will also use newer technologies that were not available at the time of Prairie Grass. Our current tracer technology can measure both the
mean concentration and concentration fluctuations. For characterizing the state of the boundary layer we plan on using three-dimensional sonic anemometers,
sodars, a 915 MHz radar profiler, and an existing meteorological network containing 34 towers. A 61 m tall tower in the study area will
provide the means of making detailed observations of the vertical turbulence and temperature profiles. Additional sensors may be provided by collaborators.
As noted in the introduction, the Sound-Barrier Tracer Study showed deviations from the Prairie Grass results in both stable and unstable
conditions. This leads to some basic questions regarding the repeatability of dispersion results from short-term
studies such as Prairie Grass, which took place over a single intensive observation period in July and August 1956. Are the observed deviations due to
different surface roughnesses at the two sites, different methods of measuring boundary-layer stability, random variability, seasonal differences, or
perhaps something else? Will further tracer releases continue to show deviations from the Prairie Grass results? As a result of the issues identified above,
the science objectives of Project Sagebrush are to:
Improve the understanding of short-range dispersion from continuous near-surface releases in nearly flat terrain using modern meteorological
sensors and tracer technology.
Improve the understanding of concentration fluctuations within continuous plumes.
Assess the overall repeatability and applicability of individual tracer studies by comparing the new tracer results to classical tracer
Develop improved parameterizations linking plume widths to observed boundary-layer structure.
Develop improved dispersion models for both mean concentrations and concentration fluctuations.
Provide a new high-quality data set for testing and validating existing dispersion models.
Phase 1 of Project Sagebrush started the first week of October in spite of the government shutdown. The Piper Navajo aircraft from the
University of Tennessee Space Institute (UTSI) had arrived the previous week and was fitted out with a Trace Gas Analyzer (TGA) for sampling
the SF6 tracer used in the project. A shakedown flight of the aircraft was completed on 1 October. The weather during the first two weeks of
October was unfortunately rather unsettled and not ideal for the planned tracer studies. Regardless, three of the planned five Sagebrush tracer
releases were completed on 2, 5, and 7 October with the UTSI aircraft participating in all three.
After the release on the 7th, the weather turned more unsettled and looked to remain so through much of the original two-week window for Phase 1.
The UTSI staff therefore decided to return to Tennessee on the 9th. FRD extended Phase 1 for one week to conduct additional releases without the
aircraft. This entailed reducing the tracer release rate and moving some of the tracer samplers closer to the source. Two final releases were
conducted on 11 and 18 October. Overall, the one-week extension of the study allowed FRD to meet its original objective of completing five
successful tracer releases.
Quality control and assurance analyses of the bag sampler tracer data set and fast-response tracer data have been completed for all 5 tests
and a comprehensive data report on Phase 1 is in preparation.
Data is available upon request.
Clawson, Kirk L. , D. D. Finn and R. Eckman, 2015:Dispersion
Characteristics of Project Sagebrush Phase 1. 95th Annual American Meteorological Conference. Air Pollution
Meteorology Observational Studies. 4-8 January Phoenix, AZ Amer. Meteor. Soc., 1.1
Eckman, R. , K.L. Clawson, and D. D. Finn, 2015:Changes in
Horizontal Plume Distributions at Larger Turbulence Intensities. 95th Annual American Meteorological Conference.
Source Models and Atmospheric Dispersion Studies. 4-8 January Phoenix, AZ Amer. Meteor. Soc., 3.6
Finn, D., K.L. Clawson, R.M. Eckman, R.G. Carter, J.D. Rich, T.W. Strong, S.A. Beard, B.R. Reese, D. Davis, H. Liu, E. Russell, Z. Gao,
S. Brooks, 2015: Project Sagebrush Phase 1, NOAA Technical Memorandum OAR ARL-268 , Air Resources Laboratory, Idaho Falls, Idaho, pp 338.
Richard Eckman, Ph.D
1750 Foote Dr.
Idaho Falls, ID 83402