APPENDIX III- 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), H2O, and ozone; this description is intended to apply to the determination of their vertical profiles.

Independent Evaluation of the Instrument Design and Data Analysis

Before a formal intercomparison with a certified instrument can be planned, the Investigator should supply documentation addressing the following points to the NDACC Steering Committee's Microwave Working Group (MWWG) or designated representative. In some cases, this documentation may be 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 backing from his/her home institute. Also, the Investigator must be willing (within reason) to deploy the instrument at an NDACC Steering Committee-selected site.
• A document completely describing the instrument and data acquisition procedures should be provided for review. In particular, this document should emphasize calibration procedures.
• An algorithm description document also should be submitted. This document should describe the forward model, retrieval model, and method of error analysis. It also should show that the spectroscopic database is current.

Once the instrument has been accepted into the NDACC, the intercomparison process can begin. 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. In general, completely invalidated instruments will not be accepted into the NDACC.
• If there are other NDACC instruments measuring the same constituent, side-by-side data validation campaigns should be planned.

• The Investigator must deposit data into the NDACC archive on a regular basis.
• The experiment documentation files in the NDACC archive should be kept up-to-date.
• The Investigator should participate in the ongoing forward model and retrieval algorithm intercomparisons in order to ensure that the algorithms, as well as 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 should also certify and describe the ways in which each of the above requirements have been met.

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 which may affect the results. Once the regular operation of a primary or complementary instrument has begun, such changes should not be undertaken lightly; consultation with the MWWG is recommended. The primary data (interferograms or spectra) should be retained by the Investigator 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.