Methods of Accumulated Temperature During Rice Growing Stage in Heilongjiang Province

The accumulated temperature is an important index for regional thermal resource to be valued and development process of crops to be evaluated. Taking rice for example, based on the research of temperature coefficient and change of diurnal temperature, a new method of accumulated temperature is explored and studied with biological significance, so heat excessive and fewness could be shown accurately during growing stage of rice. The result shows that using daily extreme temperature, sub-sine simulation method and correct formula can simulate the diurnal variation of temperature for meteorological stations, such as Fuyu, Fujin, Muling and Harbin; temperature coefficients of rice are sectionally simulated above 30℃ and under 20℃ with Curve Equation Method. Results are extended for rice temperature coefficient. Temperature coefficients between three fundamental points of temperature are simulated. It could be as virtual quantification to three fundamental points of temperature. Hourly and daily equivalent temperature are got by combining temperature coefficient with simulated and corrected temperature of 24 h, and accumulated equivalent temperature is achieved during growing stage for rice. The method is preferable to the early method which values the accumulated temperature with daily mean temperature because it could not overlook positive role of temperature of part hours on rice at a low temperature condition, and it could not exaggerate positive role of temperature of part hours on rice at a high temperature condition. The method shows that different rice growing stages is various reaction of changing temperature. Furthermore, continuous quantification of heat resources is achieved during growing of rice. Accuracy is increased for equivalent accumulated temperature during the growing of rice. Taking Harbin city for example, the stage is main period of vigorous growth because daily equivalent temperature is close to daily mean temperature, and even is above daily mean temperature in June and July. In the last 55 years, the accumulated temperature increase significantly by 92℃·d/(10 a); they are sharp periods of that in the 1970s and the 1990s, with the climate change trend rate 359℃·d/(10 a) and 559℃·d/(10 a). From the 2000s to now, heat resource is full. Three fundamental points and diurnal changes of the temperature are taken in studying methods of accumulated equivalent temperature, so accuracy is increased for computation of accumulated equivalent temperature, and could show heat difference in the time and space.