Abstract

Dual-polarization lidar data and radiosonde data are used to determine that iridescence in cirrus and a lunar corona in a thin wave cloud were caused by tiny ice crystals, not droplets of liquid water. The size of the corona diffraction rings recorded in photographs is used to estimate the mean diameter of the diffracting particles to be 14.6μm, much smaller than conventional ice crystals. The iridescent cloud was located at the tropopause [1113.6km above mean sea level (ASL)] with temperature near 70°C, while the more optically pure corona was located at approximately 9.5km ASL with temperature nearing 60°C. Lidar cross-polarization ratios of 0.5 and 0.4 confirm that ice formed both the iridescence and the corona, respectively.

© 2011 Optical Society of America

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References

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2008 (1)

2006 (1)

N. L. Seldomridge, J. A. Shaw, and K. S. Repasky, “Dual-polarization lidar using a liquid crystal variable retarder,” Opt. Eng. 45, 106202, doi:10.1117/1.2358636 (2006).
[CrossRef]

2003 (4)

1998 (1)

1991 (2)

Gedzelman, S. D.

Goodman, J. W.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, 1996).

Hallett, J.

Lock, J. A.

Mace, G. G.

Neiman, P. J.

P. J. Neiman and J. A. Shaw, “Coronas and iridescence in mountain wave clouds over northeastern Colorado,” Bull. Am. Meteorol. Soc. 84, 1373–1386 (2003).
[CrossRef]

J. A. Shaw and P. J. Neiman, “Coronas and iridescence in mountain wave clouds,” Appl. Opt. 42, 476–485 (2003).
[CrossRef] [PubMed]

Poellot, M. R.

Repasky, K. S.

N. L. Seldomridge, J. A. Shaw, and K. S. Repasky, “Dual-polarization lidar using a liquid crystal variable retarder,” Opt. Eng. 45, 106202, doi:10.1117/1.2358636 (2006).
[CrossRef]

Sassen, K.

Seldomridge, N. L.

N. L. Seldomridge, J. A. Shaw, and K. S. Repasky, “Dual-polarization lidar using a liquid crystal variable retarder,” Opt. Eng. 45, 106202, doi:10.1117/1.2358636 (2006).
[CrossRef]

Shaw, J. A.

N. L. Seldomridge, J. A. Shaw, and K. S. Repasky, “Dual-polarization lidar using a liquid crystal variable retarder,” Opt. Eng. 45, 106202, doi:10.1117/1.2358636 (2006).
[CrossRef]

P. J. Neiman and J. A. Shaw, “Coronas and iridescence in mountain wave clouds over northeastern Colorado,” Bull. Am. Meteorol. Soc. 84, 1373–1386 (2003).
[CrossRef]

J. A. Shaw and P. J. Neiman, “Coronas and iridescence in mountain wave clouds,” Appl. Opt. 42, 476–485 (2003).
[CrossRef] [PubMed]

Yang, L.

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Figures (7)

Fig. 1
Fig. 1

Photograph of iridescence in cirrus cloud ( altitude = 13.4 km ASL) on 3 February 2009 at 1600 MST (2300 UTC). Photo by J. A. Shaw using a Nikon D300 and an 18 200 mm VR zoom lens set at 60 mm , ISO250, f / 14 , 1 / 800 s exposure.

Fig. 2
Fig. 2

Photograph of lidar beam and lunar corona on 4 February 2009 at 2032 MST (6 February, 0332 UTC). Photograph by J. A. Shaw using a Nikon D300 camera, a 10.5 mm fisheye lens, ISO 400, f / 2.8 , 4.0 s exposure.

Fig. 3
Fig. 3

Lunar corona photograph used for the diffraction analysis [photograph by J. A. Shaw on 4 February 2009 at 2034 MST (6 February, 0332 UTC), using a Nikon D300 camera and a 20 mm fisheye lens, ISO 1000, f / 2.8 , 2.0 s exposure]. The three horizontal black lines across the corona indicate the diam eters of the first-order red ring (top), the second-order blue ring (center), and the second-order red ring (bottom).

Fig. 4
Fig. 4

Radiosonde profiles of atmospheric temperature (left) and relative humidity (right) above Bozeman, Montana (ground altitude 1.5 km ) near 1700 MDT on 3 February 2009 (0000 UTC on 4 February) during the iridescence display of Fig. 1.

Fig. 5
Fig. 5

Synoptic radiosonde profiles of temperature (left) and humidity (right) at 00 UTC, 6 February 2009, from Great Falls, Montana. The lunar corona observations (Fig. 2) were made during 0200-0400 UTC on 6 February 2009 while the tropopause was beginning to lower from 11.7 km at 00 UTC to 10.0 km at 12 UTC.

Fig. 6
Fig. 6

Altitude plot of range-corrected relative lidar backscatter signal at 0330 UTC on 6 February 2009: (left) copolarized signal and (right) cross-polarized signal.

Fig. 7
Fig. 7

Altitude plot of lidar cross-polarization ratio at 0330 UTC, 6 February 2009, showing ice clouds at 9.5 and 11.3 km ASL (and zero-mean noise above the second cloud layer).

Tables (2)

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Table 1 Corona Ring Dimensions and Resulting Cloud Particle Diameter

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Table 2 Tropopause Altitudes and Temperatures from Synoptic Soundings at Great Falls, Montana

Equations (5)

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D r λ z D θ r λ = 0 , 1.635 , 2.679 , 3.699 ,
D r λ z D θ r λ = 1.220 , 2.233 , 3.238 ,
α image = 2 tan 1 ( 15.8 2 f ) .
Δ θ pixel = α image # pixels = 752.4 mrad 2848   pixels = 0.264 mrad / pixel .
θ r = N dia Δ θ pixel 2 .

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