ORACLES Field Campaign

Tristan, Andrew, and Elin represented the University of Wisconsin as part of NASA's multi-million dollar ORACLES (ObseRvations of Aerosol above CLouds and their intEractionS) field campaign. The campaign was stationed in Walvis Bay, Namibia, where 19 instrument teams (over 100 scientists) gathered to study cloud/aerosol interactions and their effects on the global climate system. The Angola Basin--or the eastern South Atlantic Ocean just off the coast of Angola--is the best spot in the world to study cloud/aerosol interactions because a semi-permanent stratocumulus deck and seasonal biomass burning (aerosol) layer occur simultaneously at this location during the southern hemisphere's winter. By the end of the campaign, the ORACLES team collected the most extensive dataset in the world for studying a multitude of problems relating cloud/aerosol interactions on the global climate system.

Our group participants were a part of the Advanced Precipitation Radar--3rd Generation (APR3) team, which also included Simone Tanelli, Steve Durden, Ousmane Sy, Greg Sadowy and William Chun (all scientists from NASA's Jet Propulsion Laboratory). Tristan was a key member of the flight planning team. Given that the majority of instruments required the plane to either be in-cloud or within close proximity of either cloud boundary, Tristan would help determine flight legs where the APR3 team could gather continuous stretches of data at high altitude (optimally, the APR3 could only be operated at altitudes greater than 8000 ft) such that the needs of all instrument teams were met. Andrew and Elin supported the NASA JPL scientists in operating the APR3 radar. Elin also assisted in the integration and decommissioning of the APR3 at Wallops Flight Facility in Virginia.

The APR3 is an airborne radar system that can take simultaneous measurements at three different frequencies, the same frequencies corresponding to the space borne TRMM Precipitation Radar (13 and 35 GHz) and the CloudSat Cloud Profiling Radar (95 GHz). For ORACLES, the APR3 team will examine the data to determine precipitation frequency in the stratocumulus deck and, eventually, the role of aerosols in affecting precipitation frequency and magnitude. Previous studies have shown that light precipitation is a major benefactor to global energy exchange, yet current spaceborne observational platforms are limited in reliably estimating light precipitation. The ORACLES APR3 dataset will not only characterize light precipitation frequency and magnitude in tropical stratocumulus clouds; the triple frequency radar data will be critical toward improving CloudSat's 2C-RAIN-PROFILE algorithm by utilizing the 13 and 35 GHz data as an additional constraint when computing precipitation rates (this will one day be the subject of Andrew's Ph.D. dissertation!).