DiGiovanni et al. 2013
DiGiovanni, K., F. Montalto,, and , 2013: The applicability of classical predictive equations for the estimation of evapotranspiration from urban green spaces: Green roof results. J. Hydrol. Eng., 18, 99-107, doi:10.1061/(ASCE)HE.1943-5584.0000572.
Green roofs and other urban green spaces can provide a variety of valuable benefits linked to evaporative processes, including stormwater management, reduction of urban heat island, and carbon sequestration. Accurate and representative estimation of urban evapotranspiration (ET) is a necessary tool for predicting such benefits. However, many common ET estimation procedures were developed for agricultural applications, and thus carry inherent assumptions that may not be applicable to urban green spaces, including green roofs. The objective of this paper is to evaluate the performance of two combination methods for the prediction of ET from a green roof. Two Penman-Monteith based ET estimation methodologies, using onsite and regionally available data sets, were compared, for daily time steps, to weighing lysimeter measurements of actual ET at a green roof site in the Bronx, NY. Over the period of record, the ASCE Standardized Reference ET Equation performed well in predicting actual ET with a RMSD of only 0.03 mm/d. Additionally, the ASCE Standardized Reference Evapotranspiration Equation for short reference types, using onsite climatic data, and coupled with a variation of the Thornthwaite-Mather approximation, which accounts for variable media moisture conditions, gave reasonable predictions of actual evapotranspiration for 89 days analyzed (representing months from June through January) with an aggregate underestimation of 10.1%. However, this method was found to be highly sensitive to input parameters, specifically media field capacity. Further onsite data collection is necessary to fully evaluate the performance of the equations over different seasons at this location, while monitoring of supplementary urban green spaces and green infrastructure sites will also lend further insights regarding urban evapotranspiration.