２００２年海南一次非热带气旋暴雨成因分析     

吴春娃  赵付竹  王凡 《陕西气象》2011,(2):1-3

本文对2008年8月10日出现在北京首都机场的一次暴雨天气过程,从天气形势、物理量场、卫星产品、雷达资料等多方面进行了分析,结果表明,此次强降水发生在高空有利的环流背景下,锋面抬升、高低层温度差动平流、中层辐合、中低层风切变、中层暖干盖的存在以及副高的维持均为强降水的产生提供了有利条件。  相似文献   

Modelling the Gross Primary Productivity of West Africa with the Regional Biomass Model RBM+, using optimized 250 m MODIS FPAR and fractional vegetation cover information     

《International Journal of Applied Earth Observation and Geoinformation》2015

Global warming associated with climate change is one of the greatest challenges of today’s world. Increasing emissions of the greenhouse gas CO₂ are considered as a major contributing factor to global warming. One regulating factor of CO₂ exchange between atmosphere and land surface is vegetation. Measurements of land cover changes in combination with modelling the Gross Primary Productivity (GPP) can contribute to determine important sources and sinks of CO₂.The aim of this study is to accurately model the GPP for a region in West Africa with a spatial resolution of 250 m, and the differentiation of GPP based on woody and herbaceous vegetation. For this purpose, the Regional Biomass Model (RBM) was applied, which is based on a Light Use Efficiency (LUE) approach. The focus was on the spatial enhancement of the RBM from the original 1000–250 m spatial resolution (RBM+). The adaptation to the 250 m scale included the modification of two main input parameters: (1) the fraction of absorbed Photosynthetically Active Radiation (FPAR) based on the 1000 m MODIS MOD15A2 FPAR product which was downscaled to 250 m using MODIS NDVI time series; (2) the fractional cover of woody and herbaceous vegetation, which was improved by using a multi-scale approach. For validation and regional adjustments of GPP and the input parameters, in situ data from a climate station and eddy covariance measurements were integrated.The results of this approach show that the input parameters could be improved significantly: downscaling considerably reduces data gaps of the original FPAR product and the improved dataset differed less than 5.0% from the original data for cloud free regions. The RMSE of the fractional vegetation cover varied between 5.1 and 12.7%. Modelled GPP showed a slight overestimation in comparison to eddy covariance measurements. The in situ data was exceeded by 8.8% for 2005 and by 2.0% for 2006. The model results were converted to NPP and also agreed well with previous NPP measurements reported from different studies. Altogether a high accuracy and suitability of the regionally adjusted and downscaled model RBM+ can be concluded. The differentiation between vegetation growth forms allows a separation of long-term and short-term carbon storage based on woody and herbaceous vegetation, respectively.  相似文献   

黄、渤海冷空气海浪场的集合预报试验   总被引：1，自引：0，他引：1  

王亚男  王庆元  刘彬贤 《海洋学报》2015,37(9):10-16

利用欧洲集合天气预报系统51个预报风场驱动SWAN海浪模式,对黄、渤海2013年12月-2014年2月期间受冷空气影响的海浪场进行数值模拟试验,并利用浮标观测资料对海浪集合预报结果进行初步检验分析,结果显示:从逐时平均偏差结果可知,24h预报时效内集合平均与控制预报性能相近,48~72h预报时效内,集合平均明显优于控制预报,但均比实况偏小;集合分位值(75、90百分位值和极端值)明显优于集合平均,且预报时效越长,优势越明显,集合预报极端值与实况相当或略偏大;从逐24h平均偏差结果可知,集合分位值(75、90百分位值和极端值)比集合平均和控制预报更接近实况。总的分析表明:集合分位值(75、90百分位值和极端值)对受冷空气影响的海浪场具有较强的分辨能力,可以提高对海浪场的预报水平,且有较好的应用潜力。  相似文献   

Regional oceans governance mechanisms: A review     

《Marine Policy》2015

The development of regional governance for the protection of the environment, sustainable use of natural resources and conservation of its biodiversity is unquestionably a cornerstone of international environmental law and policy. With regard to marine and coastal issues, it has mainly been taking place through Regional Seas programmes, Regional Fishery Bodies and Large Marine Ecosystems mechanisms. Based on a similar geographical approach, however, these regional mechanisms raise concerns relating to their coordination and efficiency, and possibly overlap in what they aim to achieve. This paper provides a review of existing regional oceans governance mechanisms, assessing their individual and collective capacities to move towards ecosystem-based management, and highlighting options to make the regional landscape more coherent and effective.  相似文献   

基于稀疏AR模型的潮流信号建模与预报   总被引：1，自引：0，他引：1  

卢小鹏  叶庆卫  吕翠兰 《海洋学研究》2015,33(2):14-18

潮流信号处理与预报在很多方面具有非常重要的意义和价值。本文引入信号稀疏表示理论,构建一种稀疏AR模型,寻找各潮流数据间的历史关联性,并进行预报分析。首先由实测潮流信号进行常规AR建模,获得一组过完备稀疏基;其次随机从该过完备稀疏基抽取部分建立欠定方程组,利用稀疏优化算法获得最稀疏的AR系数;多次重复上一步,获得稀疏AR系数的平均以增强稀疏AR模型的稳定性;最后利用这些稀疏AR系数来重构或预测潮流信号。文章针对实测潮流信号,特别是存在多峰值有回流现象的潮流信号,进行了稀疏AR建模与预测的多次实验。实验结果与传统的潮流信号调和预报方法相对比,发现基于稀疏AR模型的潮流预报对于潮流存在多变的现象时,具有明显优越性,从回报结果来看,稀疏AR模型的潮流预报均方差明显小于传统潮流调和分析预报方法。  相似文献   

青岛近海大型水母漂移集合预测方法研究   总被引：1，自引：0，他引：1  

吴玲娟  高松  刘桂艳  白涛 《海洋预报》2015,32(2):62-71

考虑水母垂直运动等自主运动,基于集合预报和拉格朗日粒子追踪方法,建立青岛近海大型水母的集合漂移预测模型。并利用2012—2013年青岛近海水母实时监测数据和集合漂移预测模型,快速预测水母集合漂移轨迹、速度、趋势和可能影响范围等要素。通过分析水母监测数据和数值模拟结果,在水母如何自主运动及其机理尚不十分清楚的情况下,多轨迹漂移预测结果比单轨迹的更合理、科学、可信,能够传达更多的信息量,对水母灾害的应急处置更具有指导意义。  相似文献   

Deterministic and ensemble storm surge prediction for Atlantic Canada with lead times of hours to ten days     

《Ocean Modelling》2015

Regional deterministic and ensemble surge prediction systems (RDSPS and RESPS respectively) are used to forecast sea levels off the east of Canada and northeast US. The surge models for the RDSPS and RESPS have grid spacings of 1/30° and 1/12° respectively. The models are driven by surface air pressure and 10 m winds generated by operational global deterministic and ensemble prediction systems that are run operationally by the Canadian Meteorological Centre. Surge forecasts are evaluated for the period 1 March, 2013 to 31 March 2014. Based on traditional statistics (e.g., standard deviation of the difference between observations and predictions) both systems are shown to have skill in forecasting surges six days into the future. It is shown however that skill exists beyond six days if allowance is made for errors in the timing of large surges. The usefulness of the RESPS is demonstrated for two positive surges (important for coastal flooding and erosion) and a negative surge (important for safe navigation in shallow water). It is shown that the RESPS can identify events not forecast by the RDSPS, and can also add useful additional information on the timing of the surge, an important consideration in tidally dominated waters. Several new types of display are used to illustrate the sort of information that can be generated by the RESPS to support the issuers of warnings of unusually high and low total water levels.  相似文献   

Correlation －SVM 模型在大坝变形预测中的应用     

朱涛  刘慕溪 《测绘与空间地理信息》2015,(8):37-40

引起大坝变形的影响因素很多,即在利用支持向量机（ SVM）模型进行大坝变形分析和预报的过程中,需要将所有的影响因子都输入到SVM模型中,这样会造成输入因子的不侧重性,基于此,本文对大坝变形的影响因子进行相关性分析,根据大坝变形影响因子和大坝变形量之间的关系来确定最优的影响因子,即将比重比较大的影响因子输入到SVM模型中,从而提高了SVM模型运行效率及预测的精度和速度。  相似文献   

突变理论在边坡工程应用的研究进展     

Fan Liuming  Geng Pengchao 《地球科学进展》2015,30(11):1268-1277

突变理论是非线性科学领域中的一个重要分支,作为一种数学工具已经在众多领域得到广泛应用,在边坡工程中的应用尤为活跃。首先简述了突变理论的发展概况和基本原理,然后分别从3个方面详细论述了突变理论在边坡工程应用中的研究进展,即基于尖点突变法的边(斜)坡稳定性分析、基于突变级数法的边(斜)坡稳定性评价和基于灰色理论、模糊数学的尖点突变预测模型对滑坡时间预报,重点讨论了相应的理论模型、应用方法和实际效果,最后结合目前存在的问题探讨突变理论在边坡工程的发展趋势。  相似文献   

HHT-EEMD用于IGS站高程时间序列分析     

施闯  牛玉娇  魏娜  楼益栋  张双成 《大地测量与地球动力学》2018,38(7):661-667

利用经验模态分解（EMD）和整体经验模态分解（EEMD）方法，将BJFS站2000~2015年高程时间序列进行分解，发现其不仅存在1 a、0.5 a、0.25 a、2个月、1个月以及长周期等周期项，还存在以往方法很难探测出来的近似2 a周期信号。与EMD分解结果对比，整体经验模态分解可以明显减弱模式混叠现象。对各分量进行Hilbert 变换（HHT），得到时间-频率-能量的Hilbert 频谱图。结果表明，年周期和2 a周期变化是高程运动的主要贡献项。利用小波变换方法对比验证EEMD的分解结果表明，与小波分析相比，EEMD重构信号与高程序列差异的RMS更小，证明了HHT-EEMD方法在数据资料分析过程中的有效性。对环境负载及GRACE负载造成的测站位移进行功率谱分析得出，环境负载确实会造成IGS站高程时间序列的1 a、0.5 a以及季节性运动，GRACE负载还验证了2 a信号的存在。  相似文献