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Atmospheric aerosols affect the global energy budget by scattering and absorbing sunlight (direct effects) and by changing the microphysical structure, lifetime, and coverage of clouds (indirect effects). Both aerosol direct and indirect effects are affected by the vertical distribution of aerosols in the atmosphere, which is further influenced by a range of processes, such as aerosol dynamics, long-range transport, and entrainment. However, many observations of these processes are based on ground measurements, limiting our ability to understand the vertical distribution of aerosols and simulate their impact on clouds and climate. In this work, we examined the vertical heterogeneity of aerosols over the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) using data collected from the Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystems (HI-SCALE) campaign. The vertical profiles of meteorological and aerosol physiochemical properties up to 2500 m above the ground are examined based on the 38 flights conducted during the HI-SCALE campaign. The aerosol properties over the SGP show strong vertical heterogeneity and seasonal variabilities. The aerosol concentrations at the surface are the highest due to strong sources of emission at ground level. The mode diameter of these aerosols during summer (~ 100 nm) is larger than that during spring (~ 30 nm), potentially as a result of enhanced condensational growth due to enriched volatile organic compounds in summer. The concentration of aerosols below 30 nm in the boundary layer (BL) (e.g., below 1000 m) during spring is higher than that during summer, a result of the stronger new particle formation (NPF) events and a reduced condensation sink in spring. In the BL, the size of the aerosols gradually increases with altitude due to condensational growth and cloud processing. However, the composition of the aerosols remained similar, with organics and sulfates representing 59.8 ± 2.2 % and 22.7 ± 2.1 % of the total mass in the BL. Through the vertical profiles of aerosol properties, we noticed a considerable number of NPF events (7 out of 38) in the upper BL, where the newly formed particles continue to grow as they are mixed down to the surface. There is also an indication that deep convection brings aerosols from the free troposphere (FT) to the surface, where they grow to contribute to the cloud condensation nuclei (CCN). Overall, the vertical heterogeneity of aerosols over the SGP is influenced by aerosol dynamics (new particle formation, growth, and cloud processing) and transport processes (long-range transport, entrainment, and convective downward transport). Case studies showing the influence of these factors are discussed.

During the first phase of the Biomass Burn Operational Project (BBOP) field campaign, conducted in the Pacific Northwest, the DOE G-1 aircraft was used to follow the time evolution of wildfire smoke from near the point of emission to locations 2–3.5 hours downwind. In nine flights we made repeated transects of wildfire plumes at varying downwind distances and could thereby follow the plume's time evolution. On average there was little change in dilution-normalized aerosol mass concentration as a function of downwind distance. This consistency hides a dynamic system in which primary aerosol particles are evaporating and secondary ones condensing. Organic aerosol is oxidized as a result. On all transect more than 90 % of aerosol is organic. In freshly emitted smoke aerosol, NH4+ is approximately equivalent to NO3−. After two hours of daytime aging, NH4+ increased and is approximately equivalent to the sum of Cl−, SO42− and NO3−. Particle size increased with downwind distance causing particles to be more efficient scatters. Averaged over nine flights, mass scattering efficiency increased in ~ two hours by 56 % and in one fight doubled. Coagulation and material transport from small to large particles are discussed as mechanisms for increasing particle size. As absorption remained nearly constant with age the time evolution of single scatter albedo was controlled by age-dependent scattering. Near-fire aerosol had a single scatter albedo (SSA) of 0.8–0.9. After one to two hours of aging SSAs were typically 0.9 and greater. Assuming global-average surface and atmospheric conditions, the observed age-dependence in SSA would change the direct radiative effect of a wildfire plume from near zero near the fire to a cooling effect downwind.

The effect of organic particle mass loading from 1 to ≥100 μg m−3 on the cloud condensation nuclei (CCN) properties of mixed organic-sulfate particles was investigated in the Harvard Environmental Chamber. Mixed particles were produced by the condensation of organic molecules onto ammonium sulfate particles during the dark ozonolysis of α-pinene. A continuous-flow mode of the chamber provided stable conditions over long time periods, allowing for signal integration and hence increased measurement precision at low organic mass loadings representative of atmospheric conditions. CCN activity was measured at eight mass loadings for 80- and 100-nm particles grown on 50-nm sulfate seeds. A two-component (organic/sulfate) Köhler model, which included the particle heterogeneity arising from DMA size selection and from organic volume fraction for the selected 80- and 100-nm particles, was used to predict CCN activity. For organic mass loadings of 2.9 μg m−3 and greater, the observed activation curves were well predicted using a single set of physicochemical parameters for the organic component. For mass loadings of 1.74 μg m−3 and less, the observed CCN activity increased beyond predicted values using the same parameters, implying changed physicochemical properties of the organic component. A sensitivity analysis suggests that a drop in surface tension must be invoked to explain quantitatively the CCN observations at low SOA particle mass loadings. Other factors, such as decreased molecular weight, increased density, or increased van't Hoff factor, can contribute to the explanation but are quantitatively insufficient as the full explanation.

The authors of this volume analyze the policies that led to East Asia's economic success, including those affecting human resources, savings, the financial sector, trade and institutions, and examine the lessons these policies carry for Latin America. The genesis of this book was an IDB-sponsored conference, "Development Experience of the Latin American and East Asian Countries" held in Santiago, Chile in June 1994. The conference was attended by policymakers, scholars and community leaders from Latin America, North America and East Asia. The Japan Special Fund and the Economic Commission for Latin America and the Caribbean provided financial and logistical support. The papers presented in this volume draw on the conference discussions. Valuable contributions and comments came from many participants, including government officials from Latin American and Caribbean countries and staff of the World Bank, ECLAC, and IDB.

The authors of this volume analyze the policies that led to East Asia's economic success, including those affecting human resources, savings, the financial sector, trade and institutions, and examine the lessons these policies carry for Latin America. The genesis of this book was an IDB-sponsored conference, "Development Experience of the Latin American and East Asian Countries" held in Santiago, Chile in June 1994. The conference was attended by policymakers, scholars and community leaders from Latin America, North America and East Asia. The Japan Special Fund and the Economic Commission for Latin America and the Caribbean provided financial and logistical support. The papers presented in this volume draw on the conference discussions. Valuable contributions and comments came from many participants, including government officials from Latin American and Caribbean countries and staff of the World Bank, ECLAC, and IDB.