Seasonal evaluation of rainfall estimation by four cumulus parameterization schemes and their sensitivity analysis

Sustainable water resources management require scientifically sound information on precipitation, as it plays a key role in hydrological responses in a catchment. In recent years, mesoscale weather models in conjunction with hydrological models have gained great attention as they can provide high‐resolution downscaled weather variables. Many cumulus parameterization schemes (CPSs) have been developed and incorporated into three‐dimensional Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model 5 (MM5). This study has performed a comprehensive evaluation of four CPSs (the Anthes–Kuo, Grell, Betts–Miller and Kain–Fritsch93 schemes) to identify how their inclusion influences the mesoscale model's precipitation estimation capabilities. The study has also compared these four CPSs in terms of variability in rainfall estimation at various horizontal and vertical levels. For this purpose, the MM5 was nested down to resolution of 81 km for Domain 1 (domain span 21 × 81 km) and 3 km for Domain 4 (domain span 16 × 3 km), respectively, with vertical resolutions at 23, 40 and 53 vertical levels. The study was carried out at the Brue catchment in Southwest England using both the ERA‐40 reanalysis data and the land‐based observation data. The performances of four CPs were evaluated in terms of their ability to simulate the amount of cumulative rainfall in 4 months in 1995 representing the four seasonal months, namely, January (winter), March (spring), July (summer) and October (autumn). It is observed that the Anthes–Kuo scheme has produced inferior precipitation values during spring and autumn seasons while simulations during winter and summer were consistently good. The Betts–Miller scheme has produced some reasonable results, particularly at the small‐scale domain (3 km grid size) during winter and summer. The KF2 scheme was the best scheme for the larger‐scale (81 km grid size) domain during winter season at both 23 and 53 vertical levels. This scheme tended to underestimate rainfall for other seasons including the small‐scale domain (3 km grid size) in the mesoscale. The Grell scheme was the best scheme in simulating rainfall rates, and was found to be superior to other three schemes with consistently better results in all four seasons and in different domain scales. Copyright © 2011 John Wiley & Sons, Ltd.     

Recent catastrophic debris flows in Luding county, SW China: geological hazards, rainfall analysis and dynamic characteristics

About 127 debris flow gullies have been identified, and debris flows have been an important type of geological hazards in Luding County, affecting cities, towns, rural areas, scenic spots and human’s engineering projects, such as mining and waterpower utilizing equipments. In this summary paper, recent two catastrophic debris flow events occurred on June 30, 2005, in Chuni town, in the central of the county, and on August 11, 2005, in Hailuogou scenic spot, in the southwest of the county, respectively, are reviewed. The debris flow events are introduced on the basis of field investigation and RS interpretation and the triggering factors for flow occurrence are identified. Furthermore, the rainfall related to flow occurrence including antecedent rainfall and intraday rainfall is analyzed, and a power-law function which can be used as a basic warning line is established based on both antecedent effective rainfall and intraday rainfall. Then dynamic parameters such as flow velocity and flow discharge are calculated, respectively. Through comparison and discussion, some conclusions are made including (1) The antecedent rainfall played an important role for debris flows which generated predominately based on the slope-instability due to the saturated loose sediments; (2) Despite slower flow velocity and smaller magnitude, the slope-type debris flows just like 2005-6-30 debris flows usually lead to serious damages for the difficulty to forecast and to prevent; (3) The mistaken recognition on debris flow hazards and lack of prevention consciousness strengthen the hazard and damage degree. This research is of certain significance for the prevention and mitigation of debris flow hazards and for the planning of the town building and tourism development in the future.     

Comparison of heat balance characteristics at five glaciers in the Southern Hemisphere

Ablation characteristics of five glaciers in Patagonia and New Zealand were compared. Investigated glaciers were Tyndall and Moreno in southern Patagonia, Soler and San Rafael in northern Patagonia, and Franz Josef in New Zealand. Micro-meteorological observations were carried out at the glaciers and the heat balance components were estimated. At Franz Josef and Soler glaciers, the sensible heat flux is the largest and the latent heat flux is the second, and they are larger than the net radiation. At San Rafael Glacier, the net radiation is the largest and the latent heat flux is the smallest component, which is similar to Moreno and Tyndall glaciers. Though the latent heat flux is the smallest component at San Rafael Glacier, it is more than twice as large as that at Tyndall Glacier and contributes substantially to ice melting. The ratios of heat balance components were very different among glaciers, but the total heat flux ranged from about 240 to 300 W m⁻² showing little difference among glaciers.     

西藏冈底斯岩带曲水杂岩体锆石LA-ICP-MS U-Pb年龄及其地质意义

曲水杂岩体位于冈底斯构造-岩浆岩带东段南缘,其岩浆活动与雅鲁藏布江新特提斯洋壳向北俯冲、消减以及印度与欧亚板块碰撞息息相关。本文以曲水县-昌果乡广泛分布的中酸性花岗岩体为研究对象,进行了系统的LA-ICP-MS锆石U-Pb年代学和岩石地球化学研究。结果表明,曲水杂岩体由3期时代和规模不同的花岗质岩体构成,其LA-ICP-MS锆石U-Pb年龄分别为95.2±1.0～88.5±1.0Ma、65.2±0.6Ma和48.5±0.5～43.3±0.7Ma;岩石地球化学研究表明,晚白垩世和古新世花岗岩以中性-中酸性为主,属钙碱性系列,具中铝特征,A/CNK比值小于1.1,属于I型花岗岩,是玄武质下地壳部分熔融产物,指示其形成于特提斯洋壳俯冲过程的岛弧构造环境。始新世花岗岩以高钾钙碱性系列为主,并出现钾玄岩系列,具偏铝-过铝质特征,指示岩浆上侵过程中遭受了不同程度的地壳物质混染,其形成于印度-欧亚板块强烈碰撞的构造环境。     

西昌市泸山地区典型火后泥石流特征与成因机制研究——以响水沟左岸3#支沟为例

2020年3月30日,四川省凉山州西昌市经久乡发生森林大火,山火燃烧后形成的山火灰和烧焦土体在强降雨作用下极易启动形成泥石流,给西昌市泸山、琼海景区生态环境及当地百姓生命财产安全带来潜在地质灾害风险。以西昌市安哈镇响水沟左岸3^#支沟为例,采用野外调查、无人机航拍、地球物理探测、现场及室内实验等手段,对2020年5月1日该沟发生的火后泥石流流体特征、动力学参数及成因机制等开展研究,系统分析了山火及降雨过程对该次火后泥石流形成的影响机制。该成果可为系统认识西昌泸山“3·30”山火地区火后泥石流的运动特征、物源规模、激发雨量及其发展趋势研判提供科学参考。     

Input data selection for solar radiation estimation

Model input data selection is a complicated process, especially for non‐linear dynamic systems. The questions on which inputs should be used and how long the training data should be for model development have been hard to solve in practice. Despite the importance of this subject, there have been insufficient reports in the published literature about inter‐comparison between different model input data selection techniques. In this study, several methods (i.e. the Gamma test, entropy theory, AIC (Akaike's information criterion)/BIC (Bayesian information criterion) have been explored with the aid of non‐linear models of LLR (local linear regression) and ANN (artificial neural networks). The methodology is tested in estimation of solar radiation in the Brue Catchment of England. It has been found that the conventional model selection tools such as AIC/BIC failed to demonstrate their functionality. Although the entropy theory is quite powerful and efficient to compute, it failed to pick up the best input combinations. On the other hand, it is very encouraging to find that the new Gamma test was able to choose the best input selection. However, it is surprising to note that the Gamma test significantly underestimated the required training data while the entropy theory did a better job in this aspect. This is the first study to compare the performance of those techniques for model input selections and still there are many unsolved puzzles. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison of LLR,MLP, Elman,NNARX and ANFIS Models—with a case study in solar radiation estimation

Despite the widespread application of nonlinear mathematical models, comparative studies of different models are still a huge task for modellers. This is because a large number of trial and error processes are needed to develop each model, so the workload will be multiplied into an unmanageable level if many types of models are involved. This study presents an efficient approach by using the Gamma test (GT) to select the input variables and the training data length, so that the trial and error workload can be greatly reduced. The methodology is tested in estimating solar radiation at the Brue catchment, UK. Several nonlinear models have been developed efficiently with the aid of the GT, including local linear regression, multi-layer perceptron (MLP), Elman neural network, neural network auto-regressive model with exogenous inputs (NNARX) and adaptive neuro-fuzzy inference system (ANFIS). This work is only feasible within the time and resources constraint, due to the GT in reducing huge workload of the trial and error process.     

Hydrological modelling using data from monthly GCMs in a regional catchment

This study demonstrates the use of spatially downscaled, monthly general circulation model (GCM) rainfall and temperature data to drive the established HyMOD hydrological model to evaluate the prospective effects of climate change on the fluvial run‐off of the River Derwent basin in the UK. The evaluation results of this monthly hydrological model using readily available, monthly GCM data are consistent with studies on nearby catchments employing high‐temporal resolution data, indicating that useful hydro‐climatic planning studies may be possible using standard datasets and modest computational resources. HyMOD was calibrated against 5 km² gridded UK Climate Projections dataset data and then driven using monthly spatially interpolated (~5 km²) outputs from Hadley Centre Coupled Model, version 3 and the Canadian Centre for Climate Modelling and Analysis for Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC‐SRES) A2a and B2a covering the 2020s, 2050s and 2080s. Results for both GCMs project a decrease in annual run‐off in both GCM models and scenarios with higher values in the summer/autumn months, whereas an increase in the later winter months. Both Hadley Centre Coupled Model, version 3 and the Canadian Centre for Climate Modelling and Analysis show higher ranges of uncertainty during the winter season with higher values of run‐off associated with December in all three simulation periods and two scenarios. A seasonal comparison of run‐off simulations shows that both GCMs give similar results in summer and autumn, whereas disparities due to GCM uncertainties are more conspicuous in winter and spring. In this study, both the GCMs under A2a scenario have demonstrated the high possibility of time shift in monthly average peak run‐offs in the Derwent River by 2080s in comparison with the early 21st century. Copyright © 2013 John Wiley & Sons, Ltd.     

川西地区地质灾害发育特征与时空分布规律

川西地区受青藏高原隆升和发育于青藏高原的大江大河深切割等作用,共发育地质灾害16411处,以滑坡和泥石流为主,是我国地质灾害高风险地区。本文采用资料收集、数理统计、Arcgis软件分析等方法分析发现,川西地质灾害具有成因机制复杂,突发性、群发性与链生性、危害大等特点。形成机理差异大,滑坡变形模式以滑移-拉裂、蠕滑-剪断、倾倒折断等模式为主;泥石流形成机理主要为土力-水力驱动型和堵溃型;崩塌失稳主要表现为滑移式、倾倒式和坠落式。发育分布规律在低山和中山区呈带状,和沿活动断裂带和深切河谷呈线状集中分布;受地震和强降雨影响,地质灾害年际变化大,2008、2009、2013年、2017年地质灾害频发、高发和群发期。     

西藏昌都白格滑坡斜坡地质结构特征及成因机制

在西藏昌都市江达县波罗乡发生的两次高位大型滑坡,形成堰塞体阻断金沙江,其溃决洪水对下游造成了巨大损失.本文基于野外地质调查与工程验证、遥感影像、倾斜摄影测量、岩体微观特征,结合区域地质资料进行分析研究.结果表明:(1)白格滑坡发育于金沙江构造混杂岩带,坡体属于河谷型构造破碎松散体;(2)坡体物质主要由弱变形构造透镜体岩块和强变形错动带(糜棱岩带、碎裂岩带、断层泥)组成,镜下岩石结构破坏严重,岩石强度显著降低;(3)断层破碎带控制滑坡体两侧及后缘边界,为滑坡提供了侧向及后缘的切割面;(4)不连续错动带为白格滑坡的滑动层,在重力卸荷作用下发生贯通,导致坡体发生多期次崩滑;(5)综合坡体失稳启动分析,白格滑坡为"推移式+牵引式"混合型滑坡;(6)白格滑坡是在内动力和外动力耦合作用相互交替下促进形成,加之金沙江对坡脚掏蚀,松散体在重力卸荷作用下剪切破坏致使滑坡发生.白格滑坡事件可为研究金沙江构造混杂岩带中大型滑坡形成机制提供依据,同时也为该区域防灾减灾研究提供理论指导.