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I.-J. Choi, T. Iguchi, T. Nakajima, and S.-C. Yoon

University Allied Workshop July 1-3 th , 2008. Aerosol-Cloud Interaction over East Asia using Ground-based Measurement and Cloud Microphysical Model. I.-J. Choi, T. Iguchi, T. Nakajima, and S.-C. Yoon.

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I.-J. Choi, T. Iguchi, T. Nakajima, and S.-C. Yoon

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  1. University Allied Workshop July 1-3th , 2008 Aerosol-Cloud Interaction over East Asia using Ground-based Measurement and Cloud Microphysical Model I.-J. Choi, T. Iguchi, T. Nakajima, and S.-C. Yoon School of Earth and Environmental Sciences Seoul National University, KOREA

  2. Background • Aerosol indirect effect : Cloud albedo effect & Cloud lifetime effect • The aerosol indirect effect , which requires proper understanding not only of what portion of aerosols can act as CCN but also of the atmospheric dynamics that determine cloud development, is considered to be the greatest source of uncertainties in climate prediction. [IPCC, 2007]

  3. Cloud Optical/ Microphysical Properties Aerosol Size /Chemical Composition Cloud Droplet Number/Size Objectives of This Study • A major challenge is to determine the ability of aerosols to act as cloud condensation nuclei (CCN) at water vapor supersaturation S that are relevant for atmospheric conditions [Dusek et al., 2007]. In this study, we focus on … CCN activity of aerosols from surface-based measurements during the ABC-EAREX2005 Aerosol-cloud interaction over East China Sea region using cloud microphysical model

  4. Bin-type Cloud Microphysical Model • Bin cloud microphysics in HUCM is combined with a 3-D non-hydrostatic modeling system, the Non-Hydrostatic Model developed by JMA-MRI. NHM • 3-D mesoscale model • Bulk cloud microphysics HUCM • 2-D cloud model • Bin cloud microphysics [Saito et al., 2006] [Khain et al., 2000] NHM+ HUCM • 3-D mesoscale cloud-resolving model • Bin method cloud microphysics • Nesting Procedure • Mstrn-X for radiation process [Iguchi et al., 2008]

  5. Methodology PREPARING MODEL INPUT Aerosol bulk number concentration from SPRINTARS (sulfate, seasalt, dust, carbonaceous, and BC) Meteorological Parameters from JMA-MANAL and NCEP Topography Data from GTOPO30 ANALYSIS OF MEASUREMENT DATASET Aerosol size distribution from Ground-based measurement Hygroscopicity parameters related to chemical composition MODEL SIMULATION Aerosol-CCN nucleation with new aerosol information Aerosol loading vs. Cloud microphysical parameters

  6. Ground-based Measurement dataset • Dataset during the ABC-EAREX2005 campaign at Gosan ABC supersite, Korea (126.17 oE, 33.29 oN, 72 m) 0.5 ~ 20 ㎛ APS Detectable Size Range 0.01 ~ 3 ㎛ CPC 0.01 ~ 0.4 ㎛ SMPS 0.001 0.01 0.11 10 [㎛]

  7. Designation of each aerosol dominant case Mass concentrations [Unit : μg m-3] SC SULFATE + CARBONACEOUS DU DUST SS SEA SALT

  8. CN-CCN Relation All SC DU SS

  9. Aerosol Size Distribution dN/dlogDp dV/dlogDp +++++++ SULFATE + CARBONACEOUS DUST SEASALT

  10. Aerosol-CCN Nucleation • Aerosol bulk number concentrations (5 species : sulfate, dust, seasalt, BC, and carbonaceous aerosol) from SPRINTARS are used to provide more realistic and inhomogeneous initial and boundary conditions [Iguchi et al., 2008]. Size Distribution Aerosol size distributions for 5 aerosol types are determined based on the ground-based measurement, SMPS and APS, which shows multi-mode log-normal distribution. Chemical Composition The treatment of various aerosol species involves only the hygroscopicity parameter (solute effect part in the Kölher equation). : Van’t Hoff factor : osmotic coefficient : soluble mass fraction : CN/water molecular weight : CN/water droplet density [Abdul-Razzak and Ghan, 2000, Ghan et al., 2001]

  11. CCN and Seven hydrometeors in NHM+HUCM Radius [㎛] 1000 100 10 0.01 0.1 1 0.001 17 size bins CCN water cloud 33 size bins DROPLET • Cloud Microphysical • Processes • Nucleation • Condensation • Deposition • Coalescence • Evaporation • Sublimation • Droplet freezing • Melting COLUMN ice crystal PLATE DENDRITE ice cloud SNOWFLAKE GRAUPEL HAIL

  12. Setup of Numerical Experiment • 302 x 302 x 40 grid • 5 km horizontal resolution • 40 ~ 1120 m vertical resolution • 2005. 3. 17. 00 UTC ~ 18 UTC : ABC-EAREX2005 SC1 period • Simulation time : 18 hours • Time step : 20 second Model Domain MODIS RGB Image Synoptic Chart

  13. Aerosol & CN Number Concentration

  14. Cloud Microphysical Properties Effective Radius [μm] Liquid Water Path [g m-2] Cloud Optical Thickness

  15. Aerosol-Cloud Interaction Liquid Water Path [g m-2] Effective Radius [um] Cloud Optical Thickness Column aerosol number concentration [cm-3] • The more aerosol number concentration, the smaller cloud effective radius. • No increasing/decreasing trend in aerosol number concentration vs. Liquid water path.

  16. Summary and Conclusion • Ground-based measurement dataset during the ABC-EAREX2005 were analyzed to investigate aerosol-CCN relationship for different aerosol species. Sulfate and carbonaceous aerosols are easily activated to CCN, but dust and seasalt aerosols are hard to act as CCN. • Aerosol size distribution from ground-based measurements showed multi-mode log-normal size distribution for all aerosol species, which was used in the model to provide more realistic values. • From NHMHUCM simulation considering various aerosol species , the cloud albedo effect related with effective radius was very distinct (column aerosol loading vs. effective radius ~ decreasing trend), but cloud lifetime effect related with liquid water path was not clear in this study. • Further investigations are needed to get a better understanding of cloud lifetime effect over East Asia region.

  17. Thank You !

  18. Definitions of CCN and CN • CCN : aerosol particles which are capable of initiating drop formation at the observed low supersaturations are called cloud condensation nuclei (CCN). • All AP are eventually able to initiate drops provided that the supersaturation of the water vapor in their environment is high enough • Therefore, in air the total number of aerosol particles per unit volume is often measured in terms of the total number of drops per unit volume observed in a cloud chamber at supersaturations of several hundred percent. • The aerosol particle concentration determined in this fashion is then simply called the concentration of condensation nuclei. (CN) Pruppacher and Klett (1978)

  19. Determination of chemical component • Aerosol mass concentrations are calculated by the treatment of Fukugawa et al. (2006) and Ohta and Okita (1990) from inorganic ionic components measured by PILS-IC. [Sea Salt]= [Sea Salt Cation] + [Sea Salt Anion] [Sea Salt Cation]= (100/83.7) x [Na+] [Sea Salt Anion]= Cl- + Sea Salt SO42- [Sea Salt SO42-]= 0.252 x [Na+] [Non Sea Salt Sulfate]= [SO42-] – [Sea Salt SO42-] [Soil Dust]= (100/8.6) x [Al ] [Al ] = 0.896 x [Non Sea Salt Ca2+] [Non Sea Salt Ca2+]= [Ca2+] – (0.4/10.556) x [Na+] Sea Salt Sulfate Soil Dust

  20. Aerosol Mass Ratio of Designated Cases (PM2.5)

  21. D. Goto (2007)

  22. Data Merge of SMPS and APS measurements • Relationship between mobility diameter (dm) for SMPS and aerodynamic diameter (da) for APS [Hand and Kreidenweis, 2002] • The Cunningham correction factor for solids under normal temperature and pressure (NTP) is defined as follows (Allen and Raabe, 1982, 1985; Rader, 1990)

  23. Size Distribution in original NHMHUCM • Bulk number concentrations of hygroscopic aerosol (sulfate, seasalt, OC) from SPRINTARS are utilized to calculate their size distribution function. • For sulfate and OC, lognormal size distribution is assumed. • For seasalt aerosol, power law is assumed.

  24. CN Size Distribution in current NHMHUCM SU (N=1000 cm-3) OC (N=2500 cm-3) SS (N=30cm-3) CN

  25. Aerosol-CCN Nucleation Process (Original) • Based on the Köhler theory, the supersaturation around the droplet is calculated by the following equation [Pruppacher and Klett, 1997] Sw : supersaturation over water rw/cn : droplet/aerosol radius T : temperature ν : Van’t Hoff factor ρcn : CN density • Assuming the uniform composition of aerosol, critical radius is described by the followings : All CN of which radius is larger than the critical radius is converted to CCN.

  26. Aerosol-CCN Nucleation – Chemical composition • The treatment of various aerosol species involves only the hygroscopicity parameter (solute effect part in the Kölher equation), which is defined as the following [Abdul-Razzak and Ghan, 2000]. : Van’t Hoff factor : osmotic coefficient : soluble mass fraction : CN/water molecular weight : CN/water droplet density [Ghan et al., 2001; Nishikawa et al., 1991]

  27. Definition of Cloud microphysical parameters Effective Radius Liquid Water Path Cloud Optical Thickness

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