Andrew Turnipseed

The canopy horizontal array turbulence study

The Canopy Horizontal Array Turbulence Study (CHATS) took place in spring 2007 and is the third in the series of Horizontal Array Turbulence Study (HATS) experiments. The HATS experiments have been instrumental in testing and developing subfilterscale (SFS) models for large-eddy simulation (LES) of planetary boundary layer (PBL) turbulence. The CHATS campaign took place in a deciduous walnut orchard near Dixon, California, and was designed to examine the impacts of vegetation on SFS turbulence. Measurements were collected both prior to and following leafout to capture the impact of leaves on the turbulence, stratification, and scalar source/sink distribution. CHATS utilized crosswind arrays of fast-response instrumentation to investigate the impact of the canopy-imposed distribution of momentum extraction and scalar sources on SFS transport of momentum, energy, and three scalars. To directly test and link with PBL parameterizations of canopy-modified turbulent exchange, CHATS also included a 30-m profile ...

Marine Organic Halide and Isoprene Emissions Near Mace Head, Ireland

Vertical profiles of the concentration of several alkyl halides, as well as isoprene, were made from the surface to 200 m, using a tethered balloon platform, near Mace Head, Ireland in September-October 2003. Profiles indicate a surface source of several alkyl halides. Alkyl halides have been proposed as a source of new particles in the atmosphere. Estimates of emission rates (µ gm −2 h −1 ) were made using a flux-gradient technique for CH2Br2 (0.8),

Arctic springtime observations of volatile organic compounds during the OASIS‐2009 campaign

Gas-phase volatile organic compounds (VOCs) were measured at three vertical levels between 0.6 m and 5.4 m in the Arctic boundary layer in Barrow, Alaska, for the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS)-2009 field campaign during March–April 2009. C4-C8 nonmethane hydrocarbons (NMHCs) and oxygenated VOCs (OVOCs), including alcohols, aldehydes, and ketones, were quantified multiple times per hour, day and night, during the campaign using in situ fast gas chromatography-mass spectrometry. Three canister samples were also collected daily and subsequently analyzed for C2-C5 NMHCs. The NMHCs and aldehydes demonstrated an overall decrease in mixing ratios during the experiment, whereas acetone and 2-butanone showed increases. Calculations of time-integrated concentrations of Br atoms, ∫[Br]dt, yielded values as high as (1.34 ± 0.27) × 1014 cm−3 s during the longest observed ozone depletion event (ODE) of the campaign and were correlated with the steady state Br calculated at the site during this time. Both chlorine and bromine chemistry contributed to the large perturbations on the production and losses of VOCs. Notably, acetaldehyde, propanal, and butanal mixing ratios dropped below the detection limit of the instrument (3 parts per trillion by volume (pptv) for acetaldehyde and propanal, 2 pptv for butanal) during several ODEs due to Br chemistry. Chemical flux calculations of OVOC production and loss are consistent with localized high Cl-atom concentrations either regionally or within a very shallow surface layer, while the deeper Arctic boundary layer provides a continuous source of precursor alkanes to maintain the OVOC mixing ratios.

Boundary layer dynamics during the Ocean‐Atmosphere‐Sea‐Ice‐Snow (OASIS) 2009 experiment at Barrow, AK

Three-dimensional atmospheric turbulence measurements were conducted from seven sonic anemometers on two different towers in Barrow, AK, during the spring of 2009 as part of the Ocean-Atmosphere-Sea-Ice-Snow (OASIS) campaign. This was the largest number of side-by-side atmospheric turbulence measurements in the Arctic at one time. These analyses allowed for (1) a comparison of the instrumental measurement approaches and (2) a comparison of the variability of the lower atmospheric surface layer at these measurement heights and tower sites. Friction velocity estimates were affected for a sonic anemometer that was operated on the tower in the near vicinity of a building module. Boundary layer height (BLH) was estimated from sonic anemometer measurements based both on a turbulence variable estimator and a temperature gradient method. Results from both methods were compared to radiosonde-estimated BLH and generally underestimated the BLH for shallower depths. Conditions with low BLH (< 100 m) often lasted for several days. The seven ozone depletion events (ODE) that were observed during the OASIS campaign had a tendency of coinciding with BLH of less than 50 m and stable atmospheric conditions; however, there was not a clear relationship between the occurrence of ODE and wind speed or wind direction as ODE occurred under a wide range of conditions of BLH, wind speed, local wind direction, and atmospheric stability. Comparisons of these surface layer dynamics to sites in Antarctica and Greenland reveal that boundary layer dynamics are not the primary driving force that fosters the unique ozone chemistry at this coastal Arctic site.

Hygroscopic and Volatile Properties of Ultrafine Particles in the Eucalypt Forests: Comparison with Chamber Experiments and the Role of Sulphates in New Particle Formation

Simultaneous measurements of the volatile and hygroscopic properties of ultrafine particles were conducted in a Eucalypt forest in Tumbarumba, South-East Australia, in November 2006. These measurements were part of an intensive field campaign EUCAP 2006 (Eucalypt Forest Aerosols and Precursors). The particles exhibited a 2 step volatilisation with the first component starting to evaporate at temperatures above 50 degrees Celsius. With the onset of evaporation of the first component the hygroscopic growth factor increased. This indicated that the particle was composed of a less volatile, but more hygroscopic core, which was coated with a more volatile, but less hygroscopic, coating. The fraction of the more hygroscopic component was proportional to the measured maximum SO2 concentration indicating the role of gaseous H2SO4 in new particle formation. As the volatilisation temperature of the second more hygroscopic component was above that for H2SO4 it is likely that this component is partially or fully neutralised H2SO4. Comparison with pinene smog chamber experiments shows an excellent agreement with the first step volatilisation indicating its origin in the photooxidation of a monoterpene precursor.

Atmospheric aerosol and ion characteristics during EUCAP (Eucalypt Forest Aerosols and Precursors)

We measured the characteristics and dynamics of atmospheric ions, aerosol particles, and their precursors in an intensive field campaign in a Eucalypt forest in Tumbarumba, South-East Australia, in November 2006. The measured size range of ions was 0.34 to 40 nm and that of aerosol particles approximately 10 to 168 nm, and for observing their size distributions we used an Air Ion Spectrometer (AIS) and a Scanning Mobility Particle Sizer (SMPS). We also measured the hygroscopic and chemical properties of the particles with a Volatility-Humidity Tandem Differential Mobility Analyser (VH-TDMA). The total concentration of ultrafine aerosol particles was measured with a Condensational Particle Counter (CPC). Furthermore, we measured ambient concentrations of volatile organic compounds (VOC), SOx, NOx/NOy, and O3. Finally, we modelled the 96-h back trajectories of air masses arriving at the site and observed that the arrival directions varied greatly and included trajectories that travelled only over land as well as ones that travelled most of the time over the ocean. On the most polluted day, the air masses arrived approximately from the direction of greater Sydney / Newcastle coal mine area. The total concentration of ultrafine aerosol particles was approximately 3500 cm-3, and daytime aerosol formation took place on 64% of days with acceptable data. The dominant VOCs were isoprene, eucalyptol, a- and b-pinene, camphene, and limonene. The measured hygroscopic growth factors (Gh) at RH of 90% varied from 1.1 to 1.5. The smallest Gh were observed for aged accumulation mode particles in early mornings, and the largest Gh occurred for the freshly nucleated particles on Nov 10, the day with the highest concentration of SO2.