Version 27 (modified by Jin Lee, 2 years ago) (diff)


Assess possible degradation of TC forecasts by ACCESS-G caused by not assimilating some observation types

Bureau currently does not receive and so its models do not assimilate a large number of observation types that UKMO doesn. This is thought to degrade Bureau's global model forecasts.

There is a view that the observation coverage is sufficient (Kelly et al. 2007).

However Fiorino (2009) showed that changes (in this case IFS physics) may not show up in gross verification statistics but can show up in tropics: e.g. tropical winds, tropical cyclone tracks.

Also the impact of one observation type on its own may not be clear. However the synergistic effect of a number of observation types can be magnified.

Additional observation types

Following two tables show a comparison of observations which are currently used operationally in ACCESS-G3 and those used in UKMO OS42,

In-situ observations

Obstype Usage in ACCESS-G3 Usage in UKMO OS42 Comment
METAR, SYNOP used used
TEMP, PILOT, SONDE used used
AIREPS, AMDARS used used

Satellite observations

Obstype Usage in ACCESS-G3 Usage in UKMO OS42 Comment
ATOVS MetOp-1, MetOp-2, NOAA-15, NOAA-18, NOAA-19 MetOp-1, MetOp-2, NOAA-15, NOAA-18, NOAA-19
AIRS Aqua Aqua
IASI MetOp-1, MetOp-2 MetOp-1, MetOp-2
MWTS-1, MWHS-1 not used FY-3B
MWTS-2, MWHS-2 not used FY-3C
Satwind METEOSAT-11, H-8, GOES-15, GOES-16, Aqua METEOSAT-8, METEOSAT-9, METEOSAT-10, H-8, GOES-13, GOES-15, MetOp-1, MetOp-2, NOAA-15, NOAA-18, NOAA-19, S-NPP, Terra, Aqua
Scatwind MetOp-1, MetOp-2, CORIOLIS MetOp-1, MetOp-2, CORIOLIS
GPSRO MetOp-1, MetOp-2, TerraSAR-X, FY-3C MetOp-1, MetOp-2, TerraSAR-X, TanDEM-X, FY-3C, COSMIC-6
Ground GPS used used
MT/SAPHIR not used MT
GOES CSR not used GOES-13, GOES-15

Experimental set-up

For each TC case we will use a control and a test. The control will have only the observation types used operationally whereas the test will assimilate additional observation types that we currently do not assimilation but are used by UKMO.

We will mainly assess the difference in track forecasts between control and test. However a question arises as to how robust the difference in track forecasts is. It's possible that the difference arose because of the inherent chaotic nature of the data assimilation system and the forecast model. To allow us to approximately the effect of this randomness we will also create an initial condition by adding global, random perturbations to the control.

Trial periods

The following is a list of TC's used in this experiment and the trial periods,

TC First cycle of trial last cycle of trial lon/lat when first declared Category Comments
KAI-TAK 2017120400 2017122318
TEMBIN 2017121100 2017122518 straight track
HILDA 2017121700 2017122818
BOLAVEN 2017122400 2018010318
IRVING 2017122700 2018010618 Cat 1
JOYCE 2018010100 2018011318 Cat 1
CEBILE 2018011800 2018020818
FEHI 2018011900 2018013018
GITA 2018013100 2018022218 Cat 4
SANBA 2018020100 2018021618
KELVIN 2018020700 2018021918

Starting cycletimes are chosen 10 days prior to the dates when TC's were declared ("Start date"). ???? might need to go a little further to allow analysis of pre-storm environment ????



  • Obstore files were retrieved from the update runs of UKMO operational OS,
    • all obstypes are tar'ed in a single tarball
    • 1.1 GB of data per cycle
    • from 20171204 00Z till 20180222 18Z (inclusive)
  • Ops_ExtractAndProcess reads observations from obstore files
    • There were some problems with Ops_ExtractAndProcess reading obstore files


  • non-hybrid 4DVar . alternatively hybrid uncouple 4DVar with error modes from an archive of a single run
  • PFM resolutions are N144 and N320


  • Resolution: N640L70 (????check physics settings are correct for N512????)
  • PC2 cloud scheme
  • ????


  • Jim Fraser's List of TCs in West Pacific & Eastern Indian Ocean from G3 trial periods
    • Note "First Lat" and "First Lon" columns show lat/lon when TC's were first named; they are the TC locations on the dates under the column, "Start date"
  • JTWC bogus central pressure observations are available from Dec, 2017
    • the central pressure data are converted to text files and then these text files are read in by OPS

Things to do

  • For Ops_ExtractAndProcess tasks work out how to read UKMO obstore files
    • Do we use exclusively obstores from UKMO - both for control and test?
  • Need initial varstats files
  • Need to turn on all obstypes UKMO uses
  • Ask Jim what fields are needed for TC track verification

Attachments (1)