1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705
|
\newpage
\chapter{Transformations and interpolations}
\label{sec_transformations}
Different transformations and 2D interpolations are available in
OASIS3-MCT to adapt the coupling fields from a source model grid to a
target model grid. In the following paragraphs, a description of each
transformation with its corresponding configuration lines that the
user has to write in the {\it namcouple} file is given. Features that
are now deprecated (non functional) compared to prior versions will be
noted with the string UNUSED but not described.
\section{Time transformations}
\label{subsec_timetrans}
\begin{itemize}
\item {\bf LOCTRANS}:
{\tt LOCTRANS} requires one configuring line on which a time
transformation, automatically performed below the call to {\tt
oasis\_put}, should be indicated:
\begin{verbatim}
# LOCTRANS operation
$TRANSFORM
\end{verbatim}
% $
\vspace{-0.2cm} where {\tt \$TRANSFORM} can be
\begin{itemize}
\item {\tt INSTANT}: no time transformation, the instantaneous field
is transferred;
\item {\tt ACCUMUL}: the field accumulated over the previous
coupling period is exchanged (the accumulation is simply done over
the arrays {\tt field\_array} provided as third argument to the
{\tt oasis\_put} calls, not weighted by the time interval between
these calls);
\item {\tt AVERAGE}: the field averaged over the previous coupling
period is transferred (the average is simply done over the arrays
{\tt field\_array} provided as third argument to the {\tt
oasis\_put} calls, not weighted by the time interval between
these calls);
\item {\tt T\_MIN}: the minimum value of the field for each source
grid point over the previous coupling period is transferred;
\item {\tt T\_MAX}: the maximum value of the field for each source
grid point over the previous coupling period is transferred;
\item {\tt ONCE}: UNUSED ; {\bf not supported in OASIS3-MCT.}
\end{itemize}
With OASIS3-MCT, time transformations are supported more generally
with use of the coupling restart file. The coupling restart file
allows the partial time transformation to be saved at the end of a
run for exact restart at the start of the next run. For that
reason, coupling restart filenames are now required for all {\it
namcouple} entries that use LOCTRANS (with non INSTANT
values). This is the reason an optional restart file is now provided
on the OUTPUT {\it namcouple} input line.
\end{itemize}
\section{The pre-processing transformations}
\label{subsec_preproc}
\begin{itemize}
\item {\bf REDGLO} UNUSED
\item {\bf INVERT}: UNUSED
\item {\bf MASK}: UNUSED
\item {\bf EXTRAP}: UNUSED
\item {\bf CHECKIN}:
{\tt CHECKIN} calculates the global minimum, the maximum and the sum
of the source field values (not weighted by the grid cell area) and
prints them to the OASIS3-MCT debug file (for the master process of
the source component model only). These informations are found in
the debug file of the master process of the source model under the
attribute ``diags''.
This operation does not transform the field.
The generic input line is as follows:
\begin{verbatim}
# CHECKIN operation
INT = 1
\end{verbatim}
\item {\bf CORRECT}: UNUSED
\item {\bf BLASOLD}:
{\tt BLASOLD} allows the source field to be scaled and allows a
scalar to be added to the field. The prior ability to perform a
linear combination of the current coupling field with other coupling
fields has been deprecated in OASIS3-MCT. This transformation
occurs before the interpolation {\it per se}.
This transformation requires at least one configuring line with two
parameters:
\begin{verbatim}
# BLASOLD operation
$XMULT $NBFIELDS
\end{verbatim}
% \vspace{-0.2cm}
where {\tt \$XMULT} is the multiplicative coefficient of the source
field, which must be given as a REAL value (e.g 2.0 and not 2). {\tt
\$NBFIELDS} must be 0 if no scalar needs to be added or 1 if a
scalar needs to be added. In this last case, an additional input
line is required where {\tt \$AVALUE} is the scalar to be added to
the field, which must also be given as a REAL value :
\begin{verbatim}
CONSTANT $AVALUE
\end{verbatim}
\end{itemize}
% subsection{The pre-processing transformations}
\section{The remapping (interpolation)}
\label{subsec_interp}
\begin{itemize}
\item {\bf MAPPING}:
The {\tt MAPPING} keyword is used to specify an input file to be
read and used for mapping (ie. regridding or interpolation); the
{\tt MAPPING} file must follow the {\tt SCRIPR} format. This is an
alternative method to {\tt SCRIPR} for setting the mapping file.
Since OASIS3-MCT\_2.0, {\tt MAPPING} can be used for higher order
remapping. Up to 5 different sets of weights (see section
\ref{subsec_mapdata} for the weight file format) can be applied to
up to 5 different fields transfered as {\tt oasis\_put} arguments
(see section \ref{prismput}).
This transformation requires at least one configuring line with one
filename and two optional string values:
\begin{verbatim}
$MAPNAME $MAPLOC $MAPSTRATEGY
\end{verbatim}
\begin{itemize}
\item {\tt \$MAPNAME} is the name of the mapping file to read. This
is a NetCDF file consistent with the SCRIPR map file format (see
section \ref{subsec_inputdata}).
\item {\tt \$MAPLOC} is optional and can be either {\tt src} or {\tt
dst}. With {\tt src}, the mapping will be done in parallel on
the source processors before communication to the destination
model processes; this is the default. With {\tt dst}, the mapping
is done on the destination processes after the source grid data is
sent from the source model.
\item {\tt \$MAPSTRATEGY} is optional and can be either {\tt bfb},
{\tt sum}, or {\tt opt}. In {\tt bfb} mode, the mapping is done
using a strategy that produces bit-for-bit identical results
regardless of the grid decompositions without leveraging a partial
sum computation; this is the default. With {\tt sum}, the
transform is done using the partial sum approach which generally
introduces roundoff level changes in the results on different
processor counts. Option {\tt opt} allows the coupling layer to
choose either approach based on an analysis of which strategy is
likely to run faster. Usually, partial sums will be used if the
source grid has a higher resolution than the target grid as this
should reduce the overall communication (e.g. for conservative
remapping).
\end{itemize}
Note that if {\tt SCRIPR} (see below) is used to calculate the
remapping file, {\tt MAPPING} can still be listed in the {\tt
namcouple} to specify a name for the remapping file generated by
{\tt SCRIPR} different from the default and/or to specify a {\tt
\$MAPLOC} or {\tt \$MAPSTRATEGY} option.
\item {\bf SCRIPR}:
{\tt SCRIPR} gathers the interpolation techniques offered by Los
Alamos National Laboratory SCRIP 1.4 library
\citep{Jones99}\footnote{See also
http://climate.lanl.gov/Software/SCRIP/ and the copyright
statement in appendix \ref{sec_SCRIP}.}. {\tt SCRIPR} routines
are in {\tt oasis3-mct/lib/scrip}. See the SCRIP 1.4 documentation
in {\tt oasis3/doc/SCRIPusers.pdf} for more details on the
interpolation algorithms.
When the SCRIP library performs a remapping, it first checks if the
file containing the corresponding remapping weights and addresses
exists; if it exists, it reads them from the file; if not, it
calculates them and store them in a file. The file is created in the
working directory and is called {\tt rmp\_{\it srcg}\_to\_{\it
tgtg}\_{\it INTTYPE}\_{\it NORMAOPT}.nc}, where {\it srcg} and
{\it tgtg} are the acronyms of respetively the source and the target
grids, {\it INTTYPE} is the interpolation type, i.e. {\tt DISTWGT},
{\tt GAUSWGT}, {\tt BILINEAR} ({\bf not BILINEA as in OASIS3.3}) or
{\tt CONSERV} -see below, and {\it NORMAOPT} is the normalization
option, i.e. {\tt DESTAREA}, {\tt FRACAREA} or {\tt FRACNNEI} for
{\tt CONSERV} only -see below). One has to take care that the
remapping file will have the same name even if other details, like
the grid masks, are changed. When reusing a remapping file, one has
to be sure that it was generated in exactly the same conditions than
the ones it is used for.
The following types of interpolations are available:
\begin{itemize}
\item {\tt DISTWGT} performs a distance weighted nearest-neighbour
interpolation (N neighbours). All types of grids are supported.
\begin{itemize}
\item Masked target grid points: the zero value is associated to
masked target grid points.
\item Non-masked target grid points having some of the N source
nearest neighbours masked: a nearest neighbour algorithm using
the remaining non masked source nearest neighbours is applied.
\item Non-masked target grid points having all of the N source
nearest neighbours masked: by default, the nearest non-masked
source neighbour is used (logical {\tt ll\_nnei} hard-coded to
{\tt .true.} in {\tt oasis3-mct/lib/scrip/src/remap\_distwgt.F};
same default behaviour as OASIS3.3).
\end{itemize}
The configuring line is:
\begin{verbatim}
# SCRIPR (for DISWGT)
$CMETH $CGRS $CFTYP $REST $NBIN $NV $ASSCMP $PROJCART
\end{verbatim}
where:
% \vspace{-0.5cm}
\begin{itemize}
\item {\tt \$CMETH = DISTWGT}.
\item {\tt \$CGRS} is the source grid type ({\tt LR}, {\tt D} or
{\tt U})- see appendix \ref{subsec_gridtypes}.
\item {\tt \$CFTYP} is the field type: {\tt SCALAR}. The option
{\tt VECTOR}, which in fact leads to a scalar treatment of the
field (as in the previous versions), is still accepted. {\bf
VECTOR\_I or VECTOR\_J, i.e. vector fields, are not supported
anymore in OASIS3-MCT.}. See ``Support of vector fields with
the SCRIPR remappings'' below.
\item {\tt \$REST} is the search restriction type: {\tt LATLON} or
{\tt LATITUDE} (see SCRIP 1.4 documentation SCRIPusers.pdf).
\item {\tt \$NBIN} the number of restriction bins (see SCRIP 1.4
documentation SCRIPusers.pdf). Note that for D or U grid, the
restriction may influence sligthly the result near the borders
of the restriction bins.
\item {\tt \$NV} is the number of neighbours used.
\item {\tt \$ASSCMP}: UNUSED; {\bf vector fields are not supported
anymore in OASIS3-MCT.} See ``Support of vector fields with
the SCRIPR remappings'' below.
\item {\tt \$PROJCART}: UNUSED; {\bf vector fields are not
supported anymore in OASIS3-MCT.} See ``Support of vector
fields with the SCRIPR remappings'' below.
\end{itemize}
\item {\tt GAUSWGT} performs a N nearest-neighbour interpolation
weighted by their distance and a gaussian function. All grid types
are supported.
\begin{itemize}
\item Masked target grid points: the zero value is associated to
masked target grid points.
\item Non-masked target grid points having some of the N source
nearest neighbours masked: a nearest neighbour algorithm using
the remaining non masked source nearest neighbours is applied.
\item Non-masked target grid points having all of the N source
nearest neighbours masked: by default, the nearest non-masked
source neighbour is used (logical {\tt ll\_nnei} hard-coded to
{\tt .true.} in {\tt
oasis3-mct/lib/scrip/src/remap\_gauswgt.F}); {\bf this is NOT
the same default behaviour as OASIS3.3}; to have the same
default behaviour as in OASIS3.3, put {\tt ll\_nnei=.false.}.
\end{itemize}
The configuring line is:
\begin{verbatim}
# SCRIPR (for GAUSWGT)
$CMETH $CGRS $CFTYP $REST $NBIN $NV $VAR
\end{verbatim}
%
% \vspace{-0.5cm}
where:
% $
all entries are as for {\tt DISTWGT}, except that:
\begin{itemize}
\item {\tt \$CMETH = GAUSWGT}
\item {\tt \$VAR}, which must be given as a REAL value (e.g 2.0
and not 2), defines the weight given to a neighbour source grid
point as proportional to $exp(-1/2 \cdot d^2/\sigma^2)$ where
$d$ is the distance between the source and target grid points,
and $\sigma^2 = \$VAR \cdot \overline{d}^2$ where
$\overline{d}^2$ is the average distance between two source grid
points (calculated automatically by OASIS3-MCT).
\end{itemize}
\item {\tt BILINEAR} performs an interpolation based on a local
bilinear approximation (see details in chapter 4 of SCRIP 1.4
documentation SCRIPusers.pdf). Logically-Rectangular (LR) and
Reduced (D) source grid types are supported.
\item {\tt BICUBIC} performs an interpolation based on a local
bicubic approximation for Logically-Rectangular (LR) grids (see
details in chapter 5 of SCRIP 1.4 documentation SCRIPusers.pdf),
and on a 16-point stencil for Gaussian Reduced (D) grids. Note
that for Logically-Rectangular grids, 4 weights for each of the 4
enclosing source neighbours are required corresponding to the
field value at the point, the gradient of the field with respect
to {\it i}, the gradient of the field with respect to {\it j}, and
the cross gradient with respect to {\it i} and {\it j} in that
order. OASIS3-MCT will calculate the remapping weights and
addresses (if they are not already provided) but will not, at run
time, calculate the two gradients and the cross-gradient of the
source field (as was the case with OASIS3.3). These 3 extra fields
need to be calculated by the source code and transfered as extra
arguments of the {\tt oasis\_put} (see {\tt fld2, fld3, fld4} in
section \ref{prismput}).
For both {\tt BILINEAR} and {\tt BICUBIC}:
\begin{itemize}
\item Masked target grid points: the zero value is associated to
masked target grid points.
\item Non-masked target grid points having some of the source
points normally used in the bilinear or bicubic interpolation
masked: a N nearest neighbour algorithm using the remaining non
masked source points is applied.
\item Non-masked target grid points having all bilinear or bicubic
neighbours masked: by default, the nearest non-masked source
neighbour is used ({\tt ll\_nnei} hard-coded to {\tt .true.} in
{\tt oasis3-mct/lib/scrip/src/remap\_bilinear.f}, {\tt
remap\_bicubic.f} and {\tt remap\_bicubic\_reduced.f}); {\bf
this is not the same default behaviour as OASIS3.3}; to have
the same default behaviour as in OASIS3.3, put {\tt
ll\_nnei=.false.} in the appropriate routine.
\end{itemize}
For both {\tt BILINEAR} and {\tt BICUBIC}, the configuring line
is:
\begin{verbatim}
# SCRIPR (for BILINEAR or BICUBIC)
$CMETH $CGRS $CFTYP $REST $NBIN
\end{verbatim}
\vspace{-0.5cm} where:
% $
\begin{itemize}
\item {\tt \$CMETH = BILINEAR} or {\tt BICUBIC}
\item {\tt \$CGRS} is the source grid type: LR or D.
\item {\tt \$CFTYP}, {\tt \$NBIN} are as for {\tt DISTWGT}.
\item {\tt \$REST} is as for {\tt DISTWGT}, except that only {\tt
LATITUDE} is possible for a Reduced (D) source grid.
\end{itemize}
\item {\tt CONSERV} performs 1st or 2nd order conservative
remapping, which means that the weight of a source cell is
proportional to area intersected by the target cell (plus some
other terms proportional to the gradient of the field in the
longitudinal and latitudinal directions for the second order).
The configuring line is:
\begin{verbatim}
# SCRIPR (for CONSERV)
$CMETH $CGRS $CFTYP $REST $NBIN $NORM $ORDER
\end{verbatim}
% $
\vspace{-0.5cm} where:
\begin{itemize}
\item {\tt \$CMETH = CONSERV}
\item {\tt \$CGRS} is the source grid type: LR, D and U. Note that
the grid corners have to given by the user in the grid data file
{\tt grids.nc} or by the code itself in the initialisation phase
by calling routine {\tt oasis\_write\_corner} (see section
\ref{subsubsec_griddef}) ; OASIS3-MCT will not attempt to
automatically calculate them as OASIS3.3.
% For second-order remapping, only LR is supported because the
% gradient of the coupling field used in the transformation has
% to be calculated automatically by OASIS3.
\item {\tt \$CFTYP, \$REST}, {\tt \$NBIN} are as for {\tt
DISTWGT}.
\item {\tt \$NORM} is the NORMalization option:
\begin{itemize}
\item {\tt FRACAREA}: The sum of the non-masked source cell
intersected areas is used to NORMalise each target cell field
value: the flux is not locally conserved, but the flux value
itself is reasonable.
\item {\tt DESTAREA}: The total target cell area is used to
NORMalise each target cell field value even if it only partly
intersects non-masked source grid cells: local flux
conservation is ensured, but unreasonable flux values may
result.
\item {\tt FRACNNEI}: as {\tt FRACAREA}, except that at least
the source nearest unmasked neighbour is used for unmasked
target cells that intersect only masked source cells. Note
that a zero value will be assigned to a target cell that does
not intersect any source cells (masked or unmasked), even with
FRACNNEI option.
\end{itemize}
\item {\tt \$ORDER}: {\tt FIRST} or {\tt SECOND} for first or
second order conservative remapping respectively (see SCRIP 1.4
documentation).
For {\tt CONSERV/SECOND}, 3 weigths are needed; OASIS3-MCT will
calculate these weights and corresponding addresses (if they are
not already provided) but will not, at run time, calculate the
two extra terms to which the second and third weights should be
applied; these terms, respectively the gradient of the field
with respect to the longitude ($\theta$) $\frac{\delta f}{\delta
\theta}$ and the gradient of the field with respect to the
latitude ($\phi$) $\frac{1}{cos \theta}\frac{\delta f}{\delta
\phi}$ need to be calculated by the source code and transfered
as extra arguments of the {\tt oasis\_put} (see {\tt fld2, fld3}
in section \ref{prismput}). Note that {\tt CONSERV/SECOND} is
not positive definite and has not been fully validated yet.
\end{itemize}
\end{itemize}
{\bf Precautions related to the use of the SCRIPR/CONSERV remapping}
\begin{itemize}
\item For the 1st order conservative remapping: the weight of a
source cell is proportional to area of the source cell intersected
by target cell. Using the divergence theorem, the SCRIP library
evaluates this area with the line integral along the cell borders
enclosing the area. As the real shape of the borders is not known
(only the location of the 4 corners of each cell is known), the
library assumes that the borders are linear in latitude and
longitude between two corners. This assumption becomes less valid
closer to the pole and for latitudes above the {\tt north\_thresh}
or below the {\tt south\_thresh} values (see {\tt
oasis3-mct/lib/scrip/remap\_conserv.F}, the library evaluates
the intersection between two border segments using a Lambert
equivalent azimuthal projection. Problems were observed in some
cases for the grid cell located around this {\tt north\_thresh} or
{\tt south\_thresh} latitude.
\item Another limitation of the SCRIP 1st order conservative
remapping algorithm is that is also supposes, for line integral
calculation, that $sin(latitude)$ is linear in longitude on the
cell borders which again is in general not valid close to the
pole.
% A projection or at least a normalization by the
% true area of the cells (i.e. by the areas as considered by the
% component models) is needed.
\item For a proper consevative remapping, the corners of a cell have
to coincide with the corners of its neighbour cell, with no
``holes'' between the cells.
\item If two cells of one same grid overlay, at least the one with
the greater numerical index must be masked for a proper
conservative remapping. For example, if the grid cells with {\it
i=1} overlays the grid cells with {\it i=imax}, the latter must
be masked. If this is not the case given the mask defined in {\it
masks.nc}, OASIS3-MCT must be compiled with the CPP key {\tt
TREAT\_OVERLAY} which will ensure that these rules are
respected. This CPP key was introduced in OASIS3.3.
\item A target grid cell intersecting no source cell (either masked
or non masked) at all i.e. falling in a ``hole'' of the source
grid will in all cases get a zero value.
\item If a target grid cell intersects only masked source cells, it
will still get a zero value unless the {\tt FRACNNEI}
normalisation option is used, in which case it will get the
nearest non masked neighbour value. {\bf Note that the option of
having the value 1.0E+20 assigned to these target grid cell
intersecting only masked source cells (for easier
identification) is not yet availble in OASIS3-MCT.}
% The target grid mask is never considered in {\tt CONSERV},
% except with normalisation option {\tt FRACNNEI} (see below). To
% have a value calculated, a target grid cell must intersect at
% least one source cell. However, the NORMlisation option (that
% takes into account the source grid mask, see below) may result
% in a null value calculated for those target grid cells. In that
% case (i.e. at least one intersecting source cell, but a null
% value finally calculated because of the normalisation option),
% the value 1.0E+20 is assigned to those target grid points if
% {\tt prism/src/lib/scrip/src/scriprmp.f} or {\tt vector.F90}
% (for vector interpolation) are compiled with {\tt
% ll\_weightot=.true.}.
\end{itemize}
% {\bf Precautions related to the use of all SCRIPR remappings}
% \begin{itemize}
% \item For using {\tt SCRIPR} interpolations, linking with the
% NetCDF library is mandatory and the grid data files (see section
% \ref{subsec_griddata}) must be NetCDF files (binary files are
% not supported).
% the weights and addresses will also differ whether or not the
% {\tt MASK} and {\tt EXTRAP} transformations are first activated
% during the pre-processing phase (see section
% \ref{subsec_preproc}) and this option is not stored in the
% remapping file name. Therefore, the remapping file used will be
% the one created for the first field having the same source grid,
% target grid, and interpolation type (and the same normalization
% option for {\tt CONSERV}), even if the {\tt MASK} and {\tt
% EXTRAP} transformations are used or not for that field. (This
% inconsistency is however usually not a problem as the {\tt MASK}
% and {\tt EXTRAP} transformations are usually used for all fields
% having the same source grid, target grid, and interpolation
% type, or not at all.)
% \end{itemize}
{\bf Support of vector fields with the SCRIPR remappings}
Vector mapping is NOT supported and will not be supported by
OASIS3-MCT. For proper treatment of vector fields, the component
model has to send the 3 components of the vector projected in a
Cartesian coordinate system.
\item {\bf INTERP}: UNUSED
\item {\bf MOZAIC}: UNUSED; note that {\tt MAPPING} (see above) is the
NetCDF equivalent to {\tt MOZAIC}.
\item {\bf NOINTERP}: UNUSED
\item {\bf FILLING}: UNUSED
\end{itemize}
\section{The post-processing stage}
\label{subsec_cooking}
\begin{itemize}
\item {\bf CONSERV}:
{\tt CONSERV} ensures a global modification of the coupling field.
This analysis requires the source and target grid mesh areas to be
transfered to the coupler with {\tt oasis\_write\_area} (see section
\ref{subsubsec_griddef}). {\bf For a correct CONSERV operation,
overlapping grid cells on the source grid or on the target grid
must be masked.} In the {\it namcouple}, {\tt CONSERV} requires
one input line with one argument and one optional argument:
\begin{verbatim}
# CONSERV operation
$CMETH $CONSOPT
\end{verbatim}
\vspace{-0.5cm} where:
\begin{itemize}
\item {\tt \$CMETH} is the method desired with the following choices
\begin{itemize}
\item with {\tt \$CMETH = GLOBAL}, the field is integrated on both
source and target grids, without considering values of masked
points, and the residual (target - source) is uniformly
distributed on the target grid; this option ensures global
conservation of the field
\item with {\tt \$CMETH = GLBPOS}, the same operation is performed
except that the residual is distributed proportionally to the
value of the original field; this option ensures the global
conservation of the field and does not change the sign of the
field
\item with {\tt \$CMETH = BASBAL}, the operation is analogous to
{\tt GLOBAL} except that the non masked surface of the source
and the target grids are taken into account in the calculation
of the residual; this option does not ensure global conservation
of the field but ensures that the energy received is
proportional to the non masked surface of the target grid
\item with {\tt \$CMETH = BASPOS}, the non masked surface of the
source and the target grids are taken into account and the
residual is distributed proportionally to the value of the
original field; therefore, this option does not ensure global
conservation of the field but ensures that the energy received
is proportional to the non masked surface of the target grid and
it does not change the sign of the field.
\end{itemize}
\item {\tt \$CONSOPT} is an optional argument specifying the
algorithm. {\tt \$CONSOPT} can be {\tt bfb} or {\tt opt}. The
{\tt bfb} option enforces a bit-for-bit transformation regardless
of the grid decomposition or process count. The {\tt opt} option
carries out the conservation using an optimal algorithm using less
memory and a faster approach. Option {\tt bfb} is the default
setting.
\end{itemize}
\item {\bf SUBGRID}: UNUSED
% {\tt SUBGRID} can be used to interpolate a field from a coarse
% grid to a finer target grid (the target grid must be finer over
% the whole domain). Two types of subgrid interpolation can be
% performed, depending on the type of the field.
%
% For solar type of flux field ({\tt \$SUBTYPE = SOLAR}), the
% operation performed is:
%$$\Phi_{i} = \frac{1-\alpha_i}{1-\alpha} F$$ where $\Phi_{i}$ ($F$) is
%the flux on the fine (coarse) grid, $\alpha_i$ ($\alpha$) an
% auxiliary field on the fine (coarse) grid (e.g. the albedo). The
% whole operation is interpolated from the coarse grid with a
% grid-mapping type of interpolation; the dataset of weights and
% addresses has to be given by the user.
%
% For non-solar type of field ({\tt \$SUBTYPE = NONSOLAR}), a
% first-order Taylor expansion of the field on the fine grid
% relatively to a state variable is performed (for instance, an
% expansion of the total heat flux relatively to the SST):
%$$\Phi_{i} = F + \frac{\partial F}{\partial T} ( T_i - T ) $$ where
%$\Phi_{i}$ ($F$) is the heat flux on the fine (coarse) grid, $T_i$
% ($T$) an auxiliary field on the fine (coarse) grid (e.g. the SST)
% and $\frac{\partial F}{\partial T}$ the derivative of the flux
% versus the auxiliary field on the coarse grid. This operation is
% interpolated from the coarse grid with a grid-mapping type of
% interpolation; the dataset of weights and addresses has to be given
% by the user.
%
% This analysis requires one input line with 7 or 8 arguments
% depending on the type of subgrid interpolation.
%
% \begin{enumerate}
% \item If the the {\tt SUBGRID} operation is performed on a solar
% flux, the 7-argument input line is:
%\begin{verbatim}
%# SUBGRID operation with $SUBTYPE=SOLAR
% $CFILE $NUMLU $NID $NV $SUBTYPE $CCOARSE $CFINE\end{verbatim}where
%{\tt \$CFILE} and {\tt \$NUMLU} are the subgrid-mapping file name and
%associated logical unit (see section \ref{subsec_transformationdata} for the
%structure of this file); {\tt \$NID} the identificator for this
%subgrid-mapping dataset within the file build by OASIS based on all
%the different {\tt SUBGRID} analyses in the present coupling; {\tt
%\$NV} is the maximum number of target grid points use in the
%subgrid-mapping; {\tt \$SUBTYPE = SOLAR} is the type of subgrid
% interpolation; {\tt \$CCOARSE} is the
%auxiliary field name on the coarse grid (corresponding to $\alpha$)
%and {\tt \$CFINE} is the auxiliary field name on fine grid
%(corresponding to $\alpha_i$).
%These two fields needs to be exchanged between their original model
%and OASIS3 main process, at least as {\tt AUXILARY} fields.
%This analysis is performed from the coarse grid with a grid-mapping type
%of interpolation based on the {\tt \$CFILE} file.
%
% \item If the the SUBGRID operation is performed on a nonsolar flux,
% the 8-argument input line is:
%\begin{verbatim}
%# SUBGRID operation with $SUBTYPE=NONSOLAR
% $CFILE $NUMLU $NID $NV $SUBTYPE $CCOARSE $CFINE $CDQDT
%\end{verbatim} where {\tt \$CFILE}, {\tt \$NUMLU}, {\tt \$NID},
%{\tt \$NV} are as for a solar subgrid interpolation; {\tt
%\$SUBTYPE = NONSOLAR}; {\tt \$CCOARSE} is the auxiliary
%field name on the coarse grid (corresponding to $T$) and {\tt \$CFINE}
%is the auxiliary field name on fine grid (corresponding to $T_i$); the
%additional argument {\tt \$CDQDT} is the coupling ratio on the coarse
%grid (corresponding to $\frac{\partial F}{\partial T}$) These three
%fields need to be exchanged between their original model and OASIS3
%main process as {\tt AUXILARY} fields. This operation is performed from the
%coarse grid with a grid-mapping type of interpolation based on the {\tt
%\$CFILE} file.
%
% \end{enumerate}
\item {\bf BLASNEW}:
{\tt BLASNEW} performs a scalar multiply or scalar add to any
destination field. This is the equivalent of BLASOLD on the
destination side. The prior feature that supported linear
combinations of the current coupling field with any other fields
after the interpolation has been deprecated.
This analysis requires the same input line(s) as {\tt BLASOLD}.
\item {\bf MASKP}: UNUSED
\item {\bf REVERSE}: UNUSED
\item {\bf CHECKOUT}:
{\tt CHECKOUT} calculates the global minimum, the maximum and the
sum of the target field values (not weighted by the grid cell area)
and prints them to the OASIS3-MCT debug file (for the master process
of the target component model only). These informations are found in
the debug file of the master process of the target model under the
attribute ``diags''. This operation does not
transform the field. The generic input line is as for {\tt CHECKIN}
(see above).
\item {\bf GLORED}: UNUSED
\end{itemize}
|