喀斯特流域降雨-径流人工神经网络模型结构分析及模拟

喀斯特流域降雨-径流响应是一个非线性过程,分析确定地下河流量过程的主要影响因子对喀斯特流域水文过程模拟具有重要意义。本文利用普定后寨河流域实测降雨、径流系列资料,采用神经网络权重分析法确定该流域的人工神经网络模型结构为两个隐含层、三个输入变量,该人工神经网络模型结构可以保持降雨-径流模拟的稳定性。模型经交叉训练与验证,训练期效率系数（NSC）达0.9以上,验证期NSC达0.88以上。说明神经网络权重分析法能够较好地确立预报因子与预报对象的关系,为喀斯特流域降雨-径流模拟提供一种有效的分析手段。      

不同微物理参数化方案对降雨数值模拟的影响试验——以北京为例

城市暴雨预报对防洪排涝具有重要意义。基于中尺度数值天气预报模型WRF,构建北京市暴雨模拟模型,采用13种微物理参数化方案,对2007年8月1日下午至8月2日凌晨的暴雨过程进行了模拟试验。结果表明,对该场降雨,Kessler方案模拟得到的面平均降雨量与实测值最接近;WSM5方案模拟得到的面平均降雨过程与实测过程吻合最好;累积降雨高值区域落区模拟和最大1h降雨强度模拟,Milbrandt方案表现最好;综合考虑降雨量、降雨过程、累积降雨高值区域落区范围和最大1h降雨强度指标,Milbrandt和Thompson方案表现最好。此外,相比单矩方案,采用多矩方案可能会提高对微物理过程的描述精度。研究结果对北京市暴雨预报具有一定参考意义。     

不同降水产品在长江流域的偏差校正研究

基于长江流域135个站点1983—2020年的月降水量观测数据,分别对ERA5-Land、PERSIANNCDR和MSWEP等三种降水产品进行了适用性评估,并对比使用了多种偏差校正方法来提高降水产品的观测精度。结果表明,MSWEP对于长江流域的降水模拟效果较好,空间相关系数高达0.91,相对偏差仅为1.64%;ERA5-Land则对长江流域降水高估严重,精度较差。经偏差校正处理后,三种降水产品的适用性均得到了不同程度的提升,尤其是ERA5-Land,KGE(Kling-Gupta Efficiency)指标值从校正前的0.72增加到了0.82。对比不同偏差校正方法的应用效果发现,线性缩放法和分段伽玛分布校正法在长江流域表现最优,且后者更加稳健。本研究可为降水产品及气候模式输出等的后处理工作提供指导。     

江苏省无资料山丘区洛阳河流域径流模拟方法探讨

近年来,无资料或资料缺乏地区汇流计算成为水文研究热点。基于地形参数的地貌瞬时单位线(GIUH)方法凭借其对历史降雨径流实测资料的不依赖性,已然成为径流模拟研究中被普遍采用且效果较好的方法之一。为探讨江苏省无资料山丘区的径流模拟方法,选取具有典型地形地貌特征的镇江通胜洛阳河小流域展开研究。根据地貌特征值等数据提取出该流域的地貌单位线,采用地貌单位线计算径流过程,利用2016、2017年汛期实测的4场洪水进行方法验证,将计算径流与实测数据进行对比分析,结果表明:基于地貌特征的地貌单位线法在该流域洪水模拟中具有较高精度,又因该流域于江苏省乃代表性区域,初步判定可将该方法推广至其他无资料山丘区流域。     

基于降雨类型直方图分析的降雨站点相似性研究

为研究降雨观测站点间的相似性,提出了基于单场降雨类型直方图分析的降雨站点相似性比较模型。首先提取降雨时间序列中的雨量项,经过数据预处理,选择和提取单场降雨特征,并将这些特征统计量进行数据标准化处理;采用基于Davies-Bouldin指数聚类有效性指数的K-means方法进行聚类,最后对聚类结果进行基于单场降雨的降雨类型直方图相似性分析。实验结果符合相关区域的站点相似性实际情况,表明该相似性模型是可靠的,具有较好的应用价值。     

鄂西恩施地区非饱和土降雨入渗规律

在分析鄂西恩施地区降雨特征的基础上,选取6组典型降雨条件,设计并进行了室内人工降雨土柱非饱和入渗试验。通过实测土体体积含水率,揭示了鄂西恩施地区非饱和土降雨入渗规律,获得了降雨入渗影响区体积含水率变化规律、入渗前锋运移规律以及降雨强度和历时对入渗的影响规律。通过GeoStudio软件对室内降雨试验进行了数值模拟,数值模拟结果与试验结果基本相同,进一步验证了降雨入渗规律。同时依据实测结果,分析了数值模拟的不足之处,为通过数值模拟方法研究非饱和土降雨入渗奠定了基础。     

生物滞留设施规模设计方法研究

研究提出了基于单场次降雨分析以及基于长系列降雨统计的生物滞留设施规模设计方法。针对国内市政排水设计一般采用设计重现期的概念,基于单场次降雨分析的规模设计方法用暴雨强度公式和雨型分配方法计算设计降雨过程,由设计降雨推算设施入流过程,用水量平衡法推算出流过程,用洪量削减率、洪峰削减率、洪峰延迟时间评估设计效果。基于长系列降雨统计的规模设计方法对长期日降雨量进行统计分析,得出不同降雨发生频率对应的设施入流量及处理量,用年径流总量削减率评估设计效果。     

降雨重现期及其用于滑坡概率分析的探讨

极端气候条件往往会诱发各种地质灾害,而降雨型滑坡的发生则与极值降雨关系密切。为了有效预防和控制汛期滑坡灾害的发生,定量评估滑坡灾害造成的人员与经济风险,讨论了汛期极值降雨条件下滑坡概率的分析方法。利用Gumbel极值分布理论,以三峡库区巴东县1990~2006年日降雨量为基础资料,采用统计分析方法,求取研究区在汛期(6月中旬至9月)最大一次连续降雨量、多日累积最大降雨量的极值及其分布曲线; 在此基础上,以研究区一个滑坡实例为对象,综合采用渗流模拟、稳定性分析和基于蒙特卡罗的滑坡概率分析方法,讨论了降雨极值及其重现期成果分别在降雨新生型滑坡和降雨复活型滑坡概率分析中的应用思路与方法。结果表明,随着重现期的增加,一次降雨过程的降雨量也增加; 随着降雨日数的增加,具有不同重现期降雨事件的累积降雨量均会增加,且重现期越长,累积降雨量值会越大; 降雨极值曲线分别应用于降雨新生型和降雨复活型滑坡概率分析的思路是可行并有效的。     

基于TRMM卫星雷达降雨的流域陆面水文过程

利用热带降雨观测计划(TRMM)卫星雷达降雨数据驱动分布式陆面水文模型,研究流域尺度陆面水文过程,评估该数据在水文模拟与预报等研究领域的性能。通过与实测雨量资料比较,验证TRMM卫星雷达降雨数据的质量。分别将TRMM卫星雷达降雨与观测降雨作为耦合模型的气象输入,模拟和研究淮河流域1998~2003年的陆面水文过程时空变化。结果表明,TRMM卫星雷达降雨数据能够很好地描述降雨的时空分布,利用TRMM降雨模拟的结果与利用观测降雨模拟的结果精度相当;模拟流量与实测资料基本吻合。卫星雷达降雨数据在陆面水文过程研究中具有广泛的应用前景。     

气象产品的广义联合偏差修正方法及其应用

卫星气象产品、气候模式预测数据通常与地面观测数据存在偏差,为保证数据的可靠性和合理性,需要对其进行偏差校正,但偏差校正过程往往受具体区域气象特征、方法本身假定等因素的影响,导致修正效果不佳。为此,本文提出一种广义联合偏差修正方法,相较于现有研究最常用的单变量QM修正方法以及固定多变量修正顺序的JBC修正方法,该方法充分考虑到流域尺度降水和气温双变量的时空相关性,并结合其对径流的主导作用对变量修正顺序进行动态调整,实现了QM法和JBC法的优势互补。在澜沧江-湄公河流域的应用表明：考虑降水、气温相关性可显著改善降水和温度极值的修正效果,尤其是5、6月份,修正后气象与实测数据的纳什系数提升了0.5以上;考虑气象要素的修正次序显著降低了修正后的降水和温度频率分布及均值偏差;利用修正后的气象数据驱动分布式水文模型时,部分月份的径流模拟精度提升了54.3%。     

东亚水循环中水稳定同位素的GCM模拟和相互比较

利用引入稳定同位素循环的ECHAM4、GISS E和HadCM3模式的模拟,对东亚降水中年平均δD和过量氘d的空间分布以及大气水线（MWL）进行了分析.根据模拟的空间分布,降水同位素在很大程度上反映不同气团的地理背景以及它们之间的相互作用,模拟结果很好地再现了由GNIP实测资料得到的降水稳定同位素的纬度效应、大陆效应和...     

大气环流模式在黄河流域的适用性评价

本文以国际上较流行的5个大气环流模式(HadCM3、GFDL、ECHAM4、CSIRO-Mk2以及CGCM2)对黄河流域1961～1990年温度和降水的模拟结果为基础,通过与该流域同期观测值比较,分析了各大气环流模式(GCM)在黄河流域的适用性.研究结果表明:HadCM3、GFDL两个模式对黄河流域温度的模拟结果较好;ECHAM4、HadCM3两个模式对黄河流域降水的模拟结果较好.5个大气环流模式对温度的模拟明显优于对降水的模拟.总体而言,英国的HadCM3模式在黄河流域的适用性最好,可为黄河流域水文水资源、水土流失对全球气候变化响应等相关研究,提供未来气候变化情景的借鉴.     

The relationship between the isotopic content of precipitation and the precipitation amount in tropical regions

General circulation models (GCMs) fitted with stable isotope schemes are widely used to interpret the isotope–climate relationship. However, previous studies have found that the spatiotemporal isotope/precipitation correlation simulated by GCMs is stronger and more widespread than the observed value. To understand the reason for this failure, we investigated the factors influencing the empirically well-known isotope/precipitation relationship, or precipitation amount effect, in the tropics using newly obtained daily precipitation isotope monitoring data over Asia. As in previous studies, we found an apparent correlation between the long-term monthly mean isotopic content and the corresponding precipitation amount (local precipitation) observed at sub-tropical island stations. Furthermore, on a monthly timescale, the isotopic variability of precipitation for these stations was more clearly related to the regional precipitation amount than to local precipitation. This correlation of isotopic content with the regional precipitation amount was observed at the equatorial (Maritime Continent) stations. For these stations, isotope/local precipitation relationships only appeared over longer timescales, with different regression line slopes at each station. However, at the coastal stations, there was a strong linear relationship between the monthly mean isotopic content and corresponding regional precipitation, and regression line slopes were spatially uniform. For the two sub-tropical terrestrial (Indochina Peninsula) stations, the isotopic minimum appeared without any relationship to rainfall amount but usually occurred at the leeward station during the rainy season. These results suggest that the isotopic variations of precipitation did not depend on the ’local’ rain-out history but on the rain-out process in the surrounding region. However, local rainfall events were associated not only with large-scale disturbances but also with regional circulation. Thus, the scale difference of controlling factors between local rainfall amount and isotopic value results in the weakening of the rainfall amount effect at the observation site and in the discrepancy between GCM simulations and observations. This finding suggests that regional precipitation–isotope relationships should be compared with GCM results. Additionally, because the isotope signal reflects the rain-out history at a regional scale, evaluation of the isotopic field using isotopic GCMs will be useful not only to reconstruct paleoclimate conditions but also to examine how GCMs can reproduce real atmospheric circulation over the tropics.     

气候模式对长江流域气温和降水的模拟性能评估及未来情景预估

利用政府间气候变化专门委员会第四次评估报告的22个新一代全球气候模式基准期(1961～1990年)模拟结果,从时空尺度分别讨论了与观测过程的差异,评估了模式对长江流域气温和降水的模拟性能。结果表明22个气候模式对长江流域具有一定的模拟能力,地面气温的模拟值都偏低,部分降水的模拟值局部偏高。不同的气候模式的模拟能力差异显著,大部分模式对长江流域的模拟精度有待进一步改进,只有少数几个模式（降水有6个模式,气温有5个模式）的年变化趋势与实况基本一致。综合比较,UKMO_HadCM3和NCAR_PCM两个模式基本能再现长江流域降水和气温的年变化特征。长江流域降水和气温未来情景预估表明各个模式和情景结果虽然存在差异,但对未来90年气候变化的模拟趋势基本一致,将持续增温、降水出现区域性增加,并着重讨论了UKMO_HadCM3模式在2020s（2010～2039年）、2050s（2040～2069年）和2080s（2070～2099年）3个时段的降水和气温时空变化特征,研究结果表明3个时段气温和降水在不同情景下都是逐渐增加的,A2情景下未来降水增幅最显著,B1情景增幅最小。     

东亚地区区域气候模拟的研究进展

由于大气环流模式对东亚地区区域气候特征的模拟存在很大不足,采用区域气候模式模拟该地区特殊的季风气候成为目前发展的一个重要研究方向,并取得了显著的研究进展。通过回顾当前东亚地区区域气候模拟的现状,表明大部分区域气候模式都不同程度地模拟出了东亚季风区持续性洪涝现象的大尺度环流特征和演变过程,再现了东亚各主要气候区降水的年际、季节和季节内变化及主要雨带的季节进退和降水的时空演变特征。但是,大部分模式没能很好地模拟出大尺度特征的强度和量值,模拟的温度和降水存在系统性偏差。原因分析表明,进一步完善和改进区域气候模式的物理过程参数化方案及动力框架可以改善模拟效果。最后对区域气候模式未来的发展给出展望。     

西南极乔治王岛冰芯研究——冰雪层定年、微粒记录及离子迁移

在分析南极乔治王岛冰帽大冰穹顶部降水和成冰条件的基础上,利用冰芯上部层物理特征参数确定的5个年层及其附近气象站相应的降水记录,结合多年降水资料将大冰穹45m冰芯划分为15个年层.应用此年层剖面,证实了微粒含量的两个异常峰值分别对应于1987年Deception岛和1980年的SealNunataks两次火山喷发.乔治王岛冰帽属于温性冰帽,大、小冰穹冰芯阴阳离子受沉积后融水渗浸淋溶作用的影响.对冰芯阴阳离子的淋溶次序分析显示,大冰穹为SO₄^2->Mg²⁺>Ca²⁺>K⁺>Cl^->Na⁺>NO₃^->Br^-,而小冰穹为Mg²⁺>Ca²⁺>SO₄^2->K⁺>Cl^->Br^->Na⁺.     

Climate change impact projections at the catchment scale in Tunisia using the multi-model ensemble mean approach

In this work, we developed a mean projection for climate change and assessed its impact on some hydro-meteorological indicators relevant to climatic condition, precipitation extremes magnitude and frequency for the Siliana catchment in Tunisia based on an ensemble of seven combinations of global circulation models (GCMs) and regional climate models (RCMs) derived from the EU-FP6 ENSEMBLES project. We performed quantile-based mapping (QM) bias correction technique of climate model projection using local observations. Because there is no warranty that the best climate model based on its performances in reproducing historic climate will be superior to other models in simulating future climate, we used the multi-model ensemble (MME) mean approach to derive a mean projection as the best guess for climate change projection for the Siliana catchment. We also quantified the uncertainty of the MME in the projected change in the selected indicators by comparing their values in the reference period (1981–2010) to these in the future period (2041–2070). Results reveal that the Siliana catchment will be prone to drier and warmer climate in the future with less rainy days for each month. The uncertainty associated with the MME projection suggests that no clear general tendency for extreme rainy days in the future is expected. These findings highlight the need to consider an ensemble of multi-climate models with an uncertainty framework if reliable climate change impact study is sought at the catchment scale.     

Performance of general circulation models and their ensembles for the prediction of drought indices over India during summer monsoon

The drought during the months of June to September (JJAS) results in significant deficiency in the annual rainfall and affects the hydrological planning, disaster management, and the agriculture sector of India. Advance information on drought characteristics over the space may help in risk assessment over the country. This issue motivated the present study which deals with the prediction of drought during JJAS through standardized precipitation index (SPI) using nine general circulation models (GCM) product. Among these GCMs, three are the atmospheric and six are atmosphere–ocean coupled models. The performance of these GCM’s predicted SPI is examined against the observed SPI for the time period of 1982–2010. After a rigorous analysis, it can be concluded that the skill of prediction by GCM is not satisfactory, whereas the ability of the coupled models is better than the atmospheric models. An attempt has been made to improve the accuracy of predicted SPI using two different multi-model ensemble (MME) schemes, viz., arithmetic mean and weighted mean using singular value decomposition-based multiple linear regressions (SVD-MLR) of GCMs. It is found that among these MME techniques, SVD-MLR-based MME has more skill as compared to simple MME as well as individual GCMs.     

Prograde metamorphism and decompression of the Gföhl gneiss, Czech Republic

Quartzofeldspathic rocks of the Gföhl gneiss from the Moldanubian of the Czech Republic span amphibolite-to granulite-facies, and are associated with eclogite. Protomylonitic fabrics related to terminal tectonic emplacement and reworking of the gneiss are common. Some non-mylonitic rocks, however, preserve early, prograde features (e.g., Opx-rimmed Hbl in metabasites), whereas others have characteristics generally associated with near-isothermal decompression (e.g., Pl-Opx moats separating Grt and Qtz in metabasites; Crd ± Spl coronas on Grt and aluminosilicates in metapelites); the unequivocal distinction between prograde and decompressional features in these rocks, however, may not be possible or even justified. For example, some metapelites contain growth-zoned (i.e., rimward increase in X_Mg) garnets that also record evidence (i.e., rimward decrease in X_Ca, compensated by the presence of reversely-zoned plagioclase in the same rock) of decompression. In rare instances, eclogitic rocks (P > 11 kbar) interpreted as tectonic enclaves within the gneiss also record mineralogic evidence of decompression (e.g., Crd-Opx-Spr coronas on pyrope). In metapelites, plagioclase-cored coronal garnets with high Prp/Grs ratios (˜ 2.5) record near-isobaric cooling from near the thermal maximum at a relatively shallow but undetermined crustal level.

Unlike Gföhl gneisses elsewhere (e.g., in Austria), the rocks described here do not preserve evidence of extreme metamorphic conditions. Texturally stable Grt-Bt pairs in non-mylonitic samples give T_max < 750 °C. P_max is not known, but prograde metamorphism apparently progressed from the kyanite to sillimanite fields, implying P ˜ 8 kbar at the maximum Grt-Bt temperature. At these conditions, dehydration of mafic gneiss occurred in the presence of a CO₂-rich (X_CO2 ˜ 0.85) pore fluid