THE CLIMATE ADJUSTMENT PROCESS - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 163

Figure 12-6. The ASOS station at Albany Airport, Albany, New York, USA. Source: National
Oceanic and Atmospheric Administration (NOAA).

The analyst should be wary of MCP adjustments, especially upward adjustments,
of more than 4% based on a year or more of on-site data, as they may reflect
problems in the reference data. Observed trends should be confirmed with at
least two or three independent sources of reference data.

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12.3 SOURCES OF REFERENCE DATA

Most sources of reference data fall into one of four general categories: tall tow-
ers instrumented for wind resource assessment, surface weather stations, rawinsonde
stations, and modeled data sets. This section discusses some of the pros and cons
of each source of reference data and provides guidance on how the data should be
used.

12.3.1 Tall Towers Instrumented for Wind
Resource Assessment
It is unusual, but not impossible, to obtain data from tall towers with a sufficiently
long record to be useful as reference data sets for MCP. So long as the data prove to
be well correlated with the target site and homogeneous through time, they can be an
excellent reference. The analyst should be aware of gaps in the data record, as well as
possible changes in the anemometers and their mountings and heights. The possibility
that wind turbines may have been installed near the tower (a distinct risk given that
many such towers are in areas of good wind resource) should also be verified. If