observations results in a significantly greater improvement compared to the addition of

temperature or pressure observations alone. However, global wind measurements,

particularly above the surface, are only provided by 12 hourly rawinsonde launches from

selected locations, primarily over land. For many years, the world's oceans were “data

voids” in terms of wind measurements. Only recently have satellites begun to fill this

gap. The SeaWinds scatterometer on the QuikSCAT satellite obtains winds referenced to

10 meters above the surface over the global oceans under nearly all weather conditions.

The wind speed and direction data from QuikSCAT have been extensively tested against

surface observations and are of such quality that these data are routinely assimilated into

numerical weather prediction models run by both the National Center for Environmental

Prediction (NCEP) and the European Centre for Medium Range Weather Forecasting

(ECMWF).

However, scatterometer data alone only provide wind information near the ocean surface.

This information can be complemented with satellite cloud-track winds that provide

information about winds in the free troposphere over the ocean, as well as over land,

where scatterometer data are not available. In particular, the height resolved cloud

motion vectors from the Multi-angle Imaging SpectroRadiometer (MISR) instrument on

the NASA EOS Terra satellite yield wind speeds for clouds at altitudes less than

approximately 2.5 km that are shown to compare favorably with the QuikSCAT winds

globally. In addition, the direction of the MISR winds is similar to the QuikSCAT wind

vectors when compared on the same basis. The synergistic use of these two sets of wind

observations has the potential to make possible a variety of new studies: from improved

forecast and climate model validation; to increased understanding of tropospheric water

vapor transport; to observations of the coupling between the ocean surface and lower

atmosphere in a variety of conditions, such as during strong El Nino or La Nina events.