A comparative study on Omega equation-based vertical velocity diagnosis for the South China Sea
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摘要: 本文基于OFES(Ocean general circulation model For the Earth Simulator)模式0.1° × 0.1°高分辨率温盐和三维流场数据,分析Omega方程在南海垂向流速诊断中的适用性和南海垂向流速的时空变化特征。结果表明,Omega方程诊断垂向流速wOmega与OFES模式垂向流速wOFEES在南海海盆大部分区域量级相当,约为 O (10−5 m/s),南海北部陆架区则小一个量级。wOmega和wOFEES的空间相关系数rs在台湾西南部(R1区)和越南以东(R2区)较大,在菲律宾西(R3区)、南海南部(R4区)以及海南岛东北部(R5区)较小。季节变化上,R1、R2和R4区rs冬季大、夏季小,R3和R5区rs无明显季节特征。R1和R2区是Omega方程的适用区,其wOmega与wOFEES的时间相关系数rt较大。各区域中形变项(
$ {S}_{{\mathrm{DEF}}} $ )的贡献率均超过50%,整体大于平流项($ {S}_{{\mathrm{ADV}}} $ ),并呈现出“上层$ {S}_{{\mathrm{ADV}}} $ 主导,下层$ {S}_{{\mathrm{DEF}}} $ 增强”的共同垂向结构,其临界深度在20~70 m之间。对比eSQG(effective Surface Quasi-Geostrophy)诊断垂向流速结果,Omega方程明显更适用于南海垂向流速的诊断。Abstract: Based on 0.1° × 0.1° high-resolution temperature, salinity, and three-dimensional velocity data from the Ocean general circulation model For the Earth Simulator (OFES), this study analyzes the applicability of the Omega equation for diagnosing vertical velocity in the South China Sea (SCS) and the spatiotemporal variation characteristics of vertical velocity in the SCS. The results show that the vertical velocity diagnosed by the Omega equation (wOmega) and the OFES model vertical velocity (wOFES) are of comparable magnitude in most areas of the SCS basin, approximately O(10−5 m/s), while wOmega is one order of magnitude smaller than wOFES on the northern continental shelf of the SCS. The spatial correlation coefficient (rs) between wOmega and wOFES is larger in the region southwestern of Taiwan (R1) and east of Vietnam (R2), and smaller in the western Philippines (R3), the southern SCS (R4), and the northeastern region of Hainan Island (R5). In terms of seasonal variation, rs is larger in winter and smaller in summer in regions R1, R2, and R4, while regions R3 and R5 show no significant seasonal characteristics in rs. Regions R1 and R2 are applicable areas for the Omega equation, where the temporal correlation coefficient rt between wOmega and wOFES is larger. In all regions, the contribution of the deformation term ($ {S}_{{\mathrm{DEF}}} $ ) exceeds 50%, generally greater than the contribution of the advection term ($ {S}_{{\mathrm{ADV}}} $ ), and they exhibit a common vertical structure of “$ {S}_{{\mathrm{ADV}}} $ dominance in the upper layer and$ {S}_{{\mathrm{DEF}}} $ enhancement in the lower layer”, with the critical depth ranging from 20−70 m. Comparing the results of vertical velocity diagnosed by effective Surface Quasi-Geostrophy (eSQG) and the Omega equation, the Omega equation is significantly better adapted for diagnosing vertical velocity in the SCS.-
Key words:
- South China Sea /
- vertical velocity /
- Omega equation /
- OFES /
- spatio-temporal variation /
- eSQG
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表 1 全年、夏季和冬季R1~R5区wOmega和wOFES的空间相关系数rs
Tab. 1 Spatial correlation rs of wOmega and wOFES in the R1 to R5 regions in whole year, summer and winter
全年 夏季 冬季 R1 (100 m) 0.45(p < 0.01) 0.52(p < 0.01) 0.64(p < 0.01) R2 (100 m) 0.73(p < 0.01) 0.70(p < 0.01) 0.77(p < 0.01) R3 (100 m) 0.61(p < 0.01) 0.51(p < 0.01) 0.55(p < 0.01) R4 (100 m) 0.66(p < 0.01) 0.20(p < 0.01) 0.60(p < 0.01) R5 (50 m) 0.15(P = 0.02) 0.41(p < 0.01) 0.09(P = 0.20) 表 2 全年、夏季和冬季R1~R5区weSQG和wOFES的空间相关系数rs
Tab. 2 Spatial correlation rs of weSQG and wOFES in the R1 to R5 regions in whole year, summer and winter
全年 夏季 冬季 R1 (100 m) 0.30(p < 0.01) 0.32(p < 0.01) 0.04(p = 0.15) R2 (100 m) 0.41(p < 0.01) 0.49(p < 0.01) 0.35(p < 0.01) R3 (100 m) 0.18(p < 0.01) 0.14(p < 0.01) 0.42(p < 0.01) R4 (100 m) 0.64(p < 0.01) 0.69(p < 0.01) 0.51(p < 0.01) R5 (50 m) 0.14(p < 0.01) 0.27(p < 0.01) 0.07(p = 0.16) 表 3 R1~R5区wOmega(weSQG)和wOFES的时间相关系数rt超过0.4的比例
Tab. 3 The proportion of regions R1~R5 where the temporal correlation coefficient (rt) between wOmega (weSQG) and wOFES exceeds 0.4
wOmega和wOFES的rtOmega>0.4 weSQG和wOFES的rteSQG>0.4 R1 (100 m) 81% 73% R2 (100 m) 87% 55% R3 (100 m) 2% 0 R4 (100 m) 33% 10% R5 (50 m) 9% 7% -
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