Form and Origin of the Parry Arcs

Complex Ice‐crystal Halo Phenomena: Sky Archaeology

“…When the s u n is lower in the sky, the relation between the top of the 46" halo and the zenith would be correct and both of the missing arcs could appear. At a solar elevation around 25", the lower tangent arc or lower sunvex Parry arc would appear approximately as shown (Greenler et al 1977) and the circumzenithal arc would circle the zenith as in the drawing. It appears that Lowitz's drawing is not a 'snapshot picture' of the display as it appeared a t 10 00 am, but rather a composite of sketches he made over the long duration of this spectacular display.…”

“…The calculation also includes intensity information which is expressed in the spot diagram by a selective discarding of points, determined by the calculated value of the intensity. (See, for example, Greenler et a/. 1977.…”

“…(Greenler and Mallmann 1972. ) (4) If there is an additional degree of orientation so that a pair of long side faces are constrained to be horizontal (f3") the upper suncave Parry arc shown in the simulation, arching over the top of the upper tangent arc, is produced by rays C. (Greenler et al 1977. ) Photograph by R. G. Greenler…”