Invited Presentation: Satellite detection of impacts of urban pollution plumes on cloud microstructure and precipitation forming processes

The Visible Infrared Imager Radiometer Suite (VIIRS) onboard the new NPP satellite represents an improvement of spatial resolution by a factor of 3 with respect to the Advance Very High Resolution Radiometer (AVHRR), that has been in use for over 25 years onboard the NOAA polar orbiting satellites. It represents a similar improvement of the resolution with respect to the MODIS channels that allow retrieving cloud microstructure. The ability to retrieve cloud properties at the nominal spatial resolution of 375 m allows resolving the convective elements of boundary layer clouds with unprecedented detail. Observing cloud drop effective radius (r_e) and temperature (T) over urban and industrial areas enable pinpointing the pollution sources and observing their impacts on the clouds. Examples that will be presented include:

1. Clouds over Manaus in the Amazon and downwind appear to have largely reduced r_e, and warm rain showers are inferred to be suppressed.

2. The retrieved cloud properties make it possible to map qualitatively the relative amounts of pollution aerosols over the Houston area. When taking into account the wind direction, this can help in mapping the pollution sources.

3. Emissions from coal power plants affect conspicuously individual small clouds. This allows the identification of the active polluting stacks.

These observed changes in cloud microstructure and inferred precipitation forming processes help in separating the aerosol and heat island effects on precipitation, cloud electrification and severe convective storms.