Characterization and parameterization of kB-1 variation in different growth stages of summer maize

Abstract

【Objective】 Previous studies indicate that existing parameterizations for additional damping (kB-1) are not applicable to all vegetation types. This paper proposes a new approach to account for significant structural differences during vegetation growth. The objective is to analyze the daily and monthly variation patterns of kB-1 during four growing stages of summer maize and to identify the optimal parameterization for each stage. 【Method】 We used fluxes, meteorological and MODIS satellite data from June to September 2012 at the US-Tw2 site to infer the damping parameter kB-1 using the Monin-Obukhov similarity theory, across the seedling, jointing, heading, and maturity stages with observed data. 【Result】 Across all four growing stages, kB-1 exhibited a daily pattern with minimal values in the morning and evening and a peak during midday. Monthly mean values increased with surface roughness. Among the nine parameterization schemes, the results of K07 best matched the observed kB-1 values during the seedling stage, while K89 was most effective for the jointing, heading, and maturity stages, with their associated root mean square error (RMSE) being 1.34, 2.41, 2.79, and 1.55, respectively. For the sensible heat flux, K07, S58, S01 and K89 best matched the observed data in the seedling, jointing, heading, and maturity stages, respectively, with their associated RMSEs being 33.39 W/m2, 46.98 W/m2, 65.97 W/m2, and 36.46 W/m2, respectively. 【Conclusion】 In early growth stage, the parameterization schemes based on the roughness Reynolds number matched the observed data better, whereas the schemes incorporating vegetation structure and air-surface temperature difference (Ts-Ta) were more accurate in the later stages. The optimal parameterization schemes for estimating sensible heat fluxes in the seedling, jointing, heading, and maturity stages are K07, S58, S01 and K89, respectively.

Keywords

• kb-1
• parameterization scheme
• sensible heat flux
• reproductive period
• maize