A possible generation mechanism of the strong current over the northwestern shelf of the South China Sea

Continuous observation in late April 2005 on the northwestern shelf of the South China Sea reveals vigorous strong currents, the maximum velocity of which exceeds 3.8 m/s. The strong currents occurred around spring tide period, when the internal tide waves were also expected to be vigorous. Analysis shows that the major peaks of the current power spectrum are in low frequency band. Using a numerical method applied to the actual ocean stratification, we find that the amplitude profiles of the strong current are similar to that of the currents induced by some low-mode internal waves (at diurnal or semi-diurnal frequency). It indicates that the temporal and spatial features of strong currents were possibly induced by low frequency internal waves.     

浪致混合对亚热带冬季海洋混合强度的影响

上层海洋在全球气候系统中起着至关重要的作用。对上层海洋层结及混合的模拟偏差一直是海洋和气候数值模式发展中悬而未决的问题。本文首先评估了CMIP5中45个模式对上层海洋层结模拟的偏差,确认了冬季亚热带地区海洋模式垂向混合偏强。随后,基于自然资源部第一海洋研究所地球系统模式(FIO-ESM v1.0),分别开展了1986−2005年期间包含和关闭海浪垂向混合情况下的数值实验,分析浪致混合对亚热带冬季海洋混合强度模拟的影响及机制。发现浪致混合使得气候模式中亚热带海域冬季的海洋层结增强,增强的层结使上层海洋更加稳定。首次揭示了增加浪致混合反而降低了海洋总体的垂向混合率：浪致混合使北半球冬季亚热带海域混合率从无浪实验的227 cm²/s降低到有浪实验的178 cm²/s,降低了21.6%;南半球冬季亚热带海域混合率从无浪实验的189 cm²/s降低到有浪实验的165 cm²/s,降低了12.7%。进一步分析发现,浪致混合主要是通过增加冬季亚热带海域上层海洋的热含量从而强化了海洋的层结,最终改善了气候模式对上层海洋混合的模拟。     

Noise reduction of acoustic Doppler velocimeter data based on Kalman filtering and autoregressive moving average models

Oceanic turbulence measurements made by an acoustic Doppler velocimeter(ADV) suffer from noise that potentially affects the estimates of turbulence statistics. This study examines the abilities of Kalman filtering and autoregressive moving average models to eliminate noise in ADV velocity datasets of laboratory experiments and offshore observations. Results show that the two methods have similar performance in ADV de-noising, and both effectively reduce noise in ADV velocities, even in cases of ...     

惠州高潭一次特大致洪暴雨过程分析

2018年8月30-31日广东出现一次超历史记录的极端强降水过程,惠东高潭24 h雨量达1 056.7 mm,采用广东省区域雷达拼图产品、MICAPS实况、CFSR逐6 h再分析资料（水平分辨率0.5°×0.5°）,以及广东省国家级地面气象观测站和区域自动站资料,着重分析了此次过程中\     

北半球大气遥相关型冬夏差异及其与温度场关系的探讨

利用55年的NCEP/NCAR再分析资料, 采用合成分析等方法探讨了冬、 夏季北半球大气遥相关型的差异及其与温度场的关系。主要结果有: 北半球冬、 夏季典型的大气遥相关型具有很大的差异, 且大气遥相关路径的偏折与温度场的变化有密切的关系。北半球冬季, 呈经向型分布特征的大气遥相关路径在温度纬向梯度正负号发生改变处发生偏折; 而在北半球夏季, 由于温度场分布呈现纬向特征, 遥相关路径不易产生南北向的偏折, 从而使得异常中心基本上沿纬圈分布, 呈明显的纬向特征。此外, 由于冬季等温线南北起伏明显的区域往往位于东西方向海陆交界处, 因此冬季大气遥相关路径往往在东西向海陆交界处发生偏折。     

The mechanism of the banded structure of drifting macroalgae in the Yellow Sea

At the end of May 2008, a massive bloom of macroalgae occurred in the western Yellow Sea off China and lasted for nearly two months, and annual blooms have occurred since then on. During bloom period, the surfacedrifting macroalgae have showed an interesting pattern dominated by a banded structure, and the distance between neighboring bands ranged from hundreds of meters to about 6 km with a peak at 1–1.5 km, which is an order of higher than the scale of Langmuir circulation of 50–100 m. In order to explain this new phenomenon,ocean current data obtained from a Doppler current profiler off Qingdao was used to implement stability analysis.By numerically solving the resulting differential Orr-Sommerfeld equation, the secondary circulation induced from the instability of the Emkan current was found to fit well with the observed spatial scale of the surfacedrifting macroalgae's banded structure. As the wind driven Emkan current exist universally in the global ocean, it is reasonable to conclude that the banded structure with kilometers distance between adjoining bands is ubiquitous. We found a new circulation in the upper ocean which is important for exchange of energy, materials and gas between the upper ocean and subsurface layer.     

Zonal distribution features of high frequency planetary waves in the oceans derived from satellite altimeter data

1IntroductionTheavailabilityofnearly9aofhighqual-itysealevelanomaly(SLA)datafromsatellitealtimetersmakesitnowpossibletoestimatethedominantsignalsofvariabilityintheglobalo-ceanmoreaccuratelythanwaspreviouslypos-sible.Moreover,mergingtheT/PandERS-1and2altimeterdatathroughanadvancedglobalobjectiveanalysiscangreatlyimproveoura-bilitytoaccuratelyestimateoceanicvariabili-tycomparedwithusingasinglealtimeter(BoulagerandMenkes,1995).ThealtimeterdatarevealthedominantroleofplanetaryRoss-bywavesinocea…     

Tidal effects on temperature iront in the Yellow Sea

Temperature front (TF) is one of the important features in the Yellow Sea, which forms in spring, thrives in summer, and fades in autumn as thermocline declines. TF intensity |ST| is defined to describe the distribution of TF. Based on the MASNUM wave-tide-circulation coupled model, temperature distribution in the Yellow Sea was simulated with and without tidal effects. Along 36°N, distribution of TF from the simulated results are compared with the observations, and a quantitative analysis is introduced to evaluate the tidal effects on the forming and maintaining processes of the TF. Tidal mixing and the circulation structure adapting to it are the main causes of the TF.     

Current Status of Global Ocean Reanalysis Datasets

With the development of the ocean satellite remote sensing technology, the reanalysis of past oceanic observations using modern data assimilation technique and the restructuring of the long-term and consistent gridded data products have made great progress. Such datasets provide us with the most primary research tools to identify the state and evolution of ocean, and understand the role of ocean in climate change and variability at different spatial-temporal scales. In this paper, the current research status in the global reanalysis datasets including some of international global ocean reanalysis projects and the corresponding reanalyzed products were systematically reviewed. In addition, the present status of the domestic research of ocean reanalysis datasets was briefly introduced. The validation of the reanalysis datasets and some quality problems represented by the reanalyzed products, and the Ocean Reanalyses Intercomparison Project were systematically reviewed. Moreover, the prospects of the studies of oceanic reanalysis in the future were also discussed in this paper.