scholarly journals Nonlinear Effects of Coexisting Surface and Atmospheric Forcing of Anthropogenic Absorbing Aerosols: Impact on the South Asian Monsoon Onset

2013 ◽  
Vol 26 (15) ◽  
pp. 5594-5607 ◽  
Author(s):  
Shao-Yi Lee ◽  
Ho-Jeong Shin ◽  
Chien Wang
Keyword(s):  
Indian Subcontinent ◽  
Critical Factor ◽  
Nonlinear Effects ◽  
Monsoon Onset ◽  
Climate Impacts ◽  
Monsoon Circulation ◽  
The South ◽  
Surface Cooling ◽  
Atmospheric Heating ◽  
Absorbing Aerosols

Abstract The direct radiative effect of absorbing aerosols consists of absorption-induced atmospheric heating together with scattering- and absorption-induced surface cooling. It is thus important to understand whether some of the reported climate impacts of anthropogenic absorbing aerosols are mainly due to the coexistence of these two opposite effects and to what extent the nonlinearity raised from such coexistence would become a critical factor. To answer these questions specifically regarding the South Asia summer monsoon with focus on aerosol-induced changes in monsoon onset, a set of century-long simulations using the Community Earth System Model, version 1.0.3 (CESM 1.0.3), of NCAR with fully coupled atmosphere and ocean components was conducted. Prescribed direct heating to the atmosphere and cooling to the surface were applied in the simulations over the Indian subcontinent, either alone or combined, during the aerosol-laden months of May and June. Over many places in the Indian subcontinent, the nonlinear effect dominates in the changes of subcloud layer moist static energy, precipitation, and monsoon onset. The surface cooling effect of aerosols appears to shift anomalous precipitative cooling away from the aerosol-forcing region and hence turn the negative feedback to aerosol-induced atmospheric heating into a positive feedback on the monsoon circulation through latent heat release over the Himalayan foothills. Moisture processes form the critical chain mediating local aerosol direct effects and onset changes in the monsoon system.

scholarly journals Particulate absorption of solar radiation: anthropogenic aerosols vs. dust

2009 ◽  
Vol 9 (2) ◽  
pp. 6571-6595 ◽  
Author(s):  
C. Wang ◽  
G.-R. Jeong ◽  
N. Mahowald
Keyword(s):  
Solar Radiation ◽  
North Africa ◽  
Radiative Forcing ◽  
Indian Subcontinent ◽  
Critical Factor ◽  
Climate Impacts ◽  
Anthropogenic Aerosols ◽  
Solar Absorption ◽  
Boreal Spring ◽  
Dust Absorption

Abstract. Particulate solar absorption is a critical factor in determining the value and even sign of the direct radiative forcing of aerosols. The heating to the atmosphere and cooling to the Earth's surface caused by this absorption are hypothesized to have significant climate impacts. We find that anthropogenic aerosols play an important role around the globe in total particulate absorption of solar radiation. The global-average anthropogenic fraction in total aerosol absorbing optical depth exceeds 65% in all seasons. Combining the potentially highest dust absorption with the lowest anthropogenic absorption within our model range, this fraction would still exceed 47% in most seasons except for boreal spring (36%) when dust abundance reaches its peak. Nevertheless, dust aerosol is still a critical absorbing constituent over places including North Africa, the entire tropical Atlantic, and during boreal spring in most part of Eurasian continent. The equality in absorbing solar radiation of dust and anthropogenic aerosols appears to be particularly important over Indian subcontinent and nearby regions as well as North Africa.

scholarly journals Particulate absorption of solar radiation: anthropogenic aerosols vs. dust

2009 ◽  
Vol 9 (12) ◽  
pp. 3935-3945 ◽  
Author(s):  
C. Wang ◽  
G. R. Jeong ◽  
N. Mahowald
Keyword(s):  
Solar Radiation ◽  
North Africa ◽  
Radiative Forcing ◽  
Indian Subcontinent ◽  
Critical Factor ◽  
Climate Impacts ◽  
Anthropogenic Aerosols ◽  
Solar Absorption ◽  
Boreal Spring ◽  
Dust Absorption

Abstract. Particulate solar absorption is a critical factor in determining the value and even sign of the direct radiative forcing of aerosols. The heating to the atmosphere and cooling to the Earth's surface caused by this absorption are hypothesized to have significant climate impacts. We find that anthropogenic aerosols play an important role around the globe in total particulate absorption of solar radiation. The global-average anthropogenic fraction in total aerosol absorbing optical depth exceeds 65% in all seasons. Combining the potentially highest dust absorption with the lowest anthropogenic absorption within our model range, this fraction would still exceed 47% in most seasons except for boreal spring (36%) when dust abundance reaches its peak. Nevertheless, dust aerosol is still a critical absorbing constituent over places including North Africa, the entire tropical Atlantic, and during boreal spring in most part of Eurasian continent. The equality in absorbing solar radiation of dust and anthropogenic aerosols appears to be particularly important over Indian subcontinent and nearby regions as well as North Africa.

Radiative effects of clouds and water vapor on the monsoon

2020 ◽  
Author(s):  
Michael Byrne ◽  
Laure Zanna
Keyword(s):  
Climate Change ◽  
Water Vapor ◽  
Monsoon Onset ◽  
Monsoon Circulation ◽  
Radiative Effects ◽  
Surface Cooling ◽  
Radiative Processes ◽  
Cloud Effect ◽  
The Tropics ◽  
Emergent Constraint

<p>Monsoons are summertime circulations shaping climates and societies across the tropics and subtropics. Here the radiative effects controlling the climatological monsoon and its response to climate change are investigated using idealized simulations. The influences of clouds, water vapor and CO<sub>2</sub> on the monsoon are decomposed using the radiation-locking technique. Seasonal cloud and water vapor radiative effects strongly modulate the climatological monsoon, reducing net monsoon precipitation by approximately half. Warming and moistening of the monsoon by seasonal longwave cloud and water vapor effects are counteracted by a strong shortwave cloud effect. The shortwave cloud effect expedites monsoon onset by approximately 10 days, whereas longwave cloud and water vapor effects delay onset. A simple theory for monsoon onset relates monsoon onset to the efficiency of surface cooling. In climate change simulations the water vapor feedback and CO<sub>2</sub> forcing have similar influences on the monsoon, warming the surface and moistening the region. In contrast, clouds have a negligible effect on surface temperature yet dominate the response of the monsoon circulation to climate change. The radiation-locking simulations and analyses advance understanding of how and why radiative processes influence the monsoon, and establish a new framework for interpreting monsoon--radiation coupling in observations, in state-of-the-art models and in different climate states. Moreover, sensitivities of the monsoon to the longwave cloud feedback are found to be similar over the seasonal cycle and under CO<sub>2</sub> forcing, suggesting a potential emergent constraint for monsoons in a changing climate.</p>

scholarly journals Synoptic Preconditions for Extreme Flooding during the Summer Asian Monsoon in the Mumbai Area

2014 ◽  
Vol 15 (1) ◽  
pp. 229-242 ◽  
Author(s):  
Marco Lomazzi ◽  
Dara Entekhabi ◽  
Joaquim G. Pinto ◽  
Giorgio Roth ◽  
Roberto Rudari
Keyword(s):  
Time Series ◽  
South Asian ◽  
Asian Monsoon ◽  
Indian Subcontinent ◽  
Monsoon Season ◽  
Value Added ◽  
South Asian Monsoon ◽  
Flood Events ◽  
The South ◽  
Synoptic Conditions

Abstract The summer monsoon season is an important hydrometeorological feature of the Indian subcontinent and it has significant socioeconomic impacts. This study is aimed at understanding the processes associated with the occurrence of catastrophic flood events. The study has two novel features that add to the existing body of knowledge about the South Asian monsoon: 1) it combines traditional hydrometeorological observations (rain gauge measurements) with unconventional data (media and state historical records of reported flooding) to produce value-added century-long time series of potential flood events and 2) it identifies the larger regional synoptic conditions leading to days with flood potential in the time series. The promise of mining unconventional data to extend hydrometeorological records is demonstrated in this study. The synoptic evolution of flooding events in the western-central coast of India and the densely populated Mumbai area are shown to correspond to active monsoon periods with embedded low pressure centers and have far-upstream influences from the western edge of the Indian Ocean basin. The coastal processes along the Arabian Peninsula where the currents interact with the continental shelf are found to be key features of extremes during the South Asian monsoon.

George Harrison and the Concert for Bangladesh

2017 ◽  
pp. 149-166
Author(s):  
Mohammad Delwar Hossain ◽  
James Aucoin
Keyword(s):  
Popular Music ◽  
South Asia ◽  
Indian Subcontinent ◽  
New Left ◽  
Humanitarian Aid ◽  
World Politics ◽  
Severe Weather ◽  
The South ◽  
George Harrison

The Concert for Bangladesh occurred on August 1, 1971, forever changing the dynamic between popular music, politics, and humanitarian aid. The concert was organized by former Beatle George Harrison, reflecting New Left political leanings. He was inspired to put on the concert by Bengali Ravi Shankar, who sought aid for victims of war and severe weather in East Pakistan, soon to become Bangladesh. The concert raised consciousness among the counterculture movement and mixed with world politics as the War of Liberation raged in the south Asia country on the Indian subcontinent.

Evaluation of the impact from the discharge of treated sewage on the south-east Saronicos Gulf through mathematical water quality modelling

1999 ◽  
Vol 39 (8) ◽  
pp. 63-70
Author(s):  
C. Noutsopoulos ◽  
E. Gavalaki ◽  
A. Andreadakis
Keyword(s):  
Biological Treatment ◽  
Critical Factor ◽  
Field Measurements ◽  
Substantial Improvement ◽  
Disposal Site ◽  
The South ◽  
Treated Sewage ◽  
Limiting Nutrient ◽  
The Impact

The paper presents the results of a study of the impact caused by the discharge of treated sewage from the south-west Attiki area to the south-east coast of the Saronicos Gulf. The study involved the application of a eutrophication-dissolved oxygen model which, following validation on the basis of field measurements, was applied to predict the impact of three different biological treatment configurations, with and without nutrients removal, as well as three alternative disposal sites on the quality of the receiving waters. The simulation results show that nitrogen is the limiting nutrient and that its removal during treatment results in a substantial improvement of the quality of the recipient. The disposal site is a critical factor in the case of a biological treatment scheme exhibiting carbon removal, but it is of limited importance in the case of treatment systems with nitrogen removal.

scholarly journals Regional Contrast of Mesoscale Convective System Structure prior to and during Monsoon Onset across South America

2011 ◽  
Vol 24 (14) ◽  
pp. 3753-3763 ◽  
Author(s):  
Thomas M. Rickenbach ◽  
Rosana Nieto-Ferreira ◽  
Richard P. Barnhill ◽  
Stephen W. Nesbitt
Keyword(s):  
South America ◽  
Annual Cycle ◽  
Dry Season ◽  
Monsoon Onset ◽  
System Structure ◽  
Convergence Zone ◽  
The South ◽  
The West ◽  
Central Amazon ◽  
Mesoscale Convective

Abstract In this study, a 10-yr (1998–2007) climatology of observations from the Tropical Rainfall Measuring Mission (TRMM) satellite is used to study regional mechanisms of monsoon onset across tropical and subtropical South America. The approach is to contrast regional differences in the structure, intensity, and rainfall of mesoscale convective systems (MCSs) prior to and after onset, in the context of thermodynamic conditions from the National Centers for Environmental Prediction (NCEP) reanalysis data. This is accomplished by analyzing the mean annual cycle time series, 10-yr frequency histograms, and 3-month-averaged values prior to and following onset in four regions of distinct rainfall variability. Observed MCS metrics and NCEP variables include lightning flash rate, convective rain fraction, height of the 30-dBZ isosurface, minimum 85-GHz polarization corrected temperature, and the fluxes of sensible and latent heat. The west-central Amazon region had a distinct maximum of MCS intensity 2 months prior to the monsoon onset date of each region, which was well correlated with surface sensible heat flux, despite the observation that thermodynamic instability was greatest after onset. At the mouth of the Amazon, the dry season rainfall minimum, the premonsoon maximum in MCS intensity metrics, and monsoon onset were all delayed by 2–3 months relative to the west-central Amazon. This delay in the annual cycle and comparatively large difference in pre- versus postonset MCSs, combined with previous work, suggest that the slow migration of the Atlantic Ocean intertropical convergence zone controls onset characteristics at the mouth of the Amazon. All metrics of convective intensity in the tropical regions decreased significantly following onset. These results, in the context of previous studies, are consistent with the hypothesis that thermodynamic, land surface, and aerosol controls on MCS intensity operate in concert with each other to control the evolution of precipitation system structure from the dry season to the wet season. The other two regions [the South Atlantic convergence zone (SACZ) and the south], associated with the well-documented dipole of intraseasonal rain variability, have a weaker and more variable annual cycle of all MCS metrics. This is likely related to the strong influence of baroclinic circulations and frontal systems in those regions. In the south, fewer but larger and more electrified MCSs prior to onset transition to more, smaller, and less electrified MCSs after onset, consistent with previous climatologies of strong springtime mesoscale convective complexes in that region.

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