Knowledge Resource Center for Ecological Environment in Arid Area
| 西北干旱区极端降水的变化及其与山区洪水的关系 | |
| 其他题名 | Extreme Precipitation Change in Northwest Arid Region of China and Its Relationship with Mountainous Floods |
| 王少平 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 丁永建 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 西北干旱区在全球气候变化的背景下，降雨增多，降雪变化显著，冰雪消融加速，河流径流增加，极端气象水文灾害呈现增多增强的趋势，其影响日益广泛。然而，针对干旱区极端气象水文事件的研究还十分有限。为此，本文基于西北干旱区1961—2009年的逐日降水和气温的气象站点数据，定义了适合西北干旱区的八个极端降水指标和五个极端降雪指标，利用旋转EOF分析方法和线性趋势分析方法，研究了气候变化背景下，西北干旱区的极端降水和极端降雪事件的时空变化特征。在此基础上，选取了西北干旱区四个日平均径流数据较完整的山区流域，挑选了独立的径流事件序列中的年最大值和基于某个阈值以上的洪峰，基于这些洪峰定义了八个洪水指标，分析了这些洪水指标的变化趋势。通过上述的分析，结合四个山区流域的逐日降水和平均气温的格网数据，以及其出山口水文站的日平均径流数据，利用灰色关联度方法分析了这几个流域的极端降水指标与洪水指标之间的动态相关性；针对这几个山区流域的洪水高发月份，定义了两个能反映径流事件特征的径流变量以及八个对径流事件有贡献的降水和气温指标，建立了径流指标与降水和气温指标之间的多元线性回归模型，分析了降水和气温对径流变化的影响，并讨论了冰川覆盖率对径流的调控作用。通过上述研究，主要得出了以下结论：（1）从季节上来看，西北干旱区的极端降水指标在春秋冬三个季节无显著的变化趋势，在夏季为普遍增长趋势，且大雨阈值以上降水日数（DPh：大降水日数）、大雨阈值以上降水强度（IPh：大降水强度）、大雨阈值以上降水量（PTh：大降水量）和大雨阈值以上降水量占总降水量的比重（PTh/PT：大降水量占总降水量的比重）的线性增长趋势都通过了95%置信水平上的显著性检验；对比各个降水指标的变化趋势发现，暴雨阈值以上降水强度（IPt：强降水强度）和大雨阈值以上降水强度（IPh）的变化趋势比暴雨阈值以上降水日数（DPt：强降水日数）和大雨阈值以上降水日数（DPh：大降水日数）更显著，尤其夏季大雨阈值以上降水强度（IPh）的增长幅度在南疆的西部、中天山地区和北疆准格尔盆地的西部地区达到了584%/10a。由此可见，大雨和暴雨强度的变化，尤其是夏季大雨强度的变化是极端降水事件显著变化的主要原因，也是西北干旱区降水增加的主要原因。（2）除HSE（大雪事件次数）外，其余极端降雪指标——DHS（大雪日数）、MASD（最大一日降雪量）、MASE（最大一次事件降雪量）和MDSE（最大连续降雪日）在北疆整个区域尺度上都有显著的增长趋势，并通过了95%的置信水平上的显著性检验；并且从1993年以后，DHS、MASD、MASE和MDSE的值都大于其相应的区域平均值，这表明，20世纪90年代初以来，北疆的极端降雪事件增多增强，北疆以极端降雪事件增加增强为标志的降水变化是其气候显著变化的主要特征之一。在大西沟—小渠子和奇台地区，所有极端降雪指标均呈增长趋势，这可能是日降雪量超过6毫米和累积降雪量超过30毫米的降雪事件增多引起的。（3）在开都、疏勒和黑河山区流域，大部分的洪水指标呈增长的趋势，在玛纳斯河山区流域，大多数洪水指标均呈减小的趋势。由此可见，在无冰川补给或者冰川补给很少的流域（如开都河、疏勒河、黑河山区流域），洪水风险增加，在有冰川补给的流域（如玛纳斯河山区流域），洪水风险减小，冰川调节洪水的能力增强。（4）通过研究西北干旱区四个山区流域的极端降水指标与该流域的洪水指标之间的动态相关关系发现，四个流域均未发生强降水事件，而大降水指标与洪水指标之间的动态相关性很强；玛纳斯河、开都河、疏勒河和黑河的山区流域，与洪水指标的动态相关性最大的大降水指标分别为PTh和DPh、DPh和PTh、IPh和DPh以及PTh。（5）西北干旱区山区流域的洪水90%以上集中在有冰川融水补给的夏季，而冰川融化又受气温控制。因此本文基于径流事件的概念，为该地区主要几个山区流域建立了径流指标与降水和温度指标之间的多元线性回归模型，可利用降水和气温数据来预测径流事件的变化特征。另外，本文还通过分析气温对径流指标的贡献率在枯水年和丰水年的差值（TCdiff）与冰川覆盖率的关系，讨论了冰川对径流的调控作用。 |
| 英文摘要 | The northwest arid region of China (NAR) is a region which is sensitive to global climate warming on the planet, and consequently, extreme weather and hydrological events occurred more and more in this region due to the increased rainfall, significant changes in snowfall, accelerated melting of ice and snow, and the increased river runoff. However, studies on extreme meteorological and hydrological events in arid regions are still limited. To study the variations in extreme precipitation and floods, the relationship between extreme precipitation and floods, and to predict floods, the following analysis were done. Firstly, based on the daily precipitation and temperature dataset of weather stations during the period 1961—2009 in NAR, eight extreme precipitation indices and five snowfall indices were defined and analyzed by rotated EOF analysis and linear regression analysis to obtain the variations of extreme precipitation and snowfall events in the NAR under climate change. Secondly, based on the daily average discharge data of four typical upper basins in the NAR, eight flood indices which were defined based on the peak discharges of runoff events were calculated, and then trend analysis were conducted for these flood indices. Thirdly, based on the daily precipitation and temperature grid data and daily average discharge data of these four upper basins, the dynamic correlations between these extreme precipitation indices and flood indices for these upper basins were analyzed by gray relational analysis; and moreover, multiple linear regression models were built for the defined runoff indices which can describe the characteristics of runoff events with the defined precipitation and temperature indices which can describe the characteristics of precipitation and temperature events which occurred during the related runoff events. Finally, some important conclusions were obtained.(1) From the seasonal point of view, the extreme precipitation indices in the NAR showed non-significant trends in spring, autumn and winter, and showed increasing trends in summer, and moreover, the trends in summer DPh (days of heavy precipitation), IPh (intensity of heavy precipitation), PTh (amount of heavy precipitation) and PTh/PT (the proportion of heavy precipitation to total precipitation) were all significant at the 95% confidence level. Comparing the trends in each precipitation index, it was found that the trends in IPt (intensity of torrential precipitation) and IPh were more significant than those in DPt (days of torrential precipitation) and DPh, especially that in IPh was 584%/10a in the western part of southern Xinjiang, the middle Tianshan region and the western Junggar Basin in northern Xinjiang. It can be concluded that changes in the intensity of heavy and torrential precipitation, especially in summer, might the main reason for the significant changes in extreme precipitation events and the main sources of the increase in precipitation in NAR.(2) Except HSE (heavy snowfall events), the remaining four extreme snowfall indices—DHS (days of heavy snowfall), MASD (maximum 1-day snowfall amount), MASE (maximum 1-event snowfall amount) and MDSE (maximum consecutive snowfall days) experienced significant increasing trends at the 95% confidence level over the whole Northern Xinjiang; and since 1993, the values of DHS, MASD, MASE and MDSE were all larger than the annual average values of these indices during studied years, which indicates that the climate changed rapidly since the early 1990s in northern Xinjiang. The change of precipitation process marked by the increase of extreme snowfall events in the northern Xinjiang is one of the main features of its significant climate change. In the Daxigou-Xiaoqizi and Qitai areas, all the extreme snowfall indices increased, and it is possibly caused by the increases of these snowfall events whose daily snowfall was > 6 mm or whose accumulated snowfall amount was > 30 mm.(3) Increasing trends were found for most of the flood indices in the upper basins of Kaidu River, Shule River and Hei River, while decreasing trends were found for most of the flood indices in Manas River Basin. It can be concluded that in the upper basins without glaciers or with low glacier coverages (such as the upper basins of Kaidu River, Shule River and Hei River), the risk of floods increased; while in the basins with high glacier coverages, the risk of floods decreased, which the power of glaciers to regulate floods increased.(4) By studying the dynamic correlation between extreme precipitation indicators of four upper basins in the NAR and the flood indices of these upper basin, it was found that none of the four basins experienced torrential precipitation events; and there was strong dynamic correlation between heavy precipitation indicators and flood indicators. For the upper basins of Manas river, the precipitation indicators which had strongest dynamic correlation with these flood indices are PTh and DPh; for the upper basin of Kaidu river, those are PTh and DPh; for the upper basin of Shule rivers, those are DPh and PTh; and for the upper basin of Hei rivers, those are IPh, DPh and PTh.(5) More than 90% of floods in the upper basins of rivers in the NAR distributed in summer when glacier meltwater supplies are available, and the glacier melting is controlled by high temperature. Thence, based on the definition of runoff events, a multiple linear regression model for runoff indices with precipitation and temperature indices were established for the studied upper river basins in the NAR, which makes it possible to interpret the characteristics of runoff events using precipitation and temperature datasets. Additionally, regulation of glaciers on runoff was discussed through analyzing the differences of temperature contributions to runoff indices between dry and wet years (TCdiff) against glacier coverages. |
| 中文关键词 | 极端降水 ; 极端降雪 ; 洪水 ; REOF分析 ; 冰川 |
| 英文关键词 | extreme precipitation extreme snowfall floods rotated EOF analysis glaciers |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288131 |
| 推荐引用方式 GB/T 7714 | 王少平. 西北干旱区极端降水的变化及其与山区洪水的关系[D]. 中国科学院大学,2018. |
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