Lightning in a Clear Sky

Polarization singularities in the clear sky

Ideas from singularity theory provide a simple account of the pattern of polarization directions in daylight. The singularities (two near the Sun and two near the anti-Sun) are points in the sky where the polarization line pattern has index +1/2 and the intensity of polarization is zero. The singularities are caused by multiple scattering that splits into two each of the unstable index +1 singu...

Digital imaging of clear-sky polarization.

If digital images of clear daytime or twilight skies are acquired through a linear polarizing filter, they can be combined to produce high-resolution maps of skylight polarization. Here polarization P and normalized Stokes parameter Q are measured near sunset at one inland and two coastal sites. Maps that include the principal plane consistently show that the familiar Arago and Babinet neutral ...

A clear-sky radiance archive from Meteosat ”water vapor” observations

Blue Skies: A Methodology for Data-Driven Clear Sky Modelling

Solar energy is gaining prominence across the world in response to climate change, depleting reserves, lowering costs, and favorable legislation. However, a key challenge in integrating solar power into the grid is the ability to forecast solar energy production accurately. The variability and uncertainty of solar power can negatively impact grid stability and increase the cycling costs of conv...

Color and luminance asymmetries in the clear sky.

A long-standing assumption about the clear sky is that its colors and luminances are distributed symmetrically about the principal plane. As useful as this approximation is, our digital-image analyses show that clear-sky color and luminance routinely depart perceptibly from exact symmetry. These analyses reconfirm our earlier measurements with narrow field-of-view spectroradiometers [J. Opt. So...