The effects of turbulence and environmental parameters on isoprene mixing ratios within and above the canopy during PROPHET 2001.

Abstract

During July of 2001, vertical profiles of isoprene mixing ratios and meteorological parameters were measured, both within and above canopy, in a hardwood forest at UMBS near Pellston, Michigan. Vertical profiles of isoprene mixing ratios are compared with vertical profiles of temperature, wind speed, turbulence, relative humidity, and PAR to see how these environmental parameters may influence isoprene mxing ratios. The results indicate that an anti-correlation could exist between isoprene mixing ratios and the level of turbulence present in the atmosphere. High levels of turbulence sometimes yielded lower isoprene mixing ratios even with high light values and warm temperatures. Linear regression was performed on the 14 days of data along with the light (CL) and temperature (CT) emission algorithms of the BEIS model. As has been established in other studies, positive correlations were observed between temperature and isoprene mixing ratios, and PAR and isoprene mixing ratios. When CL and CT were multiplied together and divided by wind speed, the correlation increased. Thus, it appears that isoprene mixing ratios in the canopy are driven by isoprene emissions, and dilution by the wind and turbulence acts to control isoprene mixing ratios.