华北平原参考作物蒸散量时空变化及其影响因素分析

根据华北平原56个气象站1960—2012年逐日气象数据和Penman-Monteith模型计算了各站及区域整体参考作物蒸散量(ET0),利用样条插值法、气候倾向率、累积距平、敏感性系数等方法对华北平原ET0的时空变化及其影响因素进行了分析。结果表明:(1)华北平原多年平均ET0为1071.37mm,空间上呈现高低值相间分布格局,高值中心分布在冀北、鲁中、豫西,而低值中心分布在冀东、鲁南、豫东及豫南等地;(2)近53年ET0呈减少趋势(-12.8mm/10a),山东半岛北部及冀北等地有缓慢增加趋势,其余地区以减少为主;(3)ET0对气温、平均风速、日照时数为正敏感,而对相对湿度为负敏感。平均气温与日照时数敏感系数呈现下降趋势,相对湿度与风速敏感系数表现出上升趋势。ET0对气温和风速敏感度高的区域同时对日照时数和相对湿度敏感度较低;(4)归因分析表明,华北平原ET0的主导因子是日照时数,平均风速次之,相对湿度、最高温度、最低温度对ET0变化影响较小,日照时数主导区域包括冀北、坝上地区、冀中、豫西、豫南、鲁中及鲁西北,平均风速的主导区域为冀南、河南黄河以北、豫中、鲁西北,温度主导区域零星分布于冀北、豫西、山东半岛等地,相对湿度的主导区域主要分布在鲁南、山东半岛。

Spatial and temporal variations of reference crop evapotranspiration and its influencing factors in the North China Plain

Potential evapotranspiration is the theoretical upper limit value of actual evapotranspiration, which constitutes the important parameters for the research of regional thermal balance, water budget, water resources assessment and crop water requirements. Study on regional response of potential evapotranspiration to global climatic changes in China has significance in global hydrological cycling, energy balance and eco-environmental evolution research. Reference crop evapotranspiration(ET₀) as a common parameter is largely an evolution of definition of potential evapotranspiration and with the method of Penman-Monteith Model recommended by Food and Agriculture Organization for computing crop water requirements in 1998, reference crop evapotranspiration could be estimated quickly and accurately. Based on the daily observation data of the 56 meteorological stations in the North China Plain from 1960 to 2012, reference crop evapotranspiration were calculated, then the spatial-temporal variation patterns of reference crop evapotranspiration over North China Plain was analyzed with the methods of linear regression, spline interpolation and accumulative anomaly method. In the meantime, the dominant factors of the ET₀''s variations in North China Plain were quantitatively analyzed by calculating sensitivity coefficients of reference crop evapotranspiration to climate elements and the relative change of the climate elements. The result showed that: (1) Annual reference crop evapotranspiration of north China plain was 1071.37mm and the spatial distribution pattern was high center alternating with low center. The high value reference crop evapotranspiration areas mainly distributed in the northern Hebei, central part of Shandong mountainous region and western regions of Henan, while the low value centers distributed in the eastern regions of Hebei, southern Shandong, eastern and southern regions of Henan province. (2)The reference crop evapotranspiration has decreased obviously in North China Plain during the last 53 years by the rate of 12.8mm/10a, and its decadal variation showed that the decade anomaly consistently decreased. From the perspective of the regional distribution of ET₀ change, the ET₀ of the northern Shandong Peninsular and the northern regions of Hebei province showed a slowly increasing trend, while the ET₀ of the rest areas decreased. (3) The sensitivity coefficients of reference crop evapotranspiration to the daily temperature (S_AT), sunshine hours (S_SH), wind speed (S_WS) were positive values, while the sensitivities coefficients of reference crop evapotranspiration increased slowly, while S_RH and S_WS decreased. There was a corresponding relationship for the sensitivity coefficients of reference crop evapotranspiration, which meand areas of high sensitivity to temperature and wind speed had relative low sensitivity to sunshine hour and the relative humidity. (4)The dominant factors of ET₀ in North China Plain were as follows:sunshine hours and wind speed were the dominant factors caused change of ET₀ in North China Plain, while relative humidity, daily maximum temperature and minimum temperature contributed less to the change of ET₀. Sunshine hours was the determining factor in the change of ET₀ in many regions of the northern and the central regions of Hebei province, Bashang District of Hebei Province, the southern and western region of Henan province and the central regions of Shandong province.The regions affected by wind speed expanded across the Southern region of Hebei province, southern Henan Province and the north of the Yellow River in Henan Province, the central regions of Henan province, northwestern regions of Shandong province.The meteorological stations affected by temperature scattered in the west of northern Henan Province, western region of Henan province and Shandong peninsula, while relative humidity only had significant influence on the ET₀ of the southern regions of Shandong province and Shandong peninsula.