Multi-model ensemble schemes for predicting northeast monsoon rainfall over peninsular India

The northeast (NE) monsoon season (October, November and December) is the major period of rainfall activity over south peninsular India. This study is mainly focused on the prediction of northeast monsoon rainfall using lead-1 products (forecasts for the season issued in beginning of September) of seven general circulation models (GCMs). An examination of the performances of these GCMs during hindcast runs (1982–2008) indicates that these models are not able to simulate the observed interannual variability of rainfall. Inaccurate response of the models to sea surface temperatures may be one of the probable reasons for the poor performance of these models to predict seasonal mean rainfall anomalies over the study domain. An attempt has been made to improve the accuracy of predicted rainfall using three different multi-model ensemble (MME) schemes, viz., simple arithmetic mean of models (EM), principal component regression (PCR) and singular value decomposition based multiple linear regressions (SVD). It is found out that among these three schemes, SVD based MME has more skill than other MME schemes as well as member models.     

考虑降水预报的三峡入库洪水集合概率预报方法比较

为了考虑预见期内降水预报的不确定性对洪水预报的影响,采用中国气象局、美国环境预测中心和欧洲中期天气预报中心的TIGGE(THORPEX Interactive Grand Global Ensemble)降水预报数据驱动GR4J水文模型,开展三峡入库洪水集合概率预报,分析比较BMA、Copula-BMA、EMOS、M-BMA 4种统计后处理方法的有效性。结果表明:4种统计后处理方法均能提供一个合理可靠的预报置信区间;其期望值预报精度相较于确定性预报有所提高,尤其是水量误差显著减小;M-BMA方法概率预报效果最佳,它能够考虑预报分布的异方差性,不需要进行正态变换,结构简单,应用灵活。     

Dynamic weather forecaster: results of the testing of a collaborative, on-line educational platform for weather forecasting

The online Dynamic Weather Forecaster is an open, collaborative application available now to high-school and college instructors across the United States who would like to easily incorporate weather forecasting in their instruction. The application consists of a set of 13 questions that allow students to submit forecasts that cover most of the parameters used by professional weather forecasters. Submissions are automatically validated against weather parameters and graded. We tested the impact of the application on the learning of 199 undergraduate students in an introductory meteorology course in spring 2008. Students who begin forecasting early in the semester and continue to do so throughout the semester are statistically significantly more successful in the course than students who start late or complete a low number of forecasts. College, year in school, and gender were not significant predictors of success. Students found the application easy to use, and 92.3% of them found it at least somewhat helpful as they learned about the weather. Through the use of the DWF, students also experience first-hand that uncertainty is a critical part of weather forecasting and of scientific studies in general. With sufficient interest from potential users outside the USA, the DWF platform could easily be expanded to include global weather data.     

基于数值天气预报产品的气象水文耦合径流预报

以福建金溪池潭水库流域为例,采用TIGGE数据中心的ECMWF、UKMO、NCEP等7种模式控制预报产品驱动新安江模型,开展径流集合预报。通过集合挑选、多模式集成前处理以及基于BMA模型的后处理等过程,探讨不同处理方案和初始集合质量对气象水文耦合径流预报精度及不确定性的影响。结果表明,不同的处理方案均能有效提高径流预报的精度和稳定性,同时进行前处理和后处理能从降低误差输入和控制误差输出两方面减小预报误差,相对于其他方案表现更好。初始集合质量对气象水文耦合径流集合预报有一定影响,但前处理或后处理对预报误差的有效控制使得该影响并不显著。总体而言,前处理和后处理过程是提高气象水文耦合径流预报准确性和可靠性必不可少的环节,应予以重视。     

Study of the relationship between geopotential height anomaly over Europe and extreme abnormal weather over the Eastern Mediterranean and Middle East during December 2013

The Eastern Mediterranean and the Middle East (EMME) is suffering from abnormal cooling of weather conditions and existence of an extreme weather phenomenon known as ice storm Alexa. The present paper investigates the weather conditions over Europe that causes this abnormal weather over the EMME through December of 2013. Daily data sets of several meteorological elements (temperature, precipitation, relative humidity, sea level pressure, and geopotential height at level 500 hPa, etc.) over the northern hemisphere, including Europe and EMME of December of 2013, have been used through the present work. In addition, to that, a time cross section analysis of the daily operational data for meteorological elements (mean surface temperature, temperature and geopotential height at level 500 hPa, relative humidity, precipitation rate, and sea surface pressure) was done over the EMME for December 2013. The methodology of anomaly and correlation coefficient techniques for the data sets has been used. The results uncovered that the EMME has abnormal and very cold weather conditions due to the inference of meridional blocking persisted over Europe and the existence of the extremely negative geopotential height anomaly aloft over Eastern Europe throughout this month.     

Eastern Mediterranean gravity potential and the Hellenic subduction process

Tornographic images of the Mediterranean upper mantle P-wave velocity structure have been used to analyse the gravity potential in the vicinity of the Hellenic subduction zone. The velocity anomalies are assumed to be proportional to density variations according to Birch's law. The effect of the topography on the geoid in the region is also calculated. The results indicate that the upper mantle geoid signal probably has significant amplitudes of several metres, but it correlates poorly with the observed geoid. The geoid calculated from topography correlates well, but has an amplitude that is too large in comparison with the observed geoid. The results show that an improved understanding of the Hellenic subduction zone geoid requires refinement of the Moho topography, so that the effect of this topography can be separated from the upper mantle signature.     

Origin of the Eastern Mediterranean basin: a reevaluation

The origin of the Eastern Mediterranean basin (EMB) by rifting along its passive margins is reevaluated. Evidence from these margins shows that this basin formed before the Middle Jurassic; where the older history is known, formation by Triassic or even Permian rifting is indicated. Off Sicily, a deep Permian basin is recorded. In Mesozoic times, Adria was located next to the EMB and moved laterally along their common boundary, but there is no clear record of rifting or significant convergence. Farther east, the Tauride block, a fragment of Africa–Arabia, separated from this continent in the Triassic. After that the Tauride block and Adria were separate units that drifted independently. The EMB originated before Pangaea disintegrated. Two scenarios are thus possible. If the configuration of Pangaea remained the same throughout its life span until the opening of the central Atlantic Ocean (configuration A), then much of the EMB is best explained as a result of separation of Adria from Africa in the Permian, but this basin was modified by later rifting. The Levant margin formed when the Tauride block was detached, but space limitations require this block to have also extended farther east. Alternatively, the original configuration (A2) of Pangaea may have changed by 500 km of left-lateral slip along the Africa–North America boundary. This implies that Adria was not located next to Africa, and most of the EMB formed by separation of the Tauride block from Africa. Adria was placed next to the EMB during the transition from the Pangaea A2 to the Pangaea A configuration in the Triassic. Both scenarios raise some problems, but these are more severe for the first one. Better constraints on the history of Pangaea are thus required to decipher the formation of the Eastern Mediterranean basin.     

Kinematics of the Eastern Mediterranean region and the WEGENER-MEDLAS project

The Eastern Mediterranean is a region of complex kinematic behaviour resulting from the collision of the African/Arabian and Eurasian plates. Neither the geodynamic processes nor the kinematic quantities involved in the deformations taking place are well understood and they are subject to several alternative interpretations. Different solutions presented in the literature are discussed as an introduction to the WEGENER-MEDLAS Project, by means of which geodetic data will be introduced in an attempt to help resolve the current pattern of kinematic changes. The manner of field observation and data reduction are discussed along with the practical experience obtained to date and a summary of the first years's field experience and the estimated accuracies of baseline results are presented.Mitteilung aus dem Institut für Angewandte Geodäsie, 6000 Frankfurt 70, FR Germany     

Paleomagnetic reconstruction of the Cenozoic evolution of the Eastern Mediterranean

A total of 113 paleomagnetic sites were sampled along an Anatolian S–N transect from the Arabian platform, the Hatay region, the Eastern Taurides, the Kirsehir block, the Sivas basin and the Eastern Pontides. Reliable characteristic remanent paleomagnetic directions were retrieved from 37 of these sites, spanning in time from Paleocene to Miocene. In a general way, declinations are westerly deviated and inclinations are shallower than the geocentered dipole value at the present latitudes. When combined with previously published results, these data indicate that a large-scale counterclockwise rotation of Anatolia of some 25° has occurred since the Miocene. Assuming that the pole of rotation of Anatolia with respect to Europe has remained constant in time at the location given by MacClusky et al. [J. Geophys. Res. 105 (2000) 5695] on the basis of the geodetic data, this rotation implies that a large westward displacement (500 km at the average latitude of 40°) has taken place. Assuming that the rotation was initiated by the Arabia/Europe collision about 12 Ma ago, this corresponds to an average displacement of about 40 mm/year.Together with previous results from the western part of the Aegean arc, these results indicate that the main trends of the Cenozoic evolution of the Eastern Mediterranean appear to consist of two post-early Miocene rotations of opposite senses: a clockwise rotation of the western part of the Aegean [Tectonophysics 146 (1988) 183] around a pole situated in northern Albania, and a counterclockwise rotation around the pole given by McClusky et al. [J. Geophys. Res. 105 (2000) 5695]. Comparison with GPS data suggest that both rotations are still active today.     

Depositional models for fine-grained sediment in the western Hellenic Trench, Eastern Mediterranean

Sediment in tectonically active, topographically restricted settings of the western Hellenic Arc, eastern Mediterranean, consists primarily of clayey silt and silty clay. Failure of metastable sediment temporarily stored on relatively steep slopes is triggered by earthquake tremors and eustatic oscillations. Redeposition of these materials by gravitative transport has resulted in markedly different lithofacies from site to site. Most piston cores include three Late Quaternary stratigraphic units that can be correlated with sections in other parts of the eastern Mediterranean; numerous radiocarbon-age determinations enhance the correlation. Seven fine-grained sediment types are identified in cores from eight distinct depositional environments. Some muds are closely related to specific environments (slump and debris flow deposits on slope and high-relief environments), or to time (well laminated mud during the latest Pleistocene-mid-Holocene), or to both (uniform and faintly laminated muds restricted to trench basins). Turbiditic and hemipelagic muds are common throughout the study area. Mud distribution patterns correlate closely with calculated sedimentation rates. We propose two depositional models for these sediments. The first emphasizes downslope transformations resulting in progressively reduced flow concentration during transport: from slump and debris flow–>turbidity current–>low density turbidity current or turbid layer mechanisms. The distal end-member deposits settling from low concentration flows are thick, rapidly emplaced, fine-grained uniform muds closely associated with faintly laminated muds. These were ponded in flat trench basin-plains. Planktonic and terrigenous fractions in the turbiditic, finely laminated and uniform muds record mixing of materials of gravitative and suspension origin during redeposition. This sequence prevails under conditions of minimal stratification of water masses, as characterized by the present Mediterranean. In the second model developed for conditions of well-developed water mass stratification, well laminated rather than uniform mud prevails as the end product of low concentration flows. These very finely laminated and graded muds record particle-by-particle settling from detached turbid layers concentrated along density interfaces; they include material from turbid layers complemented by the normal ‘rain’ of pelagic material. Stratification barriers resulted in region-wide distribution of such deposits, in both slope and trench environments.     

多普勒雷达图像在地质灾害气象预警中的应用——以湖南省新邵县“2005．05．31”特大地质灾害气象预警为例

本文介绍了湖南地质灾害概况,通过对暴雨诱发地质灾害的机理分析和多普勒雷达系统监测暴雨的可能性分析,选取地质灾害频发的湖南省作为典型研究区,通过多普勒雷达图像地质灾害气象反演分析和灾害识别研究,精确地预报了湖南省新邵县“2005．05．31”特大地质灾害,论证多普勒雷达是监测突发性地质灾害的有效手段。     

青岛市崂山区地质灾害气象预报预警

本文基于地质灾害递进分析理论与方法，进行了崂山区地质灾害气象预报预警探讨。崂山区地质灾害及隐患点发育的类型主要是滑坡、崩塌和泥石流。据调查，区内地质灾害及隐患点83处，其中已发生灾害17处，新的灾害隐患66处。崂山区地质灾害基础因子主要是地形坡度、地质构造、地面高程、岩体、植被、水系和坡形，诱发因：于主要是大气降水、人类工程活动和地震。大气降水是变化频繁的敏感因子。通过分析崂山区日降水量、持续累计降水量与地质环境条件、地质灾害发生频率、发生时间的关系，结合国内其他地区的分析结论，初步选定崂山区地质灾害预报预警降水量临界值，在此基础上建立了崂山区地质灾害预报预警信息系统，并以图形和表格两种形式在网上对外发布成功。通过回访调查，预报基本准确，服务效果明显，在很大程度上减轻和避免了灾害损失，有效地保护了人民生命财产的安全，促进了经济、社会的持续、稳定、健康发展。     

Flood forecasts based on multi-model ensemble precipitation forecasting using a coupled atmospheric-hydrological modeling system

The recent improvement of numerical weather prediction (NWP) models has a strong potential for extending the lead time of precipitation and subsequent flooding. However, uncertainties inherent in precipitation outputs from NWP models are propagated into hydrological forecasts and can also be magnified by the scaling process, contributing considerable uncertainties to flood forecasts. In order to address uncertainties in flood forecasting based on single-model precipitation forecasting, a coupled atmospheric-hydrological modeling system based on multi-model ensemble precipitation forecasting is implemented in a configuration for two episodes of intense precipitation affecting the Wangjiaba sub-region in Huaihe River Basin, China. The present study aimed at comparing high-resolution limited-area meteorological model Canadian regional mesoscale compressible community model (MC2) with the multiple linear regression integrated forecast (MLRF), covering short and medium range. The former is a single-model approach; while the latter one is based on NWP models [(MC2, global environmental multiscale model (GEM), T213L31 global spectral model (T213)] integrating by a multiple linear regression method. Both MC2 and MLRF are coupled with Chinese National Flood Forecasting System (NFFS), MC2-NFFS and MLRF-NFFS, to simulate the discharge of the Wangjiaba sub-basin. The evaluation of the flood forecasts is performed both from a meteorological perspective and in terms of discharge prediction. The encouraging results obtained in this study demonstrate that the coupled system based on multi-model ensemble precipitation forecasting has a promising potential of increasing discharge accuracy and modeling stability in terms of precipitation amount and timing, along with reducing uncertainties in flood forecasts and models. Moreover, the precipitation distribution of MC2 is more problematic in finer temporal and spatial scales, even for the high resolution simulation, which requests further research on storm-scale data assimilation, sub-grid-scale parameterization of clouds and other small-scale atmospheric dynamics.     

Evaluation of the weather research and forecasting (WRF) model over Guyana

In the present study, diagnostic studies were undertaken using station-based rainfall data sets of selected stations of Guyana to understand the variability of rainfall. The multidecadal variation in rainfall of coastal station Georgetown and inland station Timehri has shown that the rainfall variability was less during the May–July (20–30%) of primary wet season compared to the December--January (60–70%) of second wet season. The rainfall analysis of Georgetown based on data series from 1916 to 2007 shows that El Niño/La Niña has direct relation with monthly mean rainfall of Guyana. The impact is more predominant during the second wet season December--January. A high-resolution Weather Research and Forecasting model was made operational to generate real-time forecasts up to 84 h based on 00 UTC global forecast system (GFS), NCEP initial condition. The model real-time rainfall forecast during July 2010 evaluation has shown a reasonable skill of the forecast model in predicting the heavy rainfall events and major circulation features for day-to-day operational forecast guidance. In addition to the operational experimental forecast, as part of model validation, a few sensitivity experiments are also conducted with the combination of two cloud cumulus (Kain--Fritsch (KF) and Betts–Miller–Janjic (BMJ)) and three microphysical schemes (Ferrier et al. WSM-3 simple ice scheme and Lin et al.) for heavy rainfall event occurred during 28–30 May 2010 over coastal Guyana and tropical Hurricane ‘EARL’ formed during 25 August–04 September 2010 over east Caribbean Sea. It was observed that there are major differences in the simulations of heavy rainfall event among the cumulus schemes, in spite of using the same initial and boundary conditions and model configuration. Overall, it was observed that the combination of BMJ and WSM-3 has shown qualitatively close to the observed heavy rainfall event even though the predicted amounts are less. In the case of tropical Hurricane ‘EARL’, the forecast track in all the six experiments based on 00 UTC of 28 August 2010 initial conditions for the forecast up to 84 h has shown that the combination of KF cumulus and Ferrier microphysics scheme has shown less track errors compared to other combinations. The overall average position errors for all the six experiments taken together work out to 103 km in 24, 199 km in 48, 197 km in 72 and 174 km in 84 h.     

Solar shield: forecasting and mitigating space weather effects on high-voltage power transmission systems

In this paper, central elements of the Solar Shield project, launched to design and establish an experimental system capable of forecasting the space weather effects on high-voltage power transmission system, are described. It will be shown how Sun–Earth system data and models hosted at the Community Coordinated Modeling Center (CCMC) are used to generate two-level magnetohydrodynamics-based forecasts providing 1–2 day and 30–60 min lead-times. The Electric Power Research Institute (EPRI) represents the end-user, the power transmission industry, in the project. EPRI integrates the forecast products to an online display tool providing information about space weather conditions to the member power utilities. EPRI also evaluates the economic impacts of severe storms on power transmission systems. The economic analysis will quantify the economic value of the generated forecasting system. The first version of the two-level forecasting system is currently running in real-time at CCMC. An initial analysis of the system’s capabilities has been completed, and further analysis is being carried out to optimize the performance of the system. Although the initial results are encouraging, definite conclusions about system’s performance can be given only after more extensive analysis, and implementation of an automatic evaluation process using forecasted and observed geomagnetically induced currents from different nodes of the North American power transmission system. The final output of the Solar Shield will be a recommendation for an optimal forecasting system that may be transitioned into space weather operations.     

A fuzzy neural network bagging ensemble forecasting model for 72-h forecast of low-temperature chilling injury

Natural Hazards - On the basis of the daily temperature and precipitation data of Guangxi and the NCEP/NCAR reanalysis data and forecast field data, the paper aims to determine the significant...     

Modeling the Contemporary Stress Field and Deformation Pattern of Eastern Mediterranean

The contemporary stress field in the earth's crust is important and provides insights into mechanisms that drive plate motions.In this study,elastic plane stress finite element modeling incorporating realistic rock parameters was used to calculate the stress field,displacement field,and deformation of the plate interactions in the eastern Mediterranean.Modeled stress data for the African-Arabian-Anatolian plate interactions with fixed European platform correlate well with observed contemporary stress indica...     

Spatial variations of fundamental seismotectonic parameters for the earthquake occurrences in the Eastern Mediterranean and Caucasus

Natural Hazards - In this study, a comprehensive statistical analysis was made for different parts of the world. For this purpose, fundamental seismotectonic earthquake parameters such as b-value,...