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Effects of ice particle size vertical inhomogeneity on the passive remote sensing of ice clouds

Zhibo Zhang (UMBC GEST) June 7 th ,2010 Celebrating GEST’s 10 th Anniversary . Effects of ice particle size vertical inhomogeneity on the passive remote sensing of ice clouds. Many thanks to: Steven Platnick (NASA GSFC), Ping Yang (Texas A&M University),

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Effects of ice particle size vertical inhomogeneity on the passive remote sensing of ice clouds

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  1. Zhibo Zhang (UMBC GEST) June 7th,2010 Celebrating GEST’s10th Anniversary Effects of ice particle size vertical inhomogeneity on the passive remote sensing of ice clouds Many thanks to: Steven Platnick (NASA GSFC), Ping Yang (Texas A&M University), Andrew K. Heidinger (NOAA NESDIS) and Jennifer Comstock (PNNL) GEST 10th Anniversary

  2. Outline • Background • Exciting discoveries • Summary Outline

  3. What happens in the night? MODIS daytime granule Product size ~40M MODIS nighttime granule Product size ~4M Optical thickness Effective radius Optical thickness Effective radius ? ? Background

  4. Infrared approach is needed (and already funded by NASA) to fill the nighttime gap in MODIS cloud product But, does the infrared approach provide the same cloud property retrievals as the solar approach? If not, what are the potential reasons? Our research focuses on the effect of cloud particle size vertical inhomogeneity Background

  5. Ice cloud vertical inhomogeneity Microphysical processes that could lead to ice particle size vertical inhomogeneity. 1) Condensation growth; 2) Size sorting; 3) Coalescence & aggregation Background

  6. MODIS cloud retrieval algorithm Plane-parallel Vertical homogenous Real cloud Cloud in MODIS retrieval algorithm Ice clouds in reality Ice Particle model Microphysical processes that could lead to ice particle size vertical inhomogeneity. 1) Condensation growth; 2) Size sorting; 3) Coalescence & aggregation Could cloud particle size inhomogeneity lead cause inconsistency between the solar and infrared methods? Background

  7. Thin clouds IR method Solar method • Both methods tend to underestimate the effective size. • IR method is worse due to higher degree of nonlinearity. Exciting Discoveries

  8. Thick clouds (1) IR method Solar method • Solar method is highly sensitive to cloud particle at cloud top • IR method is relatively insensitive to cloud vertical inhomogeneity. Exciting Discoveries

  9. Thick Clouds (2) Cloud top IR < solar IR ~ solar Cloud base Cloud particle size Exciting Discoveries

  10. Summary If cloud particle size is vertically inhomogeneous…… • For thin clouds, both solar and IR methods tend to underestimate the effective radius • For thick clouds, it depends… Take-home message • Cloud particle inhomogeneity could lead to inconsistency between solar and IR methods. • Be cautious when comparing or combining the two methods. Summary

  11. Happy Birthday, GEST! This talk is based on Zhang et al 2010 JGR (Will be highlighted in EOS) GEST 10th Anniversary

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