The CSSP MESETA is a research project focuses on the role of Tibetan Plateau (TP) in shaping the climate of Asia. Motivated by the recent debate on the relative importance of elevated heating from TP versus orographic blocking provided by the Himalayas in maintaining the South Asian summer monsoon (SASM), MESETA work package A aims to further investigate TP’s orographic forcing on the dynamic and thermodynamic structures of regional and downstream climate.
Using the UK Met Office HadGEM3 model in its atmosphere only configuration, various experiments with idealised orography were performed to assess the orographic forcing exerted by the TP, Himalayas (HM) and Iranian Plateau (IP). Our results confirm that elevated heating from the TP is indeed not required to maintain the SASM while the HM and IP are both important in sheltering the Indian landmass from the cooler extratropical airmass. Meanwhile, the East Asian summer monsoon weakens in all simulations that removed the TP. Whether this is due to the lack of elevated heating or orographic blocking will be the focus of future investigation. This work contributes to the goals of the Global Monsoon Model Intercomparison Project (GMMIP), an endorsed component of CMIP6.