x x x cloud variables top pressure cloud type effective radius

Cloud Variables Top pressure

Bottom pressure

Cloud cover/cloud detection

Optical thickness

Liquid water

Effective radius

Particle phaseParticle shape

Cloud type

X

X

X

Bottom pressure/heigth

• A chi serve? Aviazione, bilancio radiativo (LW bottom)

• Come si stima? - Spessore (topmolecolare-topO2)

- LWC - Tipo (climatologia) - cloud radar

Cloud type

• A chi serve

+

Optical thickness

Bid

irect

iona

l ref

lect

ance

g = 0.85= 0.86= 0.87

Ice particle habit

• A chi serve

S. Platnick, ISSAOS ‘02

Ice Cloud MicrophysicsCRYSTAL-FACE, A. Heymsfield

25 July 2002(VIPS)

25 July 2002(VIPS)

CPI: 7 July 2002

Ice cloud microphysics, cont.

MODIS ice crystal library habits/shapes


Yang et al., “Single-scattering properties of complex ice crystals in terrestrial Atmosphere”, Contr. Atmos. Phys., 71, 223-248, 1998.

Effective radius and optical thickness2 2

0 0 0 0 0

( ) ( ) 2 ( )z z z

ext extk dz r Q r n r drdz r n r drdz

CLM: Cloud microphysical properties

• 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 c and re using a visible and near-infrared band

Retrieval of c and re

Liquid Water Clouds - ocean surface

• 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 c and re using a visible and near-infrared band

Retrieval of c and re

Ice Clouds - ocean surface

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

Multiple scatteringwater cloud examples


Optical thickness

1- = 0

Bid

irect

iona

l ref

lect

ance

g = 0.85= 0.86= 0.87

reflectance vs. asymmetry parameter (g)

g = < cos() p()> ~ re


1- re

Bid

irect

iona

l ref

lect

ance

Optical thickness Optical thickness

g = 0.85

1- = 0.006

1- = 0

1- = 0.020

1- = 0.006

g = < cos() p()> ~ re

1- = 0

g = 0.85= 0.86= 0.87

reflectance vs. asymmetry parameter (g)

Multiple scattering - reflectancewater cloud examples

reflectance vs. 1-0 (R ~1-0N)

Ship track schematic

N ~ 40 cm-3

W ~ 0.30 g m-3

re ~ 11.2 µm

N ~ 100 cm-3

W ~ 0.75 g m-3

re ~ 10.5 µm


courtesy, P. Durkee

Level-1B Image of California Stratus with Ship Tracks

marine marine stratocumulusstratocumulus

April 25, 2001

Red =0.65 µmGreen = 0.56 µmBlue =0.47 µm

Level-1B Image of California Stratus with Ship Tracks

April 25, 2001

Red =0.65 µmGreen = 0.56 µmBlue =0.47 µm

3.7 µm band3.7 µm band

CLM: Cloud microphysical properties• Cloud effective droplet radius• Cloud optical thickness

Cloud phase

10-10

10-8

10-6

10-4

10-2

100

0.1 1 10

mi water mi ice

Imag

inar

y R

efra

ctio

n In

dex

Wave Length [m]

VIS

0.9

3.810.8

12.0

ABS

ORP

TIO

N

1.6

IR thermodynamic phase retrieval (B. Baum, S. Ackerman, S. Nasiri, NASA LaRC, U. Wisconsin/CIMSS)


Abs

orpt

ion

coef

ficie

nt (c

m-1)

water

ice

ice

16.7 14.3 11.1 10.0 9.1 8.3 µm12.5


High Ice clouds

BTD[8.5-11] > 0 over a largerange of optical thicknesses Tcld = 228 K

Midlevel clouds

BTD[8.5-11] values are similar(i.e., negative) for both waterand ice cloudsTcld = 253 K

Low-level, warm clouds

BTD[8.5-11] values alwaysnegativeTcld = 273 K

Ice: Cirrus model derived from FIRE-I in-situ data *Water: re=10 mAngles = 45o, = 20o, and 40o

Profile: midlatitude summer

Simulations of Ice and Water Phase Clouds8.5 - 11 m BT Differences

=

=

*Nasiri et al, 2001Nasiri et al., 2002

Bispectral IR algorithm

Uncertain

Mixed

Phase

Ice

Liquid

Water

No

Retrieval

Effect of multilayered clouds


CLP Cloud phase

Ice/Water Clouds Separate in 8.6-11 vs 11-12 um BT plots

Cloud Composition

Ice Cloud

Water Cloud

Contrails

Contrails

Infrared Temperature Difference - 8.6 m (Band 29) - 11.0 m (Band 31)

Infrared Temperature Difference - 11.0 m (Band 31) - 12.0 m (Band 32)

MODIS Image Over Kansas - 21 April 1996

x x x cloud variables top pressure cloud type effective radius

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