An analytical diagnostic model of the Antarctic Circumpolar Current

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红外和水色遥感资料同化研究设想

本文指出卫星红外及水色遥感资料同化研究，需要建立在中尺度分辨力大洋热力动力准地转运动与上混合层运动耦合数值模式的基础上，利用该耦合模式可进一步研究中尺度温度结构及相应运动场的形成、演化和统计特征，使该模式具有温度场预报应用的价值，并得到诸如叶绿素、悬浮泥沙等水色要素在空间场的分布，且使温度场和水色要素场与动力环境相协调。该项研究对卫星海洋学发展有深刻的理论意义和潜在应用前景。     

Can Langmuir Circulations Solve the Problem of Insufficient Upper-Ocean Mixing?

Insufficient vertical mixing in the upper ocean during summer is a common problem of oceanic circulation and climate models. The turbulence associated with non-breaking waves is widely believed to effectively solve this problem. In many studies, non-breaking surface wave processes are attributed to the effects of Langmuir circulations(LCs). In the present work, the influences of LCs on the upper-ocean thermal structure are examined by using one-and three-dimensional ocean circulation, as well as climate, models. The results indicated that the effect of vertical mixing enhanced by LCs is limited to the upper ocean. The models evaluated, including those considering LC effects alone and the combined effects of LCs and wave breaking, failed to produce a reasonable summertime thermocline, resulting in a large cold bias in the subsurface layer. Therefore, while they can slightly reduce the biases of mixed layer depths and sea surface temperatures in models, LCs are insufficient to solve the problem of insufficient vertical mixing. Moreover, restriction of non-breaking surface wave-induced processes in LCs may be questionable.     

Simulation of double cold cores of the 35°N section in the YellowSea with a wave-tide-circulation coupled model

Based on the MASNUM wave-tide-circulation coupled numerical model, the temperature structure along 35°N in the Yellow Sea was simulated and compared with the observations. One of the notable features of the temperature structure along 35°N section is the double cold cores phenomena during spring and summer. The double cold cores refer to the two cold water centers located near 122°E and 125°E from the depth of 30m to bottom. The formation, maintenance and disappearance of the double cold cores are discussed. At least two reasons make the temperature in the center (near 123°E) of the section higher than that near the west and east shores in winter. One reason is that the water there is deeper than the west and east sides so its heat content is higher. The other is invasion of the warm water brought by the Yellow Sea Warm Current (YSWC) during winter. This temperature pattern of the lower layer (from 30m to bottom) is maintained through spring and summer when the upper layer (0 to 30m) is heated and s     

Simulation and analysis on seasonal variability of average salinityin the Yellow Sea

The CTD (conductivity, temperature and depth) data collected by six China-Korea joint cruises during 1996-1998 and the climatological data suggest that the seasonal variability of average salinity in the Yellow Sea (Sa) presents a general sinusoid pattern. To study the mechanism of the variability, annual cycles of Sa were simulated and a theoretical analysis based on the governing equations was reported.Three main factors are responsible for the variability: the Yellow Sea Warm Current (YSWC), the Changji-ang (Yangtze) River diluted water (YRDW) and the evaporation minus precipitation (E-P). From December to the next May, the variability of Sa is mainly controlled by the salt transportation of the YSWC. But in early July, the YSWC is overtaken and replaced by the YRDW which then becomes the most important controller in summer. From late September to November, the E-P gradually took the lead. The mass exchange north of the 37癗 line is not significant.     

四川盆地东北部一次突发性暴雨事件的影响系统分析

利用ERA5再分析资料、新一代雷达拼图资料,探究了2017年5月初四川盆地东北部一次突发性暴雨事件的影响系统及动力影响因子。结果表明:此次暴雨事件的主要影响系统有中纬500 hPa东移低槽、西伸的西太平洋副热带高压、对流层中低层的西南低空急流以及低层切变线。大尺度的低空急流与中小尺度的山区低空急流的叠加使四川盆地东北部形成正涡度柱和低层强辐合柱的动力耦合,低空急流最大风速出口辐合上升区与地形的辐合抬升作用叠加形成盆地东北部强烈的垂直上升运动,成为山地暴雨突发的动力触发条件,因低空急流建立的位势不稳定层结构成暴雨的热力条件。冷空气自低层逐渐向高层侵入是暴雨第二阶段增幅的主要原因。盆地东北部地形是本次暴雨的另一个增幅因子,其对暴雨过程中垂直上升运动有加强作用,秦巴山脉迎风坡的抬升作用对暴雨第一阶段的降水量贡献较大,青藏高原东麓背风坡的辐合效应对第二阶段降水量贡献较大。此外,盆地东北部山地对东移的中尺度对流系统有阻挡作用,使其停滞并旺盛发展。     

The Equilibrium Range of Wind Wave Spectra： an Explanation Based on White Noise

Laboratory experiments and field observations show that the equilibrium range of wind wave spectra presents a – 4 power law when it is scaled properly. This feature has been attributed to energy balance in spectral space by many researchers. In this paper we point out that white noise on an oscillation system can also lead to a similar inverse power law in the corresponding displacement spectrum, implying that the – 4 power law for the equilibrium range of wind wave spectra may probably only reflect the randomicity of the wind waves rather than any other dynamical processes in physical space. This explanation may shed light on the mechanism of other physical processes with spectra also showing an inverse power law, such as isotropic turbulence, internal waves, etc.     

Wave-induced mixing in the Yellow Sea

Vertical wave-induced mixing parameter Bv expressed in wave number spectrum was estimated in the Yellow Sea. The spatial distributions of By averaged over upper 20 m in 4 seasons were analyzed. It is the strongest in winter because of winter monsoon, and the weakest in spring. Since in summer it plays an important role for circulation of upper layers, its vertical structure was also discussed. Two simulations with and without wave-induced mixing in this season were performed to evaluate its effect on temperature distribution. Numerical results indicate that wave-induced mixing could increase the mixed layer thickness greatly.     

Parallelization of a coupled wave-circulation model and its application

Using the technique of Message Passing Interface, a parallelized version of a coupled wave-circulation model was set up. The tested model is a regional one for simulating the seas off China, which is comprised of 450,625 elements and 30 vertical sigma layers. The implementation efficiency was evaluated on two kinds of computers, the HP Integrity Superdome and SGI Altix 4700 multiprocessor. The numerical results show that the low-communication high-extra-computation scheme (LCHC) produces higher efficiency than the high-communication no-extra-computation scheme (HCNC) while the number of processors exceeds 24 for HP Integrity Superdome and eight for SGI Altix 4700, respectively. The experiments with both LCHC and HCNC scheme show super-linear speed-up when the number of processors is small. The model with the LCHC scheme is preferred as it achieves parallel efficiency in excess of 90% on the HP machines for all experiments with the number of processors no more than 100, while the efficiency decreases rapidly with the HCNC scheme after the number of processors increases to more than 24. Numerical results suggest that the parallelization of this coupled wave-circulation model is efficient and portable to a variety of parallel architectures.