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2.2 Texas regional mosaic WSR-88D Level II data <br />Another useful tool during SPECTRA was the Texas regional mosaic IRaDS (IntegratedRadar Data <br />Services) WSR-88D Level II data. These National Weather Service (NWS) WSR-88D sites cover the <br />Texas weather modification programs’ target areas. NEXRAD data is run through Thunderstorm <br />Identification, Tracking, Analysis, and Nowcasting (TITAN) as a graphic user interface, enabling the radar <br />meteorologist to examine the three-dimensional structure of echoing clouds in real time. Individual echoes <br />and groups of echoes can be tracked and their development and motion projected in time. Airborne Data <br />Acquisition and Telemetry System onboard the research aircraft allows the radar meteorologist at each <br />seeding target to track the SOAR research aircraft on TITAN and vector the aircraft to regions of <br />enhanced convection within the Ultra High Frequency (UHF) range of the telemetry system. During the <br />field measurement program (phase 1), the SOAR research aircraft was mostly deployed in targets of <br />existing weather modification programs in Texas. This allowed the crew on the research aircraft to <br />communicate with the project meteorologist at each weather modification site in Texas to obtain <br />supplemental radar information to that available onboard the research aircraft. The aircraft flight tracks <br />can also be used to associate the cloud physics in situ data with the cloud radar echoes. <br />2.3 Operational procedures during SPECTRA 1 <br />During the SPECTRA 1 field campaign, the SOAR research aircraft was deployed in a region of <br />enhanced convection to conduct CCN measurements and subsequent measurements of drop size <br />distributions through the vertical development of the convective cloud. In order to achieve the program <br />objectives, the aircraft had to first measure the CCN and aerosol concentrations below cloud base, and <br />then proceed to penetrate the cloud formation in vertical steps to measure the microphysical properties of <br />the clouds. <br />Each morning during the contract period the Project Meteorologist prepared a weather forecast for the <br />whole state of Texas including the surrounding areas in New Mexico and Oklahoma. This forecast was <br />prepared by mid morning and addressed the probability of convection. When a certain level of certainty of <br />the probability of convection within a specified target area was determined, the aircraft was deployed to <br />the area of forecasted convection within the aircraft’s range. If the forecasted convection was beyond the <br />aircrafts range, then the aircraft was repositioned, and the forecast was updated. A priority was given to <br />the operational weather modification programs in Texas. <br />Once the aircraft was at the location where convection was forecast, the flight crew (consisting of the <br />pilot, flight meteorologist and flight scientist) waited at the airport and monitored the weather conditions <br />visually. During this period, a formal briefing was always planned so that the crew could discuss the <br />research objectives for this flight and design a flight profile that could best achieve these objectives. <br />When convective towers started to develop, the pilot filed an Instrument Flight Rules (IFR) flight plan and <br />scrambled to the aircraft for immediate departure. The aircraft departed towards the area of enhanced <br />convection and worked with the local air traffic authority to request clearance to maneuver in this area. <br />When the flight meteorologist or the flight scientist determined that the measurement objectives have <br />been achieved, the crew returned to the base airport. The procedure that followed was usually the <br />removal of the data from the aircraft data system. When the aircraft did not return to its home base, the <br />retrieval of data was not always possible. When the data was retrieved, plots were generated to check the <br />data quality. A flight report was written to record the flight scientists’ and/or field meteorologists’ <br />observations from the aircraft. If an instrument failure or malfunction was experienced during the flight, <br />then the field meteorologist usually trouble shot the instrument in the field. If a field repair was not <br />possible, then the instrument was shipped to the manufacturer. The flight scientist made the decision <br />whether the field program could continue with an instrument inoperative or whether the instrument was <br />required for the subsequent flight. <br />18 <br />