Probabilistic SWE reanalysis as a generalization of deterministic SWE reconstruction techniques

Snow accumulation and melt is highly variable in space and time in complex mountainous environments. Therefore, it is necessary to provide high‐resolution spatially and temporally distributed estimates of sub‐basin snow water equivalent (SWE) to accurately predict the timing and magnitude of snowmelt runoff. In this study, we compare two reconstruction techniques (a commonly used deterministic reconstruction vs a probabilistic data assimilation framework). The methods retrospectively estimate SWE from a time series of remotely sensed maps of fractional snow‐covered area (FSCA). In testing both methods over the Tokopah watershed in the Sierra Nevada (California), the probabilistic reconstruction approach is shown to be a more robust generalization of the deterministic reconstruction. Under idealized conditions, both probabilistic and deterministic approaches perform reasonably well and yield similar results when compared with in situ verification data, whereas the probabilistic reconstruction was found to be in slightly better agreement with snow‐pit observations. More importantly, the probabilistic approach was found to be more robust: unaccounted for biases in solar radiation impacted the probabilistic SWE estimates less than the deterministic case (4% vs 7% errors for water year (WY)1997 and 0% vs 3% errors for WY1999); the probabilistic reconstruction was found to be less sensitive to the number of available observations (6% vs 10% errors in WY1997 and 13% vs 44% errors in WY1999 from the nominal cases when four fewer FSCA images were available). Finally, results from the probabilistic reconstruction approach, which requires precipitation inputs (unlike the deterministic approach), were found to be relatively robust to bias in prior precipitation estimates, where the nominal case mean estimates were recovered even when an underestimated prior precipitation was used. The additional robustness of the probabilistic SWE reconstruction technique should prove useful in future applications over larger basins and longer periods in mountainous terrain. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of runoff components using path analysis and isotopic measurements in a glacier‐covered alpine catchment (upper Hailuogou Valley) in southwest China

Monitoring of stable water isotopes (δ¹⁸O and δ²H) at the watershed scales can improve our understanding of complex hydrology and hydroclimatology of the watershed, especially in remote regions. Previous studies that used tracers for hydrograph separation are largely based on end‐member mixing approach (EMMA), but one drawback of this approach is that at least two independent tracers are required for multi‐component separation. Here we introduce a new approach—path analysis, in combination with isotopic measurements to investigate the runoff generation in a glacier‐covered alpine catchment (upper Hailuogou Valley) in southwest China. This newly developed method can not only provide a multi‐component hydrograph separation with the aid of only one tracer but also determine the direct and indirect influence of sources on streamflow. Path analysis show that the majority of streamflow is dominated by ice/snow meltwater that represents about 63–78% of the total discharge, whereas precipitation and groundwater contribute approximately 19–39% and 2–4% of the streamflow discharge, respectively. These results are in good agreement with those derived from EMMA (using ¹⁸O and Cl^? as tracers), corroborating that our proposed approach is successful in hydrograph separation of the catchment. This approach may provide new opportunities for the hydrograph separation of catchment with sparse data and be of interest to catchment hydrologists who seek to understand the behaviour of hydrologic systems. Copyright © 2015 John Wiley & Sons, Ltd.     

大兴安岭嫩江科洛浅覆盖区断裂构造调查

位于大兴安岭北段东坡的嫩江科洛地区属于典型的浅覆盖区。针对该区特殊的地质地貌特点,尝试利用重力和航磁技术解译和推断,结合野外露头调查和查证的综合研究方法对区域内断裂构造进行识别和应力机制分析。通过基岩出露区的验证,该方法对浅覆盖区断裂构造性质及活动特点的推断解释具有较明显的效果。因此,本文认为重磁、露头观测的综合应用,起到了相互补充、印证的效果,减少了推断结果的多解性,提升了解释成果的可靠性。为浅覆盖区地质填图、区域构造研究及成矿预测等提供了有效的技术方法支撑。     

冬季香梨树彩条布覆盖棚的温湿度效应分析

摘 要：为了探讨冬季香梨园覆盖棚内外的温、湿度变化规律,于2014～2015年库尔勒市上户镇哈拉苏村香梨园进行小气候观测试验,对2015年1月彩条布覆盖棚内部、外部气温、相对湿度的变化规律进行分析。结果表明:彩条布覆盖棚棚内气温高于棚外,一天中 最低气温出现在夜间（21:00～09:00）,棚内外气温变化主要受太阳辐射影响;棚内外低于-15℃的天数均大于15d,低于-20℃的平均时长为5h,最大持续时长为7h;棚内日较差高于棚外,棚内外气温日较差变化趋势一致,棚内外0.4m高度的降温幅度分别为0.3002℃/d（P=0.001）、0.2324℃/d（P=0.006）,棚内外3m高度的降温幅度分别为0.2786℃/d（P=0.006）、0.2347℃/d（P=0.000）;棚内日平均相对湿度高于棚外,在两个高度下,棚内外日平均相对湿度变化趋势相似, 棚内外0.4m高度增湿幅度分别为0.2688%/d（P=0.000）、0.2391%/d（P=0.007）,棚内外3m高度增湿幅度分别为0.0767%/d（P=0.075）、0.2586%/d（P=0.006）。     

极地吊舱推进船舶回转性能的离散元分析

吊舱推进装置在极地船舶中被广泛应用,其转舵模块可以带动螺旋桨摆动从而产生任意方向的推进力,使船舶操纵更为灵活。提出了一种吊舱推进船舶冰区操纵的离散元方法,对具有吊舱推进装置的冰区船舶破冰过程进行了数值模拟。以“雪龙2”号破冰船为研究对象,计算分析了船舶定速直航时的冰阻力,并通过与Lindqvist经验公式的对比验证了冰阻力计算的合理性。在此基础上进一步对船舶在不同冰厚、不同吊舱转向角下的回转破冰运动进行了离散元模拟,分析了回转半径与船长比值随冰厚的变化规律。计算结果表明：船舶的回转性能随冰厚的增大而降低,并随吊舱转向角的增大而显著提高。     

Evaluation of the snow‐covered area data product from MODIS

The Moderate Resolution Imaging Spectroradiometer (MODIS), flown on board the Terra Earth Observing System (EOS) platform launched in December 1999, produces a snow‐covered area (SCA) product. This product is expected to be of better quality than SCA products based on operational satellites (notably GOES and AVHRR), due both to improved spectral resolution and higher spatial resolution of the MODIS instrument. The gridded MODIS SCA product was compared with the SCA product produced and distributed by the National Weather Service National Operational Hydrologic Remote Sensing Center (NOHRSC) for 46 selected days over the Columbia River basin and 32 days over the Missouri River basin during winter and spring of 2000–01. Snow presence or absence was inferred from ground observations of snow depth at 1330 stations in the Missouri River basin and 762 stations in the Columbia River basin, and was compared with the presence/absence classification for the corresponding pixels in the MODIS and NOHRSC SCA products. On average, the MODIS SCA images classified fewer pixels as cloud than NOHRSC, the effect of which was that 15% more of the Columbia basin area could be classified as to presence–absence of snow, while overall there was a statistically insignificant difference over the Missouri basin. Of the pixels classified as cloud free, MODIS misclassified 4% and 5% fewer overall (for the Columbia and Missouri basins respectively) than did the NOHRSC product. When segregated by vegetation cover, forested areas had the greatest differences in fraction of cloud cover reported by the two SCA products, with MODIS classifying 13% and 17% less of the images as cloud for the Missouri and Columbia basins respectively. These differences are particularly important in the Columbia River basin, 39% of which is forested. The ability of MODIS to classify significantly greater amounts of snow in the presence of cloud in more topographically complex, forested, and snow‐dominated areas of these two basins provides valuable information for hydrologic prediction. Copyright © 2003 John Wiley & Sons, Ltd.     

浅覆盖城市经济区立体填图最新进展——浙江1∶5万鸣鹤镇、澥浦镇、慈城镇、鄞江镇、姜山镇幅区调项目成果

本文结合浙江1∶5万鸣鹤镇、澥浦镇、慈城镇、鄞江镇、姜山镇幅区调项目实际材料,系统论述了浅覆盖城市经济区立体填图的内容、方法、手段和工作程序,总结了慈城测区区域地质调查项目组浅覆盖区立体填图的方法与经验,论述了浅覆盖城市经济区立体填图最新进展,可供城市经济区地质调查和浅覆盖区三维立体填图借鉴.     

蒙古国东南部钨多金属靶区的快速圈定与成矿分析

复杂地表条件下矿产勘探一直是个难题,国外区块更是如此,首次利用XLT一592WZ型便携式XRF分析仪在蒙古国苏赫巴托尔省（额尔德尼查干苏木）13451X草原覆盖地区系统采集数据,分析研究并圈定成矿靶区。初期利用x荧光仪进行扫面勘探,发现有W、As、Ph、Zn、Cu、Fe等元素异常,经过异常查证优选了一个钨多金属找矿远景区。在钨多金属找矿远景区内通过23条探槽和钻探工程进一步揭露发现一条黑钨矿体;钨矿主要以脉状、团块状或是角砾状形式出现,成矿围岩为花岗斑岩,矿石以黑钨矿为主,白钨矿极少,可见硅化、萤石,推测该区成矿类型为高温热液型黑钨矿。综合来看,在野外利用便携式X荧光光谱仪进行定性与半定量分析是有效的,该方法可在同类地区推广应用。     

长江口沙波分布区桥墩局部冲刷深度计算公式的改进

利用多波束水深仪、浅地层剖面仪和多普勒流速仪对长江口苏通大桥南、北主墩区域现场测量,结果显示主墩周围最大冲刷深度为8.3 m和19.6 m。建墩前后河床形态变化显著,建墩后桥墩所在床面由平床改变为典型不对称沙波发育,平均波长为30.8 m和23.1 m,平均波高为4.2 m和9.4 m,陡坡朝向下游。基于实测水文条件和地形资料,以沙波起动流速和落急最大流速分别取代单向流作用下"平床"假定的桥墩局部冲刷计算公式中单颗粒泥沙的起动流速和墩前流速,获得河口涨落潮双向流作用下沙波底床桥墩局部冲刷计算公式。且该公式计算的苏通大桥南、北主墩局部冲刷深度为9.5 m和22.1 m,非常接近实测值。     

浅谈建筑竣工测量面积计算自动化

建设工程竣工测量面积直接影响城市规划管理部门的行政决策和建设单位的经济效益,所以竣工面积计算的准确性很重要.文章对房屋竣工测量过程中有关房屋建筑面积计算问题进行了探讨,提出了实际工作中的解决方法及建议.