Version 46 (modified by Jin Lee, 4 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

Starting from OS40 UKMO started to assimilate GMI observations. Since the trial started from Dec 2017 GMI was excluded.

Obstype Usage in ACCESS-G3 Usage in UKMO OS39 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
GMI not used GPM UKMO OS40 started assimilating GMI from 20180213T06
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 From some time in Dec 2017 until 20180101T00 no data in obstore; from 20180101T06 obstores contain data
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 2017120406 2017122312
TEMBIN 2017121106 2017122512 straight track
HILDA 2017121706 2017122812
BOLAVEN 2017122406 2018010312
IRVING 2017122706 2018010612 Cat 1
JOYCE 2018010106 2018011312 Cat 1
CEBILE 2018011806 2018020812
FEHI 2018011906 2018013012
GITA 2018013106 2018022212 Cat 4
SANBA 2018020106 2018021612
KELVIN 2018020706 2018021912
HOLA 2018022406 2018031112 Cat 4 named on 20180306 and at its naming Cat 1
LINDA 2018030306 2018032512
MARCUS 2018030606 2018032512
NORA 2018030906 2018032712
IRIS 2018031406 2018040512
JELAWAT 2018031406 2018040112
JOSIE 2018032106 2018040212
KENI 2018032906 2018041112
FLAMBOYAN 2018041706 2018050112
EWINIAR 2018052306 2018060912

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 ?????


As one of the verification measures to be used in this experiment is the ability of the trials to predict TC tracks it is important to resolve the inner core structure of a TC; even better, to have a few gridpoints within the eye of a storm (Q. In order to model the interaction between a TC and its environment in related to TC movement do we need to resolve the eye?). To achieve this I would like to run UM at N640 resolution (see here for some issues encountered when changing the resolution of the ported PS41 suite from N320 to N640). However, running at this resolution for a trial lasting for more than 3 months is unaffordable at NCI. So as a compromise I decided to run at N320 UM resolution.


  • Obstore files were retrieved from the update runs of UKMO operational OS,
    • all obstypes are tar'ed in a single tarball
    • raijin4:/g/data/dp9/as2291/obstores
    • 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 N108 and N216
  • used a new VAR build to get around a bug that incorrectly opens RTTOV coefficients - details here


  • Resolution: N320L70 (0.5625 deg lon and 0.375 deg lat; 63 km x 42 km at equator)
  • PC2 cloud scheme
  • ????


Overall verification

Verificaition of TC tracks

  • TC tracker needs following fields,
    • essential: MSLP; 10-m winds; 850, 700, 500 hPa u/v winds and geopotential heights (available in the archived files, "*_glm_t???.ff")
    • additional: 800, 500, 300 hPa heights
    • fields need to be in Grib1 format
    • TC bogus files are needed to be used as first guess for the tracker
    • Jim to do an initial test of TC tracker once analysis and forecast files are available from a single basetime
      • test whether all STASH fields are output for TC tracker by cold-starting the suite from 20180306T06; long forecast from 20180306T12 should produce forecast files which can be used by the tracker


  • 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

Useful information

  • N640L70: 0.3515625 deg lon and 0.234375 deg lat; 39 km x 26 km at equator

Things to do

  • What do gl?_ops_process_analysis_* tasks do - generate feedback ODB1? Should these tasks be removed from the suite?
  • TCBOGUS data seem to be available in UKMO obstores. Will they be used by VAR?
  • What to do about locally received data?
  • files being copied are,
    • obstore files
    • glu_t+3 from 20180305T18 - to produce forecasts to test TC tracker

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