diff --git a/A-INSTALL b/A-INSTALL
index a85c1f96f701ce78a3f7b88147e605ccd536bb48..14ef158756ed91d741f6384f049c749be1b371b5 100644
--- a/A-INSTALL
+++ b/A-INSTALL
@@ -1,7 +1,7 @@
 #
 # Version of PACKAGE MESONH "Open distribution"
 #              PACK-MNH-V5-6-1
-#              DATE : 05/09/2023
+#              DATE : 25/09/2023
 #              VERSION : MESONH MASDEV5_6 + BUG-1
 #
 #  MAP
diff --git a/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90 b/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90
index 3f5860da56c6be4bf8b67fbd5b0dd7409779490c..9559f6b17ca0dcaa3816b5dcb764b2db48b8a678 100644
--- a/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90
+++ b/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90
@@ -2301,7 +2301,9 @@ subroutine Write_flyer_time_coord( tpflyer )
   type(tdimnc),        pointer :: tzdim
 
   !Do it only if correct model level and has really flown
-  if ( tpflyer%nmodel == imi .and. Count( tpflyer%xx /= XUNDEF) > 1 ) then
+  if ( tpflyer%nmodel == imi ) then
+  ! Do the second if only if the first one is OK (if not, xx may be not allocated)
+  if ( Count( tpflyer%xx /= XUNDEF) > 1 ) then
     Allocate( tzdim )
 
     istatus = NF90_INQ_NCID( tpfile%nncid, 'Flyers', icatid )
@@ -2342,6 +2344,7 @@ subroutine Write_flyer_time_coord( tpflyer )
     !Restore file identifier to root group
     incid = tpfile%nncid
   end if
+  end if
 
 end subroutine Write_flyer_time_coord
 
diff --git a/src/MNH/aeroopt_get.f90 b/src/MNH/aeroopt_get.f90
index d8ec58193f7c308daba8bf8ad069ab21f2e7a976..994608c3da4bbb2bcab4f8ad5382131f9e67adc8 100644
--- a/src/MNH/aeroopt_get.f90
+++ b/src/MNH/aeroopt_get.f90
@@ -132,8 +132,9 @@
   REAL, DIMENSION(size(ZMASS,1),size(ZMASS,2),size(ZMASS,3))      :: VEXTR
   COMPLEX, DIMENSION(size(ZMASS,1),size(ZMASS,2),size(ZMASS,3),6)::Req !  Equivalent refractive index
   REAL, PARAMETER           :: EPSILON=1.d-8                     ![um] a small number used to avoid zero
-  
-  INTEGER ::JJJ, JI, JSV
+  REAL,DIMENSION(NSP+NCARB+NSOA)       :: ZFAC
+  REAL,DIMENSION(NSP+NCARB+NSOA)       :: ZRHOI  
+  INTEGER ::JJJ, JI, JSV, JJ
  
 !-------------------------------------------------------------------------
 !-------------------------------------------------------------------------
@@ -212,25 +213,33 @@ NMODE_AER=JPMODE  ! in case of ORILAM
 !       VDDST(:,:,:)=0.
 !    ENDIF
 
-
-     VOC(:,:,:)=(ZMASS(:,:,:,JP_AER_OC,JMDE))/XFAC(JP_AER_OC)
-     VH2O(:,:,:)=(ZMASS(:,:,:,JP_AER_H2O,JMDE))/XFAC(JP_AER_H2O)
-     VAM(:,:,:)=(ZMASS(:,:,:,JP_AER_NH3,JMDE))/XFAC(JP_AER_NH3)
-     VSU(:,:,:)=(ZMASS(:,:,:,JP_AER_SO4,JMDE))/XFAC(JP_AER_SO4)
-     VNI(:,:,:)=(ZMASS(:,:,:,JP_AER_NO3,JMDE))/XFAC(JP_AER_NO3)
-     VBC(:,:,:)=(ZMASS(:,:,:,JP_AER_BC,JMDE))/XFAC(JP_AER_BC)
-     VDDST(:,:,:)=(ZMASS(:,:,:,JP_AER_DST,JMDE))/XFAC(JP_AER_DST)
+! Cf Ackermann (all to black carbon except water)
+!Set molecular weightn g/mol 
+ZRHOI(:) = 1.8e3
+ZRHOI(JP_AER_H2O) = 1.0e3   ! water
+ZRHOI(JP_AER_DST) = XDENSITY_DUST  ! dusts
+DO JJ=1,NSP+NCARB+NSOA
+  ZFAC(JJ)=(4./3.)*XPI*ZRHOI(JJ)*1.e-9
+ENDDO
+
+     VOC(:,:,:)=(ZMASS(:,:,:,JP_AER_OC,JMDE))/ZFAC(JP_AER_OC)
+     VH2O(:,:,:)=(ZMASS(:,:,:,JP_AER_H2O,JMDE))/ZFAC(JP_AER_H2O)
+     VAM(:,:,:)=(ZMASS(:,:,:,JP_AER_NH3,JMDE))/ZFAC(JP_AER_NH3)
+     VSU(:,:,:)=(ZMASS(:,:,:,JP_AER_SO4,JMDE))/ZFAC(JP_AER_SO4)
+     VNI(:,:,:)=(ZMASS(:,:,:,JP_AER_NO3,JMDE))/ZFAC(JP_AER_NO3)
+     VBC(:,:,:)=(ZMASS(:,:,:,JP_AER_BC,JMDE))/ZFAC(JP_AER_BC)
+     VDDST(:,:,:)=(ZMASS(:,:,:,JP_AER_DST,JMDE))/ZFAC(JP_AER_DST)
     IF (NSOA .EQ. 10) THEN 
-     VSOA1(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA1,JMDE))/XFAC(JP_AER_SOA1)
-     VSOA2(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA2,JMDE))/XFAC(JP_AER_SOA2)
-     VSOA3(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA3,JMDE))/XFAC(JP_AER_SOA3)
-     VSOA4(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA4,JMDE))/XFAC(JP_AER_SOA4)
-     VSOA5(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA5,JMDE))/XFAC(JP_AER_SOA5)
-     VSOA6(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA6,JMDE))/XFAC(JP_AER_SOA6)
-     VSOA7(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA7,JMDE))/XFAC(JP_AER_SOA7)
-     VSOA8(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA8,JMDE))/XFAC(JP_AER_SOA8)
-     VSOA9(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA9,JMDE))/XFAC(JP_AER_SOA9)
-     VSOA10(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA10,JMDE))/XFAC(JP_AER_SOA10)
+     VSOA1(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA1,JMDE))/ZFAC(JP_AER_SOA1)
+     VSOA2(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA2,JMDE))/ZFAC(JP_AER_SOA2)
+     VSOA3(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA3,JMDE))/ZFAC(JP_AER_SOA3)
+     VSOA4(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA4,JMDE))/ZFAC(JP_AER_SOA4)
+     VSOA5(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA5,JMDE))/ZFAC(JP_AER_SOA5)
+     VSOA6(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA6,JMDE))/ZFAC(JP_AER_SOA6)
+     VSOA7(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA7,JMDE))/ZFAC(JP_AER_SOA7)
+     VSOA8(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA8,JMDE))/ZFAC(JP_AER_SOA8)
+     VSOA9(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA9,JMDE))/ZFAC(JP_AER_SOA9)
+     VSOA10(:,:,:)=(ZMASS(:,:,:,JP_AER_SOA10,JMDE))/ZFAC(JP_AER_SOA10)
      VSOA(:,:,:)=VSOA1(:,:,:)+VSOA2(:,:,:)+VSOA3(:,:,:)+VSOA4(:,:,:)+&
                  VSOA5(:,:,:)+VSOA6(:,:,:)+VSOA7(:,:,:)+VSOA8(:,:,:)+&
                  VSOA9(:,:,:)+VSOA10(:,:,:)
diff --git a/src/MNH/aircraft_balloon_evol.f90 b/src/MNH/aircraft_balloon_evol.f90
index e37f97c5b71fa08247d3449f6c8c8923c4296cdf..dcbdd6349d012cb4ceea2734c75146d1c55a5c4b 100644
--- a/src/MNH/aircraft_balloon_evol.f90
+++ b/src/MNH/aircraft_balloon_evol.f90
@@ -31,6 +31,8 @@
 MODULE MODE_AIRCRAFT_BALLOON_EVOL
 !      ##########################
 
+USE MODD_PRECISION, ONLY: MNHREAL
+
 USE MODE_MSG
 
 IMPLICIT NONE
@@ -43,6 +45,8 @@ PUBLIC :: AIRCRAFT_COMPUTE_POSITION
 
 PUBLIC :: FLYER_GET_RANK_MODEL_ISCRASHED
 
+REAL, PARAMETER :: XTIMETHRESH = 1.E-8_MNHREAL
+
 CONTAINS
 !     ########################################################
       SUBROUTINE AIRCRAFT_BALLOON_EVOL(PTSTEP,               &
@@ -299,7 +303,7 @@ SELECT TYPE ( TPFLYER )
     ! Launch?
     LAUNCH: IF ( .NOT. TPFLYER%LFLY .AND. .NOT. TPFLYER%LCRASH .AND. TPFLYER%NMODEL == IMI ) THEN
       ! Check if it is launchtime
-      LAUNCHTIME: IF ( ( TDTCUR - TPFLYER%TLAUNCH ) >= -1.e-10 ) THEN
+      LAUNCHTIME: IF ( ( TDTCUR - TPFLYER%TLAUNCH ) >= -XTIMETHRESH ) THEN
         TPFLYER%LFLY = .TRUE.
         GLAUNCH = .TRUE.
 
@@ -315,15 +319,16 @@ SELECT TYPE ( TPFLYER )
     ! Check if it is time to store data. This has also to be checked if the balloon
     ! is not yet launched or is crashed (data is also written in these cases, but with default values)
     IF ( TPFLYER%NMODEL == IMI .AND. &
-          ( .NOT. TPFLYER%LFLY .OR. TPFLYER%LCRASH .OR. ABS( TPFLYER%TPOS_CUR - TDTCUR ) < 1.e-8 ) ) THEN
+          ( .NOT. TPFLYER%LFLY .OR. TPFLYER%LCRASH .OR. ABS( TPFLYER%TPOS_CUR - TDTCUR ) < XTIMETHRESH ) ) THEN
       !Do we have to store balloon data?
       TPFLYER%LSTORE = TPFLYER%TFLYER_TIME%STORESTEP_CHECK_AND_SET( ISTORE )
       IF ( TPFLYER%LSTORE ) TPFLYER%NSTORE_CUR = ISTORE
     END IF
 
     ! In flight
+    ! The condition "ABS( TPFLYER%TPOS_CUR - TDTCUR ) < XTIMETHRESH" is necessary if the balloon changes of model
     INFLIGHTONMODEL: IF ( TPFLYER%LFLY .AND. .NOT. TPFLYER%LCRASH .AND. TPFLYER%NMODEL == IMI &
-                          .AND. ABS( TPFLYER%TPOS_CUR - TDTCUR ) < 1.e-8 ) THEN
+                          .AND. ABS( TPFLYER%TPOS_CUR - TDTCUR ) < XTIMETHRESH ) THEN
       ISOWNERBAL: IF ( TPFLYER%NRANK_CUR == ISP ) THEN
         CALL FLYER_INTERP_TO_MASSPOINTS()
 
diff --git a/src/MNH/ini_aircraft.f90 b/src/MNH/ini_aircraft.f90
index 40be297467af3fdff58183479da32c89a667975a..64e39beb3c82047dd42ed9f19ccd5d9c94f2a434 100644
--- a/src/MNH/ini_aircraft.f90
+++ b/src/MNH/ini_aircraft.f90
@@ -54,6 +54,8 @@ DO JI = 1, NAIRCRAFTS
 
     TZAIRCRAFT%NID = JI
 
+    TZAIRCRAFT%LFIX = .FALSE.
+
   IF ( CTITLE(JI) == '' ) THEN
     WRITE( CTITLE(JI), FMT = '( A, I3.3) ') TRIM( CTYPE(JI) ), JI
 
diff --git a/src/MNH/ini_aircraft_balloon.f90 b/src/MNH/ini_aircraft_balloon.f90
index 7dc6567036e01f7619912a665cd1b99b452486e7..f31a5584a3f4d9018367801a666ac2644e9098a0 100644
--- a/src/MNH/ini_aircraft_balloon.f90
+++ b/src/MNH/ini_aircraft_balloon.f90
@@ -67,10 +67,11 @@ CONTAINS
 !          ------------
 !
 USE MODD_AIRCRAFT_BALLOON
-USE MODD_CONF,       ONLY: CPROGRAM
+USE MODD_CONF,       ONLY: CPROGRAM, NMODEL
 USE MODD_DYN_n,      ONLY: DYN_MODEL
 USE MODD_IO,         ONLY: ISP, TFILEDATA
 USE MODD_PARAMETERS, ONLY: NUNDEF
+USE MODD_PARAM_n,    ONLY: PARAM_MODEL
 !
 USE MODE_GRIDPROJ,       ONLY: SM_XYHAT
 USE MODE_INI_AIRCRAFT,   ONLY: INI_AIRCRAFT
@@ -92,6 +93,7 @@ REAL,               INTENT(IN) :: PLONOR  ! longitude of origine point
 !
 INTEGER :: IMI    ! current model index
 INTEGER :: JI
+LOGICAL :: GCHECK
 !
 !----------------------------------------------------------------------------
 
@@ -99,12 +101,12 @@ IF ( CPROGRAM == 'DIAG  ') RETURN
 
 IF ( NAIRCRAFTS > 0 .OR. NBALLOONS > 0 ) LFLYER = .TRUE.
 
+IMI = GET_CURRENT_MODEL_INDEX()
+
 !----------------------------------------------------------------------------
 !
 !*      2.   Balloon initialization
 !            ----------------------
-IMI=GET_CURRENT_MODEL_INDEX()
-
 IF ( IMI == 1 ) THEN
   ALLOCATE( NRANKCUR_BALLOON (NBALLOONS) ); NRANKCUR_BALLOON = NFLYER_DEFAULT_RANK
   ALLOCATE( NRANKNXT_BALLOON (NBALLOONS) ); NRANKNXT_BALLOON = NFLYER_DEFAULT_RANK
@@ -147,13 +149,50 @@ END IF
 !*      4.   Allocations of storage arrays
 !            -----------------------------
 !
-IF ( IMI == 1 .AND. ISP == NFLYER_DEFAULT_RANK ) THEN
+! Check that CCLOUD, CRAD and CTURB are the same for all models if some flyers have CMODEL='MOB'
+! This is necessary because we need to allocate and compute the same data on every model if the flyer is allowed to change model
+! This check is only done once (on MODEL IMI=1)
+! This check has to be done AFTER the calls to INI_AIRCRAFT and INI_BALLOON
+IF ( IMI == 1 .AND. NMODEL > 1 .AND. ISP == NFLYER_DEFAULT_RANK ) THEN
+  GCHECK = .FALSE.
+
+  DO JI = 1, NBALLOONS
+    IF ( TBALLOONS(JI)%TBALLOON%CMODEL == 'MOB' ) THEN
+      GCHECK = .TRUE.
+      EXIT
+    END IF
+  END DO
+
+  DO JI = 1, NAIRCRAFTS
+    IF ( TAIRCRAFTS(JI)%TAIRCRAFT%CMODEL == 'MOB' ) THEN
+      GCHECK = .TRUE.
+      EXIT
+    END IF
+  END DO
+
+  IF ( GCHECK ) THEN
+    DO JI = 2, NMODEL
+      IF ( PARAM_MODEL(JI)%CCLOUD /= PARAM_MODEL(1)%CCLOUD )        &
+        CALL PRINT_MSG( NVERB_ERROR, 'GEN', 'INI_AIRCRAFT_BALLOON', &
+                       'CCLOUD must be the same on all nested domains if aircraft/balloon has CMODEL="MOB"' )
+      IF ( PARAM_MODEL(JI)%CRAD   /= PARAM_MODEL(1)%CRAD )          &
+        CALL PRINT_MSG( NVERB_ERROR, 'GEN', 'INI_AIRCRAFT_BALLOON', &
+                       'CRAD must be the same on all nested domains if aircraft/balloon has CMODEL="MOB"' )
+      IF ( PARAM_MODEL(JI)%CTURB  /= PARAM_MODEL(1)%CTURB )         &
+        CALL PRINT_MSG( NVERB_ERROR, 'GEN', 'INI_AIRCRAFT_BALLOON', &
+                       'CTURB must be the same on all nested domains if aircraft/balloon has CMODEL="MOB"' )
+    END DO
+  END IF
+END IF
+
+! Allocate data arrays of flyers
+IF ( ISP == NFLYER_DEFAULT_RANK ) THEN
   DO JI = 1, NBALLOONS
-    CALL TBALLOONS(JI)%TBALLOON%DATA_ARRAYS_ALLOCATE()
+    IF ( TBALLOONS(JI)%TBALLOON%NMODEL == IMI ) CALL TBALLOONS(JI)%TBALLOON%DATA_ARRAYS_ALLOCATE()
   END DO
 
   DO JI = 1, NAIRCRAFTS
-    CALL TAIRCRAFTS(JI)%TAIRCRAFT%DATA_ARRAYS_ALLOCATE()
+    IF ( TAIRCRAFTS(JI)%TAIRCRAFT%NMODEL == IMI ) CALL TAIRCRAFTS(JI)%TAIRCRAFT%DATA_ARRAYS_ALLOCATE()
   END DO
 END IF
 !
@@ -208,6 +247,7 @@ CALL SM_XYHAT( PLATOR, PLONOR, TPFLYER%XLATLAUNCH, TPFLYER%XLONLAUNCH, TPFLYER%X
 
 IF ( CPROGRAM == 'MESONH' .OR. CPROGRAM == 'SPAWN ' .OR. CPROGRAM == 'REAL  ' ) THEN
   ! Read the current location in the synchronous file
+  ! Remark: if the balloon is not yet in flight or is crashed, position is not available in file
 
   IF ( TPINIFILE%CFORMAT == 'LFI'                                                             &
        .OR. ( TPINIFILE%CFORMAT == 'NETCDF4' .AND.                                            &
diff --git a/src/MNH/ini_balloon.f90 b/src/MNH/ini_balloon.f90
index bbcaa9abad8b08aa5af220fc8fc9cc6055de02b5..e3ca63c57f4548453f78fef314f1cf78e9f11ed2 100644
--- a/src/MNH/ini_balloon.f90
+++ b/src/MNH/ini_balloon.f90
@@ -48,6 +48,8 @@ DO JI = 1, NBALLOONS
 
   TZBALLOON%NID = JI
 
+  TZBALLOON%LFIX = .FALSE.
+
   IF ( CTITLE(JI) == '' ) THEN
     WRITE( CTITLE(JI), FMT = '( A, I3.3) ') TRIM( CTYPE(JI) ), JI
 
diff --git a/src/MNH/ini_posprofilern.f90 b/src/MNH/ini_posprofilern.f90
index 4ce19c1558c9b1b90c8c30c16ab0631bd4037214..6a50b045d044f43e3a1ae420c44edadfc66d488c 100644
--- a/src/MNH/ini_posprofilern.f90
+++ b/src/MNH/ini_posprofilern.f90
@@ -141,6 +141,7 @@ END IF
 LPROFILER = ( INUMBPROF > 0 )
 
 DO JI = 1, NUMBPROFILER_LOC
+  TPROFILERS(JI)%LFIX = .TRUE.
   CALL TPROFILERS(JI)%DATA_ARRAYS_ALLOCATE( ISTORE )
 END DO
 !----------------------------------------------------------------------------
diff --git a/src/MNH/ini_surfstationn.f90 b/src/MNH/ini_surfstationn.f90
index c1eb1a20dab4975e5cb9021e1154403505ed7996..a14cc771c37a1852a1ff9cd1991400cfb71795d7 100644
--- a/src/MNH/ini_surfstationn.f90
+++ b/src/MNH/ini_surfstationn.f90
@@ -142,6 +142,7 @@ END IF
 LSTATION = ( INUMBSTAT > 0 )
 
 DO JI = 1, NUMBSTAT_LOC
+  TSTATIONS(JI)%LFIX = .TRUE.
   CALL TSTATIONS(JI)%DATA_ARRAYS_ALLOCATE( ISTORE )
 END DO
 
diff --git a/src/MNH/modd_sensor.f90 b/src/MNH/modd_sensor.f90
index 18ca64c27d6941aaa3a87a398614b0900f1867ae..b780c39137fc86ee7ed5d63c5a9af8921b9b8c04 100644
--- a/src/MNH/modd_sensor.f90
+++ b/src/MNH/modd_sensor.f90
@@ -21,6 +21,8 @@ MODULE MODD_SENSOR
 
   INTEGER, PARAMETER :: NTAG_NCUR = 145
   INTEGER, PARAMETER :: NTAG_PACK = 245
+
+  INTEGER, PARAMETER :: NEMPTYDATA = -1 ! Size to communicate if exchange of no sensor data
   TYPE :: TSENSORTIME
       INTEGER                                    :: N_CUR   = 0       ! current step of storage
       REAL                                       :: XTSTEP  = 60.     ! storage time step (default reset later)
@@ -71,6 +73,7 @@ MODULE MODD_SENSOR
       INTEGER :: NV01 = NNEGUNDEF ! Z position for ni_m  , nj_v+1
       INTEGER :: NV10 = NNEGUNDEF ! Z position for ni_m+1, nj_v
       INTEGER :: NV11 = NNEGUNDEF ! Z position for ni_m+1, nj_v+1
+
       ! Coefficient to interpolate values (sensors are usually not exactly on mesh points)
       REAL :: XXMCOEF = XUNDEF ! Interpolation coefficient for X (mass-point)
       REAL :: XYMCOEF = XUNDEF ! Interpolation coefficient for Y (mass-point)
@@ -380,7 +383,6 @@ MODULE MODD_SENSOR
       INTEGER :: IK00, IK01, IK10, IK11
       INTEGER :: IKB, IKE, IKU
       INTEGER :: JI, JJ
-      LOGICAL :: GCHANGE ! set to true if at least an index has been forced to change
       LOGICAL :: GDONE   ! set to true if coefficient computation has been done
       LOGICAL :: GDONOLOWCRASH
       REAL    :: ZZCOEF00, ZZCOEF01, ZZCOEF10, ZZCOEF11
@@ -388,7 +390,6 @@ MODULE MODD_SENSOR
       OLOW  = .FALSE.
       OHIGH = .FALSE.
 
-      GCHANGE = .FALSE.
       GDONE   = .FALSE.
 
       IKB = 1 + JPVEXT
@@ -419,9 +420,9 @@ MODULE MODD_SENSOR
       IF ( ANY( [ IK00, IK01, IK10, IK11 ] < IKB ) ) THEN
           ! Sensor is low (too near the ground or below it)
         OLOW = .TRUE.
+
         IF ( GDONOLOWCRASH ) THEN
           ! Do not allow crash on the ground: set position on the ground if too low
-          GCHANGE = .TRUE.
           !Minimum altitude is on the ground at ikb (no crash if too low)
           IK00 = MAX ( IK00, IKB )
           IK01 = MAX ( IK01, IKB )
@@ -454,25 +455,20 @@ MODULE MODD_SENSOR
         OHIGH = .TRUE.
 
         ! Limit ik?? indices to prevent out of bound accesses
-        IF ( IK00 > IKU-1) THEN
-          IK00 = IKU-1
-          GCHANGE = .TRUE.
-        END IF
-        IF ( IK01 > IKU-1) THEN
-          IK01 = IKU-1
-          GCHANGE = .TRUE.
-        END IF
-        IF ( IK10 > IKU-1) THEN
-          IK10 = IKU-1
-          GCHANGE = .TRUE.
-        END IF
-        IF ( IK11 > IKU-1) THEN
-          IK11 = IKU-1
-          GCHANGE = .TRUE.
-        END IF
+        IK00 = MIN( IK00, IKE )
+        IK01 = MIN( IK01, IKE )
+        IK10 = MIN( IK10, IKE )
+        IK11 = MIN( IK11, IKE )
 
         CALL PRINT_MSG( NVERB_WARNING, 'GEN', 'Compute_vertical_interp_coeff', &
                         'sensor ' // TRIM( TPSENSOR%CNAME ) // ' is too high', OLOCAL = .TRUE. )
+
+        ZZCOEF00 = XUNDEF
+        ZZCOEF01 = XUNDEF
+        ZZCOEF10 = XUNDEF
+        ZZCOEF11 = XUNDEF
+
+        GDONE = .TRUE.
       END IF
 
       IF ( .NOT. GDONE ) THEN
@@ -1258,9 +1254,9 @@ MODULE MODD_SENSOR
 
     END SUBROUTINE BUFFER_RECV
 
-    ! ##################################################################
-    SUBROUTINE SENSOR_COMM_SEND( TPSENSOR, KTO, OSEND_SIZE_TO_RECEIVER )
-    ! ##################################################################
+    ! ##############################################################################
+    SUBROUTINE SENSOR_COMM_SEND( TPSENSOR, KTO, OSEND_SIZE_TO_RECEIVER, OEMPTYSEND )
+    ! ##############################################################################
 
       USE MODD_IO, ONLY: ISP
 
@@ -1269,10 +1265,12 @@ MODULE MODD_SENSOR
       CLASS(TSENSOR),           INTENT(INOUT) :: TPSENSOR
       INTEGER,                  INTENT(IN)    :: KTO                    ! Process to which to send data
       LOGICAL,        OPTIONAL, INTENT(IN)    :: OSEND_SIZE_TO_RECEIVER ! If the buffer size has to be send to the receiver
+      LOGICAL,        OPTIONAL, INTENT(IN)    :: OEMPTYSEND             ! True if the sensor data has not to be sent
 
       CHARACTER(LEN=10) :: YFROM, YTO
       INTEGER           :: IPACKSIZE
       INTEGER           :: IPOS
+      LOGICAL           :: GEMPTYSEND
       LOGICAL           :: GSEND_SIZE_TO_RECEIVER
       REAL,    DIMENSION(:), ALLOCATABLE :: ZPACK ! buffer to store raw data of the sensor
 
@@ -1281,27 +1279,45 @@ MODULE MODD_SENSOR
       CALL PRINT_MSG( NVERB_DEBUG, 'GEN', 'Sensor_comm_send', &
                       'send sensor ' // TRIM(TPSENSOR%CNAME) // ': ' // TRIM(YFROM) // '->' // TRIM(YTO), OLOCAL = .TRUE. )
 
+      IF ( PRESENT( OEMPTYSEND ) ) THEN
+        GEMPTYSEND = OEMPTYSEND
+      ELSE
+        GEMPTYSEND = .FALSE.
+      END IF
+
       IF ( PRESENT( OSEND_SIZE_TO_RECEIVER ) ) THEN
         GSEND_SIZE_TO_RECEIVER = OSEND_SIZE_TO_RECEIVER
       ELSE
         GSEND_SIZE_TO_RECEIVER = .FALSE.
       END IF
 
-      IPACKSIZE = TPSENSOR%BUFFER_SIZE_COMPUTE( TPSENSOR%NSTORE_CUR )
+      IF ( GEMPTYSEND .AND. .NOT.GSEND_SIZE_TO_RECEIVER )                                                  &
+        CALL PRINT_MSG( NVERB_ERROR, 'GEN', 'Sensor_comm_send',                                            &
+                        'incompatible options: gemptysend=T and gsend_size_to_receiver=F', OLOCAL = .TRUE. )
+
+      IF ( GEMPTYSEND ) THEN
+        ! If 'empty send', ipacksize is set to NEMPTYDATA
+        ! This will allow the receiver to know that no sensor data will be sent
+        IPACKSIZE = NEMPTYDATA
+      ELSE
+        IPACKSIZE = TPSENSOR%BUFFER_SIZE_COMPUTE( TPSENSOR%NSTORE_CUR )
+      END IF
 
       IF ( GSEND_SIZE_TO_RECEIVER ) CALL TPSENSOR%BUFFER_SIZE_SEND( TPSENSOR%NSTORE_CUR, IPACKSIZE, KTO )
 
-      ALLOCATE( ZPACK(IPACKSIZE) )
+      IF ( .NOT. GEMPTYSEND ) THEN
+        ALLOCATE( ZPACK(IPACKSIZE) )
 
-      IPOS = 1
-      CALL TPSENSOR%BUFFER_PACK( ZPACK, IPOS, TPSENSOR%NSTORE_CUR )
+        IPOS = 1
+        CALL TPSENSOR%BUFFER_PACK( ZPACK, IPOS, TPSENSOR%NSTORE_CUR )
 
-      IF ( IPOS-1 /= IPACKSIZE ) &
-        CALL PRINT_MSG( NVERB_ERROR, 'GEN', 'Sensor_comm_send', 'IPOS-1 /= IPACKSIZE', OLOCAL = .TRUE. )
+        IF ( IPOS-1 /= IPACKSIZE ) &
+          CALL PRINT_MSG( NVERB_ERROR, 'GEN', 'Sensor_comm_send', 'IPOS-1 /= IPACKSIZE', OLOCAL = .TRUE. )
 
-      CALL TPSENSOR%BUFFER_SEND( ZPACK, KTO )
+        CALL TPSENSOR%BUFFER_SEND( ZPACK, KTO )
 
-      DEALLOCATE( ZPACK )
+        DEALLOCATE( ZPACK )
+      END IF
 
     END SUBROUTINE SENSOR_COMM_SEND
 
@@ -1320,26 +1336,28 @@ MODULE MODD_SENSOR
 
     END SUBROUTINE SENSOR_COMM_SEND_DEALLOCATE
 
-    ! ####################################################################################################
-    SUBROUTINE SENSOR_COMM_RECV_ALLOCATE( TPSENSOR, KFROM, KSTORE_CUR, KSTORE_MAX, ORECV_SIZE_FROM_OWNER )
-    ! ####################################################################################################
+    ! ################################################################################################################
+    SUBROUTINE SENSOR_COMM_RECV_ALLOCATE( TPSENSOR, KFROM, KSTORE_CUR, KSTORE_MAX, ORECV_SIZE_FROM_OWNER, OEMPTYRECV )
+    ! ################################################################################################################
 
       USE MODD_IO, ONLY: ISP
 
       USE MODE_MSG
 
       CLASS(TSENSOR),           INTENT(INOUT) :: TPSENSOR
-      INTEGER,                  INTENT(IN)    :: KFROM    ! Process from which to receive data
+      INTEGER,                  INTENT(IN)    :: KFROM      ! Process from which to receive data
       INTEGER,        OPTIONAL, INTENT(IN)    :: KSTORE_CUR ! Number of storage steps to receive
       INTEGER,        OPTIONAL, INTENT(IN)    :: KSTORE_MAX ! Maximum number of storage steps to store in sensor
                                                             ! (if not provided, kstore_* size must be given by the sender)
       LOGICAL,        OPTIONAL, INTENT(IN)    :: ORECV_SIZE_FROM_OWNER ! If the buffer size has to be send to the receiver
+      LOGICAL,        OPTIONAL, INTENT(OUT)   :: OEMPTYRECV ! True if the sensor data has not been received
 
       CHARACTER(LEN=10) :: YFROM, YTO
       INTEGER           :: IPACKSIZE
       INTEGER           :: IPOS
       INTEGER           :: ISTORE_CUR
       INTEGER           :: ISTORE_MAX
+      LOGICAL           :: GEMPTYRECV
       LOGICAL           :: GRECV_SIZE_FROM_OWNER
       REAL,    DIMENSION(:), ALLOCATABLE :: ZPACK ! buffer to store raw data of the sensor
 
@@ -1348,6 +1366,8 @@ MODULE MODD_SENSOR
       CALL PRINT_MSG( NVERB_DEBUG, 'GEN', 'Sensor_comm_recv_allocate', &
                       'receive sensor (name not yet known): ' // TRIM(YFROM) // '->' // TRIM(YTO), OLOCAL = .TRUE. )
 
+      GEMPTYRECV = .FALSE.
+
       IF ( PRESENT( ORECV_SIZE_FROM_OWNER ) ) THEN
         GRECV_SIZE_FROM_OWNER = ORECV_SIZE_FROM_OWNER
       ELSE
@@ -1387,19 +1407,29 @@ MODULE MODD_SENSOR
         IPACKSIZE = TPSENSOR%BUFFER_SIZE_COMPUTE( ISTORE_CUR )
       END IF
 
-      ! Allocate receive buffer
-      ALLOCATE( ZPACK(IPACKSIZE) )
+      IF ( IPACKSIZE == NEMPTYDATA ) THEN
+        GEMPTYRECV = .TRUE.
+        !call Print_msg( NVERB_DEBUG, 'GEN', 'Sensor_comm_recv_allocate', 'empty receive', olocal = .true. )
+        IF ( .NOT. PRESENT( OEMPTYRECV) )                                                                                       &
+          CALL PRINT_MSG( NVERB_ERROR, 'GEN', 'Sensor_comm_recv_allocate',                                                      &
+                          'optional dummy argument oemptyrecv must be provided in case of empty communication', OLOCAL = .TRUE. )
+      ELSE
+        ! Allocate receive buffer
+        ALLOCATE( ZPACK(IPACKSIZE) )
 
-      ! Allocation of sensor must be done only once the total number of stores is known (and only if not yet allocated)
-      IF (TPSENSOR%NSTORE_MAX < 0 ) CALL TPSENSOR%DATA_ARRAYS_ALLOCATE( ISTORE_MAX )
+        ! Allocation of sensor must be done only once the total number of stores is known (and only if not yet allocated)
+        IF (TPSENSOR%NSTORE_MAX < 0 ) CALL TPSENSOR%DATA_ARRAYS_ALLOCATE( ISTORE_MAX )
 
-      CALL TPSENSOR%BUFFER_RECV( ZPACK, KFROM )
+        CALL TPSENSOR%BUFFER_RECV( ZPACK, KFROM )
 
-      IPOS = 1
-      CALL TPSENSOR%BUFFER_UNPACK( ZPACK, IPOS, ISTORE_CUR )
+        IPOS = 1
+        CALL TPSENSOR%BUFFER_UNPACK( ZPACK, IPOS, ISTORE_CUR )
+
+        IF ( IPOS-1 /= IPACKSIZE ) &
+          CALL PRINT_MSG( NVERB_ERROR, 'GEN', 'Sensor_comm_recv_allocate', 'IPOS-1 /= IPACKSIZE', OLOCAL = .TRUE. )
+      END IF
 
-      IF ( IPOS-1 /= IPACKSIZE ) &
-        CALL PRINT_MSG( NVERB_ERROR, 'GEN', 'Sensor_comm_recv_allocate', 'IPOS-1 /= IPACKSIZE', OLOCAL = .TRUE. )
+      IF ( PRESENT( OEMPTYRECV) ) OEMPTYRECV = GEMPTYRECV
 
     END SUBROUTINE SENSOR_COMM_RECV_ALLOCATE
 
diff --git a/src/MNH/mode_sensor.f90 b/src/MNH/mode_sensor.f90
index bd6c86b3b6ee45c674bba2638188b766f3cd947b..e3ff8bea07f207702737b2803eb8b33bbcb380fa 100644
--- a/src/MNH/mode_sensor.f90
+++ b/src/MNH/mode_sensor.f90
@@ -54,6 +54,7 @@ CONTAINS
     TPSENSOR%XLWCZ(:,KSTORE_ID) = 0.
     TPSENSOR%XIWCZ(:,KSTORE_ID) = 0.
 
+    !TODO: add ICE4?
     IF ( CCLOUD == "LIMA" .OR. CCLOUD=="ICE3" ) THEN
       TPSENSOR%XLWCZ(:,KSTORE_ID) = TPSENSOR%INTERP_HOR_FROM_MASSPOINT( (PR(:,:,:,2)+PR(:,:,:,3)            ) * PRHODREF(:,:,:) )
       TPSENSOR%XIWCZ(:,KSTORE_ID) = TPSENSOR%INTERP_HOR_FROM_MASSPOINT( (PR(:,:,:,4)+PR(:,:,:,5)+PR(:,:,:,6)) * PRHODREF(:,:,:) )
@@ -136,6 +137,7 @@ CONTAINS
     TPSENSOR%XCRARE    (:,KSTORE_ID) = 0.
     TPSENSOR%XCRARE_ATT(:,KSTORE_ID) = 0.
 
+    !TODO: add ICE4?
     IF ( CCLOUD == "LIMA" .OR. CCLOUD=="ICE3" ) THEN
       ZTEMPZ(:)    = TPSENSOR%INTERP_HOR_FROM_MASSPOINT( PTH_EXN(:,:,:)  )
       ZRHODREFZ(:) = TPSENSOR%INTERP_HOR_FROM_MASSPOINT( PRHODREF(:,:,:) )
@@ -519,7 +521,6 @@ CONTAINS
   SUBROUTINE ADD_ORILAM_DATA( TPSENSOR, KLEVEL, KSTORE )
     USE MODD_CH_AEROSOL
     USE MODD_CONF_N,     ONLY: NRR
-    USE MODD_CH_AEROSOL, ONLY: NCARB, NSOA, NSP
     USE MODD_CST,        ONLY: XP00, XCPD, XRD, XRV
     USE MODD_NSV,        ONLY: NSV_AER, NSV_AERBEG, NSV_AEREND
 
diff --git a/src/MNH/write_aircraft_balloon.f90 b/src/MNH/write_aircraft_balloon.f90
index 61be44dab866a3aeb3082d101aaf1cf9608bebd0..a1b978be286734a3a65d09439ffd0d0792e0300c 100644
--- a/src/MNH/write_aircraft_balloon.f90
+++ b/src/MNH/write_aircraft_balloon.f90
@@ -78,7 +78,9 @@ SUBROUTINE WRITE_AIRCRAFT_BALLOON(TPDIAFILE)
 !
 USE MODD_AIRCRAFT_BALLOON
 USE MODD_IO,               ONLY: ISP, TFILEDATA
-!
+
+USE MODE_MODELN_HANDLER,   ONLY: GET_CURRENT_MODEL_INDEX
+
 IMPLICIT NONE
 !
 !
@@ -90,16 +92,21 @@ TYPE(TFILEDATA), INTENT(IN) :: TPDIAFILE ! file to write
 !
 !       0.2  declaration of local variables
 !
+INTEGER :: IMI
 INTEGER :: JI
+LOGICAL :: GEMPTYCOMM ! if TRUE, the communication is empty (no data is exchanged)
 !
 !----------------------------------------------------------------------------
 
+IMI = GET_CURRENT_MODEL_INDEX()
+
 DO JI = 1, NBALLOONS
   ! The balloon data is only available on the process where it is physically located => transfer it if necessary
 
   ! Send data from owner to writer if necessary
   IF ( ISP == NRANKCUR_BALLOON(JI) .AND. NRANKCUR_BALLOON(JI) /= TPDIAFILE%NMASTER_RANK ) THEN
-    CALL TBALLOONS(JI)%TBALLOON%SEND( KTO = TPDIAFILE%NMASTER_RANK, OSEND_SIZE_TO_RECEIVER = .TRUE. )
+    GEMPTYCOMM = ( TBALLOONS(JI)%TBALLOON%NMODEL /= IMI )
+    CALL TBALLOONS(JI)%TBALLOON%SEND( KTO = TPDIAFILE%NMASTER_RANK, OSEND_SIZE_TO_RECEIVER = .TRUE., OEMPTYSEND = GEMPTYCOMM )
   END IF
 
   IF ( ISP == TPDIAFILE%NMASTER_RANK ) THEN
@@ -108,11 +115,12 @@ DO JI = 1, NBALLOONS
       IF ( ASSOCIATED( TBALLOONS(JI)%TBALLOON ) ) &
         call Print_msg( NVERB_FATAL, 'GEN', 'WRITE_AIRCRAFT_BALLOON', 'balloon already associated' )
       ALLOCATE( TBALLOONS(JI)%TBALLOON )
-      CALL TBALLOONS(JI)%TBALLOON%RECV_ALLOCATE( KFROM = NRANKCUR_BALLOON(JI), ORECV_SIZE_FROM_OWNER = .TRUE. )
+      CALL TBALLOONS(JI)%TBALLOON%RECV_ALLOCATE( KFROM = NRANKCUR_BALLOON(JI), ORECV_SIZE_FROM_OWNER = .TRUE., &
+                                                 OEMPTYRECV = GEMPTYCOMM )
     END IF
 
-    ! Write data
-    CALL FLYER_DIACHRO( TPDIAFILE, TBALLOONS(JI)%TBALLOON )
+    ! Write data (if balloon is on this model (GEMPTYCOMM=F))
+    IF ( .NOT. GEMPTYCOMM ) CALL FLYER_DIACHRO( TPDIAFILE, TBALLOONS(JI)%TBALLOON )
 
     ! Remark: release of memory is done later by a call to AIRCRAFT_BALLOON_FREE_NONLOCAL
     !         This call must be done after the file is closed because flyer data is needed on the
@@ -125,7 +133,8 @@ DO JI = 1, NAIRCRAFTS
 
   ! Send data from owner to writer if necessary
   IF ( ISP == NRANKCUR_AIRCRAFT(JI) .AND. NRANKCUR_AIRCRAFT(JI) /= TPDIAFILE%NMASTER_RANK ) THEN
-    CALL TAIRCRAFTS(JI)%TAIRCRAFT%SEND( KTO = TPDIAFILE%NMASTER_RANK, OSEND_SIZE_TO_RECEIVER = .TRUE. )
+    GEMPTYCOMM = ( TAIRCRAFTS(JI)%TAIRCRAFT%NMODEL /= IMI )
+    CALL TAIRCRAFTS(JI)%TAIRCRAFT%SEND( KTO = TPDIAFILE%NMASTER_RANK, OSEND_SIZE_TO_RECEIVER = .TRUE., OEMPTYSEND = GEMPTYCOMM )
   END IF
 
   IF ( ISP == TPDIAFILE%NMASTER_RANK ) THEN
@@ -134,11 +143,12 @@ DO JI = 1, NAIRCRAFTS
       IF ( ASSOCIATED( TAIRCRAFTS(JI)%TAIRCRAFT ) ) &
         call Print_msg( NVERB_FATAL, 'GEN', 'WRITE_AIRCRAFT_BALLOON', 'aircraft already associated' )
       ALLOCATE( TAIRCRAFTS(JI)%TAIRCRAFT )
-      CALL TAIRCRAFTS(JI)%TAIRCRAFT%RECV_ALLOCATE( KFROM = NRANKCUR_AIRCRAFT(JI), ORECV_SIZE_FROM_OWNER = .TRUE. )
+      CALL TAIRCRAFTS(JI)%TAIRCRAFT%RECV_ALLOCATE( KFROM = NRANKCUR_AIRCRAFT(JI), ORECV_SIZE_FROM_OWNER = .TRUE., &
+                                                   OEMPTYRECV = GEMPTYCOMM )
     END IF
 
-    ! Write data
-    CALL FLYER_DIACHRO( TPDIAFILE, TAIRCRAFTS(JI)%TAIRCRAFT )
+    ! Write data (if aircraft is on this model (GEMPTYCOMM=F))
+    IF ( .NOT. GEMPTYCOMM ) CALL FLYER_DIACHRO( TPDIAFILE, TAIRCRAFTS(JI)%TAIRCRAFT )
 
     ! Remark: release of memory is done later by a call to AIRCRAFT_BALLOON_FREE_NONLOCAL
     !         This call must be done after the file is closed because flyer data is needed on the
@@ -168,7 +178,7 @@ IF ( ISP == TPDIAFILE%NMASTER_RANK ) THEN
   DO JI = 1, NBALLOONS
     ! Free ballon data if it was not stored on this process
     IF ( NRANKCUR_BALLOON(JI) /= TPDIAFILE%NMASTER_RANK ) THEN
-      CALL TBALLOONS(JI)%TBALLOON%DATA_ARRAYS_DEALLOCATE()
+      IF ( TBALLOONS(JI)%TBALLOON%NSTORE_MAX >= 0 ) CALL TBALLOONS(JI)%TBALLOON%DATA_ARRAYS_DEALLOCATE()
       DEALLOCATE( TBALLOONS(JI)%TBALLOON )
     END IF
   END DO
@@ -176,7 +186,7 @@ IF ( ISP == TPDIAFILE%NMASTER_RANK ) THEN
   DO JI = 1, NAIRCRAFTS
     ! Free aircraft data if it was not stored on this process
     IF ( NRANKCUR_AIRCRAFT(JI) /= TPDIAFILE%NMASTER_RANK ) THEN
-      CALL TAIRCRAFTS(JI)%TAIRCRAFT%DATA_ARRAYS_DEALLOCATE()
+      IF ( TAIRCRAFTS(JI)%TAIRCRAFT%NSTORE_MAX >= 0 ) CALL TAIRCRAFTS(JI)%TAIRCRAFT%DATA_ARRAYS_DEALLOCATE()
       DEALLOCATE( TAIRCRAFTS(JI)%TAIRCRAFT )
     END IF
   END DO
@@ -239,10 +249,8 @@ IMI = GET_CURRENT_MODEL_INDEX()
 
 IRR = SIZE( tpflyer%xr, 3 )
 
-IF (TPFLYER%NMODEL==0) RETURN
-IF (ALL(TPFLYER%XX==XUNDEF)) RETURN
-IF (COUNT(TPFLYER%XX/=XUNDEF)<=1) RETURN
 IF ( IMI /= TPFLYER%NMODEL ) RETURN
+IF ( ALL( TPFLYER%XX == XUNDEF ) ) RETURN
 !
 IKU = SIZE(TPFLYER%XRTZ,1) !number of vertical levels
 !
diff --git a/src/MNH/write_balloonn.f90 b/src/MNH/write_balloonn.f90
index 4c0e7d02b4acb61d35441843c96319153e74a333..e519c2b99e0d289941727eb4106293c8abab8ac6 100644
--- a/src/MNH/write_balloonn.f90
+++ b/src/MNH/write_balloonn.f90
@@ -73,12 +73,13 @@ TYPE(TFILEDATA),   INTENT(IN) :: TPFILE ! File characteristics
 !
 INTEGER :: IMI
 INTEGER :: JI
-LOGICAL :: OMONOPROC_SAVE ! Copy of true value of GSMONOPROC
+LOGICAL :: GEMPTYCOMM     ! if TRUE, the communication is empty (no data is exchanged)
+LOGICAL :: GMONOPROC_SAVE ! Copy of true value of GSMONOPROC
 
 IMI = GET_CURRENT_MODEL_INDEX()
 
 ! Save GSMONOPROC value
-OMONOPROC_SAVE = GSMONOPROC
+GMONOPROC_SAVE = GSMONOPROC
 ! Force GSMONOPROC to true to allow IO_Field_write on only 1 process! (not very clean hack)
 GSMONOPROC = .TRUE.
 
@@ -87,30 +88,33 @@ DO JI = 1, NBALLOONS
 
   ! Send data from owner to writer if necessary
   IF ( ISP == NRANKCUR_BALLOON(JI) .AND. NRANKCUR_BALLOON(JI) /= TPFILE%NMASTER_RANK ) THEN
-    CALL TBALLOONS(JI)%TBALLOON%SEND( KTO = TPFILE%NMASTER_RANK, OSEND_SIZE_TO_RECEIVER = .TRUE. )
+    GEMPTYCOMM = ( TBALLOONS(JI)%TBALLOON%NMODEL /= IMI )
+    CALL TBALLOONS(JI)%TBALLOON%SEND( KTO = TPFILE%NMASTER_RANK, OSEND_SIZE_TO_RECEIVER = .TRUE., OEMPTYSEND = GEMPTYCOMM )
   END IF
 
   IF ( ISP == TPFILE%NMASTER_RANK ) THEN
     ! Receive data from owner if not available on the writer process
     IF ( NRANKCUR_BALLOON(JI) /= TPFILE%NMASTER_RANK ) THEN
       ALLOCATE( TBALLOONS(JI)%TBALLOON )
-      CALL TBALLOONS(JI)%TBALLOON%RECV_ALLOCATE( KFROM = NRANKCUR_BALLOON(JI), ORECV_SIZE_FROM_OWNER = .TRUE. )
+      CALL TBALLOONS(JI)%TBALLOON%RECV_ALLOCATE( KFROM = NRANKCUR_BALLOON(JI), ORECV_SIZE_FROM_OWNER = .TRUE., &
+                                                 OEMPTYRECV = GEMPTYCOMM )
     END IF
 
     ! Write data (only if flyer is on the current model)
     ! It will also be written in the ancestry model files
-    IF ( TBALLOONS(JI)%TBALLOON%NMODEL == IMI ) CALL WRITE_BALLOON_POSITION( TPFILE, TBALLOONS(JI)%TBALLOON )
+    ! if GEMPTYCOMM=FALSE => flyer is on the current model (equivalent to TBALLOONS(JI)%TBALLOON%NMODEL==IMI)
+    IF ( .NOT. GEMPTYCOMM ) CALL WRITE_BALLOON_POSITION( TPFILE, TBALLOONS(JI)%TBALLOON )
 
     ! Free ballon data if it was not stored on this process
     IF ( NRANKCUR_BALLOON(JI) /= TPFILE%NMASTER_RANK ) THEN
-      CALL TBALLOONS(JI)%TBALLOON%DATA_ARRAYS_DEALLOCATE()
+      IF ( TBALLOONS(JI)%TBALLOON%NSTORE_MAX >= 0 ) CALL TBALLOONS(JI)%TBALLOON%DATA_ARRAYS_DEALLOCATE()
       DEALLOCATE( TBALLOONS(JI)%TBALLOON )
     END IF
   END IF
 END DO
 
 ! Restore correct value of GSMONOPROC
-GSMONOPROC = OMONOPROC_SAVE
+GSMONOPROC = GMONOPROC_SAVE
 
 END SUBROUTINE WRITE_BALLOON_n
 !-------------------------------------------------------------------------------
@@ -151,7 +155,7 @@ REAL                 :: ZLON          ! longitude of the balloon
 type(tfiledata)      :: tzfile
 TYPE(TFIELDMETADATA) :: TZFIELD
 
-! Do not write balloon position if not yet in fly or crashed
+! Do not write balloon position if not yet in flight or crashed
 IF ( .NOT.TPFLYER%LFLY .OR. TPFLYER%LCRASH ) RETURN
 
 ! Check if current model time is the same as the time corresponding to the balloon position
diff --git a/src/Makefile.MESONH.mk b/src/Makefile.MESONH.mk
index 223dd4c2caca29b0eb051c92026de99e52859072..6c9420cecf939b753d843c54d177c914efe03376 100644
--- a/src/Makefile.MESONH.mk
+++ b/src/Makefile.MESONH.mk
@@ -342,7 +342,7 @@ INC_MPI                = -I$(B)$(DIR_MPI)
 DIR_MASTER            += $(DIR_MPI)
 OBJS_LISTE_MASTER     += mpivide.o
 INC                   += $(INC_MPI)
-mpivide.o  : CPPFLAGS += -DMNH_INT=$(MNH_INT) -DMNH_REAL=$(MNH_REAL) \
+mpivide.o  : CPPFLAGS_C += -DMNH_INT=$(MNH_INT) -DMNH_REAL=$(MNH_REAL) \
                         -I$(DIR_MPI)/include
 VPATH                 += $(DIR_MPI)
 endif