- [abstract to follow]



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- [abstract to follow]



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- Atmospheric modeling, one of the first high performance computing (HPC) applications, remains a cycle-hungry domain today as we move to petascale computing. Designed from the outset for HPC, the Weather Research and Forecast (WRF) - widely used for operational weather forecasting, hurricane prediction, regional climate simulation, atmospheric chemistry, and basic atmospheric research -- is now exploiting systems comprising tens of thousands of cores as well as non-traditional architectures such as Graphics Processing Units. This talk presents a look forward at HPC and numerical weather prediction as a scientific computing challenge.



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- Atmospheric aerosol particles host a very complex mixture of organic and inorganic components. A significant fraction of organics present in aerosol particles are surface active, such as linear alkanoic and alkenoic acids or aromatics with hydrophilic substituents. Using reasonably well defined proxy systems, we have started to look at three different aspects of organic coatings: first, they may establish a barrier towards the transfer of trace gases from the gas phase into the aerosol phase. We have used the fast uptake of nitric acid to deliquesced NaCl particles to probe the effect of long chain C9 to C18 saturated and unsaturated fatty acids, indicating that the monolayer forming properties of these fatty acids determines the degree of reduction of phase transfer of nitric acid to the aqueous particles. Second, the chemical environment in a coating is substantially different from that in either the pure organic or the aqueous bulk phases. This is demonstrated with ozonolysis studies of oleic acid monolayers on deliquesced NaCl particles, which shows substantial formation of H2O2, exceeding that from bulk oleic acid ozonolysis or that known from alkene oxidation in the gas phase. Third, a number of species in organic coatings are absorbing light in the visible and UVA wavelength range. We have specifically investigated photosensitized redox processes that lead, among other things, to light induced reaction of organics with nitrogen dioxide and ozone, the former becoming a substantial source of nitrous acid in the lowermost troposphere.



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- Estimates of how humans are affecting the energy balance of the planet are uncertain largely due to complicated interactions between aerosols and clouds. A major factor in this uncertainty is the how humans have changed the number of particles in the atmosphere that may act as cloud condensation nuclei (CCN). Ultrafine particles (particles with diameters smaller than 100 nm), are often too small to act as CCN; however, a large fraction of particles in the atmosphere begin as ultrafine particles and must grow to CCN sizes. In this talk we will explore how uncertainties in ultrafine aerosol sources, such as nucleation and emissions from primary sources, lead to uncertainties in predictions of CCN concentrations. The impact of these ultrafine particles on CCN will be explored using both a simple model of aerosol timescales as well as a detailed 3-D general circulation model with aerosol microphysics. Finally, we will investigate the relative contribution of primary aerosol emissions and aerosol nucleation to CCN globally.



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- Atmospheric aerosols play a fundamental role in Earth’s atmospheric chemistry and climate. Soot is an absorbing aerosol, though the magnitude of that absorption has largely been determined by measuring the optical properties of uncoated soot. It has been proposed that coated soot might absorb radiation more efficiently than uncoated soot, thus warming the climate more than previously suspected. For this study, soot is generated in a well-controlled Santoro-Style diffusion flame burner with ethylene as the fuel, and has been successfully coated with dibutyl phthalate (DBP), a non-absorbing material. DBP has a refractive index of 1.490 (real part), which is similar to the refractive index of sulfuric acid (n=1.426) at 589 nm. DBP is substituted for the commonly found sulfate coated particles for several reasons including safety and instrument integrity. By changing the temperature of the DBP, the vapor pressure of the DBP is changed and consequently, the coating thickness can be changed. Extensive work has taken place in controlling the coating process as well as in the generation and delivery of the aerosols for analysis. The aerosols are classified with a differential mobility analyzer (DMA). From the DMA the aerosols are sent to a condensation particle counter (CPC) for size distributions or are analyzed. This talk will discuss some of the background work involved in this study as well as some of the techniques used in this experiment. 



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- Doppler cloud radar spectra provide a measure of the reflectivity- weighted velocity distributions of scatterers within a sampling volume, and as such, are snapshots of the interplay between atmospheric dynamics and hydrometeor microphysics. Distortions in spectrum morphologies from a commonly assumed gaussian distribution contain valuable information about atmospheric state that is not captured by the traditional three- moment spectrum model comprised of reflectivity, spectral width, and mean Doppler velocity. This talk will discuss three applications that analyze Doppler radar spectra in greater detail to extract useful information: classification of hydrometeor phase (ice, liquid, mixed), prediction of high spectral resolution lidar measurements, and the detection of insect-generated clutter. Potential future directions of this generalizable methodology will also be discussed.



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- The interaction of turbulence and aerosol particles in and surrounding clouds is important in understanding the microphysical properties of clouds. The seminar will detail the measurement of atmospheric turbulence with the gustprobe on the DOE G-1 Research Aircraft. This includes the techniques and associated difficulties of calculating atmospheric turbulent energy dissipation rates, updraft/downdraft velocities, and turbulent microphysical Reynolds numbers from the gustprobe data. Examples will be shown from the MASE 2005 study over the Pacific and the CHAPS 2007 study in Oklahoma. The MASE example will include the ubiquitous aerosol layer which is observed directly above marine stratus clouds. This 25 meter thick layer will be shown to be turbulently coupled to the marine stratus cloudtop, with turbulent exchange of aerosol particles between the layer and the cloudtop. Microphysical and chemical data will be shown which indicates that this layer is a region of aerosol production, as evidenced by enhanced aerosol particle, ozone and sulfur dioxide concentrations.



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