The NOAA Twin Otter and its role in BRACE: Platform description

This paper describes in detail the platform and equipment used to make airborne measurements as part of the Bay Regional Atmospheric Chemistry Experiment (BRACE). A De Havilland DHC-6 Twin Otter, operated by the National Oceanic and Atmospheric Administration's Aircraft Operations Center, was used to measure chemical and meteorological parameters during the BRACE field intensive in May, 2002. The Twin Otter flew more than 90 h on 24 missions during BRACE, measuring a suite of positional (latitude, longitude, altitude, azimuth, roll, pitch, velocity), meteorological (temperatures, pressure, 2D wind fields, dew point, UV radiation) and chemical/physical (O3, CO, SO2, CO2, NO, NO2, NOY, HNO3, CN, HCHO, H2O2, PAN, NMHCs, aerosol ionic composition, aerosol size) parameters. This manuscript describes the chemical and meteorological measurement systems, calibration procedures, and instrument performance specifications. Companion papers in this special issue present an overview and summary of results from the aircraft flights.