榆林市参考作物蒸发蒸腾量随时间序列变化的规律

The law of reference crop evaporation's variation with time series in Yulin

根据选取的榆林市5个代表气象站1985-2006年22年的气象资料,应用FAO-Penman-Monteith公式计算了各站历年各月的参考作物蒸发蒸腾量（ETo）,并分析了ETo随时间序列变化的规律。结果表明：榆林市5个代表站5、67、月份的ETo之和占全年的比例最大; 各代表站的ETo主要在1996年以后随时间呈极显著增加趋势,在1985-1996年,定边、横山的ETo随时间呈极显著减少的趋势,绥德、榆阳、神木的ETo随时间呈极显著增加的趋势,但是增加的趋势线斜率均小于1996年以后的趋势线斜率; 榆林市的ETo与平均气温、日照时数、风速呈极显著的正相关,与相对湿度呈极显著的负相关; ETo与最高气温呈显著正相关,与最低气温除了定边站呈极显著正相关外,与其它各站均呈极显著负相关; 平均气温是影响榆林市ETo变化的主要气象因子。

According to 22 - year weather data from 1985 to 2006 from five selective weather stations in Yulin, FAO - Penman - Monteith method was adopted to calculate the monthly reference crop evaporation （ ETo ） in every station, and to analyze the law of ETo＇s variation with time series. It can be drawn that the sum of ETo in May, June and July in the five stations accounted for the largest proportion of the whole year. After 1996, the ETo in every station showed a trend of increase, which was very significant. From 1985 to 1996, the ETo in Dingbian and Hengshan stations showed a significant decreasing trend with time; and the ETo in Suide, Yuyang and Shenmu stations showed a significant increasing trend, however, the slope of the increase trend line was less than the slop of trend line after 1996. In Yulin, the ETo had a significant positive correlation with the average temperature, sunshine hours and wind speed, while the relative humidity had a significant negative correlation. ETo and high temperature were in positive correlation; Apart from Dingbian, in other stations the minimum temperature had a significant negative correlation with ETo. The average ternperature is the main reason for ETo＇s change in Yulin from 1985 to 2006.