Stud

y of

the

rela

tions

hip

betw

een

ice

phas

e an

d cl

oud-

top

tem

pera

ture

with

MO

DIS

dat

aC

athe

rine

Nau

dan

d A

ntho

ny D

el G

enio

, GIS

S, N

Y

Abs

trac

t: C

loud

feed

back

in G

CM

clim

ate

chan

ge si

mul

atio

ns is

sens

itive

topr

edic

tions

of c

loud

pha

se b

ecau

se o

f the

diff

eren

t mic

roph

ysic

al a

nd ra

diat

ive

prop

ertie

s of l

iqui

d an

d ic

e. U

sual

ly th

e liq

uid-

ice

trans

ition

is p

aram

eter

ized

as a

sim

ple

func

tion

of te

mpe

ratu

re, b

ut ic

e oc

curr

ence

in c

loud

s is k

now

n to

dep

end

on th

e un

derly

ing

dyna

mic

s of t

he c

loud

syst

em.

We

are

usin

g M

OD

IS d

ata

to g

ain

insi

ghts

into

this

beh

avio

ur th

at m

ight

serv

e as

a g

uide

to im

prov

ed p

aram

eter

izat

ions

. C

loud

top

tem

pera

ture

s wer

e ob

tain

ed fr

om5-

min

leve

l 2 M

OD

IS T

ERR

A a

nd A

QU

A d

ay-ti

me

gran

ules

, alo

ng w

ith S

WIR

pha

se fo

r all

avai

labl

e w

inte

rs (D

ec-J

an-F

eb)f

rom

the

star

t of t

he m

issi

ons u

ntil

Febr

uary

200

4. C

loud

y pi

xels

in e

ach

gran

ules

wer

e se

lect

ed o

ver t

he n

orth

ern

parts

of t

he A

tlant

ic a

nd P

acifi

c oc

eans

in th

e ar

ea c

over

ed b

y th

e st

orm

trac

ks a

nd a

ggre

gate

d in

2x2

.5°

grid

box

es. F

or e

ach

grid

box

, all

pixe

ls id

entif

ied

as ic

e on

ly a

nd ic

e or

wat

er a

re se

lect

ed a

nd so

rted

into

tem

pera

ture

bin

s def

ined

eve

ry 2

K fr

om 2

00 to

300

K. H

isto

gram

s can

then

be

obta

ined

that

giv

e th

e fr

actio

n of

ice

clou

d pi

xels

ove

r the

tota

l num

ber o

f ice

and

wat

er c

loud

pix

els i

n a

give

n te

mpe

ratu

re ra

nge.

The

grid

boxe

s are

furth

er

aggr

egat

ed a

long

the

best

est

imat

e of

the

stor

m tr

ack

traje

ctor

yob

tain

ed fr

om a

con

tem

pora

ry N

CEP

rean

alys

is st

orm

trac

k at

las (

Cha

ndle

r and

Jona

s, 19

99) a

nd d

ivid

ed in

to a

wes

t, ce

ntra

l and

eas

t reg

ion.

The

stor

m tr

ajec

torie

s are

cho

sen

so th

at th

e st

orm

freq

uenc

y of

occ

urre

nce

does

not

var

y m

uch

over

the

traje

ctor

y. H

owev

er, w

e fin

d th

at b

oth

mea

n in

tens

ity (c

entra

l pre

ssur

e) a

nd se

verit

y (p

eak

inte

nsity

) inc

reas

e al

ong

the

track

.

Atla

ntic

oce

an

NC

EP st

orm

freq

uenc

y (%

) for

all

win

ters

from

Dec

embe

r 200

0 to

Fe

brua

ry 2

004.

NC

EP st

orm

mea

n in

tens

ity (m

b)

for a

ll w

inte

rs fr

om D

ecem

ber 2

000

to F

ebru

ary

2004

.

NC

EP st

orm

seve

rity

(mb)

for a

ll w

inte

rs fr

om D

ecem

ber 2

000

to

Febr

uary

200

4.

MO

DIS

ice

clou

d fr

actio

n ve

rsus

clo

ud-

top

tem

pera

ture

for a

ll m

onth

s and

bot

h pl

atfo

rms a

ccum

ulat

ed in

the

wes

tern

(s

olid

), ce

ntra

l (da

shed

) and

eas

tern

(dot

-da

sh) p

ortio

ns o

f the

stor

m tr

ack.

Ther

e ar

e at

leas

t 10,

000

pixe

ls in

eac

h 2K

te

mpe

ratu

re ra

nge.

NC

EP st

orm

freq

uenc

y (%

) for

all

win

ters

from

Dec

embe

r 200

0 to

Fe

brua

ry 2

004.

NC

EP st

orm

mea

n in

tens

ity (m

b)

for a

ll w

inte

rs fr

om D

ecem

ber 2

000

to F

ebru

ary

2004

.

NC

EP st

orm

seve

rity

(mb)

for a

ll w

inte

rs fr

om D

ecem

ber 2

000

to

Febr

uary

200

4.

For 4

diff

eren

t tem

pera

ture

rang

es, i

ce

clou

d fr

actio

n ve

rsus

stor

m fr

eque

ncy

(top)

, mea

n in

tens

ity (c

entra

l) an

d se

verit

y (b

otto

m).

The

rang

es a

re: 2

30-

240K

(col

umn

1), 2

40-2

50K

(col

umn

2), 2

50-2

60K

(col

umn

3) a

nd 2

60-

270K

(col

umn

4).

Var

iatio

ns a

long

the

estim

ated

stor

m

mea

n tra

ject

ory

of st

orm

freq

uenc

y (to

p), m

ean

inte

nsity

(cen

tre) a

nd

seve

rity

(bot

tom

) as t

he st

orm

s mov

e ea

stw

ard.

Paci

fic O

cean

For 4

diff

eren

t tem

pera

ture

rang

es, i

ce

clou

d fr

actio

n ve

rsus

stor

m fr

eque

ncy

(top)

, mea

n in

tens

ity (c

entra

l) an

d se

verit

y (b

otto

m).

The

rang

es a

re: 2

30-

240K

(col

umn

1), 2

40-2

50K

(col

umn

2), 2

50-2

60K

(col

umn

3) a

nd 2

60-

270K

(col

umn

4).

MO

DIS

ice

clou

d fr

actio

n ve

rsus

clo

ud-

top

tem

pera

ture

for a

ll m

onth

s and

bot

h pl

atfo

rms a

ccum

ulat

ed in

the

wes

tern

(s

olid

), ce

ntra

l (da

shed

) and

eas

tern

(dot

-da

sh) p

ortio

ns o

f the

stor

m tr

ack.

Ther

e ar

e at

leas

t 10,

000

pixe

ls in

eac

h 2K

te

mpe

ratu

re ra

nge.

Var

iatio

ns a

long

the

estim

ated

stor

m

mea

n tra

ject

ory

of st

orm

freq

uenc

y (to

p), m

ean

inte

nsity

(cen

tre) a

nd

seve

rity

(bot

tom

) as t

he st

orm

s mov

e ea

stw

ard.

Prel

imin

ary

Con

clus

ion:

Ove

r the

Atla

ntic

stor

m tr

ack

regi

on, w

e fo

und

that

as t

he c

loud

s mov

e ea

stw

ard,

the

ice

clou

d fr

actio

n at

a g

iven

tem

pera

ture

tend

s to

incr

ease

, im

plyi

ng th

at h

eter

ogen

eous

free

zing

bec

omes

mor

e im

porta

nt a

s the

stor

ms t

rave

l eas

twar

d. F

urth

erm

ore,

ther

e is

aco

rrel

atio

n be

twee

n ic

e cl

oud

frac

tion

and

stor

m in

tens

ity, a

t lea

st fo

r sto

rmsw

ith a

larg

e en

ough

inte

nsity

(pre

ssur

e <

980m

b). A

s st

orm

inte

nsity

incr

ease

s, ic

ecl

oud

frac

tion

incr

ease

s, su

gges

ting

a dy

nam

ic c

ontro

l.

How

ever

, ove

r the

Pac

ific

ocea

n, th

e be

havi

our i

sinv

erte

d: th

e ic

e cl

oud

frac

tion

decr

ease

s as s

torm

s mov

e ea

stw

ard

and

isan

ticor

rela

ted

with

stor

m in

tens

ity, s

ugge

stin

g an

othe

r inf

luen

ce, p

erha

ps v

aryi

ng a

eros

ol c

once

ntra

tion.