scholarly journals Searching for a fingerprint of global warming in the Asian summer monsoon

MAUSAM ◽  
2021 ◽  
Vol 52 (1) ◽  
pp. 213-220
Author(s):  
DAVID B. STEPHENSON ◽  
HERVE DOUVILLE ◽  
K. RUPA KUMAR
Keyword(s):  
Global Warming ◽  
Summer Monsoon ◽  
General Circulation ◽  
Large Scale ◽  
Climate Models ◽  
Asian Summer Monsoon ◽  
Quantitative Agreement ◽  
Monsoon Circulation ◽  
Clear Trend ◽  
Asian Summer

This study investigates possible trends in several large scale indices that describe the Asian summer monsoon. Results from recent atmospheric general circulation experiments are used to provide clues as to how the monsoon might be changing due to the effects of global warming. Interestingly, this study has found that the large-scale wind shear monsoon indices have been decreasing at a rate of 0.1-0.3% per year (based on NCEP/CAR reanalysis 1958-98) in quantitative agreement with recent results from doubled CO2 simulations made using several state-of-the-art climate models. Nevertheless, despite the weakening of the monsoon circulation, all-India rainfall shows no clear trend in either the model results or in the observation reanalysis from 1958-98. Multiple regression is used to separate out the "dynamical" contribution from the observed all-India rainfall index, and a clear increasing trend then emerges in the "non-dynamical" residual. A simple dimensionless Multivariate Monsoon Index (MMI) is proposed that could be of use in monitoring global warming changes in the monsoon.

scholarly journals Characteristics of a persistent "pool of inhibited cloudiness" and its genesis over the Bay of Bengal associated with the Asian summer monsoon

2011 ◽  
Vol 29 (7) ◽  
pp. 1247-1252 ◽  
Author(s):  
Anish Kumar M. Nair ◽  
K. Rajeev ◽  
S. Sijikumar ◽  
S. Meenu
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Surface Wind ◽  
Spatial Gradient ◽  
Dynamical Response ◽  
Monsoon Circulation ◽  
Asian Summer

Abstract. Using spatial and vertical distributions of clouds derived from multi-year spaceborne observations, this paper presents the characteristics of a significant "pool of inhibited cloudiness" covering an area of >106 km2 between 3–13° N and 77–90° E over the Bay of Bengal (BoB), persisting throughout the Asian summer monsoon season (ASM). Seasonal mean precipitation rate over the "pool" is <3 mm day−1 while that over the surrounding regions is mostly in the range of 6–14 mm day−1. Frequency of occurrence of clouds in this "pool" is ~20–40 % less than that over the surrounding deep convective regions. Zonal and meridional cross sections of the altitude distribution of clouds derived from CloudSat data reveal a vault-like structure at the "pool" with little cloudiness below ~7 km, indicating that this "pool" is almost fully contributed by the substantially reduced or near-absence of low- and middle-level clouds. This suggest the absence of convection in the "pool" region. Spaceborne scatterometer observations show divergence of surface wind at the "pool" and convergence at its surroundings, suggesting the existence of a mini-circulation embedded in the large-scale monsoon circulation. Reanalysis data shows a mini-circulation extending between the surface and ~3 km altitude, but its spatial structure does not match well with that inferred from the above observations. Sea surface at the south BoB during ASM is sufficiently warm to trigger convection, but is inhibited by the subsidence associated with the mini-circulation, resulting in the "pool". This mini-circulation might be a dynamical response of the atmosphere to the substantial spatial gradient of latent heating by large-scale cloudiness and precipitation at the vast and geographically fixed convective zones surrounding the "pool". Subsidence at the "pool" might contribute to the maintenance of convection at the above zones and be an important component of ASM that is overlooked hitherto.

Large-scale urbanization effects on eastern Asian summer monsoon circulation and climate

2015 ◽  
Vol 47 (1-2) ◽  
pp. 117-136 ◽  
Author(s):  
Haishan Chen ◽  
Ye Zhang ◽  
Miao Yu ◽  
Wenjian Hua ◽  
Shanlei Sun ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Monsoon Circulation ◽  
Asian Summer ◽  
Asian Summer Monsoon Circulation

Potential Changes in Extreme Events Under Global Climate Change

2008 ◽  
Vol 3 (1) ◽  
pp. 39-50 ◽  
Author(s):  
Koji Dairaku ◽  
◽  
Seita Emori ◽  
Hironori Higashi ◽  
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Summer Monsoon ◽  
Extreme Events ◽  
Extreme Precipitation ◽  
General Circulation ◽  
Asian Summer Monsoon ◽  
Climate Conditions ◽  
Asian Summer ◽  
A1b Scenario

Climate-related disasters are a serious problem in Asia. Advances in the understanding of meteorology and in the development of monitoring and forecasting systems have enhanced early warning systems, contributing immensely to reducing fatalities resulting from typhoons, cyclones, and floods. The frequency of extreme events causing water-related disasters has increased, however, over the last decade and may grow in the future due to anthropogenic activity. The sections that follow introduce two recent efforts in hydrologic projection in Asia. Time-slice ensemble experiments using a high-resolution (T106) atmospheric general circulation model (AGCM) on the earth simulator revealed changes in the South Asian summer monsoon resulting from climate change. Model results under global warming conditions suggest increases in mean and extreme precipitation during the Asian summer monsoon. increases generally attributed to greater atmospheric moisture content. a thermodynamic change. Dynamic changes limit the intensification of mean precipitation. Enhanced extreme precipitation over land in South Asia arises from dynamic rather than thermodynamic changes. The impact of global warming on heavy precipitation features and flood risks in the Tama River basin in Japan is addressed using 12 atmosphere-ocean coupled general circulation models (AOGCMs). Multi-model ensemble average 200-year quantiles in Tokyo from 2050 to 2300 under Intergovernmental Panel on Climate Changes (IPCC) Special Reports on Emissions Scenarios (SRES) A1B scenario climate conditions were 1.07-1.20 times greater than that under present climate conditions. A 200-year quantile extreme event in the present occurs in much shorter return periods in the A1B scenario. High-water discharge in the basin rose by 10%-26% and flood volume increased by 46%-131% for precipitation in a 200-year return period. The risk of flooding in the basin is thus, even though the increase of extreme precipitation is not substantial, projected to be much higher than that presently estimated.

Global Warming Projection by an Atmospheric Global Model with 20-km Grid

2008 ◽  
Vol 3 (1) ◽  
pp. 4-14 ◽  
Author(s):  
Shoji Kusunoki ◽  
◽  
Jun Yoshimura ◽  
Hiromasa Yoshimura ◽  
Ryo Mizuta ◽  
...  
Keyword(s):  
Global Warming ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
General Circulation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Circulation Model ◽  
Global Climate Models ◽  
Rain Band ◽  
Asian Summer

We projected global warming on the Earth Simulator using a very high horizontal resolution atmospheric global general circulation model with 20-km grids, targeting tropical cyclones (TCs) and the rain band (Baiu) during the East Asian summer monsoon season because these bring typical extreme events and global climate models have not yielded reliable simulations or projections due to insufficient resolutions. Our model reproduces TCs and a Baiu rain band reasonably well under present-day climate conditions. In a warmer climate at the end of this century, the model projects, under A1B scenario of the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES), that the annual mean formation frequency of TCs decreases by about 30% globally but increased in the North Atlantic and TCs with largemaximumsurface winds increase. The Baiu rain band activity tends to intensify and last longer until August, suggesting more damages due to heavy rainfalls in a warmer climate. This is a review paper mainly originated from published articles on tropical cyclone by Oouchi et al. (2006) [26] and on the East Asian summer monsoon by Kusunoki et al. (2006) [17].

scholarly journals Annual Cycle of Rainfall in the Western North Pacific and East Asian Sector

2009 ◽  
Vol 22 (8) ◽  
pp. 2073-2094 ◽  
Author(s):  
Chia Chou ◽  
Li-Fan Huang ◽  
Lishan Tseng ◽  
Jien-Yi Tu ◽  
Pei-Hua Tan
Keyword(s):  
Summer Monsoon ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Tropical Convection ◽  
Monsoon Circulation ◽  
Asian Summer ◽  
Monsoon Gyre

Abstract The annual cycle of precipitation over the western North Pacific and East Asian (WNP–EA) sector has five major periods: spring, the first and second wet periods, fall, and winter. In this study, processes that induce precipitation in each period are examined from a large-scale point of view. The wet phase over this sector has two distinct periods, which are dominated by the Asian summer monsoon circulation induced by the land–ocean contrast of net energy into the atmospheric column (Fnet). In the first wet period, the pre-mei-yu/mei-yu rainband is directly associated with a moisture flux convergence caused by the southwesterly Asian summer monsoon flow and the southeasterly trade winds, and indirectly associated with a dynamic feedback induced by this horizontal moisture convergence. The tropical convection, in the meantime, is associated with a rising motion that is induced by positive Fnet. In the second wet period, the WNP summer monsoon gyre dominates the rainfall of this region, which is partially associated with warmer local sea surface temperature (SST) via positive Fnet. The land–sea contrast of Fnet and the atmosphere–ocean interaction also play an important role in establishing the monsoon gyre. The dry phase over the WNP–EA region is the winter period in which precipitation is associated with winter storm activities and large-scale lifting associated with a pressure surge. In the two transition phases, due to a difference in heat capacity, the atmosphere and ocean have distinct impacts on precipitation, albeit similar solar insolations during the two periods. In the spring period, the atmospheric condition is favorable for convection, while the ocean surface is relatively colder, so the horizontal moisture advection associated with the westward extent of the Pacific subtropical high, which is different from a typical winter frontal system, is a major source for the spring rain. In the fall period, however, the atmospheric conditions dominated by the Asian winter monsoon circulation suppress convection, while relatively warmer SST still maintains tropical convection over the southern part of the WNP–EA region. Over the northern part of the WNP–EA region, the fall precipitation is associated with frontal systems, similar to those in winter.

scholarly journals Role of Thermal Condition over Asia in the Weakening Asian Summer Monsoon under Global Warming Background

2012 ◽  
Vol 25 (9) ◽  
pp. 3431-3436 ◽  
Author(s):  
Zhiyan Zuo ◽  
Song Yang ◽  
Arun Kumar ◽  
Renhe Zhang ◽  
Yan Xue ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Monsoon Circulation ◽  
Tropospheric Temperature ◽  
Climate Forecast System ◽  
Asian Summer ◽  
Asian Summer Monsoon Circulation ◽  
Plausible Reason

The large-scale Asian summer monsoon circulation has experienced a weakening tendency in recent decades. Using observed data and output from model experiments with the atmospheric component of the NCEP Climate Forecast System, the authors show that a relatively smaller warming in Asia compared to the surrounding regions may be a plausible reason for this change in the monsoon. Although the surface temperature over Asia has increased, the landmass has become a relative “heat sink” because of the larger warming in other regions of the world. Indeed, over Asia, the vertically integrated tropospheric temperature in the most recent decades is colder than that in the earlier decades, a feature different from the characteristics outside Asia.

scholarly journals Relative Roles of Land–Sea Distribution and Orography in Asian Monsoon Intensity

2009 ◽  
Vol 66 (9) ◽  
pp. 2714-2729 ◽  
Author(s):  
Zhongfeng Xu ◽  
Congbin Fu ◽  
Yongfu Qian
Keyword(s):  
Indian Ocean ◽  
South Asian ◽  
Summer Monsoon ◽  
Large Scale ◽  
Asian Monsoon ◽  
Asian Summer Monsoon ◽  
Monsoon Circulation ◽  
Eurasian Continent ◽  
The Indian Ocean ◽  
Asian Summer

Abstract The relative impacts of various land–sea distributions (LSDs) and mountains on Asian monsoon extent and intensity are assessed using a series of AGCM simulations. The air–sea coupling effects are not considered in this study. All simulations were integrated with zonal mean SST, globally uniform vegetation, soil color, and, except several simulations, soil texture. The results show that the LSD plays a more fundamental role than orography in determining the extent of Asian and African monsoons. The tropical zonal LSD and Asian mountains both play a crucial role for establishing summer monsoon convection over the South Asian region. The monsoon circulation index (MCI1) defined by the difference of zonal wind between 850 and 200 hPa is used to measure the intensity of the South Asian summer monsoon. The large-scale meridional land–sea thermal contrast between the Eurasian continent and the Indian Ocean only induces a 1.8 m s−1 increase of MCI1. The presence of the Indian subcontinent and Indochina peninsula (Asian mountains), however, induces a 6.6 (7.4) m s−1 increase of MCI1 associated with the release of latent heat of condensation. Clearly, the tropical subcontinental-scale zonal LSD and the Asian mountains almost equally contribute to the increase of MCI1 and play a more important role than the large-scale meridional LSD between the Eurasian continent and the Indian Ocean. Possible mechanisms of how the tropical subcontinental-scale zonal LSD and Asian mountains impact the Asian summer monsoon circulation and precipitation are also discussed.

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