RELATIONSHIP BETWEEN SEA-SURFACE TEMPERATURE, VERTICAL DYNAMICS, AND THE VERTICAL-DISTRIBUTION OF ATMOSPHERIC WATER-VAPOR INFERRED FROM TOVS OBSERVATIONS

With the aim of better understanding the respective role of sea surfac e temperature (SST) and vertical dynamics on the vertical distribution of atmospheric water vapor, particularly in the tropics, global scale observations from NOAA 10, covering a 31-month period, have been proc essed using the improved initialization inversion ((3I) [Chedin and Sc ott, 1984]) retrieval method and interpreted in terms of tropospheric layered water vapor contents. The method of analysis uses the power la w, which expresses the specific humidity q at pressure p as a function of their values at the surface, q, and p(0); q = q(0)(p/p(0))(lambda) . This description is applied independently to three layers giving thr ee values of lambda: lambda(1) for surface-700 hPa, lambda(2) for 700- 500 hPa, and lambda(3) for 500-300 hPa. It is shown that lambda(2) is a good indicator of the large-scale vertical dynamics and gives result s equivalent to those obtained using the vertical velocity at 500 hPa issued from a model. Consequently, the role of enhanced upward motion with increased SST for the ''super greenhouse effect'' situations is c onfirmed as well as the contribution of externally forced subsidence o n the suppression of the deep convection for cases where SSTs exceed a bout 303 K. In addition, the influence of SST on the vertical distribu tion of water vapor is analyzed together with the large-scale vertical dynamics contribution. The results show that the rate of change of wa ter vapor content in the 700- to 500-hPa and 500- to 300-hPa layers wi th respect to SST increases with decreasing rate of change of lambda(2 ) with respect to SST, that is, with increasing rate of change of upwa rd vertical dynamics with respect to SST.