scholarly journals Fast and slow responses of the South Asian monsoon system to anthropogenic aerosols

2012 ◽  
Vol 39 (18) ◽  
Author(s):  
Dilip Ganguly ◽  
Philip J. Rasch ◽  
Hailong Wang ◽  
Jin-ho Yoon
Keyword(s):  
South Asian ◽  
Asian Monsoon ◽  
South Asian Monsoon ◽  
The South ◽  
Anthropogenic Aerosols ◽  
Monsoon System

Climate response of the South Asian monsoon system to anthropogenic aerosols

2012 ◽  
Vol 117 (D13) ◽  
pp. n/a-n/a ◽  
Author(s):  
Dilip Ganguly ◽  
Philip J. Rasch ◽  
Hailong Wang ◽  
Jin-Ho Yoon
Keyword(s):  
South Asian ◽  
Asian Monsoon ◽  
South Asian Monsoon ◽  
Climate Response ◽  
The South ◽  
Anthropogenic Aerosols ◽  
Monsoon System

Climate response of the south Asian monsoon system to West Asia, Tibetan Plateau and local dust emissions

2019 ◽  
Vol 53 (9-10) ◽  
pp. 6245-6264 ◽  
Author(s):  
Charu Singh ◽  
Dilip Ganguly ◽  
Puneet Sharma ◽  
Shiwansha Mishra
Keyword(s):  
Tibetan Plateau ◽  
South Asian ◽  
Asian Monsoon ◽  
South Asian Monsoon ◽  
Climate Response ◽  
The South ◽  
Dust Emissions ◽  
Monsoon System ◽  
Local Dust

Combined effects of anthropogenic aerosols and global warming on the South Asian Monsoon

2020 ◽  
Author(s):  
Ayantika Dey Choudhury ◽  
Krishnan Raghavan ◽  
Manmeet Singh ◽  
Swapna Panickal ◽  
Sandeep Narayansetti ◽  
...  
Keyword(s):  
Global Warming ◽  
South Asian ◽  
Large Scale ◽  
Asian Monsoon ◽  
Monsoon Circulation ◽  
South Asian Monsoon ◽  
Combined Effects ◽  
The South ◽  
Anthropogenic Aerosols ◽  
Aerosol Forcing

<p>The South Asian monsoon (SAM) precipitation has been generally regarded to exhibit contrasting responses to greenhouse gas (GHG) and anthropogenic aerosol forcing, although it is not adequately clear as to how it might respond to the combined influence of GHG and aerosol forcing.  The present study examines the individual and combined effects of global warming and anthropogenic aerosols on the SAM based on a suite of numerical experiments conducted using the IITM Earth System Model version2 (IITM-ESMv2). Four sets of 50-year model integrations are performed using IITM-ESMv2 with different anthropogenic forcings 1) Pre-Industrial control, 2) anthropogenic aerosols of 2005 3) CO2 concentrations of 2005 4) anthropogenic aerosols and CO2 of 2005. In the experiment with the elevated CO2 level of 2005, an intensification of SAM precipitation and strengthening of large-scale monsoon cross-equatorial flow is noted relative to the PI-CTL run. In contrast, the experiment with elevated anthropogenic aerosols of 2005 shows a decrease of SAM precipitation and weakening of monsoon circulation relative to the PI-CTL run. A striking result emerging from this study is the strong suppression of SAM precipitation, pronounced weakening of the monsoon circulation and suppression of organized convection in response to the combined radiative effects of elevated CO2 and anthropogenic aerosols relative to the PI-CTL run. By diagnosing the model simulations it is noted that the radiative effects in the combined forcing experiment lead to a pronounced summer-time cooling of the NH as compared to the equatorial and southern oceans which are predominantly influenced by global warming, thereby creating a north-south differential radiative forcing over the Indian longitudes.  Additionally, the influence of absorbing aerosols over South and East Asia creates a surface radiation deficit over the region, stabilizes the lower troposphere, slows down the monsoon winds and reduces surface evaporation.  Although the anticyclones over the subtropical Indian Ocean intensify in the combined forcing experiment, the model simulation shows that much of the precipitation enhancement occurs to the south of the equator over the Indian Ocean whereas the moisture transport and convergence to the north of the equator is substantially reduced. Furthermore, the combined forcing experiment shows that anomalous large-scale descent over the subcontinent reinforces the suppression of organized convection giving rise to more intense breaks and weaker active spells in the southwest monsoon on sub-seasonal time-scales. This study hints that future decreases in NH aerosol emissions could potentially reverse the ongoing decreasing trend of the observed SAM precipitation since 1950s in a purely global warming environment.</p>

scholarly journals Contribution of local and remote anthropogenic aerosols to the twentieth century weakening of the South Asian Monsoon

2014 ◽  
Vol 41 (2) ◽  
pp. 680-687 ◽  
Author(s):  
Massimo A. Bollasina ◽  
Yi Ming ◽  
V. Ramaswamy ◽  
M. Daniel Schwarzkopf ◽  
Vaishali Naik
Keyword(s):  
Twentieth Century ◽  
South Asian ◽  
Asian Monsoon ◽  
South Asian Monsoon ◽  
The South ◽  
Anthropogenic Aerosols

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.

scholarly journals The remote response of the South Asian Monsoon to reduced dust emissions and Sahara greening during the middle Holocene

2021 ◽  
Vol 17 (3) ◽  
pp. 1243-1271
Author(s):  
Francesco S. R. Pausata ◽  
Gabriele Messori ◽  
Jayoung Yun ◽  
Chetankumar A. Jalihal ◽  
Massimo A. Bollasina ◽  
...  
Keyword(s):  
South Asian ◽  
Asian Monsoon ◽  
Monsoon Season ◽  
Dust Emission ◽  
Northern Africa ◽  
South Asian Monsoon ◽  
The South ◽  
Airborne Dust ◽  
Orbital Parameters ◽  
Humid Period

Abstract. Previous studies based on multiple paleoclimate archives suggested a prominent intensification of the South Asian Monsoon (SAM) during the mid-Holocene (MH, ∼6000 years before present). The main forcing that contributed to this intensification is related to changes in the Earth's orbital parameters. Nonetheless, other key factors likely played important roles, including remote changes in vegetation cover and airborne dust emission. In particular, northern Africa also experienced much wetter conditions and a more mesic landscape than today during the MH (the so-called African Humid Period), leading to a large decrease in airborne dust globally. However, most modeling studies investigating the SAM changes during the Holocene overlooked the potential impacts of the vegetation and dust emission changes that took place over northern Africa. Here, we use a set of simulations for the MH climate, in which vegetation over the Sahara and reduced dust concentrations are considered. Our results show that SAM rainfall is strongly affected by Saharan vegetation and dust concentrations, with a large increase in particular over northwestern India and a lengthening of the monsoon season. We propose that this remote influence is mediated by anomalies in Indian Ocean sea surface temperatures and may have shaped the evolution of the SAM during the termination of the African Humid Period.

Characteristics of Precipitating Convective Systems in the South Asian Monsoon

2011 ◽  
Vol 12 (1) ◽  
pp. 3-26 ◽  
Author(s):  
Ulrike Romatschke ◽  
Robert A. Houze
Keyword(s):  
South Asian ◽  
Diurnal Cycle ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Asian Monsoon ◽  
South Asian Monsoon ◽  
Western Himalayas ◽  
The South ◽  
Convective Systems ◽  
Large Systems

Abstract Eight years of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data show how convective systems of different types contribute to precipitation of the South Asian monsoon. The main factor determining the amount of precipitation coming from a specific system is its horizontal size. Convective intensity and/or number of embedded convective cells further enhance its precipitation production. The precipitation of the monsoon is concentrated in three mountainous regions: the Himalayas and coastal ranges of western India and Myanmar. Along the western Himalayas, precipitation falls mainly from small, but highly convective systems. Farther east along the foothills, systems are more stratiform. These small and medium systems form during the day, as the monsoon flow is forced upslope. Nighttime cooling leads to downslope flow and triggers medium-sized systems at lower elevations. At the mountainous western coasts of India and Myanmar, small and medium systems are present throughout the day, as an orographic response to the southwesterly flow, with a slight superimposed diurnal cycle. Medium systems are favored over the eastern parts of the Arabian Sea and large systems are favored over the Bay of Bengal when an enhanced midlevel cyclonic circulation occurs over the northern parts of these regions. The systems forming upstream of coastal mountains over the Bay of Bengal are larger than those over the Arabian Sea, probably because of the moister conditions over the bay. The large systems over the bay exhibit a pronounced diurnal cycle, with systems forming near midnight and maximizing in midday.

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