The Summer Atmospheric Circulation over the Arabian Sea

Ramage, C. S.

doi:10.1175/1520-0469(1966)023<0144:tsacot>2.0.co;2

Cited by 78 publications

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“…The common perception of the South Asian monsoon is equal to the synoptic situation during the "active monsoon". Subsidence and dry heat lows West of the Arabian Sea as explained above are also part of the "active monsoon" (Ramage, 1966;Webster et al, 1998;Gadgil, 2003). Spells of weak rainfall interrupt the "active monsoon" with a frequency of about 40 days.…”

Section: Present Day Precipitation Climatology Between the Eastern Mementioning

confidence: 99%

“…Slowing of the jet over the Western Arabian Sea causes subsidence over Pakistan, Arabia and Somalia. Any convection from the heated ground is capped by the subsiding air from above and confined to the lower troposphere (Ramage, 1966;Webster and Fasullo, 2003). The resulting shallow heat lows are generally associated with drought.…”

Section: Present Day Precipitation Climatology Between the Eastern Mementioning

confidence: 99%

“…Cyclones constantly move eastwards across West Asia. They may provide moisture during winter and spring as far west as the Karakoram and western Himalaya (Ramage, 1966;Karim and Veizer, 2002). However, only where tropospheric instability leads to ascent such cyclones may be reactivated, intensify and produce rainfall.…”

Section: The Evolution Of the South Asian Summer Monsoon And Its Effementioning

confidence: 99%

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Holocene Climate and Cultural Evolution in Late Prehistoric–Early Historic West Asia

2006

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The precipitation climatology and the underlying climate mechanisms of the eastern Mediterranean, West Asia, and the Indian subcontinent are reviewed, with emphasis on upper and middle tropospheric flow in the subtropics and its steering of precipitation. Holocene climate change of the region is summarized from proxy records. The Indian monsoon weakened during the Holocene over its northernmost region, the Ganges and Indus catchments and the western Arabian Sea. Southern regions, the Indian Peninsula, do not show a reduction, but an increase of summer monsoon rain across the Holocene. The long-term trend towards drier conditions in the eastern Mediterranean can be linked to a regionally complex monsoon evolution. Abrupt climate change events, such as the widespread droughts around 8200, 5200 and 4200 cal yr BP, are suggested to be the result of altered subtropical upper-level flow over the eastern Mediterranean and Asia.The abrupt climate change events of the Holocene radically altered precipitation, fundamental for cereal agriculture, across the expanse of late prehistoric-early historic cultures known from the archaeological record in these regions. Social adaptations to reduced agro-production, in both dry-farming and irrigation agriculture regions, are visible in the archaeological record during each abrupt climate change event in West Asia. Chronological refinement, in both the paleoclimate and archaeological records, and transfer functions for both precipitation and agro-production are needed to understand precisely the evident causal linkages.

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Section: Present Day Precipitation Climatology Between the Eastern Mementioning

confidence: 99%

Section: Present Day Precipitation Climatology Between the Eastern Mementioning

confidence: 99%

Section: The Evolution Of the South Asian Summer Monsoon And Its Effementioning

confidence: 99%

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Holocene Climate and Cultural Evolution in Late Prehistoric–Early Historic West Asia

2006

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“…If this also occurs far to the west in the presence of subsidence in the middle troposphere (Ramage, 1966), as seems likely from Pisharoty and Asnani's (1960) work, then rainfall over western India, which derives partly from this transequatorial flux, will diminish. Evaporation from the Arabian Sea is likely to diminish also, if warmer air moving southeast from Arabia is present.…”

Section: Summary and Remarksmentioning

confidence: 99%

Some aspects of break and active monsoon over southern Asia during summer

Hamilton

1977

Tellus A: Dynamic Meteorology and Oceanography

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North of 10' N, at least three synoptic phases of the summer monsoon can be identified. Two of these phases-the break and active monsoon-are extremes. Patterns of cloudiness and rainfall for these two phases differ substantially. These indicate differences in the geographic location and intensity of tropospheric energy sources.Tropospheric circuiations over the equatorial Indian Ocean during break and active monsoon also differ. A break is often accompanied by the development of a trough in the lower troposphere northeast of Gan; this appears to enhance rainfall over southeast India. Although cause and effect are difficult to separate using scanty aerological data, synoptic variation over the equatorial Indian Ocean east of 60'-65 ' E may influence rainfall over western and southern India.

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“…The intensity of the summer monsoon has been tied to the orographic effects of the Himalayan Mountains and the Tibetan Plateau, which tend to enhance the convergence of moist convection and latent heat (Ramage, 1965;Hahn and Manabe, 1975). During the winter months, the land cools relative to the ocean, allowing a broad high-pressure cell to develop over the Tibetan Plateau and, to a lesser extent, over the Arabian Peninsula.…”

Section: Introductionmentioning

confidence: 99%

A Rock-Magnetic Record of Monsoonal Dust Deposition to the Arabian Sea: Evidence for a Shift in the Mode of Deposition at 2.4 Ma

Menocal¹,

Bloemendal²,

King³

1991

Proceedings of the Ocean Drilling Program

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A detailed record of eolian deposition from the Asian monsoon has been determined from measurements of magnetic susceptibility at Sites 721 and 722 located on an elevated ridge in the western Arabian Sea. Susceptibility was measured at 5-cm intervals (1 k.y.) on whole-core sections (15,000 measurements) and these data were used to construct complete composite records extending to 3.2 Ma. The composite records at Sites 721 and 722 are virtually identical, suggesting that both are complete and without local hiatuses. Bulk X-ray diffraction analyses indicate that (eolian) quartz and dolomite abundances are strongly covariant with the susceptibility data {r = 0.83, 0.70; « = 172). An almost perfect correlation (r = 0.98; n = 94) between susceptibility and terrigenous percent (determined by sequential carbonate, opal, and organic carbon extraction) indicates that susceptibility is a rapid and sensitive tracer of terrigenous fraction variations. Furthermore, terrigenous and biogenic flux calculations indicate that the observed susceptibility variations are indeed the result of terrigenous accumulation rate variations and not dilution by variations in biogenic input.In the frequency-domain, variance is concentrated at orbital periodicities for the entire 3.2 Ma sequence; however, there is a shift in the dominant periodicity at ca. 2.4 Ma. From 3.2 to 2.4 Ma, the susceptibility data vary almost purely at 23-19 k.y. periodicities and coherency with the precessional insolation forcing is high (0.89). Strong and coherent variance at the 23-19 k.y. band is maintained after 2.4 Ma but there is a dramatic increase in variance at the 41 k.y. periodicity corresponding to orbital obliquity. The timing of this shift coincides with the initiation of Northern Hemisphere glaciation and suggests a linkage between high-and low-latitude climate processes. General circulation model experiments and paleoclimatological evidence from northeast Africa suggest that the increase in 41 k.y. power after 2.4 Ma may be reflecting periodic increases in monsoon dust source area aridity due to the coeval expansion of the Eurasian and/or North American ice sheets, which varied predominantly at this periodicity.

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The Summer Atmospheric Circulation over the Arabian Sea

Cited by 78 publications

References 0 publications

Holocene Climate and Cultural Evolution in Late Prehistoric–Early Historic West Asia

Holocene Climate and Cultural Evolution in Late Prehistoric–Early Historic West Asia

Some aspects of break and active monsoon over southern Asia during summer

A Rock-Magnetic Record of Monsoonal Dust Deposition to the Arabian Sea: Evidence for a Shift in the Mode of Deposition at 2.4 Ma

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