JEHN-YIH JUANG2018-09-102018-09-102016-03http://scholars.lib.ntu.edu.tw/handle/123456789/396577https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960156670&doi=10.1002%2f2015JG003221&partnerID=40&md5=ba3bd99deb57067da6c6e777cfa89fa6Microphysical processes of fog and their spatial and temporal pattern are a challenge to study under natural conditions. This work focuses on the development of bidirectional fluxes of fog droplets above a forest canopy in northeastern Taiwan. Bidirectional fluxes occurred regularly, start from the smallest droplet class (<2.66 μm diameter), and subsequently extend to larger droplets up to 7.41 μm diameter. The development of the bidirectional fluxes with positive (upward) fluxes of smaller droplets and downward fluxes of larger fluxes is associated with a temperature gradient and with the activation of fog droplets according to the Köhler theory. Small fog droplets develop close to the canopy as result of evapotranspiration and subsequent condensation. The rapid growth of small fog droplets and the accelerated growth of activated droplets, a process which is more likely to occur at higher levels of the fog layer, lead to a sink of small droplets and a source of larger droplets within the fog. This is in accordance with the observation that positive droplet number fluxes of small fog droplets outnumber the negative fluxes from the larger fog droplets. For liquid water, the net flux is negative. © 2016. American Geophysical Union. All Rights Reserved.droplet flux; eddy covariance; fog dynamics; fog microphysics; Taiwanatmosphere-biosphere interaction; droplet; eddy covariance; evapotranspiration; fog; forest canopy; moisture flux; temperature gradient; Taiwanjournal article10.1002/2015jg0032212-s2.0-84960156670