Study on the Estimation of Greenhouse Sensible Heat Flux Based on the Surface Renewal Method: Validation and Calculation Results

To address the issues of poor universality, high cost, and difficulty in parameter acquisition associated with existing methods for estimating crop evapotranspiration (ETc) in greenhouses, this study focused on tomato plants in a Venlo-type greenhouse (Zhenjiang, Jiangsu Province, from 20 November 2024 to 9 January 2025) to explore the applicability of the surface renewal (SR) method in greenhouses. Micrometeorological data were collected by deploying high-frequency temperature sensors and other equipment. The accuracy of sensible heat flux (H) estimation by the traditional Snyder method and the Chen method was compared. Based on the latent heat flux (LE) measured by the evaporimeter method, the actual sensible heat flux was derived through an energy balance model, which was then used for comparative verification with the estimation results of the two methods. The results showed that the Chen method, which incorporates friction velocity (u*) and does not rely on the empirical calibration coefficient α, is adaptable to the characteristics of non-uniform airflow in greenhouses. Under sunny conditions (R2 = 0.722 during the day and R2 = 0.712 at night) and cloudy conditions (R2 = 0.7558 during the day and R2 = 0.754 at night), the estimation accuracy of the Chen method was significantly higher than that of the Snyder method. Moreover, for the entire experimental period, the R2 value reached 0.733, the Pearson’s r coefficient was 0.856, and the outlier rate was as low as 9.1%. This study innovatively applies the SR method to semi-closed heated greenhouses, making a clear distinction from previous SR studies conducted in open-field environments and providing a new approach for the accurate estimation of greenhouse heat flux.