Studies and simulations of global land precipitation and summer hemispheric precipitation have received much scientific and societal attention due to the impacts on economic development. Therefore, it is necessary to evaluate and improve the simulation capability of precipitation for models.

Recently, several modeling centers have released their Coupled Model Intercomparison Project Phase 6 (CMIP6) datasets.

Researchers from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS) developed the Global Monsoons Model Intercomparison Project (GMMIP) and conducted historical experiments by the Flexible Global Ocean-Atmosphere-Land System (FGOALS) climate system model. The simulation performance for global precipitation and summer hemispheric precipitation were assessed in a recent study published in Atmospheric and Oceanic Science Letters (AOSL).

"Previous studies have shown that the leading mode of global precipitation is ENSO-related rainfall with interannual variability, while the long-term trend is related to increasing temperatures. Therefore, the fidelity of different timescales should be considered," said Dr. HE Bian from IAP, the lead author of the study.

For FGOALS-f3-L, the GMMIP simulation significantly exceeded the historical experiment on different timescales. Based on the difference of experimental design and the influence of sea surface temperature anomalies (SSTAs) on interannual precipitation, the researchers explored the possible cause of the simulation discrepancy.

Rainfall in Xiamen on Aug 21, 2018 (Image by HE Bian)

According to this study, the simulation performance of sea surface temperature (SST) forcing affected the simulation performance for global precipitation significantly, especially the tropical Pacific SSTA. In addition, different regions responded differently to the Nino3.4 region SSTA and the ENSO effects were concentrated at low- to mid-latitudes.

"Realistic simulation of the SST field is necessary for CAS FGOALS-f3-L to capture the temporal characteristics of global and hemispheric land precipitation," said Dr. HE.