A method for estimating surface albedo and its components for partial plastic mulched croplands

Abstract

In partial plastic mulch-covered croplands, the complicated co-existence of bare soil surface, mulched soil surface, and dynamically changing canopy surface results in challenges in accurately estimating field surface albedo (α) and its components (bare soil surface albedo, αb; mulched soil surface albedo, αm; and canopy surface albedo, αc) during the whole growth period. To accurately estimate α, αb, αm, and αc, and to quantify the three surfaces’ contributions to field shortwave radiation reflections (Fb, Fm, Fc), (1) a modified two-stream (MTS) approximation solution that considered the effect of plastic mulch has been proposed to accurately estimate α; (2) dynamic variations of αb, αm, and αc, and Fb, Fm, Fc have been characterized. Therein, αb and αm were determined from corresponding parameterization schemes, αc is determined using mulched irrigated croplands surface albedo (MICA) relationship between α and αb, αm, and αc that established in this study. Results indicated that: (1) compared with measurements, considering the effect of plastic mulch will significantly improve estimation of α when ground surface is not fully covered by crop canopy, while not will underestimate α by a mean value of 0.061 in the early growth period; (2) mean values of α, αb, αm, and αc during the whole growth period were 0.198, 0.174, 0.308, and 0.160, respectively, while the corresponding Fb, Fm, and Fc were 0.08, 0.42, and 0.50, respectively.