【作者】 张莹；

【导师】 杜海波；

【作者基本信息】 东北师范大学 ， 自然地理学， 2022， 硕士

【摘要】 随着全球变暖加剧,强降水事件的频次和强度都有所增加。但是,降水没有固定的持续时间,会形成不同持续时间的强降水,往往会导致严重的洪涝灾害,造成严重的社会经济损失。因此,以不同的持续时间角度来分析持续强降水事件是研究降水变化的复杂性的一个必要手段。长白山是东北地区重要的水源地,长白山的降水尤其是强降水对气候变暖的时空响应是区域水资源研究的重点。但是,降水的空间异质性较强,站点观测数据或粗空间分辨率数据对降水的区域格局分析存在局限性,需要通过模型模拟高空间分辨率的降水数据进行强降水的时空变化研究。因此,本研究通过WRF模型(The Weather and Forecasting Model)模拟了长白山区1975-2020年逐日降水数据,模拟的空间分辨率达到5 km,在此基础上分析了长白山区不同持续时间(1天、2天、3天、4天以及≥5天)的持续强降水(≥10mm/天)事件(persistent heavy precipitation,PHP)及极端持续强降水事件(extreme persistent heavy precipitation,EPHP)的发生频次、强度及两种降水事件对总降水量贡献率的时空变化特征。研究结果和结论主要包括以下几个方面:(1)1975-2020年期间,长白山区不同持续时间的PHP的频次及强度的多年均值在空间上均呈现出中西部较多,图们江子流域较少的分布格局,且PHP发生频次较多的地区其强度也更大,集中在持续2-3天事件。近50年长白山区PHP频次及强度都呈现出上升趋势,且部分强度指标显著(p<0.05)上升,而松花江流域上游变化趋势较小。整个研究区内PHP频次增长较快的地区PHP强度的增长趋势也相对较大,二者变化趋势在空间上具有一致性。(2)近50年长白山EPHP事件主要发生在松花江和鸭绿江子流域,特别是持续3天及其以上的EPHP事件,而持续2天的EPHP更多地发生在图们江子流域。高强度的EPHP主要发生在鸭绿江子流域和松花江子流域的中北部,而整个图们江子流域的强度较小。长白山区不同持续时间的EPHP事件的频次和强度均呈现出上升趋势,其中持续3天的EPHP事件的频次和强度的增加在图们江子流域(20%/10a和27%/10a)和松花江子流域(12%/10a和13%/10a)都达到了95%的显著(p<0.05)水平,但鸭绿江子流域的变化不显著。(3)近50年长白山区多年平均总降水量在整体上均呈现出西多东少的空间分布特征,且降水量集中在600-1200mm之间;长白山区各子流域总降水量均呈上升趋势,且上升趋势差异较小。除持续2天的强降水事件外,其他持续时间的PHP及EPHP对总降水量的贡献率均呈现出上升趋势,特别是持续3天及总的强降水事件。空间分布方面,大部分区域的PHP和EPHP的贡献率均呈上升趋势(松花江子流域上游中部及鸭绿江子流域北部除外),且松花江子流域上游北部、鸭绿江子流域南部及图们江子流域上升趋势显著(p<0.05),但不同子流域不同持续时间强降水事件贡献率变化趋势分布格局各有不同。总之,在气候变暖背景下,近50年长白山区降水结构发生了明显变化,强降水逐渐增多,而且强降水朝着持续性和极端性发展。因此,持续强降水和极端持续强降水对总降水量贡献率也在增加,特别是松花江子流域和鸭绿江子流域的中下游以及整个图们江子流域。同时,长白山自然保护区、鸭绿江子流域以及松花江中北部持续强降水和极端持续强降水发生频次多且强度也大,是这些区域及其下游形成洪涝灾害的原因之一。本研究对进一步理解气候变暖背景下长白山区降水结构的时空变化以及区域水资源保护具有重要意义。更多还原

【Abstract】 The frequency and intensity of heavy precipitation events have increased under global warming.However,precipitation has no fixed persistent duration,and heavy precipitation has different persistent durations,which will often lead to serious flood disasters and cause serious social and economic losses.Therefore,it is necessary to study the complexity of precipitation change by analyzing the persistent heavy precipitation events with different persistent durations.The Changbai Mountains is an important water source in northeast China,and the spatial and temporal response of precipitation,especially heavy precipitation,to climate warming in Changbai Mountains is the focus of regional water resources research.However,the spatial heterogeneity of precipitation is strong.There are limitations in the analysis of regional patterns of precipitation by station observation data or coarse spatial resolution data.The spatial and temporal variability of intense precipitation needs to be studied by model simulation of high spatial resolution precipitation data.Therefore,in this study,the daily precipitation data of Changbai Mountains from 1975 to 2020 was simulated by the WRF model(The Weather and Forecasting Model).The spatial resolution of the simulation output reached 5km.On this basis,the frequency and intensity of persistent heavy precipitation(≥ 10 mm/day)events(persistent heavy precipitation,PHP)and extreme persistent heavy precipitation(EPHP)events with different persistent durations(1,2,3,4,and ≥ 5 days)in the Changbai Mountains were analyzed.Further,the spatial and temporal variation characteristics of the contribution of the two kinds of heavy precipitation events to the total precipitation were also analyzed.The main research results and conclusions are included as follows:(1)During 1975-2020,the multi-year average frequency and intensity of PHP with different persistent durations in the Changbai Mountains were more in the central and western regions and less in the Tumen River basin.The intensity of PHP was higher in the regions with more frequent occurrences,and concentrated on events lasting for 2-3 days.In the last 50 years,the frequency and intensity of PHP increased in the Changbai Mountains.However,the change was smaller in the upper reaches of Songhua River Basin.Generally speaking,areas with strong increases in the PHP intensity accompanied with large increasing trend in PHP frequency.Therefore,the spatial patterns of change(direction and magnitude)of PHP frequency and intensity are consistent.(2)In the last 50 years,EPHP events mainly occurred in the Songhua River Basin and Yalu River Basin in the Changbai Mountains,especially for EPHP lasting for 3 days or more days.The 2-day EPHP occurred frequently in Tumen River Basin.The high intensity of EPHP mainly occurred in the middle and northern parts of Yalu River Basin and Songhua River Basin.Comparatively,the EPHP intensity of the whole Tumen River Basin was smaller.Both of the frequency and intensity of EPHP events with different persistent durations showed an increasing trend in the Changbai Mountains.The frequency and intensity of 3-day EPHP events increased significantly(p<0.05)in Tumen River Basin(20%/10 aand 27%/10a)and Songhua River Basin(12%/10 a and 13%/10a),but not significant in Yalu River Basin.(3)In the past 50 years,the average annual total precipitation was in 600-1200 mm,with stronger precipitation in the west than that in the east in the Changbai Mountains.The annual total precipitation increased in most parts of the Changbai Mountains,and the difference in the increasing trend was small among the three sub-basins.Except for the 2-day heavy precipitation events,the contribution rates of PHP and EPHP to the total precipitation showed an increasing trend,especially for the3-day heavy precipitation and total heavy precipitation events.In terms of spatial distribution,the contribution rates of PHP and EPHP to the total precipitation increased in most areas(except for the central of the upper reaches of Songhua River basin and the northern part of Yalu River basin).The increasing trends was significant(p<0.05)in the northern part of the upper Songhua River basin,the southern part of the Yalu River basin and the Tumen River basin.The spatial patterns of the contribution rates of heavy precipitation with different persistent durations were different among different sub-basins.In a word,under the background of climate warming,the precipitation structure in the Changbai Mountains has changed significantly in the last 50 years.Heavy precipitation was increasing gradually,and it was developing towards persistence and extremes.Therefore,the contribution rate of persistent heavy precipitation and extreme persistent heavy precipitation to total precipitation was also increasing,especially in the middle and lower reaches of Songhua River basin and Yalu River basin and the whole Tumen River basin.Furthermore,the high frequency and strong intensity of PHP and EPHP in the Nature Reserve of Changbai Mountains,the Yalu River basin,and the central and northern Songhua River basin were one of the reasons for the formation of floods in these areas and their downstream.The findings of this study are of great significance to further understand the temporal and spatial changes of precipitation structure and regional water resources protection in the Changbai Mountains under climate warming.更多还原