ACOM

Photolysis of Organic Aerosols

A multitude of recent atmospheric observations show that organic aerosols are ubiquitous and often more abundant than other particles such as sulfate, nitrate, soot, and dust.  These large amounts of organic particles contribute to the health impacts of air pollution, to regional visibility reductions, to both cooling and warming tendencies of radiative forcing, and to modified cloud properties and precipitation patterns.  Uncertainties remain in all aspect of their lifecycle, i.e., their formation, transformations and properties, and especially their removal.

Gas-Phase Dry Deposition as a Major Removal Mechanism for Secondary Organic Aerosols (SOA)

Water droplets on a leaf, by Siddharth Patil at Wikimedia Commons

Removal of secondary organic aerosols (SOA) from the atmosphere has been studied far less than its equal, production.  In current regional and global chemistry models rainout is the dominant loss of SOA. Here we show the importance of a less direct pathway, in which large scale evaporation of SOA particles occurs as a re-adjustment to gas-particle partitioning when semi-volatile organic gases are lost by dry deposition to the Earth’s surface.

The CONvective TRansport of Active Species in the Tropics (CONTRAST) Experiment

UTLS, convective transport in the tropics

ACD scientists in collaboration with colleagues from seven universities successfully sampled atmospheric composition over the Western Pacific warm pool region during the season characterized by massive convective storms.  The CONvective TRansport of Active Species in the Tropics (CONTRAST) experiment successfully concluded its field phase during January-February 2014. 

Secondary Organic Aerosols (SOA)

Secondary Organic Aerosol (SOA) formation in aqueous particles

Recent research suggests that in-cloud and in-particle chemistry could contribute substantially to the formation of SOA. Glyoxal is one of the precursors proposed to be important. In Knote et al. (2013) we included the state of knowledge on SOA formation from glyoxal into WRF-chem and conducted simulations over California as well as the continental United States for summer 2010.

Drought-Amplified CO Emissions in Amazonia

http://commons.wikimedia.org/wiki/File:ISS029-E-008032_Fires_along_the_Rio_Xingu_-_Brazil.jpg

Fires in Amazonia principally occur during the dry season lasting roughly from July to October and are concentrated in the 'arc of deforestation' spanning across the southern and eastern basin margins.  While much of the biomass burning activity in Amazonia follows directly from deforestation associated with agricultural practices, human-caused fires often escape from deforested areas into neighboring standing forests.  These fires typically burn below the forest canopy and cause long-term dama

WACCM Model Simulates Global Environmental Effects of a Regional Nuclear War

A closeup of the fireball and mushroom cloud from the Upshot-Knothole Grable atomic bomb; National Nuclear Security Administration

A regional nuclear conflict between India and Pakistan would not only inflict immediate damage in the subcontinent, including massive loss of life and destruction of built infrastructure; severe long-term environmental damage would also spread globally, lasting decades, researchers have found.

New ozonesonde climatology between 1995 and 2009

UTLS ozone in Western Europe

A new ozonesonde climatology for the period 1995-2009 was compiled for model evaluation and comparison to other observations [Tilmes et al., 2011]. This climatology allows evaluating the performance of ozone especially in the troposphere and lower stratosphere. Various models still show significant shortcomings to reproduce the structure and seasonality of ozone, one of the most important trace gases in the atmosphere.

Elevated Stratopause Events

Elevated stratopause event

The Whole Atmosphere Community Climate Model (WACCM) simulates many features of the stratosphere, including the very active dynamics in Northern Hemisphere winter. During midwinter in some years, there are major breakdowns of the polar winter vortex known as sudden stratospheric warmings. The frequency and development of these events simulated in WACCM are similar to observations.

Hunting for molecular species in newly formed biogenic nanoparticles

Dr. Paul Winkler with the TDCIMS instrument.

New particle formation, the spontaneous creation of new nanometer-sized particles in the atmosphere, is often the dominant source of particles in remote regions. A major part of newly formed aerosol consists of organic material that can be attributed to photo-chemically reacted volatile organic compounds emitted by vegetation. Understanding the mechanisms responsible for the growth of these biogenic nanoparticles into sizes where they may scatter radiation efficiently or change cloud properties is vitally important for assessing the impacts of new particle formation on climate.

MOPITT's 'Multispectral' View of Recent Russian Fires

Russian firefighter

During the summer of 2010, large areas of central Russia were devastated by extensive wildfires burning through forests and dry peat bogs. In addition to the threat from the actual fires, the smoke and pollutants generated by the fires created an air quality crisis for millions of Russians, including residents of Moscow. Figure 1 below shows imagery from the MODIS satellite instrument for Aug. 8; a vast smoke plume is clearly evident.

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ACOM | Atmospheric Chemistry Observations & Modeling