1. Climate Data Assimilation System I (CDAS-1)

Here you will see the monthly diagnostic surface runoff and soil moisture fields from NOAA NCEP-NCAR Climate Data Assimilation System I (CDAS-1). The CDAS-1 runs from Jan 1974 to present (May 1997, currently). The spatial distributions of surface runoff and soil moistures (0-10, 10-200 cm two layers) in four months in 1996 are shown in the following plots.

The unit for surface runoff is kg/m^2/day, and for soil moisture is volumetric fraction.

2. Water Mass Balance & Global MSL Prediction

The TOPEX/POSEIDON altimeter provides accurate determination of global sea surface topography. The global mean sea level (MSL) variation with long term trend removed may tell us the water mass redistribution among the atmosphere, continents, oceans, and ice sheet. Using the available information from GEOS-1, CDAS-1, TOPEX/POSEIDON, and WOA94, we could almost perfectly predict the observed seasonal global MSL.

The global MSL variations are predicted by integrating water mass variations in the atmosphere (GEOS-1), in soil moisture (0-200 cm depth, CDAS-1), and in the snow depth variation in Antarctica, Greenland, and regions with latitude higher than 70 N (also from CDAS-1). The global MSL variations induced by thermal expansion are estimated using the objectively analyzed temperature fields in the World Ocean Atlas 1994 (WOA94). With the steric MSL variation removed, the residual global MSL matches quite well with the predicted MSL (See the following plot).

3. Impact of Sea Level Variations on Polar Motion

This is a comparison between ocean excitation functions derived from TOPEX/Poseidon (cycle 2 - 168) with observed polar motion excitations with atmosphere and land water contribution removed. Since only monthly surface pressure fields are available for this period (01/1993 - 04/1997), some of the high frequencies in the residuals are from the atmosphere.

Email: cjl@maestro.geo.utexas.edu