Changes in the composition of the atmosphere can affect the habitability of the planet, for example, by altering long-term climate, depleting the ozone layer, changing radiative forcings, or affecting air quality at the ground. Research in this field is therefore concerned with biogenic and anthropogenic emissions, trace gas and aerosol distributions, and the chemical reactions of molecules, atoms and particles in the atmosphere.
Research in atmospheric chemistry at CCSR and GISS includes developments of gas-phase and aerosol schemes, which are appropriate for detailed climate impact studies as well as for long climate simulations. These schemes are evaluation through diverse projects with ground, airborne, and satellite observations.
NASA Goddard Institute for Space Studies operates the two most accurate polarimeters in the world on a range of aircraft, at altitudes from 200 m to 20 km. These instruments, called Research Scanning Polarimeters (RSP), are used to retrieve aerosol and cloud properties. In the case of aerosols the retrieved products are the size distribution and complex refractive index of the particles, their optical depth, and an estimate of layer height. Cloud retrievals consist of layer average particle size, cloud optical thickness and cloud top height for both ice and water clouds. A unique capability for water clouds is the retrieval of the droplet size distribution at cloud top, while for ice clouds the aspect ratio and level of distortion of the crystals in the cloud can be retrieved. Data from all the field experiments in which the instruments have operated since 2006 are available from the project home page.
Aerosol and Cloud Retrievals
NASA/GISS is the Global Processing Center for the International Satellite Cloud Climatology Project. ISCCP was established in 1982 as part of the World Climate Research Programme (WCRP) to collect and analyze satellite radiance measurements to infer the global distribution of clouds, their properties, and their diurnal, seasonal, and interannual variations. Data collection began on 1 July 1983 and is currently planned to continue through 30 June 2010. The resulting datasets and analysis products are being used to improve understanding and modeling of the role of clouds in climate, with the primary focus being the elucidation of the effects of clouds on the radiation balance. The ISCCP group is currently using data mining techniques to produce Level 2 cloud and atmospheric dynamics products that are then used to understand cloud processes at different scales and to evaluate and improve cloud representation in climate model simulations.
Glory was to be a remote-sensing Earth-orbiting observatory designed to achieve two primary mission objectives. One was to collect data on the physical and chemical properties as well as the spatial and temporal distributions of aerosols. The other was to continue collection of total solar irradiance data for the long-term climate record. The mission ended March 4, 2011, when the spacecraft failed to reach orbit following its launch from Vandenberg Air Force Base in California. On 6 March 2011, Dr. Michael Freilich, Director of the Earth Science Division, Science Mission Directorate, NASA Headquarters, directed the Glory APS Science Team to perform a comprehensive study intended to develop and evaluate the science rationale for an Aerosol Polarimetry Sensor (APS) reflight.
The Global Aerosol Climatology Project (GACP) was established in 1998 with the objective to extract an improved multi-decadal aerosol record from existing satellite measurements. Specifically, the main objective has been to develop advanced global aerosol climatologies for the full period of satellite data, supplement them by improved modeling results, and to make these aerosol datasets broadly available and suitable for use in studies of the direct and indirect effects of aerosols on climate. A major outcome of this collective research effort is a 23-year global aerosol climatology compiled from channel-1 and -2 AVHRR data and supplemented by data from other satellites, field observations, and chemical-transport modeling. The resulting datasets and analysis products have been used to improve the understanding and modeling of the climate forcing due to changing aerosols, including both the direct radiative forcing by the aerosols and the indirect radiative forcing caused by the effects of changing aerosols on cloud properties.