A sensitivity analysis of lake water level response to changes in climate and river regimes

Lake water level regimes are influenced by climate, hydrology and land use. Intensive land use has led to a decline in lake levels in many regions, with direct impacts on lake hydrology, ecology and ecosystem services. This study examined the role of climate and river flow regime in controlling lake regimes using three different lakes with different hydraulic characteristics (volume-inflow ratio, CIR). The regime changes in the lakes were determined for five different river inflows and five different climate patterns (hot-arid, tropical, moderate, cold-arid, cold-wet), giving 75 different combinations of governing factors in lake hydrology. The input data were scaled to unify them for lake comparisons. By considering the historical lake volume fluctuations, the duration (number of months) of lake volume in different ‘wetness’ regimes from ‘dry’ to ‘wet’ was used to develop a new index for lake regime characterisation, ‘Degree of Lake Wetness’ (DLW). DLW is presented as two indices: DLW₁, providing a measure of lake filling percentage based on observed values and lake geometry, and DLW₂, providing an index for lake regimes based on historical fluctuation patterns. These indices were used to classify lake types based on their historical time series for variable climate and river inflow. The lake response time to changes in hydrology or climate was evaluated. Both DLW₁ and DLW₂ were sensitive to climate and hydrological changes. The results showed that lake level in high CIR systems depends on climate, whereas in systems with low CIR it depends more on river regime.     

草地螟迁飞、降落与东北冷涡的关系

利用2009年6月内蒙古自治区植保站的草地螟越冬代成虫标记放飞和捕获试验结果,结合2009年6月每日08时和20时500-1000 hPa高空天气图、每日8次的地面天气图等气象信息,分析2009年内蒙古自治区草地螟盛发期自然放飞并回收到的标记成虫的放飞与天气系统的关系。结果表明：草地螟成虫放飞后卷入东北冷涡并随其在控制区内沿逆时针方向旋转的气流飞行,其迁飞方向与天气系统密切相关;气流方向、降水和风力等气象因子是影响草地螟成虫迁飞与降落的主要原因,分析气象因子与草地螟迁飞和降落的关系,有利于进一步认识草地螟在盛发期的迁飞习性;分析草地螟主动降落迁入的气象条件和相关预警指标,对监测草地螟成虫迁入有重要指导意义。     

DIAGNOSTIC ANALYSIS OF THE RE-INTENSIFICATION OF HIGOS IN SOUTHERN CHINA AFTER LANDFALL

The NCEP Global Data Assimilation System analysis of grid data, satellite products of Naval Research Laboratory, conventional meteorological data and observations of automatic weather stations in Guangdong province were used together with environmental conditions, atmospheric circulation, and physical characteristics to diagnose the cause and mechanism of the intensification of tropical cyclone Higos in Southern China. The results showed that favorable environmental conditions of high temperature, humidity of the underlying surface, strong upper divergence, weak vertical wind shear, and the persistence of a southwest jet stream beside the southern Higos were the necessary ingredients that contributed to the maintenance of intensity and re-intensification of Higos. The sinking intrusion of cold air from the lower troposphere was the critical condition for its intensification over land. The frontal genesis caused by weak cold air increased the lower tropospheric convergence and updraft, and the condensation latent heat released by heavy rains promoted convergence. From this positive feedback process, Higos obtained an increasing of positive vorticity and re-intensified over land. The re-intensification was due not only to the build-up of wind and the reduction of pressure but also to the simultaneous warm-up of its warm core.     

2009年造成广东深秋一次急降温冷空气的特点

分析2009年11月中旬广东入秋以来最强的一次冷空气的环流形势,结果表明,此次冷空气属于横槽转竖型,乌拉尔山阻塞高压稳定维持使得冷空气在中高纬堆积,横槽转竖后引导下来的冷空气在南岭山脉受到阻挡。分析冷空气的垂直结构发现,本次冷空气较为浅薄,堆积发生在850hPa以下,弱冷空气经过长时间堆积形成较强冷空气,冷空气带来的阴雨天气使得降温以平流降温为主。     

适应气候变化谈判的焦点问题与趋势分析

综述了近两年在《联合国气候变化框架公约》(简称《公约》)下关于适应气候变化谈判的进展,分析了适应气候变化谈判的焦点问题及各利益集团的立场,结合《公约》第十五次缔约方大会的进展,提出了我国今后在适应气候变化问题上的谈判对策建议。     

赤道太平洋冷舌的春季海表面稳定冷偏差和最小风引起的混合

The authors investigate the relationship between bias in simulated sea surface temperature (SST) in the equatorial eastern Pacific cold tongue during the boreal spring as simulated by an oceanic general circulation model (OGCM) and minimal wind mixing (MWM) at the surface. The cold bias of simulated SST is greatest during the boreal spring, at approximately 3°C. A sensitivity experiment reducing MWM by one order of magnitude greatly alleviates cold biases, especially in March-April. The decrease in bias is primarily due to weakened vertical mixing, which preserves heat in the uppermost layer and results in warmer simulated SST. The reduction in vertical mixing also leads to a weak westward current in the upper layer, which further contributes to warmer SST estimates. These findings imply that there are large uncertainties about simple model parameters such as MWM at the oceanic surface.     

The Cold Tongue in the South China Sea during Boreal Winter and Its Interaction with the Atmosphere

A distinct cold tongue has recently been noticed in the South China Sea during the winter monsoon, with the cold tongue temperature minimum occurring in the January or February. This cold tongue shows significant links with the Maritime Continent’s rainfall during the winter period. The cold tongue and its interaction with the Maritime Continent’s weather were studied using Reynolds SST data, wind fields from the NCEP–NCAR reanalysis dataset and the quikSCAT dataset. In addition, rainfall from the GOES Prec...     

2010年2月大气环流和天气分析

2010年2月主要环流形势为:北半球有三个极涡中心,亚洲极涡的强度偏强,形状扁平;东亚大槽较弱;南支槽接近常年,中上旬较为活跃。这种环流形势使得今年2月影响我国的北支锋区偏弱,冷空气路径偏北。2月主要气候特点:气温偏高,降水接近常年。新疆、浙江降水量较历史同期偏多;云南、贵州、四川南部、广西西部等地气象干旱持续发展;8-13日受寒潮天气影响,我国出现大范围雨雪天气,全国大部地区气温明显偏低,对春运造成严重影响。     

1961～2004年漠河年均温与持续极端气温频数的变化分析

利用漠河站点1961～2004年逐日平均、最高和最低气温资料计算得到的年均温、年变化和季节变化的持续暖口和冷夜频数,分析了它们的线性趋势、增量、显著性和平稳性.其中年均温升高了约1.61℃,年持续暖口频数增加了约4次,冬季持续暖日频数和夏季持续冷夜频数都呈显著增加趋势.分别对年均温和年持续频数的线性回归关系,以及年均温和季持续频数的线性回归关系进行了显著性检验.在线性回归关系显著的情况下,分别就各频数序列埘年均温的影响逐一进行显著性检验,从而揭示了年均温与符频数序列的变化关系.研究结果表明:从按年,变化的角度米分析,年均温的升高是由年持续暖日频数的增加和年持续冷夜频数的减少共同显著影响的;从按季变化的角度来分析,年均温的升高主要由春、夏季持续暖日频数的增加和春、秋季持续冷夜频数的减少共同显著影响的.     

冬季登陆我国的0428和7427号台风过程的冷空气作用和水汽特征

应用NCEP/NCAR再分析资料,对冬季登陆我国的0428和7427号台风过程的冷空气作用和水汽特征进行了研究,结果表明：在初冬季节,东亚大槽引导的冷空气可以到达热带洋面的台风外围;台风与出海高压相向而行, 外围气压梯度增强对台风强度的加强和维持起作用;弱冷空气在低层侵入仍在温暖海面上的台风,气旋扰动加强使台风加强;当强冷空气侵入台风中心中层时会破坏其暖心结构,使其填塞消亡。台风生成于水汽通量辐合带内,其生成和发展引起水汽汇合的扰动,加强水汽的辐合,使水汽辐合带加强;一旦台风脱离水汽辐合带后,不能继续获取大量水汽,则会逐渐减弱消亡;冬季台风过程没有强的水汽输送带。