基于Penman-Monteith法的黑河流域玉米农田蒸散特征研究

Evapotranspiration of Maize Field in Irrigation Area in Heihe Middle Reaches Using the Penman-Monteith Method

为研究黑河流域玉米农田蒸散(ET)特征,以黑河中游农田生态水文试验站气象观测资料为基础,通过彭曼法(P-M)计算得到农田参考蒸散量,与涡度相关系统实测蒸散量对比分析,结果表明,在玉米生长期内,2种方法得到的结果具有良好的线性相关性,彭曼法可以精确的反应农田实际蒸散量。利用彭曼法计算结果分析表明,试验地在玉米生长季,ET日变化呈现早晚低,中午高的变化特征,但受当地气候影响,正午蒸散值有略微的下降,出现具有"蒸散高地"现象的"单峰型"变化曲线;最大日峰值出现在大喇叭口期,为0.39 mm/h,最低日峰值出现在完熟期,为0.19mm/h。ET季节变化动态明显,与农田灌溉、降雨季节分布以及玉米叶面积指数密切相关;太阳辐射、空气温度、空气相对湿度和风速等因子共同影响农田蒸散;5月的蒸散值维持在一个较低的水平,仅占玉米生长季蒸散总量的5.0%,6月蒸散剧烈增加,7月达到最高,8月仍维持在一个高水平,6-8月蒸散量占玉米生长季蒸散总量的82.0%,9月蒸散量急剧下降,仅占玉米生长季蒸散总量的13.0%。

To study the evapotranspiration( ET) of maize field in irrigation area in Heihe Middle Resches,an ecological experimental station of eco-hydrology research on maize field was established in Zhangye Oasis in irrigation in Heihe Middle Reaches. The meteorological data provided by this station were used to calculate evapotranspiration by the Penman-Monteith equation( P-M). Compared to ET measured by eddy covariance system( EC),It draw a conclusion that two results had a good linear correlation in the whole growing period and that the PenmanMonteith method could response farmland quantity of actual evapotranspiration accurately. Results gotten from P-M showed that the diurnal variation of ET in this agroecosystem could be graphed as a line with a single-peak which occurred high in the noon and low in the morning and evening as following the growing stage; while ET declined slightly and a plateau in the evapotranspiration occurred during the middle part in the day affected by local climate.Seasonal ET highest peaks in bell-mouthed stage( 0. 39 mm / h) and lowest peaks in maturity period( 0. 19 mm / h).ET changed as the seasons changed obviously and it was closely related to irrigation,precipitation seasonal distribution and maize leaf area index. The solar radiation,air temperature,relative humidity and wind speed affected the ET together. In May,ET maintained a lower level with the percentage of total ET of 5. 0%. In June,ET increased sharply and then up to the maximal value in July and maintains the higher level the whole August. It accounted for82. 0% of the total during June to August. ET decreased rapidly in September,accounted for only 13. 0% of the total evapotranspiration in maize growth season.