Night-time evaporation from a short-rotation willow stand

• Published in: Journal of hydrology (Amsterdam) Vol. 157; no. 1; pp. 235 - 245
• Main Authors: Iritz, Zinaida, Lindroth, Anders
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 1994; Elsevier Science
• Subjects: canopy; climatic factors; dark; Earth, ocean, space; evaporation; Exact sciences and technology; External geophysics; leaf conductance; Meteorology; Other topics in atmospheric geophysics; Salix viminalis; stand characteristics; vapor pressure; Sweden; Europe; Climatic condition; Forests; Night; Ground surface; Dicotyledones; Atmospheric boundary layer; Angiospermae; Salix viminalis; Spermatophyta; Evaporation; Salicaceae
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/0022-1694(94)90107-4

The aim of the present study was to quantify and analyse the evaporation during night-time in a willow ( Salix viminalis L.) short-rotation stand. Evaporation measurements were made throughout the 24 h period on 76 days during the 1988 growing season using the energy-balance/Bowen-ratio method. Canopy conductance was estimated using a rearranged form of the Penman combination equation. The mean hourly evaporation rate during daytime was 0.18 mm h −1 and the corresponding value during night-time was 0.013 mm h −1, about 7% of the daytime rate. The mean cumulative night-time evaporation was 0.12 mm per night or 4.3% of the mean daytime evaporation. The highest night-time evaporation occurred in September and October with 0.21 mm and 0.36 mm per night, respectively, some 30–35% of the daytime evaporation during these periods. Total night-time evaporation for the growing season was estimated as 21 mm. Night-time evaporation was controlled mainly by vapour pressure deficit and ventilation whereas net radiation had only a minor influence. The night-time canopy resistance was estimated for a shorter period when the canopy was completely closed (leaf area index around 5) and the soil evaporation could be assumed negligible. The canopy resistance ranged between 10 and 220 s m −1 depending on vapour pressure deficit. The dependence on vapour pressure deficit during night-time was similar to the dependence during daytime but with a much larger sensitivity during the dark period.