Abstract. The Nanjing University of Information Science and Technology Earth System
Model version 3 (NESM v3) has been developed, aiming to provide a numerical
modeling platform for cross-disciplinary Earth system studies, project
future Earth climate and environment changes, and conduct
subseasonal-to-seasonal prediction. While the previous model version NESM v1
simulates the internal modes of climate variability well, it has no
vegetation dynamics and suffers considerable radiative energy imbalance at
the top of the atmosphere and surface, resulting in large biases in the
global mean surface air temperature, which limits its utility to simulate
past and project future climate changes. The NESM v3 has upgraded
atmospheric and land surface model components and improved physical
parameterization and conservation of coupling variables. Here we describe
the new version's basic features and how the major improvements were made.
We demonstrate the v3 model's fidelity and suitability to address global
climate variability and change issues. The 500-year preindustrial (PI)
experiment shows negligible trends in the net heat flux at the top of
atmosphere and the Earth surface. Consistently, the simulated global mean
surface air temperature, land surface temperature, and sea surface
temperature (SST) are all in a quasi-equilibrium state. The conservation of
global water is demonstrated by the stable evolution of the global mean
precipitation, sea surface salinity (SSS), and sea water salinity. The sea
ice extents (SIEs), as a major indication of high-latitude climate, also
maintain a balanced state. The simulated spatial patterns of the energy
states, SST, precipitation, and SSS fields are realistic, but the model suffers
from a cold bias in the North Atlantic, a warm bias in the Southern Ocean,
and associated deficient Antarctic sea ice area, as well as a delicate sign
of the double ITCZ syndrome. The estimated radiative forcing of quadrupling
carbon dioxide is about 7.24 W m−2, yielding a climate sensitivity
feedback parameter of −0.98 W m−2 K−1, and the equilibrium climate
sensitivity is 3.69 K. The transient climate response from the 1 % yr−1 CO2
(1pctCO2) increase experiment is 2.16 K. The model's performance on internal
modes and responses to external forcing during the historical period will be
documented in an accompanying paper.