Investigating Interannual and Seasonal Variations of Energy Balance in a Mountain Cloud Forest in Chi-Lan Mountain

Cloud forest is usually covered by dense fog influencing measurement of flux severely. Energy balance closure (EBC) is a parameter to correct measurement of flux but it will change by environment. This study find out the relationship between environmental factors and energy balance closure in Chi-Lan Mountain cloud forest. The Chi-Lan Mountain cloud forest in northeastern Taiwan is a typical subtropical cloud forest. At this site, the average EBC is 0.86, similar as other needle forest site. EBC is strongly influenced by dense fog. While the visibility is under 100 m, the EBC is only 0.48. EBC increase when visibility increase. Wind speed is also an environment factor effecting EBC. EBC will increase when wind speed increase to 2.0 m s-1, but decrease when wind speed over 2.0 m s-1. The EBC is more than 1 in morning due to the different characteristics of air masses causing by winds. In short, the inter-annual and seasonal variations in energy balance closure over Chi-Lan Mountain forest is dominate by dense fog.