Bryan A. Baum 1, Ping Yang 2, Andrew J. Heymsfield 3, and Sarah Thomas 4 1 NASA Langley Research Center, Hampton, VA 2 Texas A&M University, College Station,

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