Representation of Rossby wave propagation and its effect on the teleconnection between the Indian summer monsoon and extratropical rainfall in the Met Office Unified Model

Compared with Global Atmosphere 6 (GA6) of the UK Met Office Unified Model (UM), dry bias over Indian monsoon region in 7 (GA7) is significantly reduced. However, physical processes controlling how this reduced India influences rainfall teleconnections extratropics remain unclear. Thus, study, we use Rossby wave tracing a horizontally nonuniform background flow to investigate improved simulation GA7 compared GA6 affects extratropical teleconnections. We find that rays emanating from upper troposphere first propagate westward, then divide into Northern Hemisphere (NH) subtropical westerlies Asia and Southern (SH) westerlies. The ray trajectories years strong summer (ISMR) are closer observations than those GA6. also tropospheric meridional winds South Asian western Tibetan Plateau much better simulated owning improvement ISMR High (SAH), which leads more realistic GA7. circulation modulate vertical motion moisture transport, hence affect anomalies NH SH. This paper provides new insights for assessment tropical–extratropical models.