Bryan A. Baum 1, Ping Yang 2, Andrew J. Heymsfield 3, and Sarah Thomas 4 1 NASA Langley Research...
-
Upload
arline-fletcher -
Category
Documents
-
view
216 -
download
1
Transcript of Bryan A. Baum 1, Ping Yang 2, Andrew J. Heymsfield 3, and Sarah Thomas 4 1 NASA Langley Research...
Bryan A. Baum1, Ping Yang2, Andrew J. Heymsfield3, andSarah Thomas4
1 NASA Langley Research Center, Hampton, VA 2 Texas A&M University, College Station, TX 3 National Center for Atmospheric Research, Boulder, CO 4 Cooperative Institute for Meteorological Satellite Studies, University of
Wisconsin-Madison
Development of Ice Cloud Scattering Models from Polar, Midlatitude, and Tropical In-situ Measurements
Development of Ice Cloud Scattering Models from Polar, Midlatitude, and Tropical In-situ Measurements
1. Derive a set of microphysical models that better represent the range of naturally occurring ice clouds.
2. Build a set of multispectral scattering models for MODIS and other imagers.
3. Suggest two approaches for validation of the new models.
Goals of the Work Goals of the Work
Version 1 Version 2 Version 3
Particle Size Distributions (PSD)
12 PSDs discretized to 5 size bins, very crude;
Some models are similar to others
3 Averaged PSDs discretized to 27 size bins, based on our evaluation of Heymsfield’s data
Based on Gamma distribution fits to PSDs;
>30 bins (more bins for large sizes)
Microphysical Data Source
FIRE-I, FIRE-II, and older; difficult to trace back to source
FIRE-I, FIRE-II, ARM FIRE, ARM, TRMM, SHEBA, CRYSTAL
Habit Distributions
and Habits
Exactly the same for each model; based on plates, solid/hollow columns, 2D bullet rosettes, aggregrates
Varies by model; based on plates, solid/hollow columns, 2D bullet rosettes, aggregrates
Varies by model;
New habits: droxtals, 3D bullet rosettes
Scattering models Scattering models computed in 1997; Based on Terra SRF
Scattering models computed 2000-2002; spectral resolution based on Terra SRFs
Recompute scattering libraries with higher resolution in particle size and wavelength; add new parameters such as Qe; Dm
Limitations Models based solely on midlatitude cirrus; not readily adaptable to global analyses
Analysis of size spectra is complex; based solely on midlatitude cirrus
TBD
MODIS Version 1 Cirrus Microphysical Models
Note: 5 size bins; fixed habit percentage used in all models
MODIS Version 1 Cirrus Microphysical Models
Note: 5 size bins; fixed habit percentage used in all models
Max length < 70 m50% bullet rosettes25% hexagonal plates25% hollow columns
Max length > 70 m30% bullet rosettes20% hexagonal plates20% hollow columns30% aggregates
Baum, B. A., D. P. Kratz, P. Yang, S. Ou, Y. Hu, P. F. Soulen, and S-C. Tsay, 2000a: Remote sensing of cloud properties using MODIS Airborne Simulator imagery during SUCCESS. I. Data and models. J. Geophys. Res., 105, 11,767-11,780.
Validation Approach #1
ATSR-2 Measurement Residual Analysis
Testing the single-scattering properties of MODIS Version 1 cirrus models between scattering angles of 57o and 170o
Dr. Anthony J. Baran and Dr S. Havemann
Met Office, UK
Channels located at 0.55, 0.66, 0.87, 1.6, 3.7, 10.8, and 11.9 m
Cloud height determined by parallax technique
Cloud properties inferred by optimal estimation method
Perform forward calculations, then minimize difference betweenmeasurements and simulations
ATSR-2 Image at 0.87 m21 July, 1996; Latitude -32.5o; Longitude -95.9o
ATSR-2 Image at 0.87 m21 July, 1996; Latitude -32.5o; Longitude -95.9o
ATSR-2 Residual Results21 July, 1996;
Latitude -32.5o; Longitude -95.9o Scattering angle: 155.8o (forward)
ATSR-2 Residual Results21 July, 1996;
Latitude -32.5o; Longitude -95.9o Scattering angle: 155.8o (forward)
ATSR-2 Residual Results21 July, 1996;
Latitude -32.5o; Longitude -95.9o; Scattering angle: 118.9o (nadir)
ATSR-2 Residual Results21 July, 1996;
Latitude -32.5o; Longitude -95.9o; Scattering angle: 118.9o (nadir)
False Color Image R: 0.65 m reflectance G: 0.87 m reflectance B: 1.6 m reflectance
ATSR-2 Image23 July, 1996; Latitude -10.1o; Longitude -122.6o
ATSR-2 Image23 July, 1996; Latitude -10.1o; Longitude -122.6o
ATSR-2 Residual Results23 July, 1996;
Latitude -10.1o; Longitude -122.6o Scattering angle: 138.7o (forward)
ATSR-2 Residual Results23 July, 1996;
Latitude -10.1o; Longitude -122.6o Scattering angle: 138.7o (forward)
ATSR-2 Residual Results23 July, 1996;
Latitude -10.1o; Longitude -122.6o Scattering angle: 157.2o (nadir)
ATSR-2 Residual Results23 July, 1996;
Latitude -10.1o; Longitude -122.6o Scattering angle: 157.2o (nadir)
Replicator Ice Crystal Profiles from FIRE Cirrus II CampaignReplicator Ice Crystal Profiles from FIRE Cirrus II Campaign
Version 1 Version 2 Version 3
Particle Size Distributions (PSD)
12 PSDs discretized to 5 size bins, very crude
3 Averaged PSDs discretized to 27 size bins, based on our evaluation of Heymsfield’s data
Based on Gamma distribution fits to PSDs;
>30 bins (more bins for large sizes)
Microphysical Data Source
FIRE-I, FIRE-II, and older; difficult to trace back to source
FIRE-I, FIRE-II, ARM FIRE, ARM, TRMM, SHEBA, CRYSTAL
Habit Distributions
and Habits
Exactly the same for each model; based on plates, solid/hollow columns, 2D bullet rosettes, aggregrates
Varies by model; based on plates, solid/hollow columns, 2D bullet rosettes, aggregrates
Varies by model;
New habits: droxtals, 3D bullet rosettes
Scattering models Scattering models computed in 1997; Based on Terra SRF
Scattering models computed 2000-2002; spectral resolution based on Terra SRFs
Recompute scattering libraries with higher resolution in particle size and wavelength; add new parameters such as Qe; Dm
Limitations Models based solely on midlatitude cirrus; not readily adaptable to global analyses
Analysis of size spectra is complex; based solely on midlatitude cirrus
TBD
Cirrus Size Distributions Based on In-situ Data From Midlatitude Cirrus
Cirrus Size Distributions Based on In-situ Data From Midlatitude Cirrus
Version 2: Scattering properties available for 27 size bins
MODIS - Current Set ofCirrus Models (Version 1)
Max length < 70 m50% bullet rosettes25% hexagonal plates25% hollow columns
Max length > 70 m30% bullet rosettes20% hexagonal plates20% hollow columns30% aggregates
Cirrus Habit Percentages Based on In-situ Data From Midlatitude Cirrus
Cirrus Habit Percentages Based on In-situ Data From Midlatitude Cirrus
FIRE-II - avg. of3 cases (cold cirrus)
Max length < 100 m35% bullet rosettes46% hexagonal plates16% hollow columns 3% aggregates
Max length > 100 m38% bullet rosettes 0% hexagonal plates22% hollow columns40% aggregates
FIRE-I - avg. of5 cases (warm cirrus)
Max length < 150 m37% bullet rosettes 0% hexagonal plates63% hollow columns 0% aggregates
Max length > 150 m33% bullet rosettes 0% hexagonal plates27% hollow columns40% aggregates
ARM-IOP - avg. of 2 cases (cirrus uncinus)
Max length < 100 m 0% bullet rosettes70% hexagonal plates10% hollow columns20% aggregates
Max length > 100 m75% bullet rosettes 0% hexagonal plates 0% hollow columns25% aggregates
Nasiri, S. L., B. A. Baum, A. J. Heymsfield, P. Yang, M. Poellot, D. P. Kratz, and Y. Hu: Development of midlatitude cirrus models for MODIS using FIRE-I, FIRE-II, and ARM in-situ data. J. Appl. Meteor., 41, 197-217, 2002.
Version 1 Version 2 Version 3
Particle Size Distributions (PSD)
12 PSDs discretized to 5 size bins, very crude
3 Averaged PSDs discretized to 27 size bins, based on our evaluation of Heymsfield’s data
Based on Gamma distribution fits to PSDs;
>30 bins (more bins for large crystal sizes)
Microphysical Data Source
FIRE-I, FIRE-II, and older; difficult to trace back to source
FIRE-I, FIRE-II, ARM FIRE, ARM, TRMM, SHEBA, CRYSTAL
Habit Distributions
and Habits
Exactly the same for each model; based on plates, solid/hollow columns, 2D bullet rosettes, aggregrates
Varies by model; based on plates, solid/hollow columns, 2D bullet rosettes, aggregrates
Varies by model;
New habits: Droxtals, 3D bullet rosettes
Scattering models Scattering models computed in 1997; Based on Terra SRF
Scattering models computed 2000-2002; spectral resolution based on Terra SRFs
Recompute scattering libraries with higher resolution in particle size and wavelength; add new parameters such as Qe; Dm
Limitations Models based solely on midlatitude cirrus; not readily adaptable to global analyses
Analysis of size spectra is complex; based solely on midlatitude cirrus
TBD
Particle size distributions (PSD) in form of gamma distributions
PSDs developed from polar, midlatitude, and tropical data
Ice crystal scattering properties recomputed for a variety of habits
(including new habits like the droxtal and 3D bullet rosette)
Higher spectral resolution for scattering property calculations
Higher resolution in discretization of large particle sizes
What’s new for Version 3? What’s new for Version 3?
Particle Size Distributions Particle Size Distributions
Gamma size distribution* has the form:
N(D) = NoDe-D
where D = max diameter
No = intercept
= dispersion
= slope
The intercept, slope, and dispersion values are derived for each PSD by matching three moments (specifically, the 1st, 2nd, and 6th moments)
Note: when = 0, the PSD reduces to an exponential distribution
*Heymsfield et al., Observations and parameterizations of particle size distributions in deep tropical cirrus and stratiform precipitating clouds: Results from in situ observations in TRMM field campaigns. J. Atmos. Sci., 59, 3457-3491, 2002.
Midlatitude Cirrus Clouds
FIRE-1 (1986)FIRE-2 (1991)ARM IOP (2000)
Tropical ice cloud characteristics
• Form in an environment having much higher vertical velocities
• Size sorting is not as well pronounced
• Large crystals often present at cloud top
• Crystals may approach cm in size.
• Habits tend to be more complex
Tropical Ice Clouds - TRMMTropical Ice Clouds - TRMM
In-Situ Data: Gamma DistributionsIn-Situ Data: Gamma Distributions
Individual particle size distributions:
• 2025 PSDs from TRMM and midlatitude (FIRE-1, FIRE-2, ARM) campaigns
• 331 PSDs from SHEBA (May)
• No way to tell location within cloud layer where PSD data were derived
Effective Diameter vs. Median Mass DiameterEffective Diameter vs. Median Mass Diameter
De calculated assuming only hollow columns
Effect of habits is still being explored
Ice Crystal HabitsIce Crystal Habits
Midlatitude Cirrus
Tropical Ice Clouds
Polar ice clouds - TBD
Simulated Particle HabitsReplicator Particle Habits
Note: the use of the droxtal forsmall particles is quite recent.
Small, Nonspherical Ice Crystals: Droxtals Small, Nonspherical Ice Crystals: Droxtals
Yang, P., B. A. Baum, A. J. Heymsfield, Y.-X. Hu, H.-L. Huang, S.-C. Tsay, and S. Ackerman: Single scattering properties of droxtals. In press, J. Quant. Spectrosc. Radiant. Transfer, 2003.
Geometry of ice crystals observed in an ice fog (after Ohtake, 1970)
1x10 -2
1x10 -1
1x10 0
1x10 1
1x10 2
2x10 2
0 60 120 180
droxtal
sphere
0 60 120 180 0 60 120 180 0 60 120 180
=0.66µm=5X
=0.66µm=10X
=11µm=5X
=11µm=10X
(Scattering Angle o)
Ice Crystal Profiles From Tropical CirrusIce Crystal Profiles From Tropical Cirrus
Simulated Particle HabitsCPI Particle Habits
Suggestions for Future ModelsSuggestions for Future Models
The exact meaning of our satellite-derived “effective diameter” continues to confuse many in the community because of the complexity of ice habits and the abundance of definitions
What modelers seem to want is IWP
One parameter that both in-situ aircraft and surface-based radar measurements provide is median mass diameter (Dm)
Suggestion: Include Dm and IWP as part of retrieval
Optical Depth - IWP2 Parameter Solution
Optical Depth - IWP2 Parameter Solution
*Heymsfield, Matrosov, and Baum: Ice water path-optical depth relationships for cirrus and deep stratiform ice cloud layers. Submitted to J. Appl. Met., 2003.
Here’s one way to relate directly the visible optical depth and IWP*
Includes midlatitude cirrus (FIRE-1, FIRE-2, ARM IOP) and TRMM data (Heymsfield et al.,
J. Atmos. Sci., 59, 3457-3491, 2002)
Issues:
• limited data from in-situ measurements
• can not assess how representative these data are
Optical Depth - IWP3 Parameter Solution
Optical Depth - IWP3 Parameter Solution
*Obtain IWP using layer-averaged median mass diameter Dm and visible optical depth v, where coefficients e0, e1 are determined for midlatitude and tropical clouds
Advantages:
• readily obtain Dm from radar data (e.g., ARM)
• can derive Dm for each ice model
• determine v from MAS, MODIS
• easier to validate the models this way, and provides a path to derive error estimates for IWP
*Heymsfield, Matrosov, and Baum: Ice water path-optical depth relationships for cirrus and deep stratiform ice cloud layers. Submitted to J. Appl. Met., 2003.
If we include Dm and IWP in the MOD06 product…
Compare MODIS-derived IWP/Dm to ARM CART site retrievals of IWP/ Dm
Can also incorporate field experiment data (MAS vs. radar)
Build error estimates from these comparisons as function of synoptic cloud type
Validation Approach #2Validation Approach #2
Short term plans Short term plans
Developing set of microphysical models based on measurement-based set of PSDs from polar, midlatitude, and tropical data -Could use some guidance here
Soon will be recomputing libraries of ice scattering properties to extend wavelength domain and range of particle sizes
Will send set of models to Anthony Baran for independent testing using AATSR data
Extending work to IR interferometer measurements as well as MISR and other imagers
Midlatitude Cirrus Midlatitude Cirrus
Midlatitude cirrus often show 3 distinct layers:
- small particles in “generating region” near cloud top
- growth region containing pristine ice crystals in middle region
- sublimation layer near cloud base, with largest particles