Circulation and Energy Balance in a Tropical Monsoon

Berson, F. A.

doi:10.1111/j.2153-3490.1961.tb00109.x

Cited by 6 publications

(2 citation statements)

References 8 publications

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“…In the 1960s, several studies (e.g. Berson 1961) showed that the Australian summer monsoon has similarities to the Asian summer monsoon, such as its abrupt poleward shift, sudden onset over a large region and intraseasonal active-break periods.…”

Section: Introductionmentioning

confidence: 99%

Factors contributing to the onset of the Australian summer monsoon

Hung¹,

Yanai²

2004

Quart J Royal Meteoro Soc

107

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SUMMARYUsing the reanalyses from the European Centre for Medium-Range Weather Forecasts, outgoing longwave radiation (OLR) and precipitation data for 1979-93, this paper examines major factors contributing to the onset of the Australian summer monsoon. The low-level (850 hPa) westerly wind and convective activity (OLR, precipitation) over a region in northern Australia (NAU) are used to determine the onset dates. Composite results are then derived, based on these dates. Daily apparent heat source and apparent moisture sink values are obtained as residuals of the large-scale heat and moisture budgets to help clarify the roles of the various heating processes in the onset. Four major factors contributing to the onset are identi ed: (1) land-sea thermal contrast, (2) barotropic instability, (3) arrival of the Madden-Julian oscillation (MJO) and (4) intrusion of midlatitude troughs. The thermal contrast due to differential heating between land and sea acts as a seasonal preconditioning for the onset. The sensible heating over the continent leads to a reversal of meridional temperature gradient between the Australian continent and the Arafura Sea in a layer below 800 hPa in September-March, and sets up a thermally induced meridional-vertical circulation which helps to transport low-level moist air inland. The barotropic instability criterion is often met at 850 hPa in NAU several days prior to the onset. The sudden onset is then triggered by the arriving MJO and at times by the intrusion of a midlatitude trough.

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Section: Introductionmentioning

confidence: 99%

Factors contributing to the onset of the Australian summer monsoon

Hung¹,

Yanai²

2004

Quart J Royal Meteoro Soc

107

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show abstract

“…Prior to the First GARP Global Experiment (FGGE), most of the synoptic studies on the Southern Hemisphere summer monsoon focused on the local circulation features over limited areas such as Indonesia and/or northern Australia (e.g., Bryant, 1958;Berson, 1961;Falls, 1970). The FGGE data represent the best data quality and coverage ever obtained over the Southern Hemisphere summer monsoon region.…”

Section: Introductionmentioning

confidence: 99%

Heat, Moisture, and Vorticity Budget Before and After the Onset of the 1978-79 Southern Hemisphere Summer Monsoon1

Murakami

Iwashima

Nakazawa³

1984

Journal of the Meteorological Society of Japan

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A step-like increase in the 850mb zonal mean westerlies over the equatorial Southern Hemisphere (3.75*-11.25*S, 90*E-180*) occurred between 22-30 December 1978. This event was used to subjectively define the onset for the 1978-79 Southern Hemisphere monsoon. During the onset period, widespread increases in 850mb cross-equatorial northerlies occurred over the western Pacific between 120*E and the dateline, reflecting the intensified low-level Hadley circulation after the onset. Over the maritime continent (Sumatra, Borneo, New Guinea), the large-scale apparent heating rate (Q1) decreased considerably from the pre-to post-onset phase. By contrast, drastic intensification in Q1 heat sources took place near Cape York Peninsula and the equatorial South Pacific east of Australia, with a maximum heating rate of about 4* per day at 447mb. The spatial distribution of the large-scale apparent moisture sources (Q2) exhibits a parallel feature to that of the Q1 pattern for both the pre-and post-onset phases. An approximate inverse relationship exists between the large-scale apparent vorticity sources (Z) at 850 and 200mb over the Southern Hemisphere monsoon region. For example, near Cape, York Peninsula, large positive Z values at 850mb are contrasted with pronounced negative Z values at 200mb after the onset. IntroductionPrior to the First GARP Global Experiment (FGGE), most of the synoptic studies on the Southern Hemisphere summer monsoon focused on the local circulation features over limited areas such as Indonesia and/or northern Australia (e.g., Bryant, 1958;Berson, 1961; Falls, 1970

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Evolution of maritime continent thunderstorms under varying meteorological conditions over the Tiwi Islands

Beringer

Tapper

Keenan

2001

Intl Journal of Climatology

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The development of tropical island thunderstorms in the maritime continent were investigated over the Tiwi Islands to the north of the Australian continent. A satellite cloud climatology was developed to examine these island thunderstorms, locally known as Hectors. During the pre-monsoon period of 1990 and 1991 Hectors were observed on 70% of days. These Hectors were observed to occur under two distinct environmental flow regimes. Under easterly flow, development occurred on the western end of the island and conversely under westerly flow, development occurred to the east. Hectors were also observed to have three distinct modes of development (Hector, suppressed and late developing) and one mode of non-development (non-Hector). Satellite cloud climatologies were developed and mean atmospheric characteristics were determined for each of these development modes. Hectors developed under conditions of moderate convective available potential energy, moderate shear and high moisture availability. Sub-cloud layer winds were also thought to contribute to the structure of the storm. Non-Hector and suppressed Hector days usually occurred after a previous convective disturbance such as a monsoon low or squall line and had typically low convective available potential energy and high values of convective inhibition. Conditions for late developing Hectors appeared to be conducive for thunderstorm development with high convective available potential energy and low values of convective inhibition. However, early initiation was suppressed by high shear conditions. Development in the late developing mode could be more intense than in other modes.

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Circulation and Energy Balance in a Tropical Monsoon

Cited by 6 publications

References 8 publications

Factors contributing to the onset of the Australian summer monsoon

Factors contributing to the onset of the Australian summer monsoon

Heat, Moisture, and Vorticity Budget Before and After the Onset of the 1978-79 Southern Hemisphere Summer Monsoon1

Evolution of maritime continent thunderstorms under varying meteorological conditions over the Tiwi Islands

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