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
CrIS	S-NPP	S-NPP
ATMS	S-NPP	S-NPP
AMSR	GCOM-W1	GCOM-W1
SSMIS	DMSP17, DMSP18	DMSP17, DMSP18
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
SEVIRI CSR	not used	METEOSAT-8, METEOSAT-10
AHI CSR	H-8	H-8
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 ?????

Configuration

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.

OPS

• 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

VAR

• 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

UM

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

Results

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

Resources

• ​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