A compilation of current and temperature data from moored instruments during INDEX 1979, RRS "Discovery"

A COMPILATION OF CURRENT AND TEMPERATURE DATA FROM MOORED INSTRUMENTS DURING INDEX 1979,

RRS DISCOVERY

D.R. OUADFASEL

DATA REPORT 19 1980

INSTITUTE OF aCEAIMOQRAPHIC SCIENCES

%

\

INSTITUTE OF OCEANOGRAPHIC SCIENCES

Worm ley, Godalming, Surrey, GU8 SUB.

(0428 - 79 - 4141)

(Director: Dr. A.S. Laughton)

Bidston Observatory, Birkenhead,

Merseyside, L43 7RA. (051 - 653 - 8633)

Crossway, Taunton,

Somerset, TA1 2DW. (0823 - 86211)

(Assistant Director: Dr. D.E. Cartwright) (Assistant Director: M.J. Tucker)

On citing this report in a bibliography the reference should be followed by the words UNPUBLISHED MANUSCRIPT.

A COMPILATIOJ OF CURRENT AND TEMPERATURE DATA FROM MOORED INSTRUMENTS DURING INDEX 1979,

R.R.S DISCOVERY

D.R. QUADFASEL

Data Report: 19

1980

1

As part of the Global Weather Experiment (FGGE) a multiship oceanographic survey

of the western Indian Ocean was carried out between March and September 1979. The

general aim of this experiment and some preliminary results have been described by

Swallow (1980). The British contribution to INDEX was a two month cruise of RRS

Discovery between 10 May and 6 July 1979 (I.O.S. cruise report, No. 83, 1979) .

Besides the ship-board measurements an array of four current meter systems was

moored off the Somali coast in water depths between 3300 and 4500 m for just over

one month. The self-recording instruments were deployed at nominal depths of 200,

500, 700 and 2000 m which were chosen in relation to the levels of the westward

equatorial jets (Luyten and Swallow, 1976). The observed mean depths of

instru-ments were however some 100-200 m greater than intended. In this report

oceano-graphic data obtained with the moored instruments are presented in a oceano-graphical form.

Basic statistics are also given. Some preliminary results on the kinematics of the

Somali Current system based on these observations have been published by Schott and

Quadfasel (1980).

The four moorings (272-275 in Fig. 1) contained four Aanderaa RCM-4 current

meters each, except for 275 (only 3 c.m.). The moorings were taut wire systems

with a steel sphere 10 m above the top instrument as the only buoyancy. Only 275

had additional back-up buoyancy above the acoustic release system.

The accuracy of the Aanderaa current meters as specified by the manufacturer are

+ 2% for the speed value, _+ 2 degrees for direction, H- 0.1°C for temperature and

2 dbar for pressure.

Most of the instruments deployed had a 100% data return, the amount of spiky

values which had to be replaced by linear interpolation between neighbouring values

was less than 1%. Only on three current meters severe problems occured reducing

the quality of data substantially:

(a) Mooring 273 (417 m) ;

The rotor was lost after 11 days of recording on 2 June. For the

analysis and plots of this record an artificial constant speed of

15 cm/s was used during the second half of the record to show at

least the directional signal.

(b) Mooring 2 73 (2198 m) :

The compass of this instrument was cut short for altogether 25% of

the recording time. Single gaps were up to 5 hours long and occured

more frequently at the end of the recording time. These gaps were

linearly interpolated between neighbouring values. For analysis of

used, however, in the long periodic fluctuations (>2d) the errors

are negligible.

(c) Mooring 275 (2142 m):

The magnetic tape was not decodable due to a slipping capstan in

the recording unit. The record is completely lost.

No attempt has been made to correct the recorded current speeds and directions

for horizontal mooring motion. Some statistical information about the records is

given in Table 1, the data are also presented graphically in different ways, using

the following abbreviations:

U - East component of current, cm/s

V - North " " " cm/s

T - Temperature °C

P - Pressure dbar

1. U,V,T,P as time series.

All time series are based on 1 hourly mean values. They are presented

as deviations from the overall mean which is indicated on the left of

the zero-line in each case.

2. U,V combined to progressive vector diagrams.

The plots are based on 1 hourly mean values, tickmarks are every day.

3. U,V combined for stickplots.

The time series of 1 hourly mean values was low pass filtered and

every sixth value is presented. Filter type: Lanczos taper, half

power frequency 30 h. No. of weights: 30, Amplitude reduction at

24.8 h: 0.26, at 12.4 h: 0.01.

4. The statistics given in Table 1 are based on 1 hourly mean values.

ACKNOWLEDGEMENTS

The help of Mr I. Waddington and captain and crew of RRS Discovery during

deploy-ment and retrieval of the moorings is highly appreciated.

REFERENCES

I.O.S. Cruise Report No. 83, 1979. Physical oceanographic studies in the western

equatorial Indian Ocean: a contribution to the FGGE oceanographic programme.

Luyten, J.R. and J.C. Swallow, 1976. Equatorial undercurrents. Deep-Sea Res. 23,

999-1001.

Schott, F. and D.R. Quadfasel, 1980. Development of the subsurface currents of

3

Swallow, J.C., 1980. Response of the western Equatorial Indian Ocean to the

monsoon winds: observations during the Global Weather Experiment,Science,

Table la

MOORING NO.: 272 BOTTOM D E P T H : 2*21 5 m

POSITION: jg) = 2°00.2'N ^ = 2i8°02.7'E

START: 17.05. 1979, 16.00 G M T STOP: 1 9 . 0 6 . 1979, O7.OO GMT = 10 m i n

D E P T H

(m)

PAR M E A N V A R I A N C E STD

DEV. M I N M A X

VECTOR M E A N

DIR

M E A N INSTR

3 0 5 u . 8 9 2 6 . 6 9 5 . 1 7 - 1 4 . 7 5 11 . 9 3 2 . 2 2 1 5 6 . 3 A-VTP

V = 2 .02+ 2 5 . 9 6 5 . 0 9 - 1 2 * . 2 6 1 2 . 0 4

T 11 . 7 7 . 0 2 . 1 2 , 11 .2*3 1 2 . 2 3

P 3 0 5 . 1 9 . 6 3 . 1 3 0 0 . 1 3 1 4 . 3

6 0 7 u 9 . 2 6 62*. 8 5 8 . 0 5 - 1 7 . 2 3 3 0 . 5 0 1 2 . 6 5 4 7 . 0 A - V T V 8 . 6 2 3 2 . 0 5 5 . 6 6 - 2 . 6 5 2 4 . 4 1

T 8 . 8 9 . 0 2 . 1 3 8 . 6 6 9 . 5 0

8 5 9 U _{- . 3 9} 1 5 . 9 0 3 . 9 9 - 1 3 . 9 5 1 0 . 0 7 1 . 9 5 3 4 8 . 4 A-VT

V 1 . 9 1 3 1 . 9 4 5 . 6 5 - 9 . 2 7 1 7 . 8 7

T 7 . 5 9 . 0 2 . 1 2 7 . 2 2 * 8 . 1 0

2 1 6 6 U - 2 . 8 1 1 7 . 6 7 24.20 - 1 2 . 1 5 7 . 4 7 3 . 7 7 2 2 8 . 3 A - V T

V - 2 . 5 1 1 2 . 4 7 3 . 5 3 -10.74 9 . 2 2

Table lb.

MOORING NO.: 273 BOTTOM D E P T H ; 3851 m

POSITION: 0 = 3°57.2'N ?V = 5 0 * 0 3 . 3 E

START: 21.05.1979, 13 . 0 0 G M T STOP: 22.06.1979, 12.00 GMT A t = 10 m i n

REMARKS; TOP I N S T R . ROTOR L O S T O N 2 J U N E

DEEP INSTR„ PARTLY COMPASS SHORT C U T

DEPTH (m)

PAR M E A N V A R I A N C E STD

DEV„ M I N M A X

VECTOR M E A N

DIR

M E A N INSTR

U 2 . 1 6 128.91 1 1 . 3 5 - 1 8 . 9 6 1 4 . 9 9 2 . 6 0 _{1 2 3 . 9} A - V T P V - 1 . 4 5 3 8 . 7 3 6 . 2 2 - 1 4 . 9 6 1 2 . 8 7

T 10.52 .18 .43 9 . 6 5 1 1 .82

P 4 1 6 . 0 2 5 3 5 , 5 5 0 . 4 3 7 6 . 2 5 6 6 . 9

U * - 7 . 8 9 1 2 . 9 1 3 . 5 9 - 1 8. 9 6 . 7 5 7 . 9 1 2 6 7 . 0

V * -.41 1 9 . 7 8 4 . 4 5 - 1 2 . 5 9 1 2 . 8 5

6 5 7 U 2 . 8 3 1 0 3 . 7 8 1 0 . 1 9 - 1 6 . 4 9 2 3 . 5 4 3 . 6 9 50. 1 A - V T V _{2 . 3 7} 3 0 . 9 3 5 . 5 6 - 1 2 . 6 1 1 7. 0 2

T _{9 . 3 9} . 0 5 . 2 1 8.54 9 . 8 1

9 0 1 U 2 . 5 5 1 0 2 . 5 3 1 0 . 1 3 - 1 7 . 2 7 2 3 . 3 5 4 . 5 9 3 3 . 7 A - V T V _{3 . 8 3 4 7 . 7 2} 6 . 9 1 - 1 1 . 7 5 2 6 . 8 2

T 8 . 2 0 . 2 5 . 4 9 6 . 6 1 9 . 0 9

2 1 9 8 U 5 . 4 6 8 . 7 3 2 . 9 5 - 4 . 2 1 1 3 . 5 9 1 0 . 6 9 3 0 . 7 A - V T

V 9 . 1 9 3 9 . 6 7 6 . 3 0 - 7 . 2 0 21 .97

T 2 . 2 2 . 0 0 4 . 0 6 2 . 0 7 2 . 3 2

Table 1c.

MOORING NO. : 27k BOTTOM DEPTH: h5k'2. m

POSITION: 0 = 5''^0.7'N 50" 23. 8'E

START: 2 5 . 0 5 . 1 9 7 9 04.00 G M T STOP: 2 5 . 0 6 . 1 9 7 9 09.00 GMT /v t = 10 m i n

STD '

M I N M A X V E C T O R DIR INSTR

DEPTH (m)

PAR M E A N V A R I A N C E

DEV. M I N M A X M E A N M E A N INSTR

DEPTH (m)

3 5 7 U 1 . 1 8 5 8 . 0 5 7 . 6 2 - 1 3 . 5 2 21 . 2 5

1 . 2 9 6 6 . 3 A - V T P

V . 5 2 3 5 4 . 5 8 1 8 . 8 3 - 2 5 . 0 9 41 . 8 5 1 . 2 9 6 6 . 3

T 1 1 . 5 7 . 4 9 . 7 0 9 . 8 7 1 2 . 9 9

P 3 5 6 . 6 1 8 2 2 . 3 4 2 . 7 3 0 0 . 9 4 6 8 . 8

651 U 6 . 0 0 1 6 9 . 5 5 1 3 . 0 2 - 1 8 . 4 5 3 2 . 9 2

7.45 1 2 6 . 2 A - V T

V - 4 . 4 0 4 4 8 . 2 4 2 1 . 1 7 - 3 3 . 0 1 4 0 . 1 3 7.45

T _{9 . 7 5} . 2 4 . 4 9 8 . 5 0 1 0 . 9 5

9 0 9 U - 2 . ] 2 1 7 2 . 4 5 1 3 . 1 3 - 2 6 , 6 8 2 8 . 7 7

2 . 3 4 2 7 8 . 2 A - V T

V .33 1 9 2 . 9 9 1 3 . 8 9 - 3 2 . 9 1 3 0 . 2 6 2 . 3 4 2 7 8 . 2

T 8 . 0 4 . 4 2 . 6 5 6 . 5 5 9.45

2204 U - 4 . 3 2 3 2 . 8 0 5 . 7 3 - 1 3 . 8 8 7 . 8 6

4 . 46 255.4 A - V T

V - 1 . 1 2 2 7 . 0 2 5 . 2 0 -12.53 10.44 4 . 46 255.4

T a b l e Id.

M O O R I N G NO.: 275 BOTTOM DEPTH 3335 m

POSITION; 0 = 7°17.8'N X = 50''39.22'E

START; 28.05.1979, 06.00 GMT STOP: 28.06.1978 13.00 GMT At = 10 m i n

REMARKS: T A P E OF D E E P INSTR. N O T D E C O D A B L E

D E P T H (m)

PAR M E A N V A R I A N C E STD

DEV. M I N M A X

VECTOR M E A N

DIR

M E A N INSTR

2 6 7

8 2 0

U V T P U V T

- 1 . 0 6 5 . 6 9 1 3 . 2 9 2 6 7 . 4

- 4 . 6 7 - . 1 2

9 . 1 7

7 9 . 8 0 2 0 8 . 8 9

.57

1 4 9 5 . 6 2 3 0 . 3 7

8 5 . 9 0 . 2 2

8 . 9 3 1 4 . 4 5 . 7 5 3 8 . 7 1 5 . 1 8

9 . 2 7

.47

- 2 1 . 8 2 - 1 6 . 4 9 1 1 . 2 3 2 4 1 . 6 - 3 5 . 0 0 - 2 4 . 7 9 7 . 6 6

2 0 . 3 3 5 0 . 5 2 1 5 . 0 5 4 0 9. 5

4 6 , 0 1

18.45

1 0 . 1 3

5 . 7 9

4 . 6 7

3 4 9 . 5

2 6 8 . ^

A-VTP

47° E

1 6 5 1 9 7 9 O D O M T 2 2 5 .

1 6 3 1 9 7 9 O D G M T 2 2 6

U=0.89 0

9.26

-0.39

- 2 8 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

2 7 2 - U

z=305m

1 1 1 1 1 1 1 1 1 _{1 1 1 1 M 1 1}

L R.I • HJII

n _{(fMliyifMMMIflllll}

607

ffTiur' " V f F V ^ '

iMiA 1 Uklnii f

859

- f\|WvyM\/i

2166

1 1 1 1 1 1 H=4215

1 1 1 1 1 1 1 1 1 1 11 1 11 1 1 1 1 1 1 1 1 1 1 1

v = - 2 I W 0

&62

1.91

- 2 51

M 1 1 1 1

Vll,

M M 1 1 1 1 1 2 7 2 - V

111111111

A l & i l W W

1 1 1 1 1 1 1 1

W L i W - V \ ,

- » A A

'flKMrfVW;

111111 111111111 1 1 1 1 1 1 1 1 1 11111111

Fig. 2 Variation of east - (u) and north - (v) component of current from

their mean value at position 272 (see Fig. 1). H = bottom depth

10

u - 2 . t 6 0

2 83

2.55

5.46

H - 1 1 11 1 11 1 1 •

P 2 7 3 - U

z»416m

1 1 1 1 1 1 1 1 1

iir

I 1 1 1 M 1 M H

-657

vJ1

l l l l f i i W

901 j A w

-2198

k yV| _ \ f W V

H=3851

H - 111111111 111111111 111111111 h

H

-v = -l,45 0

2.37

3.83

9.19

1 1 1 1 1 1 1 1 1 1 1 1

2 7 3 - V

1 1 1 1 1 1 1 1 1

111

1 1 1 1 1 1 1 1 1 H

-i. 1 lAt

' " 'II'

i

p ( f | i i'

I

H - 1 1 1 1 1 1 1 1 1 111111111 • 111111111 1 11

11

0 = 1.18 0 •

6.00

-2.32

-4.32

H 1 1 1 1 1 1 -H 1 1 1 1 1 1 1

2 7 4 - U

z=357m

/ V

ft 1 1 1 1 1 1 1• ' 1 1 1 1 1 1

K ii/

/f Tf

V t

651 mf

,, ,rV

f w

V

uAu;

y

"

909 y

wii l y

f\i/r

2204 J

1-1 1 1 1 1 1 1 HM542

1 1 1 1 1 1 1 1 1 1 M l

1 1 1 1 1 1 1 1 1 1111 n

v-0.52 0

-4.40

0.33

-1.12

I l i u m 1 1 1 1 1 1 1 1 H

2 7 4 - V

11111IIII

y

i /

'/IIP

V

1

111II1II 111111II1

'y

• 1111111II 1II11 1

12

2 7 . 5 1 9 7 9

00 GM! (6. 116 216

1 I t I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

u = -106 0

- 4 67

I I I I I

2 7 5 - U

z= 267 m

820

H=3335

I I I I I I I - l - f I I I I I I I I I I I I I I I I I I

2 7 5 1 9 7 9

00 GMT 16

V" 5 69 0

- 0 1 2

M i l l - 1 1 1 1 1 I I 1 H

2 7 5 - V

-11 I I 1 1 1 1 1 1 1 1 1 1 ! 1 1 1

y

lAi'in. "ii ilJl

' V

M i l l

p \ l w

I I 1 I I I I I I

llffllf r ^

1 1 1 1 1 1 I I I - 1 I I I I 1 1 I I

13

16 5 1 9 7 9 0 0 G M T 22 5 - 1 0 0

- 5 0

p=305.1 0

T=11.77 0

8.89

759

2.53

111111 1 1 1 1 1 1 1 1 1

272-?

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

— 2 7 2 - T _z»305m

607

859 iWyvvv"

2166

1 1 1 1 1 1 H=42t5

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Fig. 6 Variation of pressure (p) and temperature (T) from their nrean

value at position 272 (see Fig. 1). H = bottom depth, z =

instrument depth, p = mean value of p, T = mean value of T.

2051979

O O C M T 2 2 )

p = 416,0 0

T . 1 0 5 2 0

9.39

8.20

222

H- 1 1 1 1 1 1 1 1 1

272-?

1 1 1 1 1 1 1 1 1

-VWVWVAM/VVIAIIM/I

1 1 M 1 M 1 1

-H-- \

272-1

z = 416m

''I'll

(

-657

''^^•^'Wvvvv/vvv^

_rtt

901

"•iVvvpvvifWr^ wv

2198

H-H=385t

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 111111111

14

0 0 G M T 1 6

8.04

2.44

M M 1 1 M 11111 1111

274-P

1 1 1 1 1 1 1 1 1 1 1 1 1 1

1-274-T z = 357m

i i n

JIAttM

651

' IV

il U/tltfl

909

1. A

2204

1111111 1 H M 5 4 2

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 M 1

Fig. 8 Variation of pressure and temperature at position 274 (see Figs. 1,5)

2 7 5 1 9 7 9

00 GMT 16

p=2674 0

T'13.29 0

9.17

M i l l 1 1 1 1 1 1 1 1 1

275-P

I I 1 1 1 1 1 1 1 1 I I 1 1 1 1 1 1

V

- /

tv

J

-\A/

1 I I I I

I r

H=3335

1 1 I I 1 1 1 1 1 ^ . y x / T n t l "

1 M 1 1 1 I I 1 1 1 1 1 1 1 1 I I

15

272

>8.05.1979

305 m

'N

2166

273

22.05.1979 274 _26.05.1979

416

901

909

2198

275

29.05.1979

2198

I I I I I

300km

100 200

274 and 275 Station No. Fig. 10 Progressive Vector diagrams for positions 272, 273,

(see Fig. 1). Tickmarks are every day 0000 GtfT.

and date of first tickmark are given on top of each column.

16

1 1 1 1 1 1 272

z= 305m

1 1 1 1 1 M 1 1 M M M 1 1 1 M 1 1 M M 1

607

'dWiuikk

859 l i i i i

2166 H=42I5

1 1 1 M 1 1 1 1 1 1 1 M 1 1 1 1 1 1 1 1 1 M 1 1 1 6 . 5 1 9 7 9 2 2 . 5 .

O O G M T 0 ( m / \ 5 0 1 I I I I I

Fig. 11 Stickplots of low pass filtered currents at position 272, Half power frequency : 30 hours, H = bottom depth, z = instrument depth. North is upwards.

I I I I I I I I I

z=416m

I I I I I I I I I

I

-I -I -I -I -I -I -I I I

m i s s i n g

T n

\r-657

901

H " 3 8 5 1

I I I M I I I 2 2 . 5 .

2 0 . 5 1 9 7 9 0 . 0 G M T

17

274

z=357m

2204

mumA'mm.

H=4542

I I I I I I I I _{I I I I I I I I I}

2 4 . 3 . 1 9 7 9 1 . 6

OX) GMT 0 cm/» 5 0

Fig. 13 Stickplots of currents at position 274 (see Figs. 1,11)

I I I I I

275

z" 267m

M I I I I i I I I I I I I I I I M I I M I I I I I I I

H.3J35

Ml M I I I I I I I I I M ( I t t I I I t 1 I >

\\\llllml/A

' ' ' M i I I I I 2 7 5 1 9 7 9 1.6.

0 0 G M T 0 c m / s 5 0