东亚地区气象参数卫星遥感反演理论和方法研究Ⅰ:ISPRM和SRRM

文中对10a来改进的同步物理反演方法(ISPRM)实践与发展进行了总结。在不违背先验信息和卫星测值之间独立的原则下,所做的改进都是针对这类非适定反演问题的欠定性(under-determinedness)进行的。由适定反演理论知道,正演是反演的基础,又是卫星辐射率测值输入和反演结果输出之间的桥梁。为了获得好的正演,就必须竭尽可能充分利用一切可以使用的先验信息,把非适定反演问题转化成适定的反演问题,从而通过Ridge回归或Bayes反演过程,把先验信息、理论模拟信息和卫星探测信息三者最佳地结合起来,以最大限度减少这类反演问题的欠定性对数值解的影响。     

2006年汛期北京地区中尺度数值业务降水预报检验

采用北京地区自动站逐小时观测降水资料对2006年汛期北京地区中尺度数值业务降水预报效果进行了客观检验,并针对2006年汛期的降水特点对模式的降水预报性能进行了初步的评估,着重对发生的28次降水过程按其主导的天气系统进行了分类,并对各个类型的降水预报进行了评分检验,根据检验结果分析了数值业务模式对于夏季不同天气系统导致的降水过程的预报能力,并且对不同分辨率的模式网格的预报性能进行了初步对比。     

ECMWF模式对东北半球气象要素场 预报能力的检验

利用ECMWF模式逐日分析场(0场)序列和7d预报场序列,使用气候学方法客观检验ECMWF模式对东北半球的预报能力,主要结果如下:1)模式对不同要素场的预报能力呈现出明显的季节性差异,夏季特别是7月预报能力最弱.2)总体来说,850 hPa温度场、500 hPa高度场与0场相关最好,850 hPa湿度场与0场相关最弱;随着预报时效的增加,预报能力总体减弱.3)大陆上温度场预报总体较0场偏高,而在赤道低纬地区偏低,模式对赤道附近温度场变率预报能力弱于中高纬地区,这一特征在其它要素预报中也有不同程度的体现.4) 500 hPa位势高度预报场与0场的差值表现出清楚的起源于里海并向东北传播经贝加尔湖、鄂霍次克海转向东南至日本东部海域的波列,这一现象在500 hPa风场差值图中也有清楚的表现.5)纬向风预报能力强于经向风,30°N附近存在纬向风与0场相关系数高值带.6)总体来说,模式对高层的预报能力优于低层,但模式对700 hPa风场的预报存在显著差异.     

CAPPS模式在石家庄市应用的效果检验

根据《气象部门空气质量预报质量考核和管理暂行办法》,对CAPPS系统在石家庄市空气质量预报中的应用效果进行检验,对CAPPS1.0和CAPPS2.0的预报能力和产生的误差进行了对比分析。结果表明:CAPPS2.0的整体预报水平高于CAPPS1.0,但其预报值多偏高于监测值,这是导致冬季首要污染物正确性评分偏低、夏季高污染预报能力偏低的主要原因。CAPPS系统对前日污染实况依赖性强,预报结果滞后,对高浓度污染日的预报准确率仅为13%,预报能力偏低。     

CUACE系统在乌鲁木齐空气质量预报中的效果检验

采用2013年12月1日—2014年2月28日空气质量观测数据,对CUACE系统在乌鲁木齐空气质量预报中的效果进行离线检验。结果表明,在污染物浓度和空气质量分指数方面,NO2的预报效果优于PM10和PM2.5,28 h预报时效的预报效果优于52 h预报时效;在首要污染物预报结果中,28 h预报时效的总体预报效果优于52 h,28 h预报时效中PM2.5预报正确率为65%;从空气质量等级的预报效果来看,28 h预报时效与52 h预报时效无明显差别,对NO2和PM10的预报准确率达到100%,对PM2.5三级预报准确率达到90%以上,对二、四级预报准确率在70%～80%之间,对五、六级重度污染预报值偏低两个级别或以上。     

2008年T213与德国降水数值预报产品对比检验分析

为了解各种数值预报的误差特点,更好地在预报过程中选择数值预报产品作为参考依据,将中国国家气象中心的T213降水预报和德国降水预报分别进行晴雨预报检验,对2008年5—8月期间东北地区降水资料进行对比分析。结果表明：两种模式24—120h预报正确率为60%—70%左右,随着预报时效的增加,正确率呈下降趋势,德国降水预报的正确率高于T213,两种预报漏报率均明显小于空报率,T213漏报率较低,为5%左右,德国降水预报空报率较低,为20%左右。对2008年4—6月出现东北冷涡过程的两种模式降水预报进行对比分析,发现德国降水预报正确率明显高于T213预报,对冷涡降水预报有一定的指示意义。     

2013年汛期华中区域业务数值模式降水预报检验

为充分了解华中区域中尺度业务数值预报模式更新为WRF后的预报性能,对该模式2013年汛期24 h和48 h的累积降水预报产品,采用TS评分、预报正确率、漏报率、空报率、偏差及ETS评分等统计量对其进行了较详细的评估。结果表明：从日平均降水率分布来看,24 h预报的降水中心位置和强度与实况更接近,48 h的预报明显偏大、偏强;汛期总体降水检验表明,该模式的降水预报以偏大为主,随着降水量级的增大,TS和ETS评分逐渐减小,且ETS评分逐渐靠近TS;逐月降水检验结果发现,该区域汛期月晴雨预报正确率与雨日率呈正相关;通过梅雨期WRF与GRAPES_Meso的预报对比检验可见,两个模式都表现出了较好的预报性能。值得指出的是,随着降水量级的增大,WRF模式降水预报优势逐渐显现。总的来说,该模式的降水预报产品具有一定的参考价值。     

“天气在线”网上气象站对郑州单点要素预报能力的检验

对“天气在线”网上气象站所预报的郑州市2004和2005年的汛期(6~8月)降水、最低气温、最高气温3项气象要素的准确率进行了检验与分析,结果表明:“天气在线”对郑州市一般降水的预报准确率具有参考价值,对中雨及以上量级的降水预报能力比较差,尤其是对单站暴雨预报能力更弱;对郑州单点的温度预报能力很强,特别是晴天的情况下,不论是最高温度、最低温度还是高温天气都有很高的预报准确率。     

Numerical simulation and land subsidence control for deep foundation pit dewatering of Longyang Road Station on Shanghai Metro Line 18

In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to reduce the drawdown and land subsidence outside pits. In dewatering design for confined water, factors including drawdown requirements, the thickness of aquifers, the depth of dewatering wells and the depth of cutoff curtains have to be considered comprehensively and numerical simulations are generally conducted for calculation and analysis. Longyang Road Station on Shanghai Metro Line 18 is taken as the case study subject in this paper, a groundwater seepage model is developed according to the on-site engineering geological conditions and hydrogeological conditions, the excavation depth of the foundation pit as well as the design depth of the enclosure, hydrogeological parameters are determined via the pumping test, and the foundation pit dewatering is simulated by means of the three-dimensional finite difference method, which produces numerical results that consistent with real monitoring data as to the groundwater table. Besides, the drawdown and the land subsidence both inside and outside the pit caused by foundation pit dewatering are calculated and analyzed for various curtain depths. This study reveals that the drawdown and the land subsidence change faster near the curtain with the increase in the curtain depth, and the gradient of drawdown and land subsidence changes dwindles beyond certain depths. In this project, the curtain depth of 47/49 m is adopted, and a drawdown-land subsidence verification test is completed given hanging curtains before the excavation. The result turns out that the real measurements basically match the calculation results from the numerical simulation, and by increasing the depth of curtains, the land subsidence resulting from dewatering is effectively controlled.     

Modeling diagnosis of suspended sediment transport in tidal estuarine system

A three-dimensional, time-dependent hydrodynamic and suspended sediment transport model was performed and applied to the Danshuei River estuarine system and adjacent coastal sea in northern Taiwan. The model was validated with observed time-series salinity in 2001, and with salinity and suspended sediment distributions in 2002. The predicted results quantitatively agreed with the measured data. A local turbidity maximum was found in the bottom water of the Kuan-Du station. The validated model then was conducted with no salinity gradient, no sediment supply from the sediment bed, wind stress, and different freshwater discharges from upstream boundaries to comprehend the influences on suspended sediment dynamics in the Danshuei River estuarine system. The results reveal that concentrations of the turbidity maximum simulated without salinity gradient are higher than those of the turbidity maximum simulated with salinity gradient at the Kuan-Du station. Without bottom resuspension process, the estuarine turbidity maximum zone at the Kuan-Du station vanishes. This suggests that bottom sediment resuspension is a very important sediment source to the formation of estuarine turbidity maximum. The wind stress with northeast and southwest directions may contribute to decrease the suspended sediment concentration. When the freshwater discharges increase at the upstream boundaries, the limits of salt intrusion pushes downriver toward river mouth. Suspended sediment concentrations increase at the upriver reaches in the Danshuei River to Tahan Stream, while decrease at Kuan-Du station.