerosol in one region can influence the precipitation in a remote region through changes in circulation.

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“…Thus, during a break, aerosol concentration builds up in central and north India through local emissions and long range transports while the north Indian Ocean remains relatively pristine. As a large fraction of these aerosols is of absorbing type (Menon 2004;Chakraborty et al 2004;Bollasina et al 2008), they would cool the surface but warm the atmospheric layer between 1 and 3 km. Such warming of the lower atmosphere over central and north India and lack of it over the north Indian Ocean would lead to a north-south temperature gradient at this level and convergence of moisture to central and north India.…”

Section: Introductionmentioning

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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Impact of absorbing aerosols on the simulation of climate over the Indian region in an atmospheric general circulation model

Cited by 28 publications

References 24 publications

Performance evaluation of AR4 Climate Models in simulating daily precipitation over the Indian region using skill scores

Performance evaluation of AR4 Climate Models in simulating daily precipitation over the Indian region using skill scores

Local and remote impacts of direct aerosol forcing on Asian monsoon

Absorbing aerosols facilitate transition of Indian monsoon breaks to active spells

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