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Problem in the data?

There are several shortcomings of radiosonde data that can interfere with estimation of trends:

0) Poor, uneven coverage by sampling sites

1) Changes in instruments.

2) Irregular sampling at available sites (twice vs. once daily, changes in frequency, down periods, censoring)

Each of these can bias trends. For example, variations in data density can correlate with atmospheric variations. Changes in instrument can obviously introduce spurious trends.

Item (0) we deal with here by including as many stations aspossible; the trick then is to carefully handle (1) and (2), especially when using stations that don't report all the time. We use data from March 1985-Feb. 1999.

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