GEST 10th Anniversary 1

EFFECTS OF ICE PARTICLE SIZE VERTICAL INHOMOGENEITY ON THE PASSIVE REMOTE SENSING OF ICE CLOUDS

Zhibo Zhang (UMBC GEST)June 7th,2010Celebrating GEST’s 10th Anniversary

Many thanks to:Steven Platnick (NASA GSFC), Ping Yang (Texas A&M University), Andrew K. Heidinger (NOAA NESDIS) and Jennifer Comstock (PNNL)

Outline 2

Outline

Background Exciting discoveries Summary

Background 3

What happens in the night?MODIS daytime granule Product size ~40M

Optical thicknessEffective radius

MODIS nighttime granule Product size ~4M

Optical thicknessEffective radius

? ?

Background 4

Infrared approach is needed (and already funded by NASA) to fill the nighttime gap in MODIS cloud product

But, does the infrared approach provide the same cloud property retrievals as the solar approach? If not, what are the potential reasons?

Our research focuses on the effect of cloud particle size vertical inhomogeneity

Background 5

Ice cloud vertical inhomogeneity

Microphysical processes that could lead to ice particle size vertical inhomogeneity.1) Condensation growth; 2) Size sorting; 3) Coalescence & aggregation

Background 6

MODIS cloud retrieval algorithm

Plane-parallelVertical

homogenous

Cloud in MODIS retrieval algorithm

Real cloud

Ice Particle model

Ice clouds in reality

Microphysical processes that could lead to ice particle size vertical inhomogeneity.1) Condensation growth; 2) Size sorting; 3) Coalescence & aggregationCould cloud particle size inhomogeneity lead cause inconsistency between the solar and infrared methods?

Exciting Discoveries 7

Thin cloudsSolar method IR method

•Both methods tend to underestimate the effective size.•IR method is worse due to higher degree of nonlinearity.

Exciting Discoveries 8

Thick clouds (1)Solar method IR method

•Solar method is highly sensitive to cloud particle at cloud top•IR method is relatively insensitive to cloud vertical inhomogeneity.

Exciting Discoveries 9

Thick Clouds (2)

Cloud particle size

Cloud top

Cloud baseIR < solar IR ~ solar

Summary 10

Summary

If cloud particle size is vertically inhomogeneous……

For thin clouds, both solar and IR methods tend to underestimate the effective radius

For thick clouds, it depends…Take-home message• Cloud particle inhomogeneity could

lead to inconsistency between solar and IR methods.

• Be cautious when comparing or combining the two methods.

GEST 10th Anniversary 11

Happy Birthday, GEST!

This talk is based on Zhang et al 2010 JGR (Will be highlighted in EOS)