基于短时临近降水集合预报的中小河流洪水预报研究

为了延长中小河流洪水预报预见期,建立了基于短时临近精细化网格降水集合预报的中小河流洪水预报模型.模型采用百分位映射订正技术,发展数值模式降水预报场与实况场映射关系,结合Bayesian模型,构建基于GRAPES-3KM模式和Time-Lag-Ensemble融合技术的短时临近降水集合预报(最优集成、最大(95％分位数)...     

Development of typhoon driven wave nowcasting model in Southeast China Sea

Using optimal interpolation data assimilation of observed wave spectrum around Northeast coast of Taiwan Island, the typhoon driven wave nowcasting model in Southeast China Sea is setup. The SWAN (simulating waves nearshore) model is used to calculate wave field and the input wind field is the QSCAT/NCEP (Quick Scatterometer/National Centers for Environmental Prediction) data. The two-dimensional wavelet transform is applied to analyze the X-band radar image of nearshore wave field and it reveals that the observed wave spectrum has shoaling characteristics in frequency domain. The reverse calculation approach of wave spectrum in deep water is proposed and validated with experimental tests. The two-dimensional digital low-pass filter is used to obtain the initialization wave field. Wave data during Typhoon Sinlaku is used to calibrate the data assimilation parameters and test the reverse calculation approach. Data assimilation corrects the significant wave height and the low frequency spectra energy evidently at Beishuang Station along Fujian Province coast, where the entire assimilation indexes are positive in verification moments. The nowcasting wave field shows that the present model can obtain more accurate wave predictions for coastal and ocean engineering in Southeast China Sea.     

The Importance of Being Timely

Policymakers want to know about real‐time economy performance. However, closely watched macroeconomic time series produced by national statistics offices are published infrequently, with a time lag and subject to revision. Such issues create uncertainty in tracking economic developments, a by‐product of which is to raise the value of business and consumer surveys. Although providing less granularity than official data series, the surveys are released in a timelier manner and are subject to little revision. Using real‐time data sourced from the Deutsche Bundesbank, the OECD and the Office for National Statistics, an assessment of the role that the popular and widely used Purchasing Managers' Index (PMI) play in reducing forecasting errors in a simple ‘nowcasting’ framework is undertaken. The empirical exercise is conducted for five developed economies and also covers the period of the Great Recession. The conclusion is clear: timing matters. Copyright © 2015 John Wiley & Sons, Ltd.     

Nowcasting Business Cycles Using Toll Data

Nowcasting has been a challenge in the recent economic crisis. We introduce the Toll Index, a new monthly indicator for business cycle forecasting, and demonstrate its relevance using German data. The index measures the monthly transportation activity performed by heavy transport vehicles across the country and has highly desirable availability properties (insignificant revisions, short publication lags) as a result of the innovative technology underlying its data collection. It is coincident with production activity due to the prevalence of just‐in‐time delivery. The Toll Index is a good early indicator of production as measured, for instance, by the German Production Index, provided by the German Statistical Office, which is a well‐known leading indicator of the gross national product. The proposed new index is an excellent example of technological, innovation‐driven economic telemetry, which we suggest should be established more around the world. Copyright © 2011 John Wiley & Sons, Ltd.     

腐蚀方法在风暴自动识别中的应用

为了解决聚类过程中常碰到的虚假合并问题,针对对流风暴的特点,使用了一种特殊的腐蚀方法,即在执行腐蚀操作时考虑了风暴边缘的反射率因子的强弱分布,进行动态的卷积模板的设计,而不是始终使用一个固定的卷积模板。试验及评价的结果表明,这种方法能够成功地识别出风暴体的虚假合并,进而提高风暴体的正确识别率和预报评价指标。     

雷达测雨及临近预报在中小流域水文视角下的应用评估

本文选取了2012年“苏拉”、2014年“海贝思”、2016年“尼伯特”三场台风在梅溪流域引发的三场不同类型降雨过程,探究了雷达测雨及临近预报在中小流域水文预报中的应用前景。采用24h累积雨量相对误差RE、时空两个维度均方根误差与相应维度均值的比值m-RMSE、平均绝对误差RMAE和平均偏差RMB等指标,基于地面雨量站的观测值评估雷达测雨以及1h、2h、3h预见期的集合临近预报,结果表明：雷达测雨总体上与地面雨量站观测值较为接近,不同类型降雨的RE值均在3%左右;时空分布均匀的降雨,临近预报效果优于短历时降雨和强降雨的临近预报效果,且随着预见期的延长,时空分布均匀的降雨预报效果更稳定,短历时降雨和强降雨的预报精度下降明显。因此,高时空分辨率的雷达测雨及临近预报在中小流域水文预报中有较好的应用前景,但短历时降雨和强降雨还需进一步研究。     

Google's MIDAS Touch: Predicting UK Unemployment with Internet Search Data

Internet search data could be a useful source of information for policymakers when formulating decisions based on their understanding of the current economic environment. This paper builds on earlier literature via a structured value assessment of the data provided by Google Trends. This is done through two empirical exercises related to the forecasting of changes in UK unemployment. Firstly, economic intuition provides the basis for search term selection, with a resulting Google indicator tested alongside survey‐based variables in a traditional forecasting environment. Secondly, this environment is expanded into a pseudo‐time nowcasting framework which provides the backdrop for assessing the timing advantage that Google data have over surveys. The framework is underpinned by a MIDAS regression which allows, for the first time, the easy incorporation of Internet search data at its true sampling rate into a nowcast model for predicting unemployment. Copyright © 2016 John Wiley & Sons, Ltd.     

Statistic characteristics of severe convective storm during Warm-Season in the Beijing-Tianjin region and its vicinity

This study analyzed the climatological characteristics of severe convective storms in the Beijing and Tianjin region and its vicinity based on the Doppler radar data of Tanggu during May-August of 2003-2007. The climatological characteristics, e.g. storm area, volume, top height, max reflectivity, life time and motion, are analyzed. The results include： 75% of all storms in the Beijing-Tianjin region last no more than 30 minutes, and most storms have a volume less than 400 kin3; most storms move from southwest to northeast while the speed is between 10-30 km/h; the mean storm top height is about 6 km, but some strong convective storms can have a top height larger than 15 kin; finally, storm area and volume have a similar geographical distribution character showing increasing trends from west to east. Compared with the statistic results based on the conventional surface meteorological observations, the results based on the radar data can present not only 3D spatial statistic results of convective storms （e.g., volume and top height）, but also the quantitative climatological characteristics, such as the lifetime and speed distributions. These statistical results are useful for studying the climatic characteristics of convective storms in the Beijing-Tianjin region and its vicinity.