Precipitation Intensityand

Cloud Physics

Brad Eck

April 26, 2007

Data Sources

• Precipitation Intensity– North American Regional Reanalysis (NARR)– netCDF (thanks to Cedric)– Units: kg/m^2/s mm/s

• Cloud Physics– Moderate Resolution Imaging Spectrometer

(MODIS)– Optical Thickness

Optical Thickness

• “…a measure of how opaque a medium is to radiation passing through it.” http://scienceworld.wolfram.com/physics/OpticalDepth.html

• “The (dimensionless) line integral of the absorption coefficient…along any path in a … medium.” http://amsglossary.allenpress.com/glossary/search?id=optical-thickness1

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Source: King et. al., “Remote sensing of cloud, aerosol, and water vapor properties from the Moderate Resolution Imaging Spectrometer (MODIS),” IEEE Trans. Geosci. Remote Sens. 30, 2-27 (1992).

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• Optical thickness combines droplet size, water content and cloud height to give a normalized cloud size

• Bigger clouds should have a higher precipitation intensity

May 2006