Measurements of hydrogen peroxide and methylhydroperoxide will be made using a new chemical ionization mass spectrometry (CIMS) instrument on board the NSF/NCAR Gulfstream V research aircraft during the Deep Convective Clouds and Chemistry (DC3) field campaign in May-June 2012. Measurements of the two peroxides will be made at 10 Hz allowing horizontal and vertical sample resolution on the order of 20 meters and 2 meters, respectively. Through-the-inlet isotopically-labeled standard gas additions will be made continuously to provide coincident calibration for both species under all encountered variations in pressure, temperature, water vapor and other environmental variables. Extensive pre-mission, integration, test fight, and deployment evaluations and comparisons will be made using a ground-based wet-chemical calibration system.
The DC3 airborne peroxide observations will provide: 1) distributions of these species in and around isolated deep convective clouds, 2) constraining data on odd-hydrogen chemistry in the upper troposphere and lower stratosphere, 3) constraining data on vertical transport of odd-hydrogen precursors by deep mid-latitude continental clouds, 4) constraining data on the scavenging of soluble species by cloud droplets and hydrometeors, 5) a probe of convected air-mass chemical aging in the upper troposphere with and without lightning-added nitrogen oxides, and 6) characterization of the variance of topics 1-5 across cloud-storm properties such as cloud base temperature, vertical velocity, freezing level and glaciation, and lightning. Results will be significant to tropospheric oxidant and ozone chemistry and their regional-to-global distributions; to heterogeneous gas-aerosol chemistry under cold, low specific humidity, and mixed sunlight conditions; to aerosol chemical evolution and their regional-to-global distributions; and ultimately to air quality and climate. The instrument system is novel and represents a significant advance in airborne peroxide instrumentation. One post-doctoral fellow, one graduate student and one or more undergraduate students will participate in the experiment. Data will be archived at the National Center for Atmospheric Research and results published in peer-reviewed journals.
