Some Aspects of the Monsoon Circulation and Monsoon Rainfall

1978 ◽  
pp. 1209-1249
Author(s):  
R. Ananthakrishnan
Keyword(s):  
Monsoon Rainfall ◽  
Monsoon Circulation

scholarly journals ISO-Modulating Effects on the East Asian Summer Monsoon Circulation Patterns Associated with Southern Taiwan’s Monsoon Rainfall

2014 ◽  
Vol 142 (9) ◽  
pp. 3163-3177 ◽  
Author(s):  
Ken-Chung Ko ◽  
Po-Sheng Chiu
Keyword(s):  
Summer Monsoon ◽  
Monsoon Rainfall ◽  
Southern China ◽  
Low Pressure ◽  
Monsoon Trough ◽  
Central China ◽  
Monsoon Circulation ◽  
Circulation Patterns ◽  
Southern Taiwan ◽  
Southern Flank

In this study, the circulation patterns of the summer monsoon associated with monsoon rainfall in southern Taiwan were analyzed and two types of monsoon patterns were defined. The first type was characterized by a broad low pressure area extending northeastward from a low pressure center near southern China to southern Japan. Strong southwesterly flows were observed over the southern flank of the monsoon trough. The second type of monsoon pattern was characterized by a strong westward-extending anticyclone in the area north of Taiwan (including central China, South Korea, and Japan), and a weaker east–west-elongated monsoon trough south of Taiwan, driving the easterly flow to southern Taiwan. The modulating effect of intraseasonal oscillations (ISOs) on these monsoon flow patterns indicates that as ISOs propagate northwestward toward southern China, they create favorable conditions for developing and strengthening southwesterly flows and convection. However, because of the latitudinal limit of northwestward-propagating ISOs, only the edge of the strongest convection over the southern flank of the ISO cyclonic circulation reaches southern Taiwan during the westerly phase. Thus, although the westerly ISO pattern appears to be stronger than the easterly pattern, it brings less rainfall to southern Taiwan. Through the tightening of pressure gradients, the ISO typically generates anomalous cyclones (anticyclones) that can affect the southwesterly and northeasterly flows near its southern (northern) and northern (southern) rims. Therefore, fluctuations in the low-frequency background flow can exert a notable effect on the monsoon rainfall and associated circulation systems near Taiwan.

Some aspects of the monsoon circulation and monsoon rainfall

1977 ◽  
Vol 115 (5-6) ◽  
pp. 1209-1249 ◽  
Author(s):  
R. Ananthakrishnan
Keyword(s):  
Monsoon Rainfall ◽  
Monsoon Circulation

Performance of the New NCAR CAM3.5 in East Asian Summer Monsoon Simulations: Sensitivity to Modifications of the Convection Scheme

2010 ◽  
Vol 23 (13) ◽  
pp. 3657-3675 ◽  
Author(s):  
Haoming Chen ◽  
Tianjun Zhou ◽  
Richard B. Neale ◽  
Xiaoqing Wu ◽  
Guang Jun Zhang
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Monsoon Rainfall ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Model Performance ◽  
Seasonal Migration ◽  
Monsoon Circulation ◽  
Convection Scheme ◽  
Asian Summer

Abstract The performance of an interim version of the NCAR Community Atmospheric Model (CAM3.5) in simulating the East Asian summer monsoon (EASM) is assessed by comparing model results against observations and reanalyses. Both the climate mean states and seasonal cycle of major EASM components are evaluated. Special attention is paid to the sensitivity of model performance to changes in the convection scheme. This is done by analyzing four CAM3.5 runs with identical dynamical core and physical packages but different modifications to their convection scheme, that is, the original Zhang–McFarlane (ZM) scheme, Neale et al.’s modification (NZM), Wu et al.’s modification (WZM), and Zhang’s modification (ZZM). The results show that CAM3.5 can capture the major climate mean states and seasonal features of the EASM circulation system, including reasonable simulations of the Tibetan high in the upper troposphere and the western Pacific subtropical high (WPSH) in the middle and lower troposphere. The main deficiencies are found in monsoon rainfall and the meridional monsoon cell. The weak meridional land–sea thermal contrasts in the model contribute to the weaker monsoon circulation and to insufficient rainfall in both tropical and subtropical regions of EASM. The seasonal migration of rainfall, as well as the northward jump of the WPSH from late spring to summer, is reasonably simulated, except that the northward jump of the monsoon rain belt still needs improvement. Three runs using modified schemes generally improve the model performance in EASM simulation compared to the control run. The monsoon rainfall distribution and its seasonal variation are sensitive to modifications of the ZM convection scheme, which is most likely due to differences in closure assumptions. NZM, which uses a convective available potential energy (CAPE)-based closure assumption, performs better in tropical regions where the rainfall is closely related to CAPE. However, WZM and ZZM, which use quasi-equilibrium (QE) closure, have more realistic subtropical rainfall in the mei-yu/baiu/changma front region, mainly because the rainfall in the subtropics is more sensitive to the rate of destabilization by the large-scale flow.

scholarly journals The Delayed Effect of Major El Niño Events on Indian Monsoon Rainfall

2010 ◽  
Vol 23 (4) ◽  
pp. 932-946 ◽  
Author(s):  
Hyo-Seok Park ◽  
John C. H. Chiang ◽  
Benjamin R. Lintner ◽  
Guang J. Zhang
Keyword(s):  
El Niño ◽  
Monsoon Rainfall ◽  
Indian Monsoon ◽  
El Nino ◽  
Monsoon Season ◽  
Monsoon Circulation ◽  
Indian Monsoon Rainfall ◽  
El Niño Events ◽  
Moist Processes ◽  
El Nino Events

Abstract Previous studies have shown that boreal summer Indian monsoon rainfall is, on average, significantly above normal after major El Niño events. In this study, the underlying causes of this rainfall response are examined using both observational analysis and atmospheric general circulation model (AGCM) simulations. Moist static energy budgets for two strong El Niño events (1982/83 and 1997/98), estimated from monthly 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40), suggest that stronger low-level moisture transport and reduced moist stability associated with a warmer north Indian Ocean (NIO) can increase monsoon rainfall, despite a weakened monsoon circulation. The trade-off between a dynamically weaker monsoon and moist processes favoring enhanced monsoonal rainfall is broken during the late monsoon season (August–September) as the warm NIO enhances surface latent heat flux and the monsoon circulation relaxes back to the climatological mean. The monsoon circulation strength and the moist processes work together in the late season, which explains the observed tendency for monsoonal rainfall increases during the late monsoon season after strong winter El Niño conditions. Idealized AGCM experiments with a fixed-depth ocean mixed layer demonstrate that the remnant but weaker-than-peak warm SSTs in the eastern equatorial Pacific during spring and the early summer following winter El Niños substantially contribute to the NIO warming. The results suggest that local air–sea interactions in the tropical Indian Ocean after winter El Niño are strongly dependent on the details of El Niño’s decaying trend.

Weakening of North Indian SST Gradients and the Monsoon Rainfall in India and the Sahel

2006 ◽  
Vol 19 (10) ◽  
pp. 2036-2045 ◽  
Author(s):  
Chul Eddy Chung ◽  
V. Ramanathan
Keyword(s):  
Indian Ocean ◽  
South Asian ◽  
Radiative Forcing ◽  
Climate Model ◽  
Monsoon Rainfall ◽  
Equatorial Indian Ocean ◽  
Sub Saharan Africa ◽  
Monsoon Circulation ◽  
Sub Saharan ◽  
Sst Gradient

Abstract Sea surface temperatures (SSTs) in the equatorial Indian Ocean have warmed by about 0.6–0.8 K since the 1950s, accompanied by very little warming or even a slight cooling trend over the northern Indian Ocean (NIO). It is reported that this differential trend has resulted in a substantial weakening of the meridional SST gradient from the equatorial region to the South Asian coast during summer, to the extent that the gradient has nearly vanished recently. Based on simulations with the Community Climate Model Version 3 (CCM3), it is shown that the summertime weakening in the SST gradient weakens the monsoon circulation, resulting in less monsoon rainfall over India and excess rainfall in sub-Saharan Africa. The observed trend in SST is decomposed into a hypothetical uniform warming and a reduction in the meridional gradient. The uniform warming of the tropical Indian Ocean in the authors’ simulations increases the Indian summer monsoon rainfall by 1–2 mm day−1, which is opposed by a larger drying tendency due to the weakening of the SST gradient. The net effect is to decrease the Indian monsoon rainfall, while preventing the sub-Saharan region from becoming too dry. Published coupled ocean–atmosphere model simulations are used to describe the competing effects of the anthropogenic radiative forcing due to greenhouse gases and the anthropogenic South Asian aerosols on the observed SST gradient and the monsoon rainfall.

scholarly journals Relationship between surface fields over Indian ocean and monsoon rainfall over homogeneous zones of India

MAUSAM ◽  
2022 ◽  
Vol 53 (2) ◽  
pp. 133-144
Author(s):  
S. K. DASH ◽  
M. S. SHEKHAR ◽  
G. P. SINGH ◽  
A. D. VERNEKAR
Keyword(s):  
Indian Ocean ◽  
Monsoon Rainfall ◽  
Surface Wind ◽  
Monsoon Circulation ◽  
Sea Level Pressure ◽  
Surface Parameters ◽  
Pressure Surface ◽  
Surface Wind Stress ◽  
The Indian Ocean ◽  
Surface Fields

The monthly mean atmospheric fields and surface parameters of NCEP/NCAR reanalysis for the period 1948-1998 have been studied to examine the characteristics of monsoon circulation features, sea surface temperature (SST), sea level pressure, surface wind stress and latent heat flux over the Indian Ocean and nearby seas during deficient, normal and excess rain years. The entire period of study has been classified into deficient, normal and excess rain years for all India as well as for each of the five homogeneous zones separately based on the observed seasonal mean rainfall. On the basis of the mean characteristics of the surface fields, the oceanic region covering the Indian Ocean and adjacent seas has been divided into four regional sectors. Using various statistical means the relation between the surface fields over the four regional sectors and the monsoon rainfall over five homogeneous zones of Indian landmass has been examined. Attempt have been made to identify some surface parameters which can be used as predictors for seasonal mean monsoon rainfall over the entire India and also over some homogeneous zones.

scholarly journals Understanding Future Change of Global Monsoons Projected by CMIP6 Models

2020 ◽  
Vol 33 (15) ◽  
pp. 6471-6489 ◽  
Author(s):  
Bin Wang ◽  
Chunhan Jin ◽  
Jian Liu
Keyword(s):  
North American ◽  
Rainy Season ◽  
Monsoon Rainfall ◽  
North American Monsoon ◽  
Convective Heating ◽  
Monsoon Circulation ◽  
Future Change ◽  
Global Monsoon ◽  
African Monsoon ◽  
The Future

AbstractProjecting future change of monsoon rainfall is essential for water resource management, food security, disaster mitigation, and infrastructure planning. Here we assess the future change and explore the causes of the changes using 15 models that participated in phase 6 of the Coupled Model Intercomparison Project (CMIP6). The multimodel ensemble projects that, under the shared socioeconomic pathway (SSP) 2–4.5, the total land monsoon rainfall will likely increase in the Northern Hemisphere (NH) by about 2.8% per one degree Celsius of global warming (2.8% °C−1) in contrast to little change in the Southern Hemisphere (SH; −0.3% °C−1). In addition, in the future the Asian–northern African monsoon likely becomes wetter while the North American monsoon becomes drier. Since the humidity increase is nearly uniform in all summer monsoon regions, the dynamic processes must play a fundamental role in shaping the spatial patterns of the global monsoon changes. Greenhouse gas (GHG) radiative forcing induces a “NH-warmer-than-SH” pattern, which favors increasing the NH monsoon rainfall and prolonging the NH monsoon rainy season while reducing the SH monsoon rainfall and shortening the SH monsoon rainy season. The GHG forcing induces a “land-warmer-than-ocean” pattern, which enhances Asian monsoon low pressure and increases Asian and northern African monsoon rainfall, and an El Niño–like warming, which reduces North American monsoon rainfall. The uncertainties in the projected monsoon precipitation changes are significantly related to the models’ projected hemispheric and land–ocean thermal contrasts as well as to the eastern Pacific Ocean warming. The CMIP6 models’ common biases and the processes by which convective heating drives monsoon circulation are also discussed.

scholarly journals The Indian summer monsoon rainfall: interplay of coupled dynamics, radiation and cloud microphysics

2005 ◽  
Vol 5 (3) ◽  
pp. 2879-2895 ◽  
Author(s):  
P. K. Patra ◽  
S. K. Behera ◽  
J. R. Herman ◽  
S. Maksyutov ◽  
H. Akimoto ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Prediction Models ◽  
Monsoon Rainfall ◽  
Indian Summer Monsoon Rainfall ◽  
Cloud Microphysics ◽  
Summer Monsoon Rainfall ◽  
Wave Radiation ◽  
Droplet Growth ◽  
Monsoon Circulation

Abstract. The Indian summer monsoon rainfall (ISMR), which has a strong connection to agricultural food production, has been less predictable by conventional models in recent times. Two distinct years 2002 and 2003 with lower and higher July rainfall, respectively, are selected to help understand the natural and anthropogenic influences on ISMR. We show that heating gradients along the meridional monsoon circulation are reduced due to aerosol radiative forcing and the Indian Ocean Dipole in 2002. An increase in the dust and biomass-burning component of the aerosols through the zonal monsoon circulation resulted in reduction of cloud droplet growth in July 2002. These conditions were opposite to those in July 2003 which led to an above average ISMR. In this study, we have utilized NCEP/NCAR reanalyses for meteorological data (e.g. sea-surface temperature, horizontal winds, and precipitable water), NOAA interpolated outgoing long-wave radiation, IITM constructed all-India rainfall amounts, aerosol parameters as observed from the TOMS and MODIS satellites, and ATSR fire count maps. Based on this analysis, we suggest that monsoon rainfall prediction models should include synoptic as well as interannual variability in both atmospheric dynamics and chemical composition.

scholarly journals Observed and model simulated inter-annual variability of the Indian monsoon

MAUSAM ◽  
2021 ◽  
Vol 52 (1) ◽  
pp. 133-150
Author(s):  
V. KRISHNAMURTHY ◽  
J. SHUKLA
Keyword(s):  
Interannual Variability ◽  
Summer Monsoon ◽  
General Circulation ◽  
Monsoon Rainfall ◽  
Indian Summer Monsoon Rainfall ◽  
Circulation Model ◽  
Summer Monsoon Rainfall ◽  
Monsoon Circulation ◽  
Global Response ◽  
Tropical Sst Anomalies

The Center for Ocean-Land-Atmosphere (COLA) general circulation model has been integrated seven times with observed global sea surface temperature (SST) for the years 1979-98. The model-simulated annual cycle, the seasonal mean and the interannual variability of the summer monsoon rainfall and circulation over the Indian region are compared with the corresponding observations. It if found that, although this model has shown remarkable success in simulating the local and global response of tropical SST anomalies, the model shows poor skill in simulating the interannual variability of monsoon rainfall over India. While it is true that the correlation between the observed tropical Pacific SST and the Indian summer monsoon rainfall for the most recent 20 years itself is considerably over India is largely related to the systematic errors of the model in simulating the climatological mean monsoon circulation and rainfall, especially over the oceanic regions.

scholarly journals The Indian summer monsoon rainfall: interplay of coupled dynamics, radiation and cloud microphysics

2005 ◽  
Vol 5 (8) ◽  
pp. 2181-2188 ◽  
Author(s):  
P. K. Patra ◽  
S. K. Behera ◽  
J. R. Herman ◽  
S. Maksyutov ◽  
H. Akimoto ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Prediction Models ◽  
Monsoon Rainfall ◽  
Indian Summer Monsoon Rainfall ◽  
Cloud Microphysics ◽  
Summer Monsoon Rainfall ◽  
Wave Radiation ◽  
Droplet Growth ◽  
Monsoon Circulation

Abstract. The Indian summer monsoon rainfall (ISMR), which has a strong connection to agricultural food production, has been less predictable by conventional models in recent times. Two distinct years 2002 and 2003 with lower and higher July rainfall, respectively, are selected to help understand the natural and anthropogenic influences on ISMR. We show that heating gradients along the meridional monsoon circulation are reduced due to aerosol radiative forcing and the Indian Ocean Dipole in 2002. An increase in the dust and biomass-burning component of the aerosols through the zonal monsoon circulation resulted in reduction of cloud droplet growth in July 2002. These conditions were opposite to those in July 2003 which led to an above average ISMR. In this study, we have utilized NCEP/NCAR reanalyses for meteorological data (e.g. sea-surface temperature, horizontal winds, and precipitable water), NOAA interpolated outgoing long-wave radiation, IITM constructed all-India rainfall amounts, aerosol parameters as observed from the TOMS and MODIS satellites, and ATSR fire count maps. Based on this analysis, we suggest that monsoon rainfall prediction models should include synoptic as well as interannual variability in both atmospheric dynamics and chemical composition.

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