2011 AMS Summer Community Meeting
National Center for Atmospheric Research
Center Green Conference Center · Boulder, Colorado
8–11 August 2011
Measurement of Greenhouse and Trace Atmospheric Gases
using Miniaturized AirCore® Technology
Kristin Herrmann Favela, Tom Jaeckle, LeMoey Wiebush
Southwest Research Institute, San Antonio, Texas
Pieter Tans
NOAA’s Earth System Research Laboratory, Boulder, Colorado
The National Oceanic and Atmospheric Administration (NOAA) is responsible for acquiring and maintaining the
global, regional, and local records of greenhouse gases. Specifically, the Global Monitoring Division (GMD)
Carbon Cycle Greenhouse Gases Group (CCGG) is charged with this mission. One significant tool developed by
scientists at NOAA's Earth Systems Research Laboratory (ESRL) is called AirCore®. This technology provides a
continuous sample of atmospheric gases when carried aloft with either a balloon or an aircraft, and is capable
of both vertical and land‐based (horizontal) measurements. Since AirCore® can obtain samples in the
troposphere and stratosphere, the balloon is the preferred lifting mechanism. However, the present
embodiment of the AirCore® sampler is large and heavy and, when carried aloft with a balloon, is subject to
launch restrictions and safety concerns.
The SwRI-developed Skywisp® stratospheric glider can operate at altitudes above 100,000 ft using a balloon for
ascent with the gross weight under 4 lbs. Reducing the AirCore® sampler to a size which can be hosted by the
glider will make launch and recovery easier, less expensive, and safer. Urban and other occupied regions of the
earth could be evaluated with the resulting system. Greenhouse gases (GHGs) and other pollutants could be
traced to sources and sinks to focus government policy and industrial practice. The current volume of gas
collected in the AirCore® sampler results in cavity ring‐down spectroscopy measurements with a precision of
0.2 ppm in a naturally occurring background concentration of about 390 ppm for CO2, and 2 ppb measured in
background concentration of 1800 ppb for CH4. Reduction of the AirCore® sampler to a size suitable for the
Skywisp® will require a different means of analysis which can provide sufficient accuracy with the smaller
volume of collected air. Mass spectrometry can provide the sensitivity needed and can measure many
components simultaneously. However, precision provided by a typical mass spectrometer may not be suitable
for all applications.
Miniaturization of the AirCore® has resulted in a simple, effective, low resource, reusable, and low cost
sampler with the ability to provide temporal and spatial resolution of a continuous air sample. This device,
called Advanced Resolution – Miniaturized Air Plug (AR‐MAP), can be used for land‐based (horizontal)
measurements as well as for the vertical measurement of GHGs in the atmosphere. The resulting
time‐resolved 3‐dimensional profiling can be used to create chemical maps with a limited number of discreet
samples, greatly reducing effort and cost. This is applicable to many functions including the identification of
unknown sources of toxic chemicals and the profiling of chemical plumes for the verification of models.
The miniaturized device consists of a long (30 m), thin fused silica capillary tube (0.53 mm i.d.) with lightweight
valving on both ends. The AR‐MAP is evacuated prior to the collection of the air sample at a very low flow rate.
Due to the high aspect ratio of the tube, the collected gas remains ordered, preserving the spatial and/or
temporal resolution. Diffusion of the gas occurs only very slowly. Field or laboratory analysis of the tubes
contents can occur by mass spectrometry to provide simultaneous measurement of many components. Each
basic reusable unit can be assembled for under $500.
To validate the AR‐MAP in the laboratory setting, a custom laboratory apparatus has been designed, built and
tested. Results demonstrate that slugs of gas delivered to the tube in regular intervals are recoverable upon
analysis; therefore, memory of the air sampled is maintained. In addition, 13CO2 and CD4 peaks co‐maximize
indicating that no chromatographic retention is occurring for these GHG’s. For other pollutants such as
chloroform and benzene, a small chromatographic effect is occurring; for field operation, results can be
corrected by application of a retention factor. After storage for three hours at ambient temperature, the
longitudinal diffusion along the length of the tube was found to be equivalent to 5.6 cm/hour for chloroform.
Initial estimate of LOD shows this device is readily capable of limits of detection in the ppb‐regime. Results to
be presented include: 1) spatial and temporal resolution of collected air; 2) resolution as a function of altitude
and storage time; 3) sensitivity, accuracy and precision of mass spectrometric detection; 4) configuration for
SkyWisp® flight; and 5) field demonstration.