%0 Journal Article %A WANG Biao %A ZENG Xinmin %A LIU Zhengqi %A ZHOU Xiaolin %A SUO Jingdong %T Estimation and Variation Characteristics of the Reference Crop Evapotranspiration in Northwest China During 1956-2011 %D 2016 %R 10.11755/j.issn.1006-7639(2016)-02-0243 %J Journal of Arid Meteorology %P 243-251 %V 34 %N 2 %X

Based on the daily meteorological data at 42 weather stations in Northwest China from 1956 to 2011, the reference crop evapotranspiration (ET0) was estimated by using Penman-Monteith (P-M) equation, and the temporal and spatial distributions of ET0 in Northwest China were analyzed. The mutation and period of ET0 during 1956-2011 were studied by using Mann-Kendall (M-K) test and Morlet wavelet analysis methods, and the correlation between ET0 and main meteorological factors was done by using the multivariable linear regression method. The results are as follows: (1) The monthly and seasonal changes of ET0 in Northwest China were obvious, the value of ET0 in July was the maximum, while that in December was the minimum, and that in summer, spring, autumn and winter decreased in turn. (2) In the past 56 years, the annual average ET0 in Northwest China reduced significantly, and the seasonal difference was significant, the trends of average ET0 in spring, summer and autumn decreased, and the decreasing rate in summer was the biggest, while the average ET0 in winter increased slowly. (3) The maximum ET0 was located in Kumul to Hotan area. (4) The decreasing mutation of ET0 in spring, summer, autumn and the whole year appeared in the early of the 1980s, and that occurred respectively in 1984, 1986, 1981, 1980, while that in winter mutated in 1995. The annual average ET0 in Northwest China during 1956-2011 had 2-3 years obvious periods and 6 years quasi-periods. (5) The ET0 were positive correlated with wind speed at 2 m and sunshine duration, while that was negative correlated with relative humidity and mean surface air temperature, and the correlation between the ET0 and air temperature was weak. Therefore, the rising of air temperature and relative humidity, and the decreasing of sunshine duration and wind speed caused the ET0 reducing in Northwest China during 1956-2011. The root mean square error considering the above four climatic factors was the minimum in all multitiple linear regression models. In general, the decreasing of ET0 was caused by the variation of four meteorological factors.

%U http://www.ghqx.org.cn/EN/10.11755/j.issn.1006-7639(2016)-02-0243