中国大陆地区基于太阳辐射经验值计算ET0的适用性研究

太阳辐射是利用FAO推荐的Penman-Monteith(PM)公式计算参考作物需水量(ET_0)的必要参数。为了探究PM公式在辐射数据缺失的条件下,利用FAO推荐的公式及参数获得太阳辐射值(R_(s_c))替代观测值(R_(s_o))在中国大陆地区的适用性,本研究选用了中国大陆112个站点至少15 a的多年月平均观测数据,通过逐点计算分析了R_(s_c)和R_(s_o)的时空差异及二者分别输入PM公式获得的参考作物需水量ET_(0_c)和ET_(0_o)的时空差异。结果表明,R_(s_c)与R_(s_o)存在显著的时空差异性,二者相对差值范围为-2.86～4.41 MJ·m~(-2)·d~(-1),且在4—8月份差异较大;大致以"胡焕庸线"为界,线西北区域R_(s_c)与R_(s_o)的时空差异相对较小,且稳定,线东南区域的时空差异较大,且不稳定。但是,基于二者计算的ET_(0_c)和ET_(0_o)时空差异却不显著,平均只有0.06～0.26 mm·d~(-1)的误差;"胡焕庸线"西北地区的ET_(0_c)和ET_(0_o)绝对差值常年稳定在0.00～0.25 mm·d~(-1),"胡焕庸线"线东南地区则随季节而变化,夏季差异相对较大。在实际的应用中,西北地区全年和北方地区春、秋、冬三季以及长江、珠江流域所覆盖的南方地区在1、2、10、11、12月使用R_(s_c)替代R_(s_o)获得ET_0具有较好的适用性,北方地区的夏季、南方地区的3—9月份使用R_(s_c)计算ET_0则必须研究相应的方法对结果进行矫正,否则会有误差,且偏大。

Applicability of the empirical value of solar radiation in estimation of ET0 in Mainland China

Radiation parameters are essential for calculating reference crop evapotranspiration (ET₀) by using Penman-Monteith (PM) formula recommended by FAO.To explore the applicability of using the FAO recommended formula for radiation parameter (R_{s_c}) instead of observations (R_{s_o}) in PM formula under the condition of lacking radiation parameters, this study used multi-year monthly average observation data of 112 stations, that each station has at least 15 years of data. The spatiotemporal difference between R_{s_c} and R_{s_o}, and ET₀_c and ET₀_o which obtained by PM formula input of R_{s_c} and R_{s_o}, respectively, by point-by-point was analyzed.The results showed that R_{s_c} and R_{s_o} had significant spatial-temporal differences, and the relative difference between them ranged from -2.86 to 4.41 MJ·m^-2·d^-1, which were larger from April to August. Taking Hu Huanyong Line as the boundary,the spatial-temporal difference in the northwest region of the line was relatively small and stable, while the spatial-temporal difference in the southeast region of the line was relatively large and unstable.However, the spatial-temporal difference of the ET₀_c and ET₀_o calculated by R_{s_c} and R_{s_o}, respectively,was not significant, only 0.06~0.26 mm·d^-1.The absolute difference value between ET₀_c and ET₀_o was stable in 0~0.25 mm·d^-1in northwest of Hu Huanyong Line. The difference in southeast region of the line changed with the season, and the difference in summer was relatively large. In actual application, using R_{s_c} instead of R_{s_o} to obtain ET₀ had a good applicability in the northwest region within a year and also the north region in spring, autumn, winter and the Yangtze river-Pearl river basin (the southern region) in months, Jan., Feb., Oct., Nov. and Dec.If R_{s_c} was used to calculate ET₀ in summer of the north region and from March to September of the south region, corresponding methods must be studied to correct the results.Otherwise, there will be relatively large errors.