The roles of different mechanisms related to the tide-induced fronts in the Yellow Sea in summer

In summer, the Yellow Sea Cold Water Mass （YSCWM） is a stable water mass of low temperature lying at the bottom of the central Yellow Sea （YS）. It is fringed by some typical tidal fronts, which separate deep, stratified water on the offshore side from the well-mixed, shallow water on the inshore side. Three striking fronts--Subei Bank Front （SBF）, Shandong Peninsula Front （SPF）, and Mokpo Front （MKF; a front off the southwestern tip of the Korean Peninsula）--have been iden- tified by various studies from both satellite observations and model results. Tide plays an important role in the formation and maintenance of these fronts. However, it is still a matter of debate as to the roles these two kinds of mechanisms of upwelling and tidal mixing play, and how importance they are in the maintenance processes of the above three fronts. Basing a nested high-resolution model HYCOM （the Hybrid Coordinate Ocean Model）, this study focuses on the different mechanisms of tidal effects on the thermal fronts in the YS in summertime. Through comparative experiments with and without tidal forcing, the results indicate that the MKF is mainly driven by tide-induced upwelling. For the SPF, tidal mixing is the dominant factor, when lower cold water is stirred upwards along the sloping topography of the western YS. Meanwhile, the combined effect of upwelling and tidal mixing is the main cause of the formation of the SBF. Diagnostic analysis of thermal balance shows that horizontal nonlinear advection induced by strong tidal currents also contributes to the thermal balance of frontal areas.     

O3浓度增加对冬小麦影响的试验研究

利用OTC 1型开顶式气室对冬小麦进行不同O3 浓度处理的试验研究。结果表明 ,O3 浓度增加 ,冬小麦发育期表现为开花前期有所延迟 ,开花后期的各发育期明显提前 ,生育期缩短 ,植株矮化 ,干物质累积量明显下降。无论是长时期通气处理还是阶段性通气处理 ,产量均明显降低     

对ENSO循环机理的一些新认识

近几年国内学者通过资料诊断、理论分析和数值试验,对ENSO循环的机理提出了一些新的看法,其中包括El Nino和La Nina的起源,与ENSO循环相联系的暖、冷水的传播过程,热带西太平洋纬向风应力异常,以及热带东太平洋经向风应力异常在ENSO循环中的动力作用等.作者介绍了我国在这些方面的一些研究成果.     

IMPACT OF UPLIFT OF TIBETAN PLATEAU AND CHANGE OF LAND-OCEAN DISTRIBUTION ON CLIMATE OVER ASIA

Using an improved CCM1/NCAR climate dynamic model and a combination distribution ofland-ocean-vegetation during 40-50 MaBP,a series of numerical experiments representingdifferent stages of the Tibetan Plateau uplifting and different land-ocean distributions are designedto discuss the influence of the Plateau uplifting and land-ocean distribution variation on Asianclimate change.It is shown that Tibetan Plateau uplifting can firstly increase the precipitation inChina during the period from initial uplift to half height of modern Tibetan Plateau and thendecrease the rainfall during the time from the half height to the present plateau.At the same time.the uplifting can reduce surface air temperature over China.Besides.the effects of the uplift andland-ocean distribution change on the variation of winter and summer Asian monsoon circulationare also discussed.     

THE ROLES OF BOUNDARY-LAYER DYNAMICS ON THE DEVELOPMENT OF MADDEN-JULIAN OSCILLATION

In this paper,a tropical atmospheric model of relevance to shorts-term climate variations(Wang and Li 1993)is util-ized for study of the development of Madden-Julian oscillation.The model contains an interactive process ofboundary-layer Ekman convergence and precipitation heating.The model is solved by expanding dependent variables interms of parabolic cylindrical functions in the meridional direction and truncating three meridional modes n=0,2,4 forequatorial symmetric solutions.The free wave solutions obtained under long-wave approximation are induced as aKelvin wave and two Rossby waves.After considering the effect of boundary-layer dynamic process,the modifiedKelvin wave becomes unstable in long-wave bands with a typical growth rate on an order of 10~(-6) s~(-1)and an eastwardphase speed of 10 m s~(-1);the most unstable mode is wavenumber one.These theoretical results are consistent with the ob-served Madden-Julian oscillation in equatorial area.For the two modified Rossby waves,one with a smaller meridionalscale(n=4)decays except for extra long-waves;the other with a larger meridional scale(n=2)grows in short-wavebands.This may be relevant to explaining the westward propagation of super cloud clusters in the Madden-Julianoscillation.The theory suggests that the boundary-layer dynamic process is an important mechanism in the develop-ment of the Madden-Julian oscillation.     

热带地转适应运动的动力学基础

文中讨论了热带斜压大气地转适应过程中的若干动力学约束关系,在不考虑行星位势涡度梯度的前提下给出了三维重力惯性波的频散方程、位势涡度时间不变式。在这基础上指出由于Taylor-Proudman定理成立,运动将趋于水平化。同时指出,在热带纬圈半地转平衡更易出现。地转适应后的运动,一般是水平无辐散的,虽然垂直运动趋于零,但物理场随高度仍然有变化,即是层结的。     

Real-Time Observation on Water-Soluble Ions of PM_(2.5)in Beijing under the Influences of Different Air Masses in Summer

To further understand the variations of water-soluble ions in PM2.5 in Beijing,the authors observed their concentrations continuously and in high temporal resolution by the system for rapid collection of fine particles and ion chromatography(RCFP-IC) during 12–18 July 2010.These results combined with those of earlier backward trajectory research are used analyzed to determine the causes of concentration changes in water-soluble ions under the influences of two kinds of air masses in summer.The results indicate that concentrations of NO3-,SO42-,and NH4+ were influenced strongly by the continental air mass than by the marine air mass.Cl- and Na+ were not changed significantly.Because the sources of K+,Mg2+,and Ca2+ are mainly concentrated on land,their concentration levels were slightly higher under the control of continental air mass than that of the marine air mass.Variations of NO2- during the observation differed from those of other ions;its concentration was significantly higher under the influence of marine air mass.Moreover,the authors obtain the diurnal variations of eight water-soluble inorganic ions including NH4+,K+,Mg2+,Ca2+,Cl-,NO2-,NO3-,and SO42-.Diurnal variations of NH4+,NO3-,and Cl- showed single peak,which appeared before noon,while SO42- showed two peaks that appeared during rush hours.Those of Mg2+,Ca2+,and K+ showed single peak that appeared in the afternoon.That of NO2- showed with a peak appearing at sunrise and a valley appearing at sunset.     

ENSO动力学与预测

发生在热带太平洋地区的ENSO现象是海气相互作用的集中表现,是年际气候变化中的最强信号.由于它的发生会在全球许多地区引起严重的气候异常,极大地影响着这些地区的工农业生产和人民生活,因此,对ENSO的机理及其预测的研究一直是大气海洋界的一个热点研究课题.中国科学院大气物理研究所在ENSO的机理及其预测等方面进行了大量的研究,取得了许多研究成果.作者将对中国科学院大气物理研究所在这方面的一些研究成果进行回顾和介绍.     

简单的热带海气耦合波——Rossby和Kelvin波的相互作用

本文分析了当大气和海洋中未经耦合前的自由波分别为Kelvin波和Rossby波,经相互作用后所产生的耦合波的性质。结果表明,不管大气的自由波为Kelvin波或Rossby波,而海洋的自由波为Rossby波或Kelvin波,经相互作用后的耦合波可以分成两类。一类耦合波的色散关系接近自由的Kelvin波;另一类则由不同经圈模的Rossby波经相互作用后的耦合波。这两类波都具有不稳定性。文中讨论了耦合波的传播和不稳定的物理机制,并指出这类不稳定的热带耦合波,对研究ENSO事件中的某些现象有一定的参考意义。     

Real-Time Observation on Water-Soluble Ions of PM2.5in Beijing under the Influences of Different Air Masses in Summer简

To further understand the variations of water-soluble ions in PM2.5 in Beijing,the authors observed their concentrations continuously and in high temporal resolution by the system for rapid collection of fine particles and ion chromatography（RCFP-IC） during 12–18 July 2010.These results combined with those of earlier backward trajectory research are used analyzed to determine the causes of concentration changes in water-soluble ions under the influences of two kinds of air masses in summer.The results indicate that concentrations of NO3^-,SO4^2-,and NH4＋ were influenced strongly by the continental air mass than by the marine air mass.Cl^- and Na^＋ were not changed significantly.Because the sources of K^＋,Mg^2＋,and Ca^2＋ are mainly concentrated on land,their concentration levels were slightly higher under the control of continental air mass than that of the marine air mass.Variations of NO2^- during the observation differed from those of other ions;its concentration was significantly higher under the influence of marine air mass.Moreover,the authors obtain the diurnal variations of eight water-soluble inorganic ions including NH4^＋,K^＋,Mg^2＋,Ca^2＋,Cl^-,NO2^-,NO3^-,and SO4^2-.Diurnal variations of NH4^＋,NO3^-,and Cl^- showed single peak,which appeared before noon,while SO4^2- showed two peaks that appeared during rush hours.Those of Mg^2＋,Ca^2＋,and K＋ showed single peak that appeared in the afternoon.That of NO2^- showed with a peak appearing at sunrise and a valley appearing at sunset.