Study of droplet size variability in the transition zone between cloudy and clear air using surface-based hyperspectral observations

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Description

Using surface-based hyperspectral observations collected during the MAGIC field campaign, we present the first surface-based look at the variability in droplet size at the cloud edge and through the transition into clear sky. From July 2013 through September 2013, the Solar Spectral Flux Radiometer (SSFR) was deployed as a part of the MAGIC campaign. The SSFR is a shortwave, moderate resolution spectrometer with a wavelength range from 350 nm to 1700 nm and shares its heritage with the Shortwave Spectrometer (SWS). We present an innovative algorithm, applicable to hyperspectral observations, that provides qualitative information about the changing size of the cloud particles approaching the cloud edge. Building on previous work within our group, the algorithm relies on spectral invariant cloud properties. The slope of the linear fit over visible wavelengths depends mostly on the cloud optical thickness while the intercept of the fit over near-infrared wavelengths depends on both optical thickness and effective droplet radius. This contrast in dependencies enables the use of the regression line parameters to study the droplet size changes in the transition zone.