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A unique and most important measurement capability of GIFTS is that
wind profile information can be obtained from the observed horizontal
displacements of cloud and water vapor profile features since they are
observed with high spatial and time resolution. Wind profile estimates
can be diagnosed through the direct time assimilation of GIFTS
radiance measurements, or the retrieved temperature and water vapor
profile data, in a mesoscale numerical model. Alternatively, vertical
profiles of wind velocity can be estimated by tracking the horizontal
displacement of features in the retrieved water vapor profiles. A
similar approach is now used operationally; however, the current GOES
application only provides upper tropospheric winds by tracking the
horizontal displacement of features in the geostationary satellite
infrared water vapor radiance imagery.
GIFTS will provide substantial improvements of the wind field in several ways. Clouds will be more accurately located in altitude using high resolution spectral radiances in the application of CO2 slicing and H2O intercept techniques. Water vapor tracking can be done using the high vertical resolution water vapor profile mixing ratios assigned to isentropic, isobaric, or height surfaces, thereby, alleviating the height assignment problem. (The advantage of using isentropic rather than isobaric or constant height surfaces is that moisture features will be conserved in cloud-free areas where the vertical motion is largely adiabatic.) The high vertical resolution of the GIFTS will provide vertical profiles of wind, rather than single layer estimates. |