The tropical intraseasonal oscillation in SAMIL coupled and uncoupled general circulation models

Simulations of tropical intraseasonal oscillation(TISO) in SAMIL,the Spectral Atmospheric Model from the Institute of Atmospheric Physics(IAP) State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) coupled and uncoupled general circulation models were comprehensively evaluated in this study.Compared to the uncoupled model,the atmosphere-ocean coupled model improved the TISO simulation in the following aspects:(1) the spectral intensity for the 30-80-day peak eastward periods was more realistic;(2) the eastward propagation signals over western Pacific were stronger;and(3) the variance distribution and stronger signals of Kelvin waves and mixed Rossby gravity waves were more realistic.Better performance in the coupled run was assumed to be associated with a better mean state and a more realistic relationship between precipitation and SST.In both the coupled and uncoupled runs,the unrealistic simulation of the eastward propagation over the equatorial Indian Ocean might have been associated with the biases of the precipitation mean state over the Indian Ocean,and the unrealistic split of maximum TISO precipitation variance over the Pacific might have corresponded to the exaggeration of the double Intertropical Convergence Zone(ITCZ) structure in precipitation mean state.However,whether a better mean state leads to better TISO activity remains questionable.Notably,the northward propagation over the Indian Ocean during summer was not improved in the mean lead-lag correlation analysis,but case studies have shown some strong cases to yield remarkably realistic northward propagation in coupled runs.     

一种模拟非均匀介质中弹性波传播新的k-space方法

传统的伪谱(PS)方法,采用傅里叶变换(FT)计算空间导数具有很高的精度,每个波长仅需要两个采样点,而时间导数采用有限差分(FD)近似因而精度较低.当采用大时间步长时,由于时空精度不平衡,PS法存在不稳定性问题.原始的k-space方法可以有效地克服这些问题但是却无法适用于非均匀介质.为了提高原始k-space方法模拟非均匀介质波动方程的精度,我们提出了一种新的k-space算子族.它是用非均匀介质的变速度代替原k-space算子中的常数补偿速度构造得到,引入低秩近似可以高效求解.我们将构造的新的k-space算子应用于耦合的二阶位移波动方程,而不是交错网格一阶速度应力波动方程,使模拟弹性波的计算存储量减少.我们从数学上证明了基于二阶波动方程的k-space方法与基于一阶波动方程的k-space方法是等价的.数值模拟实验表明,与传统的PS、交错网格PS和原始的k-space方法相比,我们的新方法可以在时间和空间步长较大的均匀和非均匀介质中,为弹性波的传播提供更精确的数值解.在保持稳定性和精度的同时,采用较大的时空采样间隔,可以大大降低数值模拟的计算成本.     

混合层的建立对一次强阵风天气过程的影响

利用NCEP再分析资料和常规地面观测资料,分析混合层的建立对2012年3月23日天津地区强阵风天气过程的影响机理。结果表明：强气压梯度和强变压梯度的共同动力作用是地面强阵风形成的背景条件。强阵风出现在午后气温较高、湿度较低且地面气压较低的时段。午后深厚混合层内的干热对流使高空急流北侧下沉气流将动量下传至对流层中层后向近地面层进一步有效下传,导致地面阵风增大。深厚混合层的建立也是地面强阵风形成的一个重要原因。WRF模拟结果表明,局地混合层强度差异使高空动量下传产生局地差异,这可能是天津各地区阵风强度存在空间差异的重要原因。     

ARTIFICIAL NEURAL NETWORK CORRECTION OF ROUGH ERRORS OF OBSERVATIONS

In the context of tower measured radiation datasets.following the correction principle meetinga diagnostic equation in data quality control and in terms of a technique for model construction ondata and ANN(artificial neural network)retrieval for BP correction of radiation measurementswith rough errors available,a BP model is presented.Evidence suggests that the developed modelworks well and is superior to a convenient multivariate linear regression model,indicating its wideapplications.     

湛江港雷州湾海水增养殖资源的开发利用

综述了湛江港、雷州湾的地理环境、气候、海岸水文、水化、水产资源等基本情况,介绍了鱼、虾、贝、藻的生产历史和现状,提出了资源开发利用的建议。     

Are Io's Alfvén wings filamented? Galileo observations

The interaction of Io with the Jovian magnetosphere generates auroral and radio emissions. The underlying electron acceleration process is not understood and few observations exist to constrain the theoretical models. The source of energy for the electron acceleration is in all likelihood supplied from the Alfvén wings that stretch out from both poles of Io into the two Jovian hemispheres. The form of the current system associated with the Alfvén wings has been disputed, some suggesting that the greatly slowed flow near Io implies that a steady current loop links Io to Jupiter's ionosphere, others arguing that the return waves appear only downstream of Io and others suggesting that both forms develop. Given the finite inclination of the Alfvén wings implied by the finite value of the Alfvén Mach number and the strong reflection that occurs at the boundary of the Io torus, we argue that no steady current loop can be invoked between Io and Jupiter's ionosphere. However, the energetics of the auroral and radio emissions imply that most of the energy in the Alfvén wings is transformed into electron acceleration at high-latitudes, that is, outside the Io torus. The dilemma then is to understand how a large fraction of the power penetrates the reflecting boundary. We present data from Galileo's multiple flybys of Io that suggest that the coupling with the Jovian ionosphere is mediated by filamentary Alfvén wings associated with electromagnetic waves propagating out of the torus. In particular, we report on the systematic observation, within the cross-section of Io's Alfvén wings and in their immediate vicinity, of intense electromagnetic waves at frequencies up to several times the proton gyrofrequency. We interpret these “high-frequency/small-scale” waves as the signature of a strong filamentation/fragmentation of the Alfvén wings before they reflect off of the sharp boundary gradient of the Io torus. As a consequence, we suggest that most of the primary energy is converted into “high-frequency/small-scale” electromagnetic waves that can propagate out from the torus toward Jupiter's ionosphere. Reaching high-latitudes, these waves are able to accelerate electrons to almost relativistic speeds.