The return of sunlight each spring to the Arctic is nice if you live up there, but the change of seasons also brings back the sunlight’s ability to catalyze ozone destruction. That process happened in a big way during March 2011. “It’s been extraordinary,” says ACD scientist James Hannigan. Since 1999, he and colleague Michael Coffey have maintained a NASA-funded infrared spectrometer at Thule, on the far northwest coast of Greenland (see photo).

Everyone could see the black cloud that forms over Cairo, but nobody knew its source. Not until former ACD doctoral candidate Heba Marey did some scientific sleuthing and solved the mystery. The source of the cloud turned out to be illegal burning of rice husks, done at night when farmers are less likely to get caught. Marey used NASA's Multi-Angle Imaging Spectroradiometer (MISR) to trace the path of the smoke plumes. More at NASA's Earth Observing System Data and Information System (EOSDIS)...

ACD scientist Fred Eisele and postdoctoral fellow Jun Zhao recently developed a highly sensitive mass spectrometer, the Cluster CIMS, capable of measuring neutral molecular clusters in the atmosphere. This instrument allows for the quantification of singly-charged clusters containing 2-4 sulfuric acid (H2SO4) molecules.

Satellite observations have revealed that cirrus is very prevalent near the tropopause throughout most of the tropics. The cirrus is of interest since it restricts the amount of water vapor that is transported from the upper troposphere into the lower stratosphere.

The global chemical transport model MOZART-4 has been recently released to the scientific community through the ACD MOZART-4 homepage and the NCAR Community Data Portal.

ACD scientists Julia Lee-Taylor and Sasha Madronich are using the GECKO-A model to investigate the formation of SOA from an explicit chemistry perspective. A typical simulation, starting with 60 precursor hydrocarbons, simulates ~5 million gas-phase reactions among ~1 million species.

The importance of lateral boundary conditions (BC) in regional atmospheric transport models or numerical prediction models has been well established in the meteorological community. Much more recently, attention has also been drawn to the consideration of chemical lateral boundary conditions in regional chemical transport models (CTMs) and in air quality simulations, and the importance of the inflow of pollution on local air quality.

The tropopause is a fundamental boundary of the atmosphere, separating the turbulent mixing dominated troposphere from the much more stable and stratified stratosphere. To examine the role of the tropopause and the jet streams in constraining the cloud distributions, ACD scientists performed an analysis of cloud top and tropopause relationships using the CALIPSO cloud data and NCEP GFS tropopause data.

New particle formation is often the dominant source of particles in remote regions. In recent years, substantial progress has been achieved in measuring the chemical composition of nanometer-sized aerosols during various stages of growth. Much of this work has been conducted in a collaborative effort between ACD’s Ultrafine Aerosols Research Group and Peter McMurry’s research group at the University of Minnesota.

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. The climatology is available to download at: http://acd.ucar.edu/~tilmes/ozone.html

The extratropical upper troposphere and lower stratosphere (Ex‐UTLS) is a transition region between the stratosphere and the troposphere. Significant progress has been made in understanding the climate-relevant processes in this region during the last decade, assisted by a suite of new observational studies. The NCAR UTLS program directed field campaigns using the GV aircraft, and these campaigns played a significant role in these new studies.

The new Version 5 (“V5”) MOPITT (Measurements of Pollution in the Troposphere) product for carbon monoxide (CO) is the first satellite product to exploit simultaneous near-infrared (NIR) and thermal-infrared (TIR) observations to enhance retrieval sensitivity in the lower troposphere. Since most major sources of tropospheric CO are found at or near the Earth's surface, this feature will improve air quality forecasts and studies of CO sources.