4.1 Surface air temperature and precipitation
The ensemble mean climatological annual cycle of the surface air
temperature (Tair) and precipitation (P) for nine
representative high-latitude, midlatitude, and tropical regions for
CAS-FGOALS-g3, and the observational estimates for both variables, are
shown in Fig. 2 and Fig. 3, respectively. For the G3 simulations of the
temperature, the overall results showed that the annual cycle of the G3
simulations in the nine regions mimicked the observations. Among the
comparisons, the simulated temperature seasonal cycle data were at
high-latitude and mid-latitude regions were closer to the observations
than those of the tropical regions, where the Amazon region depicted a
high temperature bias in JFM (January to March) and SON (September to
November), the Sahel region depicted a lower temperature bias in MAM
(March to May) and SON, and the Indian region depicted a systematically
higher seasonal cycle (Fig. 2).
Inspection of the regionally averaged seasonal cycles of precipitation
are shown in Fig. 3. Unlike that of the temperature, comparison of the
regionally averaged seasonal cycles of precipitation with the
observations do not show obvious trends at specific latitudes.
Systematic overestimations of precipitation appeared in Alaska and the
Amazon, and the seasonal cycle was too low and did not follow the phase
of the observations in central Canada. For places like the eastern USA
and Europe, the seasonal cycle was out of phase with the observations.
For Sahel, on the other hand, an earlier peak of the cycle appeared in
May, rather than in August in the observations. Overall, the seasonal
cycle of precipitation depicted poorer results than that of the
temperature seasonal cycle, and this bias of the seasonal cycle did not
show obvious features in terms of latitude.