Methods of calculating growing degree-day based on OR assumption and daily extreme temperatures | 基于优化生长假设利用极端温度计算日积温的方法

chinois. 积温是评估区域热量资源和测算作物生长发育进程的重要指标，准确计算日积温是作物模型中有效模拟和预测作物生长发育进程和科学调控田间水肥管理的基础。本研究以作物生长发育对温度反应的优化假设为前提，对比分析基于日极端温度通过日均温估算日积温的2种方法、温度日变化正弦模拟得到小时温度并以时积温改进日积温模型的方法，与温度日变化曲线和三基点温度围成的真实有效的日积温的差异。首先从理论上论述了日均温法可能导致真正的日积温被高估或低估和日极值法可能高估日积温，然后以实例分析和论证了3种日积温模型与真实有效的日积温间的差异，得出时积温方法计算日积温误差相对最小的结论。为准确估算日积温，建议基于优化假设和日极端温度计算日积温时采用时积温方法。

anglais. Growing degree-day （GDD） is an important indicator for assessing regional heat resources and timing phenol- stage process, and correct GDD calculation is the basis of water and fertilizer management in agricultural production and accurate simulation and prediction of crop growth and development in crop models. In this paper, two daily average temperature methods of calculating GDD based on assumption of optimized response of growth and development to temperature （OR assumption） and daily extreme temperatures was reviewed, and a growing degree-hour （GDH） method of calculating growing degree-days was introduced. Hourly temperature was estimated by diurnal temperature curve simulated by sine wave based on extreme temperatures. Theoretical argument showed that daily average temperature method may result in an over- or under-estimated GDD,and daily extreme temperatures method may result in an over-estimated GDD;Case study showed the GDH method had the smallest error comparing with the true GDD in three methods. To calculate accurately GDD, GDH method is recommended strongly when GDD is calculated by extreme temperatures based on OR assumption.