JOURNAL
Correction
OF GEOPHYSICAL
RESEARCH,
VOL. 101, NO. C8, PAGE 18,451, AUGUST
to "A!iased tidal errors in TOPEX/POSEIDON
15, 1996
sea
surface height data" by M. G. Schlax and D. B. Chelton
Table 2. GeosatAlias Periodsand Three LongestAlias
In the paper "Aliased tidal errors in TOPEX/POSEIDON
sea surfaceheight data" by M. G. Schlaxand D. B. Chelton Wavelengthsfor the Six Major Tidal Constituents
(Journal of GeophysicalResearch,99(C12), 24,761-24,775,
1994), Tables 1, 2, and 3 all containerrors in the aliaswave- Tide
days
deg
•o, deg
•, deg
lengthsof the tidal harmonics.The correctedtables appear
317.13
1.25W
8.00 W
1.81 E
below.The changeshavelittle or no effecton the primary alias M 2
S2
168.81
1.46 E
179.89E
1.49 W
wavelengthsAothat are of most interest in applications.The
N2
52.07
1.08 E
4.09 E
2.31 W
major error was the interchangeof the secondaryaliasvalues K1
175.45
1.47 E
359.79 E
1.48 W
for A_• and • in the tablesfor TOPEX (Table 1) and ERS 1
O1
112.95
1.25W
8.18 W
1.80 E
4465.22
1.47E
359.78E
1.48W
(Table 3). Minor changeshave been made to the primary P1
aliasesfor TOPEX. Note further that the repeat period of
The directionof propagationfor each alias is denotedas E for east
Geosatusedto calculatethe entriesin Table 2 is 17.0505days, and W for west.
rather than 17.05 daysaswas statedin the paper (p. 24,765).
We alsowish to offer a more intuitiverationalefor equation
(3a),
Table 3. ERS 1 Alias Periodsand Three LongestAlias
27/'
Wavelengthsfor the Six Major Tidal Constituents
•½x
= •qbx• •t.
(3a)
As wasstatedin the text, •qbxis the phasechangethat occurs
over the time interval •t betweenthe nearest-timepointson
two adjacentascending
tracks.Thisis the phasechangethat
Tide
Ta,
days
i•-1,
deg
M2
94.49
0.78 W
S2
hastraditionally
beenusedin thecalculation
of aliaswave- K•
N2
lengths.
During
thetimeinterval
•t thephase
ofthealiased O1
signalat the earliertrackhasalsoadvanced
by the amount p•
2rrT•-•t. The synchronous
phasedifferencebetweenthe
•
97.39
365.25
75.07
365.25
0.72
0.86
0.72
0.79
0.72
•o, deg
8.79 E
179.76
E
E
W
W
4.29
359.70
8.58
359.52
•, deg
0.67 E
0.72
W
E
E
W
0.62
0.72
0.66
0.72
W
W
E
E
The directionof propagationfor eachaliasis denotedas E for east
and W for west.
Table 1. Tidal Periods, TOPEX Alias Periods, and the
Three LongestAlias Wavelengthsfor the Six Major
Tidal
Constituents
Tide
Period,
hours
Ta,
days
deg
•o, deg
•, deg
M2
S2
N2
K•
O•
P•
12.420601
12.
12.658348
23.93447
25.819342
24.06589
62.11
58.74
49.53
173.19
45.71
88.89
2.16E
2.79 W
2.16 W
2.81 W
2.17 E
2.81 W
9.01 E
183.01W
9.01 W
366.03W
9.24 E
366.03W
4.14 W
2.88 E
4.14 E
2.86 E
4.09 W
2.86 E
aliasedsignalsat the adjacentnodesis therefore givenby the
difference(3a).
Acknowledgments.
The authorswishto thankChenGe for bringing theseerrors to our attention and helpingto resolvethem, and an
anonymousreviewerof the originalmanuscriptfor pointingout the
interpretationof equation(3a) givenhere.
The directionof propagationfor eachaliasis denotedas E for east
and W for west.
(ReceivedAugust 18, 1995.)
Copyright1996by the AmericanGeophysicalUnion.
Paper number96JC01970.
0148- 0227/96/96J C-01970509.00
18,451