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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 PMC Particle Size from 14 Years of HALOE Observations Mark Hervig GATS Inc.

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 Halogen Occultation Experiment (HALOE) Solar Occultation observations in both hemispheres Operated from 11 October 1991 - 21 November 2005 Profile retrievals: H 2 O, O 3, NO, CH 4 PMC extinction at 5 wavelengths (2.45, 3.40, 3.46, 5.26, 6.26 m) Temperature 1.8 km vertical resolution This work uses HALOE “Vpmc” data

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 HALOE PMC Measurements HALOE multi-wavelength extinctions are consistent with modeled PMC spectra 60-70 N Mie theory and a lognormal size distribution with r m = 50 nm, = 1.4 Ice refractive indices measured at various temperatures

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 HALOE PMC Size Information The HALOE 2.45 m PMC measurement is 50% scattering The longer wavelength PMC measurements are pure absorption Absorption - scattering contrast yields PMC size information Median radius can be determined if size distribution width is fixed

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 Modeling PMC Optics The extinction calculations are sensitive to: Ice refractive index 266K: Waren et al., 1984 (0.05 - 2000 m) 163K: Toon et al., 1994 (1.4 - 20 m) 130-210K: Clapp et al., 1995 (2.5 - 12.5 m) 100K: Bertie et al., 1969 (1.2 - 333 m) Particle shape Spheres (Mie theory) Non-spherical (T-matrix) Size distribution Lognormal: total conc. (N), median radius (r m ), width ( ) Gausian: total conc. (N), median radius (r m ), width ( r)

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 Spheres vs. Spheroids Oblate and prolate spheroids were considered in these results Random orientation Aspect ratios (AR) from 0.2 to 5 Cross section differences less than 12% compared to spheres

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 PMC Size Distributions Lognormal has precedence CARMA suggests Gaussian Comparison of lognormal and Gaussian size distributions Both use r m = 50 nm Typical widths IR extinction is proportional to volume Volume weighted mean radii: Lognormal: 75 nm Gaussian: 58 nm

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 PMC Median Radii Determined from HALOE Median radius can be determined from measured extinction ratios R = ( ) / (2.45 m) if the distribution width is fixed. We can use = 3.40, 3.46, 5.26, or 6.26 m, but (3.40) has the highest signal-to-noise Examine sensitivity to: Particle shape Size distribution Refractive index

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 HALOE PMC and Background Signals The background is less than 10% for > 2.45 m At 2.45 m, the background is roughly 50% of the PMC signal Background was subtracted from all HALOE PMC measurements

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 PMC Radii Results Median radii profiles were determined from yearly averaged extinctions. 60 - 70 N, -20 to 50 days from solstice The calculations used two sets of assumptions: Spheres - lognormal ( = 1.3, 1.5, 1.7) Spheroid (AR=0.2) - Gaussian ( r = 10, 15, 20 nm)

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 PMC Radius Time Series The median value of r m for all altitudes in each annual profile Results based on sphere - lognormal and spheroid - gaussian models Grand Averages: Spheroid - Gaussian: 141 nm Sphere - lognormal: 62 nm

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 Mission average median radius profiles Average of yearly profiles from 1993 - 2005 Inversions assume either: 1.Spheres - lognormal ( = 1.3, 1.5, 1.7) r m = 70 34 nm (83 km) Vertical mean r m = 40 28 nm 2.Spheroid (AR=0.2) - Gaussian ( r = 10, 15, 20 nm) r m = 140 39 nm (83 km) Vertical mean r m = 79 58 nm and use ice refractive indices for 163K. Error bars indicate the variation in r m over time and for changing distribution width

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 Comparisons with CARMA Model Results Particle radii from CARMA are perhaps most sensitive to H 2 O A quick survey of H 2 O in the polar summer mesosphere: SourceApproximate 83 km Mixing Ratio (ppmv) Korner & Sonnemann (model)3 CHEM2D model (Siskind)3 ALOMAR 22 GHz (Seele)3 - 4 Odin 557 GHz (Lassow)5 HALOE (Hervig)5 - 7 ACE4 - 7 OSIRIS Limb OH (Gattinger)1 - 7

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 Water Vapor and PMCs There is evidence for a little more H 2 O in the polar summer mesosphere How does this affect PMCs? HALOE - ACE H 2 O Comparisons at 66 N during summer

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 HALOE Radii Compared to CARMA CARMA model runs using two sources of H 2 O: CHEM2D: 3 ppmv (83 km) CARMA r m : 20 - 70 nm (83 km) HALOE: 6 ppmv (83 km) CARMA r m : 70 - 140 nm (83 km) CARMA notes: FS Temperatures, CHEM2D vertical winds, averages of 24 - 96 hr cloud age, r m is the number weighted mean, courtesy Mike Stevens (NRL) HALOE results as before, averages from 1993 - 2005 Inversions assuming either: Spheres - lognormal Spheroid (AR=0.2) - gaussian

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 The Range of Observed PMC Extinctions The HALOE PMC detection threshold is 3.40 m extinction > 2 10 -6 km -1 HALOE extinctions predicted from CARMA results for H 2 O from: CHEM2D: 3 ppmv at 83 km, does not cover the HALOE range HALOE: 6 ppmv at 83 km, easily covers the HALOE observations Notes: HALOE PMC frequency for 60- 70 N and -10 to 40 days from solstice is 23%. The corresponding SME PMC frequency is about 33% (1.4 times as many). Stevens et al. [2005] estimated that HALOE detects about 50% of the PMC mass that is present. 60-70 N

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Mark Hervig, CAWSES Ice Layer Workshop, Kuehlungsborn, May 15, 2006 Summary HALOE PMC median radii, mission averages, 60 - 70 N Spheres - lognormal: 70 nm at 83 km, 40 nm vertical mean Spheroid - Gaussian: 140 nm at 83 km, 79 nm vertical mean The Gaussian size distribution requires larger median radii. Spheroids lead to slightly larger radii, but this is a small effect. HALOE PMC measurements are consistent with HALOE H 2 O CARMA results using HALOE H 2 O can reproduce HALOE PMC radii HALOE extinction magnitude

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