next up previous contents index
Next: Bibliography Up: $FILE Previous: 1. Scientific documentation   Contents   Index

Subsections


2. User's guide

2.1 Perform a MODEL-run with Lagrangian tracers

(See also the MesoNH User's Guide Chapter 4.)

No specific operation is needed in the preliminary stages of a MesoNH simulation (generation of the initial and coupling files) until the model itself is started (MAINPROG=MODEL in procedure prepmodel).

The following parameters must be set in the namelist file EXSEG1.nam.

Activation

Initialization - Reinitializations

Dynamical options

2.2 Compute DIAGnostics involving Lagrangian tracers

(See also the MesoNH User's Guide Chapter 6.)

The involved parameters in the namelist file DIAG1.nam are in namelists NAM_DIAG and NAM_STO_FILE.

2.2.0.0.1 Main switch

!!! Warning !!!
If LTRAJ=.FALSE. the Lagrangian tracers will be absent in the output diachronic file.

2.2.0.0.2 Basic DIAGnostics

In the most simple case, the Lagrangian tracers were initialized at the model START then no reinitialization occurred during the run (case LINIT_LG=.FALSE. or simulation without RESTART).

If so, set LTRAJ=.TRUE. but keep the namelist NAM_STO_FILE empty. The present groups in the output diachronic file will be: LGXM, LGYM, LGZM, X and Y.

2.2.0.0.3 Advanced DIAGnostics

A specific post-processing whose specifications have to be prescribed in namelist NAM_STO_FILE, may be useful or even necessary in two cases:

Important remark : This post-processing can also be performed on Linux PC independently from, and after, the program DIAG with the specific program compute_r00_pc available with the package of "tools related to MesoNH" (www.aero.obs-mip.fr/mesonh/dir_doc/tools_21mar2005/tools/tools.html). This way may be more convenient and more flexible in most cases, and is recommended whenever possible.

The latter program works with diachronic files from DIAG as input and modifies them to add supplemental groups. These input files must contain the groups LGXM, LGYM, LGZM, that are obtained with DIAG as indicated just above (i.e., in DIAG1.nam: LTRAJ=.TRUE. in NAM_DIAG; empty namelist NAM_STO_FILE).

Please see the documentation on compute_r00_pc for specific use, but note that this program does exactly the same job as DIAG, and that the required input namelists are almost the same. The content is described below for DIAG.


2.2.1 Case (1): Catenation of evolution fragments back to the model start

It has been shown in §1.2.3 that even if reinitializations of the Lagrangian tracer fields occurred during the model run (at every restart), it is possible to retrieve the Lagrangian history back to the model start.

This can be done with the following paradigmatic example for file DIAG1.nam.

&NAM_DIAG ......., LTRAJ=.TRUE. /
&NAM_DIAG_FILE      YSUFFIX='t0'
,YINIFILE(1) = "SIMUL.1.SEG04.001"
,YINIFILE(2) = "SIMUL.1.SEG03.001"
,YINIFILE(3) = "SIMUL.1.SEG02.001"
,YINIFILE(4) = "SIMUL.1.SEG01.001"
,YINIFILE(5) = "INIT_MNH_FILE"
/
&NAM_STO_FILE
 CFILES(1) = "SIMUL.1.SEG04.001",
 CFILES(2) = "SIMUL.1.SEG03.001",
 CFILES(3) = "SIMUL.1.SEG02.001",
 CFILES(4) = "SIMUL.1.SEG01.001",
 CFILES(5) = "INIT_MNH_FILE",
 NSTART_SUPP(1)=4,
 NSTART_SUPP(2)=2
/

In the example the simulation has been performed in 4 segments with output files (*.001) at segment ends only.

2.2.1.0.1 Input

In the following, $t(n)$ is the time of the currently treated file YINIFILE(n), and $t_{i}$ the times of the model restarts (start at $t_0$).

Following the catenation process of §1.2.3 (Fig.1.1), one needs at each step to know at restart time $t_i$ the initial location of the Lagrangian parcels at the previous restart time $t_{i-1}$. This is precisely the information given by the LGXT, LGYT, LGZT fields at time $t_i$.

Thus for the catenation process of file YINIFILE(n) back to time $t_0$, programme DIAG needs to have all the restart-time files prior to time $t(n)$ as input (of course in addition to file YINIFILE(n)). This is the purpose of the STOrage namelist NAM_STO_FILE. Since the catenation process goes back in time, these files have to be anti-chronologically ordered.

Important remarks:

  1. In the present (Masdev4_5 Bug2) and previous versions of MesoNH, YINIFILE(n) MUST EXACTLY MATCH CFILES(n) for any $n$.
  2. Consequently YINIFILE(n) are obligatorily restart-time files2.2and thence catenated Lagrangian evolutions computed with DIAG necessarily end in coincidence with simulation segments2.3.

2.2.1.0.2 Output

In the above example, DIAG will produce the following fields

Remark : If using the "tool" compute_r00_pc on Linux PC, it is possible to choose not only $\theta$ and $r_v$, but also any other quantity present in the diachronic input file (and also potential vorticity even if not present) - see the specific documentation on the MesoNH www for details. This possibility will be implemented in DIAG in a forthcoming bugfix of MesoNH.

If at any step of the catenation process a Lagrangian parcel is found to originate from outside the model domain, this parcel is flagged in the resulting fields X000 ... RV000 as "coming from outside"2.4 with the special value -1.E+11 (that will be later recognized by DIAPROG - see XSPVAL).


2.2.1.0.3 Supplementary time origins

It is possible to produce supplementary sets of 'initial' coordinates with other time origins among the $t_i$'s (simply by means of intermediate records during the catenation process Eq.1.7-1.9). This is the purpose of the variable NSTART_SUPP(:).

For the above example of namelist, the following two sets of fields will be produced:


2.2.2 Case (2): Initial value of physical variables

In this example, the simulation has been performed without run-time reinitialization (LINIT_LG= .FALSE.) of the Lagrangian tracers, which were initialized at the model start (file INIT_MNH_FILE).

&NAM_DIAG ......., LTRAJ=.TRUE. /
&NAM_DIAG_FILE      YSUFFIX='t0'
,YINIFILE(1) = "SIMUL.1.SEG04.003"
,YINIFILE(2) = "INIT_MNH_FILE"
/
&NAM_STO_FILE
 CFILES(1) = "SIMUL.1.SEG04.003",
 CFILES(2) = "INIT_MNH_FILE"
/

DIAG will produce the following fields:

2.3 Make Lagrangian analyses with DIAPROG

For most plots allowed by DIAPROG and involving the Lagrangian tracers, it is necessary to make the following variable initializations:

2.3.1 Conventional plots

The fields present in the considered diachronic input file (thereafter "groups") and in relation with the initial coordinates method, namely LGXM, LGYM, LGZM, X00n, Y00n, Z00n, TH00n, RV00n, can of course be plotted as any other conventional group with DIAPROG: 2D horizontal or vertical cross-sections, horizontal or vertical profiles, etc. (see the DIAPROG Documentation). Examples are given here that may have some common interest for MesoNH users.


2.3.1.1 Horizontal cross-sections

Figure 2.1: : Examples of conventional horizontal plots of initial coordinate fields.
\includegraphics[angle=0, width=\textwidth, keepaspectratio=true,clip=true]{figdocu/sudtessin.eps}

Figure 2.1(a) shows the initial altitude $z_0$ of the parcels present at the altitude $z=7000$m in the case of a developing baroclinic wave over western Europe. The initial altitude is here shot after a 18-hours model-run without run-time reinitialization. Parcels in the ascent ahead of the trough originate from altitudes below 7000m and thus have $z_0<7000$m (colors blue to green). Parcels in the descent of upper-level air behind the trough originate from altitudes above 7000m and thus have $z_0>7000$m (colors light green to purple). It is noteworthy that such a plot enables to immediately identify coherent air-masses (here the rising warm-conveyor belt ahead of the trough or the upper-level air intrusion behind it) without any kind of parcel preselection (as otherwise needed in classical trajectory-based methods). The colored plot is here obtained with the following commands:

LCOLAREA=T LISO=F
NIMNMX=1
XISOMIN_LGZM=4.500 XISOMAX_LGZM=9.500 XDIAINT_LGZM=.250
LCOLZERO=T
NCOLZERO=12
LGZM(*.001)_Z_7000

Superimposition of other fields (here $PV$ contours and wind arrows) can be obtained in the classical way (LGZM(*.001)_Z_7000_ON_...).

Remark the factor $(*.001)$ that turns the initial altitude into kilometers.

Figure 2.1(b) shows the initial ordinate $y_0$ of the parcels on the isentrope $\theta=315$K after the same 18-hours evolution. This plot makes strikingly visible the southwards intrusion of subpolar air (high values of $y_0$, colors yellow to purple) behind the trough and the northwards intrusion of subtropical air (low values of $y_0$, colors blue to green) ahead of the trough. The strong gradient of $y_0$ off the eastern shore of Spain indicates the close proximity of air masses with very different geographical origins. This reveals there active frontogenesis2.5.

The colored plot is here obtained with the following commands

LISO=T LCOLINE=T
NIMNMX=1
XISOMIN_LGYM=-1000000 XISOMAX_LGYM=4750000 XDIAINT_LGYM=250000
LGYM_TH_315

Handling millions of meters can be avoided by conversion into kilometers in the following way.:

...
XISOMIN_LGYM=-1000 XISOMAX_LGYM=4750 XDIAINT_LGYM=250
LGYM(*.001)_TH_315


2.3.1.2 Vertical cross-sections

Figure 2.2: : Example of vertical cross-section showing the initial altitude. The solid contour is the iso-$z_0=1.5$km, which can be viewed as the intersection with the section plane of a material surface initially horizontal then driven upwards by the convective plume. The color scale represents the total water content $r_t$ (in g.kg$^{-1}$).
\includegraphics[angle=0, width=\textwidth, keepaspectratio=true,clip=true]{figdocu/cumulus.eps}

Figure 2.2 exemplifies how the Lagrangian tracer $z_0$ can capture the dynamics of a convective plume. The simulation uses a reversible microphysical cycle (i.e., without precipitation) so that the total water content $r_t=r_c+r_v$ (cloud water + vapor) is conserved by the flow. The simulation is started with a horizontally uniform $r_t$ distribution. Therefore the $r_t$ surfaces are expected to coincide with $z_0$ surfaces, what is well shown in the figure, where the $z_0$-contour encompasses the wet plume which develops in the shape of a mushroom. The plot is here obtained with the following commands (after having appropriately defined the vertical cross-section and specified the color-scale parameters for $r_t$ in the classical way).

XISOMIN_LGZM=1.5 XISOMAX_LGZM=1.5 XDIAINT_LGZM=1
MRC_CV__PLUS_MRV_CV__ON_LGZM(*.001)_CV_

Figure 2.3: : Vertical cross-section along an organized convection line, showing the net vertical displacement $\Delta z=z-z_0$ of the Lagrangian parcels over 30 min (color areas, $\Delta z$ in km). The quasi-horizontal line is the $0^\circ $C-isotherm.
\includegraphics[angle=0, width=0.5\textwidth, keepaspectratio=true,clip=true]{figdocu/LDCPo.eps}

As second example, Figure 2.3 shows the vertical Lagrangian displacement over 30 min in a vertical cross-section along an organized orographically triggered convection line. The net vertical displacement is $\Delta z=z-z_0$, where $z_0$ is the initial altitude of the Lagrangian parcel 30 min before. The ambient flow is from left to right. The weak positive values at low-levels over the upwind side of the first relief correspond to orographic uplift. This triggers deep convection cells rising up to the tropopause. These deep ascents are signed by the high positive values of $\Delta z$ at high-levels. Organized low-level subsidence (negative values) is also well visible more downstream over the plain, due to convective downdrafts.

In this simulation, reinitializations of the Lagrangian tracers were made every 5 min and a catenation has been performed in order to retrieve the 30min-evolution. The group used in DIAPROG for $z_0$ is in this case the catenation result Z000. The command sequence for this plot is as follows (after having appropriately defined the vertical cross-section in the classical way):

...
LISO=T LCOLAREA=T
LCOLZERO=T
NCOLZERO=8
XISOMIN_Z000=-3.250 XISOMAX_Z000=9.750 XDIAINT_Z000=.500
ALT(*.001)_CV__MINUS_Z000(*.001)_CV_

Remark: Horizontal displacement can also be plotted using the fields X and Y (that are available as soon as the Lagrangian tracers are) and the operator _MINUS_, for example

X_CV__MINUS_X000_CV_
Y_CV__MINUS_Y000_CV_

2.3.2 Horizontal plots on iso-surfaces

2.3.2.1 Iso-$z_0$

Unlike the potential temperature or vorticity, the initial altitude $z_0$ (given by LGZM or Z00n) is by definition a conserved quantity even in complex (in particular, highly diabatic) atmospheric flows.

DIAPROG allows to plot any group from the input diachronic file on iso-$z_0$ surfaces - just as one can make plots on isobar, iso-$\theta$, iso-$PV$, etc. , surfaces. Iso-$z_0$'s have the advantage to be true material surfaces (unlike iso-$\theta$ or iso-$PV$ that are only approximately material surfaces), that are initially horizontal then deformed by the flow (as in the vertical cross-sections of Fig.2.2).

Such plots are exemplified in Fig.2.4. Panels (a-b) show the actual altitude $z$ of the points of the material surface $z_0=2000$m 1 and 4 hours after initialization of the tracer $z_0$. Coherent ascendant (subsident) air-masses are well visible as regions with actual altitudes greater (resp. lower) than the initial altitude 2000 m.

Figure 2.4: Lagrangian evolution (time origin for the evolution: $t_0=21$ UTC) for a real-case simulation over the western Mediterranean. Horizontal plots on the isosurface $z_0=2000$ m. (a,b) color scale: altitude $z$(m) of the surface points. Contours: 5 mm/h instantaneous rain rate. Arrows: wind $>20$ m/s. (c,d) color scale: Lagrangian net diabatic change $\Delta \theta =\theta -\theta _0$(K). Contours: rain droplet mixing ratio $>0.05$ g/kg. Arrows: wind $>20$ m/s.
\includegraphics[angle=0, width=\textwidth, keepaspectratio=true,clip=true]{figdocu/z00.eps}

A horizontal plot of a group on an iso-$z_0$ surface, e.g., $z$ on a $z_0=2000$ m isosurface as in Fig.2.4, is produced by DIAPROG upon request of type

ALT_SV3_2000
(altitude to be prescribed in m).

Figures 2.4(c-d) show the net diabatic change $\theta-\theta_0$ on the same $z_0=2000$m surface. It reveals that the ascendant air-masses have experienced strong diabatic heating (these bands indeed accompany frontal rain production) while the air-pool that has subsided down to the Gulf of Genoa has experienced significative cooling. Figures 2.4(c-d) are obtained with

THM_SV3_2000_MINUS_TH000_SV3_2000_ON_&
RVM_SV3_2000_ON_UMVM_SV3_2000

Options for plots on iso-$z_0$ surfaces can be precised with setting the variables LXYZ00 and CGROUPSV3 appropriately.

Case LXYZ00=F (default)
LGZM is used as $z_0$, i.e., the plot is on a material surface deformed since the most recent model RESTART (or START if no reinitialization of the Lagrangian tracers meanwhile).

Case LXYZ00=T
The group that has to be used as $z_0$ is prescribed with the (character) variable CGROUPSV3. For instance

LXYZ00=T
CGROUPSV3='Z001'
THM_SV3_1500
allows to choose the time origin for the material surface evolution among the $t_i$'s corresponding to the Z00i's (if computed by DIAG - see §2.2).


2.3.2.2 Other isosurfaces

The above possibility remains available for any kind of group precised in variable CGROUPSV3. For instance

LXYZ00=T
CGROUPSV3='TH000'
THM_SV3_300
plots the potential temperature on the iso-$\theta_0=300$K surface, i.e., the material surface that coincided with the isentrope 300 K at the initial time $t_0$. This example may be of interest since it provides whether the Lagrangian parcels of the considered surface have been diabatically cooled or heated, and how much.

The group precised in CGROUPSV3 can as well have nothing to do with Lagrangian considerations. For example

LXYZ00=T
CGROUPSV3='REHU'
THM_SV3_90
simply plots the potential temperature on a surface defined by a relative humidity of 90%.

Remarks

  1. Horizontal plots on an isosurface make sense only if there is a one-to-one relationship between altitude and quantity $\alpha$ defining the isosurface. However in case of an overturned isosurface there may be several points on a vertical corresponding to a given value of $\alpha$. To avoid such an ambiguity DIAPROG will choose the highest occurrence of $\alpha$ on the considered vertical. (For that reason fields plotted on an overturned isosurface may appear as discontinuous functions of the horizontal coordinates.)
  2. If there is no occurrence found on a vertical, the plot will appear as non-valued at this location.
  3. By default the number following _SV3_ must be INTEGER. However LCHREEL=T (default=F) allows the use of REAL values.

2.3.3 Lagrangian parcel plumes

DIAPROG allows to track an ensemble of Lagrangian parcels that are initially contained in a box prescribed by the user, in the form of a plume of stars.

The box is defined by prescription of the minimum and maximum Cartesian coordinates of the points within the box:

XXL=x_min XXH=x_max
XYL=y_min XYH=y_max
XZL=z_min XZH=z_max
All six values have to be given in meters. You can use convij2xy or convxy2ij to convert grid indices or geographical coordinates (lat,lon) into the required Cartesian coordinates (see DIAPROG documentation).

DIAPROG computes a 3D mask corresponding to true occurrences for the condition:
( $XXL<x_0(x,y,z,t)<XXH$) AND ( $XYL<y_0(x,y,z,t)<XYH$) AND ( $XZL<z_0(x,y,z,t)<XZH$).

(This condition can be simply interpreted as "the Lagrangian parcel currently considered was initially present in the box".)

Again the time origin for $x_0$, $y_0$, $z_0$ can be either the instant of the most recent RESTART (LGXM, LGYM, LGYM used - default option) or an earlier START or RESTART instant. For the latter case one has to precise which from the (X00i,Y00i,Z00i)'s have to be used, in the same manner as for plots on $z_0$ isosurfaces. For instance

LXYZ00=T
CGROUPSV3='Z002'
allows to use X002,Y002,Z002 as $x_0$, $y_0$, $z_0$.

The plots show both the initial box and a plume of stars marking the true occurrences of the mask (i.e., the Lagrangian parcels from the box) at the current time, in projections onto the three Cartesian planes $xy$ (horizontal), $xz$ (vertical W-E) and $yz$ (vertical S-N). Examples are given in figures 2.5(a-d).

After definition of a mask (XXL=,..., XZH=), such plots are obtained with the following commands:

These three plots (in the above order) can also be produced together with the single command LMASK3D=T.

The plot domains are controlled with the classical parameters: NIINF, NISUP, NJINF, NJSUP, XHMIN, XHMAX (XZ plots delimited with NIINF, NISUP, XHMIN, XHMAX; YZ plots delimited with NJINF, NJSUPF, XHMIN, XHMAX).

Plots on mask top

After definition of a mask, it is also possible to plot in horizontal projection the value of any 3D group on the top of the particle plume (i.e., at any point of true occurrence of the mask condition, and of maximum altitude on a given vertical). For example

ALT_MSKTOP__K_2
plot the value of the altitude (ALT) of the mask top (the suffix _K_2 makes no sense but is necessary for the syntax).

As default option the field is plotted with isocontours. However this requires a minimum of four contiguous 'true' points. Thus the value of the considered group on isolated 'true' points does not appear in an isocontoured plot. It is however possible to visualize it in the form of a plume of colored stars instead of contours:

LMARKER=T
THM_MSKTOP__K_2
(same color scale as for the contours). Examples of both options are given in figure 2.5(e-f). Remark the apparently reduced size of the plume when LMARKER=F.

Figure 2.5: (a-c) Plume of particles that were in the plotted box 12h earlier: (a) Horizontal ($xy$) projection plane; (b) $xz$ (W-E) vertical plane; (c) $yz$ (S-N) vertical plane. (d) As in (a) but after a 24h evolution. (e,f) Altitude of the mask top (color scale, in m): (e) option LMARKER=T; (f) option LMARKER=F.
\includegraphics[angle=0, width=\textwidth, keepaspectratio=true,clip=true]{figdocu/plume.eps}

Figure 2.5 is obtained with the following sequence:

XHMIN=0
XHMAX=12000
!
NIGRNC=5
L2CONT=T
XLWCONT=1
!
XXL=300000 XXH=900000
XYL=3000000 XYH=3600000
XZL=4000 XZH=8000
!
! use of tracers initialized on 09 February 2002 at 12 UTC
! (triplet X000,Y000,Z000)
!
LXYZ00=T
CGROUPSV3='Z000'
!
! Panels (a-c)
!
_file1_'FRANK.1.10_00.002_d12'
LMASK3D=T
!
! Panel (d)
!
_file2_'FRANK.1.10_12.002_d12'
LMASK3D_XY=T
!
LISO=F LCOLAREA=T
NIMNMX=2
XISOLEV=1000,2000,3000,4000,5000,6000,7000,8000,9999.
!
! Panel (e)
!
LMARKER=T
ALT_MSKTOP__K_2
!
! Panel (f)
!
LMARKER=F
ALT_MSKTOP__K_2

Remarks

  1. L2CONT=T is needed to superimpose the continents to horizontal plots.
  2. The axes of a horizontal plot can be labelled in meters instead of gridpoint indices (default option): LINDAX=F LGEOG=F and set NCHPCITVXMJ=, NCHPCITVYMJ=, NCHITVXMJ=, NCHITVYMJ= to change the label interval (see DIAPROG Documentation for details).
  3. Users may be interested in superimposing the plots at different times for a given Lagrangian plume in order to track its evolution. It is not possible directly with DIAPROG. However a software for that purpose is available from the support team at Meteo-France - please contact Nicole Asencio (Nicole.Asencio@meteo.fr).


2.3.4 Backtrajectories

As noted in §1.2.3, the algorithm of Eq.1.7-1.9 (sketched in Fig. 1.1) can also be used with DIAPROG to compute backtrajectories.

As the Lagrangian tracers at every RESTART times in the considered while are required, DIAPROG needs to open several files simultaneously that must be ordered ANTICHRONOLOGICALLY.

For example we consider a simulation with 6-hourly spaced restarts on 09 and 10/02/2002. For the while 12UTC - 12UTC the loading sequence is as follows:

_file1_'SIMUL.1.10_12.001'
_file2_'SIMUL.1.10_06.001'
_file3_'SIMUL.1.10_00.001'
_file4_'SIMUL.1.09_18.001'
_file1__file2__file3__file4_
Note that the file on 09/10, 18 UTC contains the location of the parcels 6 hours earlier, so the file on 09/02, 12 UTC is not needed for trajectories back to that time.

The coordinates of the end points for one or several backjectories are specified in three lists XXPART, XYPART, XZPART corresponding to the abscissas, ordinates and altitudes of the end points. The lists must have matching numbers of elements and be ended with '9999.'. For example for specifying N backtrajectories:

XXPART=x1,x2,x3,...,xN,9999.
XYPART=y1,y2,y3,...,yN,9999.
XXPART=z1,z2,z3,...,zN,9999.
These coordinates must all be expressed in meters. (convij2xy or convxy2ij can be helpful, see DIAPROG documentation.)

Three plots in the projection planes $xy$ (horizontal), $xz$ (vertical W-E) and $yz$ (vertical S-N) are produced (in this order) with the command

LTRAJ3D=T
(automatically set back to false after computation).

A trajectory appears as a chain of stars marking the successive locations of the considered Lagrangian parcel at the RESTART times, and connected to each other with segments (the end point appears as a small circle instead of a star), as illustrated in figures 2.6(a,c,e).

If several trajectories are requested in the same plot (N>1), each single trajectory appears with its own color.

Remarks

  1. L2CONT=T is needed to superimpose the continents to horizontal plots.
  2. As for parcel plumes the domains for the $xy$, $xz$ and $xz$ projections are controlled by the parameters NIINF, NISUP, NJINF, NJSUP, XHMIN, XHMAX.


Evolution of physical variables

It is possible to track along the parcel trajectory the evolution of any 3D group present in the considered diachronic files. This group must be specified in variable CTRAJ_GROUP and the option is activated with LTRAJ_GROUP. For example to track the potential temperature of the Lagrangian parcel:

LTRAJ_GROUP=T
CTRAJ_GROUP='THM'
LTRAJ3D=T
This results in six plots ordered as for the example in figure 2.6.

For tracking another group it is necessary to change CTRAJ_GROUP then to request again the trajectory computation (LTRAJ3D=T).

Figure 2.6: Example of backtrajectory with group tracking. (The times indicated in (a) do not appear on plots.) (a,b) Horizontal ($xy$) projection plane. (c,d) $xz$ (W-E) vertical plane. (e,f) $yz$ (S-N) vertical plane.
\includegraphics[angle=0, width=\textwidth, keepaspectratio=true,clip=true]{figdocu/trajFrancfort.eps}

In summary, the example (Fig.2.6) is produced with the following sequence:

!
! loading sequence
!
_file1_'SIMUL.1.10_12.001'
_file2_'SIMUL.1.10_06.001'
_file3_'SIMUL.1.10_00.001'
_file4_'SIMUL.1.09_18.001'
_file1__file2__file3__file4_
!
! end point(s) prescription (only one trajectory in this example)
!
XXPART=2850000,9999.
XYPART=2300000,9999.
XZPART=   4800,9999.
!
! plot options
!
XHMIN=0
XHMAX=12000
NIGRNC=5
L2CONT=T
XLWCONT=1
!
! request of trajectory(ies) with potential temperature tracking
!
LTRAJ_GROUP=T
CTRAJ_GROUP='THM'
LTRAJ3D=T


2.3.5 Streamlines (stationary flows only)

For stationary flows streamlines strictly coincide with trajectories. So, under the hypothesis that the flow varies only little between the time when the Lagrangian tracers were initialized and the current time -and ONLY under this hypothesis-, it makes sense to use the current Lagrangian tracer fields in recursive loop in the algorithm Eq.1.7-1.9 in order to obtain streamlines.

The end points of the streamlines are specified in the same way as for backtrajectories with XXPART, XYPART, XZPART.

The computation of streamlines is performed upon the following command sequence:

_file1_'SIMUL.1.02UTC.001'
_file1__file1_
XXPART=x1,x2,x3,...,xN,9999.
XYPART=y1,y2,y3,...,yN,9999.
XXPART=z1,z2,z3,...,zN,9999.
!
! (possibly)
L2CONT=T
!
LFLUX3D=T

In the example the flow must be quasi-stationary between 02 UTC and the prior restart. DIAPROG uses the fields LGXM, LGYM, LGZM 100 times in loop to compute streamlines backwards from the prescribed end points. As for backtrajectories, three plots are generated in the $xy$, $xz$, $yz$ projection planes with identical appearance.


next up previous contents index
Next: Bibliography Up: $FILE Previous: 1. Scientific documentation   Contents   Index
Jean-Pierre CHABOUREAU 2005-05-13