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Cloud Optical & Microphysical Properties (M. D. King, S. Platnick, M

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1 Cloud Optical & Microphysical Properties (M. D. King, S. Platnick, M
Cloud Optical & Microphysical Properties (M. D. King, S. Platnick, M. Gray, E. Moody, et al. – NASA GSFC, UMBC) Optical thickness, particle size (effective radius), and water path 1 km spatial resolution, daytime only, liquid water & ice clouds Solar reflectance technique, VIS through MWIR Water nonabsorbing bands: 0.65, 0.86, 1.24 µm Water absorbing bands: 1.6, 2.1, 3.7 µm Land, ocean, and snow/sea ice surfaces Land surface: 0.65 µm Ocean surface: 0.86 µm Snow/ice surfaces: 1.24 µm MODIS 1st satellite sensor with all useful SWIR, MWIR bands

2 Liquid Water Clouds - ocean surface
Retrieval of tc and re The reflection function of a nonabsorbing band (e.g., 0.86 µm) is primarily a function of optical thickness The reflection function of a near-infrared absorbing band (e.g., 2.14 µm) is primarily a function of effective radius clouds with small drops (or ice crystals) reflect more than those with large particles For optically thick clouds, there is a near orthogonality in the retrieval of tc and re using a visible and near-infrared band Liquid Water Clouds - ocean surface

3 Ice Clouds - ocean surface
Retrieval of tc and re The reflection function of a nonabsorbing band (e.g., 0.86 µm) is primarily a function of optical thickness The reflection function of a near-infrared absorbing band (e.g., 2.14 µm) is primarily a function of effective radius clouds with small drops (or ice crystals) reflect more than those with large particles For optically thick clouds, there is a near orthogonality in the retrieval of tc and re using a visible and near-infrared band Ice Clouds - ocean surface

4 Cloud Optical & Microphysical Properties Retrieval Example
Liquid Water Clouds - ocean surface Liquid Water Clouds - ice surface

5 Cloud Optical & Microphysical Properties
Critical input Cloud mask to retrieve or not to retrieve? Cloud thermodynamic phase use liquid water or ice libraries? Surface albedo for land, ancillary information regarding snow/ice extent (NISE data set) Atmospheric correction requires cloud top pressure, ancillary information regarding atmospheric moisture & temperature (e.g., NCEP, DAO, other MODIS products) 3.7 µm emission (band contains both solar and emissive signal) need cloud top temperature, ancillary for surface temperature (e.g., from NCEP, DAO, ...)

6 MOD12 (IGBP ecosystem classification) + USGS water + tundra
Ecosystem Map (A. H. Strahler, C. B. Schaaf, et al. – Boston University) MOD12 (IGBP ecosystem classification) + USGS water + tundra For the time being we’re using ecosystem as a surrogate for surface albedo.

7 Surface Albedo Surface albedo = ecosystem + MOD43 (Strahler, Schaaf et al.) aggregation
For the time being we’re using ecosystem as a surrogate for surface albedo.

8 Ecosystem Color Scheme
Albedo Movies Loops through bands 0.65, 0.86, 1.24, 1.64, 2.1, and 3.7 µm Loops through seasonal equinox and solstice, progressing from Julian days 91, 173, 293, 356 Ecosystem Color Scheme Pink = Crops Green = Trees Yellows = Barren/Deserts Blues = Savannas

9 Atmospheric Correction
Cloud library calculations give cloud-top quantities (no atmosphere) atmosphere included during retrieval Rayleigh scattering iterative approach applied to 0.65 µm band only (used over land) important for thin clouds and for any clouds with large solar/view angle combinations Atmospheric absorption Well-mixed gases a function of pc, water vapor absorption a function of profile; both a weak function of temperature Assume above-cloud column water vapor amount the primary parameter, vapor profile of minor consequence Library calculations made at a variety of pc, above-cloud column water amounts (scaled from various water vapor and temperature profiles), geometries using MODTRAN 4.0 with scripts for 2-way transmittance calculations requires cloud top pressure, and ancillary information regarding atmospheric moisture (currently using NCEP)

10 Two-way Atmospheric Path Transmittance (1/µ + 1/µ0)
pc = 900 hPa w = 2.0 g-cm-2 above-cloud precipitable water µ0 = 0.8 0.86, 1.24 µm 1.6 µm 0.67 µm 2.1 µm 3.7 µm (1-way µ path) Absorption transmittance For the time being we’re using ecosystem as a surrogate for surface albedo. 3.7 µm cosine of viewing zenith angle (µ)

11 Cloud Optical Thickness in the Arctic: Provisional Production Code (edition 3)
June 2, 2001 tc 20 15 10 5

12 Cloud Optical Thickness in the Arctic: Provisional Production Code (new correction)
June 2, 2001 tc 20 15 10 5

13 Cloud Effective Radius in the Arctic: Provisional Production Code (edition 3)
June 2, 2001 re(µm) 40 34 28 22 16 10 4

14 Cloud Effective Radius in the Arctic: Provisional Production Code (new correction)
June 2, 2001 re(µm) 40 34 28 22 16 10 4

15 Level-2 Global Cloud Images
Cloud Top Temperature Bispectral Phase Cloud Effective Radius Cloud Optical Thickness Cloud Mask Land Classification True Color Image October 1, 2001

16 Drakensberg escarpment
SAFARI 2000 Core Sites Mongu Okavango Delta Etosha Pan Maun Sua Pan Swakopmund Tshane Skukuza Namib Desert Inhaca Island Drakensberg escarpment

17 (red = in-cloud portions)
ER-2, C-130 ground tracks MODIS true color 11 Sept. 2000, 0940 UTC ER-2 Validation region C-130 (red = in-cloud portions)

18 UK C-130 in situ droplet radius, liquid water content
11 Sept. 2000, UTC (S. Osborne, Met Office) optical thickness: C-130 ≈ 5, MODIS ≈ 3±1 MODIS droplet size retrievals

19 Previous + SAFARI 2000 Namibian Sc studies
California central valley fog AVHRR California Sc MAS Arctic stratus (Jan. & April 1989, 2 AM scenes, ) Namibian Sc AVHRR (Sep. 1999, 3 PM scenes) (Oct. 1995, SATE-2 validation) ATSR-2 MODIS 18 Sept. 11 Sept. 7 Sept. 2 Sept. C-130 13 Sept. CV-580 5 10 15 20 25 cloud droplet effective radius (µm) Namibian Sc often have significantly smaller droplet sizes than other regimes? Or lack the larger droplet sizes of other regimes? A difference in CCN concentrations? If so, why?

20 Retrieved Optical Thickness
Comparison of Visible Optical Thickness (G. G. Mace, S. Bensen, K. Sassen – University of Utah) Retrieved Optical Thickness MOD06 Optical Thickness

21 Gridded Level-3 Joint Atmosphere Products (M. D. King, S. Platnick, P
Gridded Level-3 Joint Atmosphere Products (M. D. King, S. Platnick, P. A. Hubanks, et al. – NASA GSFC, UMBC) Daily, 8-day, and monthly products (474.8, 883.2, MB) 1° ´1° equal angle grid Mean, standard deviation, marginal probability density function, joint probability density functions

22 Cloud Optical Thickness
Level-3 Monthly April 2001 tc 20 16 12 8 4

23 Cloud Effective Particle Radius
Level-3 Monthly April 2001 re(µm) 40 34 28 22 16 10 4

24 L3 product bin sizes (liquid water clouds)
MODIS L3 aggregation from 6°x 6° grid off Namibian coast liquid water clouds L3 product bin sizes (liquid water clouds)

25 Cloud Top Pressure (W. P. Menzel, R. Frey, K. Strabala, L
Cloud Top Pressure (W. P. Menzel, R. Frey, K. Strabala, L. Gumley, et al. – NOAA NESDIS, U. Wisconsin/CIMSS) Level-3 Monthly April 2001 pc (hPa) 1000 900 800 700 600 500 400 300

26 Precipitable Water over Land & Sunglint (B. C. Gao, et al
Precipitable Water over Land & Sunglint (B. C. Gao, et al. – Naval Research Laboratory) Level-3 Monthly April 2001 q (cm) 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0

27 MODIS Aerosol Optical Thickness & Effective Radius
ta (0.55 µm) re 0.5 2.4 0.4 1.8 0.3 1.2 0.2 0.6 0.1 0.0 0.0

28 Aerosol Optical Thickness (fine mode) (Y. J. Kaufman, D. Tanré, L. A
Aerosol Optical Thickness (fine mode) (Y. J. Kaufman, D. Tanré, L. A. Remer, D. A. Chu. – NASA GSFC, CNES/USTL) Level-3 Monthly September 2000 ta (0.55 µm) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

29 Aerosol Optical Thickness (coarse mode) (Y. J. Kaufman, D. Tanré, L. A
Aerosol Optical Thickness (coarse mode) (Y. J. Kaufman, D. Tanré, L. A. Remer, D. A. Chu. – NASA GSFC, CNES/USTL) Level-3 Monthly September 2000 ta (0.55 µm) 0.4 0.3 0.2 0.1 0.0


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