Peter Harley

General Information

ACD & TIIMES
Associate Scientist
BEACHON

Contact Information:
PO Box 3000, Boulder, CO 80307-3000
Office: FL0 - 3170
Telephone: 303-497-1863
Email: harley@ucar.edu
Home Page | BAI Group Page - Vita

Research Focus & Field Studies FY08:

Model of Emissions of Gases and Aerosols from Nature (MEGAN)

My TIIMES research focuses on quantifying trace gas emissions from plants and elucidating short-term and long-term environmental controls over those emissions.  These efforts involve both laboratory and field measurements, and are conducted within the framework of the Model of Emissions of Gases and Aerosols from Nature (MEGAN). Initially, these efforts were focused on the potential impacts of biogenic emissions on tropospheric oxidant chemistry, but now increasingly relate to the involvement of trace gas emissions on formation and growth of secondary organic aerosols.

MEGAN Community Data Portal

MEGAN Interactions Group

Work this fiscal year has included studies of low molecular weight oxygenated compounds (e.g., methanol, acetone, acetaldehyde) and attempts to better quantify emissions of high molecular weight terpenoids such as sesquiterpenes.  Both of these efforts have been facilitated by the development of a laboratory-based FLUXTRON platform for the measurement of emissions under controlled environmental conditions.

Future plans involve continuing these efforts under the umbrella of BEACHON.  In particular, the development of a convenient and well-equipped field site in the Manitou Experimental Forest as part of BEACHON-SRM08 will greatly aid this work in the future, facilitating long-term measurements and the characterization of seasonal and interannual variations in BVOC emissions.

Biological & physical controls over emission of potential SOA precursors from vegetation
NCAR PI(s):  Peter Harley, Jim Greenberg, Alex Guenther, Thomas Karl
Brief description of the project objectives and approach:

Through a combination of laboratory (including NCAR greenhouse and Fluxtron facilities) and field measurements, we will improve our estimation of the magnitude of emissions of BVOC from vegetation and our understanding of the controls over those emissions.  In the context of BEACHON, we will focus on those BVOC implicated in formation and growth of secondary organic aerosol (a list including, but not necessarily restricted to: isoprene, methylbutenol, monoterpenes and sesquiterpenes).  Abiotic controls include light and temperature, possibly CO2, and stresses such as drought and elevated O3.  Potential biological controls include plant phenology and stress due to herbivory.  Though emissions of these compounds are incorporated into the current version of MEGAN, realistic parameterizations will require substantially more emissions data from a wide variety of plant species and growth forms.  Elucidation of controls over emissions requires a combination of controlled experiments under laboratory conditions, and long-term field measurements obtained over complete (and ideally multiple) growing seasons.

Measurements will be accomplished using a variety of vegetation enclosure systems, from temperature controlled leaf cuvettes to branch enclosures to whole plant enclosures, and BVOC identification and quantitation will be accomplished using a variety of analytical techniques including GC-FID, GC-MS, and PTR-MS.  Leaf enclosure experiments will also incorporate simultaneous measurements of net photosynthesis, evapotranspiration, and stomatal conductance.

FY2008 accomplishments:

• Instrument development and preliminary measurements to determine the role of light and temperature in establishing the atmospheric compensation point for light weight oxygenated species such as methanol, acetaldehyde and acetone.  Ultimately, these measurements and algorithms will be incorporated into MEGAN.

• Measurement of secondary organic aerosol precursors (primarily mono- and sesquiterpenes) from dominant vegetation species in the rainforest of Borneo.  This work was carried out as part of OP3 (Oxidant and Particle Photochemical Processes above a South-East Asian tropical rain forest) sponsored by the Natural Environment Research Council in the UK and the University of Malaysia Sabah.

• As part of BEACHON-SRM08, I participated in the development of a long-term research site at the Manitou Experimental Forest north of Woodland Park, CO.  Measurements were initiated to elucidate short and long-term controls over emissions of biogenic VOC (methylbutenol, mono- and sesquiterpenes) from needles of Ponderosa pine, the dominant tree species at the site.

Relevance to BEACHON:

To the extent that SOA (and ice nuclei from biogenic sources) contribute to cloud formation and determination of cloud radiative properties and precipitation, better understanding of the sources of biogenic SOA precursors is essential.  Understanding of potential feedbacks on BVOC emissions due to alterations in cloud properties and precipitation will require far better understanding of the effects of light and, especially, effects of soil moisture, on these emissions.  Measurements of above-canopy BVOC fluxes are a significant component of BEACHON-SRM08, and concomitant measurements at the leaf or branch scale will both constrain above-canopy flux estimates and help explain observed variations in fluxes on diurnal and seasonal (interseasonal) time scales.

Community Service FY08:

• Mentoring two Colorado College undergraduates participating in the BEACHON-SRM08 Field Study (Woodland Park, CO, July - September 2008)

Scientific Talks FY08:

• The BEACHON Project - Southern Rocky Mountain Intensive (Woodland Park, CO, August 2008)
• Obtaining estimates of Farquhar model parameters from measured photosynthesis data (University of Colorado Mountain Research Station, CO, July 2008

Publications FY08:

Jardine, K., P. Harley, T. Karl, A. B. Guenther, M. Lerdau, J. E. Mak, 2008: Plant physiological and environmental controls over the exchange of acetaldehyde between forest canopies and the atmosphere. Biogeosciences. (Submitted)