Isoprene flux measurements using eddy covariance and disjunct eddy accumulation

Quantifying biogenic hydrocarbon (BHC) emissions is important for understanding the role they play in tropospheric chemistry. Isoprene is a very reactive compound that affects the oxidative capacity of the atmosphere, which in turn determines the lifetime of numerous atmospheric constituents such as methane (CH4) and CO. The oxidation of isoprene leads to the production of peroxy radicals (RO2), which may lead to the formation of organic acids, or depending on the level of nitric oxides present, to either production or consumption of tropospheric O3. BHC emissions, in particular isoprene, are predominantly driven by increases in temperature and solar radiation, and there can be significant variations in emissions from one hour to the next, and between days. To better understand the natural variability of isoprene emissions, eddy covariance isoprene flux measurements are being collected on a long-term basis. This long-term dataset, spanning from 1999-2005, provides a unique tool for validating biogenic emission inventories that are used as input into regional photochemical models. This long-term dataset will be presented and compared to the biogenic emission inventory system (BEIS3) model estimates. Using isoprene as a compound of interest, the micrometeorological technique of disjunct eddy accumulation (DEA) was tested side-by-side with the direct eddy covariance (EC) technique. One week of DEA and EC hourly flux measurements will be presented, confirming the use of DEA to measure fluxes of other atmospheric compounds that, to date, has not been attainable.