Simulation of the Interface between the Indian Summer Monsoon and the East Asian Summer Monsoon: Intercomparison between MPI-ESM and ECHAM5/MPI-OM

The time-mean and interannual variability of the interface between the Indian summer monsoon and East Asian summer monsoon (IIE) was assessed using both Max-Planck-Institute Earth System Model (MPI-ESM) and ECHAM5/MPI-OM and by calculating diagnostics and skill metrics around the IIE area. Progress has been made in modeling these aspects by moving from ECHAM5/MPI-OM to MPI-ESM. MPI-ESM is more skillful than ECHAM5/MPI-OM in modeling the time-mean state and the extreme condition of the IIE. Though simulation of the interannual variability significantly deviates to some extent in both MPI-ESM and ECHAM5/MPI-OM, MPI-ESM-LR shows better skill in reflecting the relationship among sea surface temperature anomalies over the Pacific, circulation anomalies over East Asia, and IIE variability. The temperature becomes warmer under the RCP2.6 and RCP8.5 scenarios in comparison with the historical experiments, but the position of the IIE and the key physical process in relation to the IIE variability almost remains the same, suggesting that the Indian summer monsoon tends to change in phase with the East Asian summer monsoon under each RCP scenario. The relatively realistic description of the physical processes modulated by terrain in MPI-ESM may be one of the most important reasons why MPI-ESM performs better in simulating the IIE.