http://www.cnr.it/ontology/cnr/individuo/prodotto/ID13157

Determining degree-days thresholds from field observations (Articolo in rivista)

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Determining degree-days thresholds from field observations (Articolo in rivista) (literal)

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Alternative label

Snyder R.L, Spano D., Cesaraccio C., Duce P (1999)
Determining degree-days thresholds from field observations
in International journal of biometeorology (Print); Springer Verlag, New York NY (Stati Uniti d'America)
(literal)

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Snyder RL: Department of Land, Air and Water Resources,University of California, Davis Spano D: Università di Sassari, Dipartimento di Economia e Sistemi Arborei Cesaraccio C,Duce P: CNR-IBIMET, Sassari (literal)

Titolo

Abstract

This paper compares several methods for determining degree-day (°D) threshold temperatures from field observations. Three of the methods use the mean developmental period temperature and simple equations to estimate: (1) the smallest standard deviation in °D, (2) the least standard deviation in days, and (3) a linear regression intercept. Two additional methods use iterations of cumulative °D and threshold temperatures to determine the smallest root mean square error (RMSE). One of the iteration methods uses a linear model and the other uses a single triangle °D calculation method. The method giving the best results was verified by comparing observed and predicted phenological periods using 7 years of kiwifruit data and 10 years of cherry tree data. In general, the iteration method using the single triangle method to calculate °D provided threshold temperatures with the smallest RMSE values. However, the iteration method using a linear °D model also worked well. Simply using a threshold of zero gave predictions that were nearly as good as those obtained using the other two methods. The smallest standard deviation in °D performed the worst. The least standard deviation in days and the regression methods did well sometimes; however, the threshold temperatures were sometimes negative, which does not support the idea that development rates are related to heat units. (literal)

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