NCEP/NCAR reanalysis data and the spectral atmospheric general circulation Model (AGCM)
of IAP/LASG (SAMIL) are employed to investigate the transport and balance of atmospheric angular
momentum (AAM). It is demonstrated that SAMIL depicts the general features of the AAM transport
and balance reasonably well. The AAM sources are in the tropics and sinks are in the mid-latitudes.
The strongest meridional transport occurs in the upper troposphere. The atmosphere gains westerly
momentum and transports it upward in the areas of surface easterlies, and downward into the areas
of surface westerlies. Consequently, AAM balance is maintained. Systematic biases of the model
compared to the reanalysis and observations are revealed. Possible mechanisms for these biases are
investigated. In SAMIL, the friction torque in the tropics is stronger compared to the observations,
which is probably due to the excessive precipitation along the Inter-tropical convergence zone (ITCZ)
in the model, since the simulated Hadley circulation is much stronger than observed. In the winter
half of the year, the transport center is in the lower troposphere in the SAMIL model, but it is in
the upper troposphere in the reanalysis and observations. These discrepancies also suggest that
simulations of convection and tropical precipitation need to be improved and that higher resolution
is necessary for a quantitative simulation of AAM transport and balance. Results also demonstrate
that the analysis of the transport and balance of atmospheric angular momentum is a powerful tool
in diagnosing climate models for potential improvement. 相似文献