Black carbon (BC) aerosol mass mixing ratio and microphysical properties were measured from the NOAA P‐3 aircraft during active surface oil burning subsequent to the Deepwater Horizon oil rig ...explosion in April 2010. Approximately 4% of the combusted material was released into the atmosphere as BC. The total amount of BC introduced to the atmosphere of the Gulf of Mexico via surface burning of oil during the 9‐week spill is estimated to be (1.35 ± 0.72) × 106 kg. The median mass diameter of BC particles observed in the burning plume was much larger than that of the non‐plume Gulf background air and previously sampled from a variety of sources. The plume BC particles were internally mixed with very little non‐refractory material, a feature typical of fresh emissions from fairly efficient fossil‐fuel burning sources and atypical of BC in biomass burning plumes. BC dominated the total accumulation‐mode aerosol in both mass and number. The BC mass‐specific extinction cross‐section was 10.2 ± 4.1 and 7.1 ± 2.8 m2/g at 405 and 532 nm respectively. These results help constrain the properties of BC emissions associated with DWH and other large spills.
Key Points
BC yield from surface oil burning
BC size and coating state from surface oil burning
Lifetime and radiative impacts of BC from surface oil burning
While most black carbon (BC)‐containing particles are removed in the lower troposphere in the tropics, some are lofted to higher altitudes via convection where they may be distributed globally ...throughout the tropical tropopause layer (TTL). Single‐particle measurements of BC aerosol were made from the NASA WB‐57F aircraft during both the dry (February 2006) and wet (August 2007) seasons in Central America. BC mass loadings declined sharply with increasing altitude from the ground to 5 km. In the TTL, they were up to six times higher in the wet relative to the dry season. The variability in BC mass was examined using convective‐influence back trajectories to determine the source regions. The seasonal differences in the vertical profiles are explained by long‐range transport of (1) low‐BC air from the southern hemisphere in the dry season and (2) high‐BC air from biomass‐burning or pollution sources in Africa and Asia advected by the Asian monsoon circulation in the wet season.
Key Points
Tropical BC profiles from the ground to the lower stratosphere for two seasons
BC as a sensitive tracer of transport
Seasonal variability of BC attributed to influence from the Asian monsoon
In February and March of 2011, the Global Hawk unmanned aircraft system (UAS) was deployed over the Pacific Ocean and the Arctic during the Winter Storms and Pacific Atmospheric Rivers (WISPAR) field ...campaign. The WISPAR science missions were designed to (1) mprove our understanding of Pacific weather systems and the polar atmosphere; (2) evaluate operational use of unmanned aircraft for investigating these atmospheric events; and (3) demonstrate operational and research applications of a UAS dropsonde system at high latitudes. Dropsondes deployed from the Global Hawk successfully obtained high-resolution profiles of temperature, pressure, humidity, and wind information between the stratosphere and surface. The 35 m wingspan Global Hawk, which can soar for ~ 31 h at altitudes up to ~ 20 km, was remotely operated from NASA's Dryden Flight Research Center at Edwards Air Force Base (AFB) in California. During the 25 h polar flight on 9–10 March 2011, the Global Hawk released 35 sondes between the North Slope of Alaska and 85° N latitude, marking the first UAS Arctic dropsonde mission of its kind. The polar flight transected an unusually cold polar vortex, notable for an associated record-level Arctic ozone loss, and documented polar boundary layer variations over a sizable ocean–ice lead feature. Comparison of dropsonde observations with atmospheric reanalyses reveal that, for this day, large-scale structures such as the polar vortex and air masses are captured by the reanalyses, while smaller-scale features, including low-level jets and inversion depths, are mischaracterized. The successful Arctic dropsonde deployment demonstrates the capability of the Global Hawk to conduct operations in harsh, remote regions. The limited comparison with other measurements and reanalyses highlights the potential value of Arctic atmospheric dropsonde observations where routine in situ measurements are practically nonexistent.
In situ airborne measurements of actinic flux and the mass and mixing state of individual refractory black carbon (BC) particles were made in the lower troposphere around a major U.S. metropolitan ...area. These data were used to estimate atmospheric heating rates and surface dimming due to absorption of solar radiation by refractory BC. Direct absorption by ozone is also calculated and averages 10% of that of BC below 4 km but becomes dominant above this altitude. Variability in BC absorption is large due to source variability and clouds. Average BC heating rates are much smaller than those associated with BC and other absorbing aerosol components in global hotspot regions. These results, which are specific to refractory BC absorption, will help determine the value of short‐term climate‐change mitigation strategies involving BC emission reductions. They may also be used to estimate refractory BC contributions to total aerosol absorption.
Influenza A viruses occur worldwide in wild birds and are occasionally associated with outbreaks in commercial chickens and turkeys. However, avian influenza viruses have not been isolated from wild ...birds or poultry in South America. A recent outbreak in chickens of H7N3 low pathogenic avian influenza (LPAI) occurred in Chile. One month later, after a sudden increase in deaths, H7N3 highly pathogenic avian influenza (HPAI) virus was isolated. Sequence analysis of all eight genes of the LPAI virus and the HPAI viruses showed minor differences between the viruses except at the hemagglutinin (HA) cleavage site. The LPAI virus had a cleavage site similar to other low pathogenic H7 viruses, but the HPAI isolates had a 30-nucleotide insert. The insertion likely occurred by recombination between the HA and nucleoprotein genes of the LPAI virus, resulting in a virulence shift. Sequence comparison of all eight gene segments showed the Chilean viruses were also distinct from all other avian influenza viruses and represent a distinct South American clade.
Building on previously published details of the laboratory calibrations of the Harvard Lyman-a photofragment fluorescence hygrometer (HWV) on the NASA ER-2 and WB-57 aircraft, we describe here the ...validation process for HWV, which includes laboratory calibrations and intercomparisons with other Harvard water vapor instruments at water vapor mixing ratios from 0 to 10 ppmv, followed by in-flight intercomparisons with the same Harvard hygrometers. The observed agreement exhibited in the laboratory and during intercomparisons helps corroborate the accuracy of HWV. In light of the validated accuracy of HWV, we present and evaluate a series of intercomparisons with satellite and balloon borne water vapor instruments made from the upper troposphere to the lower stratosphere in the tropics and midlatitudes. Whether on the NASA ER-2 or WB-57 aircraft, HWV has consistently measured about 1-1.5 ppmv higher than the balloon-borne NOAA/ESRL/GMD frost point hygrometer (CMDL), the NOAA Cryogenic Frost point Hygrometer (CFH), and the Microwave Limb Sounder (MLS) on the Aura satellite in regions of the atmosphere where water vapor is <10 ppmv. Comparisons in the tropics with the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite show large variable differences near the tropopause that converge to ~10% above 460 K, with HWV higher. Results we show from the Aqua Validation and Intercomparison Experiment (AquaVIT) at the AIDA chamber in Karlsruhe do not reflect the observed in-flight differences. We illustrate that the interpretation of the results of comparisons between modeled and measured representations of the seasonal cycle of water entering the lower tropical stratosphere is dictated by which data set is used.
Building on previously published details of the laboratory calibrations of the Harvard Lyman‐α photofragment fluorescence hygrometer (HWV) on the NASA ER‐2 and WB‐57 aircraft, we describe here the ...validation process for HWV, which includes laboratory calibrations and intercomparisons with other Harvard water vapor instruments at water vapor mixing ratios from 0 to 10 ppmv, followed by in‐flight intercomparisons with the same Harvard hygrometers. The observed agreement exhibited in the laboratory and during intercomparisons helps corroborate the accuracy of HWV. In light of the validated accuracy of HWV, we present and evaluate a series of intercomparisons with satellite and balloon borne water vapor instruments made from the upper troposphere to the lower stratosphere in the tropics and midlatitudes. Whether on the NASA ER‐2 or WB‐57 aircraft, HWV has consistently measured about 1–1.5 ppmv higher than the balloon‐borne NOAA/ESRL/GMD frost point hygrometer (CMDL), the NOAA Cryogenic Frost point Hygrometer (CFH), and the Microwave Limb Sounder (MLS) on the Aura satellite in regions of the atmosphere where water vapor is <10 ppmv. Comparisons in the tropics with the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite show large variable differences near the tropopause that converge to ∼10% above 460 K, with HWV higher. Results we show from the Aqua Validation and Intercomparison Experiment (AquaVIT) at the AIDA chamber in Karlsruhe do not reflect the observed in‐flight differences. We illustrate that the interpretation of the results of comparisons between modeled and measured representations of the seasonal cycle of water entering the lower tropical stratosphere is dictated by which data set is used.
Black carbon (BC) and mineral dust are among the most abundant insoluble aerosol components in the atmosphere. When released, most BC and dust particles are externally mixed with other aerosol ...species. Through coagulation with particles containing soluble material and condensation of gases, the externally mixed particles may obtain a liquid coating and be transferred into an internal mixture. The mixing state of BC and dust aerosol particles influences their radiative and hygroscopic properties, as well as their ability of forming ice crystals. We introduce the new aerosol microphysics submodel MADE-in, implemented within the ECHAM/MESSy Atmospheric Chemistry global model (EMAC). MADE-in is able to track mass and number concentrations of BC and dust particles in their different mixing states, as well as particles free of BC and dust. MADE-in describes these three classes of particles through a superposition of seven log-normally distributed modes, and predicts the evolution of their size distribution and chemical composition. Six out of the seven modes are mutually interacting, allowing for the transfer of mass and number among them. Separate modes for the different mixing states of BC and dust particles in EMAC/MADE-in allow for explicit simulations of the relevant aging processes, i.e. condensation, coagulation and cloud processing. EMAC/MADE-in has been evaluated with surface and airborne measurements and mostly performs well both in the planetary boundary layer and in the upper troposphere and lowermost stratosphere.
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