scholarly journals Anthropogenic Aerosols Cause Recent Pronounced Weakening of Asian Summer Monsoon Relative to Last Four Centuries

2019 ◽  
Vol 46 (10) ◽  
pp. 5469-5479 ◽  
Author(s):  
Yu Liu ◽  
Wenju Cai ◽  
Changfeng Sun ◽  
Huiming Song ◽  
Kim M. Cobb ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Anthropogenic Aerosols ◽  
Asian Summer

scholarly journals Distinct effects of anthropogenic aerosols on the East Asian summer monsoon between multidecadal strong and weak monsoon stages

2016 ◽  
Vol 121 (12) ◽  
pp. 7026-7040 ◽  
Author(s):  
Xiaoning Xie ◽  
Hongli Wang ◽  
Xiaodong Liu ◽  
Jiandong Li ◽  
Zhaosheng Wang ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Anthropogenic Aerosols ◽  
Asian Summer

scholarly journals Transport of aerosol pollution in the UTLS during Asian summer monsoon as simulated by ECHAM5-HAMMOZ model

2012 ◽  
Vol 12 (11) ◽  
pp. 30081-30117 ◽  
Author(s):  
S. Fadnavis ◽  
K. Semeniuk ◽  
L. Pozzoli ◽  
M. G. Schultz ◽  
S. D. Ghude ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Indian Subcontinent ◽  
Aerosol Layer ◽  
Anthropogenic Aerosols ◽  
Upper Troposphere ◽  
Aerosol Pollution ◽  
Asian Summer ◽  
Cloud Ice ◽  
The Impact

Abstract. An eight member ensemble of ECHAM5-HAMMOZ simulations for the year 2003 is analyzed to study the transport of aerosols in the Upper Troposphere and Lower Stratosphere (UTLS) during the Asian Summer Monsoon (ASM). Simulations show persistent maxima in black carbon, organic carbon, sulfate, and mineral dust aerosols within the anticyclone in the UTLS throughout the ASM (period from July to September) when convective activity over the Indian subcontinent is highest. Model simulations indicate boundary layer aerosol pollution as the source of this UTLS aerosol layer and identify ASM convection as the dominant transport process. Evidence of ASM transport of aerosols into the stratosphere is observed in HALogen Occultation Experiment (HALOE) and Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction. The impact of aerosols in the UTLS region is analyzed by evaluating the differences between simulations with (CTRL) and without aerosol (HAM-off) loading. The transport of anthropogenic aerosols in the UTLS increases cloud ice, water vapour and temperature, indicating that aerosols play an important role in enhancement of cloud ice in the Upper-Troposphere (UT). Aerosol induced circulation changes include a weakening of the main branch of the Hadley circulation and increased vertical transport around the southern flank of the Himalayas and reduction in monsoon precipitation over the India region.

scholarly journals Dynamics of Asian Summer Monsoon Response to Anthropogenic Aerosol Forcing

2019 ◽  
Vol 32 (3) ◽  
pp. 843-858 ◽  
Author(s):  
Hai Wang ◽  
Shang-Ping Xie ◽  
Yu Kosaka ◽  
Qinyu Liu ◽  
Yan Du
Keyword(s):  
Summer Monsoon ◽  
Radiative Forcing ◽  
Asian Summer Monsoon ◽  
Atmospheric Response ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Sst Cooling ◽  
Aerosol Forcing ◽  
Cooling Pattern ◽  
Asian Summer

Anthropogenic aerosols partially mask the greenhouse warming and cause the reduction in Asian summer monsoon precipitation and circulation. By decomposing the atmospheric change into the direct atmospheric response to radiative forcing and sea surface temperature (SST)-mediated change, the physical mechanisms for anthropogenic-aerosol-induced changes in the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM) are diagnosed. Using coupled and atmospheric general circulation models, this study shows that the aerosol-induced troposphere cooling over Asian land regions generates anomalous sinking motion between 20° and 40°N and weakens the EASM north of 20°N without SST change. The decreased EASM precipitation and the attendant wind changes are largely due to this direct atmospheric response to radiative forcing, although the aerosol-induced North Pacific SST cooling also contributes. The SST-mediated change dominates the aerosol-induced SASM response, with contributions from both the north–south interhemispheric SST gradient and the local SST cooling pattern over the tropical Indian Ocean. Specifically, with large meridional gradient, the zonal-mean SST cooling pattern is most important for the Asian summer monsoon response to anthropogenic aerosol forcing, resulting in a reorganization of the regional meridional atmospheric overturning circulation. While uncertainty in aerosol radiative forcing has been emphasized in the literature, our results show that the intermodel spread is as large in the SST effect on summer monsoon rainfall, calling for more research into the ocean–atmosphere coupling.

The Influences of Climate Forcers and Agricultural Activities on the South Asian Summer Monsoon

2020 ◽  
Author(s):  
Shradda Dhungel ◽  
Kostas Tsigaridis ◽  
Susanne Bauer
Keyword(s):  
South Asia ◽  
South Asian ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Surface Energy Budget ◽  
Agricultural Activities ◽  
South Asian Summer Monsoon ◽  
Anthropogenic Aerosols ◽  
Aerosol Loading ◽  
Asian Summer

<p>South Asia is one of the most heavily populated regions in the world with about 1.7 billion inhabitants. The diversity of human activities in the region make delineating the sources and magnitude of regional emissions complex. The major combustion sources in South Asia – predominantly anthropogenic – include wildfires and the burning of agricultural residues, garbage, biofuels, and fossil fuels. But regional aerosol loading is also heavily influenced by natural aerosols, primarily dust transported from as far as the Arabian Peninsula. Past studies have examined how irrigation expansion along with greenhouse gas (GHG) forcing have altered the surface energy budget, thereby affecting the transport of water vapor and altering South Asian Summer Monsoon (SASM) rainfall variability. However, there are still limited modelling studies that consider anthropogenic effects from anthropogenic aerosol loading in combination with irrigation and GHGs and how these factors collectively induce variability in the SASM. Using the NASA GISS-E2.1 model, this study elucidates the role of intensive agricultural activities on SASM, both at the onset of the Green Revolution (i.e., 1960s) and at present, isolating the individual roles of irrigation, anthropogenic aerosols, and GHGs. Specifically, we examine the impacts on SASM by using sensitivity runs to quantify how anthropogenic emissions from agriculture, urbanization as well as long- and short-term forcers have affected SASM from 1960-2014 using prescribed- and coupled-ocean runs. Understanding the roles of each of these influences on SASM can help to develop more effective climate interventions in the region and predict how SASM will influence and interact with the changing regional and global climate.</p>

scholarly journals Nonlinear response of Asian summer monsoon precipitation to emission reductions in South and East Asia

2021 ◽  
Author(s):  
Ross Herbert ◽  
Laura J Wilcox ◽  
Manoj Joshi ◽  
Ellie Highwood ◽  
David J Frame
Keyword(s):  
East Asia ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Anthropogenic Aerosols ◽  
Emissions Reductions ◽  
Emission Reductions ◽  
Aerosol Emission ◽  
Highly Nonlinear ◽  
Asian Summer ◽  
Aerosol Emissions

Abstract Anthropogenic aerosols over South and East Asia currently have a stronger impact on the Asian Summer Monsoon (ASM) than greenhouse gas emissions, yet projected aerosol emission changes in these regions are subject to considerable uncertainties such as timescale, location, emission type, and even the sign of the change. We use a circulation/climate model with idealised aerosol distributions to demonstrate that the sum of ASM responses to aerosol emission reductions in each region is very different to the response to simultaneous reductions in both regions, implying the ASM response to aerosol emissions reductions is highly nonlinear. The phenomenon is independent of whether aerosols are scattering or absorbing, and results from interaction of induced atmospheric circulation changes. The nonlinearity from interactions between aerosol forcing from different regions represents a new source of uncertainty in projections of ASM changes over the next 30-40 years, and may limit the utility of country-dependent aerosol trajectories when considering their Asia-wide effects, though we recommend further work to establish whether the nonlinearity is buffered by other drivers. To understand likely changes in the ASM due to aerosol reductions, countries will need to accurately take account of emissions reductions from across the wider region, rather than approximating them using simple scenarios and emulators. The nonlinearity in the response to forcing therefore presents a regional public goods issue for countries affected by the ASM, as the costs and benefits of aerosol emissions reductions are not internalised; in fact, forcings from different countries such as India and China work jointly to determine outcomes across the region.

scholarly journals East Asian summer monsoon enhanced by COVID-19

2021 ◽  
Author(s):  
Chao He ◽  
Wen Zhou ◽  
Tim Li ◽  
Tianjun Zhou ◽  
Yuhao Wang
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Fast Response ◽  
Forced Response ◽  
Anthropogenic Aerosols ◽  
Coupled Models ◽  
Asian Continent ◽  
Asian Summer

Abstract Anthropogenic emissions decreased dramatically during the COVID-19 pandemic, but its possible effect on monsoon is unclear. Based on coupled models participating in the COVID Model Intercomparison Project (COVID-MIP), we show modeling evidence that the East Asian summer monsoon (EASM) is enhanced in terms of both precipitation and circulation, and the amplitude of the forced response reaches about 1/3 of the standard deviation for interannual variability. The response of EASM to COVID-19 is consistent with the response to the removal of all anthropogenic aerosols simulated by atmospheric component models, which confirms the dominant role of the fast response to reduced aerosols. The observational evidence, i.e., the anomalously strong EASM observed in 2020 and 2021, also supports the simulated enhancement of EASM. The essential mechanism for the enhanced EASM in response to COVID-19 is the enhanced zonal thermal contrast between Asian continent and the western North Pacific in the troposphere, particularly at the upper troposphere, due to the reduced aerosol concentration over Asian continent and the associated latent heating feedback. As the enhancement of EASM is a fast response to the reduction in aerosols, the effect of COVID-19 on EASM dampens soon after the rebound of emissions based on the models participating in COVID-MIP.

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