摘要
黄河源区作为黄河重要的水源涵养区,其干湿变化及趋势严重影响下游农业生产过程及数亿人的饮水安全。该研究利用黄河源区土壤湿度观测网长期的观测数据,通过计算多层土壤湿度异常百分比指数(soilmoistureanomaly percentageindex,SMAPI),获取近10a间黄河上游最重要的水源涵养区-玛曲地区的干旱演变特征,并以此为依据对5种典型干旱指数:帕默尔干旱指数(palmer drought severity index,PDSI)、自校准帕默尔干旱指数(self-calibration palmer drought severity index,SC-PDSI)、标准化降水指数(standardized precipitation index,SPI)、标准化降水蒸发指数(standardized precipitation evapotranspiration index,SPEI)和地球重力场-气候试验卫星(gravity recovery and climate experiment,GRACE)反演的陆地储水量异常产品在该地区的适宜性进行了综合评价。结果表明:黄河源区干湿交替变化大致划分为5个过程,其中,2011年秋季出现了表层非常湿润的状况(0.05 m处的SMAPI为52%),这段时期为整个研究时段期间上最为湿润的时期,而2012年1月-2016年6月期间出现了自2008年7月-2017年6月以来最为稳定、持续时间最长的干旱时期,且2015年8月期间部分土壤层结出现了严重干旱状态(0.05、0.10、0.20m的SMAPI分别为-47%、-43%、-41%)。干旱指数评估结果表明:在评估黄河源区的干旱变化特征时,最宜采用SC-PDSI指数,但针对典型干旱/湿润时期的统计分析结果显示,按照现有的干旱等级划分标准,SC-PDSI指数将过高估计干旱的程度,从而使得"轻微干旱"状态"严重化","中度干旱"状态"极端化",应重新制定SC-PDSI干旱等级划分方案。对相同的时间尺度而言,SPEI和SPI两种指数在变化趋势上相似,但SPI较SPEI更适用于黄河源区干旱程度的评估。遥感陆地储水量异常在该区域与土壤湿度异常百分比指数呈现显著相关性(r=0.37,P<0.01),就统计结果而言,陆地储水量异常对干旱的刻画能力仅次于SC-PDSI,优于SPI、SPEI和PDSI。因此,陆地储水量异常可以作为一种无需气象观测资料且能够表征黄河源区干旱的参考指标之一。需要指出的是,对青藏高原地区的黄河源区而言,各干旱指数均具有一定的适用局限性,特别是利用现有干旱等级划分旱涝事件的强度等级时仍然存在较多的不确定性。
As the most important catchment of the Yellow River, the drought of the source region of the Yellow River has a significant impact on water resources regulation and ecological environment protection. Although, as a foundation of drought estimates, drought index is capable of describing the intensity, range and starting and ending time of the drought, due to differences of the methodology and background in drought indexes, widely used drought index based on meteorological measurements cannot precisely depict the temporal and intensity characteristic of the drought, evaluating the performance of drought index is essential for drought monitoring and diagnosis. Therefore, soil moisture anomaly percentage index(SMAPI) from a well-instrumented regional-scale soil moisture and temperature monitoring network was identified as the reference of drought index to evaluate five droughts indices-the palmer drought severity index(PDSI), the self-calibrating palmer drought severity index(SC-PDSI), standardized precipitation index(SPI), standardized precipitation evapotranspiration index(SPEI), and monthly land water storage anomaly from gravity recovery and climate experiment(GRACE). The time series of SMAPI showed that during the whole study period there were five stages which were respectively from July 2008 to August 2009(the first stage), September 2009 to March 2011(the second stage), April 2011 to December 2011(the third stage), January 2012 to June 2016(the fourth stage) and from July 2016 to June 2017(the fifth stage). Results indicated against the first stage, two distinct features of SMAPI were presented with an initial increasing trend and increasing again after a decreasing trend at the end of the first stage. At this stage, a slight drought event occurred in the cold winter of 2008(SMAPI=-17%). Against the second stage, except August of 2010, the SMAPI showed a slowly drying trend, especially at the end of 2010, that all SMAPI of different soil depths decreased to approximately-20% indicates during this period there was a stable drought event. Against the third stage, the study area presented a clear wetting process, and in the fall of 2011 occurring an extremely wetting event, which was the most humid month overall phases(SMAPI at 0.05 m was equal to 52%). The drought event with the longest duration was from January 2012 to June 2016(the fourth stage), and in accordance with minimum SMAPI(SMAPI at 0.05 m, 0.10 m, and 0.20 m were equal to-47%,-43%,-41%, respectively) at three soil depths, the severest drought occurred in August 2015. The drought began to mitigate in the last stage, and concurrent SMAPI increased to larger than 5% in January 2017. The estimation of the five indexes indicated SC-PDSI had a similar trend with PDSI, but SC-PDSI showed a more stable characteristic in comparison of PDSI, and thus SC-PDSI performed the optimum effect in the Yellow River source region, but according to an existing classification of drought, it would generally overestimate the intensity of drought event, and the future work should thus need to define a new classification of drought for SC-PDSI. Against an identical time-scale parameter k, the time series of SPI and SPEI showed similar characteristics, but SPI was more suitable for assessing the intensity of drought in this study region. But when air temperature was less than 0, it would result in a large error in study area. Terrestrial water storage anomaly from gravity recovery and climate experiment, as a space-borne remote sensing observation product, showed a significant agreement with the SMAPI(correlation coefficient was 0.37, P<0.01). Relevant research should primarily focus on improving the existing drought assessment approach or developing a more suitable drought index for the source catchment of the Yellow River in future.
作者
王作亮
文军
李振朝
韩博
刘蓉
王欣
Wang Zuoliang;Wen Jun;Li Zhenchao;Han Bo;Liu Rong;Wang Xin(Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China;College of Atmospheric Sciences,Plateau Atmosphere and Environment Key Laboratory of Sichuan Province,Chengdu University of Information Technology,Chengdu 610225,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),School of Atmospheric Sciences,Sun Yat-sen University,Zhuhai 519028,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2019年第21期186-195,共10页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金重点项目(41530529)
国家自然科学基金培育项目(91737103)
关键词
土壤湿度
干旱
降水
黄河源区
适宜性评估
soil moisture
drought
precipitation
source region of Yellow River
suitability evolution
