METEOROLOGICAL DATA

During the NOA'81 e x p e d i t i o n two independent automatic systems f o r measuring m e t e o r o l o g i c a l parameters were i n s t a l l e d on "Poseidon". The T e f r i m e t (designed by Fa. Theodor F r i e d r i c h s ) system r e c o r d e d dry b u l b , wet b u l b and sea s u r f a c e temperatures, wind speed and d i r e c t i o n and a i r p r e s s u r e w i t h a time i n t e r v a l of one minute.

The new equipment b u i l t from a d e s i g n by Dr. K. U h l i g , Department of M a r i t i m e Meteorology, I f M - K i e l , s t i l l i n the t e s t phase, had the advantage of r e c o r d i n g mean v a l u e s averaged over a predetermined i n t e r v a l . I t had two sensors f o r dry and wet b u l b temperatures and one sensor each f o r wind speed and d i r e c t i o n as w e l l as short-wave downward r a d i a t i o n .

Both d a t a s e t s had l a r g e gaps. T h e r e f o r e t h e p r e s e n t a t i o n here ( f i g . 11.1 - 11.3) i s the best p o s s i b l e combination of d a t a from both systems.

The wind data are o n l y recorded and d i s p l a y e d r e l a t i v e to the s h i p ' s speed and heading.

F i g u r e 11.1 p r e s e n t s the m e t e o r o l o g i c a l d a t a d u r i n g t h e l o n g s e c t i o n B102.

In the f i r s t 3 days of the long s e c t i o n FS " P o s e i d o n " steamed through the r e g i o n of the Azores h i g h p r e s s u r e area w i t h few c l o u d s , r e l a t i v e l y dry a i r and low winds. Steaming through the a n t i c y c l o n e the s h i p passed through r e g i o n s of e a s t e r l y , s o u t h e r l y and w e s t e r l y winds. On the 23rd J u l y the s h i p came i n t o the i n f l u e n c e of s t r o n g e r w e s t e r l y winds, a d v e c t i n g more humid s u b p o l a r a i r . P a s s i n g f r o n t s p r o v i d e d complete c l o u d c o v e r .

F i g u r e 11.2 p r e s e n t s the meteorology measured on the l o n g l e g s of the f r o n t survey. The f i r s t two days the c e n t r e of an a n t i c y c l o n e w i t h a c e n t r a l p r e s s u r e of 1035 hPa was s i t u a t e d 400 km south of the survey r e g i o n . Due t o i t the ship operated under c l o u d l e s s sky, i n dry a i r and s o u t h w e s t e r l y wind.

On the 29th J u l y an occluded f r o n t system a t t a c h e d to a c y c l o n e w i t h c e n t r a l p r e s s u r e of 995 hPa passed over the survey r e g i o n . The wind i n c r e a s e d t o 20 a s "¹ from a s o u t h w e s t e r l y d i r e c t i o n and advected a i r , which a l t h o u g h 2 *C warmer than the l o c a l sea s u r f a c e temperature was h i g h l y s a t u r a t e d w i t h water vapour.

D u r i n g the h i g h r e s o l u t i o n p a r t of the f r o n t survey the c y c l o n e i n t e n s i f i e d t i l l the 2nd August to a c e n t r a l p r e s s u r e of 975 hPa. I t s c e n t r e was s i t u a t e d 900 m i l e s n o r t h of the survey r e g i o n ( f i g u r e 11.3).

During the l a s t two days the wind decreased but s t i l l advected p o l a r a i r c o l d e r than the sea surface temperature on the c o l d s i d e of the f r o n t . Due t o a s t a t i o n a r y f r o n t the area was covered w i t h s t r a t u s clouds.

S e c t i o n B 1 0 2 20

15

10

N O A '81

\

« 1000 r-n

.5 E g 8 500

S e fi

" /î r v

F \ 1 «i i ^¿4

I II!

I A l l ,\ _{. ...A..} ^¿4

21. 22.

10h G M T 0"

23.

0»

24.

0»

_i

25. July 1981 26.

0» Oh

38* 40' 4 5 ' 55°

F i g . i l . l : Wet and d r y b u l b a i r temperature, wind speed and d i r e c t i o n , a i r p r e s s u r e and s h o r t wave i r r a d i a n c e a l o n g the s e c t i o n B102.

S e c t i o n C 3 0 8 A - C 3 1 7 N O A ' 8 1

£ 20

10

£ 360 r

F]

1.1 1801

-ÏE r

1 ,UU. ^{i l'}

* 1020

F~

a 1000

<

, 4 —

« 1 0 0 0 r

I

if . M

31.

0h

1. AUQ. » 8 1 0h

I

2.

0"

3.

0»

4.

0*

5.

0h

11.3: Wet and d r y bulb a i r temperature, wind speed and d i r e c t i o n , a i r pressure and s h o r t wave i r r a d i a n c e d u r i n g the h i g h r e s o l u t i o n p a r t of the f r o n t a l survey.

12. CONCLUSIONS

The experiment NOA'81 was the f i r s t of a s e r i e s of experiments c a r r i e d out w i t h our new measurement system, c a l l e d SEA ROVER.

The SEA ROVER i s an i n t e g r a t e d system measuring hydrography and c u r r e n t s i n the upper boundary l a y e r of the ocean, combined w i t h m e t e o r o l o g i c a l measurements, n a v i g a t i o n and r e a l - t i m e data p r o c e s s i n g , from the moving s h i p , steaming at almost f u l l speed.

We were a b l e to monitor l a r g e areas w i t h h i g h e r h o r i z o n t a l r e s o l u t i o n i n s h o r t e r time than c l a s s i c a l CTD s u r v e y s , the cost being the l i m i t e d depth range and the r e l a t i v e l y l a r g e t e c h n i c a l expense. Real-time data p r o c e s s i n g a l l o w e d a spontaneous adjustment of the survey p a t t e r n a c c o r d i n g to the j u s t measured hydrographic s i t u a t i o n . New problems i n c a l i b r a t i o n , time-constant behaviour and temperature dependence of the sensors were caused by h i g h d i v i n g speeds of the f i s h . The a p p l i e d scheme of r e c a l i b r a t i o n , e d i t i n g and d a t a r e d u c t i o n succeeded i n c o r r e c t i n g some of the e r r o r s i n the measurements. The accuracy was s u f f i c i e n t to r e s o l v e the s t r o n g s i g n a l s i n the upper boundary l a y e r . I n l a t e r experiments (NOA'83) the d i v i n g speed of the f i s h was reduced i n order to a v o i d some of the d e t e c t e d e r r o r s o u r c e s .

The NOA'81 experiment p r o v i d e d a data set of hydrography i n the upper 80 m, s u r f a c e c u r r e n t s and meteorology c o n t i n u o u s l y measured over a d i s t a n c e of 12 Mm. The h i g h h o r i z o n t a l r e s o l u t i o n over long s e c t i o n s span up a s p e c t r a l range of 0.4 - 2500 km, the towing speed of 10 knots improved the s y n o p t i c i t y of the measurements, and the data r a t e of 16 c y c l e s per second r a i s e s t a t i s t i c a l s i g n i f i c a n c e . Repeated surveys of the same t r a c k on r e t u r n t r i p s a l l o w to i n v e s t i g a t e temporal changes.

With the use of i s o p y c n i c a n a l y s i s we were a b l e to d i s c r i m i n a t e oceanic f i n e s t r u c t u r e from i n t e r n a l waves. For example the p r e s e n t a t i o n of temperature on s u r f a c e s of constant oj. show c l e a r l y the e x t e n s i o n of d i f f e r e n t water masses and thus e d d i e s , meanders, tongues and f r o n t s are d e t e c t a b l e .

A v e r a g i n g o v e r a l a r g e number of data samples improved the s i g n a l to n o i s e r a t i o and i n c r e a s e d the s t a t i s t i c a l s i g n i f i c a n c e . These s t a t i s t i c a l r e s u l t s can be used f o r the t e s t of models or the comparison w i t h c l i m a -t o l o g c i a l d a -t a .

The h i g h h o r i z o n t a l r e s o l u t i o n r e v e a l s new i n s i g h t s i n the l a r g e - s c a l e s t r u c t u r e of l o n g s e c t i o n s i n t e r s e c t i n g the s t r e a m l i n e s of the s u b t r o p i c a l

g y r e . Large r e g i o n s of r e l a t i v e l y homogeneous T-S r e l a t i o n s h i p a l t e r n a t e w i t h narrow bands of s t r o n g h o r i z o n t a l g r a d i e n t s . The t r a n s i t i o n zone between the s u b t r o p i c a l warm water and the s u b a r c t i c water extends over 700 km. The t r a n s i t i o n s themselves are found mainly at f o u r s t r o n g f r o n t s not broader t h a n 50 km each. The i n t e r m e d i a t e r e g i o n s o n l y show mesoscale v a r i a b i l i t y l i k e the waters near the Azores or n o r t h of the P o l a r F r o n t . The h o r i z o n t a l p a t t e r n s d i f f e r a l s o v e r t i c a l l y . While water mass changes i n the s e a s o n a l

t h e r m o c l i n e occur n e a r l y s t e p l i k e , h o r i z o n t a l g r a d i e n t s i n the mixed l a y e r a r e much weaker and o f t e n are p h a s e - s h i f t e d compared to the s t r u c t u r e i n the t h e r m o c l i n e . Thus the mixed l a y e r masks the p a t t e r n of the u n d e r l y i n g w a t e r , a r e s u l t which may be important f o r remote s e n s i n g . At the P o l a r F r o n t between 50° N and 52° N s y n o p t i c - s c a l e meanders w i t h wave-lengths of about 200 km have been observed. The s t r u c t u r e s d e t e c t e d i n the h y d r o g r a p h i c d a t a show s t r o n g s i m i l a r i t i e s w i t h the s u r f a c e c u r r e n t s on s c a l e s l a r g e r than 20 km. The l a c k of h o r i z o n t a l r e s o l u t i o n i n the n a v i g a t i o n data hindered us from comparing hydrogaphy and c u r r e n t measurements on s m a l l e r s c a l e s . Improvement of the n a v i g a t i o n system i s t h e r e f o r e necessary f o r the i n v e s t i g a t i o n of s t r u c t u r e s l i k e the t h e r m o c l i n i c i t y maximum which was l e s s than 10 km w i d e .

13. REFERENCES

Baumgartner, A. and E. R e i c h e l , 1975: The World Water Balance.

E l s e v i e r , Amsterdam, 179 pp.

Bauer, J . and J.D. Woods, 1984, I s o p y c n l c A t l a s of the North A t l a n t i c Ocean.

B e r . I n s t . f . Meereskunde K i e l , Nr. 132, 173 pp.

B r e t h e r t o n , F., R.E. Davis and C.B. Fandry (1976): A technique f o r o b j e c t i v e a n a l y s i s and design of océanographie experiments a p p l i e d t o MODE-73.

Deep-Sea Research, 23, 559-582.

Budyko, M.I., 1974: Climate and L i f e .

I n t e r n a t i o n a l Geophys. S e r i e s , V o l . 18, Academic P r e s s , London, 508 pp.

C o l l i n s , D.S., R.T. P o l l a r d and S. Pu, 1983: Long Sea Soar CTD s e c t i o n s i n the n o r t h e a s t A t l a n t i c Ocean c o l l e c t e d d u r i n g RRS " D i s c o v e r y " C r u i s e 116.

I n s t i t u t e of Océanographie S c i e n c e s , Report No. 148, 77 pp.

D e s s u r e a u l t , J.G., 1976: " B a t f i s h " . A depth c o n t r o l l a b l e towed body f o r c o l l e c t i n g océanographie d a t a .

Ocean E n g i n e e r i n g 3, 99-111.

Dettmann, E., 1981: Konzeption, G e s t a l t u n g und Anwendung e i n e s ozeano-g r a p h i s c h e n Schleppsystems.

Ph.D. T h e s i s , U n i v e r s i t y of Hannover.

D i e t r i c h , G., 1969: A t l a s of the Hydrography of the Northern North A t l a n t i c Ocean.

C o n s e i l I n t e r n a t i o n a l pour l ' E x p l o r a t i o n de l a Mer, S e r v i c e Hydro-graphique, C h a r i o t t e n l u n d S l o t - Denmark, 140 pp.

D i e t r i c h , G., K. K a l l e , W. Krauss and G. S i e d l e r , 1980: General Oceanography.

An I n t r o d u c t i o n . 2nd e d i t i o n ( t r a n s l a t e d from German), John-Wiley, New York, 626 pp.

F i s c h e r , J . , H. Leach and J.D. Woods, 1985: S y n o p t i c - s c a l e s t r u c t u r e s i n the seasonal thermocline a t the North A t l a n t i c P o l a r F r o n t ,

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

F i s c h e r , J . , C. Meinke, P . J . M i n n e t t , V. Rehberg and V. S t r a s s , 1985:

A d e s c r i p t i o n of the I n s t i t u t für Meereskunde Schleppfisch-System.

T e c h n i s c h e r B e r i c h t Nr. 1 der Abt. Regionale Ozeanographie des I n s t i t u t s für Meereskunde, K i e l , 2. A u f l a g e .

H a r d t k e , P.G. and J . Meincke, 1984: K i n e m a t l c a l i n t e r p r e t a t i o n of i n f r a r e d s u r f a c e p a t t e r n i n the North A t l a n t i c .

Oceanologica A c t a 7 ( 3 ) , 373-378.

Horch, A., 1984: Eine Beschreibung d e r NOVASoftware für S c h l e p p f i s c h -Experimente.

T e c h n i s c h e r B e r i c h t N r . 5 d e r Abt. Regionale Ozeanographie des I n s t i t u t s für Meereskunde, K i e l , 2. A u f l a g e .

Isemer, H.-J. and L. Hasse. 1985: The Bunker c l i m a t e a t l a s of the N o r t h A t l a n t i c Ocean. V o l . 1 : O b s e r v a t i o n s , S p r i n g e r V e r l a g , H e l d e l b e r g , New Y o r k , Tokyo. V o l . 2: ( i n p r e p a r a t i o n ) .

J e n k i n s , G.M. and D.G. Watts, 1968: S p e c t r a l A n a l y s i s and i t s a p p l i c a t i o n s . Holden-Day, pp. 525.

K r a u s s , W. and R. Käse, 1984: Mean c i r c u l a t i o n and eddy k i n e t i c energy i n the e a s t e r n North A t l a n t i c .

J . Geophys. Res. 89, 3407-3415.

K r a u s s , W. and J . Meincke, 1982: D r i f t i n g buoy t r a j e c t o r i e s i n the N o r t h A t l a n t i c C u r r e n t .

N a t u r e , 296, 737-740.

K r e y s z i g , E., 1965: S t a t i s t i s c h e Methoden und i h r e Anwendungen.

Vandenhoeck & Ruprecht, Göttingen, p. 422.

Leach, H., 1984: E i n e Beschreibung des w i s s e n s c h a f t l i c h e n N a v i g a t i o n s s y s t e m s des PS "Poseidon".

T e c h n i s c h e r B e r i c h t N r . 2 d e r Abt. Regionale Ozeanographie des I n s t i t u t s für Meereskunde, K i e l , 2. A u f l a g e .

Leach, H., 1985: The a n a l y s i s of c u r r e n t s measured from a moving s h i p i n the r e g i o n of the N o r t h A t l a n t i c P o l a r f r o n t ,

( s u b m i t t e d t o Deep-Sea R e s e a r c h ) .

Leach, H., P . J . M l n n e t t and J.D. Woods, 1985: The GATE L a g r a n g i a n B a t f i s h Experiment.

Deep-Sea Res. 32, 575-597.

Meincke., J . and A. Sy, 1983: L a r g e - s c a l e e f f e c t s of the M i d - A t l a n t i c Ridge on the N o r t h A t l a n t i c C u r r e n t .

ICES Report, C.M./C:8, 10 pp.

Onken, R., R. B l e c k and J.D. Woods, 1986: Two-dimensional model o f mesoscale f r o n t o g e n e s i s . ( i n p r e p a r a t i o n ) .

Robinson, M.K., R.A. Bauer and E.H. Schroeder, 1979): A t l a s of North A t l a n t i c - I n d i a n Ocean monthly mean temperatures and mean s a l i n i t i e s of the s u r f a c e l a y e r .

U.S. Naval Océanographie O f f i c e Ref. Pub. 18, Washington D.C.

Woods, J.D., 1985: The p h y s i c s of thermocline v e n t i l a t i o n .

I n J . C . J . N i h o u l ( E d i t o r ) , Coupled Ocean-Atmosphere Models. E l s e v i e r , Ams t e r dam.

Woods, J.D., H. Leach and P. M i n n e t t , 1981: The GATE Lagrangian B a t f i s h Experiment.

B e r . I n s t . f . Meereskunde K i e l , Nr. 88 and N r . 89.

Woods, J.D. and P . J . M i n n e t t , 1979: A n a l y s i s of mesoscale t h e r m o c l i n i c i t y w i t h an example from the t r o p i c a l thermocline d u r i n g GATE.

Deep-Sea Res. 26A, 85-96.

Sy, A.,1985: An a l t e r n a t i v e e d i t i n g technique f o r océanographie d a t a . Deep-Sea Res. ( i n p r e s s ) .

14. APPENDIX

14.1 Coefficients f o r sensor c a l i b r a t i o n

2

y = a + a,x + a„x

o 1 I

x: raw d a t a v a l u e y: c a l i b r a t e d v a r i a b l e

MS38 a

o ^a l ^a2

P -3.097345 X 10 ² 3.653411 X 10 ^{- 2} 8.021386 X -9

10

T Sensor 1 -2.441963 X 1

10 2.425639 X 10 ^{- 3} 2.444443 X -10

If

₂ -2.503945 X 1 10

10 2.420168 X 10 ^{- 3} 2.756392 X -10 10

C " 1 -2.644104 X 1

10 3.399403 X 10 ^{- 3} 3.781636 X -9 10

c "

² -2.702129 X 1

10 3.460328 X 10 ^{- 3} 2.303073 X -9 10

MS39 a

o ^al a2

P -2.8495911 X 10 ² 3.7115809 X 10 ^{- 2} 3.213433 X 10 ^{- 9}

T Sensor 1 -2.488925 X 1

10 2.439146 X 10 ^{- 3} 3.5183501 X 10 ^{- 1 2}

2 -2.4189148 X 1

10 2.4221177 X 10 ^{- 3} -9.9700212 X 10 ^{- 1 1}

c "

^{1 -2.713648} X 1

10 3.452988 X 10 ^{- 3} 2.507046 X -9 10

C " 2 -2.553158 X 1

10 3.249933 X 10 ^{- 3} 3.663812 X -9 10

14.2 Coefficients f o r c a l i b r a t i o n correction of s a l i n i t y

S = a + a,S

c o l

S: C T D - s a l i n i t y S - c o r r e c t e d s a l i n i t y

a

o ^al

S Sensor 1 S Sensor 2

0.4861705987 0.3668513607

0.9848659552 0.9860728478

14.3 Coefficients for pressure calibration correction

P = P + a + a.Tu c o 1 P : c o r r e c t e d p r e s s u r e value

c

P : CTD-pressure

Tu: 4-hour mean of upper t u r n i n g p o i n t temperature a = 5.79 lO^Pa

o

a, = -0.1212 l O ^ P a K^{- 1}

Im Dokument 3D1 I iTH-'EeR- m (Seite 148-159)