Evaluating Spatial Scales of Eddy Covariance Fluxes over the Southeastern United States using 20 Hz Wind and Temperature Data from the NASA DC-8 Meteorological Measurement System
Wednesday, 17 December 2014
Accurate calculation of eddy covariance fluxes of chemical constituents requires precise determination of turbulent scales of motion. During the 2013 SEAC4RS (Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys) mission, fast-response, in-situ measurements of temperature (T), three-dimensional wind (u,v,w), and Formaldehyde (CH2O) were collected on board the NASA DC-8. In the boundary layer above dense oak forests of the southeastern United States, strong updrafts detected by the Meteorological Measurement System (MMS) correlated with peak concentrations of CH2O in regions of active vertical mixing. However, flux calculations of chemical constituents critically depend on dynamic mixing scales, which can depend on altitude and be driven by diurnal variability. Within regions of enhanced Isoprene and/or CH2O concentrations, sensible heat and momentum flux calculations based on 20 Hz MMS winds and temperatures will be used to define eddy scales responsible for upward transport of trace gases. Defining spatial scales of active turbulence at different levels within the mixed layer will assist those computing eddy fluxes of a broad spectrum of reactive trace gases, including Isoprene and its oxidation products.