Alkaline phosphatase activity and its relationship to inorganic phosphorus in the transition zone of the North-western African upwelling system

The enzymatic activity of alkaline phosphatase (APA) was studied in the transition zone between the African upwelling system and the open ocean waters of the Canary Islands region. This region is recurrently dominated by the presence of upwelling filaments that may transport nutrient-enriched waters out into the open ocean before nutrients become exhausted by plankton. Turnover rates by APA were generally low in the whole region, but detectable in all the measurements carried out. On average, turnover rates were higher in the upwelling stations, and APA in those waters seemed to be mainly generated by heterotrophic bacteria to supply easily assimilable organic C. APA outside the upwelling area showed an inverse hyperbolic relationship with increasing phosphate, suggesting the presence of both constitutive and Pi-inducible APA. In these offshore waters, a threshold of 0.1 μM of phosphate could be defined for the regulatory function of Pi on APA. Thus, APA in nutrient-poor waters seemed to be induced to compensate for Pi-deficiency. Turnover rates in the filaments showed basal (probably constitutive) levels, whereas they increased in the surrounding waters, where phosphate concentration presumably did not satisfy plankton P-demands. The fertilising effect of the filaments and associated cyclonic eddies extended to at least 175 km offshore, where basal alkaline phosphatase activities were still found. The magnitude of this effect depends probably on the intensity of upwelling events and the degree of recirculation of filament water back to the coastal jet.     

5月3～5日珠江三角洲暖区强降水过程分析

本文通过对2003年5月3～5日珠江三角洲地区出现的暖区暴雨到大暴雨．局部特大暴雨过程的天气尺度及中尺度系统的分析．总结出一些暖区强降水出现的规律。     

一次江淮大暴雨过程中尺度系统结构分析

本文应用观测资料和中尺度数值模拟结果对1999年6月23日发生在江淮地区一次梅雨锋暴雨过程进行研究，揭示了影响这次暴雨过程的物理条件、云团的演变特征及与中尺度系统的关系，分析表明，在暴雨生成和发展过程中，多个中尺度云团在相继生成和移动发展，暴雨中心是几个发展较强的中尺度对流云团造成的，西南风低空急流为暴雨提供了水汽输送，并且通过强垂直运动向对流层中上层输送水汽，这次暴雨与中尺度系统发生发展有直接关系，西南涡分裂出一系列的小涡旋，这些小涡旋边向东移边减弱，并且同时在地面上引发小低压，这些中尺度低压增强低空水平辐合，成为触发不稳定能量的机制，低空急流中心与雨区相互对应，且急流风速增强，风速水平切变梯度增大的过程对应着强降水过程。     

Simulated eddy induced vertical velocities in a Gulf of Alaska model

Mesoscale eddies can distribute nutrients, heat and fresh water into the Gulf of Alaska (GOA) from the coastal margins. While many studies have investigated the physical characteristics of GOA eddies, their effects on passive-dispersive particles have not been previously simulated to investigate eddy induced upwelling. A climatologically forced Parallel Ocean Program simulation of the north Pacific Ocean with an online particle tracking scheme was used to simulate passive-dispersive particles in the Gulf of Alaska. In-eddy vertical Lagrangian velocities of the particles were calculated both inside and outside the eddies and showed upwelling rates are generally greater inside the eddies where the vertical velocities of the particles ranged from 0.2 to 0.7 m/day.     

“96·8”特大暴雨和中尺度系统发展结构的非静力数值模拟

1996年8月3～5日(“96     

青藏高原上中尺度对流系统东移传播成因

运用1998年夏季日本静止气象卫星探测反演出的红外辐射亮温资料,对青藏高原上的中尺度对流系统(MCSs)进行了自动追踪,进而对移出高原的MCSs进行了分类,在此基础上,运用空间数据挖掘中的决策树方法得到了东移出高原的MCSs与其环境物理量场之间的关系,结果表明,在400hPa上,当MCSs的中心位置位于100°E附近时,移出高原且向东南方向移动的MCSs仅与该等压面上的高度和温度有关;而向东北方向移动的MCSs仅与高度和假相当位温有关;此外,移出高原且方向向东的MCSs主要决定于等压面高度、散度、涡度和假相当位温这4个物理量值。在500hPa上,位于东经104°E以西且最终移出高原的MCSs,决定其是否移向东北方向的环境物理量因素为K指数和水汽通量散度,而影响其向东南及东方向移动的因素则较多。     

海南岛附近四季风场的中尺度环流

利用一层σ坐标原始方程数值诊断模式研究海南岛，雷州半岛及其四周海域的地面风场特征，在春夏秋冬四季典型盛行气流下试验，均明显呈现绕流，爬坡，辐合线、海陆风和山谷风效应，看出在不同季节下的中尺度环流存在一定的差异。试验表明，区域内的复杂地形和海陆分布是形成各种中尺度环流的重要原因，同时，揭示出本地气候分布的特征与中尺度环流间存在的密切的关系。     

湿斜压大气中暴雨中尺度系统发展的一种可能机制

根据暴雨中尺度系统发生时的大气运动特征,在绝热、无摩擦条件下,从湿斜压原始方程出发,考虑大气运动的涡度及散度演化不仅受动力场的制约,而且还受到热力场的约束,采用不同于传统研究涡度及散度方程的分析方法,导出了新形式的涡度及散度方程。在此基础上,分析了湿斜压大气中对流层中低层气流旋转与辐合持续增长的动力特征,初步揭示了湿斜压大气中暴雨中尺度系统发展的动力机制。     

Stochastic modelling of unresolved eddy fluxes

A subgrid-scale parameterization scheme motivated by statistical closure theory, but employing statistics obtained from high-resolution direct numerical simulations, is applied to large eddy simulations of two-level quasigeostrophic turbulence on the sphere. It is shown that these parameterizations are consistent with the phenomenology of quasigeostrophic turbulence. The parameterizations consist of 2 × 2 dissipation and stochastic forcing covariance matrices at each wavenumber, with the off-diagonal elements of the matrices representing vertical mixing. Two flow regimes, characterized by their deformation scales, are considered, namely atmospheric and oceanic. In the former, the deformation scale is fully resolved, and the truncation scale is within the enstrophy cascading interial range. In the latter, the deformation scale is not fully resolved, and the truncation scale is within the energy cascading inertial range. It is demonstrated through numerical experiments that both stochastic and deterministic variants of the scheme give comparable results for the energy spectra in the atmospheric regime. In the oceanic regime, the stochastic variant again gives excellent results, but the deterministic variant is found to be numerically unstable.     

Review of Development and Application of High Resolution Global Climate System Model

Climate models have been used as an important tool to quantitatively study climate variability and to predict or project climate change in the future. One of the most important pathways for development and improvement of climate system model is to increase the spatial resolution and improve the corresponding physical parameterization schemes, which is very important for understanding climate change and improving climate prediction skill. Based on a brief introduction of the importance of developing high-resolution global climate system model, a review of recent progresses in the development and application of high-resolution models was summarized. The paper also introduced the current situation and problems for the development and evaluation of high-resolution models and focused on the key scientific and technical bottlenecks which restrict the development of high-resolution models, including the development of dynamic framework of the high-resolution ocean and atmospheric models and massive high performance parallel computing, the improvement of the sub-grid physical parameterization scheme, and mesoscale air-sea interaction. Meanwhile, the scientific objects and experiments design of the international high resolution climate model intercomparison project (HiResMIP) of the coupled model intercomparison project phase 6 (CMIP6) was introduced. Finally, we prospect the future developments and evaluations of high-resolution climate models in China was proposed.