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3. DATA SETS Data sets for the various experiments have been selected from recently conducted major field research programs with comprehensive, multi-parameter observational systems including CCOPE (Cooperative Convective Precipitation Experiment), HIPLEX (High Plains Experiment), GATE (GARP Atlantic Tropical Experiment), COSE (Colorado Orographic Seeding Experiment), PEP (Precipitation Enhancement Program), and the Alberta Hail Project. Table 2 summarizes the observational data sets proposed for each numerical experiment by date, field project, and lead observational scientist. 3.1 Model Verification against Observations Numerical simulations in these experiments w'ill be designed to verify numerical models with available observational data. Cases selected for these experiments have a reasonably complete set of observations required to initialize and verify the most fundamental model calculations and physical processes described in model simulations. Two types of cloud system (convective and orographic) will be studied in open and closed experiments. 3.1.1 Convective cases 3.1.1.1 Open data sets 3.1.1.1.1 Liquid microphysical processes only A. Gate 226 - August 14, 1974 On August 14, 1974 a line of cumulus congestus clouds developed in GATE. This cloud line persisted for a number of aircraft penetrations and observations which provided excellent documentation of th,e boundary layer structure and some microphysical information regarding the evolution of precipitation. This was selected as a case for study because of the reasonably good initial conditions available and the warm cloud structure observed. A successful mission involving four aircraft was flown through a small but persistent line of towering cumulus. The line was oriented in a northwest to southeast direc- tion and ran from the ship Oceanographer to the ship Gillis and beyond. The purpose of the mission was to study the structure of the boundary layer in relation to the line of convection. The aircraft involved were the NCAR Electra, the UK C-130 (the aircraft the author was aboard), the NOAA DC-6 and the Frl~nch DC-7. The first three aircraft were equipped with inertial navigation systems (INS) and gust probes which insured high quality wind measurements and fluxes, respectively. Although the DC-7 did not have a gust probe, it was equipped with an INS. All aircraft had instrumentation for measuring the usual thermodynamic variables - temperature, pressure and dew point. In order to accomplish the scientific objectives, the flight plan called for repeated crossings of the cloud line at numerous altitu- des. The Electra and the C-130 flew repeated patterns in formation at 30 and 150 meters for the Electra and 330 and 450 meters for the C-130. The DC-6 flew 7.