A METHOD FOR CALCULATING THEDATE OF BOUNDARY TEMPERATURE USING SPLINE INTERPOLATION
求算界限温度日期的一种新方法──样条函数插值法

Using the data of monthly mean temperature of a year, the annual temperature curve was simulated by means of the spline interpolation. On the basis of the simulated curve, the beginning/last date of different boundary temperature and the cumulative temperature can be calculated. Spline-function is the smooth connection of continuous segments of a polynomial. The quadratic spline-function can be expressed as following: Based on the interpolation condition, connecting condition and boundary condition, the undetermind coefficient a, b,c can be calculated. The recurrence formulas are: On this basis, the annual temperature curve can be simulated, then the date of boundary temperature can be calculated.