2000.09.09 By K. Matsumoto @ National Astronomical Observatory
1. NAOTIDE & NAOTIDEJ
NAOTIDE is a program to predict ocean tidal height at given
time and location using ocean tide model developed by
assimilating TOPEX/POSEIDON altimeter data. NAOTIDEJ is a
program for ocean tidal prediction near Japan using higher
resolution regional model. This package comes with NO
WARRANTY.
2. Ocean tide model
* Short-period ocean tide model (NAO.99b, NAO.99Jb models)
Models for major 16 constituents (M2, S2, K1, O1, N2, P1,
K2, Q1, M1, J1, OO1, 2N2, Mu2, Nu2, L2, T2) are
prepared. Model region and resolution are as follows,
Model Region Resolution
Global model (NAO.99b) 0degE-360degE, 90degS-90degN 0.5deg
Regional model around Japan (NAO.99Jb) 110degE-165degE, 20degN-65degN 5min
These models are developed by assimilating nearly 5 years
of TOPEX/POSEIDON altimeter data (Cycle 10-198) into
hydrodynamical model. The appropriate reference to NAO.99b
and NAO.99Jb models is
Matsumoto, K., T. Takanezawa, and M. Ooe,
Ocean Tide Models Developed by Assimilating TOPEX/POSEIDON
Altimeter Data into Hydrodynamical Model: A Global Model
and a Regional Model around Japan,
Journal of Oceanography, 56, 567-581, 2000.
* Long-period ocean tide model (NAO.99L model)
Global models for 7 constituents (Mtm, Mf, MSf, Mm, MSm,
Ssa, Sa) are prepared. The long-period global models are
developed by T. Takanezawa (NAO). These models are purely
hydrodynamical model (T/P data not assimilated). Model
region and resolution are as follows,
Model Region Resolution
Mtm, Mf, MSf, Mm, MSm, Ssa 0degE-360degE, 90degS-90degN 0.5deg
Sa 0degE-360degE, 90degS-90degN 1.0deg
Sa model is re-sampled into 0.5 deg map for the sake of
convenient calculation, although their original resolution
is 1.0 deg.
A paper for the long-period model is now being prepared.
* Radial loading tide model
Global models for above 23 constituents are prepared.
They are based on spherical harmonic decomposition of
ocean tidal field up to degree and order 360.
Model Region Resolution
Global model 0degE-360degE, 90degS-90degN 0.5deg
Sa loading models is developed using re-sampled 0.5deg map
although their original resolution is 1.0deg for the sake
of convenient calculation.
3. Performance
Comparison with 98 open ocean tide gauge data shows
comparable performance of NAO.99b model as CSR4.0 and
GOT99.2b model.
---------------------------------------------------------------------------
| M2 O1 K1 S2 P1 N2 K2 Q1 | RSS
---------------------------------------------------------------------------
RMS Misfit NAO.99b | 1.457 0.755 1.011 1.033 0.378 0.643 0.426 0.236| 2.364
RMS Misfit CSR4.0 | 1.477 0.848 1.100 1.000 0.397 0.631 0.509 0.324| 2.456
RMS Misfit GOT99.2b| 1.392 0.829 1.035 1.006 0.372 0.637 0.414 0.289| 2.347
---------------------------------------------------------------------------
Unit is in cm.
Collinear residual reduction test shows that performance of
NAO.99b is better than CSR4.0 and GOT99.2b in shallow waters.
TOPEX/POSEIDON data cycles 240-258 are used for this test.
-------------------------------------------------------------------------
ocean depth (m) | 0 < H < 200 | 200 < H < 1000 | 1000 < H
# of normal points | 25609 | 18796 | 525054
-------------------------------------------------------------------------
RMS collinear diff. NAO.99b | 11.20 cm | 6.98 cm | 8.56 cm
RMS collinear diff. CSR4.0 | 15.77 cm | 7.37 cm | 8.55 cm
RMS collinear diff. GOT99.2b| 13.99 cm | 7.37 cm | 8.65 cm
-------------------------------------------------------------------------
4. Program
Program is supplied as a subroutine form. You may see how
to use it by taking a look at a test driver program
naotest.f (or naotidej.f for calculation near Japan).
In the program naotest.f,
at the line
itmode = 1
you can select tidal calculation mode.
itmode = 1 : compute geocentric tide, which is sum of pure
ocean tide and radial loading tide. This mode
is used for tidal correction for altimeter
data.
itmode = 2 : compute pure ocean tide with respect to ocean
floor. This mode may be used for tidal
correction for sea-bottom pressure gage.
itmode = 3 : compute radial loading tide.
At the line
lpmode = 1
you can select the way of calculating long-period tide.
lpmode = 1 : use the long-period ocean tide map of
Takanezawa (2000, in prep.).
lpmode = 2 : use equilibrium tide model. This is valid for
itmode = 1 or 2. Note that, however, the same
value will be returned for both itmode values.
18.6-year period tide (Doodson #055.565) is treated as
equilibrium tide for both lpmode = 1 and 2.
At the lines
x = 246.61503d0 ! East longitude in degree
y = -18.42767d0 ! North latitude in degree
given are the ocean location where you want to predict tides.
At the lines
iyear1 = 1997 ! year
imon1 = 1 ! month
iday1 = 1 ! day
ihour1 = 0 ! hour
imin1 = 0 ! minute
given are the start time epoch of prediction in UTC.
At the lines
iyear2 = 1997 ! year
imon2 = 1 ! month
iday2 = 2 ! day
ihour2 = 0 ! hour
imin2 = 0 ! minute
given are the end time epoch of prediction in UTC.
At the line
dt = 60.d0 ! in minute
give is the time step of prediction in minute.
At the line
outfile = 'naotest.out'
given is the output file name.
The output file will look like this;
Geocentric tidal height
Elapsed day Tide(cm) Short-p Long-p M D Yr H M MJD Longitude Latitude
0.0 -21.809 -21.663 -0.146 1/ 1 1997 0: 0 50449.000000 246.6150 -18.4277
0.041667 -21.544 -21.403 -0.141 1/ 1 1997 1: 0 50449.041667 246.6150 -18.4277
0.083333 -14.953 -14.817 -0.136 1/ 1 1997 2: 0 50449.083333 246.6150 -18.4277
0.125000 -3.783 -3.652 -0.131 1/ 1 1997 3: 0
50449.125000 246.6150 -18.4277
Elapsed day : elapsed time reckoned from the start epoch in day.
Tide : tidal height in cm, which is sum of
the short-period tide and the long-period tide.
Short-p : short-period tide in cm.
Long-p : long-period tide in cm.
M D Yr H M : time in UTC.
MJD : corresponding Modified Julian Date.
Longitude : East longitude in degree.
Latitude : North latitude in degree.
The short-period tide value is from 16 major constituents
and 33 minor constituents which is inferred from major ones
by interpolating or extrapolating the admittance.
The long-period tide value is from 7 major constituents and
5 nodal modulations. 18.6-year period equilibrium tide is
added to the 12 terms when itmode = 1 or 2.
62 tidal constituents are considered in total.
5. Install
The following files are necessary for global ocean tidal
prediction;
naotide990909.tar.gz
nao99b_gc.tar.gz + nao99L_gc.tar.gz (if you need geocentric tidal height)
nao99b.tar.gz + nao99L.tar.gz (if you need pure ocean tidal height)
nao99b_rload.tar.gz (if you need radial loading tidal height)
The following files are necessary for regional ocean tidal
prediction using high-resolution tidal maps;
naotidej990909.tar.gz
nao99Jb_gc.tar.gz + nao99L_gc.tar.gz (if you need geocentric tidal height)
nao99Jb.tar.gz + nao99L.tar.gz (if you need pure ocean tidal height)
(Note: No regional models for long-period tides and radial loading tides)
I suppose you are working on UNIX system. The similar as for
naotidej.
Make nao99b directory.
(~): mkdir nao99b
(~): cd nao99b/
Make omap directory.
(~/nao99b): mkdir omap
(~/nao99b): cd omap
If you need geocentric tidal height;
(~/nao99b/omap): gunzip nao99b_gc.tar.gz
(~/nao99b/omap): tar xvf nao99b_gc.tar
(~/nao99b/omap): gunzip nao99L_gc.tar.gz
(~/nao99b/omap): tar xvf nao99L_gc.tar
If you need pure ocean tidal height;
(~/nao99b/omap): gunzip nao99b.tar.gz
(~/nao99b/omap): tar xvf nao99b.tar
(~/nao99b/omap): gunzip nao99L.tar.gz
(~/nao99b/omap): tar xvf nao99L.tar
If you need radial loading tidal height;
(~/nao99b/omap): gunzip nao99b_rload.tar.gz
(~/nao99b/omap): tar xvf nao99b_rload.tar
Extract naotide program in the nao99b directory.
(~/nao99b/omap): cd ..
(~/nao99b): gunzip naotide000909.tar.gz
(~/nao99b): tar xvf naotide000909.tar
Compile the program in the naotide directory.
(~/nao99b): cd naotide
(~/nao99b/naotide): f77 (or f90) -o naotest naotest.f
Make a link to the tide model directory.
(~/nao99b/naotide): ln -s ../omap .
6. Validation
Run naotest and compare the output file "naotest.out" with
"naotest.out.exam".
(~/nao99b/naotest): naotest
naotest.out.exam is the result on HI-UX/MPP.
7. Format transformation
The tide models are written in integer table format. In
order to transform them to standard (Longitude, Latitude,
Amplitude, Greenwich phase) format, please use
nao2xyap.f such as;
% f77 (f90) -o nao2xyap nao2xyap.f
% nao2xyap < m2.nao > m2.xyap
8. E-mail contact
* Questions about the short-period ocean tide model and
the software as well as reprint request should be sent to
National Astronomical Observatory
Koji MATSUMOTO
matumoto@miz.nao.ac.jp
* Questions about the long-period ocean tide model should
be sent to
National Astronomical Observatory
Takashi TAKANEZAWA
takane@miz.nao.ac.jp
EOF
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