The Simulated Indian Monsoon: A GCM Sensitivity Study

Fennessy, M. J.; Kinter, James L.; Kirtman, Ben P.; Marx, L.; Nigam, Sumant; Schneider, Eric D.; Shukla, J.; Straus, David M.; Vernekar, Anandu D.; Xue, Yongkang; Zhou, Jiayu

doi:10.1175/1520-0442(1994)007<0033:tsimag>2.0.co;2

Cited by 114 publications

(56 citation statements)

References 19 publications

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“…The weaker and more realistic large-scale monsoon at T63s is also confirmed by the smaller V-index ( Table 3) and suggests that the large-scale dynamical monsoon weakens when smoother orography is used in the model. These findings are opposite to those of Bhaskar Rao (1991) and Fennessy et al (1994), who found stronger upper-level easterlies and low-level wasterlies in the mean orography case compared to the enhanced orography case. Another noteworthy feature of the T63s simulation is the northward position of the strengthened Tibetan anticyclone (Fig.…”

Section: A Smooth Mountain Experiment: T 63scontrasting

confidence: 96%

“…The Tibetan plateau is present in T63s but is considerably smoother than at T63 -for example, the southern slopes of the Tibetan plateau have a mean gradient of 3m/km at T21 (or T63s) resolution compared to 10m/km at T63 resolution. Hence, the difference between T63s and T63 is not strictly comparable to previous mountain-no mountain studies (Murakami et al, 1970;Hahn and Manabe, 1975;Sadler and Ramage, 1976; and others) but is more comparable to sensitivity studies of mean versus envelope/silhouette orography (WMO 1992, 93;Bhaskar Rao et al, 1991;Fennessy et al, 1994). Silhouette/enhanced orography has steeper slopes and higher peaks because it uses the maximum value in the grid box rather than the mean, and is similar to the envelope orography proposed by Wallace et al (1983) which adds a fraction of the sub-gridscale standard deviation to the mean orography.…”

Section: A Smooth Mountain Experiment: T 63ssupporting

confidence: 52%

“…It could be that the increased precipitation over India is a local effect due to regionally increased orography, and in general such orography is poorly represented in coarse resolution GCMs. For example, the difference between enhanced and mean orography over India is less than 250m in Fennessy et al (1994), whereas it exceeds 300m in T63-T63s. Orography, however, does not explain the large increase in precipitation over the equator and the decrease over the Phillipines.…”

Section: A Smooth Mountain Experiment: T 63smentioning

confidence: 99%

“…This is in agreement with the results of Bhaskar Rao et al (1991) who found an increase over the Indian sub-continent with enhanced orography, mainly due to enhanced moisture convergence. However, Fennessy et al (1994) found that enhanced orography led to a decrease in precipitation over the entire Indian peninsula by at least 3mm/day, and ascribed this to dynamicallyinduced changes in the orographically forced stationary waves. It could be that the increased precipitation over India is a local effect due to regionally increased orography, and in general such orography is poorly represented in coarse resolution GCMs.…”

Section: A Smooth Mountain Experiment: T 63smentioning

confidence: 99%

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Simulation of the Asian Summer Monsoon and its Dependence on Model Horizontal Resolution

Stephenson

Chauvin

Royer

1998

Journal of the Meteorological Society of Japan

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The 1986-1989 Asian summer monsoons have been simulated using a state-of-the-art atmospheric General Circulation Model (GCM), spectrally truncated at 63, 42, 31 and 21 total wavenumbers, corresponding to horizontal resolutions ranging from 200-600km. The mean June-September Asian monsoons have been analyzed and compared to the observed mean monsoon behaviour. Large-scale features such as the lower tropospheric westerly jet, the upper tropospheric tropical easterlies, the Tibetan anticyclone, and copious rainfall over continental Asia are captured by the model at all resolutions. As the resolution is increased, the core of the low-level westerly jet moves towards Somalia and becomes more realistic. The model, however, produces excessive precipitation over the equatorial Indian Ocean and over the southern slopes of the Tibetan plateau, and these errors become accentuated at higher resolution. Furthermore, the monsoon is displaced southward at higher resolutions as is clearly evidenced by a shift in the position of the Tibetan anticyclone. A budget analysis of the upper-level vorticity suggests that this may be related to the excessive ascent over the southern slopes of the Tibetan plateau. A smooth orography test has been made at T63 truncation using T21 truncated orography, in order to assess the contribution due to orographic changes. Smooth orography alleviates the excessive precipitation over the southern slopes of the Tibetan plateau and has a strong and generally beneficial impact on the monsoon over land. It also gives large-scale dynamical monsoon indices in better agreement with observations, yet does not alleviate the excessive precipitation over the equatorial Indian Ocean. The excessive oceanic precipitation is partly due to a systematic intensification of the equatorial convergence zones with increased resolution, yet this appears to be only weakly coupled to the dynamics of the monsoon circulation.

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Section: A Smooth Mountain Experiment: T 63scontrasting

confidence: 96%

Section: A Smooth Mountain Experiment: T 63ssupporting

confidence: 52%

Section: A Smooth Mountain Experiment: T 63smentioning

confidence: 99%

Section: A Smooth Mountain Experiment: T 63smentioning

confidence: 99%

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Simulation of the Asian Summer Monsoon and its Dependence on Model Horizontal Resolution

Stephenson

Chauvin

Royer

1998

Journal of the Meteorological Society of Japan

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“…E-mail: satyabanb@cdac.in better seasonal simulations in the tropics over sufficiently large areal and seasonal average basis. Beginning from 1980, several Atmospheric General Circulation Models (AGCMs) have been used in different countries to simulate the Indian summer monsoon (ISM) circulation and Indian summer monsoon rainfall (ISMR) with different resolutions and model physics (Fennessy et al, 1994;Goswami, 1998;Sabre et al, 2000;Wang et al, 2005;Sajani et al, 2007;Rajendran et al, 2008 and several others). The studies of Gadgil and Sajani (1998) and Kang et al (2002), which analysed the Atmospheric Model Intercomparison Project (AMIP) model results, showed that most of the AGCMs are capable of simulating the regional structure of the ISM circulation and precipitation regimes.…”

Section: Introductionmentioning

confidence: 99%

Dynamical simulation of Indian summer monsoon circulation, rainfall and its interannual variability using a high resolution atmospheric general circulation model

Ratna

Sikka

Dalvi

et al. 2011

Intl Journal of Climatology

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This paper discusses the simulations of Indian summer monsoon (ISM) using a high-resolution National Center for Environmental Prediction (NCEP) T170/L42 model for a 20-year period (1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) with observed Sea Surface Temperature (SSTs) as boundary conditions and using five initial conditions in the first week of May. Good agreement is found between the observed and simulated climatologies. Interannual variability (IAV) of the ISM rainfall as simulated in individual ensemble members and as provided by ensemble average shows that the two series are found to agree well; however, the simulation of the actual observed year-to-year variability is poor. The model simulations do not show much skill in the simulation of drought and excess monsoon seasons. One aspect which has emerged from the study is that where dynamical seasonal prediction has specific base for the large areal and temporal averages, the technique is not to be stretched for application on short areal scale such as that of a cluster of a few grid point. Monsoon onset over Kerala (MOK) coast of India and advance from Kerala coast to northwest India is discussed based on ensemble average and individual ensemble member basis. It is suggested that the model is capable of realistically simulating these processes, particularly if ensemble average is used, as the intermember spread in the ensemble members is large. In short, the high-resolution model appears to provide better climatology and its magnitude of IAV, which compares favourably with observations, although year-to-year matching of the observed and simulated seasonal/monthly rainfall totals for India as a whole is not good.

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Seasonal and regional responses to changes in Australian soil moisture conditions

Simmonds

Hope

1998

Int. J. Climatol.

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The Simulated Indian Monsoon: A GCM Sensitivity Study

Cited by 114 publications

References 19 publications

Simulation of the Asian Summer Monsoon and its Dependence on Model Horizontal Resolution

Simulation of the Asian Summer Monsoon and its Dependence on Model Horizontal Resolution

Dynamical simulation of Indian summer monsoon circulation, rainfall and its interannual variability using a high resolution atmospheric general circulation model

Seasonal and regional responses to changes in Australian soil moisture conditions

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