The Tendrils and Legacy of GATE (Invited Presentation)

Two large field tropical international expeditions occurred in the mid-20th century. The first, the International Indian Ocean Expedition (IIOE), organized as part of the International Geophysical Year was basically oceanographic with the aim of understanding the Indian Ocean circulation, a hitherto relatively dateless region. Some 45 research vessels from 14 countries were involved. The second, the GARP (Global Atmospheric Research Programme) Atlantic Tropical Experiment, originally set in the mid/western Pacific, occurred to investigate the structure of the tropical atmosphere with emphases on tropical convective organization and the mutual interaction between convection and larger scale flow. Scientists from some 70 nations were involved using 15 research aircraft and 40 research ships.

Each expedition produced scientific results and utilized sensing equipment that has influenced not only what we know about the tropics but how future missions were designed and where they were conducted. We will concentrate on the tendrils emanating out of GATE but we will also note that those arising from the IIOE and from GATE will intertwine and how they have profound influences on our understanding of the dynamic and thermodynamics of the tropics.

A host of coupled ocean-atmosphere expeditions followed GATE that allowed investigations its broader implications and to take into account regional influences. This was an important step as a number of key GATE scientists realized that there was uncertainty in the generalization of conclusions reached in GATE for the entire tropics. An example was the GARP Monsoon Experiment (MONEX) that had distinctive summer and winter components. There was some oceanographic guidance from the IIOE especially in the Arabian Sea and joint land-based Doppler radar at Bintulu, Malaysia together with dedicated aircraft missions allowed a much deeper extension of mesoscale convective systems observed in GATE. Importantly from the results of ancillary campaigns such as EMEX (Equatorial Mesoscale Experiment) held north of Australia allowed the realization that about 50% of rainfall occurred in the stratiform regions of the disturbance extending out well beyond the deep convection, altering the distributions of connective and radiative heating. The importance of these emerging distributions of heating and their strong diurnal variations on understanding

GATE and MONEX were designed and conducted before the implications of organized propagating equatorial disturbances described theoretically by Matsuno in the mid-1960’s and the Madden-Julian Oscillation were fully realized. Subsequent field expeditions, such as TOGA-COARE (the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Experiment) and DYNAMO extended the scientific procedures developed in GATE with this emerging dynamical basis.

In summary, the influences of the GATE tendrils have influenced the way we have developed knowledge in the last 50 years. And as new problems emerge, they will be engaged and investigated in the international, multi-platform platforms introduced in GATE. Such is its legacy.