三江源温性草原蒸散量计算方法的比较

Comparative study on calculation methods of warm steppe's evapotranspiration in the source region of Three Rivers

【目的】对比分析了三江源温性草原蒸散量的计算方法,为牧区蒸散量的合理使用提供依据。【方法】以小型自动气象站气象观测资料为基础,采用FAO Penman-Monteith(FAO P-M)、Penman1948(P-48)、Priestley-Tay-lor(P-T)和FAO Penman 1979(F-79)4种不同方法,估算了三江源温性草原参考作物蒸散量,并对计算结果进行了对比分析。【结果】三江源温性草原的参考作物蒸散量季节分布极不均匀,表现出春季、夏季、秋季、冬季依次减小的趋势。并且FAO P-M公式的计算结果与其他3种方法(P-48、P-T和F-79)的计算结果呈正相关,但与F-79公式计算结果间差异不大,与另两种方法计算结果间的差异显著。通过偏差分析可知,P-48公式计算的结果偏大,P-T公式计算的结果偏小,造成偏差的主要原因是4种模型各自选用了不同的辐射项和动力项。【结论】在利用气象数据计算蒸散量的过程中,要根据当地需要采用不同的公式。在三江源温性草原,可采用F-79修正式代替标准的FAO P-M公式计算参考作物蒸散量。

[Objective] Comparative study on calculation methods of warm steppe＇s evapotranspiration in the source region of three rivers was conducted to provide basis for rational use of evapotranspiration. [Method] Based on meteorological data of HOBO Weather Station,different methods were used to calculate the reference evapotranspiration of grassland in the source region of three rivers （Yellow river,Jinsha river and Lanchang river）. [Result] The analysis showed that dynamic variation of warm steppe＇s evapotranspiration in the source region of three rivers was different. Seasonal reference evapotranspiration was in a sequence of springs〉ummer〉autumn〉winter. And the Penman 1948,Priestley Taylor formula and the FAO Penman 1979 were all correlated well with the FAO Penman-Monteith. The FAO Penman 1979 was in agreement with FAO Penman-Monteith estimates, but Priestley-Taylor and the Penman 1948 estimates were obviously deviated from FAO Penman-Monteith estimates. The cause of the deviation was the difference in calculating the radiation and dynamics. [Conclusion] It is necessary to take appropriate formula to calculate the evapotranspiration. The FAO Penman 1979 was approximately equivalent to FAO Penman Monteith to calculate warm steppe＇s evapotranspiration in the source region of three rivers.