白洋淀西部平原参考作物腾发量长期变化趋势及其成因

Trends of Reference Evapotranspiration and the Main Causes from 1955 to 2018 in Dianxi Plains

参考作物腾发量ET_(0)是作物需水量计算的关键因子,是水循环研究的重要因素。研究气候变化背景下参考作物腾发量长期变化规律,阐明其主要成因,可为应对气候变化对农业产生的影响和区域水资源规划管理提供基础。采用FAO推荐的Penman-Monteith公式计算了淀西平原1955-2018年逐日ET_(0),分析了ET_(0)及其构成项辐射项ETrad和空气动力学项ET_(aero)的长期变化规律,利用Mann-Kendall方法分析了ET_(0)及其主要驱动因素平均温度、湿度、日照和风速的变化趋势,并利用偏相关分析获得ET_(0)和主要驱动因素之间的关系。结果显示:淀西平原多年平均ET_(0)为1070.5 mm,ET_(0)下降趋势明显,倾向率为-19.5 mm/10 a。多年平均ETrad和ET_(aero)占ET_(0)的百分比分别为61.2%和38.8%。从4月至10月以辐射项为主,辐射项占参考作物腾发量的53.0%~80.2%,其他时段空气动力学项占的比例大些。淀西平原平均温度呈显著上升趋势,温度倾向率为0.23℃/10 a;日照时数、平均风速和相对湿度倾向率分别为-138.85 h/10 a、-0.09 m/s/10 a和-0.58%/10 a。从偏相关分析来看,参考作物腾发量与平均温度、日照时数、平均风速呈显著正相关,相关系数分别为0.909、0.608和0.534,与相对湿度呈显著负相关,相关系数为-0.371。淀西平原参考作物腾发量呈显著下降趋势,主要因为日照时数和风速的显著下降所致。

The long-term trends of reference evapotranspiration(ET_(0)) and the main caused in Dianxi Plain were studied in this paper,which provides the basis for dealing with the impact of climate change on agriculture and water resources planning and management.The daily ET_(0) during 1955-2018 was calculated by using the Penman-Monteith formula recommended by FAO,the variation regularity of ET_(0) and radia⁃tion term(ET_(rad))and aerodynamics term(ETaero)were analyzed.The trends of mean temperature,humidity,sunshine and wind speed,which are the main driving factors of ET_(0) were analyzed by using the Mann-Kendall method.The relationship between ET_(0) and main driving factors was obtained by partial correlation analysis.The results show that ET_(0) decreases obviously in 1955-2018,its decline rate is-19.5 mm/10 a.The average annual ET_(0) is 1070.5 mm.The annual average ET_(rad) and ETaero as the percentage of ET_(0) is 61.2%and 38.8%respective⁃ly.The annual average daily ET_(0) shows a single peak curve and its average value is 2.9 mm/d.ET_(rad) accounted for 53.0%~80.2%is dominated from April to October,while ETaero accounted for a larger proportion in other periods.The average temperature shows a significant upward trend;its decline rate is 0.23℃/10a.The sunshine,average wind speed,relative humidity all show an obvious downward trend in Dianxi Plain,the decline rates are-138.85 h/10 a,-0.09 m/s/10 a and-0.58/10 a respectively.ET_(0) is linearly positively correlated with the average temperature,sunshine hours,and average wind speed and the correlation coefficients are 0.909,0.608,and 0.534,respectively.ET_(0) is lin⁃early negative with relative humidity,and the correlation coefficient is-0.371.It is mainly due to the significant decrease of sunshine and wind speed that ET_(0) shows a significant downward trend in Dianxi Plain.