Description of the output of the KNMI Trajectory Model TRAJKS version 31-03-2000 Documentation-Rinus Scheele / Peter van Velthoven 14-06-2000 A trajectory file consist of a number of subsequent trajectories The data for a trajectory consist of a header and a body: ------------------------------------------------------------------------------- HEADER The header is one line and has the format: (A1,A2,I3,1X,I8.8,1X,I8.8,1X,I8.8,I3,I4,3I5,I4.2,2f5.1,f9.4) Example of a header for backward trajectories (111299_h_TR): WTK 1 99121206 99121207 99120707 -1 121 796 76 571 06 1.0 1.0 -0.7500 Contents: mTK lp yymmddh1 yymmddh2 yymmddh3 ts npt LON LAT PRES DT DX DY frac Another example of a header for backward trajectories (year 2000): WTK 1 20906 20908 20408 -1 121 736 49 518 06 1.0 1.0 -0.6000 mTK lp yymmddh1 yymmddh2 yymmddh3 ts npt LON LAT PRES DT DX DY frac Explanation: m : mode of the trajectory model: W: uses the 3D wind field (W is vertical velocity DP/DT) TK : Updated KNMI trajectorie model TRAJKS lp: number of calculation timesteps within one hour. yymmddh1: last analysis time used (used for administration) Last analysis means the newest analysis time as found in the input data. Remark: each parameter at an instant is calculated from data at 3 6-hourly times, because of the time interpolation. Remark: if first guess is used, this gives an extra shift in the last analysis time compared to the hour. If e.g the calculaton starts at 18 GMT, using 6 hourly FG data. Last analysis will then be 18 -6 -6 = 06 GMT. yymmddh2: start time of trajectory calculation yymmddh3: end time of trajectory calculation ts : trajectory timestep in hours (usually 1 or -1) npt: number of points = the number of lines in the body LON, LAT, PRES = coordinates of begin point trajectory LON and LAT are in 0.1 degrees , press in hPa DT : time interval between subsequent windfields in hours (usually 06) DX : grid longitude distance in degrees DY : grid latitude distance in degrees frac : time correction of start time : fraction of an hour. Remark : the exact verification time is calculated from yymmddh2 + frac Remark : if frac is not 0.000, then all (hourly) output instants are shifted in time compared to the full hour yymmddhh2. ----------------------------------------------------------------------------- BODY The body consists of npt (see header) lines describing each one trajectory position: TTTT PRES0 LON LAT PRES U V W T q PV dPV CF CP errflg Unfortunately 2 slightly different formats were used in the course of CARIBIC: ----------------------------------------- *** Up to the June 2000 CARIBIC flights The body consists of lines describing each one trajectory position: The format of a line is: 4X,I7,I6,2I5,I6,7I7,I4,I5,I7 Here follows an example of the first three lines (traj. positions): -45 10037 796 76 5716 -18 31 -10 2735 5400 420 -54 5 0 0 -105 10017 797 75 5720 -21 25 -10 2735 5529 438 -52 10 0 0 -165 9994 797 74 5721 -24 16 0 2735 5629 468 -53 17 -1 0 Contents: TTTT PRES0 LON LAT PRES U V W T q PV dPV CF CP errflg format: 4x I7 I6 I5 I5 I6 I7 I7 I7 I7 I7 I7 I7 I4 I5 I7 ----------------------------------------- *** After July 2000 the CF and CP parameters were removed form the output of the standard trajectory model and the output lines are: The format of a line is: 4X,I7,I6,2I5,I6,7I7,I7 or: Here follows an example of the first three lines (traj. positions): -44 10082 737 42 10082 42 6 -2 3012 17512 -51 -63 3 -104 10078 735 42 10078 40 9 4 3011 17652 -52 -67 3 -164 10077 734 41 10076 40 10 7 3011 17730 -56 -74 1 Contents: TTTT PRES0 LON LAT PRES U V W T q PV dPV errflg format: 4x I7 I6 I5 I5 I6 I7 I7 I7 I7 I7 I7 I7 I7 ----------------------------------------- Explanation TTTT : time in minutes relative to start time yymmddhh2 PRES0 : pressure at bottom of model=surface (0.1 hPa) LON, LAT : horizontal trajectory position (in 0.1 degrees) PRES : vertical trajectory position (0.1 hPa) U, V : horizontal winds in EW resp. NS direction at trajectory position (in 0.1 m/s) W : vertical wind at trajectory position (in mPa/s) T : temperature in 0.1 K q : moisure mixing ratio in mg / kg PV : Potential vorticity in 0.001 PVU (1 PVU = 10**-6 K m**2 / kg / s ) dPV/dp : Potential vorticity gradient in PVU/Pa errflg : error flag. See below. ------------------------------------------ ERROR FLAG errflg description The error flag is an integer. If errflg=0 everything is OK. errflg is composed as 10000*nit + 100*ntf + cDT + sh. sh : surface hit. Or top layer hit. sh =1: trajectory below lowest model level. sh =3: trajectory below surface pressure : this has been corrected by lifting the point to the the surface pressure This occurs often at the take-off or landing of the aircraft sh =2: trajectory above the highest model level. sh =4: trajectory above the highest layer: P < 0. In all four cases, the trajectory goes on, using the uppermost resp. lowermost level data. cDT : 0(no) or 70(jump): An input data timestep jump from 6 to 12 hours occurred ( implemented for X,J W forward runs only) nit: number of times that the iteration-scheme failed (did not converge) within an hour. Remember that the iteration procedure is repeated for every calculation time-step. ntf: number of times that no unique theta-level, or theta-E-level was found. Remember that the search procedure is executed before time interpolation. For format reasons nit and ntf are never allowed to be more than 99. ------------------------------------------