Simulation and analysis of pollen coronas

Abstract

By numerical simulation of light scattering by birch and pine pollen grains, we create color plates of coronas with vertical elliptical shapes and strong brightenings, respectively. The shape of the pollen is modeled by the union of n ellipsoids. The Fraunhofer integral is solved by the use of the fast Hartley transform. The sensitivity of the patterns to pollen orientation, Sun elevation, and pollen shape and size is discussed. Good agreement is obtained with amazing photographs made by a Finnish network of amateur astonomers, in the case of strong vertical orientation of the pollen axis.

Coronas and Iridescence in Mountain Wave Clouds Over Northeastern Colorado

“…It is likely that the change of angular radii reflected the growth of ice particles in the upwardmotion portion of the wave cloud, especially given that a small component of the upper-tropospheric flow was directed from the top of the corona (near the upwind edge of the cloud) to the bottom. This oblong corona was generated by a spatial variation in cloud particle size distribution across the corona, whereas previous studies describe oblong coronas resulting from diffraction by oblong-shaped pollen (Parviainen et al 1994;Trankle and Mielke 1994).…”

“…Most coronas are nearly circularly shaped, although oblong-shaped coronas can arise from diffraction by nonspherical pollen in the clear air (Parvianen et al 1994;Trankle and Mielke 1994). A closely related variation is nearly circular coronas that are caused by juniper pollen in the otherwise clear air (Mims 1998).…”

“…Figure 11 shows a series of corona simulations, graciously provided by S. Gedzelman (2003, personal communication), which were obtained in a method similar to that employed by several authors of recent publications (Trankle and Mielke 1994;Lock and Yang 1991;Laven 2003;Gedzelman and Lock 2003). The leftmost panel in Fig.…”

Primary biological aerosol particles in the atmosphere: a review

“…Spankuch et al (2000) showed that down-welling infrared flux was significantly increased when pine pollen concentrations were higher, suggesting that emissions of certain pollens may cause localised atmospheric warming events. Several groups have shown that pollen can cause visible coronae around the sun and moon and could therefore influence local solar radiation properties (Parviainen et al, 1994;Trankle and Mielke, 1994;Mims, 1998;Schneider and Vollmer, 2005).…”

Simulating coronas in color

“…During periods in spring in some forested or even desert regions, air fills with pollen grains of one dominant species at a time and coronas result because the grains have relatively uniform size and fall with more-or-less the same orientation. [7][8][9] Gedzelman saw a pollen corona on 31 March at Phantom Ranch at the base of the Grand Canyon, Arizona.…”