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Satoshi Suzuki, Shinta Seto, and Taikan Oki

Relationship Between Cloud Droplet Effective Radius and Cloud Top Height for Deep Convective Clouds in CloudSat Data Product. Satoshi Suzuki, Shinta Seto, and Taikan Oki Institute of Industrial Science, the University of Tokyo. Background: Aerosol Convection Invigoration Effect Hypothesis.

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Satoshi Suzuki, Shinta Seto, and Taikan Oki

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  1. Relationship Between Cloud Droplet Effective Radius and Cloud Top Height for Deep Convective Clouds in CloudSat Data Product Satoshi Suzuki, Shinta Seto, and Taikan Oki Institute of Industrial Science, the University of Tokyo

  2. Background: Aerosol Convection Invigoration Effect Hypothesis Rosenfeld et al. (2008)

  3. Background: Aerosol Convection Invigoration Effect Hypothesis Aerosol concentration Ex) Korenet al. (2010) Ex) Nakajima et al. (2001) Cloud droplet radius Cloud top height Purpose: Examine Cloud droplet radius - Cloud top height relationship

  4. Data: CloudSat 2B-CWC-RVOD (Dec. 2006-Feb. 2007) Cloud top height: highest bin with value Conditions of the clouds to be analyzed 50km (Independent data) Cloud Top Height >5000m Cloud Base <1500m Cloud droplet effective radius (liquid only) Cloud droplet effective radius↓ Cloud top height↑ Convection↑

  5. Geographical Distribution of Clouds Matching the Condition Cloud top height [m]

  6. Average profile for each cloud top height

  7. Average profile for each cloud top height 7

  8. Cloud droplet effective radius - Cloud top height relationship Cloud droplet effective radius↓ Cloud top height↑

  9. Radar Reflectivity Factor and Cloud Top Height Radar reflectivity is lower for lower clouds => correct attenuation calculation is needed for the negative relationship to appear 9

  10. Droplet Radius – Cloud Top Height Relationship for clouds without precipitation flag (dBZe<-15) Significant negative correlation still appears 10

  11. Variation of the relationship by surface temperature Rosenfeld et al. (2008) suggested freezing causes clouds to become invigorated. Invigoration No Invigoration Low Invigoration Freezing Level High Temperature Low Temperature

  12. Variation of the relationship by surface temperature To see the effect of freezing, lower clouds are also included in the analysis. 50km (Independent data) Cloud top >5000m 　　⇓ >1600m Freezing Level Cloud top height Cloud base < 1500m 　　⇓ <1000m Cloud droplet effective radius

  13. Cloud droplet effective radius - Cloud top height relationship Lower clouds do not show negative correlation

  14. Surface temperature 30 – 40 deg C No negative correlation

  15. Surface Temperature 10 – 20 deg C Freezing Level Negative correlation appears in clouds with lower cloud top heights

  16. Surface Temperature 0 – 10 deg C Freezing Level By moist adiabatic lapse rate, in most cases, altitude of 2000m should be below 0 deg C A mechanism other than freezing?

  17. Another Hypothesis by Lee et al. (2010) Higher aerosol concentration Smaller Cloud droplet effective radius (Larger surface area) Larger Evaporation rate Stronger downdraft, gust front Stronger Convection

  18. In clouds with cloud top heights lower than 3000 m, gust fronts do not form?

  19. Conclusions • By analyzing CloudSat 2B-CWC-RVOD product, negative correlation is found between cloud droplet effective radius and cloud top height for deep clouds • The negative correlation supports the hypothesis that aerosols are invigorating deep clouds • Negative correlation do not appear for clouds with low cloud top heights • When surface temperature is high, the threshold altitudes for negative correlation becomes higher • Attenuation calculation has a large role in determining the sign of the relationship • Analysis of clouds with low reflectivity only also shows the relationship is significantly negative

  20. Thank you for your kind attention! The authors would like to acknowledge the CloudSat Data Processing Center at CIRA/Colorado State University for providing data products, Environment Research and Technology Development Fund (S-8) of the Ministry of the Environment, Japan, KAKENHI(22760365), JSPS, Japan, and IGARSS 2011 for their support to this work and presentation.

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