Dropwinsondes (over 2000) launched over the eastern and central equatorial Pacific during the First GARP Global Experiment (FGGE) have been used to develop a comprehensive description of boundary layer structures for this region. The results from several studies based on this FGGE data set will be compared with results from GATE boundary layer studies. A principal finding of the FGGE studies has been the high frequency of occurrence of inversions at the 800-850 mb level that inhibit deep convection. Although these inversions occur most frequently over the more stable areas to the south of the ITCZ, they are also observed frequently over in ITCZ. These inversions show little longitudinal or latitudinal variation with height. During GATE there was an emphasis on defining the characteristics of the stable layer at cloud base--the transition layer-- that is critical in defining the cloud-subcloud layer coupling. The transition layer was
observed in about 45% of the FGGE soundings. As in the GATE area, this layer is observed near the height of the subcloud layer LCL. In a recent study, the FGGE soundings with transition layers were composited using a normalized height scale that preserves the structure of the transition layer. The average difference in virtual temperature across the transition layer was about 0.9 K and was found to be remarkably constant over the wide range of longitude and latitude in the FGGE study area. Differences between the thermodynamical characteristics of soundings with and without the
transition layer are being used to consider the possible mechanisms
responsible for the formation and the maintenance of this layer