The Onset and Interannual Variability of the Asian Summer Monsoon in Relation to Land–Sea Thermal Contrast

Authors:
  • CLChengfeng Li
    Chengfeng Li
  • MYMichio Yanai
    Michio Yanai
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Abstract
The onset and interannual variability of the Asian summer monsoon in relation to land–sea thermal contrast and its contributing factors are studied using a 14-yr (1979–1992) dataset. The onset of the Asian summer monsoon is concurrent with the reversal of meridional temperature gradient in the upper troposphere south of the Tibetan Plateau. The reversal is the result of large temperature increases in May to June over Eurasia centered on the Plateau with no appreciable temperature change over the Indian Ocean. In spring the Tibetan Plateau is a heat source that is distinctly separate from the heat source associated with the rain belt in the equatorial Indian ocean. The Tibetan heat source is mainly contributed by sensible heat flux from the ground surface, while the oceanic heat source is due to the release of latent heat of condensation. It is the sensible heating over the Plateau region in spring that leads to the reversal of meridional temperature gradient. Despite its intensity the condensatio... Abstract The onset and interannual variability of the Asian summer monsoon in relation to land–sea thermal contrast and its contributing factors are studied using a 14-yr (1979–1992) dataset. The onset of the Asian summer monsoon is concurrent with the reversal of meridional temperature gradient in the upper troposphere south of the Tibetan Plateau. The reversal is the result of large temperature increases in May to June over Eurasia centered on the Plateau with no appreciable temperature change over the Indian Ocean. In spring the Tibetan Plateau is a heat source that is distinctly separate from the heat source associated with the rain belt in the equatorial Indian ocean. The Tibetan heat source is mainly contributed by sensible heat flux from the ground surface, while the oceanic heat source is due to the release of latent heat of condensation. It is the sensible heating over the Plateau region in spring that leads to the reversal of meridional temperature gradient. Despite its intensity the condensatio...