There is no known missing data.
K. Trenberth, J Olson and W. Large have prepared a new climatology of surface wind stress over the oceans which has the advantage that it also features month-by-month mean fields for nearly seven years.
The wind stress statistics over the southern oceans are believed to be the most reliable available and there are quantitative differences from previous results elsewhere. The main shortcomings with the current results appear to be in the tropics. Also of note is the use of the Large and Pond formulation of the drag coefficient which has significant differences from several used previously.
The new climatology has significantly different features than in Hellerman and Rosenstein (1983) and the independent analysis of sea level pressures supports the view that many of the differences in the NH are due to real climate variations on a decadal time scale. As well as indicating the need for caution in using any fields in the ECMWF climatology, such changes have strong implications for the oceans because the two climatologies would result in quite different Gulf Stream and Kuroshio circulations. Although the oceanic adjustment time-scales are fairly long, significant changes would occur over a decade and call into question any assumptions of an oceanic steady state, such as is implied in some of the World Ocean Circulation Experiment strategies for sampling the ocean.
The highly significant and strong changes in the NH winter in the winds and pressures also have implications for interpreting trends in surface temperatures, which are of considerable interest because of the prospect of global warming associated with the buildup in greenhouse gases in the atmosphere. The results emphasize once more the conclusions of van Loon and Williams (1976, 1977) concerning the important role of the planetary scale waves in the NH and the spatial unevenness of the changes, as warming is apt to occur in the regions of increased southerlies and cooling in regions of increased northerlies. At the same time, there are added complications from mixing in the oceans and the additional heat storage (as manifest as positive or negative SST anomalies) compared with the land. The depth of the mixing plus the heat capacity of the oceans means that the anomalies may persist long after the conditions that created them have ceased. Inevitably, these factors will complicate any interpretation of the surface temperature changes in terms of global warming.
They have further shown that the wind stress varies considerably from year to year. Strong variations associated with the 1982-1983 and 1986-1987 El Nino events are evident in the tropical Pacific and NH, and the North Pacific in particular. In the SH interannual variations are not as large but still significant.
References:
Hellerman, S. and M. Rosenstein, 1983: Normal monthly wind stress over the world ocean with error estimates. J. Phys. Oceanogr., 17, 1093-1104.
NCAR Tech Note TN-338+STR, "A Global Ocean Wind Stress Climatology Based on ECMWF Analyses", K. Trenberth, J. Olson and W. Large, 1989.
van Loon, H., and J. Williams, 1976: The connection between trends of mean temperature and circulation at the surface: Pt. I. Winter. Mon. Wea. Rev., 104,365-380.
van Loon, H., and J. Williams, 1977: The Connection between trends of mean temperature and circulation at the surface: Pt. IV. Comparison of the surface changes in the Northern Hemisphere with the upper air and with the Antarctic in winter. Mon. Wea. Rev., 105, 636-647.