美国国家水文数据综述

美国国家水文数据是美国最新的数字地理空间数据库内容之一 ,是一种基于要素的复合矢量数据产品。美国国家水文数据为数据的增加、删除和改正设计了专门的方法 ,同时还涉及有自动识别和追踪更新数据的功能。介绍了美国国家水文数据的数据源和数据用途 ,分析了其数据特征 ,描述了其独特的数据更新方法 ,可供国内同行设计此类基础地理信息产品时参考。     

Strong motion dataset of Turkey: data processing and site classification

Strong motion records of Turkey are studied in order to prepare a catalog to be used as a database for further studies (for instance empirical attenuation laws). The network started to be installed in 1973, and the first record was obtained in 1976. The instruments are of SMA-1 analog recorders and SIG SM-2 and GeoSys GSR-16 digital types. Out of a total of 426 records released on the web sites of the General Directorate of the Disaster Affairs and of Kandili Observatory, a set of 210 records was selected with a satisfactory quality, for which it was possible to associate correctly determined source parameters (source magnitudes and epicentral distances). Most of the records are obtained from around North and East Anatolian Fault zones, as well as from western and southwestern parts of Turkey. The main outcome of this paper is a strong motion catalog of Turkey, with the indication of site conditions, of the frequency band of the reliability of the records, peak values of acceleration, velocity and displacements, source parameters (magnitude, epicentral and macroseismic distances), intensity and finally the fault plane solutions whenever possible. The aim is to have, with other regional dataset, a homogenous and good quality dataset.     

利用插值法建立历史旱涝格点资料的可行性

主要利用《中国近五百年旱涝分布图集》等历史文献旱涝等级资料,采用气候学分析中常用的插值方法,建立中国东部地区(106°—122°E、25°—41°N)历史时期旱涝等级格点场资料,试图从大尺度的时空变化上,分析比较插值前后资料的结构和特征方面的异同,以说明采用格点资料对中国东部地区进行古气候分析的可行性。采用普通Kriging插值法,对1470—2000年中国东部地区旱涝等级资料进行空间插值。通过交叉验证,分析了站点实际值与估算值间的平均绝对误差,说明采用Kriging插值法将站点旱涝等级资料网格化是可行的;在获取插值结果后,采用数理统计分析方法,比较了插值前站点资料与插值后网格点资料的要素场时空特征,其时间变化趋势的一致性及空间分布的无漂移,进一步说明采用该插值方法是可行的。     

CHOSEN: A synthesis of hydrometeorological data from intensively monitored catchments and comparative analysis of hydrologic extremes

Comparative hydrology has been hampered by limited availability of geographically extensive, intercompatible monitoring data on comprehensive water balance stores and fluxes. These limitations have, for example, restricted comprehensive assessment of multiple dimensions of wetting and drying related to climate change and hampered understanding of why widespread changes in precipitation extremes are uncorrelated with changes in streamflow extremes. Here, we address this knowledge gap and underlying data gap by developing a new data synthesis product and using that product to detect trends in the frequencies and magnitudes of a comprehensive set of hydroclimatic and hydrologic extremes. CHOSEN (Comprehensive Hydrologic Observatory Sensor Network) is a database of streamflow, soil moisture, and other hydroclimatic and hydrologic variables from 30 study areas across the United States. An accompanying data pipeline provides a reproducible, semi-automated approach for assimilating data from multiple sources, performing quality assurance and control, gap-filling and writing to a standard format. Based on the analysis of extreme events in the CHOSEN dataset, we detected hotspots, characterized by unusually large proportions of monitored variables exhibiting trends, in the Pacific Northwest, New England, Florida and Alaska. Extreme streamflow wetting and drying trends exhibited regional coherence. Drying trends in the Pacific Northwest and Southeast were often associated with trends in soil moisture and precipitation (Pacific Northwest) and evapotranspiration-related variables (Southeast). In contrast, wetting trends in the upper Midwest and the Rocky Mountains showed few univariate associations with other hydroclimatic extremes, but their latitudes and elevations suggested the importance of changing snowmelt characteristics. On the whole, observed trends are incompatible with a ‘drying-in-dry, wetting-in-wet’ paradigm for climate-induced hydrologic changes over land. Our analysis underscores the need for more extensive, longer-term observational data for soil moisture, snow and evapotranspiration.     

中国区域再分析湿度资料与均一化探空湿度资料的对比分析

利用1980—2010年中国98个探空站均一化月平均温度和温度露点差资料(OBS)和NCEP/NCAR(NCEP)、ERAInterim(ERA)、JRA-25(JRA)3种再分析月平均比湿资料,使用相似分析、趋势分析等方法对中国区域4种资料高空比湿进行了对比分析。结果表明:(1)从空间分布特征分析,JRA比湿与OBS比湿的空间分布相似系数最大。(2)3种再分析资料比湿普遍大于OBS比湿,除个别站点个别层次外,JRA和OBS比湿更加接近;再分析比湿和OBS比湿的相对偏差随高度增加而增大,且冬春季大于夏季。(3)从长期变化趋势分析,在对流层低层,JRA和0BS比湿较接近,在对流层中高层ERA和OBS比湿较接近。     

Evaluation of ERA-interim monthly temperature data over the Tibetan Plateau

In this study, surface air temperature from 75 meteorological stations above 3000 m on the Tibetan Plateau are applied for evaluation of the European Centre for Medium-Range Weather Forecasts(ECMWF) third-generation reanalysis product ERA-Interim in the period of 1979-2010. High correlations ranging from 0.973 to 0.999 indicate that ERA-Interim could capture the annual cycle very well. However, an average root-meansquare error(rmse) of 3.7°C for all stations reveals that ERA-Interim could not be applied directly for the individual sites. The biases can be mainly attributed to the altitude differences between ERA-Interim grid points and stations. An elevation correction method based on monthly lapse rates is limited to reduce the bias for all stations. Generally, ERA-Interim captured the Plateau-Wide annual and seasonal climatologies very well. The spatial variance is highly related to the topographic features of the TP. The temperature increases significantly(10°C- 15°C) from the western to the eastern Tibetan Plateau for all seasons, in particular during winter and summer. A significant warming trend(0.49°C/decade) is found over the entire Tibetan Plateau using station time series from 1979-2010. ERA-Interim captures the annual warming trend with an increase rate of 0.33°C /decade very well. The observation data and ERA-Interim data both showed the largest warming trends in winter with values of 0.67°C/decade and 0.41°C/decade, respectively. We conclude that in general ERA-Interim captures the temperature trends very well and ERA-Interim is reliable for climate change investigation over the Tibetan Plateau under the premise of cautious interpretation.     

高原地区ERA40与NCEPI再分析资料对比分析

利用ERA40、NCEPI (NCEP/NCAR version Ⅰ)再分析资料以及高原地区的探空资料和1979年青藏高原地区第1次气象科学试验资料,详细的比较了高原地区位势高度的特征.结果表明,两套再分析资料在高原地区具有一定的相似性,但仍存在着明显的差别.相比较而言,高原北部地区ERA40再分析资料除1980-19...     

ECMWF和NCEP再分析资料在青藏高原高度场变化中的对比分析

利用ECMWF和NCEP/NCAR北半球逐月平均的600 hPa、500 hPa和200 hPa高度场再分析资料,对高原地区高度场流型及量值进行对比研究.结果表明:二者在不同的再分析资料中具有一定的相似性,但仍存在着明显的区别.高度场流型的区别由低层向高层依次减小,600hPa高度场除冬季的流型基本一致外,其余三季的流...     

Analysis of clustering and selection algorithms for the study of multivariate wave climate

Recent wave reanalysis databases require the application of techniques capable of managing huge amounts of information. In this paper, several clustering and selection algorithms: K-Means (KMA), self-organizing maps (SOM) and Maximum Dissimilarity (MDA) have been applied to analyze trivariate hourly time series of met-ocean parameters (significant wave height, mean period, and mean wave direction). A methodology has been developed to apply the aforementioned techniques to wave climate analysis, which implies data pre-processing and slight modifications in the algorithms. Results show that: a) the SOM classifies the wave climate in the relevant “wave types” projected in a bidimensional lattice, providing an easy visualization and probabilistic multidimensional analysis; b) the KMA technique correctly represents the average wave climate and can be used in several coastal applications such as longshore drift or harbor agitation; c) the MDA algorithm allows selecting a representative subset of the wave climate diversity quite suitable to be implemented in a nearshore propagation methodology.