2.0 STERAO-A: Data Quality Review

Surface meteorological instruments are deployed prior to each Mobile CLASS launch. A description of the Mobile CLASS surface meteorological instrumentation is available in hardcopy and on the "web" (see Chapter 1.0 subsection: "Additional Information Regarding the Facilities").

During the STERAO-A project there were a number of instances where the surface "met" temperature was missing of clearly in error. In those cases, surface sonde values were substituted in project post-processing. Note that care was taken to substitute a reasonable sonde value. See the section on individual sounding data quality to see when this was done. In other instances, the surface temperature may have also a little high but was not changed as these instances were not as clear cut. One can see this situation in a number of the skew-T plots in Appendix B.

2.2 Radiosonde Data

Most of the soundings made had good data recovery. There was very little lost data and only occasional periods of bad data. The periods of bad data were usually of short duration. The overall Loran-C wind data recovery was reasonable during the project. There were periods of bad Loran-C wind data during the project. Typically these periods were at, or shortly after launch, related to either loss of navigation lock or never fully obtaining navigation lock at launch. These periods are identified in the following section.

Note that at times when these bad Loran-C winds occur, they can be associated with acceptable "Q" values. This is a function of the fact that the "Q" value is nothing more than the standard deviation of the wind data over the smoothing interval used for the wind data calculation. (See "SSSF Observing Facilities: Description and Specifications".) It is possible for the navigator to generate bad data over a sufficient period to produce bad winds with an acceptable standard deviation. The investigator should be aware of this situation and use the "Q" values with caution.

The thermodynamic sensors performed reliably throughout the project. There was virtually no lost data due to a pressure sensor failure. The temperature and humidity sensor performance was good as well.

Data recovery or availability is represented graphically in Appendix A. This presentation is derived from the "Ten-Second Data" file. Sounding data losses can be associated with problems in various system components. In the case of no data, or intermittent data, it is likely due to a failure of some type in the sonde, commonly a transmitter problem or an antenna problem. In the case of missing or bad wind data the problem is most likely associated with the Loran-C reception by the sonde or relay of that signal to the ground station.

Appendix B includes skew-T plots of the individual soundings as well as calculated stability parameters for that sounding. Appendix C provides plots of both theta and mixing ratio versus height.

2.2.1 Stability Parameters
Note that the stability parameters included with the Skew-T plots of Appendix B are generated from temperature and moisture data over the lowest 50mb (near surface) of the sounding. If the low level temperature and moisture data are not accurate, the stability parameters will be directly affected. Anytime there is a questionable stability parameter, that will be documented in the individual sounding data quality section which follows.

2.2.2 Individual Sounding Data Quality
The following information provided for each sounding is in reference to the "Interpolated Data" file produced. The Skew-T plots provided (Appendix B) are also plotted from that "Interpolated Data" file. The filenames for each listed sounding follow the standard naming convention: imddhhmm.xxx. Here, i stands for "Interpolated Data" file, m is a one digit indicator of the month, dd is the day, hh is the hour, mm is minutes past the hour, and xxx is a site id.

The "COMMENTS ON DATA QUALITY:" are included to address and explain problems encountered in the sounding data. Although, effort is extended to cover as many data problems as possible, it is certain that not every bit of spurious data will be addressed herein. It is hoped that the comments provided will give the investigator using this data a good understanding of the possible problems that are sometimes encountered and an overall feel for the system and sensor performance.

Note that general comments about the data, not necessarily regarding problems, are also included with these comments.

STERAO-A Mobile CLASS:

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