El Niño-Southern Oscillation (ENSO) seasonal phase-locking behaviors simulated in 36 Coupled Model Intercomparison Project Phase 6 (CMIP6) models are evaluated for the first time by comparison with 43 CMIP5 models and observations. There are much more aborted ENSO events (simulated mature phase occurring out of the winter season) in 30 CMIP6 and 33 CMIP5 models than in observations, which indicates that the reasonable ENSO seasonal phase-locking is still a challenge to state-of-the-art climate models. Furthermore, the seasonal cycle of the zonal SST gradient along the equator can explain approximately 30% and 36% of the variance in the ENSO phase locking for CMIP5 and CMIP6, respectively. Moreover, both the spatial distribution and the phase change timing of the zonal SST gradient seasonal cycle are crucial for the ENSO seasonal phase locking. Improvement of the simulating ENSO phase-locking should be realized by focusing on the seasonal cycle of the zonal SST gradient.

The land surface model of the Chinese Academy of Sciences (CAS-LSM), which includes lateral flow, water use, nitrogen discharge and river transport, soil freeze thaw front dynamics, and urban planning, was implemented into the Flexible Global Ocean-Atmosphere-Land System model grid-point version 3 (CAS-FGOALS-g3). Simulations were conducted using the land–atmosphere component setup of CAS-FGOALS-g3. The simulations showed reasonable distributions of the land surface variables when compared against observations (including reanalysis, merged data, remote sensing, etc). In terms of the new capabilities, it was shown that considering the groundwater lateral flow caused a deepening of the water table depth of around 25–50 mm in North India, central USA, and Sahel. Including the anthropogenic groundwater use also led to increased latent heat fluxes of about 20 W∙m-2 in the aforementioned three areas. Inclusion of the soil freeze thaw front (FTF) dynamics enabled seasonal-variation simulations of the freeze and thaw processes, and the FTF-derived permafrost extent was comparable to that seen in the observations. The simulations conducted using the riverine nitrogen transport and human activity schemes showed that major rivers around the globe, including western Europe, eastern China, and the Midwest of the USA experienced annual dissolved inorganic nitrogen (DIN) rates of 25–50 Gg∙N∙yr-1, which were accompanied by surface water regulation DIN losses of around 28 mg∙N∙m-2∙yr-1 and DIN retention of 200–500 mg∙N∙m-2∙yr-1. The results suggest that the model is a useful tool for studying the effects of land-surface processes on the global climate, especially those influenced by human interventions.