郑州极端高温天气成因分析

采用NCEP／NCAR1°×1°格点资料对2005年6月22—23日郑州出现的40℃以上的极端高温天气成因进行了分析。指出,河套高压是初夏导致郑州乃至黄淮地区西部出现极端高温的重要天气系统。河套高压的形成与高低层暖平流存在着联系。同时高温的产生也与副热带急流有关,河套高压东南侧的强下沉气流是热力和动力共同作用结果,即当河套高压东南部处于高层副热带急流入口区左侧时,动力辐合机制使得此区域的下沉气流极为强盛,由此所产生的晴空辐射增温和下沉绝热增温使得极端高温天气的出现成为可能。另外,地形所产生的焚风效应对高温的形成具有增幅作用。     

How does the Indian Ocean subtropical dipole trigger the tropical Indian Ocean dipole via the Mascarene high？

The variation in the Indian Ocean is investigated using Hadley center sea surface temperature(SST)data during the period 1958–2010.All the first empirical orthogonal function(EOF)modes of the SST anomalies(SSTA)in different domains represent the basin-wide warming and are closely related to the Pacific El Ni o–Southern Oscillation(ENSO)phenomenon.Further examination suggests that the impact of ENSO on the tropical Indian Ocean is stronger than that on the southern Indian Ocean.The second EOF modes in different domains show different features.It shows a clear east-west SSTA dipole pattern in the tropical Indian Ocean(Indian Ocean dipole,IOD),and a southwest-northeast SSTA dipole in the southern Indian Ocean(Indian Ocean subtropical dipole,IOSD).It is further revealed that the IOSD is also the main structure of the second EOF mode on the whole basin-scale,in which the IOD pattern does not appear.A correlation analysis indicates that an IOSD event observed during the austral summer is highly correlated to the IOD event peaking about 9 months later.One of the possible physical mechanisms underlying this highly significant statistical relationship is proposed.The IOSD and the IOD can occur in sequence with the help of the Mascarene high.The SSTA in the southwestern Indian Ocean persists for several seasons after the mature phase of the IOSD event,likely due to the positive wind–evaporation–SST feedback mechanism.The Mascarene high will be weakened or intensified by this SSTA,which can affect the atmosphere in the tropical region by teleconnection.The pressure gradient between the Mascarene high and the monsoon trough in the tropical Indian Ocean increases(decreases).Hence,an anticyclone(cyclone)circulation appears over the Arabian Sea-India continent.The easterly or westerly anomalies appear in the equatorial Indian Ocean,inducing the onset stage of the IOD.This study shows that the SSTA associated with the IOSD can lead to the onset of IOD with the aid of atmosphere circulation and also explains why some IOD events in the tropical tend to be followed by IOSD in the southern Indian Ocean.     

0518号台风"达维"(Damrey)特征分析

0518号台风“达维”于2005年9月26日04时正面袭击海南省,给海南省的经济造成了严重的损失,本文对0518号台风“达维”的形成、发展过程特征进行初步的探讨和分析,为今后更好地预报相似台风积累经验。     

Mixed layer depth front and subduction of low potential vorticity water in an idealized ocean GCM

It is known that there is a front-like structure at the mixed layer depth (MLD) distribution in the subtropical gyre, which is called the MLD front, and is associated with the formation region of mode water. In the present article, the generation mechanism of the MLD front is studied using an idealized ocean general circulation model with no seasonal forcing. First, it is shown that the MLD front occurs along a curve where u _g ·∇T _s = 0 is satisfied (u _g is the upper ocean geostrophic velocity vector, T _s is the sea surface temperature and ∇ is the horizontal gradient operator). In other words, the front is the boundary between the subduction region (u _g ·∇T _s > 0) and the region where subduction does not occur (u _g ·∇T _s < 0). Second, we have investigated subduction of low potential vorticity water at the MLD front, which has been pointed out by past studies. Since u _g ·∇T _s = 0 at the MLD front, the water particles do not cross the outcrop at the MLD front. The water that is subducted at the MLD front has come from the deep mixed layer region where the sea surface temperature is higher than that at the MLD front. The temperature of the water in the deep mixed layer region decreases as it is advected eastward, attains its minimum at the MLD front where u _g ·∇T _s = 0, and then subducts under the warmer surface layer. Since the deep mixed layer water subducts beneath a thin stratified surface layer, maintaining its thickness, the mixed layer depth changes abruptly at the subduction location.     

台风“达维”影响山东的暴雨落区及路径特征分析

利用高空观测资料、地面观测资料、加密自动站资料、NCEP/NCAR全球再分析资料、FY-2E卫星云图等资料对2012年第10号台风"达维"影响山东的暴雨落区分布及路径特征进行了分析。结果表明:暴雨落区主要出现在台风移动路径的右侧及台风中心附近,而且台风中心的右侧降水明显大于左侧。冷空气对台风引起的降水落区影响较大。水汽通量大值区和辐合区分布、中层的强上升运动对暴雨落区有一定作用。温度梯度大值区和假相当位温的分布与暴雨落区较一致。台风"达维"是在300 h Pa引导气流的作用下移动的,其移动路径与500 h Pa总温度线的走向及高空500 h Pa正涡度带的走向一致。此外,台风的移动路径与副热带高压、双台风效应、低层弱冷空气和下垫面等关系较大。     

亚热带喀斯特山区的生态系统特征和恢复途径

亚热带喀斯特山区主要分布于中国西南和华南，其地貌以寒武系、二叠系和碳酸盐岩与碎屑岩夹层组成的峰丛洼地和喀斯特谷地为主^[1]。由于生态环境及其脆弱，加之人类活动干扰严重，这使得该区长期以来资源难以合理开发利用，环境日益恶化。随着我国西部大开发战略的实施，环境的恶化，经济的落后和不合理的资源开发利用等问题已引起了地理、岩溶、生态、环境等学术界的高度重视。生态系统的恢复、重建，农业、林业和其他产业的合理规划已成为刻不容缓的问题。     

根据土壤化学特征划分伏牛山亚热带北界

The boundary between subtropical zone and temperate zone is not only important in physical geography, but also attractive in agricultural production. Seven soil profiles studied in this paper are placed along the southern slope of Funiu Mountain at different heights above sea level.Many compositions and properties of these soils have been determined in laboratory. In this paper,the laws of migration and accumulation of soil materials on the southern slope of Funiu Mountain are discussed first, then the division of the boundary between subtropical zone and temperate zone in this area according to soil geochemistry is discussed with qualitative methods and mathematical classification method in which twelve selected indexes such as Km, Saf, Ba, β, Feo/Fet, Mno/Mnt and so on are used. The result indicates that the boundary between subtropical zone and temperate zone on the southern slope of Funiu Mountain is about 950 m above sea level.     

The Faxinal System: Forest fragmentation and soil degradation on the communal grazing land

The Brazilian faxinal is a traditional agrosilvopastoral system, which combines extensive grazing, subsistence cropping and low impact forest extraction, managed within a communal property system. Today it is at serious risk of disappearing due to increasing grazing pressure and logging activities that are leading to environmental problems such as forest fragmentation and soil degradation. The objectives of the study were to: a) evaluate soil physical degradation levels in different grazing areas within the faxinal system; and b) correlate soil degradation, fodder quantity and livestock dynamics in different pasture areas according to the household's location. Landscape mapping, vegetation surveys, and livestock grazing dynamics were assessed. In addition, soil physical parameters were evaluated for each land use (e.g., resistance, bulk density, porosity, moisture, and water infiltration rates). Results showed that livestock grazing and household locations are the main driving forces that lead to forest fragmentation. The household location creates three interrelated gradients in the communal grazing land: 1) soil physical degradation decreases from the pasture areas to araucaria forests; 2) fodder quantity decreases from pastures to araucaria forests; and 3) the livestock grazing intensity decreases from pastures to araucaria forests. In addition, some management practices to mitigate land degradation, including improvement of pastures, installation of removable troughs for drinking water in the upland areas and restriction of livestock from the riparian zone, have been proposed.     

赤道东太平洋海温在副热带高压预报上的应用

鉴于赤道东太平洋海温与副热带高压的相关事实,使用秋冬季海表温度预报夏季副高诸特征量,由此估计我国东部地区汛期雨带位置与降水分布特征。1976—87年的预报试验取得了明显的效果。本文还对其影响机制作了探讨。     

广西早春旱大气环流特征及其成因分析

研究了广西早春旱的大气环流特征和成因的物理原因。指出，澳大利亚高空的高压、副热带高压、热带对流活动及欧亚大陆高压脊等是影响广西早春旱的主要天气系统。早春旱年的南半球及中低纬度的环流系统主要是强澳大利亚高空高压、强副热带高压；中高纬是强高空西风急流，欧亚大陆高压脊偏西，冷空气活动路径偏东。