Describing alpine lake influence on stream network temperatures: A statistical modelling approach     

Samuel P. Carlson  Geoffrey C. Poole 《水文研究》2021,35(3):e14072

Systematic variations in atmospheric heat exchange, surface residence time, and groundwater influx across montane stream networks commonly produce an increasing stream temperature trend with decreasing elevation. However, complex stream temperature profiles that differ from this common longitudinal trend also exist, suggesting that stream temperatures may be influenced by complex interactions among hydrologic and atmospheric processes. Lakes within stream networks form one potential source of temperature profile complexity due to the spatially variable contribution of lake-sourced water to stream flow. We investigated temperature profile complexity in a multi-season stream temperature dataset collected across a montane stream network containing many alpine lakes. This investigation was performed by making comparisons between multiple statistical models that used different combinations of stream and lake characteristics to represent specific hypotheses for the controls on stream temperature. The compared models included a set of models which used a topographically derived estimate of the hydrologic influence of lakes to separate and quantify the effects of stream elevation and lake source-water contributions to longitudinal stream temperature patterns. This source-water mixing model provided a parsimonious explanation for complex stream-network temperature patterns in the summer and autumn, and this approach may be further applicable to other systems where stream temperatures are influenced by multiple water sources. Simpler models that discounted lake effects were more optimal during the winter and spring, suggesting that complex patterns in stream temperature profiles may emerge and subside temporally, across seasons, in response to diversity of water temperatures from different sources.  相似文献   

不同结构林带防风效能风洞模拟     

李晓烨  王克俭  谷建才  刘启国  崔严 《中国沙漠》2019,39(6):118-125

防风林带结构是影响防风效能的主要因素。建立不同宽度、不同株行距林带防风效能与林带后距离之间的统计模型，可以为防风林建设提供指导性意见。通过风洞实验，在11 m·s^-1风速下，对4种宽度、5种株行距林带的背风面0~10H（H为林带高度）的风速进行测定，采用曲线参数估计法、傅立叶模型、SSF模型（Sum of Sin Functions），构建了不同结构林带防风效能与林带后距离间的统计模型。结果表明：傅立叶模型拟合不同宽度林带的防风效能与林带后距离的关系效果最优，可决系数（R²）均在98%以上；SSF模型拟合不同株行距林带的防风效能与林带后距离的关系效果最优（R²>0.98）。根据构建的统计模型，风速为11 m·s^-1左右时，林带宽度8 m（两行一带）的防风林的防风效能存在明显优势；5种株行距的林带中，株行距为8 m×8 m的防风林带本试验条件下防风效果最好。  相似文献   

湍流度随高度的变化及其对城市宏观地形的依赖     

李大全  孙武  欧阳睿康  黄盛  高梦媛  李庆祥  黄启明 《热带地理》2019,39(3):365-376

分别构建广州主建成区垂直比例尺为1﹕2 000、1﹕1 000和1﹕500的3个建筑物模型，利用大型边界层风洞，在西北和东南两风向下，基于中性流模拟分析了复杂城市地形下湍流度随高度的变化及其对宏观地形的依赖。结果表明：风廓线指数α与不同高度的湍流度之间的关系密切，利用现有模型，根据4类粗糙度边界层和不同垂直比例尺，可确定相应的湍流度随高度变化模型的主要系数，预测精度高。城市地形下最大湍流度面发育在0~0.2 h之间狭窄的范围内。用湍流度形态指数β来表征湍流度随高度的变化，无论城市屋脊还是平坦地形，随着风程区的延伸，廓线的指数α升高，湍流度形态指数β降低。表明同一高度湍流度值具有由迎风区、丘顶区向背风区增高，沿风程逐渐增大的规律，对地形部位和风程的依赖性强，与来流翻越简单地形时的特征一致。  相似文献   

2015年台风“彩虹”过境后下山冷急流引起的南海北部海域异常海面降温   总被引：1，自引：0，他引：1  

石雨鑫  谢玲玲  郑全安  张书文  李明明  李君益 《海洋学报(英文版)》2019,38(5):62-75

This study deals with a unusual cooling event after Typhoon Mujigea passed over the northern South China Sea(SCS) in October 2015. We analyze the satellite sea surface temperature(SST) time series from October 3 to 18,2015 and find that the cooling process in the coastal ocean had two different stages. The first stage occurred immediately after typhoon passage on October 3, and reached a maximum SST drop of –2℃ on October 7 as the usual cold wake after typhoon. The second stage or the unusual extended cooling event occurred after 7d of the typhoon passage, and lasted for 5d from October 10 to 15. The maximum SST cooling was –4℃ and occurred after 12d of typhoon passage. The mechanism analysis results indicate that after landing and moving northwestward to the Yunnan-Guizhou Plateau(YGP), Typhoon Mujigea(2015) met the westerly wind front on October 5. The lowpressure and positive-vorticity disturbances to the front triggered meridional air flow and low-pressure trough,thus induced a katabatic cold jet downward from the Qinghai-Tibet Plateau(QTP) passing through the YGP to the northwestern SCS. The second cooling reached the maximum SST drop 4d later after the maximum air temperature drop of –9℃ on October 11. The simultaneous air temperature and SST observations at three coastal stations reveal that it is this katabatic cold jet intrusion to lead the unusual SST cooling event.  相似文献   

黄土高原沟谷地貌发育演化研究进展与展望     

熊礼阳  汤国安 《地球信息科学学报》2020,22(4):816-826

黄土沟谷是黄土地貌中最有活力、最具变化、最富特色的对象单元,黄土高原千沟万壑的地貌形态以及触目惊心的侵蚀状态也让区域内沟谷地貌的形成、发育及演化问题成为研究中焦点及前沿性科学问题。近年来,诸多学者采用地学测年法、特征表达法、监测模拟法力图实现对黄土沟谷发育演化进程中“过去-现代-未来”的科学认知。这些研究在相当程度上丰富了黄土沟谷发育过程的认知。本文梳理了黄土高原沟谷地貌演化相关研究的现状,并从黄土高原地貌演化、黄土沟谷发育、基于DEM的沟谷信息提取与表达等研究进行了系统的回顾、梳理与分析。此外,本文提出“黄土沟道剖面群组”概念与方法,试图从新的视角审视黄土沟谷地貌发育演化过程。沟道剖面在黄土沟谷发育演化进程中传递物质能量和累积地形动力,并通过径流节点的串联实现剖面群的连接与组合,形成独特的剖面“群组”模式;该沟道剖面群组是集黄土沟谷地貌特征与过程于一体的综合信息集成体,其三维空间结构是对黄土沟谷地貌发育演化的高度抽象与映射,并可望进一步丰富黄土高原数字地形分析理论与方法体系,为黄土高原黄土地貌成因机理与空间分异格局带来创新的认识。  相似文献   

多能互补海洋能集成发电技术研究综述     

王世明  李泽宇  于涛  马晨倍 《海洋通报》2019,38(3)

介绍了国内外基于风能、太阳能、波浪能和潮流能等海上可再生能源进行多能互补集成发电的研究发展情况,从不同技术研究侧重点、不同装置机理差异性和多能互补集成发电方式等方面进行了概括和综述,对已有设备和理论研究等进行了对比,评述了目前海洋多能互补集成发电技术研究中存在的主要问题以及未来的研究发展趋势,指出未来海洋能源集成发电需在离岸化、新材料、大型化和阵列布局等方面进行技术研究和攻关。  相似文献   

浅层地震剖面揭示固原市清水河东侧断裂特征     

花鑫升  姬计法  酆少英  杜鹏  宋威  刘增祺 《大地测量与地球动力学》2019,39(8):794-797

为查明清水河东侧断裂的产状、性质及其浅部构造特征，跨断裂开展高分辨率的浅层地震探测，获得高信噪比的浅层地震反射叠加剖面。根据浅层地震剖面结果并结合该区域地质资料，对该断裂的浅部构造特征进行分析和讨论。结果表明，清水河东侧断裂为一条走向近SN、倾向E的逆断层，其浅部为由2~3条断层组成的“Y”字形构造，并错断埋深约10~30 m的第四系沉积层，属第四纪以来的隐伏活动断裂。  相似文献   

风和径流量对长江口缺氧影响的数值模拟   总被引：1，自引：1，他引：0  

郑静静  刘桂梅  高姗  李云  李志杰 《海洋学报》2018,40(9):1-17

受自然和人类活动的影响，海洋缺氧现象日益严重，威胁着海洋生态环境，海洋缺氧问题已经引起了人们的广泛关注。本文应用区域海洋模式并耦合生态模式，对东海的生态系统进行了数值模拟和分析研究。与观测数据比较显示，该模型能较好地模拟长江口外生态变量的分布趋势。另外本文通过设置不同敏感性实验，探讨风和径流量对长江口底层缺氧现象的影响，结果分析表明，风和径流量对长江口外缺氧区的形成有显著的影响。径流量变化虽然对长江口外缺氧区的季节变化影响并不显著，但是对缺氧区域面积却存在显著的影响。径流量增加，水体层化增强，表层叶绿素浓度增加，最终导致缺氧区域范围扩展；径流量减小，水体层化减弱，表层叶绿素浓度减小，缺氧区域范围缩小。风向和风速的改变不仅影响长江口外缺氧区的季节变化，还影响缺氧区域面积。  相似文献   

Wetland hydroperiod classification in the western prairies using multitemporal synthetic aperture radar          下载免费PDF全文

Joshua S. Montgomery  Chris Hopkinson  Brian Brisco  Shane Patterson  Stewart B. Rood 《水文研究》2018,32(10):1476-1490

Wetlands represent one of the world's most biodiverse and threatened ecosystem types and were diminished globally by about two‐thirds in the 20th century. There is continuing decline in wetland quantity and function due to infilling and other human activities. In addition, with climate change, warmer temperatures and changes in precipitation and evapotranspiration are reducing wetland surface and groundwater supplies, further altering wetland hydrology and vegetation. There is a need to automate inventory and monitoring of wetlands, and as a study system, we investigated the Shepard Slough wetlands complex, which includes numerous wetlands in urban, suburban, and agricultural zones in the prairie pothole region of southern Alberta, Canada. Here, wetlands are generally confined to depressions in the undulating terrain, challenging wetlands inventory and monitoring. This study applied threshold and frequency analysis routines for high‐resolution, single‐polarization (HH) RADARSAT‐2, synthetic aperture radar mapping. This enabled a growing season surface water extent hyroperiod‐based wetland classification, which can support water and wetland resource monitoring. This 3‐year study demonstrated synthetic aperture radar‐derived multitemporal open‐water masks provided an effective index of wetland permanence class, with overall accuracies of 89% to 95% compared with optical validation data, and RMSE between 0.2 and 0.7 m between model and field validation data. This allowed for characterizing the distribution and dynamics of 4 marsh wetlands hydroperiod classes, temporary, seasonal, semipermanent, and permanent, and mapping of the sequential vegetation bands that included emergent, obligate wetland, facultative wetland, and upland plant communities. Hydroperiod variation and surface water extent were found to be influenced by short‐term rainfall events in both wet and dry years. Seasonal hydroperiods in wetlands were particularly variable if there was a decrease in the temporary or semipermanent hydroperiod classes. In years with extreme rain events, the temporary wetlands especially increased relative to longer lasting wetlands (84% in 2015 with significant rainfall events, compared with 42% otherwise).  相似文献   

基于MISR多角度光学遥感影像的海面风速估算实验          下载免费PDF全文

王艺霖  王晓林  张华国 《海洋学研究》2018,36(2):19-26

太阳耀光是来自粗糙海面的直接太阳反射光,其强度与海面粗糙度密切相关,而海面粗糙度主要受海面风场影响。因此,包含太阳耀光信息的光学遥感影像在海洋动力过程和海面风速探测中具有积极意义。本文利用2016年2月到2017年3月期间成像的25幅Terra卫星MISR(Multi-angle Imaging Spectro Radiometer)传感器的多角度遥感影像,分别提取了太阳的高度角和方位角、正视和后视影像的卫星观测角、方位角等信息,校正获得正视和后视影像的太阳耀光辐射强度,进一步反演海表面粗糙度信息,进而计算海面风速。最后利用ECMWF(European Centre for Medium-Range Weather Forecasts)的模式风速数据与反演获得的风速结果进行对比验证。结果表明,两者的相关系数较高(R=0.745),均方根误差和平均绝对偏差值分别为1.514 m·s^-1和1.319 m·s^-1。初步实验结果表明,利用MISR多角度光学遥感影像估算海表面风速是可行性的。  相似文献