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) Koren et al. (2010)
Ex) Nakajima et al. (2001)
Cloud droplet radius
Cloud top height
Difficult to obtain aerosol data?
Purpose: Examine Cloud droplet radius - Cloud top height relationship

4. Data: CloudSat 2B-CWC-RVOD (Dec. 2006-Feb. 2007)
Conditions of the clouds to be analyzed
Cloud top height: highest bin with value
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 height7

8. Cloud droplet effective radius - Cloud top height relationship

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. Significant negative correlation still appears
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( ), JSPS, Japan, and IGARSS 2011 for their support to this work and presentation.