Determination of Thermodynamic Cloud Phase and

1
Determination of Thermodynamic Cloud Phase and
Reflectance Field from Radiance Measurements
Junshik Um and Greg McFarquhar
University of Illinois at Urbana
Champaign Department of Atmospheric Sciences
16th ARM Science Team Meeting March 29,
2006 Albuquerque, NM
2
Acknowledgement

• ARM UAV Program
• DOE ARM Program
• Tim Tooman
• Rick Petty
• Bob McCoy
• Andreas Macke
• Jim Mather

3
Outline

• Why do we use Diffuse Field Camera (DFC)?
• How does DFC give reflectance function?
• 2004 MPACE DFC Observations
• Theoretical vs. observed reflectance
• function
• Conclusions

4
Why do we use DFC?

• Thermodynamic cloud phase impacts on vertical
• profiles of radiative heating
• Scattering properties of ice and water clouds
  are
• different (e.g., halos and backscattering)
• Satellite has limited viewing angles and
  resolution
• Higher resolution and more viewing angles data
• from DFC help to interpret satellite
  measurements

5
Proteus
6
Diffuse Field Cameras
7
Principle
8
ARM c4 level data, Oct. 12th, 2004
9
2004 MPACE Observations
10
Results
12 scenes average reflectance function, SZA78.98

• Strong backscattering
• Cloudbow at the primary rainbow angle of 140

11
(No Transcript)
12

• Good agreement at backscattering angles
• Cloudbow at the primary rainbow angle

13
Conclusions

• DFC data are used to determine the directional
• dependence of reflectance that can be
  compared
• against theoretical calculations for water
  and ice
• clouds.
• The 12 selected DFC scenes show a cloudbow at
• the primary rainbow angle of 140 and
• backscattering, which are intrinsic
  scattering
• features of water clouds.
• Agreement between the DFC and water cloud
• reflectance function is noted, which is
  consistent
• with tops of MPACE clouds being dominated by
  
• water.
• Implication to help satellite interpretation

14
Future Work

• 2002 SGP-IOP (middle latitude cloud)
• 2004 MPACE (Artic cloud)
• 2006 TWP-ICE (tropical cloud)
• Scattering phase function of cloud will be
• derived.
• Dominant ice crystal habit will be determined
• for ice clouds
• Sometimes no clouds No worries !

15
(No Transcript)
16
Results
17
Results
18
Observations