Sensitivities of the Asian Summer Monsoon Simulations to Physical Parameters for the Perturbed Parameter Ensemble of HadGEM3-GC3.05

The simulation skill of the perturbed parameter ensemble (PPE) of HadGEM3-GC3.05 on the mean climate pattern of the Asian summer monsoon (ASM) is evaluated in this study. The sensitivities of the model bias to the perturbed parameters are investigated based on metrics. The results show that the PPE mean (PPE-20M) could effectively capture the general ASM precipitation and wind patterns, with a correlation coefficient of 0.78. PPE-20M mainly shows positive precipitation biases over the tropical western Pacific, southern slope of the Tibetan Plateau, Indochina Peninsula, and South China and negative precipitation biases over the Indian continent and Bay of Bengal. The magnitude of the precipitation biases is more sensitive than its pattern to the variation of the perturbed parameters. Four parameters (ent_fac_dp, qlmin, ps_cloud-ph, and psm) are found to be crucial for simulating the ASM precipitation intensity, and their combined effects are related to the simulated precipitation biases.