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SAGE III Aerosol Studies: Size Distribution Retrievals and Validation

SAGE III Aerosol Studies: Size Distribution Retrievals and Validation. Mark Hervig GATS Inc. Planned Investigations. SAGE III Validation Studies: Addressing stratospheric aerosols and cirrus Comparisons with: HALOE, balloon-borne OPCs, and SAGE II

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SAGE III Aerosol Studies: Size Distribution Retrievals and Validation

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  1. SAGE III AerosolStudies: Size Distribution Retrievals and Validation Mark Hervig GATS Inc.

  2. Planned Investigations SAGE III Validation Studies: Addressing stratospheric aerosols and cirrus Comparisons with: HALOE, balloon-borne OPCs, and SAGE II Stratospheric Aerosol Size Distribution Retrievals

  3. SAGE III Aerosol Validation Comparisons with HALOE HALOE measures aerosol extinction profiles at 4 IR wavelengths 2.45, 3.40, 3.46, and 5.26 m size distributions are retrieved from stratospheric measurements compare size distribution, surface area, etc… calculate extinction at SAGE wavelengths using the HALOE size distributions 224 coincidences during 6 months in 2002 (176 solar, 48 lunar)

  4. Comparisons with balloon-borne optical particle counters (OPCs) OPCs measure size distribution profiles compare size distribution, surface area, etc… compute extinction at SAGE wavelengths using the OPC size distributions Terry Deshler collaborating (University of Wyoming)

  5. Example comparison between SAGE III and OPC over Laramie 40N, summer 2002 Profiles over Laramie Extinction spectra at 21 km altitude Normalized spectra, 21 km

  6. Extinction profile comparisons SAGE II and HALOE 281 coincident measurements near 41N, 1991-1998 Average separations: 12.1 hours 0.8 latitude 8.0 longitude

  7. Extinction time series comparisons SAGE II, HALOE, and OPCs Measurements over Laramie Non-coincident measurements within the same location

  8. Surface area time series comparisons SAGE II and HALOE Over the equator Non-coincident measurements within the same location

  9. SAGE III Cirrus Validation Compare SAGE III and HALOE cirrus measurements Using very close coincidences: Cloud presence (yes/no) Cloud altitude others? optical depth, effective radius, volume Statistical comparisons: occurrence frequency vs. space, time Example comparison of SAGE II and HALOE cloud top heights 9 coincidences, average separation: 3 minutes time and 61 km distance

  10. SAGE III Aerosol Size Distribution Retrievals Retrieve aerosol size distributions from extinction at 8 (9) wavelengths Assume lognormal distributions, 3 parameters: total concentration, median radius, and distribution width Begin with single mode, possible bimode (6 parameters) Step 1: Find distribution shape (median radius and width) using extinction ratios Step 2: Find concentration by adjusting simulated extinction to measurement at one wavelength

  11. Simulated SAGE III Size Distribution Retrievals volcanic aerosols background aerosols

  12. Example retrieval using SAGE III measurements 21 km altitude, 40N, summer 2002 SAGE III size distribution retrieval Comparison with OPC measurements

  13. Summary SAGE III Validation: Stratospheric aerosol extinction, surface area, size distribution Cirrus altitude, occurrence frequency… Comparisons with HALOE, OPCs, SAGE II SAGE III Aerosol Size Distribution Retrievals: Infer lognormal size distributions for stratospheric aerosols Make results and software available on the web

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