A study on the distinct features of the Asian summer monsoon during the years of extreme monsoon activity over India

Ramesh, K. J.; Mohanty, U. C.; Rao, P. L. S.

doi:10.1007/bf01030142

Cited by 12 publications

(8 citation statements)

References 12 publications

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“…A zone of strong flux divergence is noticed off East Africa. These findings are consistent with earlier studies carried out using different analyses (Mohanty and Ramesh, 1994;Ramesh et al, 1996). The difference (Figure 8(c)) indicates strong flux convergence over western India and the adjoining Arabian Sea.…”

Section: Energeticssupporting

confidence: 83%

“…Further, a detailed comparison of the evolution of certain parameters, such as outgoing longwave radiation, sea surface temperature, stream function anomalies, divergent circulation and precipitation patterns, etc., was carried out by Krishnamurti et al, (1989Krishnamurti et al, ( , 1990 to elucidate some of the differences between dry (1987) and wet (1988) monsoon seasons over India. Ramesh et al (1996) examined the energetics associated with these two extreme monsoon seasons. The data-sparse network over the tropics, especially in the summer monsoon domain, has made studying the finer details of the monsoon difficult.…”

Section: Introductionmentioning

confidence: 99%

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The contrasting features of Asian summer monsoon during surplus and deficient rainfall over India

Raju

Mohanty

Rao

et al. 2002

Intl Journal of Climatology

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An endeavour is made to distinguish the mean summer monsoon features during surplus and deficient monsoon seasons. Based on all-India summer monsoon rainfall, over 42 years , seven surplus and ten deficient monsoon seasons are identified. Making use of daily averaged (00 Z and 12 Z) reanalysis data sets from the National Center for Environmental Prediction-National Center for Atmospheric Research for the corresponding surplus and deficient monsoon seasons, the mean circulation characteristics and large-scale energetics are examined.The circulation features denote that the cross equatorial flow, low-level jet and tropical easterly jet are stronger during a surplus monsoon. Further, strong Tibetan anticyclonic flow characterizes a surplus monsoon. The large-scale balances of kinetic energy, heat and moisture show a significantly large quantity of diabatic heating, adiabatic generation of kinetic energy, and horizontal convergence of heat and moisture during the surplus monsoon season compared with the deficient state. The regions with statistically significant difference between surplus and deficient monsoon seasons are delineated by a Student's t-test at the 95% confidence level. The remarkable aspect noticed in this study is that the Arabian Sea branch of the monsoon circulation is more vigorous during a surplus monsoon season, whereas the eastern Bay of Bengal branch is stronger during a deficient monsoon. The various large-scale budget terms of kinetic energy, heat and moisture are found to be consistent and in agreement with the seasonal monsoon activity over India.

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Section: Energeticssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

The contrasting features of Asian summer monsoon during surplus and deficient rainfall over India

Raju

Mohanty

Rao

et al. 2002

Intl Journal of Climatology

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“…This is adequately represented in the analysis and forecasts as well. These are in good agreement with the observations made in the earlier studies (MOHANTY and RAMESH, 1994;RAMESH et al, 1996). A zone of strong dissipation is observed all along the east African coast.…”

Section: Heat and Moisture Budgetssupporting

confidence: 82%

“…Data are also abundantly available from operational centers (such as ECMWF, NCEP, JMA and BMRC, etc.). Recent studies making use of ECMWF data sets elucidate some interesting aspects of the Asian summer monsoon region (MOHANTY and RAMESH, 1994;RAMESH et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

A Study on the Performance of the NCMRWF Analysis and Forecasting System During Asian Summer Monsoon: Thermodynamic Aspects

Ramesh

Rao

Mohanty³

1999

Pure and Applied Geophysics

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The thermodynamic characteristics of the Asian summer monsoon are examined with a global analysis-forecast system. In this study, we investigated the large-scale balances of heat and moisture by making use of operational analyses as well as forecast fields for June, July and August (JJA), 1994. Apart from elucidating systematic errors in the temperature and moisture fields, the study expounds the influence of these errors on the large-scale budgets of heat and moisture over the monsoon region. The temperature forecasts of the model delineate predominant cooling in the middle and lower tropospheres over the monsoon region. Similarly, the moisture forecasts evince a drying tendency in the lower troposphere. However, certain sectors of moderate moistening exist over the peninsular India and adjoining oceanic sectors of the Arabian Sea and Bay of Bengal.The broad features of the large-scale heat and moisture budgets represented by the analysis/forecast fields indicate good agreement with the observed aspects of the summer monsoon circulation. The model forecasts fail to retain the analyzed atmospheric variability in terms of the mean circulation, which is indicated by underestimation of various terms of heat and moisture budgets with an increase in the forecast period. Further, the forecasts depict an anomalous diabatic cooling layer in the lower middle troposphere of the monsoon region which inhibits vertical transfer of heat and moisture from the mixed layer of the atmospheric boundary layer to the middle troposphere. In effect, the monsoon circulation is considerably weakened with an increase in the forecast period. The treatment of shallow convection and the use of interactive clouds in the model can reduce the cooling bias considerably.

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“…Currently, the availability of globally analyzed upper air meteorological ®elds from various operational weather forecasting centers around the world, enriches the scope of understanding the mechanisms of the otherwise data sparse tropics, especially the monsoon region. Despite the fact that some aspects of energetics and dynamics were addressed in earlier studies (MOHANTY and RAMESH, 1994;Ramesh et al, 1996), a comprehensive understanding is necessary to interpret the Asian summer monsoon circulation in the extended range/seasonal scale simulations. Further, it is also crucial to diagnose the source of errors associated with the seasonal scale simulations and oer plausible explanations.…”

Section: Introductionmentioning

confidence: 99%

The Energetics of Asian Summer Monsoon

Rao¹

2001

Pure appl. geophys.

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Ð In this paper, we examine the large-scale balances of kinetic energy, vorticity, angular momentum, heat and moisture over the Asian summer monsoon region. The ®ve year (1986±1990) uninitialized daily analyses for the summer season comprising June, July and August (JJA), produced at the European Centre for Medium Range Weather Forecasts (ECMWF) under the aegis of Tropical Ocean and Global Atmosphere (TOGA) have been considered to carry out the study.The following features characterize the Asian summer monsoon domain. It acts as the source of kinetic energy as well as vorticity, and sink of heat and moisture. Kinetic energy and vorticity are produced in the monsoon region and transported horizontally. On the contrary, heat and moisture are transported into the monsoon region. The zonal and meridional components of adiabatic generation of kinetic energy contribute to the production of kinetic energy over the Arabian Sea and Bay of Bengal, respectively. The horizontal advection of relative vorticity is balanced by sub-grid scale generation. The angular momentum generated due to pressure torque (east-west pressure gradient) is balanced by the¯ux convergence of omega momentum. Further, the angular momentum budget delineates that¯ux convergence of relative momentum is necessary to maintain the surface westerlies against the friction. The horizontal convergence of heat and moisture facilitates enhancement of diabatic heating, and also leads to the formation of diabatic heat sources, which are crucial to sustain the summer monsoon circulation.

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A study on the distinct features of the Asian summer monsoon during the years of extreme monsoon activity over India

Cited by 12 publications

References 12 publications

The contrasting features of Asian summer monsoon during surplus and deficient rainfall over India

The contrasting features of Asian summer monsoon during surplus and deficient rainfall over India

A Study on the Performance of the NCMRWF Analysis and Forecasting System During Asian Summer Monsoon: Thermodynamic Aspects

The Energetics of Asian Summer Monsoon

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