Search Results

One cannot overestimate the importance of oxygenated organic compounds in atmospheric chemistry. As discussed in the previous chapters of this book and elsewhere (e.g., Wayne, 1991; Seinfeld and Pandis, 1998; Brasseur et al., 1999; Finlayson-Pitts and Pitts, 2000; Calvert et al., 2000, 2002, 2008) the atmosphere is an oxidizing environment and all organic compounds emitted into the atmosphere are converted into oxygenated organic compounds. The first-generation products are oxidized further. As an example, the oxidation of ethane gives CH3CHO, C2H5OH, and C2H5OOH as first-generation products and CH3OH, CH3OOH, CH2O, and HC(O)OH as second-generation products. An understanding of the chemistry of oxygenated organic compounds is central to unraveling the complex processes in the atmosphere. In this chapter we discuss the representation of oxygenates in atmospheric models, their participation in secondary organic aerosol formation, contribution to HOx chemistry in the upper troposphere, role in the transport of pollutants, and use as proxies for volatile organic compound (VOC) emissions. A major application of the chemical kinetics and mechanisms of VOC oxidation is the development of an understanding of the chemistry occurring in the troposphere and the use of that understanding to predict and develop strategies which help to mitigate adverse changes in air quality and climate change. Such applications depend on the development of models that assess chemical impacts; chemical mechanisms lie at the heart of such models. The mechanisms can be very detailed, often termed explicit, in models where the aim is to understand the chemistry occurring in a small volume of air, for example, in an analysis of processes determining radical concentrations in field measurements. Such a mechanistic approach can also be used, with increased computer resources, when a trajectory approach is used to assess the coupled impacts of atmospheric transport and chemistry. An Eulerian approach to modeling both regional and global processes presents greater problems, because the chemical rate equations have to be solved for each species at each spatial grid point in the model; this severely limits the number of chemical species that can be incorporated realistically in the model.

This chapter discusses data assimilation in atmospheric chemistry and air quality. Atmospheric chemistry dynamics and its simulations are significantly forced by emissions, in addition to other parameters. Data assimilation typically aims at analysing the initial state of the system. Hence, for atmospheric chemistry simulations, data assimilation must be extended beyond initial-value identification to identify further parameters by estimation techniques. This chapter describes advanced spatio-temporal data assimilation techniques used in atmospheric chemistry. The objective is joint parameter-initial-state estimation for a coupled four-dimensional variational data assimilation/inversion system using the chemistry-transport model EURAD-IM and satisfying three criteria: both parameter families must have dominant influence on the dynamics, they must be poorly known, and they must impinge on the system on the same timescale. A coupled initial-value/emission-inversion system is described, along with assimilation of tropospheric satellite data from both gas-phase and aerosol retrievals. Examples of aerosol data assimilation are also given.

This book examines the fundamental physical processes that control planetary climates, from convection and radiation to escape of atmospheres, evaporation, condensation, atmospheric chemistry, and the dynamics of rotating fluids. It looks at the climates of the planets in order of distance from the Sun, starting with Venus and ending with planets around other stars. The greenhouse effect and climate evolution are discussed, along with basic physical processes such as convection, radiation, Hadley cells, and the accompanying winds. It also considers the “faint young Sun paradox,” illustrated by Mars, and the effect of planetary rotation on climate, the influence of sunlight and rotation on weather patterns, and Neptune's extraordinary strong winds.

This chapter discusses the extent and nature of anthropogenic perturbations of clouds. Anthropogenic influences can perturb clouds through aerosol changes, greenhouse gas warming, and land-surface changes. The chapter addresses these anthropogenic perturbations in terms of their impact on cloud and aerosol microphysics, radiation (both reflected shortwave and emitted longwave), precipitation (both rain and snow), atmospheric dynamics, and atmospheric chemistry.

Research on the nuclear winter phenomenon involved more than half a dozen scientific disciplines, from particle microphysics and atmospheric chemistry to ozone depletion, studies on the effects of nuclear weapons, fire and smoke research, volcanic eruptions, planetary studies, and even dinosaur extinction. This chapter describes some relevant aspects of fields with obvious connections to nuclear war.

This chapter is divided into three parts. The first analyses the network of man-made organic reactions. The second is devoted to network chemical reactions in the atmospheres of astronomical bodies such as planets and satellites in the solar system. The third examines reaction networks inside living organisms, i.e., metabolic networks. In all three parts, the role of network theory in understanding chemical, physical, or biological processes is emphasized, and special attention is given to the misunderstanding of several concepts that have led to the misuse of network theory.