Opened 2 weeks ago

#284 new Support

Strange big bouncing of particles when hitting ground

Reported by: fcheng Owned by:
Priority: major Milestone:
Component: FP other Version: FLEXPART 10.4
Keywords: Cc:


Dear FLEXPART community,

I observe that the particles released by FLEXPART have seemingly overexaggerated bouncing behavior when they are hitting the ground, sometimes they can be reflected by a few km or even up to 10km in just one hour. This really confuses me since it just does not make sense.

I think the source code that controls the bouncing of particles is related to advance.f90, and maybe also the default setting of SPECIES 24. But I just could not really identify where the problem comes from.

For your information, here is my RELEASES file

 NSPEC      =           1, ! Total number of species
 SPECNUM_REL=          24, ! Species numbers in directory SPECIES
&RELEASE                   ! For each release
 IDATE1  =       20080601, ! Release start date, YYYYMMDD: YYYY=year, MM=month, DD=day
 ITIME1  =          00000, ! Release start time in UTC HHMISS: HH hours, MI=minutes, SS=seconds
 IDATE2  =       20080601, ! Release end date, same as IDATE1
 ITIME2  =          00000, ! Release end time, same as ITIME1
 LON1    =       -179.000, ! Left longitude of release box -180 < LON1 <180
 LON2    =        179.000, ! Right longitude of release box, same as LON1
 LAT1    =        -89.000, ! Lower latitude of release box, -90 < LAT1 < 90
 LAT2    =         89.000, ! Upper latitude of release box same format as LAT1
 Z1      =          0.000, ! Lower height of release box meters/hPa above reference level
 Z2      =       5000.000, ! Upper height of release box meters/hPa above reference level
 ZKIND   =              1, ! Reference level 1=above ground, 2=above sea level, 3 for pressure in hPa
 MASS    =       1.0000E0, ! Total mass emitted, only relevant for fwd simulations
 PARTS   =        6000000, ! Total number of particles to be released
 COMMENT =    "RELEASE 1 test, particles released in an hour.", ! Comment, written in the outputfile


 LDIRECT=               1, ! Simulation direction in time   ; 1 (forward) or -1 (backward)
 IBDATE=         20080601, ! Start date of the simulation   ; YYYYMMDD: YYYY=year, MM=month, DD=day
 IBTIME=            00000, ! Start time of the simulation   ; HHMISS: HH=hours, MI=min, SS=sec; UTC
 IEDATE=         20080601, ! End date of the simulation     ; same format as IBDATE
 IETIME=           210000, ! End  time of the simulation    ; same format as IBTIME
 LOUTSTEP=           3600, ! Interval of model output; average concentrations calculated every LOUTSTEP (s)
 LOUTAVER=           3600, ! Interval of output averaging (s)
 LOUTSAMPLE=          900, ! Interval of output sampling  (s), higher stat. accuracy with shorter intervals
 ITSPLIT=        99999999, ! Interval of particle splitting (s)
 LSYNCTIME=           900, ! All processes are synchronized to this time interval (s)
 CTL=          -5.0000000, ! CTL>1, ABL time step = (Lagrangian timescale (TL))/CTL, uses LSYNCTIME if CTL<0
 IFINE=                 4, ! Reduction for time step in vertical transport, used only if CTL>1
 IOUT=                  1, ! Output type: [1]mass 2]pptv 3]1&2 4]plume 5]1&4, +8 for NetCDF output
 IPOUT=                 1, ! Particle position output: 0]no 1]every output 2]only at end 3]time averaged
 LSUBGRID=              0, ! Increase of ABL heights due to sub-grid scale orographic variations;[0]off 1]on
 LCONVECTION=           1, ! Switch for convection parameterization;0]off [1]on
 LAGESPECTRA=           0, ! Switch for calculation of age spectra (needs AGECLASSES);[0]off 1]on
 IPIN=                  0, ! Warm start from particle dump (needs previous partposit_end file); [0]no 1]yes
 IOUTPUTFOREACHRELEASE= 0, ! Separate output fields for each location in the RELEASE file; [0]no 1]yes
 IFLUX=                 0, ! Output of mass fluxes through output grid box boundaries
 MDOMAINFILL=           1, ! Switch for domain-filling, if limited-area particles generated at boundary
 IND_SOURCE=            1, ! Unit to be used at the source   ;  [1]mass 2]mass mixing ratio
 IND_RECEPTOR=          1, ! Unit to be used at the receptor; [1]mass 2]mass mixing ratio 3]wet depo. 4]dry depo.
 MQUASILAG=             1, ! Quasi-Lagrangian mode to track individual numbered particles
 NESTED_OUTPUT=         0, ! Output also for a nested domain
 LINIT_COND=            0, ! Output sensitivity to initial conditions (bkw mode only) [0]off 1]conc 2]mmr
 SURF_ONLY=             0, ! Output only for the lowest model layer, used w/ LINIT_COND=1 or 2
 CBLFLAG=               0, ! Skewed, not Gaussian turbulence in the convective ABL, need large CTL and IFINE
 OHFIELDS_PATH= "../../flexin/", ! Default path for OH file

And, here is the hourly altitude (meters a.g.l.) of a particle that had a big bounce (and there are many particles with such a behavior)


Is such a big bouncing behavior normal? Any hints and help are much appreciated. Thanks a lot!

Warm regards,

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