Wet Canopy Evaporation Rate of Three Stands in Western Sichuan, China
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Graphical Abstract
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Abstract
The wet canopy evaporation rate (Er) was calculated by Penman-Monteith combination model based on three assumptions and with meteorological variables 2 m above the canopy in three stands, dominated by spruce (SF), fir (FF) and birch (BF) trees, respectively, in the subalpine forests in western Sichuan, China over a growing season. The total amount of the E was 44.5 mm for SF, 88.5 mm for FF and 57.8 mm for BF, accounting for 9.2%, 16.6% and 10.2% of the gross rainfall, respectively, in the measuring period. There was the highest average monthly Er and percentage of E to gross rainfall for FF compared with SF and BF. Mean Er was 0.097 mm h−1 (ranging from 0.028 to 0.487 mm h−1), 0.242 mm h−1 (from 0.068 to 0.711 mm h−1) and 0.149 mm h−1 (from 0.060 to 0.576 mm h−1) for SF, FF and BF, respectively. The highest average monthly Er occurred in June was 0.120 mm h−1 for SF, 0.317 mm h−1 for FF and 0.169 mm h−1 for BF, and the lowest value in October was 0.083 mm h−1 for SF, 0.187 mm h−1 for FF and 0.101 mm h−1 for BF, respectively. The averages of Er from 8:00 to 16:00 were significantly higher than those from 0:00 to 8:00 and from 16:00 to 0:00 for the three stands. The marked daily and monthly differences of Er were contributable to the variations of solar radiation, air temperature and relative humidity above the canopy.
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