What are the sources of mechanical damping in Matsuno-Gill-type models?
Lin, JL; Mapes, BE; Han, WQ; lin.789@osu.edu
2008
发表期刊JOURNAL OF CLIMATE
ISSN0894-8755
卷号21期号:2页码:165-179
摘要The Matsuno-Gill model has been widely used to study the tropical large-scale circulations and atmosphere-ocean interactions. However, a common critique of this model is that it requires a strong equivalent linear mechanical damping to get realistic wind response and it is unclear what could provide such a strong damping above the boundary layer. This study evaluates the sources and strength of equivalent linear mechanical damping in the Walker circulation by calculating the zonal momentum budget using 15 yr (1979-93) of daily global reanalysis data. Two different reanalyses [NCEP-NCAR and 15-yr ECMWF Re-Analysis (ERA-15)] give qualitatively similar results for all major terms, including the budget residual, whose structure is consistent with its interpretation as eddy momentum flux convergence by convective momentum transport (CMT). The Walker circulation is characterized by two distinct regions: a deep convection region over the Indo-Pacific warm pool and a shallow convection region over the eastern Pacific cold tongue. These two regions are separated by a strong upper-tropospheric ridge and a strong lower-tropospheric trough in the central Pacific. The resultant pressure gradient forces on both sides require strong (approximately 5-10 days) damping to balance them because Coriolis force near the equator is too small to provide the balance. In the deep convection region, the damping is provided by CMT and advection together in both the upper and lower troposphere. In the shallow convection region, on the other hand, the damping is provided mainly by advection in the upper troposphere and by CMT in the lower troposphere. In other words, the upperlevel tropical easterly jet and the low-level trade wind are both braked by CMT. These results support the use of strong damping in the Matsuno-Gill-type models but suggest that the damping rate is spatially inhomogeneous and the CMT-related damping increases with the strength of convection. Implications for GCM's simulation of tropical mean climate are discussed.
部门归属[Lin, Jia-Lin] NOAA ESRL CIRES Climate Diag Ctr, Boulder, CO USA; [Mapes, Brian E.] Univ Miami, RSMAS, Miami, FL 33152 USA; [Han, Weiqing] Univ Colorado, DAOS, Boulder, CO 80309 USA
学科领域Meteorology & Atmospheric Sciences
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收录类别sci
文献类型期刊论文
条目标识符http://ir.scsio.ac.cn/handle/344004/8439
专题海洋科技动态信息-印太暖池系统研究
通讯作者lin.789@osu.edu
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Lin, JL,Mapes, BE,Han, WQ,et al. What are the sources of mechanical damping in Matsuno-Gill-type models?[J]. JOURNAL OF CLIMATE,2008,21(2):165-179.
APA Lin, JL,Mapes, BE,Han, WQ,&lin.789@osu.edu.(2008).What are the sources of mechanical damping in Matsuno-Gill-type models?.JOURNAL OF CLIMATE,21(2),165-179.
MLA Lin, JL,et al."What are the sources of mechanical damping in Matsuno-Gill-type models?".JOURNAL OF CLIMATE 21.2(2008):165-179.
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