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Measurement-based Aerosol Radiative Effects within the Context of CCSP and IPCC

Measurement-based Aerosol Radiative Effects within the Context of CCSP and IPCC. Hongbin Yu, Yoram Kaufman February 10, 2006. Background.  Presently the IPCC assessments are largely model-based (the models are evaluated using satellite and surface measurements).

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Measurement-based Aerosol Radiative Effects within the Context of CCSP and IPCC

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  1. Measurement-based Aerosol Radiative Effects within the Context of CCSP and IPCC Hongbin Yu, Yoram Kaufman February 10, 2006

  2. Background •  Presently the IPCC assessments are largely model-based (the models are evaluated using satellite and surface measurements). • In recent years, a great deal of effort has gone into improving measurements and data sets: • It is feasible to shift the estimate of aerosol radiative effects fromlargely model-basedtoincreasingly measurement-based. MISR

  3. CCSP • CCSP, an interagency program, was established to coordinate and integrate scientific research on global change & climate change. • CCSP is generating 21 synthesis & assessment products to (1) support policymaking & adaptive management; and (2) contribute to IPCC FAR. • Product 2.3:Aerosol Properties and Their Impacts on Climate (lead by NASA, Phil DeCola) • In-situ measurements of aerosol properties and direct forcing (Bates et al.) • Satellite measurements of aerosol direct effect(Kaufman, Chin, Feingold) • Aerosol indirect effects (Penner et al.)

  4. Specific Goals • Assess the global aerosol distribution and direct radiative effect using satellites supplemented by chemical transport models. • Assess the anthropogenic component, using satellite data and models. • Evaluate these assessments against surface network data and field experiments; and compare them to model estimates. “A review of measurement-based assessments of the aerosol direct effect and forcing”, accepted to Atmospheric Chemistry and Physics

  5. natural + anthrop. 11 observations(MODIS, CERES, MISR, POLDER, SeaWiFS, MO_MI_GO, ……) 5 models (GOCART, GISS, ……) M/O=0.64 M/O=0.58 Possible reasons for the discrepancies:  Optical depth(cloud contamination in satellites; low biases of models --- sources, humidification, …...) Large discrepancies exist in Forcing Efficiency (forcing normalized by optical depth), which may result from model biases, such as high absorption, weak backscattering (large size), too bright surface.

  6. Regional Assessments Measurements Models Remer & Kaufman, Atmos. Chem. Phys., 6, 237-253, 2006 OCEAN, TOA

  7. MODIS measured aerosol size parameters can be used to distinguish anthropogenic aerosols from natural aerosols Natural + Anthropogenic total Anthropogenic Anthrop. Over ocean, the anthropogenic contribution to MODIS AOD is about 21%.MODIS and models are consistent in anthropogenic AOD. (Kaufman et al., GRL, 2005)

  8. Clear-sky DCF =  x ff xfaf x Ea Anthrop. fraction in fine- mode Forcing efficiency Fine-mode fraction Using as many measurements as possible, we estimate the TOA forcing of -1.3 ± 0.8 W/m2for cloud-free conditions (LAND + OCEAN). 9 models give -0.6 W/m2(Michael Schulz)

  9. Estimating the DIRECT FORCING in the presence of clouds: We need GLAS and Calipso!!!! And to know aerosol absorption better!!

  10. Aerosol-Cloud Interactions as Inferred from MODIS Measurements • Kaufman, Y. J., I. Koren, L. A. Remer, D. Rosenfeld, and Y. Rudich, 2005: The Effect of Smoke, Dust and Pollution Aerosol on Shallow Cloud Development Over the Atlantic Ocean,Proc. Nat. Acad. Sci.,102(32), pp.11207-11212. • Koren, I., Y. J. Kaufman, D. Rosenfeld, L. A. Remer, and Y. Rudich, 2005: Aerosol Invigoration and Restructuring of Atlantic Convective Clouds.Geophys. Res. Lett., 32, LI4828, doi: 10.1029/2005GL023187. adding new observational evidence for aerosol impacts on cloudsin IPCC FAR.

  11. Dust Total TOA Solar Forcing = Cloud modifications (fraction, Nc, LWP) + Direct effect

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