Role of Warming over the Tibetan Plateau in Early Onset of the Summer Monsoon over the Bay of Bengal and the South China Sea

Ueda, Hiroaki; Yasunari, Tetsuzo

doi:10.2151/jmsj1965.76.1_1

Cited by 101 publications

(72 citation statements)

References 30 publications

(34 reference statements)

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“…The pre-monsoon rainfall commences first over the Indochina Peninsula (*105°E) in April, which is consistent with the observational evidence (e.g., Matsumoto 1997). Subsequently, the planetary-scale monsoon onset, called the first transition (Lau et al 1998), occurs in mid-May with the enhancement of rainfall and intensification of the monsoon westerlies, bearing considerable resemblance with the observations (Li and Yanai 1996;Ueda and Yasunari 1998). The summer monsoon terminates in the end of September, and succeeding seasons are characterized by the dominance of easterlies.…”

Section: The Mri-aogcm and Boundary Conditionssupporting

confidence: 87%

Seasonally asymmetric transition of the Asian monsoon in response to ice age boundary conditions

et al. 2010

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Modulation of a monsoon under glacial forcing is examined using an atmosphere-ocean coupled general circulation model (AOGCM) following the specifications established by Paleoclimate Modelling Intercomparison Project phase 2 (PMIP2) to understand the air-sea-land interaction under different climate forcing. Several sensitivity experiments are performed in response to individual changes in the continental ice sheet, orbital parameters, and sea surface temperature (SST) in the Last Glacial Maximum (LGM: 21 ka) to evaluate the driving mechanisms for the anomalous seasonal evolution of the monsoon. Comparison of the model results in the LGM with the pre-industrial (PI) simulation shows that the Arabian Sea and Bay of Bengal are characterized by enhancement of pre-monsoon convection despite a drop in the SST encompassing the globe, while the rainfall is considerably suppressed in the subsequent monsoon period. In the LGM winter relative to the PI, anomalies in the meridional temperature gradient (MTG) between the Asian continents minus the tropical oceans become positive and are consistent with the intensified pre-monsoon circulation. The enhanced MTG anomalies can be explained by a decrease in the condensation heating relevant to the suppressed tropical convection as well as positive insolation anomalies in the higher latitude, showing an opposing view to a warmer future climate. It is also evident that a latitudinal gradient in the SST across the equator plays an important role in the enhancement of pre-monsoon rainfall. As for the summer, the sensitivity experiments imply that two ice sheets over the northern hemisphere cools the air temperature over the Asian continent, which is consistent with the reduction of MTG involved in the attenuated monsoon. The surplus pre-monsoon convection causes a decrease in the SST through increased heat loss from the ocean surface; in other words, negative ocean feedback is also responsible for the subsequent weakening of summer convection.

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Section: The Mri-aogcm and Boundary Conditionssupporting

confidence: 87%

Seasonally asymmetric transition of the Asian monsoon in response to ice age boundary conditions

et al. 2010

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“…From observational analyses, Li and Yanai (1996), Ueda and Yasunari (1998) and other previous studies have suggested that the first transition of the planetary monsoon (Lau et al 1998) observed in mid-May, concurrent with the reversal of the meridional thermal gradient over the broadscale Asian monsoon domain is strongly linked to the SCS monsoon onset. Therefore, we also examine the timing of the planetary-scale monsoon onset in the CGCMs.…”

Section: Comparison Of the Stepwise Seasonal Changesmentioning

confidence: 81%

Evaluation for the Seasonal Evolution of the Summer Monsoon over the Asian and Western North Pacific Sector in the WCRP CMIP3 Multi-model Experiments

Inoue

Ueda

2009

Journal of the Meteorological Society of Japan

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Based on the World Climate Research Programme's (WCRP's) Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model dataset, evaluation for the summer monsoon over the Asian and western North Pacific (WNP) sectors is made in terms of reproducibility of the seasonal mean structure. Also investigated is a stepwise eastward progress of convection center from the Indian Ocean toward the WNP in the course of the maturing process of the continental and oceanic monsoons.Most models roughly reproduce seasonal mean broad-scale features on the Asian summer monsoon (ASM), but lower-tropospheric circulation over East Asia (EA) through the WNP and the location and intensity of the North Pacific subtropical high exhibit large inter-model variability. Some of the models fail to reproduce a reversal of the upper-tropospheric meridional temperature gradient over the South Asia and the North Indian Ocean sector. Metrics on the reproducibility of lower-tropospheric circulation of the ASM are also presented, in order to evaluate the reproducibility of the ASM circulation quantitatively.The large inter-model variability over the EA-WNP domains could be attributed to insu‰cient reproducibility of the oceanic monsoon. In most of the models, the stepwise eastward progress of convection over the South China Sea and WNP commences in May almost concurrently with large-scale circulation, whereas the eastward progress of convection is faster in most of the models than in the observation over the WNP. It is suggested that a teleconnection pattern associated with an intensification of convective activity over the WNP in mid-July is one of the key phenomena in both the observation and the coupled models, given the withdrawal of the Baiu rainy season around Japan. The analysis based on metrics concerning the stepwise eastward progress of convection over the WNP and its vicinity suggests that these models still have some di‰culties in reproducing the stepwise eastward progress of convection accurately.

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“…This reversal intensifies the Asian summer monsoon circulation. The heating effect is also significantly associated with the timing of the Asian summer monsoon [e.g., Li and Yanai, 1996;Ueda and Yasunari, 1998]. Minoura et al [2003] reported that an increase in the surface temperature and dry intrusion in the 600-850 hPa layer over the Arabian Sea (AS), the Bay of Bengal (BB), and the Indian subcontinent (ID) can play a crucial role in enhancing convective instability prior to the onset of the Indian summer monsoon.…”

Section: Introductionmentioning

confidence: 99%

Effects of the Tibetan Plateau on the onsetof the summer monsoon in South Asia: The role of the air‐sea interaction

et al. 2013

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[1] Using both a coupled atmosphere-ocean general circulation model (GCM) and an atmospheric GCM, we investigate the effects of the Tibetan Plateau (TP) on the onset of the South Asian summer monsoon by conducting simulations with and without the TP. In the coupled GCM, the presence of the TP causes the monsoon onset to occur approximately 15 days later in the Arabian Sea (AS) and India (ID) and approximately 10 days earlier in the Bay of Bengal (BB). These changes are attributed to different atmospheric circulation patterns and different conditions within the adjacent oceans, such as the AS and the BB. When the TP is included, lower sea surface temperatures (SSTs) in the AS contribute to a stable lower atmosphere, which suppresses convection over the AS and ID in May. In contrast, low pressure over South Asia, caused by the TP, induces a southwesterly toward the BB that transports a substantial amount of water vapor to the BB. This flow results in an earlier monsoon in the BB. Without the TP, higher SSTs that are formed in the AS in May destabilize the lower atmosphere and create a depression, resulting in an earlier onset of the monsoon over the AS and ID. Consequently, the cyclonic circulation spreads abruptly to the BB, and precipitation begins to increase over the BB. Therefore, the air-sea interaction in the adjacent ocean under the influence of the TP strongly modulates the onset of the South Asian summer monsoon. This modulation was verified by the atmospheric GCM experiments.Citation: Abe, M., M. Hori, T. Yasunari, and A. Kitoh (2013), Effects of the Tibetan Plateau on the onset of the summer monsoon in South Asia: The role of the air-sea interaction,

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Role of Warming over the Tibetan Plateau in Early Onset of the Summer Monsoon over the Bay of Bengal and the South China Sea

Cited by 101 publications

References 30 publications

Seasonally asymmetric transition of the Asian monsoon in response to ice age boundary conditions

Seasonally asymmetric transition of the Asian monsoon in response to ice age boundary conditions

Evaluation for the Seasonal Evolution of the Summer Monsoon over the Asian and Western North Pacific Sector in the WCRP CMIP3 Multi-model Experiments

Effects of the Tibetan Plateau on the onsetof the summer monsoon in South Asia: The role of the air‐sea interaction

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