安康水电站精细化降水预报的检验

降水精细化数值预报模式的发展是开展精细化降水预报业务的理想途径,而模式本地化中的误差评估是当前开展业务应用的重要环节。基于此,运用误差分析、晴雨预报准确率、降水TS评分方法评估陕西精细化数值预报攻关团队提供的2016年5月1日~9月30日安康水电站降水预报。结果表明：随着降水时效的增长,降水的预报准确率呈减小趋势;大雨以上的降水过程预报较好且未出现漏报,但量值与实况有差异,预报值小于实况值;20时起报的预报准确率大于08时起报的准确率且夜间的高于白天;降水日数多的月份TS评分预报准确率高于降水日数少的月份。比较安康和石泉的结果发现,安康的预报准确率明显优于石泉,主要原因是安康降水日数比石泉多,且大的降水过程比石泉少。逐1 h、3 h的72 h以内的降水预报可以为安康水电厂水利调度提供参考。     

Trend analysis of major hydroclimatic variables in the Langat River basin,Malaysia

Trend analyses of monthly, seasonal and annual rainfall, air temperature, and streamflow were performed using Mann‐Kendall test within the Langat River basin to identify gradual trends and abrupt shifts for 1980 − 2010. Annual rainfall showed an increasing trend in upstream flow, a combination of decreasing and increasing trends in middle stream flow, and a decreasing trend in downstream flow. Monthly rainfall in most months displayed an insignificant increasing trend upstream. Stations with significant increasing trends showed larger trends in summer than those of other seasons. However, they were similar to the trends observed in annual rainfall. Annual minimum air temperature showed a significant decreasing trend upstream and significant increasing trends in the middle stream and downstream areas. Annual maximum air temperature portrayed increasing trends in both upstream and middle stream areas, and a decreasing trend for the downstream area. Both monthly and seasonal maximum air temperatures exhibited an increasing trend midstream, whereas they demonstrated trends of both decreasing and/or increasing temperatures at upstream and downstream areas. Annual streamflow in upper, middle and lower catchment areas exhibited significant increasing trend at the rates of 0.036, 0.023 and 0.001 × 10³ m³/y at α = 0.01, respectively. Seasonal streamflow in the upstream, midstream and downstream areas displayed an increasing trend for spring (0.55, 0.33 and 0.013 m³/y respectively) and summer (0.51, 0.37, 0.018 m³/y respectively). The greatest magnitude of increased streamflow occurred in the spring (0.54 m³/y). Significant increasing trends of monthly streamflow were noticed in January and August, but insignificant trends were found in May, September and November at all stations. Annual streamflow records at the outlet of the basin were positively correlated with the annual rainfall variable. This study concludes that the climate of the Langat River basin has been getting wetter and warmer during 1980‐2010.     

Can MODIS Detect Trends in Aerosol Optical Depth over Land?

The Moderate Resolution Imaging Spectroradiometer(MODIS) sensor onboard NASA's Aqua satellite has been collecting valuable data about the Earth system for more than 14 years, and one of the benefits of this is that it has made it possible to detect the long-term variation in aerosol loading across the globe. However, the long-term aerosol optical depth(AOD)trends derived from MODIS need careful validation and assessment, especially over land. Using AOD products with at least 70 months' worth of measurements collected during 2002–15 at 53 Aerosol Robotic Network(AERONET) sites over land,Mann–Kendall(MK) trends in AOD were derived and taken as the ground truth data for evaluating the corresponding results from MODIS onboard Aqua. The results showed that the AERONET AOD trends over all sites in Europe and North America, as well as most sites in Africa and Asia, can be reproduced by MODIS/Aqua. However, disagreement in AOD trends between MODIS and AERONET was found at a few sites in Australia and South America. The AOD trends calculated from AERONET instantaneous data at the MODIS overpass times were consistent with those from AERONET daily data, which suggests that the AOD trends derived from satellite measurements of 1–2 overpasses may be representative of those from daily measurements.     

检验全球数值预报模式的相似度等指标

本文依照泛函形式并考虑了球面经纬网格的特点,定义了用于全球数值模式效果检验的指标:距离、距平相似度和倾向相似度,给出了相应的计算方法,并以全球WRF模式为例,检验了该模式的中期预报效果。所得结论如下:指标距离、距平相似度和倾向相似度物理意义明确,易于理论分析,考虑了球面经纬网格的特点,检验准确度高,具有普适性,能方便应用于球面经纬网格输出的数值模式检验。指标距离、距平相似度的检验结果分别与传统检验指标均方根误差、距平相关系数相一致,该指标还可直接用于向量场(如风场)的整体检验。本文的全球WRF模式所做的检验表明,对本文个例,该模式的全球500 hPa中期天气形势预报在第7 d及之内皆可用,5 d及之内预报效果更佳。     

衡阳风变化及风能蕴藏量评估

利用衡阳9站1970—2016年测风数据,通过气候倾向率分析风速年、年代际变化,M-K检验风速突变年份,运用有效风能密度评估各区域风能蕴藏量,其结论如下:衡阳风速总体呈下降趋势,衡山减少最明显,风速减少极显著区域未出现突变;低海拔区风速集中在0～3. 4 m/s(85. 8%),1991—2016年风频两极分化,低速及高速区增多,中间出现断层。南岳山风速范围广,2005—2016年强风频区有缺失,主风频在3～5区间;2010年全面采用高灵敏度自动测风仪,低海拔区静风迅速减少;按照有效风能密度定义,南岳山风能丰富,低海拔区未达到可利用标准。     

一种卫星EIRP自动测试方法

以往在测试EIRP值时一般采用人工测试的方法,这种测试模式不仅效率低,有时还会因人工操作影响测试结果准确性。本文提供了一种EIRP的自动化测试方法,通过一台上位机对相关设备进行自动数据采集并计算出卫星EIRP值,避免了传统测试方法的人工误差,具有高效性和实时性等特点。以FY3C532轨EIRP的测试为例,简要阐述这种自动化测试方法的测试过程。     

中国土壤湿度的时空变化特征

基于中国155个农业气象观测站1981-2010年逐旬土壤湿度资料,分析了全国和12个气候区域0~50 cm逐层的土壤湿度时空分布规律,采用趋势分析和Cramér-von Mises（CVM）方法探究了土壤湿度的变化趋势及突变性。结果表明：西南、江淮、东北、江南、江汉、黄淮和华南地区各层土壤湿度均高于全国平均值,内蒙古地区最低;随着深度增加,西南地区土壤湿度增加最明显,仅青藏高原地区土壤湿度减小。不同区域0~50 cm各层土壤湿度年变化和季节变化差异明显,并具有阶段性特征,大部地区深层土壤湿度高于浅层;总体上,新疆、华南、华北、青藏高原、东北、黄淮地区1981-2010年土壤湿度减小趋势显著,其中新疆地区减小最为明显。除江淮地区外,各区域土壤湿度均存在较为明显的年际差异,突变时段主要集中在20世纪80年代后期至90年代初期、90年代后期两个时间段。     

A New Method of Significance Testing for Correlation-Coefficient Fields and Its Application

Correlation-coefficient fields are widely used in short-term climate prediction research. The most frequently used significance test method for the correlation-coefficient field was proposed by Livezey, in which the number of significantcorrelation lattice(station) points on the correlation coherence map is used as the statistic. However, the method is based on two assumptions:(1) the spatial distribution of the lattice(station) points is uniform;and(2) there is no correlation between the physical quantities in the correlation-coefficient field. However, in reality, the above two assumptions are not valid.Therefore, we designed a more reasonable method for significance testing of the correlation-coefficient field. Specifically, a new statistic, the significant-correlation area, is introduced to eliminate the inhomogeneity of the grid(station)-point distribution, and an empirical Monte Carlo method is employed to eliminate the spatial correlation of the matrix.Subsequently, the new significance test was used for simultaneous correlation-coefficient fields between intensities of the atmospheric activity center in the Northern Hemisphere and temperature/precipitation in China. The results show that the new method is more reasonable than the Livezey method.     

两种显著性检验方法在海洋大数据序列主成分分析中的应用

介绍海洋大数据序列主成分分析的两种显著性检验方法,采用该两种方法可以辨别具有真实意义的主成分模与代表随机噪声信号的模态。此二法均能很好地应用于大数据序列主成分模的显著性检验。在进行海洋大数据序列时-空变化主成分分析中,为尽可能减少或避免数据中随机噪声的影响,建议对主成分模进行显著性检验。     

Full scale decay test of a tanker: field data and theoretical analysis

This paper presents results from a full scale decay test made with a tanker in a relatively protected area in the Brazilian coast. In at least two tests the environmental loads (wind, waves and current) were very small and the time history of the surge motion was well behaved, making it possible to check some proposed models for the damping in the hull and mooring lines. Field data seem to confirm that the damping is indeed of the fluid viscosity type and the theoretical models are able to recover roughly 75% of the observed damping, the energy dissipation in the mooring lines being, by far, the major contribution. The remaining 25% are likely due to non modeled effects, such as the environment influence, which although small and not measured certainly exists, and to the friction between the mooring lines and the seabed.