Abstract

A dense volcanic cloud from the El Chichon volcanic eruption has been observed in the stratosphere over Hawaii since it was first discovered at the Mauna Loa Observatory 9 Apr. 1982. Lidar observations have shown the cloud to have been dense and highly layered in its early stages, but as the cloud matured it became more homogeneous and the top portion underwent considerable enhancement. Measurements of the degree of polarization of skylight at the zenith and across the sky in the sun’s vertical show that the polarization field is strongly modified by the effects of the cloud and that the modifications are of a different nature from those produced by high turbidity in the lower layers of the atmosphere. The degree of polarization at the zenith during twilight shows a secondary maximum at a solar depression D = 4.8–5°, a secondary minimum at D = 4°, a primary maximum at D = 1–2°, and a rapid decrease to values generally <10% in the immediate sunrise period. The positions of the neutral points are strongly affected by the cloud, the Arago point being shifted from its normal position by as much as 15–20° and the Babinet point being shifted even farther. Multiple Babinet points were observed on some occasions. The measurements indicate the polarization field to be modified more by the El Chichon cloud than it was by the clouds from previous eruptions which have occurred during this century.

© 1983 Optical Society of America

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References

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  1. Z. Sekera, Polarization of Skylight, Compedium of Meteorology (American Meteorological Society, Boston, 1950), pp. 79–90.
  2. Z. Sekera, J. Opt. Soc. Am. 47, 484 (1957).
    [CrossRef]
  3. F. Volz, J. Geophys. Res. 75, 5185 (1970).
    [CrossRef]
  4. F. Volz, J. Geophys. Res. 80, 2643 (1975).
    [CrossRef]
  5. G. Steinhorst, Appl. Opt. 13, 219 (1974).
    [CrossRef]
  6. K. L. Coulson, Appl. Opt. 19, 3469 (1980).
    [CrossRef] [PubMed]
  7. K. L. Coulson, Appl. Opt. 20, 1516 (1981).
    [CrossRef] [PubMed]
  8. E. C. Pickering, “A New Form of Polarimeter,” in Proceedings, American Academy of Arts and Sciences XIII, New Series (1884), pp. 294–302.
  9. A. Cornu, “Observations relative a la couronne visible actuellement autour du Soleil,” C. R. Acad. Sci. Paris 99, 488 (1884).
  10. H. H. Kimball, “Observations of Solar Radiation with the Angstrom Pyrheliometer at Asheville and Black Mountain, N.C.,” Mon. Weather Rev. 31, 320 (1903).
    [CrossRef]
  11. H. H. Kimball, “The Effect upon Atmospheric Transparency of the Eruption of Katmai, Volcano,” Mon. Weather Rev. 41, 153 (1913).
    [CrossRef]
  12. H. H. Kimball, “The Effect of the Atmospheric Turbidity of 1912 on Solar Radiation Intensities and Skylight Polarization,” Bulletin Mt. Weather Observatory V, 295 (1913).
  13. C. Dorno, “Himmelselligkeit, Himmelspolarisation, und Sonnenintensitat in Davos (1911 bis 1918),” Meteorol. Z. 36, 109, 181 (1919).
  14. G. M. Shah, Tellus 21, 636 (1969).
    [CrossRef]
  15. J. V. Dave, K. R. Ramanathan, Proc. Indian Acad. Sci. Sect. A 43, No. 2, 67 (1956).
  16. J. V. Dave, Proc. Indian Acad. Sci. Sect. A 43, No. 6, 336 (1956).
  17. F. Link, M. T. Martel, Ann. Geophys. 32, 157 (1976).
  18. G. V. Rozenberg, Twilight: A Study in Atmospheric Optics, A. E. Stibb, Translator (Plenum, New York, 1966).
  19. W. G. Blattner, H. G. Horak, D. G. Collins, M. B. Wells, Appl. Opt. 13, 534 (1974).
    [CrossRef] [PubMed]
  20. N. B. Divari, Atmos. Oceanic Phys. 3, 507 (1967).
  21. W. G. Blattner, “Light Scattering in Spherical Shell Atmospheres,” in Proceedings, International Symposium on Radiation in Atmosphere, Garmisch-Partenkirchen (Princeton Science Press, Princeton, N.J., 1976), pp. 268–270.
  22. R. Robley, Ann. Geophys. 6, No. 3, 157 (1950).
  23. G. Dietze, Meteorol. Z. 19, 5/6, 129 (1967).
  24. G. Steinhorst, Contrib. Atmos. Phys. 50, No. 4, 508 (1977).
  25. K. L. Coulson, R. L. Walraven, G. I. Weight, L. B. Soohoo, Appl. Opt. 13, 497 (1974).
    [CrossRef] [PubMed]
  26. R. L. Walraven, Sol. Energy 20, 393 (1978).
    [CrossRef]
  27. B. J. Wilkinson, Sol. Energy 27, 67 (1981).
    [CrossRef]
  28. C. Jensen, Die Himmelsstrahlung, Handbuch der Physik, Bd. 19 (Springer, Berlin, 1928), pp. 70–152.
  29. A. Gockel, “Beitrage zur Kenntnis von Farbe und Polarisation des Himmelslichtes,” Ann. Phys. Leipzig 62, No. 4, 283 (1920).
    [CrossRef]
  30. J. J. Tichanowsky, “Resultate der Messungen der Himmelspolarisation in verschiedenen Specktrumabschnitten,” Meteorol. Z. 43, 288 (1926).
  31. J. J. Tichanowski, “Die Bestimmung des optischen Anisotropiekoeffizienten der Luftmolekulen durch Messungen der Himmelspolarisation,” Phys. Z. 28, 252 (1927).
  32. C. Jensen, “Beitrage zur Photometric des Himmels,” Meteorol. Z. 14, 488 (1899).
  33. C. Jensen, “Normale, gestorte und pseudonormale Polarisations-Erscheinungen der Atmosphare,” Meteorol. Z. 49, 419 (1932).
  34. F. Ahlgrimm, “Zur Theorie der atmospharischen Polarisation,” Jb. Hamburg, Wiss. Anst. 32, 1 (1915).
  35. J. L. Soret, “Influence des surfaces d’eau sur la polarisation atmospherique et observation de deux points nuetres a droite et a gauche du Soleil,” C. R. Acad. Sci. 107, 867 (1888).
  36. C. Jensen, Die Polarisation des Himmelslichts, Handbuch der Geophysik, Bd. 8 (Berlin, 1942), pp. 527–620.
  37. Z. Sekera et al. “Investigation of Polarization of Skylight,” Final Report, Contr. AF 19(122)-239, U. California, Los Angeles (1955).
  38. G. C. Holzworth, C. R. Nagaraja Rao, J. Opt. Soc. Am. 55, 403 (1965).
    [CrossRef]
  39. K. L. Coulson, J. Quant. Spectrosc. Radiat. Transfer 11, 739 (1971).
    [CrossRef]
  40. J. V. Dave, Appl. Opt. 9, 2673 (1970).
    [CrossRef] [PubMed]
  41. G. N. Plass, G. W. Kattawar, J. Atmos. Sci. 28, 1187 (1971).
    [CrossRef]
  42. M. Kano, “Effect of a Turbid Layer on Radiation Emerging from a Planetary Atmosphere,” Ph.D. Dissertation, Department of Meteorology, U. California, Los Angeles (1964).
  43. H. Neuberger, Bull. Am. Meteorol. Soc. 31, 119 (1950).
  44. K. L. Coulson, “Atmospheric Turbidity Determinations by Skylight Measurements at the Mauna Loa Observatory,” Department of Land, Air and Water Resources, U. California, Davis Contrib. Atmos. Sci. No. 13 (1977).
  45. R. S. Fraser, J. Opt. Soc. Am. 58, 1029 (1968).
    [CrossRef]

1981

1980

1978

R. L. Walraven, Sol. Energy 20, 393 (1978).
[CrossRef]

1977

G. Steinhorst, Contrib. Atmos. Phys. 50, No. 4, 508 (1977).

1976

F. Link, M. T. Martel, Ann. Geophys. 32, 157 (1976).

1975

F. Volz, J. Geophys. Res. 80, 2643 (1975).
[CrossRef]

1974

1971

K. L. Coulson, J. Quant. Spectrosc. Radiat. Transfer 11, 739 (1971).
[CrossRef]

G. N. Plass, G. W. Kattawar, J. Atmos. Sci. 28, 1187 (1971).
[CrossRef]

1970

1969

G. M. Shah, Tellus 21, 636 (1969).
[CrossRef]

1968

1967

N. B. Divari, Atmos. Oceanic Phys. 3, 507 (1967).

G. Dietze, Meteorol. Z. 19, 5/6, 129 (1967).

1965

1957

1956

J. V. Dave, K. R. Ramanathan, Proc. Indian Acad. Sci. Sect. A 43, No. 2, 67 (1956).

J. V. Dave, Proc. Indian Acad. Sci. Sect. A 43, No. 6, 336 (1956).

1950

R. Robley, Ann. Geophys. 6, No. 3, 157 (1950).

H. Neuberger, Bull. Am. Meteorol. Soc. 31, 119 (1950).

1932

C. Jensen, “Normale, gestorte und pseudonormale Polarisations-Erscheinungen der Atmosphare,” Meteorol. Z. 49, 419 (1932).

1927

J. J. Tichanowski, “Die Bestimmung des optischen Anisotropiekoeffizienten der Luftmolekulen durch Messungen der Himmelspolarisation,” Phys. Z. 28, 252 (1927).

1926

J. J. Tichanowsky, “Resultate der Messungen der Himmelspolarisation in verschiedenen Specktrumabschnitten,” Meteorol. Z. 43, 288 (1926).

1920

A. Gockel, “Beitrage zur Kenntnis von Farbe und Polarisation des Himmelslichtes,” Ann. Phys. Leipzig 62, No. 4, 283 (1920).
[CrossRef]

1919

C. Dorno, “Himmelselligkeit, Himmelspolarisation, und Sonnenintensitat in Davos (1911 bis 1918),” Meteorol. Z. 36, 109, 181 (1919).

1915

F. Ahlgrimm, “Zur Theorie der atmospharischen Polarisation,” Jb. Hamburg, Wiss. Anst. 32, 1 (1915).

1913

H. H. Kimball, “The Effect upon Atmospheric Transparency of the Eruption of Katmai, Volcano,” Mon. Weather Rev. 41, 153 (1913).
[CrossRef]

H. H. Kimball, “The Effect of the Atmospheric Turbidity of 1912 on Solar Radiation Intensities and Skylight Polarization,” Bulletin Mt. Weather Observatory V, 295 (1913).

1903

H. H. Kimball, “Observations of Solar Radiation with the Angstrom Pyrheliometer at Asheville and Black Mountain, N.C.,” Mon. Weather Rev. 31, 320 (1903).
[CrossRef]

1899

C. Jensen, “Beitrage zur Photometric des Himmels,” Meteorol. Z. 14, 488 (1899).

1888

J. L. Soret, “Influence des surfaces d’eau sur la polarisation atmospherique et observation de deux points nuetres a droite et a gauche du Soleil,” C. R. Acad. Sci. 107, 867 (1888).

1884

A. Cornu, “Observations relative a la couronne visible actuellement autour du Soleil,” C. R. Acad. Sci. Paris 99, 488 (1884).

Ahlgrimm, F.

F. Ahlgrimm, “Zur Theorie der atmospharischen Polarisation,” Jb. Hamburg, Wiss. Anst. 32, 1 (1915).

Blattner, W. G.

W. G. Blattner, H. G. Horak, D. G. Collins, M. B. Wells, Appl. Opt. 13, 534 (1974).
[CrossRef] [PubMed]

W. G. Blattner, “Light Scattering in Spherical Shell Atmospheres,” in Proceedings, International Symposium on Radiation in Atmosphere, Garmisch-Partenkirchen (Princeton Science Press, Princeton, N.J., 1976), pp. 268–270.

Collins, D. G.

Cornu, A.

A. Cornu, “Observations relative a la couronne visible actuellement autour du Soleil,” C. R. Acad. Sci. Paris 99, 488 (1884).

Coulson, K. L.

K. L. Coulson, Appl. Opt. 20, 1516 (1981).
[CrossRef] [PubMed]

K. L. Coulson, Appl. Opt. 19, 3469 (1980).
[CrossRef] [PubMed]

K. L. Coulson, R. L. Walraven, G. I. Weight, L. B. Soohoo, Appl. Opt. 13, 497 (1974).
[CrossRef] [PubMed]

K. L. Coulson, J. Quant. Spectrosc. Radiat. Transfer 11, 739 (1971).
[CrossRef]

K. L. Coulson, “Atmospheric Turbidity Determinations by Skylight Measurements at the Mauna Loa Observatory,” Department of Land, Air and Water Resources, U. California, Davis Contrib. Atmos. Sci. No. 13 (1977).

Dave, J. V.

J. V. Dave, Appl. Opt. 9, 2673 (1970).
[CrossRef] [PubMed]

J. V. Dave, Proc. Indian Acad. Sci. Sect. A 43, No. 6, 336 (1956).

J. V. Dave, K. R. Ramanathan, Proc. Indian Acad. Sci. Sect. A 43, No. 2, 67 (1956).

Dietze, G.

G. Dietze, Meteorol. Z. 19, 5/6, 129 (1967).

Divari, N. B.

N. B. Divari, Atmos. Oceanic Phys. 3, 507 (1967).

Dorno, C.

C. Dorno, “Himmelselligkeit, Himmelspolarisation, und Sonnenintensitat in Davos (1911 bis 1918),” Meteorol. Z. 36, 109, 181 (1919).

Fraser, R. S.

Gockel, A.

A. Gockel, “Beitrage zur Kenntnis von Farbe und Polarisation des Himmelslichtes,” Ann. Phys. Leipzig 62, No. 4, 283 (1920).
[CrossRef]

Holzworth, G. C.

Horak, H. G.

Jensen, C.

C. Jensen, “Normale, gestorte und pseudonormale Polarisations-Erscheinungen der Atmosphare,” Meteorol. Z. 49, 419 (1932).

C. Jensen, “Beitrage zur Photometric des Himmels,” Meteorol. Z. 14, 488 (1899).

C. Jensen, Die Himmelsstrahlung, Handbuch der Physik, Bd. 19 (Springer, Berlin, 1928), pp. 70–152.

C. Jensen, Die Polarisation des Himmelslichts, Handbuch der Geophysik, Bd. 8 (Berlin, 1942), pp. 527–620.

Kano, M.

M. Kano, “Effect of a Turbid Layer on Radiation Emerging from a Planetary Atmosphere,” Ph.D. Dissertation, Department of Meteorology, U. California, Los Angeles (1964).

Kattawar, G. W.

G. N. Plass, G. W. Kattawar, J. Atmos. Sci. 28, 1187 (1971).
[CrossRef]

Kimball, H. H.

H. H. Kimball, “The Effect upon Atmospheric Transparency of the Eruption of Katmai, Volcano,” Mon. Weather Rev. 41, 153 (1913).
[CrossRef]

H. H. Kimball, “The Effect of the Atmospheric Turbidity of 1912 on Solar Radiation Intensities and Skylight Polarization,” Bulletin Mt. Weather Observatory V, 295 (1913).

H. H. Kimball, “Observations of Solar Radiation with the Angstrom Pyrheliometer at Asheville and Black Mountain, N.C.,” Mon. Weather Rev. 31, 320 (1903).
[CrossRef]

Link, F.

F. Link, M. T. Martel, Ann. Geophys. 32, 157 (1976).

Martel, M. T.

F. Link, M. T. Martel, Ann. Geophys. 32, 157 (1976).

Nagaraja Rao, C. R.

Neuberger, H.

H. Neuberger, Bull. Am. Meteorol. Soc. 31, 119 (1950).

Pickering, E. C.

E. C. Pickering, “A New Form of Polarimeter,” in Proceedings, American Academy of Arts and Sciences XIII, New Series (1884), pp. 294–302.

Plass, G. N.

G. N. Plass, G. W. Kattawar, J. Atmos. Sci. 28, 1187 (1971).
[CrossRef]

Ramanathan, K. R.

J. V. Dave, K. R. Ramanathan, Proc. Indian Acad. Sci. Sect. A 43, No. 2, 67 (1956).

Robley, R.

R. Robley, Ann. Geophys. 6, No. 3, 157 (1950).

Rozenberg, G. V.

G. V. Rozenberg, Twilight: A Study in Atmospheric Optics, A. E. Stibb, Translator (Plenum, New York, 1966).

Sekera, Z.

Z. Sekera, J. Opt. Soc. Am. 47, 484 (1957).
[CrossRef]

Z. Sekera, Polarization of Skylight, Compedium of Meteorology (American Meteorological Society, Boston, 1950), pp. 79–90.

Z. Sekera et al. “Investigation of Polarization of Skylight,” Final Report, Contr. AF 19(122)-239, U. California, Los Angeles (1955).

Shah, G. M.

G. M. Shah, Tellus 21, 636 (1969).
[CrossRef]

Soohoo, L. B.

Soret, J. L.

J. L. Soret, “Influence des surfaces d’eau sur la polarisation atmospherique et observation de deux points nuetres a droite et a gauche du Soleil,” C. R. Acad. Sci. 107, 867 (1888).

Steinhorst, G.

G. Steinhorst, Contrib. Atmos. Phys. 50, No. 4, 508 (1977).

G. Steinhorst, Appl. Opt. 13, 219 (1974).
[CrossRef]

Tichanowski, J. J.

J. J. Tichanowski, “Die Bestimmung des optischen Anisotropiekoeffizienten der Luftmolekulen durch Messungen der Himmelspolarisation,” Phys. Z. 28, 252 (1927).

Tichanowsky, J. J.

J. J. Tichanowsky, “Resultate der Messungen der Himmelspolarisation in verschiedenen Specktrumabschnitten,” Meteorol. Z. 43, 288 (1926).

Volz, F.

F. Volz, J. Geophys. Res. 80, 2643 (1975).
[CrossRef]

F. Volz, J. Geophys. Res. 75, 5185 (1970).
[CrossRef]

Walraven, R. L.

Weight, G. I.

Wells, M. B.

Wilkinson, B. J.

B. J. Wilkinson, Sol. Energy 27, 67 (1981).
[CrossRef]

Ann. Geophys.

F. Link, M. T. Martel, Ann. Geophys. 32, 157 (1976).

R. Robley, Ann. Geophys. 6, No. 3, 157 (1950).

Ann. Phys. Leipzig

A. Gockel, “Beitrage zur Kenntnis von Farbe und Polarisation des Himmelslichtes,” Ann. Phys. Leipzig 62, No. 4, 283 (1920).
[CrossRef]

Appl. Opt.

Atmos. Oceanic Phys.

N. B. Divari, Atmos. Oceanic Phys. 3, 507 (1967).

Bull. Am. Meteorol. Soc.

H. Neuberger, Bull. Am. Meteorol. Soc. 31, 119 (1950).

Bulletin Mt. Weather Observatory

H. H. Kimball, “The Effect of the Atmospheric Turbidity of 1912 on Solar Radiation Intensities and Skylight Polarization,” Bulletin Mt. Weather Observatory V, 295 (1913).

C. R. Acad. Sci.

J. L. Soret, “Influence des surfaces d’eau sur la polarisation atmospherique et observation de deux points nuetres a droite et a gauche du Soleil,” C. R. Acad. Sci. 107, 867 (1888).

C. R. Acad. Sci. Paris

A. Cornu, “Observations relative a la couronne visible actuellement autour du Soleil,” C. R. Acad. Sci. Paris 99, 488 (1884).

Contrib. Atmos. Phys.

G. Steinhorst, Contrib. Atmos. Phys. 50, No. 4, 508 (1977).

J. Atmos. Sci.

G. N. Plass, G. W. Kattawar, J. Atmos. Sci. 28, 1187 (1971).
[CrossRef]

J. Geophys. Res.

F. Volz, J. Geophys. Res. 75, 5185 (1970).
[CrossRef]

F. Volz, J. Geophys. Res. 80, 2643 (1975).
[CrossRef]

J. Opt. Soc. Am.

J. Quant. Spectrosc. Radiat. Transfer

K. L. Coulson, J. Quant. Spectrosc. Radiat. Transfer 11, 739 (1971).
[CrossRef]

Jb. Hamburg, Wiss. Anst.

F. Ahlgrimm, “Zur Theorie der atmospharischen Polarisation,” Jb. Hamburg, Wiss. Anst. 32, 1 (1915).

Meteorol. Z.

J. J. Tichanowsky, “Resultate der Messungen der Himmelspolarisation in verschiedenen Specktrumabschnitten,” Meteorol. Z. 43, 288 (1926).

C. Jensen, “Beitrage zur Photometric des Himmels,” Meteorol. Z. 14, 488 (1899).

C. Jensen, “Normale, gestorte und pseudonormale Polarisations-Erscheinungen der Atmosphare,” Meteorol. Z. 49, 419 (1932).

G. Dietze, Meteorol. Z. 19, 5/6, 129 (1967).

C. Dorno, “Himmelselligkeit, Himmelspolarisation, und Sonnenintensitat in Davos (1911 bis 1918),” Meteorol. Z. 36, 109, 181 (1919).

Mon. Weather Rev.

H. H. Kimball, “Observations of Solar Radiation with the Angstrom Pyrheliometer at Asheville and Black Mountain, N.C.,” Mon. Weather Rev. 31, 320 (1903).
[CrossRef]

H. H. Kimball, “The Effect upon Atmospheric Transparency of the Eruption of Katmai, Volcano,” Mon. Weather Rev. 41, 153 (1913).
[CrossRef]

Phys. Z.

J. J. Tichanowski, “Die Bestimmung des optischen Anisotropiekoeffizienten der Luftmolekulen durch Messungen der Himmelspolarisation,” Phys. Z. 28, 252 (1927).

Proc. Indian Acad. Sci. Sect. A

J. V. Dave, K. R. Ramanathan, Proc. Indian Acad. Sci. Sect. A 43, No. 2, 67 (1956).

J. V. Dave, Proc. Indian Acad. Sci. Sect. A 43, No. 6, 336 (1956).

Sol. Energy

R. L. Walraven, Sol. Energy 20, 393 (1978).
[CrossRef]

B. J. Wilkinson, Sol. Energy 27, 67 (1981).
[CrossRef]

Tellus

G. M. Shah, Tellus 21, 636 (1969).
[CrossRef]

Other

G. V. Rozenberg, Twilight: A Study in Atmospheric Optics, A. E. Stibb, Translator (Plenum, New York, 1966).

Z. Sekera, Polarization of Skylight, Compedium of Meteorology (American Meteorological Society, Boston, 1950), pp. 79–90.

E. C. Pickering, “A New Form of Polarimeter,” in Proceedings, American Academy of Arts and Sciences XIII, New Series (1884), pp. 294–302.

C. Jensen, Die Himmelsstrahlung, Handbuch der Physik, Bd. 19 (Springer, Berlin, 1928), pp. 70–152.

W. G. Blattner, “Light Scattering in Spherical Shell Atmospheres,” in Proceedings, International Symposium on Radiation in Atmosphere, Garmisch-Partenkirchen (Princeton Science Press, Princeton, N.J., 1976), pp. 268–270.

C. Jensen, Die Polarisation des Himmelslichts, Handbuch der Geophysik, Bd. 8 (Berlin, 1942), pp. 527–620.

Z. Sekera et al. “Investigation of Polarization of Skylight,” Final Report, Contr. AF 19(122)-239, U. California, Los Angeles (1955).

M. Kano, “Effect of a Turbid Layer on Radiation Emerging from a Planetary Atmosphere,” Ph.D. Dissertation, Department of Meteorology, U. California, Los Angeles (1964).

K. L. Coulson, “Atmospheric Turbidity Determinations by Skylight Measurements at the Mauna Loa Observatory,” Department of Land, Air and Water Resources, U. California, Davis Contrib. Atmos. Sci. No. 13 (1977).

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Figures (15)

Fig. 1
Fig. 1

Profiles of the aerosol-to-Rayleigh backscatter ratio as measured with a ruby lidar on two different dates at the Mauna Loa Observatory. The curve for 9 Apr. is the first measurement of the El Chichon volcanic cloud, and that of 3 Aug. is for the more mature cloud after it had become stabilized.

Fig. 2
Fig. 2

Schematic diagram showing the position in the atmosphere of the direct solar ray which is tangent to the earth’s surface for two different depression angles of the sun. The shaded portion of the cone represents the portion of the illuminated atmosphere which is viewed by the polarizing radiometer.

Fig. 3
Fig. 3

Degree of polarization of skylight as a function of sun elevation at a wavelength of 0.70 μm taken in the zenith direction 13 July 1982 at the Mauna Loa Observatory. The points are the individual measurements, and the solid curve is fitted by eye to the points. The dashed curve represents the altitude of the earth’s shadow as a function of sun elevation during the period of twilight.

Fig. 4
Fig. 4

Degree of polarization of the zenith skylight at λ = 0.70 μm as a function of sun elevation as observed at the Mauna Loa Observatory on three different days at the time of the volcanic cloud in the stratosphere.

Fig. 5
Fig. 5

Aerosol-to-Rayleigh backscatter profile as observed at the Mauna Loa Observatory on the same days as the polarization measurements shown in Fig. 4.

Fig. 6
Fig. 6

Degree of polarization of zenith skylight as a function of sun elevation at the Mauna Loa Observatory 13 July 1982 compared with that observed by various authors in the past.

Fig. 7
Fig. 7

Backscatter profile as observed at the Mauna Loa Observatory on three different days during the transitional phase of the volcanic cloud.

Fig. 8
Fig. 8

Degree of polarization of zenith skylight at λ = 0.70 μm as observed in different conditions at the Mauna Loa Observatory. The top curve is for very clear conditions in 1977 before the eruption of the El Chichon volcano. The curve of 11 Apr. is for the cloud in its transitional phase, and that of 14 May is for the cloud in its densest stage over Hawaii. The cloud had only two thin layers, which were located in the 20–25-km range, on 23 Apr.

Fig. 9
Fig. 9

Degree of polarization of zenith skylight as a function of sun elevation at λ = 0.70 μm as observed on two different days at the Mauna Loa Observatory compared with that observed by various authors in the past.

Fig. 10
Fig. 10

Backscatter profile as observed at the Mauna Loa Observatory of the volcanic cloud at its densent phase (14 May) compared with that for the cloud after it had become stabilized (17 Aug.).

Fig. 11
Fig. 11

Degree of polarization of zenith skylight at λ = 0.70 μm as a function of sun elevation for four different days after the volcanic cloud had become stabilized. A curve for clear atmospheric conditions at the Mauna Loa Observatory in 1977 is included for comparison.

Fig. 12
Fig. 12

Distribution of the degree of polarization through the plane of the sun’s vertical at λ = 0.70 μm as observed at the Mauna Loa Observatory 27 July 1982 for the various sun elevations indicated. The top curve was measured in the clear atmospheric conditions of 1977 at a sun elevation of 3°.

Fig. 13
Fig. 13

Distribution of the degree of polarization through the plane of the sun’s vertical at λ = 0.70 μm as observed at the Mauna Loa Observatory 27 July 1982 at the higher sun elevations. The upper curves are for the clear atmospheric conditions in 1977.

Fig. 14
Fig. 14

Angular distance of the Arago point from the antisun as a function of sun elevation as observed at the Mauna Loa Observatory on three different days of 1982. The annual mean values from Jensen’s observations in normal atmospheric conditions and after the eruption of Mt. Katmai in 1912 are given for comparison.

Fig. 15
Fig. 15

Angular distance of the Babinet point from the sun as a function of sun elevation as observed at the Mauna Loa Observatory on three different days in 1982. The annual mean values from Jensen’s observations in normal atmospheric conditions and after the eruption of Mt. Katmai in 1912 are given for comparison.

Tables (1)

Tables Icon

Table I Difference Between A-distance at H = 4.5° and that at the Presunrise Minimum, According to Data of Jensen33 and as Measured at Mauna Loa on Various Dates in 1982; Note that the Data of 22 Aug. are for λ = 0.80 μm

Metrics