u.s. DEPARTMENT OF COMMERCE

Rogers· C. B. Morton. Secretary

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

Robert M. White, Administrator

ENVIRONMENTAL RESEARCH LABORATORIES

Wilmot N. Hess, Director

NOAA TECHNICAL REPORT ERL 363-GLERL 8

(GLERL Contribution No. 61)

Large-Scale Current Measurements

in Lake Superior

PETER W. SLOSS

JAMES H. SAYLOR

BOULDER, COLO.

January 1976

For sale by the Superintendent of Documents,U. S. Government Printing Office, Washington, D. C. 20402
I

l,

NOTICE

The NOAA Environmental Research Laboratories do not

approve, recommend, or endorse any proprietary product or

proprietary material mentioned in this publication. No

reference shall be made to the NOAA Environmental Research

Laboratories, or to this publication furnished by the NOAA

Environmental Research Laboratories, in any advertising or

sales promotion which would indicate or imply that the NOAA

Environmental Research Laboratories approve, recommend, or

endorse any proprietary product or proprietary material

mentioned herein, or which has as its purpose an intent to

cause directly or indirectly the advertised product to be

used or purchased because of this NOAA Environmental Research

Laboratories publication.

ii
CONTENTS

ABSTRACT

1. INTRODUCTION

2. DATA COLLECTION AND TRANSLATION

3. RESULTS

3.1 Summer Circulation - 1967

3.2 FWPCA Observations - Summer 1967, Summary

3.3 CCIW Observations - Summer 1973

3.4 Oscillatory Currents at Isle Royale

3.5 FWPCA Observations - Winter 1966-67

4. REFERENCES

iii

Page

1

1

2

5

5

23

23

42

43

48
FIGURES

Figure 1. FWPCA 1967 summer mooring sites.

Figure 2. CCIW 1973 summer mooring sites.

Figure 3a. (lWPCA) half-month average current vectors,

16-31 May 1967, 10 and 30 m.

Figure 3b. (FWPCA) half-month average current vectors,

16-31 May 1967, 15, 22, and 60 m.

Figure 4a. (FWPCA) half-month average current vectors,

1-15 June 1967, 10 and 30 m.

Figure 4b. (FWPCA) half-month average current vectors,

1-15 June 1967, 15, 22, and 60 m.

Figure Sa. (FWPCA) half-month average current vectors,

16-30 June 1967, 10 and 30 m.

Figure 5b. (FWPCA) half-month average current vectors,

16-30 June 1967, 15, 22, and 60 m.

Figure 6a. (FWPCA) half-month average current vectors,

1-15 July 1967, 10 and 30 m.

Figure 6b. (FWPCA) half-month average current vectors~

1-15 July 1967, 15, 22, and 60 m.

Figure 7a. (FWPCA) half-month average current vectors,

16-31 July 1967, 10 and 30 m.

Figure 7b. (FWPCA) half-month average current vectors,

16-31 July 1967, 15, 22, and 60 m.

Figure 8a. (FWPCA) half-month average current vectors,

1-16 August 1967, 10 and 30 m.

Figure 8b. (FWPCA) half-month average current vectors,

1-16 August 1967, 15, 22, and 60 m.

Figure 9a. (FWPCA) half-month average current vectors,

16-31 August 1967, 10 and 30 m.

'Figure 9b. (FWPCA) half-month average current vectors,

16-31 August 1967, 15, 22, and 60 m.

Figure lOa. (FWPCA) half-month average current vectors,

1-15 September 1967, 10 and 30 m.

iv

Page

3

4

6

7

8

9

11

12

13

14

15

16

17

18

19

20

21
FIGURES (continued)

Figure lOb. (FWPCA) half-month average current vectors,

1-15 September 1967, 15, 22, and 60 m.

Figure 11a. (FW?CA) half-month average current vectors,

16-30 September 1967, 10 and 30 m.

Figure lIb. (FWPCA) half-month average current vectors,

16-30 September 1967, 15, 22, and 60 m.

Figure 12a. (FWPCA) half-month average current vectors,

1-15 October 1967, 10 and 30 m.

Figure 12b. (FWPCA) half-month average current vectors,

1-15 October 1967, 15, 22, and 60 m.

Figure 13a. (FWPCA) half-month average current vectors,

16-31 October 1967, 10 and 30 m.

Figure 13b. (FWPCA) half-month average current vectors,

16-31 October 1967, 15, 22, and 60 m.

Figure 14. (CCIW) half-month average current vectors at

10, 15, and 22 m, 1-15 June 1973.

Figure 15. (CCIW) half-month average current vectors at

10, 15, and 22 m, 16-30 June 1973.

Figure 16. (CCIW) half-month average current vectors at

10, 15, and 22 m, 1-15 July 1973.

Figure 17. (CCIW) half-month average current vectors at

10, 15, and 22 m, 16-31 July 1973.

Figure 18. (CCIW) half-month average current vectors at

10, 15, and 22 m, 1-16 August 1973.

Figure 19. (CCIW) half-month average current vectors at

10, 15, and 22 m, 17-31 August 1973.

Figure 20. (CCIW) half-month average current vectors at

10, 15, and 22 m, 1-15 September 1973.

Figure 21. (CCIW) half-month average current vectors at

10, 15, and 22 m, 16-30 September 1973.

Figure 22. Spectra of the east-west current component

at CCIW moorings 12 and 13, depth 10 m,

22 May-II August 1973.

v

Page

22

24

25

26

27

28

29

34

35

36

37

38

39

40

41

44
FIGURES (continued)

Figure 23. Same notation as figure 22, stations 12 and

13 at 10 m, east-west components, 12 August3 October 1973.

, Figure 24. FWPCA winter 1966-67 mooring sites.

TABLES

Table 1. (FWPCA) Current Components.

Table 2. (FWPCA) Current Components at Four Selected

Stations.

vi

Page

45

46

30

47
LARGE-SCALE CURRENT MEASUREMENTS IN LAKE SUPERIOR

Peter W. Sloss and James H. Saylor

Analyses of current meter data collected in Lake

Superior in 1967 and 1973 show a general counterclockwise

circulation c~vering most of the lak~l Currents near the

shore are strong - exceeding 10 cm s for a half-month

vector average - and generally parallel to the isobaths.

Open-lake currents show strong periodic motions at the local

inertial frequency. An interesting periodicity is seen in

the currents between Isle Royale and the northern shore.

Oscillatory components observed there are driven by inertial

motions when the lake becomes thermally stratified in late

summer, but in spring they show periodicities related to the

first and sixth free surface modes of the lake. Other persistent features of the measured flow patterns are the

Keweenaw Current and a general strengthening of summertime

flows as the lake becomes stratified.

1. INTRODUCTION

This report presents the results of an analysis of current meter data

collected in Lake Superior during 1966 and 1967 by the Federal Water Pollution Control Administration (FWPCA). (Subsequent to collection of the

data set, reorganization within the federal government placed this activity

within the responsibilities of the Environmental Protection Agency.) Results of the current meter surveys have not been previously published,

although aeveral selected episodes from a few of the current meter stations

h&ve been incorporated in various studies concerning the dynamics of small

areas of the lake. We attempt in this report to evaluate the usefulness

of this data set and to infer from it some characteristics of the largescale circulation patterns of Lake Superior. Additionally, comparisons of

these results with those of a current study conducted by the Canada Centre

for Inland Waters (CCIW) during 1973 are made to assist in verifying that

the current patterns deduced are truly representative of the summertime

circulation of Lake Superior.

Lake Superior is the largest of the five Great Lakes, with a length

of about 650 km and a maximum width of nearly 300 km (the average width is

120 km). The average depth of the lake is 175 m, and the volume of water

stored in Lake Superior exceeds the volume of water contained in all of the

other Gre2t Lakes combined. The surface area of the la~e is nearly

80,000 km , and this large water surface exerts much influence on the climate of the surrounding land masses.

Concommitant with the current studies conducted in 1966 and 1967, water

temperatures were measured at the same levels in the water column as the

current meters on each mooring. The water temperatures were recorded in
analog form on a waxed paper chart. Unfortunately, the usefulness of the

temperature data was limited by many mechanical failures of the recording

devices and uncertainties in the timing of many records. The data were not

systematically reduced and edited, but some features of the temperature

structure observed in Lake Superior were reported in Federal Water Quality

Administration (FWQA, 1968) reports. Millar (1952) discussed the annual

cycle of water ,temperature distribution in Lake Superior, and the 1966-67

data agree fairly well with Millar's results.

Lake Superior is nearly isothermal from December through early June of

each year. The fall turnover occurs as the water at the lake's surface is

cooled to 4°C. After attaining a nearly isothermal condition at this temperature, further cooling and intense wind stirring during winter result in

an essentially isothermal lake water mass at a temperature of O°,to 2°C.

Heating of the lake water in spring occurs first in the shallow water near

the lake coasts; this heated water spreads gradually during the course of

early summer toward the deeper areas near the center of the lake basin.

Because of the deep mean depth of Lake Superior, the quantity of water

which warms and forms the summer and early fall epilimnion is only a small

fraction (estimated in FWQA as 15 percent) of the lake's total water volume.

An important feature of epilimnion formation and distribution during the

course of summer heating is its unequal thickness over the lake basin,

with a deeper epilimnion near the coasts of the lake and a thinner layer

over the deep lake center. This characteristic is common to other lakes

as well, and is typical, for example, of the summer temperature distribution in Lake Huron. This pattern is perturbed by intervals of wind stress

which generate upwellings and downwellings. Since wind stress and the distribution of water density are the two most important forces driving the

currents in the Great Lakes during the season of density stratification,

the temperature distributions are indicative of current patterns. Whether

the density distribution drives the currents, or the currents establish

and help maintain the density distribution is an unanswerable question at

this time. The important point is that they are interrelated, and that the

observed temperature distributions fit the pattern, inferred from the current

meter recordings, of a general counterclockwise circulation of Lake Superior

during summer.

2. DATA COLLECTION AND TRANSLATION

A network of current meter moorings was deployed in Lake Superior from

the fall of 1966 through the summer of 1967 by the FWPCA. Seven moorings

were placed for the winter observations, and 16 for the summer; locations of

the summer moorings are shown in figure 1. A 17th summer mooring was lost.

Each mooring comprised a string of Geodyne current meters at FWPCA

$tandard depths of 10, 15, 22, 30, 60, 90, 120, and 150 meters, with the

number of meters on each mooring determined by water depth. Surface winds

were recorded at nine summer moorings. Current speed and direction were

recorded optically every 30 min as Gray-binary coded numbers represertted

by dot images on 16 mmfilm. Data films were decoded by an automatic

: i

I

!

i

L,'-u _

2
flying-spot scanner at Geodyne with the data transferred to BCD magnetic

tape for computer analysis.

92' 9" 90' 89' 88' 8" 86' 8"

• 9 •

7 a

•

6 14

4" •

rand

....hl.nd htarai.

Sault Ste. Marie

~u"i.in9

46' ' KILOMETERS 46' F3 F3 ... >0 0 >0 '00

STATUTE MILES !

-- -- >0 >0

92' 9" 90' 89' 88' 8" 86' 8"

48'1-'----t-----.j"-''''"'''''~~_Jd~-

49'i-i-----+- -t- -J- --:--.4- -1------+----+--------j49'

Figure 1. FWPCA 1967 summer mooring sites.

Additional data were supplied to the Great Lakes Environmental Research

Laboratory (GLERL) by the CCIW from their 1973 summer field season. Data

were returned from 12 moorings at 1 or more depths. Locations of CCIW

moorings are shown in figure 2.

3
-E

LAKE SUPERIOR 1973 C.C.I.W 49°/-

LAKE CURRENT OBSERVATIONS

• Location and designation of

current meter stations.

Figure 2. CCIW 1973 summer mooring sites.

Of 145 current meter and 9 wind data films collected by FWPCA, only

some 61 were usable; the rest showed some obvious malfunction of the current

meter clock, film system, or sensors and were not scanned. After automatic

scanning, several additional bad films became evident. There was a problem

in the scanner that caused it to lose track of the rotor-impulse channels on

the film, resulting in spurious zero-speed reports. All data analyzed by

the flying-spot scanner at Geodyne showed this defect with varying degrees

of severity. In addition to the spurious zero speeds, many data readings on

most films were flagged by the scanner as unreadable either for speed or

direction or both. Typical film translations resulted in some 10 percent of

the data points being flagged as unreadable or zero-speed. The net return

of data is thus some 40 percent of the expected sample, not including

4
several current meters which operated for only part of the intended season.

Only three wind films ran all summer, and some were as short as 3 to 10

days. Normalizing the sample size to expected record lengths would further

decrease the percentage of return.

Absolute timing of readable data is uncertain in some records since

there is evidence that some meters sometimes failed to advance the film

between readings. ~tarting points on many films are obscured or 1ightstruck,

making it necessary to approximate times based on film footage; therefore,

it must be recognized that the data on which the following discussions are

based were seriously degraded by lax quality control at FWPCA and their

contractors.

CCIW kindly supplied a number of current meter records which spanned

June through September 1973. Most of these data are from moorings near the

Canadian and Minnesota shore lines on the northwest, with four moorings

near Upper Michigan, off the Keweenaw Peninsula, and near Grand Marais,

Mich. The data were collected by the use of current meters built by P1essy

and magnetic-recording Geodyne meters, and reported as hourly averages after

editing. The results look much more consistent than the FWPCA data set.

3. RESULTS

3.1 Summer Circulation - 1967

Resultant currents were calculated from each operating current meter's

output for each half month from mid-May through October 1967. This averaging procedure is described by Sloss arid Saylor (1975). These resultants

are summarized in figures 3-13. Maps with suffix "a" show resultant current

vectors for 10- and 30-m depths; maps with suffix "b" show resultant current

vectors for 15-, 22-, and 60-m depths. Some large-scale features of the net

circulation of the lake can be seen in spite of the wide spacing between

observation points.

Thermal stratification begins in Lake Superior in early June and continues into September, but the thermocline is unlikely to pass for any long

duration below 30 m. The average maximum epi1imnion thickness is about 22 m

(FWQA, 1968). As a restl1t, most current vectors presented here represent

flow in the hypolimnion. It is highly probable that current speeds reported

here are lower than the actual values due to the frequent incidence in the

data of zero speed readings which continuity would seem to contradict. Canadian data from 1973 (discussed later) show considerably higher speeds at

nearly the same locations studied during 1967 and under similar conditions.

Usable data started with the second half of May 1967 (fig. 3a, b) for

stations west of 88°W longitude. Winds for this period averaged from the

northerly quadrant, but recorded currents at 10 and 30 m show no organized

pattern. Flow at 10 m is offshore at moorings 2 and 3. This pattern suggests that upwelling along the southern shore may have occurred in the

western part of the lake because the 30-m flow is onshore at station 2.

5
90' 89' 88' 8" 86'

49' 16-31 MAY 67 -t-_----J-_~,-----+---+--r-149·

•

\

5 10

cm·.-1

30m @ .

10 m ••----~.--

18 F4 I 5 0

~~;c:];.... ;;;c~==~"'~;;;;;;;;;~-I- -I- +- -t-----t-----,--l46. STATUTE WILES j IIIIIiII8 ........

46'

48·1--r----t-------.:P-"""'i:?-=-----J:~~

'" '" 92' 9" 90' 89' 88' 8" 86'

Figure 3a. (FWPCA) half-month average aurrent vectors, 16-31 May 1967,

10 and 30 m.

-1 The first half of June saw mean winds at approximately 3 m s from

the northeast. Currents at 10 m flowed southwestward along the shore at

station 4 and continued offshore at 2 and 3 (fig. 4a). Strong offshore

flow at station 1 at 15 m indicated the flow turned to follow the shore

in a counterclockwise pattern (fig. 4b). At station 9, the Keweenaw

Current was beginning to app~tr in the data. Smith_tl972) reported that

~his current reached 80 cm s and averaged 26 cm s ,although no such

magnitudes were seen in the FWPCA data. This is assumed to be related to

measurement hardware, not nature. Smith's data were confirmed by CCIW

measurements at their mooring 4. No other organized flow was evident for

this period in the FWPCA data.

6
•

86' 85'

•

•

MunisinSl

87'

_--t- ~----~c=:::;:::::::t~Chij>i.-~--148. ichipicoten

I.

8" 'D·

l-_J-_----+---+------1r-----i~146.

----t------1-----....,,4~----+__----_+-----I----- 49' 18 - 31 MAY 87

22m (f) ..

15m ......------

80m •••----1IIiIIII I F3 E3 I 5 0

46' KILOlfETERS ..... -..... 50 • 50

STATUTE MILES , ...... ...... 50 50

'2' 9,' 90' 89' 88' 87' 86' 85'

47'f---+-_

48'

4"

Figure 3b. (FWPCA) half-month average C!Urrent vectors, 16-31 May 1967,

15, 22, and 60 m.

7
or 91' .0' U' 88' 8" 86' 8S' 1-- ..' 1 -15 JUNE 67 - 4"

10 m •

30m @ .......................

em·.-1

I 8 8 I I I 5 0 5 10

48'

48'

,

•

f\t ..,Ii 4"

Whitef"h Pt. 'ond

....,...

Wuftt.ing

KILOMETERS 46'

46' .... E3 E3

" 0 50 "'" STATUTE IIILES I ..... -- ,. ,.

.2' 9''- .0' 8.' 88' 8" 86' os'

Figure 4a. (FWPCA) haZf-month ave~age au~rent veators~ 1-15 June 196?~

10 and 30 m.

8
•

4'1~

•

•

92- 9'· 9~ 89- 8e- 8r 86- 85-

I~--J------=T--------=r--~~------::;~-"

1 -15 JUNE 67

22m ,

15m ......----__

4S' KILOMETERS .... .... .... so 0 so ... STATUTE MILES I ........ ..... so so

92' 91' 90' 89' 88' 81' 8S' 8"

80m •

cm's-1

48' I 8 8 I I I 5 0 5 10

..'

Figure 4b. (FWPCA) half-month average current vectors, 1-15 June 1967,

15, 22, and 60 m.

9
Data for 16-30 June (fig. 5a, b) began to show a general counterclockwise flow encompassing the whole lake in the 10- and l5-meter layers.

Flows at 30 m opposed shallower flows at many stations. Mean winds were

light and had switched to the south quadrant.

Southerly winds in early July triggered possible upwelling along much

of the south shore of Lake Superior (fig. 6a, b). While 10-m flows were

offshore or p~rallel to shore at most southern lake stations, 30-m flows

were strongly onshore. Surface layer (lO-m) flow at stations 11 and 12

was to the south, as were all deeper flows at station 12, suggesting a

return flow there supporting the upw~lling. All measured average 10-m

current speeds remained below 5 cm s for this period.

Stronger 10-m flows were found for 16-31 July at station 11, ,indicating

a westward flow south of Isle Royale to maintain a general counterclockwise

circulation for the whole lake (fig. 7a, b). These flows were the strongest

measured at 10 m for any 2-week period at an offshore station. Most of

the high speed flow measured during this interval occurred during only 4 -1

days of data - 17-21 July - during which an average speed of over 58 cm s

was reached, with no missing readings reported for a l6-hr inte~val. The

question must be raised whether this represents true readings in the record.

These data were coded during the scanning process as "rotor too fast to

read speed channel." The data from station 12 nearby show no such velocity

surge for the same days. Station 11 data from 10-m depth, in fact, became

unreadable for the last 6 days of July. Flows below 10 m support a continued counterclockwise circulation covering the lake.

Early August winds averaged to very small resultants, and currents in

the lake were generally light. At station 11, flow changed to_rPparent

continuous inertial loops wi!~ a net drift of less than 1 cm s ,but an

orbital speed of 2 to 5 cm s in the inertial loop. The general counterclockwise circulation continued (fig. 8a, b).

The second half of August saw light northerly winds. Circulation at

10 m showed continuation of the pattern of previous maps. Note that the

10-m vector for station 9 seems permanently locked toward the north-northwest, while the Keweenaw Current shows prominently at 15 and 60 m (fig. 9a,

b). Thus, the recordings from the 10-m level at station 9 are judged unreliable.

The maps for 1-15 September (fig. lOa, b) are similar to the August

set. The counterclockwise la~iwide circulation persisted and the Keweenaw

Current averaged_fome 13 cm s at 15 m. At station 15 at 30 m, the current

exceeded 15 cm s parallel to bathymetry. Flow at station 16 at both 10

and 15 m pointed into the lake rather than toward Sault Ste. Marie, Mich.

This station was located west of the deepest water in the region, and indicated a circulation pattern in Whitefish Bay which may be usually clockwise in summer, with St. Marys River water originating in a southward flow

along the Canadian shore of the bay. Flows at stations 2 and 3 were parallel

to shore, following the prevailing circulation.

10
"

90' .,' N' 8r 86' 8S'

49' 49'

16 - 30 JUNE 67

10 m •

30m @ ............... .......

cm·.-1

I H H I I I

5 0 5 10 48 48'

,i(

./1 .' 4" ,

.1

:

...... Muntei",

KILOMETERS 46' 46' ..... ..... .. -0 50 100

STATUTE MILES I ........ ........ 50 50

9" 9" 90' 89' 88' 8" 86' 8S'

Figure 5a. (FWPCA) half-month average <JUPrent vectors 3 16-30 June 19673

10 and 30 m.

11
•

--I-----+-_~l____-_t_-_+_-_t-1·9'

a

Wa,••

90' 89' 88' 8" 86'

'9' 16 - 30 JUNE 67

15m •

22m @ .......................

80m • cm·.-1

'8' I R R I

A I

5 0 10

Wuniait\9

KILOMETERS '6' .... .... F3 so 0 so '00

STATUTE MILES , ....... ....... so so

OZ' 9,' 90' 89' 88' 8" 86' B"

'6'

Figure 5b. (FWPCA) haZl-month average aurrent vectors, 16-30 June 1967,

15, 22, and 60 m.

12
•

,,- ..' • 0· .,. ... 8" 86' 8S'

49-

4'· 1-15 JULY 67

10m •

30m @ .......................

cm·.-1

I 8 8 I I I 5 0 5 10 48· 48· tehipicOlWl

'\ . a

.,. •

, ,.nd r;l ...,.... Wuni.ing

KILOMETERS <,' 4,· - ..... ..... ... aa ... 0 .. '00

STATUTE MILES c:::::E"'!3:: ....... .. .. 9'- 9'· 90· 8'· 88' 8'· 86' .,'

Figure 6a. (FWPCA) haZf-month average current vector8~ 1-15 JuZy 1967~

10 and 30 m.

13
!!I I

I, .

86' 85'

eo' e8' 8" 86'

-t-_---I--_-+-----+-~r---1146.

1-15 JULY 67

cm·.-1

I E3 8 I I

22m e·..·..·....·..........·

15 m ••1-------

80m •••-----

46' .... .... so ... ,

-- 50 50

92' 9" 00' eo' 88" 8"

48'

40'

Figu1'e 6b. (FWPCA) half-month average au1'rent veotors, 1-15 July 196?,

15, 22, and 6Om.

14

ptrtt
•

86'

.......

."

Y.,

90" 89" 88"

-+------l----,-.:..-,.ti-------l-------+-----r------i""

10

•

Aohlond

16 - 31 JULY 67

30m @ .

10 m ••_------

1-r-:#----1~~li~_I___--~<.....,..JV~+---_I_____:; .....•.-l---+~=1 .. ..

<8"1-~-----+-----_-4_-;;~=-~J...J~r!!...._

<9'

<6" KILOMETERS

..... ,,"

I __

o ..

STATUTE MILES

-- 9<" 9" 90" 88' 8'" 86" 8"

Figure ?a. (PWPCA) haZf-month average auI'rent veator8~ 16-31 JuZy 196?~

10 and 30 m.

15
•

49" 16-31 JULY 67 -t-------+----~--'-----+_--+_-_t------ ",'

90' 89' .,. 06' .,'

15 m ,.1-------

22 m $ ..

80m • cm·.-1

48' I R R I

! I

5 0 10

Muniai,.,

80' 8"

-I-_-!-_+-_+--+--II'O' KILOMETERS 40' .... ..... .... ,. . .. STATUTE MILES i ..... ..... .. .. .r .,' .0' 8.' oa' .,'

Figure 'lb. (FWPCA) half-month average auITent vectors, 16-31 July 1967,

15, 22, and 60 m.

16

..tt;;:;_-. u __
a

90' 89' 88' 8" 86'

10

1 -16 AUGUST 67

cm·.-1

30m @ .

10 m ee-------

I H E3 I 5 0

48'I-T-----t-----t--.-~~___:.h31e.-

49'

46'

..

.... .... ....KILOMETERS

0 .. ~-+--_+__+_-+_-\-'6' STATUTE WILES "'" I

-- -- .. .. OZ· 91' 90' B9" BB" 8'" B6' B;'

Figure 8a. (FWPCA) half-month average current vectors.. 1-16 August 1967.. 10 and 30 m.

17
!lllj ,,!'

i[

ii!i

4" - 1 -16 AUGUST 67 ---l- --l ~L----I_---_+---T-T----14"

.0' 8" 86'

10

22m 8·..· ..·..·....·........

15m .......------

80m •••-----

46'

88' 8" 8li"

-l-------'---+----t-------1-------j--- 46' KILOMETERS " ,..... .... F3. '" ... STATUTE MILES

-- -- ,.

'Z' ,,' .0' 8.'

Figure Bb. (FWPCA) half-month average ourrent veotors, 1-16 August 1967,

15, 22, and 60 m.

18

..........=;;;;;;;;;----==================--------------------------._-- ---
90' 89' 6" 66'

30m 0 · ·..·

10 m ••l--------

S.ult St•. Meri

5 10

-_.- tht<M\"~-:-+----t--

cm·s-1

I F3 E3 I 5 0

48' ---·-I------+------f>...-='iff!:--~~i"~

49' - 16 - 31 AUGUST 67

46' KILOMETERS ..... 46'

o 50

STATUTE MILES

5O~.... ;;;;;c:::i""~~~;;;;;;;;;;;;;;;~50

9" 9" 90' 89' 86' 6" 66'

Figu:pe 9a. (PWPCA) haZf-month average ou:p:pent vecto:ps, 16-J1 August 196?~

10 and JO m.

19
I II

•r ". '0· ... ... ar a6· a'·

4~'" 49· 16 - 31 AUGUST 67

15m •

22m .......................

80m • cm·.-1 4B' 4B· I R R 6 I I 5 5 10 ••

..- •

J - ----51 i; 41"

I

:1

'ond

.........

Nunising

KILOMETERS 4'· 1;6· - .. S .. .. ,. --- --- - 0 ,. ST"TUTE WILES ...... ...... 0

___ J -- _ '0 _____- n ______ ,_,··____

9?" ". ~JO. 8!t· 8B· 8" "' "","

Figure 9b. (FWPCA) haZf-month average current veotors, 16-31 August 1967,

15, 22, and 60 m.

20
'9' 1 - 15 SEPTEMBER 67 -+-_-+-_~_-+---t--~~.9.

90' S9' ss· .,. .6' .,'

30m @ ..

10m ......------

..'

5 10

cm·.-1

I F3 E3 I 5 0

1--t----:;<(----~lo-!-~~LL--+----__r1"'-.,....IIV~_I_---_T-- .'OL'-l----

.···I----r-------j-----~.;=~~-~~€--

Wuniaing

KILOMETERS '6' F3 F3 ..... ... 0 .. STATUTE MILES "'" !

-- eo- .. .. 92' .,. 90· 89' 8.' 8" 86' 8"

'6'

Figure lOa. (FWPCA) haZf-month average CJUrrent vectors, 1-15 September 1967,

10 and 30 m.

21