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.