In this study, the impact of soil freezing–thawing processes on August rainfall in southern China (SC) during 1979–2008 and related physical mechanisms are investigated using the Grid-Point Atmospheric Model version 2.0 (GAMIL2.0). This model with considering the supercooled water in soil freezing-thawing scheme reproduces the climatology and trends of August precipitation in the SC region. Moisture-budget analysis is employed to quantity the contributions of different factors to the change of precipitation in SC. The results indicate that evaporation contributes significantly to the climatologically August rainfall in SC. The dynamic component of vertical moisture advection, which is related to changes in atmospheric circulation, plays an important role in August precipitation trends. The possible physical mechanism is that the GAMIL2.0 considering the supercooled water simulated much higher soil/air temperature on August especially in the north of 40°N, weakened the meridional thermal contrast, decreased the 200hpa zonal winds, strengthened 850hpa northerly wind, which is more benificial to the convergence in SC and lead to the precipitation increased. This study provides a new interpretation of the ‘southern flooding’ during 1979–2008 from the point of frozen soil changing.

The simplified anthropogenic aerosol optical properties and an associated Twomey effect provided by CMIP6 (i.e., MACv2-SP) were used in the Grid-point Atmospheric Model of IAP LASG (GAMIL). With the benefit of MACv2-SP, instantaneous radiative forcing (RF) from aerosol-radiation interactions (RFari) and aerosol-cloud interactions (RFaci) can be calculated by double radiation calls in one present-day (PD) simulation. The RFaci determined by this straightforward method is the exact Twomey effect, which previously was impossible to separate from its subsequent rapid adjustments using the default GAMIL model with physically based aerosol-cloud interactions. The RFaci is very robust, with a global average of −0.10 W m. The RFari can be calculated by different methods. The all-sky RFari with and without natural aerosol influence (i.e., different methods) is estimated at −0.21 and −0.33 W m, respectively. This suggests that the natural aerosol burden might substantially impact the estimate of RFari. Furthermore, the RFari determined by the difference between two simulations is more sensitive to model internal year-to-year variability compared with the RFari determined from one PD simulation. The RFaci efficiency usually enhances with increasing cloud cover, whereas the RFari efficiency becomes weaker under cloudy conditions. As a result, the seasonal variability of the global average RFaci is stronger than that of RFari. From 1975 to 2000, both RFari and RFaci show a clear response to the spatial changes in anthropogenic aerosols, and the global average RF (RFari + RFaci) is enhanced by ~6%, even with a slight decrease in the global average anthropogenic aerosols.

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.

Equilibrium climate sensitivity (ECS) and its related feedbacks are important metrics used to measure the global mean surface temperature change in future climate projections. This paper uses the radiative kernel approach and a simplified cloud feedback calculation (comparing three different cloud feedback methods) to analyze the differences in the ECS, as well as the feedbacks contributing to it, between two versions of the Flexible Global Ocean-Atmosphere-Land System model (i.e., FGOALS-g2 and FGOALS-g3). The results show that the ECS of FGOALS-g3 is smaller than that of FGOALS-g2 (2.8 K versus 3.3 K). The main feedbacks contributing to the ECS change in FGOALS-g3 are the weaker surface albedo feedback and stronger negative shortwave cloud feedback. The reduced surface albedo feedback in FGOALS-g3 is associated mainly with its mean base state, which has a lower surface air temperature and larger sea ice area compared with FGOALS-g2. The enhanced negative shortwave cloud feedback in FGOALS-g3 is caused mainly by the larger low-cloud area fraction and liquid water path. Furthermore, the ECS change can be traced back to the different cloud parameterization scheme, parameter tuning, ocean grid, and external forcings used in FGOALS-g3, as these all affect the mean climate state of the model.