OSIRIS measurements of cloud and aerosol in the upper troposphere and lower stratosphere

The Canadian designed and built Optical Spectrograph and Infrared Imaging System (OSIRIS) satellite instrument measures the spectrum of limb scattered sunlight at wavelengths from the ultraviolet (275 nm) to the near infrared (815 nm) with approximately 2 km vertical resolution and daily, nearly global coverage since launch in 2001. In this work we present a technique for the characterization of the presence of cirrus clouds using the measurements at near infrared wavelengths. Probability density functions of the scattering ratio reveal a clear distinction between the cloudy and cloud-free conditions; this is used to produce altitude resolved maps of cloud occurrence frequency. Furthermore this technique is used to study the recently reported Asian aerosol layer, which has been detected in CALIPSO measurements of the upper troposphere and lower stratosphere coincident with the Asian monsoon. The OSIRIS "cloud-free" measurements reveal the presence of a scattering aerosol layer with a temporal spatial distribution very similar to that reported by CALIPSO.