p a m S d t l c s s d k B S T t e r ( Section [email protected] WERI, Univ.ofGuam,Mangilao, Guam96923 Laboratory (Long2000). effort o normalized backscatterdatasignal(sigma 2. overall derived their visible w a or large (Atl s ca microwave N satellite. from surface 1. k d c * T J o h e e i Corresponding authoraddress: o e e n i m y a n e e n n c e h h e Y e P i R m w e e a

s n c r e n o p e THE NRCS p y t p v c p i e c a INTRODUC U 4

v

t e s m r o v C a e d l i i

n s w i i a r e e i i

t o e a W l r d l e .

c c i

r l n e i a

s

r l o e 10 o

u n S o o

r n s m a n l m n the

t e t r v a u s , r

p a i e i r w s i n

t y

r n a e

r e

M s n

n

n n e i . v o t m o i i a b t y analysis k d o

m e

i

n t e n r w h s

g

d t c o i m a T l o s w

l

p i e i high. i e

n

u t t w o e

d t c e g o

l (

t s f , s e h

w u a

h l h i h ( e t a A o o w N

a i t

n r g d

r u w h T N

a i n

t i n e ( r o n a i e o i

r s i Roger T.Edson, n f r a t h o h g s g

s

i

c i T f R e N

l o C d

s c t

t B f g r R

w a h . d v s i

n e e

. h y a

d e

J

g C e

b a i N C

e p O l

o c

i e r c 6

t s i

t C

a s e

2 l d t o g e a a m h n IMAGE h a y h l Normalized radarcross w

x r H s h s e p a f w r

s

R S

p

TION v A , 0 a f w h t t o

s S t

e

e e g a overthetropicaloceans. a k e )

e

U a o

t a a h i a e o ) i 0 t

C

A d t n i r rain r

s P m g n t e ) m d o l t a =

, s e w r g e e r t

w e g

s

0 h u d o t r t e /

S d a a e a n t r i a , 5 r e a

i s e e N o meteorological

c y o i t h h ) e

o

c e m l o E c

n

t l s i t

a S r

p u 2 , o

v t r k

t d r t o c h u a e e

t p E e

v a

a d h m i t h o e y n i a n

r t o e e a o l c e h

m n e g

t r

e u i w

u

s a o a e . ) o f l s S i s h r o d e a c n g

n u

n a e e r

r h and Paul r r t t e l

t d n

u a I a o e

n D t s v h i i e

t e

e

a t s n t a

n N n i s n o o

t p h t u d i e p g g n o

s m m i e

u

v e o o f f t ry

h

n I

o u

e c n r l o a r a s R c

r N f r

h e S v p r f a n e r

n c e e d r n

r l d o s

e

r R t l t r n . s p i h e s u

s o a r l l i C , c e i R o

n

d

s

AnteonCorporation,U n e u i N c c t c

o

t u r

a r a d w k e N o m t c e r s a L m g a

n s i o e S e T a o

v C a i t u i c r i e o v l i m o t o m n o o n n i a i s , o n t l n o e f d

s h l i t

t h c n

t n

e r S

r l s a n n e b h r f

d

i b s r e y c g s

u l u o m e u a s e o

d o t d S.

i o m t c

t j s d

o e d a c h

e o t a

o t

u c h c c t

h l l

n s l h i a

l h o p e a p a o u l e a

a

e a o n t e i r r n Roger T. u t

a t a n i e

t

a e

N S u thantheproce a e s f

e , r o p r r r Chang

l t r p t t g t g a

( s

t

i l c e h

f ,

f t l r

d

z i r t

d t N l c a v t o e e

a m e R e i

r t t z

o a t o v e o d a S h e

e c o t

h h e e e i a

e t r

a c r n e h W o p i r also r r b e f t C t b a i ,

w o c

e c e e d o -

n s s o

i e n

y e o W v t d d e n t i z section e t p y l e i r r n c

m S h

t t i

a P r a a r e n . m t e

s e o e n

l i i i

i i a

a w n b ( a h R s y m m n e i w t c R i t s

r r i f c ) n n J

e p d d h n I t h n e n i

i s g e a l e

t

i n , a

y a n a

a c i P a c t a d

i i a t i e

e e Edson m w e

s n - t

y a c i o mprove c i r w

NOAA/NESDIS

r S the tropicaloceans o d g t t r e o a y 0) fromthe r d s a g t s L Q r d y e

d i

d k t f a t

n o a i e e o o

m a

e c e r i c l

u t e e u a r e

)

n s e

i

v l h

o i f

u

r d e d z n

o e

r r s f s e r f l (NRCS) a

r r r c

s S ( r e l m p l r

i o a n ; e i a f

a

d y e

m d

t

a e t M e a l k o

a o a i i r C r C r o r c m n

email: s t

t t W m . a l i o e l n o l S t y s o o e h m i t f . i c a n e of e

d b i o E r

v d o o t

r r s e c r

s c/o n e ssed c e p a i i e e C ,

i a n o s o T i e i k l g e i

A

n t R t

fers n a e

n n i v

niversity e t i d

h h r

g t t t t t t the g s s i

h c h A v e

f n he h e n h h a e e n e h 2 a a c d a s S i e e o s s h o t t a a i i l l r T e o d d e e e n d d g d e 5 n h d s s s s s s y y - r - ) r r - t f l l

patternsfromQuikSCAT d D s f o g 2 p h o g s hours ofthenodaltime. T t The routine me normally t are T (next highest)from wave/wind orientation relative viewangle.Highest returnis Fig. 1 backscatter function n v (brighter) and 3. s T /ORA r h h ofGuam(WERI),Mangilao, a l u c a v r - r i c e a o h h h i i g e e

a o s c h e r e r METEOROLOGICAL ANALYSISWITHNRCS t n t m e e e h

a t u i f

t e y c e r t a a h

e a

d

r s o o e

r

e

NOAA/NESDIS TC p i r m t n o r c e a b e s n a r g e

i r , CampSpringMD s t a r . i o d

e d

h b h t

u e

g r o a t s

a Normalized Radar Cross-Section, l

1 s o n a 3 a o r i

l a a e t i Normalized radarcross i c m t o y i w g w

n i u r u 0 f

s

t i y e o d

s e f c

o a

r k h a r s o -

s i a v t h

c e n e

n s f u k

h m sigma i b e l t s r o a e g o s i n

s s o d m g c

e a o d e 2 n c d h e A r

d

o r s h h

r n g t r a

a n e 5 b g

e a s i signal c a e

f i

i n s d r n n t s

n -

o r d d b t ‘ k s

i p t e k a s i a o

d ( g d a

a a

e v y e p and/ m l s l - y t s r

r a t t a e i p r k s

h 0 s o

c lower(darker) h h t s e w

d

y e o

s

r i

t

n e thesensor(fromLong,2000). d

a e e

s

o b a h

A i

s

v d r t d s u isshowninFig.1. f Q g s

m c c y d e h e p

o i o r d u ’ f

e - i e e r e

c

is v p

g u u a r t A newanalysistoolover u r JPL u i e e 3 w

a o n s

s h

s a r n n i c r p ( e s

t a k 7 e n i

e p towards s t i P

n .

o S a o c n t

v

h a t a

S t - o s

e r l

t

e t e l m u e a torm webpagethenremaps km o e t e

a c a a s , i e C

s t o o r

I r s

y f h f h a l

b g l n o n m

a r

l

f s n A C o , y e y e

v o e

a P u t

n t o i e

s i

a T h

t t y

e c m t d

r g

o a h

w i h a o directionally n p

e e i t g

n i b

a 2 - h n m i f k y i t

v sigma f a section versus v d a a

c

h t h e l 0

r e (highest)oraway w c e s e a

t e n t L r a r t a a t e r

0 h r h i r s h o t

r i i c o

t d e b e g i

i l n a

0 e a

e n c r

a w o s v a u

v l a (

t e o e d s )

e u k

) b h

u a P w v l g e a when the ‘ . s

. v s i w

e s

l

l l e

e r - r i a O h l v a i e y h e o n f 0 i l

n n a v

r a i a O T e r

n

i r However l c

l 2 n

.

g c , u a v

a p t c D d s

w h

d i e d a c i A e h

n e t r f o p a e i B e

i ’ o i i e

A g i a

o

a

d s - the t n p s

r

data a

o h a su dependent n o c a r s A n S t b e s

i o

i c t n i n a a m d r i n

n l g C p r e

f n i e c o bdivides

g o

o e l

u a e g

r r s a o

o o v ).

f

f e g i a s t n u 3 o

n

higher W f o a a u

r which w 6 s e e r

a l , t i

n

t

a s

t a r a n

l

d s

h t t i h y

i T

h n n i k p i t T o c t

a

m n the t t i i i i . n e n g o h h h m d e c h b

C r t o A g e d g e o e n e h 4 e e s s y y . . f

Knowledge of this directional variation and the path of the spacecraft/sensor sub-track/scan geometry along the earth’s surface allow the analyst to deduce the orientation of the wind field. This process is less difficult if the wind speed variation and the rain field orientation are known. Then changes in the gray field can be attributed to the wind field orientation. A comparison satellite image can also aid the analyst. 85h Figure 2 provides an example of a NRCS image analysis over the northeast Pacific over Tropical Storm Alma (01E). In this case, the basic flow is understood, and so a more accurate TC position (especially in the east-west direction) is determined from the intersection of the two bright nodes and the dark band trough axis. The NRCS also allows for subtle refinement in the surrounding wind field by using cross-track (darker) and along-track (brighter) Fig. 3. Super Typhoon Podul (140kt). variation to correct adjoining flow in the ambiguities where the wind speeds and rain are almost equal. 85h 85h IR

a) b) Fig. 4. NRCS views of (a) Super Typhoon Mitag and (b) Typhoon Sinlaku. In each case concentric eyes are evident. Center positions are precisely indicated due to the small calm and rain-free area.

b) Early Stages of TC Development

The clarity of the NRCS in these cases varies with the structure of both the developing TC and the synoptic environment that it is forming in. In most cases, the analyst needs to know the approximate location of Fig 2. NRCS analysis for 27 May 2002, 1240 UTC. where to look; however, it is possible to see the Note orientation of along-track bright nodes near the developing tropical depression at the earliest point of TC Alma’s center, and cross-track dark bands. In its existence. Even if a circulation center is not clearly upper left portion of the analysis, directions originally evident in the scatterometer data, the axis of the light drawn with first guess from the ambiguities were wind (and rain-free) trough often is visible in the corrected to fit the NRCS image. NRCS. In addition, an enhanced wind (and rain) flow pattern is often apparent that develops 3. EXAMPLES asymmetrically along a portion of the trough. See Fig. 5 for an example of a complete analysis, including the a) Intense Tropical Cyclones use of the scatterometer ambiguities and a resulting In this case there is rarely any confusion between the overlay of the analyzed streamlines on to the visual tropical cyclone’s circulation and the environment imagery. One indicator of a developing system is the because the heavy rain and winds coincide. The change in character of the trough (dark) region with small ‘dark’ (low rain and low wind region) eye each successive pass. As the TC develops, the dark provides for very precise positioning of the TC . Here, trough region is seen to shrink and consolidate about the heavy rain pattern around the TC center looks its center. These images may also eventually provide similar to a microwave but often with a smaller central guidance to show the features that are best indicative feature. In some cases other characteristics of the of future development in different types of TC structure are seen such as concentric eyes or an environments (e.g. monsoon trough, TUTT related asymmetric wind field (Figs. 3 and 4). systems, waves in the easterlies…).

IR

Fig. 6. NRCS view of Typhoon Higos over Japan. Local lee side calm regions are indicated in white. IR inset shows little cloud cover over area.

to see through obscuring wind and light rain conditions at high resolution makes it a desirable supplement to the meteorological forecaster's Fig. 5. NRCS analysis over the developing Hurricane repertoire. Although the NRCS image can be more Lili. Streamlines are performed with the help of the difficult to interpret than a standard microwave image, QuikSCAT winds and ambiguities and then overlayed with practice, both small- and large-scale wind and onto a visual image. rain patterns are readily discernable. In many cases it is necessary to use these data in conjunction with b) Other Meteorological Features other conventional data to either aid or focus the analysis. However, as these data are looked at and 1) Extratropical/Subtropical Systems understood, the authors believe that there are many more uses to be developed. For example, an Although often evident from other types of remote automated pattern recognition process could help in sensing imagery, the NRCS offers a unique view of the ambiguity selection of scatterometer winds; thus, the wind field over a large area of the ocean where a improve the use of scatterometer data in both the need may exist for more precise positioning and daily NWP analysis and in TC positioning techniques. character of a particular frontal system, trough, or ridge axis. A view of a vigorous subtropical low Acknowledgments. The authors would like to thank Dr pressure area might, for instance, give an indication Dave Long (BYU) and Dr Tom Fouser (JPL) for their part in of a shrinking central light wind region as it transitions developing this imagery and Jeff Hawkins (NRL) for his into a tropical cyclone. continued support. This research was funded in part by the Office of Naval Research (PE-060243N), and by the 2) Small scale features Oceanographer of the Navy through the program office at the Space and Naval Warfare Systems Command PMW- The character of the 6km images offers a unique view 155 (PE-0603207N). . of some small scale meteorological features that 5. REFERENCES would most likely be missed, or not understood, in Atlas, R., et al.,2001: The Effects of Marine Winds from more conventional data. Such things as lee side lows Scatterometer Data on Weather Analysis. Bull. and down slope and island features are readily Amer. Meteor. Soc., Vol 82, 1965-1990. observable in the NRCS imagery (Fig. 6). Although Edson, Roger T., and J.D. Hawkins, 2000: A these features might also be available in high Comparison of Scatterometer Data over TCs, Proc. resolution visual imagery, NRCS images are available of the 23rd Conference on Hurricanes and Tropical at times when the use of visual imagery is not Meteorology, Fort Lauderdale, FL, 195-196. possible. Long, David, 2000: Point-wise Wind Retrieval Wind Scatterometry Background. A QuikSCAT/Sigma-0 Browse 4. DISCUSSION Product Ver. 2.0, Earth Remote Sensing (MERS), BYU University, Provo, Ut., 16pp. Perry, K.L. (Ed.), 2000: QuikSCAT science data product The NRCS image offers a new and unique tool to user's manual, Ver 2.0. Jet Propulsion Laboratory, analyze the winds on the ocean surface. The ability California Institute of Technology, Pasadena, CA, 90 pp.