含有开关参数化物理过程的模式变分资料同化的非光滑优化方法:几个理论问题   总被引：7，自引：0，他引：7  

Zhu Jiang  Masafumi Kamachi  Zhou Guangqing 《大气科学进展》2002,19(3):405-424

时间、空间上离散的模式如果含有带开关的参数化物理过程，某些对应的变分同化问题可以看成为非光滑优化问题。本系统地讨论了与此相关的几个理论问题。首先，利用次梯度这个非光滑优化中的基本概念可以对通常的伴随方程的解进行清楚的解释和定义。利用一个带对流调整的多层扩散模式，演示了通常的伴随方程的解在奇异点处不是由代价函数的Gateaux导数构成，而是代价函数的一个次梯度。其次，在非光滑优化的框架下对现有的解决这类问题的方法进行了评述。这些方法包括：（1）利用光滑优化方法和通常的伴随模式，并且讨论了这个方法的收敛条件；（2）正则化方法。这个方法是把模式中不光滑的项用光滑的项近似，以把问题变为光滑优化问题。（3）次梯度方法。这个方法利用通常的伴随模式来计算一个次梯度，是收敛的算法，不过收敛速度很慢。（4）非光滑优化中的Bundle方法。这个方法比次梯度方法收敛得快，不过需要利用所有的次梯度信息。由于计算所有的次梯度十分困难，现有的Bundle方法大都进行了一些改变，仅需要用户能够计算出一个次梯度。不过这个改变是无奈的，多个次梯度的信息可以提高Bundle方法的效率。本最主要的工作是提出了集值伴随方程的概念。集值伴随模式可以在奇异点处计算出所有支撑次梯度，因此利用集值伴随方程有可能提出基于Bundle方法的更好算法。  相似文献   

分布式水文-土壤-植被模式的改进及气候水文Off-line模拟试验   总被引：12，自引：3，他引：12  

王守荣  黄荣辉  丁一汇  L.R.Leung  M.S.Wigmost  L.W.Vail 《气象学报》2002,60(3):290-300

文中对引进的高分辨率 (94 2 .5m× 94 2 .5m)分布式水文 土壤 植被模式 (DHSVM) ,针对海、滦河流域的特点进行了改进 ,主要包括 :(1)改变蒸散发模拟方法 ,用改进的Penman Monteith模式模拟海滦河流域的蒸发 ,较好地模拟出 1a内的两个峰值 ,最大值出现在 4～ 6月 ,次大值出现在 7～ 8月 ;(2 )改变水文模式结构 ,用多站点气候观测资料内插到模式网格点 ,充分实现了分布式水文模拟 ;(3)发展新的水文、植被、土壤参数化方案 ,对 33个参数分区计算和确定 ,并重点对土壤孔隙度 φ、土壤蓄水能力θfc、叶面指数LAI、随机阻抗γs 等 11个参数进行调试和修订 ,提高了水文模拟精度。用改进的DHSVM模式分别对滦河、桑干河流域蒸散发、地下水位、土壤湿度、土壤水下渗、产流、汇流与径流等水文过程进行Off line模拟试验 ,模拟结果与实测值一致性较好 ,滦河流域 1979～ 1991年、桑干河流域 1979～ 1987年水文模拟效率系数分别为 0 .89和 0 .82 ,均高于国内其他相关研究  相似文献   

由大尺度观测提取中尺度信息的可能性研究     

邱崇践  张述文 《气象学报》2002,60(5):538-543

利用浅水方程模式和变分四维同化方法对由大尺度观测提取中尺度信息的可能性进行了模拟试验研究。试验的初始场是在平直气流上叠加一个半径为 5倍格距的圆形涡旋。分别设定观测点的间距是 5 ,7和 9倍格距 ,观测的时间间隔分别是 1,2和 3h ,同化时间为 6h或 12h ,考察同化产生的初始场。试验结果是 :观测点的间距是 5倍格距时 ,由观测给出的分析场不能反映涡旋的基本特征 ,而在同化产生的初始场中 ,涡旋的基本结构清楚 ,但强度有所削弱。增加观测次数或者延长同化时间 ,可以改善同化的结果。对于移动较快的系统 ,同化的结果较好。当观测点的间距是 9倍格距时 ,同化的结果与分析场相比已无明显改进。  相似文献   

卫星亮温资料四维同化方案及其对"7·20"武汉特大暴雨的模拟试验   总被引：28，自引：0，他引：28       下载免费PDF全文

孟智勇  徐祥德  陈联寿 《大气科学》2002,26(5):663-676

作者首次把与云参数相关的云顶亮温(TBB)资料直接用于中尺度模式MM5V2的牛顿张驰逼近(nudging)四维同化过程,提出了一种通过分析场的nudging四维同化来确定云顶高度的方法,并利用1 h间隔的TBB-nudging方案成功地模拟了"7@20"武汉大暴雨过程.TBB-nudging试验的模拟结果表明对流层低层中尺度低涡和低空西南急流是"7@20"大暴雨的主要影响系统,这预示着把卫星遥感资料(例如TBB等)用于中尺度模式的同化过程有可能提高中尺度暴雨的预报能力.  相似文献   

中尺度模式的四维伴随同化系统及其同化试验     

李晓莉  沈桐立  孙麟平 《南京气象学院学报》2002,25(1):36-44

以中尺度模式MM4为基础，利用伴随码技术改进、完善了MM4伴随模式同化系统，并利用该系统进行了常规资料和非常规资料的伴随模式同化试验，例如加入了可降水量资料等。试验表明：在伴随模式同化系统中加入常规和非常规资料，可以改进初始场，从而改善预报场。  相似文献   

Scale effects of Hortonian overland flow and rainfall‐runoff dynamics: laboratory validation of a process‐based model     

T. J. Stomph  N. de Ridder  T. S. Steenhuis  N. C. Van de Giesen 《地球表面变化过程与地形》2002,27(8):847-855

Hortonian runoff was measured in the laboratory from uniform slopes of lengths of 1·5, 3·0, and 6·0 m for steady, high‐intensity rainstorms with durations of 1·0 to 7·5 min. A clear reduction in runoff per unit slope length was found as slope lengths were increased. This effect becomes more pronounced with decreasing storm duration. The runoff data were used to validate a simple process‐based model that combines the Philip‐two‐term infiltration equation with the kinematic wave overland flow principle. The predicted and experimental results agreed well. Laboratory findings were extrapolated with the aid of the model to slopes and rainfall durations similar to those found under West African conditions. The calculated reduction of runoff per unit length is similar to reported observations. Thus, this process‐based model can largely explain the phenomenon of runoff reduction with increasing slope length. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Geochemical Modelling as a Tool for Actinide Speciation during Anoxic Leaching Processes of Nuclear Fuel     

M. Amme 《Aquatic Geochemistry》2002,8(3):177-198

The behaviour of many radiotoxic elements, which are contained within spent nuclear fuel planned for direct disposal, is strongly dependent on the redox chemistry of the aqueous media present in the deep geological systems, where such disposal options are investigated. Especially actinide elements are known to be sensitive. The knowledge of the speciation of actinides in the case of a possible mobilisation by intruding groundwater is therefore crucial and part of the source term calculation of many countries' performance assessment procedures. In this study, the influence of redox conditions and complexant concentration in two selected groundwaters upon the species distribution of U and Pu is assessed by using the thermodynamic modeling code PHREEQC version 2.3. The modeled systems were derived from laboratory leaching experiments testing nuclear fuel dissolution. For the calculations, critically reviewed data for U and Pu complexation were used. The results show that under the conditions calculated, U and Pu are present mainly as U(VI) and Pu(IV). The presence of solid UO₂ substrate is supposed to change this distribution. The calculational use of different groundwaters as aqueous phase, implying a slightly different solution composition, affects U and Pu speciation: U species distribution is affected mainly by complexant concentration, Pu species are influenced by pH changes. A sensitivity study on Pu speciation is performed; constants changed within their confidence intervals were applied. The results are compared with experimental observations, and differences and possible expected effects during the dissolution of real, complex materials are discussed.  相似文献   

蒙脱石抗菌材料研究   总被引：6，自引：2，他引：6  

余志伟  王筱明  王霞 《矿物岩石》2003,23(4):15-17

以膨润土为原料，通过对提纯后的蒙脱石进行酸活化处理，扩大其孔层结构。制得具有高吸附性能的载体材料；并以银、铜、锌等3种金属氧化物为抗菌剂，采用化学吸附的方法，将抗菌剂离子引入到蒙脱石的孔层结构中，制得抗菌材料。并选择最常见的大肠杆菌进行杀菌实验，结果表明杀菌效果显著。  相似文献   

Carbon assimilation characteristics of plants in oasis-desert ecotone and their response to CO2 enrichment   总被引：2，自引：0，他引：2  

SU Peixi  CHEN Huaishun  AN Lizhe  LIU Xinmin 《中国科学D辑(英文版)》2004,47(Z1)

Six species of more than 20-year-old desert woody plants in the oasis-desert ecotone were selected for study. The results showed that: (1) in different growing seasons δ13 C values of assimilating organ varied between -14‰ and -16‰ for Haloxylon ammodendron (HA),-14‰ - -15‰ for Calligonum mongolicum (CM) and -25‰ - -28‰ for Caragana korshinskii (CK), Nitraria sphaerocarpa (NS) and Hedysarum scoparium (HS). (2) The net photosynthetic rate (Pn) of HA and CM was significantly higher than those of the other species. With the decrease in Pn for the six species, their intercellular CO2 concentration increased, but stomatal limitation value decreased under the intensive light. At the same time, the photochemical efficiency of PS Ⅱ dropped to different degrees. (3) The CO2 enrichment experiment demonstrated that, Pn of HA and CM increased to different extent under 450 μmol/mol, but their Pn reduced or approximated to the current condition under 650 μmol/mol. Under 450 μmol/mol the efficiency for solar energy utilization of CK and HS significantly reduced and under 650 μmol/mol their respiration rate exceeded photosynthesis rate. It can be concluded that HA and CM have some function of pathway for C4, but the other three species have the function for C3. The decline in their Pn is mainly caused by non-stomatal factors. HA, CM, CK and HS exhibited photoinhibition, which disappeared in a short time. This is a kind of positive readjustment to adapting to the desert environment. HA and CM can adapt to the high CO2 environment, but CKand HS cannot. With the rise in atmospheric CO2 concentration and climate warming, the latter two species in the oasis-desert ecotone may be gradually degraded or even disappear.  相似文献   

Determination of Secondary Organic Aerosol Products from the Photooxidation of Toluene and their Implications in Ambient PM2.5     

T. E. Kleindienst  T. S. Conver  C. D. McIver  E. O. Edney 《Journal of Atmospheric Chemistry》2004,47(1):79-100

A laboratory study was carried out to investigate the secondary organic aerosol products from photooxidation of the aromatic hydrocarbon toluene. The laboratory experiments consisted of irradiating toluene/propylene/NO_x/air mixtures in a smog chamber operated inthe dynamic mode and collecting submicron secondary organic aerosol samples through a sampling train that consisted of an XAD denuder and a Zefluor^TM filter. Oxidation products in the filter extracts were treated using O-(2,3,4,5,6,-pentafluorobenzyl)-hydroxylamine (PFBHA) to derivatize carbonyl groups followed by treatment with N,O-Bis(trimethylsilyl)-acetamide (BSTFA) to derivatize OH groups. The derivatized products were detected with a positive chemical ionization (CI) gas chromatography ion trap mass spectroscopy (GC-ITMS) system. The results of the GC-ITMS analyses were consistent with the previous studies that demonstrated the formation of multi-functional oxygenates. Denuder results showed that many of these same compounds were present in the gas, as well as, the particle phase. Moreover, evidence was found for a series of multifunctional acids produced as higher order oxidation products of the toluene/NO_x system. Products having nearly the same mass spectrumwere also found in the ambient environment using identical analytical techniques. These products having multiple acid and alcoholic-OH moieties have substantially lower volatility than previously reported SOA products of the toluene photooxidation and might serve as an indicator for aromatic oxidation in the ambient atmosphere.  相似文献