Coupling of the land surface model CAS-LSM with the climate system model
CAS-FGOALS-g3
Abstract
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.