[A-AS08] Multiple scale structure and their interactions in Asian monsoon system

[AAS08-09] Isolated impact of land-surface condition over the Tibetan Plateau in late spring on the Asian monsoon circulation in early summer from a large-ensemble dataset

*高橋 洋¹、Sugimoto Shiori²、佐藤 友徳³ (1.東京都立大学大学院 地理環境学域、2.海洋研究開発機構、3.北海道大学)

This study isolates the impact of land-surface conditions, like surface air temperature (SAT), over the Eurasian Continent, consequently the Tibetan Plateau, on the Asian monsoon circulations from a large-ensemble AGCM experiment. The memory effects of land-surface conditions can persist only for one month. Thus, the memory effects of snow cover in the northern winter may not persist to May in the simulated dataset. However, the warmer SAT over the Tibetan Plateau in May can sometimes enhance the monsoon circulation in June. The physical mechanism to enhance the Asian summer monsoon circulation can be simple. The warmed Tibetan Plateau enhances the north-south SAT gradient, strengthening the monsoon circulation. In the upper troposphere, anti-cyclonic circulation anomalies are simulated in May when the monsoon circulation is strong in June. In the presentation, we will also discuss how the land-surface impact varies interannually.