This streaming video shows the transport of particulate pollution across the North Pacific in 2003, as observed by the moderate resolution imaging spectroradiometer (MODIS) onboard the Terra satellite. Particulate pollution is represented by optical thickness, a measurement of how well a slice of atmosphere transmits light. The greater the value of optical thickness for a given location, the less light of a particular wavelength can pass through it and the larger quantities of tiny particles that are suspended in the air. Heavy aerosol concentrations appear in shades of brown, with darker shades representing greater concentrations.