北太平洋副热带模态水形成区混合层热动力过程诊断分析

doi:10.11978/j.issn.1009-5470.2011.05.008

Abstract

Abstract: Diagnostics of the contributions from the surface heat forcing, vertical entrainment, Ekman advection, and geostrophic advection to the formation of the North Pacific subtropical mode water are performed using the National Centers for Environmental Prediction (NCEP) ocean data and the Comprehensive Ocean-Atmosphere Data Set ( COADS) fluxes. The results suggest that both the surface heat forcing and vertical entrainment dominate the cooling tendency of the wintertime mixed layer in all three mode water formation regions, with relative contributions of 67% and 19% in the North Pacific Subtropical Mode Water (NPSTMW) formation region, respectively; 53% and 21% in the North Pacific Central Mode Water (NPCMW) formation region, and 65% and 30% in the Eastern Subtropical Mode Water (ESMW) formation region. In addition, both the Ekman and geostrophic advection are warm advection in the ESMW formation region, while only the latter is warm advection in the other two mode water formation regions. Further analysis indicates that on interannual and decadal timescales, contributions from the surface heat forcing and geostrophic advection to the wintertime mixed layer cooling trend are 62% and 32% in the NPSTMW formation region, respectively. In the NPCMW formation region, the interannual and decadal variability derives from the combination of Ekman advection (32%), geostrophic advection (30%), and surface heat forcing (25%). By contrast, the surface heat forcing is the most prominent contributor (67%) in in ESMW formation region.

Key words: North Pacific, subtropical mode water, mixed layer, surface heat flux, ocean advection, vertical entrainment

CLC Number:

P731

PAN Ai-jun,WAN Xiao-fang,LIU Qin-yu . Diagnostics of mixed-layer thermodynamics in the formation regime of the North Pacific subtropical mode water[J].Journal of Tropical Oceanography, 2011, 30(5): 8-18.

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Diagnostics of mixed-layer thermodynamics in the formation regime of the North Pacific subtropical mode water

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