Observation of biomass burning plumes with the DLR Falcon research aircraft during DC3

The 2012 wildfire season in the U.S. is one of the worst in the past decade. Coinciding with the period of intense wildfires in the western U.S., the Deep Convective Clouds and Chemistry Experiment (DC3) was carried out in summer 2012 over the central and eastern parts of the United States. In addition to numerous ground-based radar, lightning and meteorological observations, three aircraft, the NCAR GV, the NASA DC8, and the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Falcon aircraft, based out of Salina, KS were utilized for airborne measurements. Here we focus on measurements from the DLR Falcon aircraft. The main objective of DC3 was a better understanding of thunderstorms and their impact on the chemical composition of the upper troposphere. However, the German DLR Falcon research aircraft also investigated numerous biomass burning plumes originating from the wildfires in Texas, New Mexico, Colorado, and Mexico. During DC3, the Falcon was equipped with a comprehensive in situ aerosol and trace gas instrumentation. The aerosol in situ payload included a multi-channel CPC, several optical particle counters of type Grimm SKY-OPC 1.129, UHSAS-A, PCASP-100X, FSSP-300, and FSSP-100. In addition, a multi-wavelength Particle Soot Absorption Photometer (PSAP) and a Single Particle Soot Photometer (SP2) were deployed. The non-volatile particle size distribution was measured using a heated inlet line with a thermal denuder. The trace gas instrumentation included measurements of NO, CO, O₃, CO₂, CH₄, SO₂, and volatile organic compounds. The DLR Falcon performed 13 local flights over Colorado, Wyoming, Kansas, Oklahoma, Texas, Missouri and Arkansas and detected biomass burning plumes in every flight. In addition, biomass burning plumes were detected during the transfer flight from Germany to the U.S. and on the way back. In most of the cases biomass burning aerosol was found at altitudes between 2 and 6 km, but in some cases extended smoke layers were also present in the upper troposphere between 9 and 13 km altitude and in the outflow of thunderstorms. During the transfer flight from the U.S. back to Germany on 18 June 2012, the Falcon followed a biomass burning plume at an altitude of 11 km between Canada and Greenland for more than two hours. Black carbon (BC) mass concentrations (size range: 70 nm - ~500 nm) in the biomass burning layers ranged between 0.1 and 1.5 µg m-3. Peak CO concentrations were as high as 700 nmol mol-1. From our SP2 data, we calculated the coating thickness of the BC particles in the biomass burning plumes and found particles with a coating thickness of up to several hundred nanometers, whereas the BC particles in the boundary layers had only minor coatings. Coatings on BC cores can enhance the absorption of solar radiation, and therefore amplify the climate impact of those aerosol layers. We present an overview of the microphysical and optical properties of the biomass burning plumes observed with the Falcon during DC3 and compare those properties with measurements of boreal and tropical biomass burning plumes taken in 2004 and 2008. We focus our presentation on the data taken on June 18, 2012 between Canada and Greenland and show the impact of aerosol aging on the microphysical and optical properties of the biomass burning aerosol during transport, and discuss the impact on the atmospheric radiation budget. Furthermore, we show an intercomparison of the DLR and NOAA SP2 measurements for a biomass burning sequence during the flight on June 11, 2012.