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APPENDIX IV - Microwave Instruments
APPENDIX IV - Microwave Instruments
The following covers the validation process for new microwave instruments, and the
criteria for maintaining existing instruments in the NDACC. The NDACC-designated
species measured by the microwave spectrometers are chlorine monoxide (ClO), water
vapor (H2O), and ozone (O3). This description is intended to apply to the determination
of their vertical profiles.
Quality Criteria for the Evaluation of New Instruments and Instrument Teams
Independent Evaluation of the Instrument Design and Data Analysis
The Investigator should supply documentation addressing the points below to the
NDACC Microwave Working Group (MWWG) or designated representative. In order to
simplify the application process, investigators are encouraged to supply this
documentation in the form of published research paper reprints.
- The Investigator must agree to submit data on a regular basis to the NDACC
data archive, and to abide by the NDACC Data Protocol. The Investigator also
must demonstrate a commitment to make long-term, high-quality measurements
with support from his/her home institute. Before being endorsed by the NDACC,
the instrument must have acquired measurements for a period of at least one
year. Instruments that are operated on a campaign basis are generally not
suited for NDACC unless the campaigns take place on a regular basis, e.g.,
during polar winter.
- A document completely describing the instrument and data acquisition
procedures should be provided for review. In particular, this document should
emphasize calibration procedures. Instruments must be calibrated against wellestablished
reference loads.
- The Investigator also should submit an algorithm-description document
containing information on the forward model, retrieval model, and method of error
analysis. It also should show that the spectroscopic database is current.
Instrument and Data Analysis Intercomparison
The following intercomparison procedures must be pursued to meet full approval as an
NDACC instrument:
- The MWWG has an ongoing forward- and retrieval-model intercomparison
activity. The Investigator should participate in this activity to help ensure that the
analysis algorithms are of acceptable quality.
- The Investigator should demonstrate the existence (and document the results) of
a continuing data-validation effort to establish that the measurement error bars
are approximately correct. A detailed error analysis similar to those given in
Rodgers (JGR, 5587-5595, 1990) or Nedoluha (JGR, 2927-2939, 1995) shall be
provided.
- While the preferred method of validation is a side-by-side campaign with another
NDACC microwave instrument, the MWWG recognizes that this is often not
possible. Comparisons against other NDACC ground-based instruments or
against well-established satellite instruments also are considered acceptable if
these instruments provide measurements over similar altitude ranges.
Quality Criteria for the Evaluation of NDACC-Affiliated Instruments and
Instrument Teams
The following guidelines must be followed to maintain NDACC affiliation:
- The Investigator must submit data to the NDACC archive on a regular basis.
- The experiment documentation files in the NDACC archive should be kept up-todate.
- The Investigator should participate in the ongoing forward-model and retrievalalgorithm
intercomparisons in order to ensure that the algorithms and the
spectroscopic databases are kept current.
- The Investigator should participate in regular data validation activities in order to
demonstrate continuing data quality and a good understanding of measurement
errors. Potential measurement biases should be flagged, and efforts to correct
them described.
- Each Investigator should submit a yearly report to the NDACC Steering
Committee. This report should give the current instrument status and also
should certify and describe the ways in which each of the above requirements has been met.
Changes in Instruments and Data Analysis
Since one of the major goals of the NDACC is the detection of long-term trends, care
should be used with any modifications of the instrument or data analysis that may affect
the results. Once the regular operation of an instrument has begun, such changes
should not be undertaken lightly; consultation with the MWWG is recommended. The
Investigator should retain primary data (interferograms or spectra) indefinitely (although
not deposited in the NDACC archive), so that improved data-retrieval processes,
including improved spectral line parameters, can be applied retrospectively to the earlier
data. In such cases, the entire dataset should be reprocessed and archived, along with
(at least) reference to earlier versions.
Version: April 14, 2009
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Page last modified: Wednesday, 08-Jul-2009 17:49:07 UTC
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