Changes in Atmospheric Constituents and in Radiative Forcing

Chlorofluoromethanes are being added to the environment in steadily increasing amounts. These compounds are chemically inert and may remain in the atmosphere for 40–150 years, and concentrations can be expected to reach 10 to 30 times present levels. Photodissociation of the Chlorofluoromethanes in the stratosphere produces significant amounts of chlorine atoms, and leads to the destruction of atmospheric ozone.

Stratospheric sink for chlorofluoromethanes: chlorine atomc-atalysed destruction of ozone

The Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT), developed by NOAA’s Air Resources Laboratory, is one of the most widely used models for atmospheric trajectory and dispersion calculations. We present the model’s historical evolution over the last 30 years from simple hand-drawn back trajectories to very sophisticated computations of transport, mixing, chemical transformation, and deposition of pollutants and hazardous materials. We highlight recent applications of the HYSPLIT modeling system, including the simulation of atmospheric tracer release experiments, radionuclides, smoke originated from wild fires, volcanic ash, mercury, and wind-blown dust.

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NOAA’s HYSPLIT Atmospheric Transport and Dispersion Modeling System

MOST volcanic rocks in modern island and continental arcs are probably derived from melting of the mantle wedge, induced by hydrous fluids released during dehydration reactions in the subducted lithosphere1. Arc tholeiitic and calc-alkaline basaltic magmas are produced by partial melting of the mantle, and then evolve by crystal fractionation (with or without assimilation and magma mixing) to more silicic magmas2—basalt, andesite, dacite and rhyolite suites. Although most arc magmas are generated by these petrogenetic processes, rocks with the geochemical characteristics of melts derived directly from the subducted lithosphere are present in some modern arcs where relatively young and hot lithosphere is being subducted. These andesites, dacites and sodic rhyolites (dacites seem to be the most common products) or their intrusive equivalents (tonalites and trondhjemites) are usually not associated with parental basaltic magmas3. Here we show that the trace-element geochemistry of these magmas (termed 'adakites') is consistent with a derivation by partial melting of the subducted slab, and in particular that subducting lithosphere younger than 25 Myr seems to be required for slab melting to occur.

Derivation of some modern arc magmas by melting of young subducted lithosphere

Aerosol radiative forcing is a critical, though variable and uncertain, component of the global climate. Yet climate models rely on sparse information of the aerosol optical properties. In situ measurements, though important in many respects, seldom provide measurements of the undisturbed aerosol in the entire atmospheric column. Here, 8 yr of worldwide distributed data from the AERONET network of ground-based radiometers were used to remotely sense the aerosol absorption and other optical properties in several key locations. Established procedures for maintaining and calibrating the global network of radiometers, cloud screening, and inversion techniques allow for a consistent retrieval of the optical properties of aerosol in locations with varying emission sources and conditions. The multiyear, multi-instrument observations show robust differentiation in both the magnitude and spectral dependence of the absorption—a property driving aerosol climate forcing, for desert dust, biomass burning, urban‐industrial, and marine aerosols. Moreover, significant variability of the absorption for the same aerosol type appearing due to different meteorological and source characteristics as well as different emission characteristics are observed. It is expected that this aerosol characterization will help refine aerosol optical models and reduce uncertainties in satellite observations of the global aerosol and in modeling aerosol impacts on climate.

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Variability of Absorption and Optical Properties of Key Aerosol Types Observed in Worldwide Locations

Place, partnerships, and practice – geoheritage education initiatives in michigan’s keweenaw region

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D.R. Sherrod, W.E. Scott, P.H. Stauffer (eds): A volcano rekindled: the renewed eruption of Mount St. Helens, 2004–2006

A unique, new educational program that focuses on geological natural hazards, U.S. Peace Corps field work, and on-campus study has begun its second year at Michigan Technological University, in Houghton, Michigan.

While “Masters International” programs that combine Peace Corps service with a graduate degree program are available at 49 different universities in a variety of fields, the program at Michigan Tech is the only one with a natural hazards focus offering geological degree programs.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005EO340003

Geohazards Graduate Study With the U.S. Peace Corps

The Alaskan eruptions of Augustine Volcano (1986) and Redoubt Volcano (1989-90) were major hazards to air traffic at Anchorage, along a major polar air route. Detailed examinations were made of multispectral imagery collected by the advanced very high resolution radiometer (AVHRR) aboard polar orbiting NOAA weather satellites. More than 70 images of eruptions from the two volcanoes, which exhibit a great variety of eruptive and atmospheric conditions have been examined. The data set offers an elaborate test of the utility of synoptic weather satellites for discriminating and tracking eruption clouds. The results so far are very encouraging, demonstrating a success in discrimination and mapping of eruption clouds under a variety of conditions. The two eruptions have different spectral characteristics, which have precluded the use of a single algorithm to discriminate eruption clouds from meteorological ones. Laboratory spectral study of ashes collected from the field are being used to help understand differing spectral characteristics of ash clouds as detected by the AVHRR.

William I. Rose

Papers

Place, partnerships, and practice – geoheritage education initiatives in michigan’s keweenaw region

D.R. Sherrod, W.E. Scott, P.H. Stauffer (eds): A volcano rekindled: the renewed eruption of Mount St. Helens, 2004–2006

Geohazards Graduate Study With the U.S. Peace Corps

Remote sensing of volcanic ash hazards to aircraft

To Richard Edwin Stoiber