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Steve Oncley

General Information

Steven Oncley

EOL - TIIMES
Project Scientist II
BEACHON & BGS

Contact Information:
PO Box 3000, Boulder, CO 80307-3000
Office: FL1-2069
Telephone: 303-497-8757
Email: oncley@ucar.edu
Home Page | Integrated Surface Flux System - Vita

Research Focus FY08:

TRAM results - Steve Oncley

Time-distance cross-sections of temperature T (a,d), carbon dioxide concentrations CO2 (b,e), and specific humidity q (c,f) measured by TRAM. Distances are the position north of Como Creek. Three pulses of air that are CO2-rich, cool, and moist are seen during this 1hr period close to the ground (panels a--c). They are much less obvious at a height halfway up the canopy (panels d--f). This provides evidence of horizontal transport of CO2 within a canopy roughly following the path of water drainage; however, the transport is organized in relatively small-scale blobs.
High resolution figure

Horizontal Advection of Carbon Dioxide

My TIIMES research has been focused on understanding horizontal advection of carbon dioxide in forest canopies, which is thought to be a significant process controlling the Net Ecosystem Exchange (NEE) of carbon. This research has been a collaboration with Jielun Sun (MMM - TIIMES), Russ Monson (University of Colorado, Biology), and others. Because there exist very few data sets that investigate this problem, we are carrying out a series of experiments at the University of Colorado's Ameriflux site on Niwot Ridge, CO, in collaboration with Prof. Russ Monson.

 

Nivot07

2006-2007 (Niwot07): EOL deployed, for the first time, the TRAnsect Measurement (TRAM) system (also developed with TIIMES support) along a 110m-long path crossing Como Creek both in the trunk space and in the middle of the canopy space. Hydra and ASA were deployed along this transect and were used to anchor the TRAM measurements. These observations have shown that in-canopy advection of CO2 occurs quite close to the surface by organized blobs on the order of 20m wide and a few hundred meters long. Their track roughly follows Como Creek, though the highest CO2 concentrations can be 10s of meters away laterally. This research also is supported by a grant from NSF-Biocomplexity (with CU).

 

TRAM

2008-2009 The TRAnsect Measurement (TRAM) track was redeployed in 2008, along with ASA networks measuring photosynthetically-active radiation (PAR), and soil temperature and moisture, to an area between the long-term CU and USGS towers. Differences in CO2 concentration measured at these towers have been observed that may be associated with a change in canopy density. The TRAM data system also was upgraded to accomodate the acquisition of more data channels (including PAR). These observations will continue through 2009.

 

AHATS - Steve Oncley

AHATS
High resolution figure

CHATS

As part of the CHATS experiment, TIIMES-BEACHON supported the development of a fast-response barometer, capable of measuring turbulent fluctuations of pressure, p'. There have been few measurements of p' in the atmosphere and fewer still in the roughness sublayer (where form drag is important) due to the difficulty of finding a pressure port that doesn't add dynamic pressure errors. For CHATS, we borrowed quad-disk probes (QDPs) patented and manufactured by NOAA-ETL and tested two commercial designs in the EOL wind tunnel. A simple modification to less expensive commercial QDPs appeared to perform nearly as well as the NOAA probes. We also operated two different transducer systems to determine the quality of the measurements. Data analysis is just beginning, though indications are that both systems operated as expected. This research is in collaboration with William Massman (US Forest Service, Rocky Mountain Research Station).

Experience with these sensors guided the design for a deployment of 14 such pressure sensors (along with 37 3-axis sonic anemometers) for the Advective Horizontal Array of Turbulence Study (AHATS) in Summer 2008. This study, led by Chenning Tong (Clemson University, SC), will investigate how pressure fluctuations interact with the production, redistribution, and destruction of the kinetic energy of turbulence at various spatial scales.

 

Scientific Talks FY08:

  • Wireless sensor networks at EOL (CUAHSI, Boulder, CO, July 2008)

Publications FY08:

Burns, S. P., A. Delany, J. Sun, B. B. Stephens, S. P. Oncley, G. D. Maclean, S. R. Semmer, J. Schroter, J. Ruppert, 2008: An evaluation of calibration techniques for in-situ carbon dioxide measurements using a programmable portable trace-gas measuring system. J. Atmos. Ocean. Technol., doi: 10.1175/2008JTECHA1080.1. (In Press)

Oncley, S. P., K. Schwenz, S. P. Burns, J. Sun, R. K. Monson, 2008: A cable-borne tram for atmospheric measurements along transects. J. Atmos. Ocean. Technol., doi: 10.1175/2008JTECHA1158.1. (In Press)

Patton, E. G., T. Horst, D. H. Lenschow, P. P. Sullivan, S. P. Oncley, S. P. Burns, A. B. Guenther, T. Karl, S. D. Mayor, S. M. Spuler, J. Sun, A. A. Turnipseed, E. Allwine, S. Edburg, B. Lamb, R. Avissar, H. Holder, R. Calhoun, J. Kleissl, W. Massman, K. Tha Paw U, J. Weil, L. Rizzo, A. Held, 2008: The Canopy Horizontal Array Turbulence Study (CHATS). , Stockholm, SE, AMS, American Meteorological Society, 18A.1.

Oncley, S. P., W. Massman, E. G. Patton, 2008: Turbulent pressure fluctuations measured during CHATS. 18th Symp. On Boundary Layers and Turbulence, Stockholm, SE, AMS, American Meteorological Society, 18A.3.

Zhong, S., W. Yao, T. Horst, C. Whiteman, S. P. Oncley, 2008: Basin temperature inversions and their relationship to ambient atmospheric conditions. , Stockholm, SE, AMS, American Meteorological Society, 14A.2.

Oncley, S. P., K. Schwenz, J. Sun, R. Monson, 2008: Measuring in-canopy advection of carbon dioxide using a new transect measurement system (TRAM). , Orlando, FL, US, J2.3.