Top PDF Ammonia in the summertime Arctic marine boundary layer: sources, sinks, and implications

Ammonia in the summertime Arctic marine boundary layer: sources, sinks, and  implications

Ammonia in the summertime Arctic marine boundary layer: sources, sinks, and implications

Acknowledgements. The authors are grateful for the hard work and dedication of the CCGS Amundsen crew. The authors also thank E. Mungall, A. Lee, V. Irish, H. Stark and J. J. B. Wentzell for help during mobilization, demobilization and calibration of the AIM-IC, as well as T. Papakyriakou and T. Burgers for providing meteorological data. The GEOS5-FP data used in this study/project have been provided by the Global Modeling and Assimilation Office (GMAO) at NASA Goddard Space Flight Center. The hi- volume sampler used for the Alert measurements was maintained and calibrated by D. Veber, as well as numerous other technicians and operators over the years. Acknowledgement is also extended to the crew at CFS Alert for maintaining the base year round. The fieldwork and model analysis was supported by NSERC’s Climate Change and Atmospheric Research program, ArcticNet and NSERC. The QFED2 code and emissions data were provided by K. Travis and P. Kim. The NASA FIRMS data set was provided by LANCE FIRMS operated by NASA/GSFC/ESDIS with funding provided by NASA/HQ. G. R. Wentworth acknowledges funding from the NSERC program Integrating Atmospheric Chemistry from Earth to Space (IACPES). Lastly, the authors wish to thank B. Christensen for providing logistical support throughout the project.
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In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O<sub>3</sub>, IO, OIO and NO<sub>x</sub>

In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O<sub>3</sub>, IO, OIO and NO<sub>x</sub>

observed (Read et al., 2008). However, reduction in the tropospheric ozone burden through iodine emitted from coastal marine sources has not been verified by observa- tions so far. During the 5-week field observations at Mweenish Bay the mixing ratios of ozone decreased in several days from the normal levels of ∼40 ppt down to as low as 12 ppt. Since the measurements by denuders did not cover all these ozone destruc-

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Interannual variability of ammonia concentrations over the United States:
sources and implications

Interannual variability of ammonia concentrations over the United States: sources and implications

pogenic ammonia are affected by changes in agricultural ac- tivities such as livestock population and fertilizer applica- tion, as well as the implementation of catalytic converters in urban areas. These emissions are sensitive to meteorology that modulates volatilization from the agricultural ammonia sources, increasing with higher temperature and wind speed. Biomass burning events are highly variable and temporar- ily increase ammonia emissions. Our baseline simulation captures only the year-to-year variation in biomass burning emissions of ammonia; emissions from all other sectors are fixed. Meteorology affects the partitioning of ammonia into ammonium nitrate, where higher temperature and lower rel- ative humidity favor the gas phase, as well as the removal of ammonia from the atmosphere by changing the rates of both wet and dry deposition (Russell et al., 1983; Mozurkewich, 1993). Even in a well-mixed boundary layer, ammonia con- centrations may have strong gradients caused by temper- ature variations with altitude that alter gas-to-particle par- titioning of ammonium (Neuman et al., 2003). Figure 5 shows the year-to-year variation in key meteorological pa- rameters across the US from 2008 to 2012 from the GEOS- 5 assimilated meteorological product. Emissions of SO x and
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Marine boundary layer cloud regimes and POC formation in an LES coupled to a bulk aerosol scheme

Marine boundary layer cloud regimes and POC formation in an LES coupled to a bulk aerosol scheme

Table 1. List of runs performed in this study. Run names concatenate the large-scale subsi- dence forcing W at 1500 m given in mm s −1 , followed by initial PBL aerosol concentration NA in # mg −1 , followed by any other modifiers for sensitivity studies. All runs use identical thermody- namic initialization, a FT aerosol concentration of 100 mg −1 and a 24 km horizontal domain size, except where noted. POC runs are 192 km wide and are initialized with equally-sized regions of higher and lower aerosol concentration given by the two numbers after NA.
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Retrieval of tropospheric NO<sub>2</sub> using the MAX-DOAS method combined with relative intensity measurements for aerosol correction

Retrieval of tropospheric NO<sub>2</sub> using the MAX-DOAS method combined with relative intensity measurements for aerosol correction

The Multi-Axis Differential Optical Absorption Spec- troscopy (MAX-DOAS) method (e.g. Wagner et al., 2004; H¨onninger et al., 2004; Wittrock et al., 2004; Sinreich et al., 2005; Friess et al., 2006; Leigh et al., 2007; Irie et al., 2008a) offers an alternative in this respect, since it has a much larger spatial representativeness than in situ surface moni- tors. MAX-DOAS instruments observe scattered solar ra- diation from the surface – in the UV and/or Visible – at a spectral resolution of typically 0.5 nm in multiple viewing di- rections (see Fig. 1). Small elevations have a relatively high sensitivity to the lower troposphere, since detected photons at small elevations have longer paths through these layers than photons observed at larger elevations. Radiative trans- fer simulations at 428 nm show that the horizontal represen- tative range is about 5 to 10 km, whereas the vertical range is about 1 to 4 km. Both ranges are wavelength dependent. The horizontal and vertical range also have a strong depen- dence on elevation, see e.g. Wittrock et al. (2004) and Pikel- naya et al. (2007). The increased sensitivity to the lower troposphere also distinguishes the MAX-DOAS technique from other ground-based passive DOAS techniques, such as direct-sun DOAS (total column NO 2 , see e.g. Herman et al.,
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Nongyrotropic particle distributions in space plasmas

Nongyrotropic particle distributions in space plasmas

Nongyrotropic plasmas are not in thermal equilibri- um. They carry excess energy and may excite unstable waves. Studies of the stability of rotating nongyrotropic distribution functions and of nongyrotropies maintained by sources and sinks in the phase space were performed by Brinca et al. (1992, 1993), Motschmann and Glass- meier (1993, 1998a) and Cao et al. (1995, 1998). The stability of an inhomogeneous nongyrotropy was dis- cussed for a magnetic reversal by Motschmann and Glassmeier (1998b). In broad ranges of the parameters nongyrotropy contributes to the destabilization of a plasma and to the excitation of unstable wave modes. In many observations the nongyrotropy is superimposed by other sources of free energy such as ring distribu- tions, anisotropy distributions or beams. In these observations it is not always easy to separate the contribution of these di€erent sources. In theoretical studies, however, it is very easy to perform this separation. Pure nongyrotropies without any other source of excess energy were studied by Brinca and Romeiras (1998) and Motschmann and Glassmeier (1998a). In an open phase space and for propagation parallel to the ambient magnetic ®eld they found a destabilization of the right handed mode. For propaga- tion perpendicular to the ambient magnetic ®eld non- gyrotropy may excite the extraordinary mode. In a rotating nongyrotropy the temporal modulation of any undisturbed distribution may couple wave modes at frequencies which di€er from each other by the gyro- frequency of the nongyrotropic plasma component or its
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Atmospheric peroxyacetyl nitrate (PAN): a global budget and source attribution

Atmospheric peroxyacetyl nitrate (PAN): a global budget and source attribution

bison, M. J., Vay, S. A., Weinheimer, A. J., Knapp, D. J., Montzka, D. D., Flocke, F. M., Pol- lack, I. B., Wennberg, P. O., Kurten, A., Crounse, J., Clair, J. M. St., Wisthaler, A., Mikoviny, T., Yantosca, R. M., Carouge, C. C., and Le Sager, P.: Nitrogen oxides and PAN in plumes from boreal fires during ARCTAS-B and their impact on ozone: an integrated analysis of aircraft and satellite observations, Atmos. Chem. Phys., 10, 9739–9760, doi:10.5194/acp-10-9739-

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Braz. J. Chem. Eng.  vol.30 número4

Braz. J. Chem. Eng. vol.30 número4

The analysis of non-Newtonian fluids is signifi- cant because of several industrial and engineering applications. Such fluids are encountered in the process of manufacturing coated sheets, foods, drilling muds, cosmetic products, dilute polymer solutions, poly- meric melts etc. Different models of such fluids have beenare suggested. This is due to the versatility of fluid characteristics in nature (Qi and Xu, 2007; Kothandapani and Srinivas, 2008; Nadeem and Akbar, 2010; Jamil and Fetecau, 2010a,b; Wang and Tan, 2011; Hayat et al., 2011a,b; Jamil et al., 2011; Nadeem et al., 2011; Hayat et al., 2012). Although much information is available on the boundary layer flow of viscous fluids, such attempts for non- Newtonian fluids are limited. In fact, the resulting differential equations in non-Newtonian fluids are more nonlinear than for a viscous fluid. To find the analytic/numerical solution of such equations is not an easy task.
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BIOCHEMICAL RESPONSES OF TWO ERYTHRINIDAE FISH TO ENVIRONMENTAL AMMONIA

BIOCHEMICAL RESPONSES OF TWO ERYTHRINIDAE FISH TO ENVIRONMENTAL AMMONIA

Toxicity through increase of external ammonia comes with corresponding plasma level enhancement. Among the ammonia detoxification strategies, glutamine formation from glutamate and the urea synthesis from glutamine and aspartate (Mommsen, & Walsh, 1989, 1992; Walsh, 1997; McKenzie et al., 1999) are relevant. Glutamine synthesis occurs independently of urea formation. However, fish urea synthesis is dependent on glutamine as substrate. Regulation of these biochemical processes is done in many ways, such as gene control, enzyme compartmentalization, metabolite concentration, and kinetic characteristics of enzymes. In this study of OUC enzymes, characteristics correlated to environmental pressures provide a path to understanding relevant aspects of regulatory mechanisms in biochemical pro- cesses.
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Variations in global methane sources and sinks during 1910–2010

Variations in global methane sources and sinks during 1910–2010

are shown in magenta (blue) and purple (green), respectively. Red (black) symbol and text are for Arctic (Antarctic) region. Annual average ice core data (Law Dome: DSS, DE08 and DE08- 2), firn records (Law Dome (DE08-2 and DSSW20K); NGRIP firn data; and NEEM firn data) and direct observations (CGO: air archive, flask sampling and GAGE/AGAGE; SUM: flask sam- pling) are prepared and presented separately here. All the observation data are referenced to the Tohoku University (TU) CH 4 scale (Aoki et al., 1992; Umezawa et a., 2014).
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Closing the Dimethyl Sulfide Budget in the Tropical Marine Boundary Layer during the Pacific Atmospheric Sulfur Experiment

Closing the Dimethyl Sulfide Budget in the Tropical Marine Boundary Layer during the Pacific Atmospheric Sulfur Experiment

Table 2. DMS budget terms for the flights that they could be measured. Columns are defined from left to right as follows: Observed rate of change, vertical flux divergence, horizontal ad- vection, photo-chemical loss required to balance budget L in Eq. (2), all in units of ppt hr −1 . Net error is an estimate of the error in the photochemical term (ppt hr −1 ). The remaining columns are entrainment velocity (cm s −1 ), mean MBL DMS concentration (ppt), surface flux and flux into the overlying buffer layer (umol m −2 d −1 ).
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Fast sulfur dioxide measurements correlated with cloud concentration nuclei spectra in the marine boundary layer

Fast sulfur dioxide measurements correlated with cloud concentration nuclei spectra in the marine boundary layer

Cotton, W. R., Di Girolamo, L. D., Geerts, B., Gerber, H., Goke, S., Gomes, L., Heikes, B. G., Hudson, J. G., Kollias, P., Lawson, 5 R. P., Krueger, S. K., Lenschow, D. H., Nuijens, L., OSullivan, D. W., Rilling, R. A., Rogers, D. C., Siebesma, A. P., Snodgrass, E., Stith, J. L., Thornton, D. C., Tucker, S., Twohy, C. H., and Zuidema, P: Electronic supplement to Rain in (shallow) Cumulus over the Ocean–The RICO campaign, Bull. Am. Meteorol. Soc., 88,

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MATHEMATICAL AND NUMERICAL METHODS FOR INVERSE PROBLEMS USING FUNDAMENTAL SOLUTIONS TECHNIQUES

MATHEMATICAL AND NUMERICAL METHODS FOR INVERSE PROBLEMS USING FUNDAMENTAL SOLUTIONS TECHNIQUES

(exterior) and γ (interior). Assuming a homogeneous Dirichlet or Neumann boundary condition on γ, we show that from a single pair of Cauchy data on an accessible part of the boundary Σ ⊂ Γ we can identify both the boundary condition and the boundary γ. A criterion is presented to distinguish such situations. We study two numerical methods to retrieve γ in the two dimensional case, when considering a homogeneous Dirichlet con- dition on γ. The first is a decomposition method requiring at a first step the resolution of a Cauchy problem. The second is a Quasi–Newton method that requires the resolution of several direct problems. For both situations, we propose the method of fundamental solutions as numerical approximation for the Cauchy and direct problems. Several numer- ical examples are presented and the accuracy and robustness of the methods is discussed. Considering a homogeneous Robin condition on γ, we address the inverse problem that consists in the identification of the Robin coefficient on γ (the boundary is now assumed to be known) from a single pair of Cauchy data on Γ. An adaptation of the decomposition and Quasi–Newton methods is studied and implemented. Several numerical simulations are presented to illustrate and compare the performance of both methods.
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Multiphase modeling of nitrate photochemistry in the quasi-liquid layer (QLL): implications for NOx release from the Arctic and coastal Antarctic snowpack

Multiphase modeling of nitrate photochemistry in the quasi-liquid layer (QLL): implications for NOx release from the Arctic and coastal Antarctic snowpack

Jones et al., 2000; Beine et al., 2002; Dibb et al., 2002; Simp- son et al., 2007). It also accounts for the range of γ mea- sured during Arctic and Antarctic summer and springtime, where springtime maximum γ ranges from ∼0.84 to ∼1.86 and summertime maximum γ ranges from ∼0.50 to ∼2.20, which is also in good accord with measured γ over the snow- pack (Honrath et al., 1999, 2002; Jones et al., 2000; Beine et al., 2002; Dibb et al., 2002; Simpson et al., 2007). Fur- thermore, these model results reinforce laboratory and snow chamber results showing that the major source of NO release from snow/ice surfaces isNO − 2 , its immediate photolytic pre- cursor that absorbs at wavelengths longer than nitrate itself (Cotter et al., 2003; Boxe et al., 2006), as shown in Fig. 2. Thus, incorporating the actinic flux at the Earth’s surface shows that nitrite is more photolabile than nitrate (Cotter et al., 2003).
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Characterization of a boreal convective boundary layer and its impact on atmospheric chemistry during HUMPPA-COPEC-2010

Characterization of a boreal convective boundary layer and its impact on atmospheric chemistry during HUMPPA-COPEC-2010

analysis of the data using the MXL model. The day is of interest for the interpretation of chemical observations, since most instruments were functioning and the wind came from the south-west, which was its predominant direction (Table 2 of Williams et al., 2011). Therefore, chemical data is available for this day under conditions that are typ- ical for the campaign. Closely related to our research questions, additional dynamical

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Boundary layer development and summer circulation in Southern Portugal

Boundary layer development and summer circulation in Southern Portugal

On the Iberian Peninsula, the summer circulation generated by the land-sea thermal contrast is associated with the regional circulation of a thermal low in the central region, well away from the direct effect of the sea. The interaction between these effects at local and regional scales, tends to reinforce the special character of the Iberian circulation. The results from numerical simulations showed that the evolution of the BL in the interior of the Peninsula is strongly influenced by the horizontal transport of heat and moisture in the sea-breeze circulation, even in locations at more than 100 km from the coast, where a direct sea-breeze effect might be expected to be of reduced importance. This influence occurs in the form of a bulk cooling of the BL in mid to late afternoon, depending on the distance from the coast. The results also showed evidence of complex 3D transport of humidity in the Iberian region, linking the coastal source region with the mid troposphere where it interacts with the large-scale subsidence, associated with the anticyclonic circulation in the upper levels. The climatolog- ical importance of this transport cannot be proven from the 2 weeks of radiosondes performed, but the corresponding vertical patterns of the humidity profile were frequently observed during this period.
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Radiative and climate impacts of a large volcanic eruption during stratospheric sulfur geoengineering

Radiative and climate impacts of a large volcanic eruption during stratospheric sulfur geoengineering

The MAECHAM5-HAM-SALSA simulations were carried out with a free running setup without nudging. Thus the dynamical feedback resulting from the additional heat- ing from increased stratospheric sulfate load was taken into account. On the other hand, not running the model in the nudged mode means that the online emissions of, e.g., sea salt and mineral dust that are sensitive to wind speed at 10 m height, can dif-

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Black carbon measurements in the boundary layer over western and northern Europe

Black carbon measurements in the boundary layer over western and northern Europe

The SP2 incandescence response for each detector was calibrated by the manufacturer (DMT) by passing dried, dif- ferential mobility analyser-selected (DMA; TSI 3085, St. Paul, Minnesota, USA) monodisperse Aquadag carbon par- ticles to the instrument (Aecheson Colloids Company, Port Huron, Michigan). The measured incandescence response was related to rBC mass calculated from the mobility diam- eter and an estimate of the effective density of the calibra- tion particles. The manufacturer calibration obtained in this way relied on a constant density assumption for the Aquadag calibration material, however Moteki et al. (2010) showed that the effective density (the relationship between mobility- estimated volume and mass measured by an aerosol particle mass (APM) analyser (Ehara et al., 1996)) of Aquadag de- creased linearly with mobility diameter. The size dependence arose from the behaviour of the non-spherical Aquadag par- ticles in the DMA. We adjusted the calibration results to ac- count for the shift and provide the calibration data in the sup- plementary information. Moteki et al. (2010) also showed that different rBC calibration materials produced different incandescence signal peak value-to-rBC mass relationships, with Aquadag having a larger signal response for a given rBC mass compared to ambient soot measured in Tokyo, Japan with an APM-SP2 system. The magnitude of the difference in responses was about 40% for particles below 10 fg in mass (0.22 µm in diameter assuming a density of 1.8 g cm −3 ), but the differences for larger particles were smaller. We have not attempted to adjust our results to account for these dif- ferences because it was not clear if ambient soot in Tokyo had similar properties to the ambient soot measured in the campaign.
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Properties of cloud condensation nuclei (CCN) in the trade wind marine boundary layer of the western North Atlantic

Properties of cloud condensation nuclei (CCN) in the trade wind marine boundary layer of the western North Atlantic

Only a few studies of CCN properties have previously been carried out over the Caribbean Sea; based on the lim- ited and very different results reported, it is not evident what the dominant CCN properties are in that region. The ob- jective of the current study is to investigate to what extent organic species, nss inorganic species, sea salt and long- range transported Saharan mineral dust may influence the CCN properties in the MBL in that region. The CCN ac- tivity was inferred from CCN concentrations in conjunction with particle number size distribution measurements. Par- ticles in the dominant CCN size range were also investi- gated with transmission electron microscopy (TEM) com- bined with energy-dispersive X-ray spectroscopy (EDX), in order to identify refractory PM such as sea salt and mineral dust, and for estimation of the volume fractions of different types of PM. The present study was carried out on Barba- dos as part of the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) cam- paign during June–July 2013.
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A box model study on photochemical interactions between VOCs and reactive halogen species in the marine boundary layer

A box model study on photochemical interactions between VOCs and reactive halogen species in the marine boundary layer

ficult to detect in the ambient air by currently available measurement techniques (see Sect. 1 ). Where the oceanic emissions of alkenes are switched off (Run 2), BrO mixing ratio is calculated to be somewhat higher, ranging <1–3.4 pmol/mol during the day- time. Among the model runs conducted in the present work, Run 1b yield a result with the most activated bromine chemistry by neglecting the oceanic emission of CH 3 CHO

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