基于局部线性嵌入的人工智能台风强度集合预报模型   总被引：3，自引：2，他引：1  

黄颖  金龙  黄小燕  史旭明  金健 《气象》2014,40(7):806-815

利用局部线性嵌入算法通过学习挖掘高维数据集的内在几何结构,高效地实现维数约简和特征提取的能力,论文以2001—2012年共12年6—9月西北太平洋海域内生成的台风样本为基础,将气候持续因子作为台风强度的基本预报因子,采用局部线性嵌入的特征提取与逐步回归计算相结合的预报因子信息数据挖掘技术,以进化计算的粒子群算法,生成期望输出相同的多个神经网络个体,建立了一种新的非线性人工智能集合预报模型,进行了分月台风强度预报模型的建模研究。在建模样本、独立预报样本相同的情况下,分别采用人工智能集合预报方法和气候持续法进行预报试验。试验对比结果表明,前者较后者在6、7、8和9月24 h台风强度预报中,平均绝对误差分别下降了23.34%、24.46%、19.41%和27.45%,4个月的平均绝对误差下降了23.10%;48 h台风强度预报中,6—9月平均绝对误差分别下降了44.82%、16.73%、0.89%和49.26%,4个月的平均绝对误差下降了25.54%。进一步研究发现,在变动局部线性嵌入算法忌近邻个数的情况下,建立的台风强度集合预报模型,其预报结果稳定可靠,相对于气候持续法均为正的预报技巧水平,为台风强度客观预报提供了新的预报工具和预报建模方法。  相似文献   

KEY AREAS OF AIR-SEA INTERACTION IN GLOBAL OCEANS AND STUDY OF THE CLIMATOLOGICAL FEATURES     

张卫青  钱永甫 《热带气象学报(英文版)》2001,7(2):175-186

Seven key areas of air-sea interaction in the global oceans are determined by comprehensive analysis of the global data of monthly mean sea surface temperature (SST), surface wind, temperature, humidity, sea surface sensible heat and latent heat fluxes. The time-lag correlation between SST and each atmospheric element in each key area are focally analyzed to expose the same and the different features of air-sea interaction in different key areas. The results show that the air-sea thermal interaction is strong in each area, SST, temperature and humidity can be fairly replaced with one another, particularly in the central eastern Pacific and the south India Ocean. The dynamic effect on SST is different in different areas and in the central western Pacific such effect is more important. The correlation between sensible heat, latent heat and SST is more significant in the eastern Pacific, the western Pacific and the two major monsoon areas — the northwestern Pacific and the south India Ocean. By analyzing the sustainable correlation probability of SST and every atmospheric element in each key area, we further know that the anomalies of which element, in which area and in which period are well sustained or easily destroyed. This is beneficial not only to prediction, but also to discussion of the physical mechanism of air-sea interaction.  相似文献   

环境污染中三维捕食_被捕食系统生存和绝灭的阈值     

刘宇红  刘志美 《广东海洋大学学报》2007,27(3):96-99

研究了一类受环境污染的3种群系统,得到了三维捕食_被捕食系统持续生存与绝灭的阈值,并由此对系统的正平衡点的稳定性进行了分析。  相似文献   

A new measure for assessing the efficiency of hydrological data-driven forecasting models     

Seok Hwan Hwang  Dae Heon Ham 《水文科学杂志》2013,58(7):1257-1274

Abstract

There is a lack of consistency and generality in assessing the performance of hydrological data-driven forecasting models, and this paper presents a new measure for evaluating that performance. Despite the fact that the objectives of hydrological data-driven forecasting models differ from those of the conventional hydrological simulation models, criteria designed to evaluate the latter models have been used until now to assess the performance of the former. Thus, the objectives of this paper are, firstly, to examine the limitations in applying conventional methods for evaluating the data-driven forecasting model performance, and, secondly, to present new performance evaluation methods that can be used to evaluate hydrological data-driven forecasting models with consistency and objectivity. The relative correlation coefficient (RCC) is used to estimate the forecasting efficiency relative to the naïve model (unchanged situation) in data-driven forecasting. A case study with 12 artificial data sets was performed to assess the evaluation measures of Persistence Index (PI), Nash-Sutcliffe coefficient of efficiency (NSC) and RCC. In particular, for six of the data sets with strong persistence and autocorrelation coefficients of 0.966–0.713 at correlation coefficients of 0.977–0.989, the PIs varied markedly from 0.368 to 0.930 and the NSCs were almost constant in the range 0.943–0.972, irrespective of the autocorrelation coefficients and correlation coefficients. However, the RCCs represented an increase of forecasting efficiency from 2.1% to 37.8% according to the persistence. The study results show that RCC is more useful than conventional evaluation methods as the latter do not provide a metric rating of model improvement relative to naïve models in data-driven forecasting.

Editor D. Koutsoyiannis, Associate editor D. Yang

Citation Hwang, S.H., Ham, D.H., and Kim, J.H., 2012. A new measure for assessing the efficiency of hydrological data-driven forecasting models. Hydrological Sciences Journal, 57 (7), 1257–1274.  相似文献   

Trend and persistence of precipitation under climate change scenarios for Kansabati basin,India     

Ashok K. Mishra  Mehmet Özger  Vijay P. Singh 《水文研究》2009,23(16):2345-2357

With increasing uncertainties associated with climate change, precipitation characteristics pattern are receiving much attention these days. This paper investigated the impact of climate change on precipitation in the Kansabati basin, India. Trend and persistence of projected precipitation based on annual, wet and dry periods were studied using global climate model (GCM) and scenario uncertainty. A downscaling method based on Bayesian neural network was applied to project precipitation generated from six GCMs using two scenarios (A2 and B2). The precipitation values for any of three time periods (dry, wet and annual) do not show significant increasing or decreasing trends during 2001–2050 time period. There is likely an increasing trend in precipitation for annual and wet periods during 2051–2100 based on A2 scenario and a decreasing trend in dry period precipitation based on B2 scenario. Persistence during dry period precipitation among stations varies drastically based on historical data with the highest persistence towards north‐west part of the basin. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Influence of the persistence of circulation patterns on warm and cold temperature anomalies in Europe: Analysis over the 20th century     

Jan Kyselý   《Global and Planetary Change》2008,62(1-2):147-163

Recent studies have pointed out that persistence of the atmospheric circulation over Europe, as measured by residence times of circulation types, has increased since the mid-1980s in all seasons and for most groups of the types. The greater persistence may affect surface climatic anomalies, particularly the frequency and severity of heat and cold waves associated with severe impacts on society and environment. In this paper, relationships between the persistence of circulation types over Europe and extreme surface air temperature anomalies are studied over the 20th century using the Hess–Brezowsky catalogue of large-scale circulation patterns and long-term temperature series at stations covering most of the European continent. Types significantly conducive to heat and cold waves are identified, and temperature anomalies are linked to their persistence. It is shown that more persistent circulation enhances the severity of temperature extremes over the whole area, which is slightly more important for warm than cold temperature anomalies. The changes in both frequencies and residence times of circulation patterns have been supporting sharply rising trends in warm temperature extremes observed over Europe in recent decades, and the circulation changes may also contributed to the fact that trends in cold temperature extremes have been less pronounced or absent in the same period. The findings also emphasize the need for taking into account the persistence of circulation types together with their frequencies when evaluating links between the atmospheric circulation and the surface climate. In global warming context, the effects of the future climate change on the occurrence and severity of temperature extremes may be exacerbated by a more persistent circulation related to a decreased cyclone activity over mid-latitudes and a northward shift of storm tracks.  相似文献   

Possible causes for the persistence barrier of SSTA in the South China Sea and the vicinity of Indonesia     

赵霞  李建平 《大气科学进展》2009,26(6):1125-1136

The persistence barrier refers to the lag correlation of sea surface temperature anomalies (SSTA) showing a rapid and significant decline in a specific season, regardless of the starting month. This implies that there is a decrease in forecast skill for SSTA in this specific season. This paper investigates the possible causes for the persistence barrier of SSTA in the South China Sea (SCS) and its adjacent regions from the perspective of interannual-interdecadal time scales. The results show that the persistence barrier of SSTA exists not only in the SCS, but also in the vicinity of Indonesia south of the equator. The SCS barrier occurs around October--November, while the occurrence of the barrier in the Indonesia region is around November--December. For these two regions, the occurrence of the persistence barrier is closely associated with the interdecadal variability of SSTA, as well as the interannual variability. The persistence barriers in the SCS and the Indonesia region do not exist alone if the interdecadal variability is not considered, because SSTA have a short memory of less than 4 months, regardless of the starting month. Moreover, the influence of the interdecadal variability of SSTA on the persistence barrier of SSTA in the SCS and the Indonesia region may be associated with SSTA in the Indian Ocean and the western Pacific, but is not closely associated with the Pacific Decadal Oscillation. However, compared with the spring persistence barrier (SPB) of ENSO, the close relationship between the persistence barriers in the SCS and the Indonesia region and the interdecadal variability is unique, since the ENSO SPB is not significantly affected by such variability. In addition, although the persistence barriers in both the SCS and the Indonesia region are quite obvious in strong ENSO cases, the interdecadal variability of SSTA also plays a non-negligible role in this relationship.  相似文献   

青藏高原积雪异常的持续性研究   总被引：12，自引：8，他引：12  

韦志刚 《冰川冻土》2001,23(3):225-230

选取青海省和西藏自治区境内的72个气象站，自建站至1999年12月逐日观观测的积雪深度资料，规定观测到地面有0．5cm以上积雪深度的日子作为积雪日，分别统计了月、冬春、年的积雪日数，通过对积雪日数的分析，确定出高原冬春积雪的异常年份。分析了这些异常年份高原积雪的持续特征，结果表明，高原冬春总体积雪的异常主要是由11月至翌年3月的积雪异常决定的，高原冬春的积雪异常和春末夏初的积雪异常是不相一致的；一般来讲，高原积雪负异常至少持续4个月，大多数般到3月份就结束了；高原冬春总体积雪的正负异常都很难持续到春末夏初，高原冬春异常多积雪的大规模消融期在2月末到3月初。  相似文献   

月平均位势高度场异常持续性初步分析     

李丽平  李巧萍  王盘兴 《南京气象学院学报》2002,25(3):380-387

使用NCEP/NCAR的500hPa月平均位势高度场球函数展开系统资料，分析了北、南半球1、7月具有较大年际异常方差贡献的5种低阶球函数（全波数n=0-4)分量振幅异常的持续性，以及它们与热带太平洋海表温度年际异常的关系。结果表明：振幅异常的持续性随n增大迅速减小，明显的持续性只存在于少数低n值超长波分量；均匀球函数分量振幅异常的持续性显著，且存在季节、半球际差异；北、南半球均匀球函数分量（n=0)振幅异常呈准同步变化，它们与热带太平洋SSTA在ENSO尺度上准同步；南半球n=2的带型球函数分量振幅异常也具有较强的持续性，且其变化与热带太平洋SSTA在年代际尺度上准同步。  相似文献   

北半球夏季５００hPa候平均高度场异常持续性的分析   总被引：1，自引：0，他引：1  

江剑民  钱传海 《大气科学》1994,18(2):200-206

本文应用环流持续性异常判据和旋转主分量分析方法，对１９５１—１９８６年间夏季北半球５００hPa逐候平均高度场进行了计算分析，探讨夏季持续性环流异常的地理分布及持续期的基本特征。结果表明:前１１项旋转主分量的主要高荷载中心，与持续异常的高频数中心或其邻近区域大都基本吻合；候平均环流异常的持续性略高于马尔柯夫过程。但某些区域季节性环流异常及多年趋势性环流异常，通常是由某些环流系统或作用中心多次替换、反复出现的持续性异常所组成的。夏季副热带系统是这类异常的重要组成部分。  相似文献