Aerosols (airborne particles) affect the formation of clouds and the amount of rain or snow they produce. They can make clouds brighter, which reduces the amount of sunlight reaching Earth. Aerosolos remain in the air for only a few days, and they vary greatly in size and other properties. A number of studies have highlighted the need for improved data on aerosols in order to reduce uncertaintly in climate predictions of climate change. Aerosols also play a major role in air quality and thus have a direct impact on human health.
By deploying a variety of coordinated sensors, ACE will assess both clouds and aerosols and clarify the relationships between them. The data it gathers will help lead to improvements in the models that predict air quality. ACE is also designed to assist the assessing the health of ocean ecosystems by sensing ocean color and the amount of organic material close to the sea surface. Observations from ACE will help scientists provide early warning of harmful algal blooms in coastal areas. These data also will help scientists calculate the amount of carbon dioxide (CO2) entering and leaving the oceans. Increases in absorbed CO2 are linked to ocean acidification, which in turn threatens the health of coral reefs and marine ecosystems.
The four main instruments for ACE consist of a lidar, for measuring cloud and aerosol heights and the thickness of certain layers; a cloud radar, to detect droplet size and cloud height; a polarimeter, to measure cloud and aerosol properties; and a multi-band spectrometer, to sample ocean properties. Some prelaunch development will be needed so that the lidar, radar, and polarimeter can carry out multi-beam and cross-track sampling.