Radiation atmosphere and

Meteorites, atmospheric radiation and, 3 299 Meteorology, radiation and, 3 293 Methacrylic esters, photocatalytic conversion, 43 431 Methane... 

C. AEROSOL PARTICLES, ATMOSPHERIC RADIATION, AND CLIMATE CHANGE... 

Aerosol concentrations and size distributions can be investigated remotely using sun-photometry. Characterization of volcanic aerosol is important in smdies of plume chemistry, atmospheric radiation, and the environmental and health impacts of particle emissions. Watson and Oppenheimer (2000, 2001) used a portable sun-photometer to observe tropospheric aerosol emitted by Mt. Etna. They found distinct aerosol optical signatures for the several plumes emitted from Etna s different summit craters, and apparent coagulation of particles as the plume aged. More recently. Porter et al. (2002) have obtained sun-photometer and pulsed lidar data for the plume from Pu u O o vent on Kilauea, Hawaii, from a moving vehicle in order to build profiles of sulfate concentration. 

There is considerable interest in volcanic emissions of sulfur compounds because of the role of atmospheric sulfur chemistry in atmospheric radiation and climate, the hydrological cycle, acid precipitation, and air quality (see Chapter 8.14). Early theories on the climatic effects of eruptions considered that ash particles were responsible for raising the planetary albedo, but it is now clear that even fine tephra sediment rapidly from the atmosphere, and that the main protagonist in volcanic forcing of climate is the... 

Aerosol particles resulting from the 1991 eruption of Mount Pinatubo (Philippines) are widely cited in the recent atmospheric literature because of their global effects on atmospheric radiation and climate (Hansen et al., 1992 McCormick et al., 1995). However, volcanic eruptions occur every year, and some have been far larger than Pinatubo. For comparison, Krakatoa (1883 between Java and Sumatra, Indonesia) and Tambora (1815 Sumbawa, Indonesia), respectively, emitted double and ten times as much pyroclastic debris into the atmosphere as Pinatubo, and significantly reduced sunlight around the globe for months (Sparks et al., 1997). Their effects on the atmosphere have been profound. 

Water is abundant on our planet, distinguishing Earth from all other planets in the solar system. More than 97% of Earth s water is in the oceans, with 2.1% in the polar ice caps and 0.6% in aquifers. The atmosphere contains only about one part in a hundred thousand (0.001%) of Earth s available water. However, the transport and phase distribution of this relatively small amount of water (estimated total liquid equivalent volume of 13,000 km3) are some of the most important features of Earth s climate. The existence of varying pressures and temperatures in the atmosphere and at the Earth s surface causes water to constantly transfer among its gaseous, liquid, and solid states. Clouds, fogs, rain, dew, and wet aerosol particles represent different forms of that water. Aqueous atmospheric particles play a major role in atmospheric chemistry, atmospheric radiation, and atmospheric dynamics. 

---