Parameterization of canopy resistance for modeling the energy partitioning of a paddy rice field

Models for predicting hourly canopy resistance (r (c)) and latent heat flux (LET) based on the Penman-Monteith (PM) and bulk transfer methods are presented. The micrometeorological data and LET were observed during paddy rice-growing seasons in 2010 in Japan. One approach to model r (c) was using an aerodynamic resistance (r (a)) and climatic resistance (r (*)), while another one was based on a relationship with solar radiation (SR). Nonlinear relationships between r (c) and r (*), and between r (c) and SR were found for different growing stages of the rice crop. The constructed r (c) models were integrated to the PM and bulk transfer methods and compared with measured LET using a Bowen ratio-energy balance method. The root mean square errors (RMSEs) were 155.2 and 170.5 W m(-2) for the bulk transfer method with r (c) estimated using r (*) and with a function of SR, respectively, while the RMSEs were 87.4 and 85.7 W m(-2) for the PM method with r (c) estimated using r (*) and SR, respectively. The r (c) integrated PM equation provided better performance than the bulk transfer equation. The results also revealed that neglecting the effect of r (a) on r (c) did not yield a significant difference in predicting LET.