- For Staff
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:
The Montreal Protocol on Substances that Deplete the Ozone Layer and its amendments mandate assessments of the status of atmospheric ozone every four years. A key input to these assessment reports is derived from integrations of models that simulate the past, present, and future chemistry of the ozone layer. Integrations using the whole atmosphere option of the CESM are underway for the upcoming 2014 assessment. This model, known as the Whole Atmosphere Community Climate Model (WACCM), simulates interactive chemistry from the Earth’s surface to above 100 km.
HIRDLS observations have shown a strong increase in gravity wave momentum flux (MF) in the stratosphere as a result of deep convection due to the monsoons. Annualised measurements of GW MF from HIRDLS (Figure 1, top) show a strong positive correlation with rainfall (blue line) and a strong anticorrelation with outgoing longwave radiation (green line), a standard proxy for convective activity. Measurements suggest that the Indian monsoon leads to a 25% increase in the measured momentum flux levels in this region, with half the annual total MF generated during the monsoon season.
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.