Welcome to ACD.
Our mission is to advance understanding and predictive capability of atmospheric composition and related processes, and to provide intellectual leadership and facility support to the wider community.
The Atmospheric Chemistry Division (ACD) is part of the NCAR Earth System Laboratory (NESL). Research within ACD is aimed at quantifying and predicting the role of atmospheric chemistry in the Earth system through observations and modeling. Our current and near-term atmospheric chemistry research goals can be classified broadly into two areas:
Clouds are an important part of the earth's climate due to their absorption, emission, and reflectance of radiation. Understanding their formation and properties is critical to predicting earth's present and future radiative budgets. All of the water droplets within clouds were formed by condensation of water onto initial seed particles called cloud condensation nuclei (CCN), or ice nuclei (IN) in the case of ice clouds.
The composition and magnitude of volcanic gas emissions contain keys to understanding and predicting volcanic events. Additionally, some volcanic gases have a positive radiative forcing and thus impact climate. Volcanic gases are mostly analyzed in situ or using airborne instruments, with all the consequent limitations in safety and sampling, and at elevated costs.
The mean circulation of the tropical lower stratosphere is characterized by upwelling, which transports air masses across the tropopause into the lower stratosphere. This is part of the global overturning Brewer-Dobson circulation. However, this upwelling circulation is weak and cannot be measured directly, but is inferred from diagnostic calculations or observed tracer transport.
Accurate NOx emissions are essential for air pollution quantification and mitigation. Combustion processes in the transportation, industrial, and residential sector and emissions from power plants are the dominant anthropogenic sources of NOx. In addition to contributing to the formation of ground-level ozone and fine particle pollution, high levels of NOx are linked with a number of adverse effects on the respiratory system.
A proposed method for geo-engineering climate involves the injection of sulfur into the tropical stratosphere. The resulting enhanced global stratospheric aerosol burden would reflect and scatter sunlight, reducing the Earth’s surface temperature and ultraviolet (UV) radiation intensity. Chemical reactions on the surface of aerosol particles would enhance heterogeneous reactions and alter the ozone abundance, which would change surface UV radiation.
