Measurements of upward turbulent ozone fluxes above a subalpine spruce‐fir forest

High rural concentrations of ozone (O 3 ) are thought to be either stratospheric in origin, advected from upwind urban sources, or photochemically generated locally as a result of natural trace gas emissions. Ozone is known to be transported vertically downward from the above-canopy atmospheric surface layer and destroyed within stomata or on other biological and mineral surfaces. However, here we report winter-time eddy correlation measurements of vertical O 3 flux above a subalpine canopy of Picea engelmannii and Abies lasiocarpa in the Snowy Range Mountains of Wyoming that indicate anomalous upward O 3 fluxes. Upward fluxes of 0.5 μg m -2 s -1 (11 kg km -2 day -1 ) were routinely measured during the 1991-92 winter season. Decreasing O 3 concentration from several hours to several days that relate to increasing positive O 3 flux magnitudes and visa versa, suggest O 3 may be temporarily stored in the snow base.