STUDY OF THE MODIFICATION OF MULTI-MODEL ENSEMBLE SCHEMES FOR TROPICAL CYCLONE FORECASTS     

张涵斌  智协飞  陈静  王亚男  王轶 《热带气象学报(英文版)》2015,21(4):389-399

This study investigates multi-model ensemble forecasts of track and intensity of tropical cyclones over the western Pacific, based on forecast outputs from the China Meteorological Administration, European Centre for Medium-Range Weather Forecasts, Japan Meteorological Agency and National Centers for Environmental Prediction in the THORPEX Interactive Grand Global Ensemble (TIGGE) datasets. The multi-model ensemble schemes, namely the bias-removed ensemble mean (BREM) and superensemble (SUP), are compared with the ensemble mean (EMN) and single-model forecasts. Moreover, a new model bias estimation scheme is investigated and applied to the BREM and SUP schemes. The results showed that, compared with single-model forecasts and EMN, the multi-model ensembles of the BREM and SUP schemes can have smaller errors in most cases. However, there were also circumstances where BREM was less skillful than EMN, indicating that using a time-averaged error as model bias is not optimal. A new model bias estimation scheme of the biweight mean is introduced. Through minimizing the negative influence of singular errors, this scheme can obtain a more accurate model bias estimation and improve the BREM forecast skill. The application of the biweight mean in the bias calculation of SUP also resulted in improved skill. The results indicate that the modification of multi-model ensemble schemes through this bias estimation method is feasible.  相似文献   

气溶胶对雷暴云起电以及闪电发生率影响的数值模拟   总被引：5，自引：1，他引：4  

师正  谭涌波  唐慧强  杨忆  彭琳  郭秀峰  陈浩然 《大气科学》2015,39(5):941-952

本文利用二维耦合气溶胶模块的雷暴云起电模式,结合一次南京雷暴个例,进行250 m分辨率雷暴云起电模拟实验,探讨了气溶胶浓度对雷暴云空间电荷分布以及闪电发生率的影响。在这个气溶胶模块中,假定一个三模态的气溶胶对数分布,考虑了气溶胶活化过程。结果显示:(1)随着气溶胶浓度增大,雷暴云电荷结构保持为三极型。(2)当气溶胶浓度从50 cm-3增加至1000 cm-3时,水成物粒子浓度上升,雷暴云电荷量和闪电发生率增加明显。(3)气溶胶浓度在1000~3000 cm-3范围时,云水竞争限制了冰晶的增长,导致雷暴云上部主正电荷堆电荷量降低。云滴和霰粒子浓度缓慢上升促进中部主负电荷堆和底部次正电荷堆电荷量继续增大。闪电发生率保持稳定。(4)当气溶胶浓度大于3000 cm-3时,水成物粒子浓度稳定,云内的电荷量以及闪电发生率保持为一定量级。  相似文献   

气候变化对中国农业旱灾损失率的影响及其南北区域差异性   总被引：4，自引：1，他引：3  

张强  韩兰英  郝小翠  韩涛  贾建英  林婧婧 《气象学报》2015,73(6):1092-1103

在全球变暖背景下,干旱灾害对中国农业生产的影响日益严重,然而由于旱灾损失的复杂性及其显著的区域差异,至今对中国农业旱灾损失规律及其影响机制的认识十分有限。文中利用1961年以来中国农业干旱灾害的灾情资料和常规气象资料,系统分析了近50年来中国农业干旱灾害不同受灾强度分布比率和综合损失率等指标的变化趋势及其在北方和南方的区域差异,研究了20世纪90年代的气温突变对农业旱灾损失率的影响特征,探讨了农业旱灾综合损失率对气温和降水等气候要素变化的依赖关系及其在气候空间的分布特征。结果发现,在气候变化背景下,近50年来中国农业旱灾综合损失率平均每10 a约增加0.5%,风险明显增大。而且,北方综合损失率每10 a约增加0.6%,高出南方1倍,风险增大的速度明显比南方快;北方农业旱灾几乎在很宽松的气温条件下就可以发生,而南方更多发生在气温较高的年份。并且,在气温突变后,变化趋势明显加剧,全中国综合损失率约增加了0.9%,风险明显增高;而且北方综合损失率的增值高达1.8%,是南方的4倍还多,气候突变对北方农业旱灾风险的影响明显比南方更凸出。综合损失率在北方对降水变化的响应要更敏感,而在南方对气温变化的响应更敏感。同时,关键影响期降水对综合损失率的影响比全年降水影响更显著;北方的关键影响期作用比南方更凸出。这些新的科学认识对中国农业旱灾防御具有重要意义。  相似文献   

A diagnostic analysis on the effect of the residual layer in convective boundary layer development near Mongolia using 20th century reanalysis data   总被引：1，自引：0，他引：1  

Bo Han  Cailing Zhao  Shihua Lü  Xin Wang 《大气科学进展》2015,32(6):807-820

Although the residual layer has already been noted in the classical diurnal cycle of the atmospheric boundary layer,its effect on the development of the convective boundary layer has not been well studied. In this study, based on 3-hourly20 th century reanalysis data, the residual layer is considered as a common layer capping the convective boundary layer. It is identified daily by investigating the development of the convective boundary layer. The region of interest is bounded by(30°–60° N, 80°–120° E), where a residual layer deeper than 2000 m has been reported using radiosondes. The lapse rate and wind shear within the residual layer are compared with the surface sensible heat flux by investigating their climatological means, interannual variations and daily variations. The lapse rate of the residual layer and the convective boundary layer depth correspond well in their seasonal variations and climatological mean patterns. On the interannual scale, the correlation coefficient between their regional averaged(40°–50°N, 90°–110° E) variations is higher than that between the surface sensible heat flux and convective boundary layer depth. On the daily scale, the correlation between the lapse rate and the convective boundary layer depth in most months is still statistically significant during 1970–2012. Therefore, we suggest that the existence of a deep neutral residual layer is crucial to the formation of a deep convective boundary layer near the Mongolian regions.  相似文献   

An experimental study on major element release from the sediments in the Changjiang (Yangtze River) Estuary     

Guo  Yanwei  Yang  Shouye 《中国海洋大学学报(英文版)》2015,14(3):417-424

With the enhanced warming and acidification of global ocean, whether and to what extent the naturally-weathered fluvial sediment into the sea can release elements and thus influence the geochemical pro...  相似文献   

利用高分影像和珞珈一号数据进行住房空置率高精度空间估算     

张栋  李德平  周亮  黄金侠  高航  王嘉丞  马宇 《测绘通报》2021,(1):41-46,52

本文主要利用珞珈一号夜间灯光数据和高分遥感影像数据,提出了一种对研究区按建成区高层区、建成区低层区和非建成区住房进行空置率分区块估算的方法,采用夜晚实地记录的方法对估算结果进行精度检验,并通过LISA聚集图分析其空间聚集情况。表明结果：①研究区整体住房空置率为17.88%,均方根误差为0.14,其中非建成区的住房空置率整体上要高于建成区,而满置率却低于建成区;②研究区住房空置率呈高高集聚和低低集聚两种空间集聚特征,为进一步大范围了解农村地区住房情况及整体的空间分布规律提供了参考。  相似文献   

不同截止高度角下BDS-3SPP精度分析     

朱玉香  陈永贵  安春华 《测绘通报》2021,(3):23-27

针对卫星可见数与历元可用率较低情况下的BDS-3定位性能,本文基于MEGX跟踪站BDS-3与GPS实测数据,分析了不同高度角（10°、20°、30°、40°）下BDS-3卫星B1I、B1C、B2a、B3I,以及GPS系统L1频率的单点定位（SPP）精度。研究发现,BDS-3平均卫星可见数与卫星空间几何构型优于GPS,且随着高度角的增加呈线性变化。BDS-3的4个频率的SPP精度随着高度角的增加呈先增加后降低的趋势,高度角为20°时,定位精度最高,高度角达到40°时,定位精度最低,且历元可用率也最低;但B1I和B3I历元可用率仍大于90%,而B1C和B2a历元可用率大于70%;不论是SPP定位精度还是历元可用率,均优于GPS系统L1频率。  相似文献   

一种多因子加权平均温度模型的构建方法     

李得宴  杨维芳  高志钰  蒋玉祥  李蓉蓉 《测绘科学》2021,46(3):73-79

针对在地基GNSS水汽反演的过程中,天顶湿延迟转换为大气可降水量时如何建立精确的大气加权平均温度(Tm)模型的问题,该文在建立Tm模型前全面考虑了对Tm有显著影响的变量并选择最优回归子集。但分析发现,最优回归子集中各变量之间存在较强的相关性,这将会导致变量之间存在多重共线性,从而影响模型的稳定性和可靠性。选择2013—2015年相关气象数据作为变量并应用岭回归的方法削弱变量之间的多重共线性,建立稳定的多因子Tm回归模型。并利用该模型分别预测2016年1—12月、2019年1—7月的Tm,均方根误差分别为2.3 K和2.0 K,预测精度较高,这将为高精度的水汽反演奠定较好的数据基础。  相似文献   

Impact of different sampling rates on precise point positioning performance using online processing service     

Serdar Erol  Reha Metin Alkan  ?.Murat Ozulu  Veli Il?i 《地球空间信息科学学报》2021,24(2):302-312

In this study, the effect of different sampling rates (i.e. observation recording interval) on the Precise Point Positioning (PPP) solutions in terms of accuracy was investigated. For this purpose, a field test was carried out in ?orum province, Turkey, on 11 September 2019. Within this context, a Geodetic Point (GP) was established and precisely coordinated. A static GNSS measurement was occupied on the GP for about 4-hour time at 0.10 second (s)/10 Hz measurement intervals with the Trimble R10 geodetic grade GNSS receiver. The original observation file was converted to RINEX format and then decimated into the different data sampling rates as 0.2 s, 0.5 s, 1 s, 5 s, 10 s, 30 s, 60 s, and 120 s. All these RINEX observation files were submitted to the Canadian Spatial Reference System-Precise Point Positioning (CSRS-PPP) online processing service the day after the data collection date by choosing both static and kinematic processing options. In this way, PPP-derived static coordinates, and the kinematic coordinates of each measurement epoch were calculated. The PPP-derived coordinates obtained from each decimated sampling intervals were compared to known coordinates of the GP for northing, easting, 2D position, and height components. According to the static and kinematic processing results, high data sampling rates did not change the PPP solutions in terms of accuracy when compared to the results obtained using lower sampling rates. The results of this study imply that it was not necessary to collect GNSS data with high-rate intervals for many surveying projects requiring cm-level accuracy.  相似文献   

地层渗透性对岩石强度及机械钻速影响因素分析     

杨谋  孟英峰  李皋  李永杰  徐翔  唐思洪  孙敏 《地质科技情报》2011,30(3):127-131

分析了地层渗透性对井底围压及破岩效率产生的影响,并对地层渗透性进行了分类,在此基础上建立了围压下岩石强度模型;基于压持效率制约了井底净化环境,修正与完善了不同地层渗透性的机械钻速模型,确定了各项参数.应用聚类分析中最优分段法对测井参数与录井参数进行了分类处理并编程获得了单轴下和围压下岩石强度剖面及机械钻速剖面,分别选取...  相似文献