Knowledge Resource Center for Ecological Environment in Arid Area
| 气候变化下区域干旱时空格局与植被动态响应特征 | |
| 其他题名 | Exploring the spatiotemporal variability of regional drought and unveiling its linkage to the responsing characteristics of vegetation danymics under climate change |
| 卢洪健 | |
| 出版年 | 2015 |
| 学位类型 | 博士 |
| 导师 | 莫兴国 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 干旱是世界范围内循环往复发生的一类自然灾害，具有出现缓慢、持续时间长和空间范围广等特点。干旱的影响复杂而深远，横跨多个经济部门。植被对干旱的响应减缓植物生长，降低植被绿度、生物量和生产力等。中国盛行季风气候，属易旱多旱区；近年来，伴随着全球气候暖化，区域干旱呈现更为频发的态势。干旱无法避免，只有在掌握其时空演变格局的基础上，提升监测、预报与预估能力，达到减缓影响与规避风险的目的。 本文基于气候干旱指数（PDSI、SPI和SPEI）、植被遥感NDVI和地理信息等数据，采用线性回归、M-K检测、EOF分解和游程理论，首先对华北平原和东北地区近54年干旱时空格局进行较详尽的分析；结合相关分析，阐明1982-2012年植被活动对干旱时间尺度的响应特征，探讨植被干旱脆弱性的主要控制因素。同时，借助数据挖掘技术-分类与回归树，构建基于多源（气候、遥感、生物物理）数据的区域植被集合干旱指数（Combined Vegetation Drought Index, CVDI）。此外，联合CMIP5的气候变化数据，分析不同典型浓度路径（RCP）下中国21世纪干旱概率与特征的变化，分离降水和温度变化对区域干旱趋势的相对贡献，比较两个地区干旱特征对气候变化的响应差异。主要研究结果如下： （1）1960-2012年，对华北平原而言，降水减少导致北部约7%的地区干旱显著加强，而降水和温度联合效应导致约40%的地区干旱显著加强。干旱频率总体上为北高南低的格局，但极端和严重干旱频率在中部和南部也较高，升温使极端和严重干旱频率以及空间范围显著增加。对东北地区来说，降水单独变化致使北部干旱减弱，而南部干旱加剧。升温不仅拉长干旱持续时间，而且激化干旱强度，系北部干旱加剧的主导因素；降水和温度联合变化的效应导致约56%的地区干旱显著加剧。时间尺度对区域干旱趋势影响很大，对空间格局影响不甚明显。 （2）华北平原干旱对春季植被活力的影响强于夏季，对北部的影响强于南部。虽然植被动态总体上对长期干旱的响应更明显，但局部和季节差异非常明显，北部植被响应干旱的时间尺度较南部的短。生长季水量平衡是其植被干旱脆弱性的主导因素，但山地和丘陵旱地除外。在东北地区，干旱对草地和耕地植被活力的影响比林地的强；林地只对长时间尺度的干旱响应，而其他土地覆盖类型对短期和长期干旱的响应都较强，最强的时段为6-7月，而草地在9月对干旱也很敏感。降水是植被干旱脆弱性的主要控制因子，干旱脆弱性随海拔升高而加重；森林干旱脆弱性与年降水量呈非线性关系，降水量700 mm的地区干旱脆弱性最高。 （3）整合不同时间尺度的SPEI/SPI有助于提升CVDI的预测精度。春季CVDI以整合12、24个月SPI和SPEI以及植被遥感指标等的精度最高，相对误差和相关系数为0.42和0.85；夏-秋季CVDI以整合3、12个月SPI和6、24个月SPEI等的效果最好，相对误差和相关系数为0.46和0.85；测试数据对CVDI具有相似的模拟精度。计算华北平原2001-2012年1km水平的CVDI，并分析其干旱监测效果，发现CVDI识别局地植被干旱胁迫和追踪干旱时间演化的能力要优于单独基于气候的干旱指数。分析县级水平作物产量与CVDI表征的干旱程度之间的关系，证明CVDI在评估农业干旱影响方面具有一定的优势。 （4）RCP4.5情景下，2006-2050年和2055-2099年中国严重干旱以上频率相当于基准期（1961-2005年）的2和3倍，RCP8.5下约为2和5倍，极端干旱频率明显增加，轻微和中等干旱将成常态化。与基准期相比，RCP4.5和8.5情景下，2055-2099年干旱持续时间平均延长1.8和3.6个月，平均干旱强度增加13.4%和25.6%。RCP4.5和8.5情景下，降水和温度联合变化导致2080-2099年中国干旱化面积达40%和65%。升温导致蒸散需求剧烈增加，不仅强化南方地区的干旱趋势，还将使降水增加的大多数北方地区向干旱化气候反转。华北平原的干旱状况与全国水平相当，东北地区稍弱。 研究厘清了降水和温度变化对华北平原和东北地区干旱时空格局的影响，阐明了植被动态对区域干旱的响应特征，首次揭示了区域植被干旱脆弱性的控制因素。构建的集合指数具备开发气候变化下近实时植被干旱胁迫监测工具的潜力；不考虑适应性对策的情况下，中国在21世纪很可能将面临广泛的农业干旱风险。 |
| 英文摘要 | Droughts are recognized as an insidious and recurring natural hazard, which occur in virtually all climatic regimes and are typically characterized by a slow-onset, long duration and extensive spatial extent. Drought usually produces a complex and far-reaching web of impacts that ripple through many sectors of the economy. The response of vegetation to drought might decelerate plant growth and reduce vegetation greenness, biomass and productivity. China, in which prevailing dominantly a monsoon climate, is drought-prone and has been subjecting to intermittent droughts since human civilization began. Furthermore, severe droughts are more frequently perceived in recent decades, keeping pace with the undoubted global warming. Although droughts are ineluctable, what we can do is to mitigate impacts and evade relevant risks by improving the capabilities of monitoring, forecasting and projection of regional drought based on the understanding of its spatial patterns and temporal evolution. In this study, firstly, several popular climate-based drought index (i.e. the Palmer Drought Severity Index, PDSI; the Standardized Precipitation Index, SPI; and the Standardized Precipitation Evapotranspiration Index, SPEI), satellite-based remote sensing vegetation metric (Normalized Difference Vegetation Index, NDVI) as well as geographic information (e.g. land cover, DEM) were calculated or extracted for North China Plain (NCP) and Northeast China (NEC), and then the spatiotemporal variability of regional drought during last 53 years were analyzed by means of various methods, including linear regression, Man-Kendall trend detection, Empirical Orthogonal Function and the run of theory. To explore the response of vegetation activities to regional drought variability, relationships between annual fluctuation of NDVI and different time-scales SPEI/SPI were conducted for each month in growing season from 1982 to 2012, and the governing factors of vegetation vulnerability to drought were identified. After then, the Combined Vegetation Drought Index (CVDI), aiming at monitoring regional and local vegetation stresses specially incurred by drought, was constructed by data miming technique, namely Classification and Regression Tree based on multi-sources datasets (climate, satellite and biophysical). Moreover, using output form a suite of general circulation model (GCM) simulations from phase 5 of the Coupled Model Intercomparison Project, projected twenty-first century drought characteristics and drying trend in China under two different Representative Concentration Pathway (RCP) were investigated by PDSI and SPEI. In particular, the relative contributions of changes in precipitation and temperature to regional drying patterns were isolated, and the differences in response of drought to climate change for NCP and NEC were illustrated. The main results and findings of this study are listed as follows: (1) For NCP, drought severity had increased significantly solely induced by precipitation with an area of 7% in the northern part during 1960-2012, but drying trend were detected out for 40% area of the whole NCP as a result of the combined effects of changes in precipitation and temperature. In general, drought occurrences in northern part were more frequent than in southern part of NCP, but extreme and severe droughts were also regularly-revisited in central and southern regions. While only considering change in precipitation, it was found that drought in the north of NEC had eased and that in southern part had been aggravated significantly in last five decades. However, the increasing temperature had not only lengthened the duration, but also exacerbated the intensity of regional drought events, and the combined effects of simultaneous changes in precipitation and temperature had led to a drying trend of 56% areas of whole NEC. It was also found that temporal trends of regional drought are different among time-scales, while spatial patterns always si |
| 中文关键词 | 干旱 ; 时空格局 ; 植被动态 ; 集合指数 ; 气候变化 |
| 英文关键词 | Drought Spatiotemporal patterns Vegetation dynamic Combined drought index Climate change |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院地理科学与资源研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287496 |
| 推荐引用方式 GB/T 7714 | 卢洪健. 气候变化下区域干旱时空格局与植被动态响应特征[D]. 中国科学院大学,2015. |
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