Vertical displacement of the mid-tropospheric water vapor boundary in the tropics derived from the VISSR Atmospheric Sounder (VAS) 6.7-micron channel

A technique for locating areas of upward or downward motion of the upper boundary of the midtropospheric water-vapor envelope over tropical oceans on the basis of GOES Visible/IR Spin-Scan Radiometer (VISSR) Atmospheric Sounder (VAS) 6.7-micron brightness temperatures is developed and demonstrated. The technique employs an analogy to the method developed by Schoeberl and Krueger (1983) for the bottom of the ozone layer and depends on the relationship investigated by Chesters and Uccellini (1982) between 6.7-micron brightness temperature and the pressure of the water-vapor upper boundary. The results of analysis of VAS data for the North Atlantic (20-40 deg N and 35-75 deg W) on September 5-7, 1982, are presented in maps which are shown to be physically consistent and in agreement with conventional upper-air measurements. Refinement of the method to account for horizontal advection and diffusion is suggested.