Single component versus two-component Wind Experiment using GEOS-4
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This experiment was conducted by the GMAO and the GLA/SIVO OSSE
group under the lead of Dr. Lars Peter Riishojgaard.  It is
actually a unique type of OSSE in which real observations
are assimilated, but are manipulated in such a way that
the resulting observations are made to resemble those from
a new type of sensor.  In this case, wind measurements from all
conventional observing systems were modified for assimilation
to gain insight to the relative effects on an analysis of single
component winds from a possible future space-based lidar instrument.

The GEOS-4 DAS was modified to analyze only a single wind component,
either zonal or meridional, from all conventional winds input to
the DAS.  In addition, all mass data were removed from all of the
experiments.  The experiments include:
- Control (both U and V-wind components analyzed)
- Zonal wind (only U-wind component analyzed)
- Meridional wind (only V-wind component analyzed)

The DAS was executed for one month, Jan 2003, at one-degree resolution.
The resulting analysis fields from each assimilation were examined
statistically by means of RMS error comparisons.  The verification
data set was the GMAO operational analysis in which all standard
mass and wind data are included.  The figure below illustrates
the relative effect, on a long assimilation, of a single component
wind observing system versus a two-component observing system as well
as differences resulting from wind components of different direction
(i.e. zonal versus meridional).  This experiment, though idealized,
helps to quantify the impact of specific wind information on a DAS which
which will aid in establishing requirements for future lidar missions.