The NCAR CCM1's simulation of the modem arctic climate is evaluated by
comparing a five-year seasonal cycle simulation with the ECMWF global
analyses. The sea level pressure (SLP), storm tracks, vertical cross
section of height, 500-hPa height, total energy budget, and moisture b
udget are analyzed to investigate the biases in the simulated arctic c
limate. The results show that the model simulates anomalously low SLP,
too much storm activity, and anomalously strong baroclinicity to the
west of Greenland and vice versa to the east of Greenland. This bias i
s mainly attributed to the model's topographic representation of Green
land. First, the broadened Greenland topography in the model distorts
the path of cyclone waves over the North Atlantic Ocean. Second, the m
odel oversimulates the ridge over Greenland, which intensifies its blo
cking effect and steers the cyclone waves clockwise around it and henc
e produces an artificial ''circum-Greenland'' trough. These biases are
significantly alleviated when the horizontal resolution increases to
T42. Over the Arctic basin, the model simulates large amounts of low-l
evel (stratus) clouds in winter and almost no stratus in summer, which
is opposite to the observations. This bias is mainly due to the locat
ion of the simulated SLP features and the negative anomaly of storm ac
tivity, which prevent the transport of moisture into this region durin
g summer but favor this transport in winter. The moisture budget analy
sis shows that the model's net annual precipitation ([P - E]) between
70-degrees-N and the North Pole is 6.6 times larger than the observati
ons and the model transports six times more moisture into this region.
The bias in the advection term is attributed to the positive moisture
fixer scheme and the distorted flow pattern. However, the excessive m
oisture transport into the Arctic basin does not solely result from th
e advection term. The contribution by the moisture fixer is as large a
s from advection. By contrast, the semi-Lagrangian transport scheme us
ed in the CCM2 significantly improves the moisture simulation for this
region; however, globally the error is as serious as for the positive
moisture fixer scheme. Finally, because the model has such serious pr
oblems in simulating the present arctic climate, its simulations of pa
st and future climate change for this region are questionable.