A Model of the Asian Summer Monsoon. Part I: The Global Scale

Hoskins, Brian J.; Rodwell, M.J.W.

doi:10.1175/1520-0469(1995)052<1329:amotas>2.0.co;2

Cited by 264 publications

(219 citation statements)

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“…[14] Among distinctive features of monsoon circulation are the band of easterly winds just south of the equator, the cross-equatorial Somali Jet, and the strong westerlies across the Arabian Sea and southern India [e.g., Hoskins and Rodwell, 1995;Rodwell and Hoskins, 1995]. Accordingly, we correlated Tibet MSE with 850 mb wind speed for early and late periods of the monsoon season ( Figure 5).…”

Section: Resultsmentioning

confidence: 99%

Signatures of Tibetan Plateau heating on Indian summer monsoon rainfall variability

Rajagopalan

Molnár

2013

JGR Atmospheres

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[1] Despite recent challenges, conventional wisdom has held that heating over the Tibetan Plateau leads to increased Indian summer monsoon rainfall via enhancement of cross-equatorial circulation aloft, and a concurrent strengthening of both the Somali Jet and westerly winds that bring moisture to southern India. We show that such heating, quantified by monthly estimates of moist static energy in the atmosphere just above the surface, correlates with summer monsoon rainfall, but only in the early (20 May to 15 June) and late (September 1 to 15 October) monsoon season. Correlations during the main monsoon season (15 June to 31 August) are small and insignificant. The positive correlations with early and late monsoon season, however, allow for heating over Tibet to modulate as much as 30% of the total rainfall. Furthermore, we demonstrate that heating over Tibet is independent of the El Niño Southern Oscillation, so that together they explain a substantial portion of variability in the early and late season rainfall, providing potential predictability. These links may also explain the wet conditions over India during early Holocene time and provide a quantitative link between a rise of Tibet and stronger Somali Jet.

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Section: Resultsmentioning

confidence: 99%

Signatures of Tibetan Plateau heating on Indian summer monsoon rainfall variability

Rajagopalan

Molnár

2013

JGR Atmospheres

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“…The intensified monsoon rainfall can reduce precipitation over the adjacent arid regions located to the west and poleward of the monsoon region. The latter results from the increased descent in the dry region through the interaction between Rossby wave and mean westerly flow (Hoskins and Rodwell 1995) and the enhanced transverse monsoon circulations driven by differential radiative heating (Webster et al 1998). Over extratropical North America, associated with a high APO index is the local weakened upward motion (figure not shown) because of both the weakened lower-level convergence and high-level divergence.…”

Section: Precipitationmentioning

confidence: 98%

Boreal summer continental monsoon rainfall and hydroclimate anomalies associated with the Asian-Pacific Oscillation

Zhao¹,

Wang

Zhou

2012

Clim Dyn

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With the twentieth century analysis data for atmospheric circulation, precipitation, Palmer drought severity index, and sea surface temperature (SST), we show that the Asian-Pacific Oscillation (APO) during boreal summer is a major mode of the earth climate variation linking to global atmospheric circulation and hydroclimate anomalies, especially the Northern Hemisphere (NH) summer land monsoon. Associated with a positive APO phase are the warm troposphere over the Eurasian land and the relatively cool troposphere over the North Pacific, the North Atlantic, and the Indian Ocean. Such an amplified land-ocean thermal contrast between the Eurasian land and its adjacent oceans signifies a stronger than normal NH summer monsoon, with the strengthened southerly or southwesterly monsoon prevailing over tropical Africa, South Asia, and East Asia. A positive APO implies an enhanced summer monsoon rainfall over all major NH land monsoon regions: West Africa, South Asia, East Asia, and Mexico. Thus, APO is a sensible measure of the NH land monsoon rainfall intensity. Meanwhile, reduced precipitation appears over the arid and semiarid regions of northern Africa, the Middle East, and West Asia, manifesting the monsoon-desert coupling. On the other hand, surrounded by the cool troposphere over the North Pacific and North Atlantic, the extratropical North America has weakened low-level continental low and upper-level ridge, hence a deficient summer rainfall. Corresponding to a high APO index, the African and South Asian monsoon regions are wet and cool, the East Asian monsoon region is wet and hot, and the extratropical North America is dry and hot. Wet and dry climates correspond to wet and dry soil conditions, respectively. The APO is also associated with significant variations of SST in the entire Pacific and the extratropical North Atlantic during boreal summer, which resembles the Interdecadal Pacific Oscillation in SST. Of note is that the Pacific SST anomalies are not present throughout the year, rather, mainly occur in late spring, peak at late summer, and are nearly absent during boreal winter. The season-dependent APO-SST relationship and the origin of the APO remain elusive.

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“…Hoskins and Rodwell (1995) discuss experiments testing mountains versus no mountains, heating versus no heating, and various 'linear' versus nonlinear integrations. They study the June-August season.…”

Section: Rossby Wavetrain From Tropical Heat Sourcementioning

confidence: 99%

Remote weather associated with South Pacific subtropical sea‐level high properties

Grotjahn

2004

Intl Journal of Climatology

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The subtropical highs in sea-level pressure (SLP) are little studied and incompletely understood. In recent years, three groups of theories, i.e. tropical divergent circulations, subtropical Rossby wavetrains, and midlatitude frontal cyclone interactions, have been proposed for remote maintenance of these highs. The latter is presented here as a remote forcing of these highs for the first time in the reviewed literature. The focus of the study is upon illuminating associations between these mechanisms and the South Pacific subtropical high in SLP (SP high). Precipitation, outgoing longwave radiation, velocity potential, and divergent winds are used as proxy markers for the remote forcing mechanisms. The tools used include composites, one-point correlations, autocorrelations, cross-correlations, and cross-spectra. Observational evidence, in monthly and daily data, is examined that appears to support each mechanism. Associations seen in monthly data are better understood in daily data at various lags. Convection over Amazonia, coordinated with suppressed convection in the western tropical Pacific, leads to enhanced SLP on the tropical side of the high. Midlatitude weather systems are the strongest influence upon the maximum SLP and the SLP on the higher latitude side of the high. The western side is associated with both middle-and lower-latitude phenomena, such as the South Pacific convergence zone. Various properties of the high have a strong period around 45 days. Associations to the Madden-Julian oscillation and El Niño-southern oscillation are explored and are strong only for the tropical side of the SP high.

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A Model of the Asian Summer Monsoon. Part I: The Global Scale

Cited by 264 publications

References 0 publications

Signatures of Tibetan Plateau heating on Indian summer monsoon rainfall variability

Signatures of Tibetan Plateau heating on Indian summer monsoon rainfall variability

Boreal summer continental monsoon rainfall and hydroclimate anomalies associated with the Asian-Pacific Oscillation

Remote weather associated with South Pacific subtropical sea‐level high properties

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