Relationships between rainfall, fog, and throughfall at a hill evergreen forest site in northern Thailand

• Published in: Tropical Montane Cloud Forests pp. 324 - 331
• Main Authors: Tanaka, N., Kuraji, K., Tantasirin, C., Takizawa, H., Tangtham, N., Suzuki, M.
• Format: Book Chapter
• Language: English
• Published: Cambridge University Press 06.01.2011
• ISBN: 9780521760355; 0521760356
• DOI: 10.1017/CBO9780511778384.036

ABSTRACTThis study used hourly data of rainfall, water captured by a sheltered fog gage, and wind speed as collected at a montane forest site in northern Thailand during nearly 3 years, to test the efficiency of the rain-protected passive fog gage as a predictor of fog occurrence. To separate possible contributions by wind-driven rain (WDR) from fog, the maximum rate of water input to the fog gage during rainless conditions (Fogmax) was derived as a function of wind speed. During periods with rain and fog, the fog gage often produced values above the Fogmax line, suggesting contributions by WDR. The specific conditions of rainfall intensity and wind speed for which this happened were identified and the corresponding data were excluded from the fog data-set for subsequent reanalysis. Based on the recalculated data-set, inter-annual and seasonal variations as well as the diurnal pattern of fog occurrence at the studied forest are described. Fog-induced canopy drip during rainless periods was only 19.3 mm over the 3 years, being less than 0.5% of total throughfall and c. 33% of the corresponding catch by the fog gage (58 mm). However, the fog gage captured nearly 18 times more water (1033 mm) during all times when WDR could reasonably be excluded.