The seven aircraft participating in TOGA COARE were in two main groups; turboprop aircraft capable of flying at lower levels and at slower speeds, and jet aircraft flying at high altitudes (> 6 km [20,000 ft]) at higher speeds. The flight tracks and coordination of the aircraft varied according the class of convection being investigated. [For details see the TOGA COARE Operations Plan (TCIPO 1992)]. The idea in class 0-1 missions was to map the boundary layer by either a single aircraft or a multiple aircraft "armada" pattern in which two or more planes flew at low levels (below 0.5 km). The turboprop aircraft arrived in close formation at a designated location in the vicinity of research ships and instrumented moorings and then spread out horizontally to map the boundary layer over a ~20,000 km^2 area. While the turboprop aircraft were mapping the boundary layer, airborne Doppler radar measurements were made of any small precipitating convection. In the more convectively active (class 2-4) cases, the turboprop aircraft emphasized airborne Doppler-radar documentation of the structure of the deep precipitating cloud and remained in the vicinity of the precipitating clouds rather than spreading out horizontally. In missions during the later half of the Intensive Observation Period (IOP), jet aircraft were flown at upper-levels in coordination with the lower-level flying turboprop aircraft to document radiation, temperature and precipitation structures.
The basic aircraft plan of boundary-layer armadas and airborne Doppler-radar measurements was executed by the two National Oceanic and Atmospheric Administration (NOAA) WP-3D aircraft and the National Center for Atmospheric Research (NCAR) Electra during the entire four months of the field phase of TOGA COARE. These three turboprop aircraft were staged out of Honiara, Guadalcanal, Solomon Islands. During the last two months of the project, these turboprop aircraft were joined by the National Aeronautics and Space Administration (NASA) jet aircraft, the DC-8 and the ER-2, which were staged out of Townsville, Australia. These aircraft flew in close coordination with the turboprops. The NASA DC-8 provided cloud physics and radiation coverage in the upper portions of the convective cloud systems, as well as carrying ARMAR, a downward-scanning Doppler radar that is a prototype for the Tropical Rainfall Measuring Mission (TRMM) satellite radar. This radar provides additional measurements of the structure and intensity of the precipitation observed simultaneously by other radars aboard the turboprop aircraft and on ships. The NASA ER-2 operated primarily above cloud top level providing high altitude remote sensing measurements with several radiometers, a lidar and a multispectral scanner.
The United Kingdom Meteorological Office C-130 aircraft also participated in the flight plan described above by augmenting boundary-layer mapping on several flights during January 1993. Additionally, single aircraft boundary-layer flights were flown by the Flinders Institute for Atmospheric and Marine Sciences (FIAMS) Cessna (C-340) aircraft based out of Rabaul, Papua New Guinea. The NCAR Electra also flew a large number of single aircraft missions. The single aircraft missions of the FIAMS C-340, the UK C-130 and the NCAR Electra helped fill in information on days between coordinated multiple aircraft missions. All the missions, involving either single and multiple aircraft, are included in the electronic atlas.
To indicate where the missions were generally flown, figures overlaying all the WP-3D flight tracks for the primarily boundary-layer missions (classes 0-1) and convective missions (classes 2-4) were constructed. The class 0-1 missions were all conducted over the IFA. In contrast, the class 2-4 missions were spread over a larger area to capture the large convective systems wherever they presented themselves. The reason for this is that the larger cloud systems were much more infrequent and had to be sampled wherever they occurred within range of the aircraft.
The final tally of samples by class is also summarized in one figure. The sampling of classes 0-1 was enhanced by additional flights by the FIAMS C-340 and the UK C-130. Given the difficulties of forecasting the rare occurrences of the larger systems, the planning of aircraft missions based on imperfect forecasts, the fact that the lead time in planning and launching a mission is of the order of the time scale of the cloud systems, logistical problems associated with operating in a developing country, and other factors, the sampling is reasonable. Not surprisingly, most cases were obtained in classes 0 and 1. The number of class 3 and 4 cases was as large as was possible under the difficult experimental constraints.