Monsoon

About: Monsoon is a research topic. Over the lifetime, 16087 publications have been published within this topic receiving 599888 citations.

Thermal Controls on the Asian Summer Monsoon

Abstract: The Asian summer monsoon affects more than sixty percent of the world's population; understanding its controlling factors is becoming increasingly important due to the expanding human influence on the environment and climate and the need to adapt to global climate change. Various mechanisms have been suggested; however, an overarching paradigm delineating the dominant factors for its generation and strength remains debated. Here we use observation data and numerical experiments to demonstrates that the Asian summer monsoon systems are controlled mainly by thermal forcing whereas large-scale orographically mechanical forcing is not essential: the South Asian monsoon south of 20°N by land–sea thermal contrast, its northern part by the thermal forcing of the Iranian Plateau and the East Asian monsoon and the eastern part of the South Asian monsoon by the thermal forcing of the Tibetan Plateau.

Physical Oceanography of the Indian Ocean

Abstract: During the preparation of the Atlas on the physical oceanography of the Indian Ocean (WYRTKI, 1971) a comprehensive analysis of its oceanographic conditions had to be undertaken to construct meaningful maps, sections and diagrams, and to interpret the structure and circulation of this ocean, which is in so many ways different from the other oceans. On a large scale 3 distinct circulation systems can be delineated. These are: I. the seasonally changing monsoon gyre II. the south hemispheric subtropical anticyclonic gyre III. the Antarctic waters with the Circumpolar Current

Oscillations of a Monsoon System. Part I. Observational Aspects

Abstract: In this paper the elements of a monsoon system are defined, and its oscillations are determined from spectral analysis of long observational records. The elements of the monsoon system include pressure of the monsoon trough, pressure of the Mascarene high, cross-equatorial low-level jet, Tibetan high, tropical easterly jet, monsoon cloud cover, monsoon rainfall, dry static stability of the lower troposphere, and moist static stability of the lower troposphere. The summer monsoon months over India during normal monsoon rainfall years are considered as guidelines in the selection of data for the period of this study. The salient result of this study is that there seems to exist a quasi-biweekly oscillation in almost all of the elements of the monsoon system. For some of these elements, such as the surface pressure field, monsoon rainfall, low-level cross-equatorial jet and monsoon cloudiness, the amplitude of this oscillation in quasi-biweekly range is very pronounced. For the spectral representati...

Atmospheric water vapor transport associated with typical anomalous summer rainfall patterns in China

Abstract: [1] This paper attempts to reveal the atmospheric water vapor transports associated with typical anomalous summer rainfall patterns in China. The results show that origins of water vapor supply related to anomalous rainfall patterns are different from those related to the normal monsoon rainfall. Anomalous pattern 1, with a heavier rainbelt along the middle and lower reaches of the Yangtze River valley, follows from a convergence of the tropical southwest water vapor transport with the midlatitude northeast water vapor transport; the tropical water vapor transport comes directly from the Bay of Bengal and the South China Sea but originally from the Philippine Sea. The anomalous water vapor transport is associated with a southwestward extension of the western Pacific subtropical high and a southward shift of the upper East Asian jet stream. Anomalous pattern 2, with a main rainbelt along the Huaihe River valley, is supported by the convergence of the subtropical southwest water vapor with the midlatitude water vapor transport. The subtropical branch comes directly from the South China Sea but originally from the East China Sea and the adjacent subtropical Pacific to the further east along 20–25N. The background large-scale circulation change includes a northwestward extension of the western Pacific subtropical high and an eastward shift of the upper jet stream. Although the cross-equator flows including the Somali jet supply abundant water vapor for the normal condition of June, July, and August rainfall over China, the tropical water vapor transports related to typical anomalous rainfall anomalies originate from the tropical western Pacific Ocean. The northward transport of anomalous warm water vapor occurs mainly in the lower troposphere, while the transport of midlatitude cold water vapor occurs briefly in the upper troposphere.

Fundamental challenge in simulation and prediction of summer monsoon rainfall

Abstract: [1] The scientific basis for two-tier climate prediction lies in the predictability determined by the ocean and land surface conditions. Here we show that the state-of-the-art atmospheric general circulation models (AGCMs), when forced by observed sea surface temperature (SST), are unable to simulate properly Asian-Pacific summer monsoon rainfall. All models yield positive SST-rainfall correlations in the summer monsoon that are at odds with observations. The observed lag correlations between SST and rainfall suggest that treating monsoon as a slave possibly results in the models' failure. We demonstrate that an AGCM, coupled with an ocean model, simulates realistic SST-rainfall relationships; however, the same AGCM fails when forced by the same SSTs that are generated in its coupled run, suggesting that the coupled ocean-atmosphere processes are crucial in the monsoon regions where atmospheric feedback on SST is critical. The present finding calls for reshaping of current strategies for monsoon seasonal prediction. The notion that climate can be modeled and predicted by prescribing the lower boundary conditions is inadequate for validating models and predicting summer monsoon rainfall.