We consider the effects of 'small' nuclear detonations in modern i?megacities,i? focusing on the possible extent of fire ignitions, and the properties of corresponding smoke emissions. Explosive ...devices in the multi-kiloton yield range are being produced by a growing number of nuclear states (Toon et al., 2006), and such weapons may eventually fall into the hands of terrorists. The numbers of nuclear weapons that might be used in a regional conflict, and their potential impacts on population and infrastructure, are discussed elsewhere. Here, we estimate the smoke emissions that could lead to widespread environmental effects, including large-scale climate anomalies. We find that low-yield weapons, which emerging nuclear states have been stockpiling, and which are likely to be targeted against cities in a regional war, can generate up to 100 times as much smoke per kiloton of yield as the high-yield weapons once associated with a superpower nuclear exchange. The fuel loadings in modern cities are estimated using a variety of data, including extrapolations from earlier detailed studies. The probability of ignition and combustion of fuels, smoke emission factors and radiative properties, and prompt scavenging and dispersion of the smoke are summarized. We conclude that a small regional nuclear war might generate up to 5 teragrams of highly absorbing particles in urban firestorms, and that this smoke could initially be injected into the middle and upper troposphere. These results are used to develop smoke emission scenarios for a climate impact analysis reported by Oman et al. (2006). Uncertainties in the present smoke estimates are outlined. Oman, L., A. Robock, G. L. Stenchikov, O. B. Toon, C. Bardeen and R. P. Turco, i?Climatic consequences of regional nuclear conflicts,i? AGU, Fall 2006. Toon, O. B., R. P. Turco, A. Robock, C. Bardeen, L. Oman and G. L. Stenchikov, i?Consequences of regional scale nuclear conflicts and acts of individual nuclear terrorism,i? AGU, Fall 2006.
The Orbiting Carbon Observatory (OCO) mission (Crisp, D., et al., Adv. Space Res., 34, 700-709, 2004) will make the first global, space-based measurements of atmospheric CO2 with the precision and ...coverage needed to characterize CO2 sources and sinks on regional scales. During its 2-year mission, OCO will fly in a sun-synchronous orbit with a 16-day ground-track repeat time, just ahead of the EOS Aqua platform. OCO incorporates three bore-sighted high-resolution spectrometers (deltanu approx 0.3 cm-1) to measure reflected sunlight in the O2 A-band (0.76 mum) and two CO2 bands at 1.61 and 2.06 mum, respectively. Each sounding recorded in these three bands will be analyzed simultaneously to retrieve the column-averaged CO2 dry air mole fraction (XCO2) with a retrieval algorithm that incorporates an atmospheric radiative transfer model, an instrument simulator model, and an inverse method (Bosch, H., et al. J. Geophys. Res., 111, D23302, doi:10.1029/2006JD007080, 2006). In order to verify and improve the space-based CO2 measurements, the OCO project incorporates a comprehensive validation program based on ground-based Fourier Transform Spectrometers (FTS) measuring direct sunlight. These high-resolution measurements (deltanu = 0.011 cm-1; OPD = 45 cm) are ideally suited to OCO validation since their vertical sensitivities are very similar and the same O2 and CO2 absorption bands are used. As an important part of this strategy, solar-absorption spectra will be simultaneously acquired at JPL by an FTS and the OCO spectrometers during its first calibration tests planned in September, 2007. These measurements will be analyzed using the OCO retrieval algorithm as well as GFIT (an algorithm designed specifically for FTS analysis.) We will discuss the planned validation exercise (e.g., FTS vs OCO spectrometry, XCO2 inter-comparison), the solar-absorption measurement and present first results of the OCO instrument line shape (ILS) and the retrieved XCO2.
Recent exploration by the Cassini/Huygens mission has stimulated a great deal of interest in Saturn's moon, Titan. One of Titan's most captivating features is the thick organic haze layer surrounding ...the moon, believed to be formed from photochemistry high in the CH4/N2 atmosphere. Here we report laboratory experiments to demonstrate the chemical and physical properties of haze material formed via photochemistry, similar to such processing on Titan. We have used a deuterium lamp to initiate particle production in these simulated atmospheres from UV photolysis. Using a novel analysis technique, the Aerosol Mass Spectrometer, we have studied the chemical composition, size, and shape of the particles produced as a function of initial trace gas composition. Our results show that the aerosols produced in the laboratory can serve as analogs for the observed haze in Titan's atmosphere. We have used quantitative data obtained for aerosol production from photochemistry to model the mass production rate as a function of CH4 concentration. It has been suggested that a similar haze layer may have formed on the early Earth. Laboratory experiments were also performed under possible conditions for early Earth, and these data suggest a significant optical depth of haze may have dominated the early Earth's atmosphere. The similarities and differences to haze production on Titan are discussed. Using the developed model and comparisons to Titan, we estimate that aerosol production on the early Earth may have been on the order of 1014 g year-1.
