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Written: April 24, 2008 - page 21 / 31





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One of the most important tasks during a flight is quality controlling the incoming data.  After checking the release point data, go to “Messages” -> “Check.”  This message box will display warnings for abrupt changes in data during the current flight between data points or in comparison to the previous flight.   

Pay particularly close attention to any messages regarding superadiabatic lapse rates.  These conditions will often exist near the surface, however, the magnitude should always be questioned.  For example, a message stating that there exists a temperature lapse rate of “303 deg C/km between 0.00 and 0.02 minutes” is not realistic.  If this occurs in the very near surface levels, try changing the release point until the message goes away or a more acceptable lapse rate is obtained.  If changing the release point makes the lapse right higher or is still unacceptable, the temperature data can be smoothed in the “Processed Tabular Display” similar to how the RH data was smoothed.  Typically, in these cases of superadiabatic lapse rates immediately following launch, only 2-3 points should need to be smoothed.  On a temperature plot, a superadiabatic lapse rate is depicted by a line sloping sharply from right to left.

A superadiabatic lapse rate later on in the flight is most likely indicative of a bad temperature sensor, and termination of the flight should be considered.  If time permits and the flight has not reach a legal level (400 hPa), a second release should be attempted.  See Chapter 5 for second release procedures.  In this case, flight termination also requires sonde rejection.  See Chapter 6, Section A for radiosonde rejection procedures.

The MkIIA radiosonde has a problem with the humidity sensor.  In particular, it has a dry bias.  The value for RH at time = 0.0 minutes is generally much higher than the following values.  There a couple of corrective actions that can be taken.  First, check the dewpoint temperature and relative humidity in the surface observation.  If the launch site is sufficiently close to another observing site, such as an ASOS site, compare the observations.  If the dewpoint or humidity from the ASOS is a more representative observation, modify the initial values accordingly.  To change the surface dewpoint, or any aspect of the surface observation, go to “Tools” -> “Modify Surface Ob.”

Often, further action must be taken to correct the dry bias.  In the “Processed Tabular Display,” scroll to the right until you find the RH column.  Note that any column in red can be edited in the following manner.  Left-click on the point where you want the data to begin to be smoothed.  The point at t = 0.00 minutes cannot be selected.  Hold down the left mouse button and drag down in the data until you get to the point that you want.  The data should now be colored maroon.  Right-click and select Apply User


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