CLIVAR/GEWEX COARE98 Conference Summary

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A Decade of Progress on the Western Pacific
Warm Pool Coupled System:
The CLIVAR/GEWEX COARE '98 Conference

Roger Lukas, U. of Hawaii, USA            Frank Bradley, CSIRO, Australia


More than 150 meteorologists and oceanographers from eight nations met in Boulder, Colorado from 7-14 July, 1998 to share results of their research using TOGA COARE (Coupled Ocean-Atmosphere Response Experiment) data, and to assess the impacts of the experiment which was conducted in the western equatorial Pacific from November 1992 through February 1993. The team of COARE scientists collected unique, high-quality observations of the upper ocean, the air-sea interface, and the atmosphere in the warm pool region. Based on the Conference, a much better understanding of the coupled ocean-atmosphere system in the tropics will result.


Scientific sessions addressed:

  • large scale coupled aspects of the Western Pacific warm pool (including its east-west migrations as part of ENSO) including predictability

  • the dynamics and air-sea interactions of the 30-60 day intraseasonal oscillation (ISO), which is particularly strong over the warm pool

  • precipitation, radiation and clouds, and the organization of convection

  • diurnal variability in the warm pool system

  • air-sea fluxes and budgets of heat, freshwater/salt, and momentum

  • warm pool response to wind and buoyancy forcing

  • parameterization, and multiple scale interactions.


Invited presentations reviewed progress towards the four goals of COARE, and assessed the legacy of COARE for CLIVAR, GEWEX, numerical weather prediction, satellite remote sensing, and in situ observing technology. Significant progress has been made in synthesizing the results of COARE research, and a substantial legacy has been left in the form of the datasets, the literature (more than 200 papers to date), improvements to the hierarchy of models, and improvements to observing systems and their application (e.g., new bulk flux algorithm improves use of bulk met observations; new satellite retrieval methods).


Highlights of the scientific discussions were

  • closure of interfacial, ocean and atmosphere budgets of heat and moisture to better than 10 Wm-2 and 25% of the rainrate, on biweekly and longer time scales;

  • determination of flux component phasing during the ISO and the identification of the importance of air-sea interaction within the ISO;

  • the success of cloud-resolving models at simulating realistic cloud structures and surface fluxes;

  • significant progress towards improving the physical basis for convective parameterization in atmospheric GCMs using COARE observations together with cloud resolving and single-column models;

  • evidence for the potential importance of high frequency forcing, such as diurnal heating, in governing longer-term SST tendencies;

  • demonstration of the need to consider the role of freshwater flux, the depth-dependent absorption of solar radiation, and the shallow thermohaline variability when predicting SST in the warm pool;

  • new insights into mixing processes and the evolution of turbulence in the upper ocean, made possible by the abrupt capping of the upper ocean by stable, fresh layers during heavy rain;

  • the relative importance of air-sea interaction and wind-forced Kelvin waves in the warm pool as compared to reflected Rossby waves during the onset of some ENSO warm events, including the 1997-98 event;

  • the impact of the COARE dataset and resulting parameterizations on numerical weather prediction analyses and forecast skill; and

  • the resolution of the global Vaisala rawinsonde humidity problem discovered during COARE.


A remarkable aspect of COARE '98 was that many new investigators joined those who had spent much of the last 10 years to develop, conduct and analyze the experiment. Significant modeling efforts are underway, motivated in large part by the high quality dataset collected during the COARE IOP, and early results are extremely encouraging. Observers are becoming involved in some of these efforts as full partners in numerical experiments to test hypotheses which COARE was designed to test. Oceanographers and meteorologists renewed their collaborative efforts to understand and model the processes important to the coupled warm pool system. The free and open access to the data from the IOP initiated by the COARE Project Office has led to its widespread use. A committee worked prior to and during the meeting to specifically identify gaps and unfulfilled objectives, and to suggest methods for dealing with them. Considering these as opportunities for programs such as CLIVAR and GEWEX, the most compelling are

  • development of an improved convection algorithm for atmospheric GCMs to link with the COARE Bulk Flux algorithm;

  • identify the source of dry air intrusions in the warm pool region, and their influence on the troposphere and convection;

  • a quantitative description of warm pool oceanic variability on 100km to 1000km scales;

  • inclusion of the hydrological cycle in coupled models that are capable of simulating mean and varying conditions in the warm pool region;

  • understanding the principal mechanism of air-sea coupling in the ISO;

  • understanding of convection under suppressed conditions and the transition to the active phase;

  • accurate time series and small space/time scale flux fields for forcing ocean models and for validating atmospheric models;

  • Examination of low wind conditions and horizontal variability of SST;

  • Assessment of the importance of mesoscale convective systems in controlling the local and remote evolution of upper ocean temperature, salinity and current structure;

  • Development of a reference surface for altimetry analysis of surface currents;

  • Inadequate salinity measurements to fully explore the salinity variability and influence on ocean dynamics;

  • Transitioning the COARE bulk flux algorithm to operational NWP models, and the scaling of the parameterization to larger domains with extension to wind speeds >12 m/s;

  • Insuring that results from COARE are used to improved turbulence, convective and radiative parameterizations in operational and coupled climate models;

  • Explicit consideration of the optical properties of the upper ocean and their role in governing SST;

  • Extension of COARE results and parameterizations to other regions (eastern Indian ocean, eastern Pacific);

  • Comparison of COARE data and results to that of other field experiments past and future to expand the range of conditions that can be studied;

  • Determination of the role of microphysical cloud processes in convection;

  • Mesoscale data assimilation of shipboard radar data; and

  • Implementation of rawinsonde humidity correction procedures for the global historical dataset.


Focused working group meetings continued or initiated efforts to address some of the major remaining challenges, and to expand the applicability and application of COARE results. The GEWEX Cloud Systems Study Working Group 4 met during the conference. A group met twice to develop a proposal to the WCRP to set up a Coupled Ocean-Atmosphere Boundary Layer working group to expand on the success of COARE and focus on continued improvements in the boundary layer parameterizations in climate and NWP models, and in air-sea flux climatologies. Another group met to develop plans towards assimilation, analysis and modeling of COARE upper ocean data.

In summary, the consensus of COARE98 was that COARE has been a huge success. The design and execution of the COARE IOP was successful, and the investment made in the resources that collected the data are beginning to have a tremendous return. While certain objectives remain to be met, progress has been rapid. It is believed that most of the identified remaining challenges are highly relevant to the scientific objectives of CLIVAR and GEWEX, so it is hoped that these programs will continue to assimilate COARE results and investigators. The proceedings of COARE98, including the review papers and extended abstracts of the contributed papers, will be published as a WCRP Report.

To COARE98 Web site