Measurements of nighttime water vapor flux using a closed chamber technique
2007
Nakano, T.(Tokyo Metropolitan Univ., Hachioji (Japan)) | Nemoto, M. | Shinoda, M.
Nighttime water vapor transportation from the atmosphere to the ground surface, which involves dew formation and water vapor adsorption to the soil, is very small, yet its contribution to the water budget has been recognized as important, especially in arid and semiarid regions. We applied a closed-chamber (CC) technique to measure nighttime water vapor flux between the atmosphere and a grassland ecosystem and used a microlysimeter (ML) method to validate the results of the CC measurements. The CC measurements were conducted on nine nights in May, July, and September of 2005 and June of 2006 at Mongolian semiarid grassland. The results of our study indicate that water vapor was transported upward during five nights and downward during four nights, and the magnitude of nighttime water vapor fluxes ranged between -0.011 mm/h and 0.011 mm/h (a positive value represents upward transportation). We also found that downward vapor transportations were involved in both dew formation and direct water vapor adsorption. The results of the CC and ML methods showed good agreement, suggesting that the CC method is appropriate for measuring small water vapor fluxes.
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