Snow cover and runoff modelling in a high mountain catchment with scarce data: effects of temperature and precipitation parameters

Snowmelt is an important source of runoff in high mountain catchments. Snowmelt modelling for alpine regions remains challenging with scarce gauges. This study simulates the snowmelt in the Karuxung River catchment in the south Tibetan Plateau using an altitude zone based temperature‐index model, calibrates the snow cover area and runoff simulation during 2003–2005 and validates the model performance via snow cover area and runoff simulation in 2006. In the snowmelt and runoff modelling, temperature and precipitation are the two most important inputs. Relevant parameters, such as critical snow fall temperature, temperature lapse rate and precipitation gradient, determine the form and amount of precipitation and distribution of temperature and precipitation in hydrological modelling of the sparsely gauged catchment. Sensitivity analyses show that accurate estimation of these parameters would greatly help in improving the snowmelt simulation accuracy, better describing the snow‐hydrological behaviours and dealing with the data scarcity at higher elevations. Specifically, correlation between the critical snow fall temperature and relative humidity and seasonal patterns of both the temperature lapse rate and the precipitation gradient should be considered in the modelling studies when precipitation form is not logged and meteorological observations are only available at low elevation. More accurate simulation of runoff involving snowmelt, glacier melt and rainfall runoff will improve our understanding of hydrological processes and help assess runoff impacts from a changing climate in high mountain catchments. Copyright © 2013 John Wiley & Sons, Ltd.     

Interannual variation of evapotranspiration in an eastern Siberian larch forest

In a deciduous larch forest in eastern Siberia, the mean and standard deviation of the total evapotranspiration (E) during May to September (day of year (DOY) = 121–274) for 2003–2006 were 181.5 and 26.4 mm, respectively. The interannual variation (IAV) in the total E was caused by the IAV in E for the canopy‐foliated period (DOY = 164–253), not by the IAV in the dates of leaf expansion and leaf fall. For the years with higher total E, E in the canopy‐foliated period was consistently higher, which corresponded to the higher soil water content in these years. Copyright © 2012 John Wiley & Sons, Ltd.     

RS与GIS支持下的汶川县城周边地质灾害危险性评价

地质灾害危险性评价是防灾减灾工作的重要依据。本文以汶川县城周边64 km2为例,应用遥感信息提取技术与GIS空间分析方法,根据IKONOS遥感图像和地形图及野外调查资料,提取了崩塌和滑坡易发性评价因子,采用信息量法确定了因子分值,计算了崩塌和滑坡易发性,并分别提出崩塌和滑坡的危险性计算方法,形成了汶川地区崩塌和滑坡危险性分区图。研究结果表明:新的崩塌和滑坡危险性评价方法能够反映区内地质灾害危险程度,该方法可行,结果合理,这为中、大比例尺区域范围内地质灾害危险性研究提供了有益的思路。     

多普勒雷达资料在飞机增雨作业中的应用研究

利用滨州714SDN雷达体积扫描资料、济南探空和机载PMS微物理探测资料,按降水冷云云层分布特点,选择不同Z-M关系计算降水条件下各特定层垂直积分含水量;结合天气资料及雷达速度场分布特征,分析降水云层演变特征及人工增雨播云条件,确定增雨作业时间和区域.     

三江源地区秋季一次层积云飞机人工增雨催化试验的微物理响应

利用三江源地区一次在层积云顶部进行的飞机锯齿形催化作业及回穿探测的全球卫星定位系统(GPS)轨迹和机载云粒子测量系统(PMS)资料,在确定作业前后有效对比区间、区分云粒子相态的基础上,通过分析作业前、后液态云粒子及冰晶浓度变化、云粒子谱的演变和过冷水含量比率的变化,研究了催化的微物理响应。结果表明,作业区液态云粒子中值直径集中在3.5—18.5 μm,直径21.5—45.5 μm的云粒子基本上为冰晶,粒径大于50 μm的粒子相态为冰相;锯齿形作业后约2—23 min,在其航线下风方36 km范围内,前向散射粒子谱探头(FSSP-100)和二维灰度云粒子探头(OAP-2D-GA2,简称2DC)所测云粒子浓度、直径变化均未超出作业前云区内的自然起伏,但在过冷水含量大于0.01 g/m³的高过冷水区,液态云粒子浓度明显降低,前向散射粒子谱探头量程内的冰晶粒子浓度明显升高,冰相含水量增大,过冷水含量比率的平均值由作业前的 (68.3±23.1)% 减小至(34.2±12.4)% 。在过冷水含量越高的区域,催化效应越明显,而在低过冷水区和仅受原点催化影响的航迹交叉点处均未观测到催化响应。     

Quantitative evaluation of strategies for erosion control on a railway embankment batter

Strategies for erosion control on a railway embankment batter (side slope) are quantitatively evaluated in this paper. The strategies were centred on control (‘do nothing’ treatment), grass seeding, gypsum application, jute mat (an erosion control blanket) placement and planting hedgerows of Monto vetiver grass. Rainfall and runoff were monitored at 1 min intervals on 10 m wide embankment batter plots during 1998 and 1999. Total bedload and suspended sediment eroded from the plots were also measured but only for a group of storm events within sampling intervals. It has been demonstrated that vetiver grass is not cost‐effective in controlling erosion on railway batters within Central Queensland region. Seeding alone could cause 60% reduction in the erosion rate compared with the control treatment. Applying gypsum to the calcium‐deficient soil before seeding yielded an additional 25% reduction in the erosion rate. This is the result, primarily, of 100% grass cover establishment within seven months of sowing. Therefore, for railway embankment batter erosion control, the emphasis needs to be on rapid establishment of 100% grass cover. For rapid establishment of grass cover, irrigation is necessary during the initial stages of growth as the rainfall is unpredictable and the potential evaporation exceeds rainfall in the study region. The risk of seeds and fertilizers being washed out by short‐duration and high‐intensity rainfall events during the establishment phase may be reduced by the use of erosion control blankets on sections of the batters. Accidental burning of grasses on some plots caused serious erosion problems, resulting in very slow recovery of grass growth. It is therefore recommended that controlled burning of grasses on railway batters should be avoided to protect batters from being exposed to severe erosion. Copyright © 2001 John Wiley & Sons, Ltd.     

The Quetzalapa Pumice: a voluminous late Pleistocene rhyolite deposit in the eastern Trans-Mexican Volcanic Belt

The study area is located in the east part of the Trans-Mexican Volcanic Belt, in the Las Cumbres Volcanic Complex (LCVC) which lies between two large stratovolcanoes: Pico de Orizaba (5700 m a.s.l.) to the south, and Cofre de Perote (4200 m a.s.l.) to the NNE. The most conspicuous structure of the LCVC is a 4-km-diameter circular crater with a dacitic dome in the center, which constitutes the remains of a destroyed stratovolcano.The Quetzalapa Pumice (QP) was produced by a plinian eruption that was dated by the ¹⁴C method at 20 000 yr. BP. The eruptive sequence consists predominantly of pumice fall deposits and scarce intra-plinian pyroclastic flow deposits, which crop out on the west flank of the LCVC. The absence of post-plinian ignimbrite deposits is striking.The deposits are well sorted, clast-supported with reverse grading at the base, with a medium to high accessory lithics content. The maximum average thickness of the deposit in the proximal areas is about 15 m and has been divided into three members: the Basal Member (BM), 2 m thick with four submembers (BMf₁, BMf₂, BMf₃, and BMafl), the Intermediate Member (IM), 10 m thick with two submembers (IMpf and IMaf), and the Upper Member (UM), 3 m thick with four submembers (UMpl, UMsdf, UMwaf, and UMpls).The predominant component of the fall deposits is a white, highly vesiculated pumice with 71% SiO₂ content. Plagioclase is the most abundant mineral followed by 1–3-mm-long biotite phenocrysts. The accessory lithics are lavas mostly of andesitic composition. Their abundance increases toward the uppermost levels of the sequence.We calculate a minimum volume of 8.4 km³ (2.22 km³ dense rock equivalent), for the entire QP deposit. Isopach and isopleth maps show that the IM deposit has an elongated distribution with a NNE–SSW direction, whereas the UM deposit has a circular distribution.We estimate a maximum eruptive column height for the IM of 20 km. Field studies and isopach and isopleth maps indicate that the eruptive column was affected by a strong wind.Previous studies located the QP source in the Las Cumbres crater. However, based on the isopach and isopleth distribution, and the lack of pumice fall deposits inside the Las Cumbres crater, we consider that the QP emission center is located on the west flank of the LCVC, and was buried by its own pumice fall deposits. It coincides with an explosion crater called La Capilla formed during the closing phase of the QP eruption.A ‘pumice fountain’ model is proposed to explain the observed sequence of deposits. According to this model, the material was emitted through a ‘hose-type’ conduit during a monogenetic eruption of rhyolitic composition. This kind of volcanic activity is not extensively reported in the literature.     

地形云人工增雨条件卫星探测反演个例分析

选取2007年6月21日陕西白于山区地形云降水过程,用极轨卫星资料反演高空间分辨率的云微物理特征.对云降水物理结构分析表明:(1)山前云区(迎风坡)云顶亮温(T)为-31℃,粒子有效半径(Re)为9μm,含有丰富过冷水,缺乏冰晶;(2)T=-20℃的低云在有高云参与的情况下,产生了较多的降水;(3)山前云区面积约400...     

一次积层混合云飞机播云对云微物理过程影响效应的分析

人工增雨效果评估主要关注的是催化后云和降水过程是否产生了预期的变化,这首先表现在云和降水的宏微观过程有无明显变化,因此了解播云作业后的云微物理结构的变化是很必要的.2009年4月18日在河北张家口进行了一次飞机播云实验,本文采用飞机探测所取得的PMS资料,分析了播云对云微物理过程影响,并进行了云物理因子综合研究.结果表明:催化后播云高度上液态含水量大幅度降低,粒子平均直径由催化前20.4μm增大到23.9 μm;云中粒子谱结构也发生很大的变化,催化后冰晶减少,降水尺度粒子显著增加;而且在播云1小时后影响区地面累计降雨量达到最大.