Factors Influencing MAPX Calculations
This section covers the evaluation
of multisensor precipitation estimates to be used in the computation
of basin average precipitation (using a procedure known as MAPX).
After completing this section, the reader should know:
This section is NOT intended
to be an all encompassing lesson on the WSR-88D system. In general,
it is fair to say that radar gives a good picture of where it
is raining. Calibration issues and other phenomena make the
quantity estimates somewhat more problematic. This does not
imply that radar estimates are incorrect; however, the precipitation
estimates derived purely from radar often differ considerably
from gage values. Fortunately, multisensor precipitation estimation
(MPE) tools are available to produce data sets which capitalize
on the strengths of both radar- and gage-based information.
Relatively speaking, radar
is one of the newest tools in measuring precipitation. The
current radar systems are “Weather Surveillance Radars – 1988
Doppler” (WSR-88D). There are currently more than 160 active
WSR-88D sites, as illustrated in Figure 1.
1 – WSR-88D Locations