Idaho Glory

OPOD has many examples of Ed Stockard's spectacular Greenlandic atmospheric optics (1,2,3,4,5,6). He imaged this glory over central Idaho.

Ed's photostream

©Ed Stockard, shown with permission.

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The glory is backscattered and diffracted light from tiny cloud droplets.

Freshly formed cloud can have droplets all nearly of the same size. As the cloud ages, collisions between droplets plus the effects of evaporation and re-condensation conspire to change the droplet sizes. The mean size increases and the size distribution broadens.

The effect of this on glories, coronae and fogbows is to effectively blur out their finer details and subdue their colours. Simple superimposition of the different size diffraction patterns from each droplet does this.

At left are IRIS Mie scattering computations for glories from monodisperse droplets and ones with a 15% (stand deviation of normal distribution) spread of diameters.

Ed Stockard's glory shows traces of three rings. An indication of droplets of very similar size although that size varies from one part of the cloud layer to another.

Monodisperse droplets

Droplets with a 15% (std dev) size spread